I was looking at the stock intake manifold. It only has a 52mm opening, so why would you go larger than that opening in a TB? Your air flow would just hit a wall when it meets the step up from the larger TB to the actual size of the hole on the intake.

Are the larger TB's tapered from the large opening to the 52mm of the stock manifold? If so I could see some benefit of that because the air would speed up as it when through the TB. I am just curious what you guys do about that? What would be the point of putting a 60mm straight through TB on your manifold if there is a large step from 60mm to 52mm

Just curious
Brain

You have to bore the manifold opening. I have a billet 60mm TB and I used a die grinder to open it up. The gains are noticable on a modded engine. Stock engines shouldn't go any higher than 55mm.

Here's a pic... it's straight through as you can see the other side of the manifold through the TB.

How come stock engines shouldnt go pass 55mm?

1999 Mitsubishi Eclipse GS 10th Anniversary OZ Edition
Check Out My Site For Pix
http://mywebpages.comcast.net/EclipseRaceR/MyEclipse/VIS%20CF%20Hood/

Actually stock opening is more like 54mm, it almost exactly matches a bored through 55mm TB.

You should only take in as much fuel and air as you can get rid of, teh stock exhaust isn't goping to do a good job of expelling that much air. Remember all parts of modding your car have to work together, outflowing your motor on the intake side without a good exhaust, isn't going to help you any.



15.9 @ 86.7mph
97 Eclipse RS

Injen CAI, 55mm TB, P&P Intake, Crower Stage 2 Cams, Hooker Header, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC

I cant wait to get a 60mm throttle body with that Indy manifold...*drools*mmmmmmmmmm:thumbsup

if you're referring to the new modern performance tb's, no they aren't tapered in. 60mm straight through. I disagree with the 55mm limit for our cars. 60 is fine. it's like with all mods in that you need to do other things in order to reap the full benefits of that mod. you should either bore out your stocker intake manifold or even better get the INDY!

It's all about airflow velocity. If the engine can only take in enough air to fill the 54MM TB, then you will not only see no gains from, but you will see a loss from going larger. You will, however, have better throttle response. More air gets in at part throttle then it did before, which decreases drivability, and decreases peak torque. Unless you are running a lot of air through the motor, such as with forced induction, what you will be feeling is a jump when you start to open the trottle, since you are letting a lot more air in at part throttle.
But do what you wish, it's not my car.
-=B-=

yea, the1bill is correct on all accounts. too large a diameter and it will be more problematic than helpful. 55-60 is the limit for a 2 L IMO

Howell did airflow tests and 55mm is the optimal size for the non-turbo 420a. Larger diameters will negatively effect performance unless you're force-feeding it compressed air! ;)

Well, I've gone 15.41 with the stock throttle body, so it can't be that bad :)

This may be a dumb question, but here goes. If you aren't planning on going turbo, are you suggesting to not go 60mm? I was all set on buying a 60mm, but now I'm not sure. I will bee getting a CAI and exhaust very soon, but I don't think I'll end up ever going turbo.


1999 Eclipse GS
OZ Edition
Bone Stock

...but not for long..

hehe if you turbo go as big as you can :P Man I really need to get one :( I've still got the dinky stock on. NE1 know any local places in the bay area that bored TBs?

>Howell did airflow tests and 55mm is the optimal size for the
>non-turbo 420a. Larger diameters will negatively effect
>performance unless you're force-feeding it compressed air! ;)

If i remember those cfm numbers correctly, 55mm flowed slightly less cfm then optimum, but 56mm flowed slightly more then optimum.

I dunno, i personally went with ARD's 57mm tb knowing i'll eventually go turbo.

whats the INDY!? I want it! }(

if you have a free flowing exhaust a 60 should be fine. it will help restore some of your low end power, because of valve overlap.

The oversized (that is really what it is) throttle body will do nothing for low end torque, or top end power, except create a loss. It is, in fact, more likely to create a low RPM power loss, because at the low RPMs, the airflow velocity is not high. At low RPMs, it simply is not consuming much air, so opening it up to even more air is not only pointless, it is detrimental.

Oh yeah, here it is, right from the horse's mouth (I am not calling Gary Howell a horse, but... ummm... yeah.)

http://www.howellautomotive.com/phpbb2/viewtopic.php?t=167

Many thanks to Gary "I'm not a horse" Howell!
-=B-=

Just a thought I had... but those are the maximum amounts of air you can flow through those sizes of TB right? But do we actually flow that much air at any given time? Meaning does a CAI or the stock air box actually flow that much air? I doubt that it does. Especially the stock air box. If that was true then a larger TB could be used to allow more of the AVAILABLE air into your motor.

you are greatly oversimplifying the issue though. at a given constant rpm at any partial throttle level, there is no difference between a small and large tb. the engine is seeing the same air flow. in terms of WOT, it does not make sense to view the larger diameter tb and the resulting slower flow (just through the length of the tb, mind you) as affecting hp/torque. what matters is the air flow throught the entire system, most importantly at the intake runners going directly into the cylinders. the 3 or so inches which air goes through the tb will not affect the entire systems air flow to the point of a loss of low end torque. however the larger diameter tb combined with a matched intake manifold will allow for significantly increased flow at the top end. there are some good articles out there on this - lemme see if I can find one.

my 2 cents homie

Uhhh oh no, I've gone cross-eyed.

LOL.. well I believe you are diggin too deep into the issue. Not to mention you sorta ignored what I brought up :P All I was saying is that just because the TB is larger, that might not mean you are exceeding the amount of air that your motor needs or wants because an infinite amount of air is not always available.

