i have an eclipse RS...quick questions

will three inch exhaust piping help any with adding horsepower to my 420a? If it does what kind of gains are we talking about? i don't know if this questions been asked before so yea

no. you will lose enough power in the bottom end to not make it worth the extra gain up top.

Try replacing the muffler, as it is the most restrictive part of the exhaust system.

A 3 inch exhaust on a non turbo eclipse is too big. You will end up with less exhaust gas velocity and loose power. Bigger isn't always better.

The stock piping is identical to the piping on the turbo Eclipse. It's fine for the stock turbo, and we're pushing a lot less exhaust gas then a 210hp turbo, so it should be fine for us too.

Originally posted by VX100
Try replacing the muffler, as it is the most restrictive part of the exhaust system. A 3 inch exhaust on a non turbo eclipse is too big. You will end up with less exhaust gas velocity and loose power. Bigger isn't always better. The stock piping is identical to the piping on the turbo Eclipse. It's fine for the stock turbo, and we're pushing a lot less exhaust gas then a 210hp turbo, so it should be fine for us too.

Up to a point if you really start building the engine the stock axhaust provides a restriction, but 3" is not going to help unless you are turbo. 2.5" should be fine for any NA set-up.



15.9 @ 86.7mph
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sigh, wrong, wrong, wrong. You can't go "too big" on the exhaust. Now, with your minimal mods, you may not see much of a gain from a 3" over a 2.5", but you will see a gain, and you WON'T (again, I could give two shits what everyone else says, if they disagree, they're wrong, we've been through this) lose power down low. SCC cut off the exhaust and put on 3" straight pipes on two seperate cars (one was a SE-R, the other a honda) and BOTH of them made more power EVERYWHERE in the power band. Let the internet myth die guys, seriously. Is it worth the extra cost for a 3" over a 2.5" for you right now? Probably not, but will you lose power because of it? Hell no.

Originally posted by 98Talon
SCC cut off the exhaust and put on 3" straight pipes on two seperate cars (one was a SE-R, the other a honda) and BOTH of them made more power EVERYWHERE in the power band.

I like how you quote a magazine as gospel :thumbsup

Have you ever tried this yourself?

Talk to Borla, one of the premier companies that makes performance exhaust for many years. Ask any other people that know the automotive performance and thermodynamics.

Hot gas flows better than cold gas. The bigger the pipe the slower the gas moves, the faster the gas cools off.

If bigger was truely better, we'd be running around with 5" exhaust systems on our cars.

Just because a 3" pipe worked well on one car does mean it's the perfect size pipe for every car. Cam profiles, engine displacement, turbo, supercharger, NA. The entire set up dictates your optimim exhaust pipe diameter.



15.9 @ 86.7mph
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>sigh, wrong, wrong, wrong. You can't go "too big" on the exhaust.

:rolleyes

Um, suuurrreee. Yes you can have too big of an exhaust, if it is a non turbo. A turbo car is a different story. (as I like to say, a turbo changes the rules) We're talking naturally aspirated vehicle dynamics.

>Now, with your minimal mods, you may not see much of a gain from a >3" over a 2.5", but you will see a gain, and you WON'T (again, I >could give two shits what everyone else says, if they disagree, >they're wrong, we've been through this) lose power down low.

WHY will you see a gain? Explain to all of us how or why EXACTLY, my car, right now, will see a gain from putting on a 3 inch exhaust.

Go ahead, we're all listening....

Also explain WHY, EXACTLY, you won't see a loss in the car's bottom end?

What is exactly going on when you have exhaust gas going through an exhaust pipe? What is going to happen when you increase the size of that pipe? What is that exhaust gas going to do differently? What is the effect on the engine?

How does fluid dynamics and thermodynamics come into play here? How are those two principles even RELATED to the workings of an internal combustion engine? Think about this, for god's sake! Learn the theory, do the reading and research, then reason it out!

Why can't people actually THINK and FIGURE THINGS OUT ANYMORE?!?!? We're supposedly the smartest creatures on the planet, but some people continue to just follow what other people say like sheep because it's the first thing they hear.

Why do people still believe this "bigger is better" crap at face value?!?!? Don't just quote what the riceboys say and what is written in a magazine trying to sell you parts, and don't just believe what you want to believe so you can rationalize the $600 you spent on your 3 inch exhaust. (yea, it MUST be faster! look how much money I spent on it!)

