This maybe a possible repost, but I thought it'd be helpful since a ton of people go back and forth between 55's, 60's, and a 57.


49mm TB flows 252 cfm
52mm TB flows 283 cfm
55mm TB flows 317 cfm
60mm TB flows 377 cfm

At 8200 RPM a 122 cubic inch engine will need 290 cfm at 100% volumetric effiency, using the formula ((Max RPM/2)*Displacement)/1728. Rule of thumb is to go 10% over because a naturally aspirated engine can go above 100% volumetric efficiency because of cam overlap, header design, etc. Go above that and you kill low end because of reduced velocity, go below that you starve the engine for air at top end. 110% is volumetric efficiency is 319 cfm

It came from here:
http://www.allpar.com/neon/performance.html

but it applies to us just the same.

Dude it's like beating a dead horse. These kids who believe their 60-70mm tbs "make them faster" will NEVER believe your numbers. I'd say just drop it :shrug

Well this def helped me. Ive been contemplating on what size to get, and I didnt even have to search.
Thanx for the info, points for you!!

Originally posted by a_miller_76
Dude it's like beating a dead horse. These kids who believe their 60-70mm tbs "make them faster" will NEVER believe your numbers. I'd say just drop it :shrug

lmao, but maybe if its repeated over and over again it will catch on ;-) a good refresher to post for those thinking of buying one :thumbsup

i just went 55 because i am lazy
the opening on our intakes is within a mm of 55 when i measured mine so that was the less work to match up

besides concept illusions will do your stock to 55 and powdercoat for half the price of a 60mm

so ok i am cheap and lazy

You should also point out if you get a TB bigger than the opening in your intake manifold it's pointless unless you port out your intake manifold. I saw a kid with a 60mm tb or something on his Honduh once and when you opened the plate and looked at the manifold there was this wall of metal. So he had a 60mm tb with a 45mm opening. Sure it made you faster :rolleyes

Hey,
i have an afx 55mm and i was considering selling it and getting a 60mm because i got my intake manifold ported to ~59mm. I guess i should stick with the 55mm :shrug

Originally posted by ajcfalcon
Hey, i have an afx 55mm and i was considering selling it and getting a 60mm because i got my intake manifold ported to ~59mm. I guess i should stick with the 55mm :shrug

Yup, until you go turbo.

well in that case im glad you posted this man!

yea all this VE this, VE that doesnt really matter to a boosted car

a 60mm throttle body will flow more air, so if you're making any decent power...i wouldnt stick with a 55mm for to long

Originally posted by turbo8u
yea all this VE this, VE that doesnt really matter to a boosted car a 60mm throttle body will flow more air, so if you're making any decent power...i wouldnt stick with a 55mm for to long

Having a throttle body too big can hurt overall performance, so unless you seriously changed the air flow characteristics inside your engine, I wouldn't use anything bigger than 55mm throttle body.

I'd say that a turbo is 'seriously changing the air flow characteristics' of your motor.

I figured if people had a formula they could read, then they'd understand them. This is more relational to stock, but should even hold true with mild mods.

Yeah, this really only applies to N/A.

Originally posted by WickedESi
Yeah, this really only applies to N/A.

Yes it does. But there are SOOOOOOOOOOOOOOOOOOOOO many newbs on here that think bigger is better no matter what. Like that guy with the 8 injectors, 70mm tb, and dual 3" exhaust on a NT car. You CAN NOT tell him that he's got a fucked up set-up because he believes what he wants to believe.

So volumetric efficiency of a turbo motor has no bearing on its power production? Riiiiiight...

Originally posted by DarkOne
So volumetric efficiency of a turbo motor has no bearing on its power production? Riiiiiight...

Yeah but isn't the posters math based of NT statistics? I understand that VE is important in all internal combustion engines, but I'd think blowing 15psi into an engine as opposed to being NA would change your TB CFM requirement drastically.

Originally posted by DarkOne
So volumetric efficiency of a turbo motor has no bearing on its power production? Riiiiiight...

no one said that choad.

what we're saying is, when the engine is being fed boost, VE rises to 120 or 150 or even 200%, air flow through the throttle body at 80% VE (naturally aspirated), and airflow at 200% VE are going to be entirely different. we didnt say anything about power persay. double the VE, and you effectively double the engines size...so yea, more ve = more powah.

Originally posted by turbo8u

Originally posted by DarkOne So volumetric efficiency of a turbo motor has no bearing on its power production? Riiiiiight...

no one said that choad. what we're saying is, when the engine is being fed boost, VE rises to 120 or 150 or even 200%, air flow through the throttle body at 80% VE (naturally aspirated), and airflow at 200% VE are going to be entirely different. we didnt say anything about power persay. double the VE, and you effectively double the engines size...so yea, more ve = more powah.

Thank you for clearing that up for the benefit of all those people who don't know better.