In case you missed it.. I was aggreeing with you. I think a larger TB can be used without a loss in performance. :thumbsup

so our cars will be slower with this 60mm tb. I will be boring out my manifold to match while also p&p everything. I don't see how this couldn't help me at all. I thought these were good mods to do.

Maybe someone that has ordered the modern 60 and already owns a Howell 55 or ARD 57 could do give us some dyno results. I would if I could but since I have stock TB and no Dyno I cant help out. sorry

>>>>so our cars will be slower with this 60mm tb

arrrg! no, the top end is improved, especially with a matched manifold. fastergs is right (and I wasn't trying to dive into it that much in regards to your question, but someone elses followup), that there is a limit where getting too big of a diameter won't help things. the 60mm tb is a good mod IMHO and when we finally have a comparison of an INDY/OEMtb vs INDY/MPtb I know it will show on the dyno. there are people on this board with a bored tb and matched intake manifold that can tell you it's a definate improvement.

but I understand the need for some dyno data to make a point. I like to have black'n'white figs to look at as well.

in any case the MPtb's have shipped out so we will soon hear from a bunch of other 2gnters on their feelings about it. I personally think it's awesome - but realize it's only one piece of the puzzle that you need to put together.

Well, then the issue becomes velocity. If the throttle body is oversized, then the throttle plate will be less open to maintain a certain RPM/speed then it would be for a smaller throttle body. Here's a simple diagram, took me 30 seconds to make:



Which of the two, assuming same CFM flow, will flow with higher velocity? The one with the big honkin' throttle plate occulting the airflow path? Or the one where the plate is perpendicular, and nearly invisible? Furthermore, if the smaller throttle body can flow as much air as the rest of the system can accept, why go larger?
-=B-=

I have a few questions.

If stock throttlebody and the 60mm throttle body are two different sizes wouldnt the CFM flow be different ?

Also, if you put a larger throttlebody on (would'nt you also adjust your throttle cable so that the throttle plate would open as it would with the stock throttlebody)?

Are we saying that the larger throttlebody ( as compared to stock) at the same rpms as stock will flow different because flow is blocked by the throttle plate? ---- run on questions anyone;-)

I'm just trying to understand this whole thing.

I believe you guys are thinking to much into it...

If your manifold is ported to *match* the larger TB (which has the same opening pattern as a small one.....horizontal at WOT) then you will get better airflow, your engine won't struggle nearly as much as a small orifice, and it will get plenty of oxygen.

While if your manifold is not ported, when the 60mm TB is opened air will slam into the manifold walls, disrupt the flow, cause turbulant air, and not flow evenly. While if you matched the opening w/ a smaller one, you would be getting air a greater velocity, but at the expense of the engine having to use more power to 'suck' it in.

In other words, you will get increased performance on the 60mm if your manifold matches (and probably more than the stock TB if your not ported, do to less restriction), but if your not porting it get the 56mm (I believe this is the max size for the stock intake mannifold).

>in terms of WOT, it does not make sense to view the larger diameter >tb and the resulting slower flow (just through the length of the tb, >mind you) as affecting hp/torque.

WHAT?!??!? :o THAT IS EXACTLY WHAT HAPPENS!!! The slower flow WILL affect the torque of the engine!!! The larger throttle body, at WOT and low RPMs, will cost you low end torque. A wide open 60mm throttlw body can flow ALOT of air! Our engines at 3000 rpms ad WOT don't need that much air. The air will flow to this huge TB then slow down because it is too big (as Bill has explained).

I'll say it again, this is what matters for power: VELOCITY, VELOCITY, VELOCITY, VELOCITY, VELOCITY.

If you could get our engines to run on buckshot and chicken shit, then the faster you can get that buckshot and chicken shit through the engine, the more power you will make.

>the 3 or so inches which air goes through the tb will not affect the >entire systems air flow to the point of a loss of low end torque.

The large TB is PART of that whole system, so the TB will affect what happens to the whole system. Your argument does not amke any logical sense. At low RPMs the huge TB won't affect the system, but at high RPMs it will? What is so different about low versus high RPMs that the TB will affect one but not the other? There isn't any.

>I have a few questions.
>
> If stock throttlebody and the 60mm throttle body are two
>different sizes wouldnt the CFM flow be different ?

The CFM flow at WOT we are talking about is the maximum flow the TB can handle. A bigger TB will flow more maximum CMF than a small TB.

>Also, if you put a larger throttlebody on (would'nt you also
>adjust your throttle cable so that the throttle plate would
>open as it would with the stock throttlebody)?

If you had your throttle plate open even a tiny bit, your idle would be 3000 rpms. The stock throttle plate is completly closed when your foot is off the accelerator. The car uses the small idle motor/valve/whatever it is called to let enough air in for the car to idle.

>Are we saying that the larger throttlebody ( as compared to
>stock) at the same rpms as stock will flow different because
>flow is blocked by the throttle plate? ---- run on questions
>anyone;-)

At the same part throttle (25%, 50%, whatever) a large TB will flow more than a small TB, giving increased throttle response. That is the primary benefit froma bored TB, the better throttle response. That is why the TB mod "feels" so good to people, you increase the throttle response so the car takes off a bit faster, it feels faster, but the tp end HP improvement is minimal, and for the price paid I don't think it is worth it.

As it pertains to throttle response, sometimes more throttle response is a good thing, and sometimes it is not.

>At the same part throttle (25%, 50%, whatever) a large TB will
>flow more than a small TB, giving increased throttle response.
>That is the primary benefit froma bored TB, the better
>throttle response. That is why the TB mod "feels" so good to
>people, you increase the throttle response so the car takes
>off a bit faster, it feels faster, but the tp end HP
>improvement is minimal, and for the price paid I don't think
>it is worth it.


