What do you do when your exhaust is too JDM? Too JDM for 56k even?

[rustest86]

yea i forgot completely about older vintage motors....... most dont turn enough RPM's or have hot enough cylinder temps that would melt anything much less a valve..... lol

they were also as you said tuned that way also..... there werent any emissions or sound laws then to resticted them.

[rustest86]

so to summarize, unless it is tuned for no backpressure at all, every motor needs backpressure to run right. turbo motors inherantly have this. they are the kings of backpressure. the amount depends on the efficiency of the turbine and the volume of air being pumped in and then expelled. backpressure in the exhaust system will never be an issue untill it is close to/at the pressure before the turbine. this is where your have 2 problems, lack of performance and high EGT's. tooo high of EGT's is when something will melt. either valves or the turbine wheel itself.

on an NA motor, all having high backpressure will do is reduce performance. so you need to find a balance between having no backpressure and having too much that'll affect the performance.

[mattblancarte]

It's actually much easier to control fuel delivery via fuel injection as opposed to an older carbureted motor. Also, a lot of those dudes in the race cars are running pretty absurd compression ratios.

Yep, tuning is what it's all about.

[pacotaco345]

I hate how people say that 3" piping is too big for a 2 liter or even a 2.4, I have a 67 mustang with a 302 (4.8 liters) with two; i repeat two 3" exhaust pipes, and no one calls it overkill. A KA is essentially half a ford small block with twice the cams, same exhaust volume, even has more with a turbo... end of story.

[silviaslider37]

a great way to get rid of that exaust is to give me your silvia front ^.^

just cut or bend the brackets so it fits.

or you can always.

lol

[PyR0NiAk]

a great way to get rid of that exaust is to give me your silvia front ^.^

that makes no sense... How will giving you his Silvia front end, get rid of his exhaust?

[estrada42]

Well, since yo

a great way to get rid of that exaust is to give me your silvia front ^.^

Well, since you put it that way.....

Here's the side pictures, and a couple of how the pipe sits. Fitment would be much better if I had no hangers welded.

[rustest86]

man were way off the original subject, but see i just dont like that sideways ebay lookin muffler. i mean the whole straighter the shot the better the flow but come on, it doesnt make that much difference. look at mine:



thats a real apexi with a 4" tip, see how it tucked up away so it doesnt drag, most of its hidden under there. and my car is lowered 1.5" all the way around. it sounds great!!, has more than enough flow capability for my setup, and doesent attract unwanted attention like that big shiny megaphone there.

i do like that color though with the painted wheels, an almost stealth look
Modified by rustest86 at 3:03 PM 10/22/2009

[estrada42]

The painted wheels are actually the thing I hate the most about the car. I can't wait to get something better on there. Hoping to find some 280zx Turbo rims locally.

[AZhitman]

every motor needs backpressure to run right.

No.

Still no.

Never, ever, not, no. Period.

[AZhitman]

I hate how people say that 3" piping is too big for a 2 liter or even a 2.4, I have a 67 mustang with a 302 (4.8 liters) with two; i repeat two 3" exhaust pipes, and no one calls it overkill. A KA is essentially half a ford small block with twice the cams, same exhaust volume, even has more with a turbo... end of story.

Wrong again.

302 = 4949cc (rounded to 5-litres).

No one calls it "overkill" because no one probably cares to critique it. Old pushrod motors can get away with big honkin' pipes, and no one's the wiser.

A KA is not "essentially" half a SBF. Let's not spread misinformation.

KA's don't have competing exhaust pulses, nor do they have horizontally opposed cylinder banks, requiring a crossover or h / x-pipe.

Regardless of what you "hate that people say", you're gonna need to get over it, because you're wrong.

3" exhaust on a 2.0 liter engine serves no useful purpose other than to create stagnation and premature cooling of the exhaust gases, reducing flow.