Well, is 55mm going to cost bottom end enough to effect the car's use as a daily driver? I have a MSD Blaster coil, MSD 8.5mm wires, new NGK plugs and a short-ram by AEM, and am looking for the next step before exhaust. Since I use my car as a daily driver, am I better off getting the 52mm port by Concept Illusions to maintain low-end power, or can I go for broke and get the 55mm bore?

Originally posted by silverarrow
Well, is 55mm going to cost bottom end enough to effect the car's use as a daily driver?

Oh please. This is like asking if your plug wires are going to net you a power gain.

Originally posted by DarkOne

Originally posted by silverarrow Well, is 55mm going to cost bottom end enough to effect the car's use as a daily driver?

Oh please. This is like asking if your plug wires are going to net you a power gain.

I love how now that you're not a mod you let all that anger fly instead of bottling it up LOL

dude, get the 55. i noticed a BIG difference in top end, and especially throttle response. i didnt feel a loss in low end power AT ALL.. but then again i have a lot more mods than you. Get the 55, if you dont you will want to later.

Originally posted by cougar694u
Go above that and you kill low end because of reduced velocity, go below that you starve the engine for air at top end.

I never said I was going to run 13s with my car with nothing but a sack of rice. All I am asking is, if the quote above is true, will my car be affected by 55mm as opposed to 52mm? I am taking this one small step at a time, so yeah, I won't be netting any major power gains anytime soon (I also plan on staying NA). I am doing this step-wise and therefore have immediate concerns (driving in stop and go traffic) and long term concerns (is this one mod worth it in the end when everything is eventually completed).

Originally posted by silverarrow
...is this one mod worth it in the end when everything is eventually completed...

Yes, just do it. If you're gonna pay to get a 52mm, just take that extra step and get a 55mm.

Originally posted by silverarrow I am taking this one small step at a time, so yeah, I won't be netting any major power gains anytime soon (I also plan on staying NA).

Now theres a bright idea, should i even ask why he wants to stay NA.
F***ING WASTE OF TIME AND MONEY!!!!!!!:wallbash

Originally posted by CustomGS

Originally posted by silverarrow I am taking this one small step at a time, so yeah, I won't be netting any major power gains anytime soon (I also plan on staying NA).

Now theres a bright idea, should i even ask why he wants to stay NA. F***ING WASTE OF TIME AND MONEY!!!!!!!:wallbash

I plan on staying NA. What's wrong with that?

Originally posted by cougar694u

Originally posted by CustomGS

Originally posted by silverarrow I am taking this one small step at a time, so yeah, I won't be netting any major power gains anytime soon (I also plan on staying NA).

Now theres a bright idea, should i even ask why he wants to stay NA. F***ING WASTE OF TIME AND MONEY!!!!!!!:wallbash

I plan on staying NA. What's wrong with that?

Have you driven a boosted car? Not a boosted 2gnt necessarily, but a boosted car in general? There's no comparison bro.

Originally posted by a_miller_76
Have you driven a boosted car? Not a boosted 2gnt necessarily, but a boosted car in general? There's no comparison bro.

I've driven everything from my brother's 540 HP mustang to a VR-4 to a GS-T to a stock 420a. My point was simply that it depends on what he/she is trying to do, or wants to do, with their car. It's a matter of preference and choice. I don't want to turbo my car, ^^^^ doesn't want to turbo theirs either.

Maybe they're intimidated by the install of a turbo kit, but who fuckin cares?

I was just curious dude. A lot of guys who've never experienced REAL horsepower think that a modded 2gnt is "fast" when it's no where close being NT. The fastest NT is still like 14.9 or something which isn't really that fast. Not saying I could come close, and Todd is a fucking awesome driver, but in the grand scheme of things it isn't that fast.

NA, 2GNT, and FAST....are not allowed in the same sentence unless its covered in sarcasm

Defintely true - Investing in any power adders on a 420A Eclipse aside from turbo is a waste of money and time.

Take it from someone who is on their second Eclipse, and has already tried the first route... it doesn't even compare to a turbocharged setup. Day and night.

yea i was thinking about going NA, but then you read all the posts about people going NA and almost spending as much money on their motors, and they're not even getting 200whp, if you're going for all out performance, turbo is the way to go, don't blow it all going NA, look how much this guy put into his motor, and how little power he's getting out of it http://forums.2gnt.com/dcboard.php?az=show_topic&forum=32&topic_id=1711&mode=full

Originally posted by BlackMagic
yea i was thinking about going NA, but then you read all the posts about people going NA and almost spending as much money on their motors, and they're not even getting 200whp, if you're going for all out performance, turbo is the way to go, don't blow it all going NA, look how much this guy put into his motor, and how little power he's getting out of it http://forums.2gnt.com/dcboard.php?az=show_topic&forum=32&topic_id=1711&mode=full

uhhhh, ever consider nitrous? thats NA....