Okay, so aren't we modding our cars to make them faster? So if you loose some HP but you're leaving the line faster and accelerating quicker then aren't you accomplishing your primary goal?

I think if you're tuning to get the best time on the track this consideration is outstanding, but for guys like me who don't go to the track but just want a more fun car this would be perfect.

Now if you put it on and the car felt slower than before....I would never buy one just cuz it's big....but if people have had a 57mm and go to a 60mm and it put a huge smile on their face, then I'm all for buying one! :thumbsup

Making the engine struggle to suck in through a small opening (makes high velocity) doesn't increase hosepower.

Ok I am starting to understand what The1Bill is trying to say about with the larger throttle having the bulky trottle plated blocking airflow where the smaller throttle is fully open. However, what if you have a Indy manifold that can accept all the airflow that the 60mm throttle can give. Not only will you have a much quicker throttle response but also a huge amount of airflow to the engine. I'm still not understanding how you are going to have a low RPM power loss if the same amout of air is getting to the engine.

I understand what Bill and Todd are saying. What I want to know, Is when does the 60 become the better size TB. I mean If you had mods such as an Indy Manifold and some more aggressive cams then would the 60 become more effective?

Yes, also if you increased displacement in your engine.

Forced induction would be another scenario where your volumetric effeciency would go WAY over 100%.
The motor doesn't need to work harder to make the air go through the smaller throttle body, and the smaller throttle body will increase airspeed velocity. If the throttle body were 20MM or something stupidly small, then the motor would be working really hard to pull it's required air through it. Even if you take your 60MM TB, and port your Indy manifold, run wild cams, and port the head until the walls are as thick as aluminum foil, you still won't be much over 100% volumetric effeciency. You might hit 110-115 percent volumetric effeciency, which means that your motor is consuming 2.0 * 1.15 = 2.3L of air. This is more then compensated for in Gary's equation, though. Now, say that we are using a turbo, and run 14.7 PSI (which is one atmosphere of air). Given perfect effeciency of the motor, you have effectively doubled it's VE, and it should act like a 4.0L. that's why turbochargers work. They cram 4.0L of air into a 2.0L. In that case, the 60MM TB would be of great benefit, as you are not feeding a 2.0 any more, but you are effectively feeding a 4.0...
I have had a lot of discussions with a bunch of engineers about this, and that is where this all comes from. At first I didn't believe them, but the numbers hath spoken.

By the way, I just thought of another condition that would require more CFM from the intake stream: increased redline. We can't effectively do that to any extent that really matters, though, at least without a standalone, so it is vastly irrelevant.

By the way, the CFM numbers that Gary posted are peak numbers, which means that at anything less then full throttle at redline, the motor will require signifigantly less air.

-=B-=

I disagree with you vx100. My point was that a reduced airflow velocity at the tb does NOT equate into significant reduced speed at the intake runners - which is what is most important. It's simple fluid dynamics. If you have a wide section of tubing, air flow velocity is diminished. But if that air then passes through tubing with a much smaller diameter - air flow velocity increases. It's Bernoulli's principle - That's the whole reason why carburators work, airplane wings lift, etc...!!!

If you made the whole intake manifold including the runners much greater in diameter as well as the tb, you WOULD have decreased air velocity and substantial loss of low end torque. As it is however, you only have perhaps 3" in length of greater diameter followed by the entire intake manifold and runners through which velocity picks up again.

Do you see my point now?

This is all well and good, but if 1 60mm throttle body is too much for our cars then why are people making individual throttle body set-ups for our cars that contain 4 32mm throttle bodies?

That doesn't make any sense to me. I'm not arguing, just confused.

bwhaha, Aaron I should clarify I'm not arguing either. This is just an open discussion :D

oops I did not mean to say Bernoullis principle (which is when air flow speeds up the pressure drops). excuse the misstatement you physicists/mech eng.'s out there. it wouldn't let me edit it above.

what I meant to say was that flow increases again as the air progresses through a smaller diameter pipe, simply put.

Well, the quad TB setup is a perfect design for a motor that has an astronomical redline, which would require a LOT of air. A motor with a 6000 RPM redline will use half of the air that a motor with a 12000 RPM redline will (well, at redline, anyways), given that nothing else changes (like the VE, etc...). Mind you, in order for a motor to stay effecient at 12000 RPM, those would need to be some NASTY camshafts, and a heavily ported head. At that point, an open header and quad throttle bodies would be VERY helpful.
Me, I'll stick to a this turbo thingie.
-=B-=

Someone needs to dyno and prove it to all of you. Many of you have valid points that sound good for either size but unless you are turbo, none of these cars will ever see 100% VE, not even close. It is a proven fact that NA cars do in fact drop in HP and TQ when the TB gets too big, it has been done for years in Mustangs and it helps nothing without a blower. I personaly have went 12 second 1/4 miles in my fox body with a stock 60mm TB, now you explain to me how a 2 liter engine needs a 60 mm TB when it is not sucking in anywhere near that much air and making 1/3 the HP at best as a 5 liter all steel 306 with a 60MM TB that was turning 7k in 4th at the traps? It doesn't. The people who tell you they feel a difference, well, its all in their heads. You cannot even come close to a seat of the pants Dyno without at a minumum 20 HP difference. I have changed cams before and really not noticed a diff in full throttle until I went to the track and got 4 mph and .3 off my 60. I am just trying to save some people some money here and keep them from buying stuff that is not going to help out until you force in air, and not N2O either, that is artificial induction, meaning there is much less going in than what is coming out so the TB would be of no help there either, N20 is atmosphere in a bottle. If you are going Turbo, have at it, otherwise, buy better things like Cams, pulleys, exhaust, and so on.