You'd better give a hell of alot more than two shits about what other people say, because quite frankly if you REALLY TRULY BELIEVE that a 3 inch exhaust won't cost bottom end on one of our cars, let alone make the car run like absolute shit, then you don't understand engine dynamics. Period. Stop spreading mis-information.

Explain to all of us EXACTLY, HOW and WHY myself, and so many other people, are wrong. Explain why what I've seen from driving my car and other cars with different exhaust setups, and why what other people have seen, is totally wrong.

I'm sure you can back up your reasoning with technical explanations and also correctly explaining the fundementals of how an internal combustion engine works to support your reasoning.

PLEASE GO AHEAD! :D I want to hear this one!

>SCC cut off the exhaust and put on 3" straight pipes on two seperate >cars (one was a SE-R, the other a honda) and BOTH of them made more >power EVERYWHERE in the power band.

Everywhere, Eh? As every good scientist says "show me the data"

Of course they made more power, they completly removed the mufflers, those stock mufflers restrict so much that it had better have gained power.

But that doesn't mean a 3 inch exhaust is optimal for a small displacement engine, versus a different sized exhaust.

I drove a 2GNT with a big 2.5 or 3 inch exhaust on it (I don't remember the size exactly, I think it was 3 inch, I can confirm it if you like) and you know what? It had NO BALLS. It was SLOW. It was so much slower than my car in the low end and the mid range, I was shocked. It was so much slower, I did not need to strap it to a dyno to know it had less power. It was blatantly obvious.

And know what else? I'm not the only person who has driven a 2GNT with a 3 inch exhaust and one without and noticed the difference.

I wasn't even the only person to drive THAT EXACT SAME CAR with the 3 inch exhaust and say "it has no power" afterwards.

Quite frankly, I trust empircal evidence and practical experience over a rice-boy magazine essentially advertizing 3 inch exhausts anyday.

>Let the internet myth die guys, seriously.

It's not an "internet myth." Seriously. It's based on the sound understanding of the dynamics and operation of the internal combustion engine.

The MYTH is that "bigger is better" when it comes to exhaust size. We've been trying to educate people that the "bigger is better" method of modding a car isn't always right, and the reasoning as to WHY THIS IS SO. It looks like we've still got more work to do.

If "bigger is always better" then explain to me why our cars don't have 3 inch exhausts on it from the factory? I'm sure you can put a muffler on a 3 inch exhaust to keep it quiet, so sound can't be the issue. And it has nothing to do with emissions. And in the grand scheme of a car, a 3 inch pipe isn't that much more money for a car manufacturer, so it's not going to cost them too much money.

So why do we have a 2 inch exhaust, and not a 3 inch exhaust? Why does the STOCK TURBO ECLIPSE have the EXACT SAME sized pipe?

I'm sure Mitsubishi WANTS to sell slow cars. I'm sure they strive and go out of their way to handicap their HP ratings as much as possible, so the competition can advertise thay they have more HP in their cars and sell more cars than Mitsubishi.

I'm sure every car company follows this same reasoning, and every car company doesn't have many highly educated and experienced automotive engineers designing their engines for them, who know FAR more about the internal combustion engine than me, or anyone else here on this board.

Why doesn't a Corvette have a 5 inch exhaust? You just said you can't go too big on exhaust! So why not? They have a 5.7L V8, they must absolutely NEED a 5 inch exhaust, because "bigger is better."

So why do the Corvette designers, or Viper designers, or Ferrari designers, who are all striving for ultimate performance, not have 5 inch exhausts on their cars?

>Is it worth the extra cost for a 3" over a 2.5" for you right now? >Probably not, but will you lose power because of it? Hell no.

Not only is is not worth the extra cost, you'll loose power as well.




Ok, If you want a technical explanation, I'll give it to you.

But FIRST, YOU are the one who is so certain that you can't go "too big" with an exhaust. So, FIRST, I want YOU to expain WHY.

You spoke up, so let's hear it.

(I know exactly what you're going to use as the cornerstone of your argument. I'm waiting for the magic word.... I'm conjuring it up right now.... I know it's coming... you're going to say it..... I know you will, since every "bigger is better" proponent uses it.... but the funny thing is, IT is the real "internet myth" .... here it is .... backpressure.... backpressure... backpressure...)