Sorry if that doesn't fit with your worldview, but it's facts.

p.s. Apologies if this makes no sense, I'm jacked up on anaesthesia.

[PyR0NiAk]

p.s. Apologies if this makes no sense, I'm jacked up on anaesthesia.

What happened???

[rustest86]

but see your saying that a 2.0l, regardless if its boosted or not, still only needs enough flow for 2.0l. and while i agree with that for an NA setup, a turbo setup is different and does require more flow as there is more than just 2.0l going threw the motor. as long as there is positive manifold pressure the displacement is increased, not is terms of the motor getting bigger, but there is more air/fuel being crammed in there. enough sometimes to almost double the accual displacement. also as far as gasses cooling slowing flow...... we all know that turbo setups run extremely high EGT's so normally this isnt an issue.

also you say backpressure is bad? why? all turbo cars depend on backpressure and if it wasnt there we wouldnt have the force to spin the turbine..... so that how is good for tubo motors but not good for an NA? like i posted above unless its retuned to run no backpressure, it will cause a lean condition and burn valves......... am i right on all this so far?

i do agree with you that the exhaust should be properly sized and built for the application it is intended but come on, " backpressure is always bad" just isnt completely correct. im sorry

[mattblancarte]

You're misconstruing Greg's points, rustest86. I believe he applied the "but, if you're running a bunch of boost..." caveat to his argument earlier in the thread.

It varies from application to application. Displacement, compression ratios, boost, fuel, tuning, etc. are all pieces to the puzzle.

Actually, back pressure is compounded by turbos and the less restriction you have in the turbo-back exhaust, while still being able to clear the gases efficiently, is where you want to be. Really... NO turbo-back exhaust is the best POWER PRODUCING exhaust... Maybe a foot-long pipe that exits under the passenger side or something to protect the turbo's hot-side, but that's it.

Turbo motors are not really fans of back pressure at all... can't gather where you came up with that one... You always want max velocity, and max scavenging. Are you trying to say that it's best to taper turbo manifolds prior to the turbo to accelerate the exhaust gas, thus spinning up a turbine more quickly?

An example of back pressure being lame on a turbo car: buy a WRX or EVO, and simply slap a 3" turbo-back exhaust with minimal restriction and a muffler. You'll see pretty major gains because both the velocity and scavenging capabilities increased, and the back pressure was majorly DECREASED.

I can speak also for my motor (rb26 w/ stock r34 twins), and tell you that I could benefit from just chopping off my muffler and letting it run a straight 3" pipe. Last time on the dyno, I was standing about 25 feet behind the car and was getting BLASTED by hot exhaust.

Modified by mattblancarte at 11:40 AM 10/23/2009

Modified by mattblancarte at 4:38 PM 10/23/2009
Modified by mattblancarte at 1:01 AM 10/25/2009

[White Comet]

You're misconstruing Greg's points, rustest86. I believe he applied the "but, if you're running a bunch of boost..." caveat to his argument earlier in the thread.

greg was talking in cases of high boost applications, rustest86 is talking talking in situations of a boosted motors period

[mattblancarte]

but see your saying that a 2.0l, regardless if its boosted or not, still only needs enough flow for 2.0l.

I was addressing this claim, which I believe is unwarranted based on what I've read thus far.

Greg's right. 2.5" straight piping to a turbo muffler won't get it's butt kicked by a 3" configuration UNLESS there is a boat-load of boost coming from a big turbo.

A stock sr20det is just fine with 2.5" straight piping and a turbo muffler. That being said, a 3" pipe won't exactly hurt performance.
Modified by mattblancarte at 12:13 PM 10/23/2009

[dtowndrifter]

I dont dig the canister type exhaust no more..their heavy..i had one an got tired of it..i had a Apexi Gt Spec...It was sorry...Actually the baffles came loose on it an i cut it open an rewelded the baffles..