I agree. I think that this topic is dead until we can get back to back dyno runs on the same car. I think that would be the only way to show, one way or the other, what the effect of the 60MM TB would be on a NA motor. I suggest 3 scenarios to do, back to back to back.

1) Stock TB, with stock intake mani upper portion

2) 60MM TB, with stock intake mani upper portion

3) 60MM TB, with port matched TB end of intake manifold


Bet you a beer that the power will go, from most powerful to least, 1, 3, 2. If I am wrong, then there will be no real perceptible difference.

-=B-=

Thats a tall order Bill. I do have all of that stuff - stock TB, Jeep TB 60mm all the way through, and stock non-TB-port-matched manifold. Basically I have everything except the dyno.

But I do have something similar to a GTech. My Field Hyper-R SFC measures 0-100m, 0-200m, 0-400m trap speed and times(it's Japaneese so everything is metric). The only problem with it is that the speed that it senses is doubled(for some wierd reason) so measuring 400m(~1/4 mile) runs on the unit happens over a REAL 200m(~1/8 mile). Otherwise, it's very consistant at starting the clock when the car starts to roll.

I'm not sure if my car qualifies well for the test though cause I also have ram air, cams, ported exh mani, test pipe, and GST exhaust. The thing that I think may disqualify me are my cams. My VE is alot higher than stock and the best I can figure is the cams make it suck about 50CFM more at redline over stock. From how this conversation is going - it shouldn't disqualify me, because I'm still N/A.

So if we can agree that my car qualifies AND unless someone else has all the other shit and can actually do it on a dyno - I could do 10 timed ~1/8 mile runs with setup #1 and #2 back to back and average the results. Would that satify the beer bet? Porting the manifold to run test #3 would take too much time(next day kind of thing) to make it a fair back to back to back scenario, but from what you're saying I should be faster with the stock TB.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

ok i don't know as much about engines and tuning an stuff as you guys, but i do know my physics pretty well. rule one: volumetric flow through a system is constant. the volume of air flowing through the inlet is equal to the air flowing through the outlet is equal to the volume of air flowing through any given point of the system. it's mechanical equivalent to current in an electrical system. current in = current out.

think about a garden hose with water flowing through it. if you couple it to a fire hose and then drinking straw (all in series) the amount of water you put in better equal the amount of water that comes out. otherwise, wtf happen to the rest of the water or where did the extra water come from? the amount of water flowing through any given point is the same. yes it will move more slowly through the fire hose and faster through the straw, but the volume of water flowing is still the same. the amount of water that comes out at the end of the straw will be the same as the amount that was put in the garden hose at the other end.

the same applies to the air intake system. the air may speed up when it reach a small stock TB. however, the volume of air flowing there is still the same as anywhere else. i don't think all the discussion about velocity is really valid. whatever happens at the TB/manifold junction is irrelevant. the final velocity of the air entering the engine occurs where the air enters the engine. it is different from where the air enters the manifold. this is why those 'vortex' POS deals on ebay that claim to increase air velocity in your intake do not work. they are being trutful - the air does speed up at that point. however imediately after it slows back down to exactly what it was before the 'vortex'.

that being said, you're just looking to increase air flow. not velocity. that's what having a CAI, or porting, or an oversized TB does - they increased the volume of air that can taken up by reducing the overall resistance of the system. decreased resistance = increased flow. just as decreased resistance = increased current in an electrical system. maybe i'm way off on this but looking at it from a physics aspect, this seems to make the most sense.

-marc

='95 RS 5spd Red=
CAI
A'pexi N1
Hanabi 8000k HID
SPAL Deluxe Power Windows
Nakayama GT5 17's
GSX Calipers
AEM Rotors

255 is fricken short

>
>I'm not sure if my car qualifies well for the test though
>cause I also have ram air, cams, ported exh mani, test pipe,
>and GST exhaust. The thing that I think may disqualify me are
>my cams. My VE is alot higher than stock and the best I can
>figure is the cams make it suck about 50CFM more at redline
>over stock. From how this conversation is going - it
>shouldn't disqualify me, because I'm still N/A.
>


While true that it is still na, you have a large advantage over a stock car due to like you said, cams. That is effectively the brain of your engine and you may unlike a stock car actually benefit from the bigger tb. I am not sure because I am by far not an expert on the transversly mounted 4 banger but I grew up tearing apart and rebuilding hot rods. I know when you go from a restrictive stock cam on an average mild 300+ horse V8 to a decent lift and duration cam, your power is amazingly improved just because the car no longer falls on its face at about 5500 rpms due to the emmisions freindly cam, it will pull hard as hell toward the 7k mark or whatever depending on the specs. Thing is, when you are revving that high with that much valve lift, you are sucking a lot more air therefore the bigger mani and tb will help out with the new bottle neck you created by the cam. On a more modded car such as yours, the tb will probably have a much more favorable effect than a bone stock bolt on car.

That is all true... mostly. The bottleneck, however, is not the amount of air being pushed through, it is how fast it is being pushed through.
Torque is determined by velocity. Why?

Because you can use the energy that the engine already expended to shove the last pulse of exhaust out to do more work.

If you get that pulse shooting out at a high speed, the next pulse will be pulled in really quickly. By timing the pulses with runner length in both the intake manifold and the header, you can make it so that the very next pulse gets plopped into the motor at positive pressure, since it is surrounded by vacuum. Basically, pistons goes back up with the exhaust valve open, and shoves the exhaust pulse out. At the same time, the intake valve is opening (overlap). There is a low pressure moving area that follows the exhaust pulse, which is moving on it's own momentum. This pulse moves, and leaves a vacuum in it's wake. Nature abhors a vacuum, so the intake pulse is formed. The fresh air rushes in to take the place of the vacuum. If all is timed right, you get an artificially high pressure pulse when the intake valve closes, which is why we can get over 100% VE without a turbocharger. The faster the exhaust pulse moves out, the faster the intake pulse can move in. The faster the intake pulse moves in, the more force (momentum) it has, and the higher the VE that can be obtained.