I'm no expert at this. I'm a chemist, not an automotive engineer. But, I have practical experience, I know a little something about fluid dynamics and thermodynamics (that whole scientist thing), I know others with even more experience modding cars that me, and I know people who have been racing and building engines for DECADES. So I will do my best to present the information and explanation so as to be perfectly clear.


So, what is going to probably happen here is you will give your explanation, I'll will give mine (and, concequently, shoot your explanation full of holes), and you will STILL not believe me, or anyone else here. So after you don't believe me, here is what I propose. Get the exact same mods on your 2GNT (or anyone elses) and mine, except put a 3 inch exhaust on yours and I'll keep my GS-T muffler, and I'll GAURANTEE you I'll win that race.

(DAMN, I feel like Mototool right now, and it's not a bad feeling either }(

Heh, if he doesn't like the fact that "bigger isn't better" for exhausts, then he'll REALLY flip when he hears "bigger isn't better" for tires either!)

It looks like Mike, mototool, and I were thinking the same thing :)

And Mike, you gave a part of it away! I was waiting for him to try and defend his position first :P

Would you still lose power on just a 3" catback? I thought the stock downpipe and Cat would provide enough back pressure as to where no power will be lost?

Originally posted by 98Talon
sigh, wrong, wrong, wrong. You can't go "too big" on the exhaust.

Hah, you're so wrong it's sick.

I'll be brief:

N/A, perhaps a tad larger is better - maybe 2-1/4" or 2.5" ehxuast, however you will lose low end power. A naturally aspirated engine needs a bit of backpressure.

Turbo, bigger is better. Backpressure is the enemy.

$600 exhaust? No thanks, I custom built mine on my turbo, and on my NA (ohmuhgod, did he say it?) '98 Talon I ran an open header half the life of the damn car, and it's faster. I did a direct comparison between the car with and without open header, on the same night, at the same track, and my car was two tenths faster in the 1/8th with open header than it was with full stock exhaust... Thermodynamics are great and all, but I measure by timeslips. Oh, and with the SCC thing, I'm not taking what a magazine said as gospel, but when there are back to back dyno charts on two seperate, NA cars, it's kind of tough to argue... You don't need backpressure to make power.

Originally posted by 98Talon
$600 exhaust? No thanks, I custom built mine on my turbo, and on my NA (ohmuhgod, did he say it?) '98 Talon I ran an open header half the life of the damn car, and it's faster. I did a direct comparison between the car with and without open header, on the same night, at the same track, and my car was two tenths faster in the 1/8th with open header than it was with full stock exhaust... Thermodynamics are great and all, but I measure by timeslips. Oh, and with the SCC thing, I'm not taking what a magazine said as gospel, but when there are back to back dyno charts on two seperate, NA cars, it's kind of tough to argue... You don't need backpressure to make power.

Two tenths faster in the 1/4? You must have dropped your 60ft time by one tenth on that run. :thumbsup I'll be back in a bit, i'm going out to the garage to design and build a 8" exhaust since bigger is better :P A DYNO is the ONLY way to really tell the difference in power your engine is making, not time slips..way too many variables with the track, eg- air temps, traction, shifting, 60 ft times, you get the point..I want to see DYNO graphs of the engine with that exhaust setup, over a smaller exhaust setup

Okay, I'll scan them in tomorrow if I get a chance, or you can pick up last months Sport Compact Car. I ran 3 10.1's then 4 9.9's in the same night, it dropped .2 (in the 1/8th) after I lopped up the exhaust, I can't remember how much the mph went up, but I'll dig for the slips. I'm just trying to help the guy. I'm sure a 2.5" full exhaust would've helped almost as much as just an open header did, and it's really not worth the extra cost for him right now to go 3", I just wanted to point out that you won't lose power on an NA car with a bigger exhaust.

Then please go put a 4" exhaust on your NA.

There's a difference between open header and adding pipe. You have exhaust gases in a contained space not venting to atmosphere. ncec they've cooled off they don't like to move well, andthey are still confined in the exhaust. You have no scavanging effect taking place in the exhaust.

Can you please give me a technical resource that backs up bigger is better, in regards to exhaust pipe size?



15.9 @ 86.7mph
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and back pressure is of no benefit to anything other maybe a diesel engine. Dark0ne taught me that! It's all about velocity.

There. I contributed somewhat. :P

hmm I have a 3" exhuast system on my now NA eclipse. Lemme see what I can say about the power.

oh but I'm kinda cheating I have 10.5:1 pistons though. The power ok nothing too impressive. At about 3k you feel some power, then probably 4k-5k you'll feel it started take off. There isn't much lowend power enough to help it take off, but if you drove 3k on like a hill your not going anyplace fast haha.