What i rock now, is a Buddy Club spec 2...I really fell in love with it...sounds nice on my stock redtop...I only went with Buddy Club cause it is the type i now like and its a reasonable price.. I could'nt score a Dart izumi or a old school Trust DD..

Hey man Estrada?! Do you have family in Dallas? I have tons of Estrada family in Cali i havent met..just curious..anyways the car looks good.

i had made this one with str8 pipes that are supposted to be mounted on a v8 truck or caprice or whatever..but i ended up getting rid of it..then i got the buddy

http://www.youtube.com/watch?v=IBtVuIFInz0

[AZhitman]

Now that I don't have a head full of anesthesia, I can respond properly.

To answer White Comet's question about his retarded friend's Integra:

"Simply, there is no properly tuned engine where increasing exhaust back-pressure causes an improvement - in power, torque or fuel economy. One of the reasons that this idea has gained support is because when people change their exhaust they seldom check the air/fuel ratio or re-map the ignition timing to once again give optimal performance. For example, some MAP sensed cars drop substantially in power with a large exhaust fitted because they are then running lean."

also as far as gasses cooling slowing flow...... we all know that turbo setups run extremely high EGT's so normally this isnt an issue.

Yes it is. Heat is relative. Slap a 4" system on a 2.0 running 8 psi and see how low your EGT's are downsstream.

also you say backpressure is bad? why? all turbo cars depend on backpressure and if it wasnt there we wouldnt have the force to spin the turbine......

No. They don't. You're thinking heat and exhaust gas velocity.

backpressure is always bad" just isnt completely correct. im sorry

You should be. If you don't have anything to back up a statement, it's best to keep it shuttered up inside.

However, it's a common misconception. I'm not making this stuff up.

Rather than me continually trying to dispel all these ignorant misconceptions, here's some mandatory reading for you guys... This way, I'M not the bad guy, and you're all gonna learn something. Happy reading:

[NOTE: If you choose NOT to read and educate yourselves, there's really no reason for you to continue posting in this thread. Education is power. Getcha some. ]

http://www.nsxprime.com/FAQ/Mi...y.htm

http://www.popularhotrodding.c....html

http://www.uucmotorwerks.com/h...h.htm

[AZhitman]

Also, I highly recommend the following two books:

http://www.amazon.com/Inductio...06911

http://www.amazon.com/Maximum-...r=1-1

[mattblancarte]

"Simply, there is no properly tuned engine where increasing exhaust back-pressure causes an improvement - in power, torque or fuel economy. One of the reasons that this idea has gained support is because when people change their exhaust they seldom check the air/fuel ratio or re-map the ignition timing to once again give optimal performance. For example, some MAP sensed cars drop substantially in power with a large exhaust fitted because they are then running lean."

Your example of the go-karts is a perfect example of causing the motor to deliver an improper amount of fuel, thus causing the AFR to run lean to produce excessively hot EGT. Removing the exhaust caused the tuning to go awry, thus causing the bad fuel delivery.

Modified by mattblancarte at 2:10 PM 10/20/2009

I should have mentioned this was also applicable to WC's teg question.

[rustest86]

what im talking about with backpressure on a turbo engine really isnt having to do with the exhaust system itself. i agree a short pipe straight off the turbo would be the best power making form of exhaust, but who wants that ticket? what im taking about is between the turbo and exhaust ports. the turbo is a phisical blockage in the system therefore creating backpressure. heat builds before the turbo because of the restriction. and as it gets hotter the velocity of the gasses increases past the turbine, spining it faster. but for this heat to build up you need the backpressure generated by the restriction of the turbo itself. right? is that not a form of backpressure, right?

and i never said lots/increasing the backpressure was good. but i did say that having no backpressure at all, which is what you saying, isnt good.

i also never said that it dosent matter what size exhaust you run, i did say that it should be built/bought according to the requirements of the setup, just like you said. and if someone was dumb enough to put a 4" exhaust on an sr,..... i dont even have a commet for that.