Now, back to the throttle body.

The whole motor works as one system. Meaning, that if there are any places where the air (intake or exhaust) slows down, the motor must expend a little bit more energy to speed it back up. Using a throttle body that is matched for the air requirements of a motor allows the air to be accelerated into the intake manifold from the intake tubing. The manifold can then accelerate the air towards the head. Momentum builds <suspenseful music> and the air can then positively charge the cylinder. Now, take the stock throttle body and replace it with a 60MM throttle body. The engine pushes out an exhaust pulse and pulls in a new pulse. The engine expends the energy to pull air from the plenum to the runner. The engine expends the energy to pull air from the throttle body into the plenum. But wait, the air at the throttle body is full of stagnant air. A lot of noise and activity culminating into a... whimper. With the stock throttle body, stagnant air (for all intents and purposes) hits the filter, which is exposed to vacuum. This stagnant air is pulled in, from the completely unrestricted (atmosphere) to a slightly restricted tube. This slightly restricted tube now moves into a slightly more restricted tube with a butterfly in the middle (yup, the throttle body), and guess what, speeds up! This faster moving air moves into the plenum, and is pulled into a runner, and it, yup, speeds up again. Into the head, yup, faster still! By this point, it has accelerated from stagnant to the speed of sound. By using the whole intake stream to gain more time for it to speed up, the acceleration has been more gradual. Gradual acceleration of any mass requires less work then rapid acceleration of the same mass. Case in point: A Civic DX with a motor that can do some work can accelerate to 60 in, say, 10 seconds. A Civic EX, which is capable of doing more work (has more power) can reach 60 in 8 seconds. Therefore, to get an object with all of the characteristics of a Civic to 60 MPH using the least energy, you get there slower. Both Civics were rockin' it out full tilt (yawn), and it took a lot more power to get the EX to the same velocity more quickly. Well, in a roundabout way, the same applies to the air going into your motor. You want it to take the least amount of energy to reach the velocity that it will attain, which means doing less work, and slower acceleration of the air.

That's why I recommend a longer runway, so to speak, with the stream necking down to the combustion chamber as gradually as possible.

-=B-=

Couple of things...

That was a really long post. I apologize, I have been awake for almost 60 hours now, and am feeling the signs of fatigue, and I had a hard time explaining what I was thinking. If anything is unclear, go ahead and ask, I will respond after a few hours of being comatose.

Secondly, MetalJim, your car has more of an air requirement. You said yourself that you have a higher VE then most other cars. I would be willing to bet, though, that you aren't anywhere near 110%, which is what Gary's numbers account for, so I think that a beer would be safe in my grubby little paws if you were to do this.

My only concern, your performance meter is based off of the speed signal, right? I fear that a G-sensor based system might be fooled by the same thing that could fool a driver, and that would be throttle response. By allowing the large rush of air in earlier, the boot in the pants feel that the "ass dyno" counts on might trick a G-tech. It is, after all, a really sophisticated ass dyno, and it only quantifies the effect that the driver feels on the seat of the pants. It also breaks it into some neat numbers, like velocity, acceleration, and now power and torque. A speed signal, however, shouldn't be fooled in the same way, unless traction is broken. If you have any way to test with your performance meter at a velocity that doesn't risk wheelspin, I think that your findings could be valid. I will hold on to the beer until I see a more stock car do better with the 60MM, though. ;)

And lastly, I don't think that the throttle body is the biggest restriction in the intake stream, I think that it would be the cams. That is why I would wait on a stock car before giving Jim his beer, since he has eliminated the biggest bottleneck, in my opinion. After the cams would be the intake manifold, and then the head. And if you are flowing enough to find the next bottleneck after cams, ported/extrude honed/Indy manifold, and P+P well worked head, then my friends, I am sure that a larger throttle body would be beneficial. And the cams would only be of enormous benefit with an increased revlimit.

But it is time to sleep before I go off on another tangent...
hehe...
-=B-=

Ah, no - I'm nowhere near 110% VE. Closer than stock - but really nowhere near it. The closest I come(I thik) is 91% Here's what I think my VE/CFM curve looks like with the Bullfrogs.
rpm ve engine airflow
1000 83 29.30
2000 83 58.60
3000 83 87.90
4000 86 121.44
5000 91 160.62
6000 91 192.74
7000 88 217.45
7200 88 223.67

...as opposed to what I think stock VE/CFM curve looks like with the stock cams.
rpm ve engine airflow
1000 70 24.71
2000 70 49.42
3000 75 79.43
4000 80 112.96
5000 80 141.20
6000 75 158.85
7000 70 172.97
7200 68 172.83

Oh, and about the SFC - I guess I didn't consider that the Gtech actually has a g-sensor. The SFC does not have a g-sensor. It bases the distance on time and speed - no g-sensing. So, you're right, the only way a run isn't right is when I loose traction. I'll disqualify any runs that I loose traction on.

I've got some stuff to take care of, but hopefully I'll be able to make these runs tonight.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

What if you are trying to use a 57mm tb with a port-matched intake manifold on a 420a with a mild port-matched head with cam gears (stock cams still) and a S16G w/TD06 turbine wheeel and a 20G compressor wheel stuffed in it to a 7800 redline? :P

Where have I seen this setup before? ;-)

Oh, I am happy to see this topic come out as I have always thought people were going a bit overkill on the tb. I only recently added a new tb to mine so I could take advantage of the new setup listed above.