The feeling is similar to my MR2. Hell maybe the MR2 is faster than my car now haha. But you can't feel a lotta torque but its accelerates kinda fast.

anyway 3" turbo only, 2.5" is all you need oh yes and 3" is very loud without turbo even with a resonator.

Originally posted by Ryan_Hes
Turbo, bigger is better. Backpressure is the enemy.

:rolleyes

This isn't correct, either.

Originally posted by mototool

Originally posted by Ryan_Hes Turbo, bigger is better. Backpressure is the enemy.

:rolleyes This isn't correct, either.

Backpressure is always the enemy. But exhaust gas velocity is also what spools your turbo. Fast exhaust gasses will will the exhaust behind it creating a scavanging efect that pulls exhaust through and keeps the turbo spooled. (not the best of explaination, but I haven't had my morning coffee yet).



15.9 @ 86.7mph
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98talon, those cars you mentioned has variable valve timing. Read what Todd wrote and understand it completely and you will see why those cars with variable valve timing see gains with bigger piping. Matt also made a point with conditions as a factor.

Make a dyno run with the stock exhaust, then a 2.5" exhaust, then a 3" exhaust, all on the same dyno session. THEN prove your point. Anything else is just theory.

Man than I really AM fucked! I'm building my 400+ horse big shot 351W and it's gonna be on 2.5" piping with an H pipe. I guess my drag racing experience, hours of watching engine dynos, and bench flowing heads means that all of my experience with engine flow is just crap. Thanks!:thumbsdown

Oh yeah, if your all about magazine numbers...SAE (Society of Automotive Engineers) offers a magazine to members each month and they have proved that 2.5" piping is good to 500 horse.

Originally posted by XtremeRS
Make a dyno run with the stock exhaust, then a 2.5" exhaust, then a 3" exhaust, all on the same dyno session. THEN prove your point. Anything else is just theory.

It's hard to dyno tune my tractor. Nobody wants to strap it down to their rollers :thumbsdown

The Calcium Chloride in my tires would throw off my dyno numbers anyway ;(

I have two instances, but they're both turbocharged, so it would only prove some of what has been said.

Scene 1: Friend at track running 116.5 mph multiple passes on a 2.5" exhaust. Drops his test pipe, makes two more passes, and ends up only running 113-114mph, with very similar ET's (within a few hundreths). The driving was still there, but the power isn't.

Scene 2: 3" exhaust, turbo tractor. Made 3 pulls, all within 5 horse of each other. Dropped the 3" exhaust. Lost 10-12 wheel horsepower, but gained 3 or 4 ft lbs. of torque at peak. No other changes made. Same dyno session. Within 15 minutes of each other.

:thumbsup

I was hoping UberXtremeRS2GnT-T would make me a 5" downpipe. I guess I'll have to JB weld my own now :(

From personal experience, 3 inch exhaust on NA BLOWS!!!! I got a 3 inch Tanabe and my car was just louder, but didnt feel any faster. Then i got UDP and intake and my car felt a little bit quicker, not too much. Then i got the ECU and i felt the biggest gain!! But i got tired of hte loud ass exhaust, so i sold it, put stock piping on with a GST muffler and HOLY SHIT!! My car felt like a completly different car. I got SOOOOOO much low end power. Then i got the Greddy and i dont feel a difference really, and its 2.5. SOOO...my point is, is that NA, 3 inch is way to much, and to be honest, i wouldnt do exhaust until you are turbo, or until you have done every other mod you can NA. I would recommend a GST muffler though, but thats it unless you are turbo.

I want a half-stack, like an 18 wheeler. Might let me run an 8" diameter pipe.

-=B-=

i have an apexi N1 3" catback
on my NA car

i lost some low end
it was not that big a loss

i gained some top end
it was very noticeable

i gained more
than i lost

i am happy

i plan to turbo

if i did not plan to turbo
i would have the 2.5"

-marc

='95 RS 5spd Red=
Matrix TypeX CAI
A'pexi Turbo N1
NGK Plugs
Accel 8mm Wires
Nakayama GT5 17's
Ractive STB
GSX Calipers
AEM 12.5" X-Drilled/Slotted Rotors

255 is fricken short

What a tearjerking poem...