Originally posted by 97whitESi

Originally posted by BlackMagic yea i was thinking about going NA, but then you read all the posts about people going NA and almost spending as much money on their motors, and they're not even getting 200whp, if you're going for all out performance, turbo is the way to go, don't blow it all going NA, look how much this guy put into his motor, and how little power he's getting out of it http://forums.2gnt.com/dcboard.php?az=show_topic&forum=32&topic_id=1711&mode=full

uhhhh, ever consider nitrous? thats NA....

well it's NA in the sense of not having a turbo, but nitrous is still considered a "power adder", but yea im sure nitrous can be very effective, but turbo is more efficient power source.

okay,

look at my mod list...



whats an ideal TB size for me? 55mm?

Originally posted by turbo8u
NA, 2GNT, and FAST....are not allowed in the same sentence unless its covered in sarcasm

New quote for me....Thanks Turby

Originally posted by SilverBullet20g

Originally posted by turbo8u NA, 2GNT, and FAST....are not allowed in the same sentence unless its covered in sarcasm

New quote for me....Thanks Turby

have you ever had a NT 2gnt want to race you? LOL! its beyond embarassing... its like brrrringggg bahhhhh dinggg bahhhh. OWNED.

Originally posted by cougar694u

Originally posted by CustomGS

Originally posted by silverarrow I am taking this one small step at a time, so yeah, I won't be netting any major power gains anytime soon (I also plan on staying NA).

Now theres a bright idea, should i even ask why he wants to stay NA. F***ING WASTE OF TIME AND MONEY!!!!!!!:wallbash

I plan on staying NA. What's wrong with that?

Absolutely nothing wrong with staying NA...If you dont want a fast car..I dont want to shit on anyones hopes and dreams,and there are a few built 420a's making some good power (at the crank) without forced induction. But, Cost effectiveness goes out the window and the hp#'s are nowhere near worth it. I would say that 99% of this board feel the same. I respect the work that is put into all motor 2G's but i will never respect the power capability of it.

Originally posted by CustomGS

Originally posted by cougar694u

Originally posted by CustomGS

Originally posted by silverarrow I am taking this one small step at a time, so yeah, I won't be netting any major power gains anytime soon (I also plan on staying NA).

Now theres a bright idea, should i even ask why he wants to stay NA. F***ING WASTE OF TIME AND MONEY!!!!!!!:wallbash

I plan on staying NA. What's wrong with that?

Absolutely nothing wrong with staying NA...If you dont want a fast car..I dont want to shit on anyones hopes and dreams,and there are a few built 420a's making some good power (at the crank) without forced induction. But, Cost effectiveness goes out the window and the hp#'s are nowhere near worth it. I would say that 99% of this board feel the same. I respect the work that is put into all motor 2G's but i will never respect the power capability of it.

I'm not doing it to be fast, I've already got a fast car. My 2gnt is a toy to play with.

Originally posted by silverarrow
I never said I was going to run 13s with my car with nothing but a sack of rice.

Sigged.

Originally posted by cougar694u
This maybe a possible repost, but I thought it'd be helpful since a ton of people go back and forth between 55's, 60's, and a 57. 49mm TB flows 252 cfm 52mm TB flows 283 cfm 55mm TB flows 317 cfm 60mm TB flows 377 cfm At 8200 RPM a 122 cubic inch engine will need 290 cfm at 100% volumetric effiency, using the formula ((Max RPM/2)*Displacement)/1728. Rule of thumb is to go 10% over because a naturally aspirated engine can go above 100% volumetric efficiency because of cam overlap, header design, etc. Go above that and you kill low end because of reduced velocity, go below that you starve the engine for air at top end. 110% is volumetric efficiency is 319 cfm It came from here: http://www.allpar.com/neon/performance.html but it applies to us just the same.

i beg to differ with this..

you fail to realize that VE is also dependant on the pieces that FEED THE CYLINDERS..

so... even 10% extra.. you have to take into account, your air filter, your throttle plate.. turbulance.. friction losses..

besides.. your only moving the torque curve.. you only lose power if your bench racing with a dyno sheet.. dyno's lie.. stop watches are a better indicator of power

ever flow an intake manifold without a TB on it.. how much you wanna bet it chokes at about 225CFM..

our engines are *similar* to a neon engine.. but VERY different with regards to the heads, the manifolds and just about all the little things that make a difference in regards to flow.

the turbo guys get away with making more power because they compress the air.. NA guys don't have it soo easy.

there is a reason the fastest NA car is only making about 170hp or so.. and it's got nothing to do with the size of the throttle body.. or the cam.. or the port work.. or the header

There is no magic bullet.. until you figure out the systems your dealing with.. no amount of bolting crap on will help unless you get extremely lucky.

Originally posted by WheatKing
besides.. your only moving the torque curve.. you only lose power if your bench racing with a dyno sheet.. dyno's lie..

yea when you're on a dyno, you don't want to look for max power, you want to look for the largest area under the curve, if you know what i mean, so everyone when you go to the dyno next time, know your calculus!