i also said that a stock sr wouldnt gain anything by going from a 2.5" to a 3". Quote, originally posted by rustest86 » backpressure is always bad" just isnt completely correct. im sorry "You should be. If you don't have anything to back up a statement, it's best to keep it shuttered up inside. "go pull the muffler off of you lawn mower the next time you start it and see how long it'll run before over heating and burning a valve. thats a simple form of why having no backpressure is bad without retuning it.

you cant just tell N/A people that having no backpressure at all with out retuning isnt gonna hurt anything, because it will. with a turbo back exhaust i agree, but N/A no i dont.

[QUOTE=mattblancarte]

I was addressing this claim, which I believe is unwarranted based on what I've read thus far.

from what was originaly said, that the stock exhaust would flow more than enough for a 2.0l if the bends were smoothed out, and wouldnt need anything bigger. maybe for a NA 2.0l, but not a turbo one. the way thats its worded that even a 2.5" is over kill for a 2.0l turbo unless there were massive amounts of boost being run.

but anyhow im done with this stupid arguement, ive been around cars/motors long enough to understand this stuff and sean first hand what can happen. and as my computer is acting all jacked up...... thank you bill gates for vista!!!!!

[White Comet]

Now that I don't have a head full of anesthesia, I can respond properly.

To answer White Comet's question about his retarded friend's Integra:

"Simply, there is no properly tuned engine where increasing exhaust back-pressure causes an improvement - in power, torque or fuel economy. One of the reasons that this idea has gained support is because when people change their exhaust they seldom check the air/fuel ratio or re-map the ignition timing to once again give optimal performance. For example, some MAP sensed cars drop substantially in power with a large exhaust fitted because they are then running lean."

the integra wasn't my friend's it was my wife's. so you're saying if the car was tuned and setup to run an open header it would have better acceleration then if it had the stock exhaust on it?

[PyR0NiAk]

From what I've been reading in one of the links Greg posted, the more restricted the exhaust is, the more low end torque you're going to have, but the more wide open it is, the more high end power you'll gain.

[AZhitman]

what im taking about is between the turbo and exhaust ports. the turbo is a phisical blockage in the system therefore creating backpressure. but for this heat to build up you need the backpressure generated by the restriction of the turbo itself. right? is that not a form of backpressure, right?

No.

That heat exists regardless.

COMPRESSION creates additional heat, but that's elsewhere.... Wrong end of the turbo. Which is why we have an intercooler.

but i did say that having no backpressure at all, which is what you saying, isnt good.

And you'd STILL be wrong.

Put a potato in your tailpipe and let me know how that works out for ya.

Seriously, there's a lot of good reading in those links I listed.

I don't link stuff that's gonna rot your teeth or give you AIDS.

So get to readin'.

[AZhitman]

Then my work here is done.

Using it as a refference is fine. But when you see these yahoo's claiming they're making "350hp, so I need 3" piping", they're confused. It's NOT the ONLY criteria.

There's SO much more to it than that.

The systems we build are STRAIGHT-THROUGH. Hold it up to the light, and you can see through it.

Compare that to a similar system with a baffled muffler, or [worse yet] a silencer, and you're damned right you'll need more diameter.

[PyR0NiAk]

Greg, this s*** is driving me nuts. I've been reading the exhaust theory from the link you posted of the nsx website. You said that choosing an exhaust size based on horsepower is "elementary". Yet, you even used horsepower as a reference in your BRM thread, and they used it as a reference as well. I actually haven't found an exhaust theory that DOES NOT state that anything with more than 400hp should have at least a 3" exhaust. So... Umm... Clarification please???

[PyR0NiAk]

Not trying to start a "BRM vs. X" debate, but it sounds as if you're saying the BRM system requires less diameter because of how straight through it is. This tells me that since other exhaust systems would require a 3" exhaust to support 400+ hp, a BRM would only need a 2.5" to do the same job?