You meant to say the "Venturi Effect" :thumbsup
1999 Eclipse GS
OZ Edition
Bone Stock

...but not for long

Anyone ever notice heating/cooling ductwork in your house or in big buildings(home depot, ect). Take a look at where the duct starts at the heater. Its damn big and large in diameter. Then take a look at how big the ducts are at the register openings. The ducts will go down in diameter the farther away from the fan source. Going from a large pipe, to a small pipe, increases air flow velocity, which in my comparison, will keep the air moving fast at the register, instead of slowly if the duct work was the same big size at the register opening. I fully agree with Bill and others, a larger TB isnt going to help for stock NA apps, it basically just changes how much air enters the engine with the gas pedal. Instead of pushing the gas half way down to reach lets say 35 mph in 3 seconds, put the pedal down half way on the 60 mm, you will accelerate faster in lets say 2 seconds to 35 mph. The larger TB just flows more air per given throttle plate opening over the stock TB. I really want to see what the 60 mm can do with a boosted setup...dyno wise anyway.

a larger TB isnt going to
>help for stock NA apps, it basically just changes how much air
>enters the engine with the gas pedal. Instead of pushing the
>gas half way down to reach lets say 35 mph in 3 seconds, put
>the pedal down half way on the 60 mm, you will accelerate
>faster in lets say 2 seconds to 35 mph.

Isn't that the idea? Sounds like you just contradicted yourself. Maybe I'm misunderstanding though.

Right, but the overall power hasnt really changed at all. It feels faster because you donthave to use as much gas pedal to get going. Make sense? The larter TB just lets in more air per given throttle plate opening, over the stock TB. The engine will consume the same amount of air, just now it will consume the same amount of air with less thorottle plate opening. Personally, our cars are hard enough to lauch as it is (MTX anyway),and having a super touchy throttle, esp on turboed cars, will make it even harder. I'd really like to see some dyno runs to get the true real world outcome, anything else is just a hypothisis(relating to the physics of it anyway)

Correct me if Im wrong. A larger throttle body has somewhat the same effect as a venom 400. It doesnt make you any faster at WOT. Just better throttle response and no extra horsepower at WOT. Maybe?

Due to the amount of information, theory, and ideas in this thread, I have moved it to the advanced tuning section.

>I disagree with you vx100. My point was that a reduced
>airflow velocity at the tb does NOT equate into significant
>reduced speed at the intake runners - which is what is most
>important. It's simple fluid dynamics. If you have a wide
>section of tubing, air flow velocity is diminished. But if
>that air then passes through tubing with a much smaller
>diameter - air flow velocity increases. It's Bernoulli's
>principle - That's the whole reason why carburators work,
>airplane wings lift, etc...!!!
>
>If you made the whole intake manifold including the runners
>much greater in diameter as well as the tb, you WOULD have
>decreased air velocity and substantial loss of low end torque.
> As it is however, you only have perhaps 3" in length of
>greater diameter followed by the entire intake manifold and
>runners through which velocity picks up again.
>
>Do you see my point now?

I do see your point but you are mistaken :) You are drawing the wrong conclusion from fluid dynamics. You are looking at each piece of the puzzle (the different parts of the intake path) independently. You can't do that with an engine. Eveything has to work together. You can't say "The intake runners are the right size, so a big throttle body doesn't matter."

I'll use the exhaust as an initial example (since it is an easy example to understand, it has been proven), then I'll move to intake. If you have a 3 inch cat back on your car, but keep the exhaust manifold stock, it will reduce exhaust gas velocity and cost you power. Ask anyone with a lightly modded NT with a 3 inch exhaust, their cars have no power.

The same thing applies to the intake. If you have too large of an intake pipe, or too large of a thottle body, or too large of an intake manifold plenum, then it won't matter if the intake manifold runners are the right length or diameter. The engine still draws air through those oversized openings (it has to draw air through them before the intake runners), and while moving through those huge openings (whether it is the intake pipe, the throttle body, or the intake manifold plenum) it WILL slow down, and you WILL loose power.

The point being, the air velocity THROUGH THE WHOLE INTAKE SYSTEM will be moving slower. Remember, everything in an engine has to work together. NEVER look at anything independently. If you change one thing, you affect everything else.

Think of an engine (or a car) like a huge pan of water 100 ft by 100ft, but only a 1/4 of an inch think. If you make a change inthe system (drop a stone in one end) you will see the affect in the whole system.



>Making the engine struggle to suck in through a small opening (makes >high velocity) doesn't increase hosepower

This is only true if the opening isn't the right size. You are generalizing way too much, it's more complex than that.

The opening/intake/exhaust/whatever you are talking about has to be the RIGHT SIZE for the application.

What am I talking about when I say "application"? I mean:

1. the engine displacement
2. the engine rpm you want to have the most power
3. the volumetric efficiency AT THAT PATICULAR rpm

If you wanted our cars at 2.0L to have maximum power at 4000 rpms, didn't care about what happened above that, and had 100% volumetric efficiency at that 4000 rpms then our stock tb would be too big. A smaller one (as well as smaller intake, narrower intake runners, smaller intake plenum, ect...) would be ideal.

If you want our cars at 2.0L to have maximum power at 7000 rpms and you have 100% volumetric efficiency, then (fromt he calculations referenced before on Howell's site) a 52mm throttle body should do.

Now, if you were turning 8500 rpms with race cams, that TB would be too small and the engine would be struggling to suck alot of air through too small of a hole.

See what I mean? You are correct when you say "IF the engine is struggling." The pointof all this is, at 7000 rpms in moderately modified form, our engines ARE NOT STRUGGLING with the stock throttle body.

Okay, okay. I'll bet no one's thought of this: what if I had a 60mm throttle body... and an E-Ram? AAAACK! Just kidding! But seriously, Jim, have you made those "dyno" pulls yet? I'm really curious, even if the results are not representative of a DSM with stock cams.

Sorry bout the delay. I couldn't do this till tonight. I was able to get 6 good runs on the Jeep TB and 5 on the stocker. And the averages are - Drum roll please....
Jeep TB - 10.48 @ 68.7mph
Stocker - 10.57 @ 68.4mph

The best run actually goes to the stocker - I managed to clock 10.39 @ 69.9 mph. On the Jeeper my best for the night was 10.41 @ 68.9. Maybe I'm a shitty drag racer cause I just don't think I got any really good launches with the Jeeper tonight. I got a couple with the stocker.

Actually, I don't use the SFC much for timing runs cause of the whole not spinning the tires on takeoff thing. I usually use a stopwatch on the same 1/4 mile(approximately) stretch. I've actually made ALOT of timed runs on that stretch. The best I ever got with the stocker was 15.6(repeatedly-many times) and the best I can get with the Jeeper is 15.4(repeatedly-many times). So my setup seems to like the bigger TB.

So there you have it. Some dyno runs or even timed runs on stock cams would be a way better measure for most of you, but I do what I can. Both Bill and Todd hit the nail on the head - everything effects everything. I don't want to beat the velocity horse to death, but I've got some shit goin on with air flow and the 60 helps me right now. Also remember - I have NOT port matched the manifold to the TB.

I bought a spare manifold to machine for my 8-injector system and I JUST finished port & polishing it last week. It looks SWEEEEEET. I'm actually going to port match the TB on that manifold and I will definately make some timed runs(on my favorite approximate 1/4 mile race track). Hopefully it'll help me N/A, but the goal on that whole project is to get some BOOST! }(


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

A little follow up to last night's escapade. I was thinking about it, and I honestly didn't feel like I did to well last night. The roads were a bit damp and thats why I blew so many launches with it. Anyway I still had the stocker in there today, just driving around a bit - getting used to it again. I tried practicing the "SFC safe" launch with it and got it pretty good. The roads are completely dry tonight and it is also a bit cooler tonight as well - so I decided to make a couple of SFC timed runs with it.

I was getting better times with the stocker and then I made a REALLY good 10.06 @ 70.2mph run on with it. It was a great launch and I really nailed the shifts. I was so impressed with it, I HAD to put the Jeeper back on to see if I could whoop it. 15 minutes later I was on the same stretch and beat it on the first pass with a 9.77 @ 72mph. Again - great launch and really nailed the shifting.

So just some more times to look at, but I guess my point is that I think I'll stick with the 60mm Jeep TB on my non-port matched manifold for now.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

Hey Jim, do you think the performance would go down with the p&p manifold? I'm trying to picture the airflow based on the times you've given. It seems like the difference between the two is nominal, as in, getting the bigger tb hasn't destroyed performance, but it hasn't really helped either.

I'm thinkin since the manifold is still restrictive, the tb isn't really doing much to affect performance.

On a side thought, would the diameter of the piping on an intake affect this airflow too? Injen's intake starts at 3" and then bottlenecks to 2.5 right before it connects to the tb. I think AEM's is 2.5" and stays that way all the way through.

>Hey Jim, do you think the performance would go down with the
>p&p manifold?

Absolutely not. Performance will go up - times will go down. I don't know what they were smoking when they made the molds for these manifold castings and the template for the upper to lower gasket, but it must have been good. Alot of material needs to be removed to properly port match the manifold sections. The upper to lower gasket actually hangs out into the stream - it needed to be cut back. Also, the port outlets to the head have a severe angle on the bottom of the port.

Here's some shots of the upper manifold. It was the worst off as far as port sizing. ALOT had to be removed to port match it.

This one compares an initially ported runner(left) to one that hasn't been touched(rigt). If you look really close at the one that hasn't been touched(left) you can see the score marks that I made from the gasket.


Here's a closeup that shows how much actually needed to be cut.


Here's a closeup of a finished runner


The finished upper section


Here's some pics of the lower section. The upper ports did not need much taken from it, but I did have to cut the gasket so that it wasn't sticking out into the runner flow.

This one shows how I cut the gasket. It only needed to be cut on 2 sides for each port - by about 1/16th of an inch.


The finished upper section of the lower manifold.


The ports to the head needed quite a bit of material removed to port match. Here's a side-by-side of an initially ported(right) and completely unported(left) runner.


This shot gives a good picture of how much actually needed to be removed to port match the head ports. It also gives a descent picture of how sharp the angle is on the bottom of these port outlets(somewhere around 40 degrees). I was able to greatly reduce this angle(to somewhere closer to 15 degrees), but it required a tremendous amount of porting.


So, most importantly, with a p&p all of the ports/gaskets are matched. I was able to smooth the surfaces of pretty much the entire bend, all the way from the plenum to the flat section in the lower manifold, which is good. Also, that severe angle at the head port outlet was a killer - I just HAD to make it more gradual. I should definately see gains with this.

Now if the original question was "Would performance go down if i port match the manifold to the TB?" - I'll find out soon enough. Before this thread started my thought was that I would see a gain, but now I'm not sure if I'll see a gain or not. I still do not think I'll see a loss.

My plan: What I'd like to do first is run the p&p manifold without port matching the Jeep TB and see what that gains it makes for me. I will definatly see a gain with that. Then, hopefully before I get the turbo on, port match the upper section to the Jeeper and see what that does for me performance-wise. By staging the mods like that, I'll be able to see what they give me individually.

>I'm trying to picture the airflow based on the
>times you've given. It seems like the difference between the
>two is nominal, as in, getting the bigger tb hasn't destroyed
>performance, but it hasn't really helped either.
>
>I'm thinkin since the manifold is still restrictive, the tb
>isn't really doing much to affect performance.
>

What do you mean it hasn't helped. It gives me somewhere around .2 seconds off of my 1/4 mile times - on an already fast(relatively speaking) car. If you look at the second post that I made with times, you'll see that I noticed the same .2 second drop on the 1/8 mile as well. I don't know but that seems more than nominal to me.

>On a side thought, would the diameter of the piping on an
>intake affect this airflow too? Injen's intake starts at 3"
>and then bottlenecks to 2.5 right before it connects to the
>tb. I think AEM's is 2.5" and stays that way all the way
>through.

Yes the diameter affects the airflow. I've always though that what really matters is to make sure that the intake piping(if you have any) is bigger than the TB. So maybe someone else can chime in as to which size is better.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

hey metal jim are you port matching the engine block cuz i picked up a stock intake manifold to port and match to my new mp tb i wanted to port what u had portd but i dont know about port matching on the engine block. should i still port it even though im might not port match>? will it be easy to do with the engine still in the car?

What did you use to port it and where did you get it? I have all kinds of spare parts laying around and would like to start porting stuff. I ported my TB but it took forever with my dremel.

Slow_AT - Yes it takes a long time to port. Thats just the plain and simple fact of the matter. I use a Dremel. I get all my bits at Home Depot. Here's a thread about the bits I use http://forums.2gnt.com/dcboard.php?az=show_topic&forum=5&topic_id=51893&mesg_id=51893&page=

Kamakazy - never port anything while it's on the car. Disassemble whatever you're porting and clean it as best you can before starting. Make sure there are no sensors or anything like that attached to the piece - you don't want metal shavings in your TPS or MAP sensor. Port match to the gaskets. If you're not gonna take the cylinder head off and (completely dissasemble it and) port match the intake ports to the gasket, well then the head ports may not EXACTLY match up to the manifold. I'm not sure how well the head matches the gasket. I remember replacing the exhaust gasket on mine, and the gasket seemed to match the head pretty damn good. But if the gasket doesn't naturally match up to the head then you have to take the head off and (completely dissasemble it and) port match the intake ports to the gasket as well. Then it'll be one smooth unobstructed flow to the valves. I think port matching the intake manifold side is still a good idea. If you want to do the head then here's a good article about doing it - http://www.sa-motorsports.com/diyport.htm There's some general good info about port matching in there as well.

And to answer your question am I going to port match the head to the manifold(gasket)? Hell yeah - as soon as the head comes off. I'm building a bottom end right now, so when it's ready for the head I'm yankin the one from my car. I'm planning on many many hours with me my head and my Dremel. Sounds like fun don't it? Like I said, the intake ports may already match up to the gasket naturally, but if they don't then they will after I'm done with the head.


95 Eclipse RS : 5 speed
Jeep TB writeup - http://www.dimensia.com:81/jimbo/JeepTBfor2gnt.html

After reading all of this, I think it is time for me to put my .02¢ worth in.
I am not an automotive guru, but my understanding is that the major part of making power in an engine, is to reduce the drag of pulling air into the cylinders as much as possible. the reason that I understand that you want to do this is because when your intake valves close off, you haven't pulled all of the available air into the cylinder, because of the vacuum that us created by the drag from the pistons pulling a large amount of air through a small opening. therefore, you are never able to fully fill your cylinders with their complete volume of air (there will always be vacuum in the cylinders before the piston begins to travel up again).
so the remedy to this is (in my understanding) to increase the size of your valves (and their lift), ports, intake runners, (and yes) throttle body. the enlarging of one without the proportionate enlarging of the others will only gain as much as the most restrictive part of the intake remaining. I think that the throttle body is probably the least of all of these, but I imagine that it would become more important if all of the other factors were improved.

I also am of the opinion that like an exhaust system, the factor of velocity being able to (scavenge) the exhaust out of your cylinders at lower rpms with a somewhat restrictive exhaust, is a trade-off for the restriction that is created at higher rpms. likewise the scavenging effect that the intake velocity has to push air into the cylinders at lower rpms with a somewhat restrictive intake, is offset by the restriction that is caused at higher rpms, where a much larger flow of air is needed.

none of this takes into account the possible affects the a less turbulent flow might have on the fuels ability to atomize properly and burn efficiently when mixed with the incoming air.

or maybe I have been drinking WAY too much coffee again.

It is cool that Metaljim took the time to make those runs but in simple truth it means nothing. Do to the fact that the weather can change an e.t. for the most consistant of cars. I worked at a speed shop for 2years in H.S. and dynoing some thing in is VERY time consuming. Water, oil,and air temp along w/ berometric presser and humidity are huge factors. When it is 95 out and track temp is 125 my civic runs 19.2 w/ night falls temps go down I throw on a bag of ice 17.8s start popping up. This is deff. a test for a dyno!

There is also the fact that most guys run c.a.i. and as you speed up you get a ram air effect which in hand moves more air into the engine. all these relative flow ratings don't mean anything without testing. But to say it is not usefull to go 60mm is a little off. If I had a stock motor w/ NO mods then yes a 60mm is pointless. But with an air intake, header, and cat back you move more air and are able to move even more air. So adding a 60mm t.b. will give you more air to move.

So if after you read this thread and want to trash your 60mm and kick the dirt in anger you can just send them my way :D

A 60mm is still too large with all the bolt ons based on volumetric efficiency. You will still see gains over stock, but the question is will you see gains over a bored stock tb. Dunno. Someone needs a dyno to find that out. Theory only goes so far. If you go forced induction it is a whole other story.