TQ is for getting out of the line faster, HP is to get you there faster and HP is what you need at the upper RPMs, not TQ.

Having more TQ down low to get you going faster is more useful than upper. But HP is what you need and a exhaust will give you that at the upper rpms.

 

BTW - you can't read evidently. Try reading it again. Also, there is probably too much in that article for you to understand. Perhaps you should ask for clarification, instead of challenging someone to force them to explain it to you.

Rick

 

I beg to differ. you want torque down low and hp high. a better powerband will always net a faster car. you know, unless it's 200whp good powerband and 500whp peaky output!

 

corrected...

 

There is a reason why the Stillen has a H or X pipe. Forget what it had exactly.

 

corrected

 

I think the APS 2.5" true dual and the Injen SES don't have a H- or X-pipe at all.

 

really? weird! well, I am proved wrong then edit: I just looked and the AAM true dual does not equalize as well, I am sorry, I was wrong.

 

Here are some excerpts to further prove my point:

"Some stock mufflers have up to 18 psi of power-robbing backpressure. A well-designed performance exhaust typically has about 2 to 6 psi of backpressure. For comparison sake, an unmuffled straight pipe usually has 1 to 3 psi of backpressure."

hmmmm....

"If the exhaust pipe is too large, the flow will be sluggish with low velocity and the scavenging will not be as good. Remember that a good exhaust has low backpressure and high velocity. The only possible exceptions to this rule are for turbocharged or nitrous engines. It is almost impossible to put too big of an exhaust past a turbocharger as a turbo's efficiency depends a lot on the pressure differential across its turbine."

hmmmm....again

"Whatever you do, do not remove or gut out the catalytic converter on your street car. The monolithic, straight through design of modern 3-way catalytic converters is usually quite free flowing on most modern sport compact cars, producing at the most, only a pound or two of extra backpressure. A gutted cat can actually hurt power as the empty box can cause flow stagnation, which effectively shortens the length of the moving gas column in the exhaust pipe. The empty box can also reduce important flow velocity. This can be felt as a loss in bottom end power.
Because of these factors, some of our project cars have actually gained power with the addition of a cat. As the number of vehicles on our highways grows every year, we must all do our part to manage pollution. If every last bit of power must be extracted, as in real, off-the-street sanctioned racing, then the cat can be removed and replaced with a length of pipe, not simply gutted."

hmmmm....yep, again!

Now, I never said backpressure was good for performance. So please don't say that I did. In context, I fully agreed, several times in fact, that high velocity is exactly what you want, with minimal backpressure, not increased backpressure. It's the small amount of negative pressure at the end of the pulse that allows the vacuum to happen, which in turn scavenges those exhaust gasses, further enhancing a cars performance, via a better burn in the chamber.

When I say OUR cars need a little backpressure to run properly, that is the point I am making. A very small amount of backpressure actually perpetuates better scavenging effect. In turn, more HP and TQ.

I don't know your experience at all, when it comes to exhaust building and dynamics or testing, especially on the our cars and the VQ and it's variations. I've built and designed and tested many exhausts for this specific engine and it's variants for about 8-10 years now. I have dyno'd full open header systems, open pipe systems, and various versions of restricted systems (mufflers, resonators, etc.). I have been building cars for more than 20 years as well. Some cars professionally and some as hobby builds.

It has always been true, that when the exhaust on these cars is left with no backpressure at all, which can be accomplished with open header designs, that the cars produce less TQ and HP. Thereby providing a less powerful car overall. A little backpressure, less than 8lbs and more than 2 lbs, have always yielded a better power band, more torque and more HP.

That isn't necessarily the case for every car and every build. This discussion is specific toward the cars we drive. The turbo car for example, suffers from just about ANY amount backpressure at all, the same goes for Nitrous cars and most supercharged cars. In fact, the design of such systems, and the resultant increase in both intake and exhaust pressures almost zero's out backpressure completely. But there is still ~1-3lbs detectable. Typically, on a turbo car, you pretty much can't have a large enough pipe...the larger the pipe, the more freely and efficient the turbo will work. This increased velocity also cancels out the effect of ZERO backpressure.

OK - I'm done now.

Rick

 

Chris don't interpret the article.

"Remember that a good exhaust has low backpressure and high velocity. The only possible exceptions to this rule are for turbocharged or nitrous engines. It is almost impossible to put too big of an exhaust past a turbocharger as a turbo's efficiency depends a lot on the pressure differential across its turbine."

I'm beginning to wonder if your exhaust knowledge is based purely on this article and if you have actually studies and experimented extensively with these cars at all. It also seems that you mis-quote the article, extensively, thereby making it seem that you don't necessarily understand what they are saying completely as well.

Go ahead and take your car and remove the catback, perform a dyno. Wait 2 hours for it to cool before and after, then install the catback and dyno again...you'll become a believer pretty quickly.

Chris - There is no 1 way of doing anything, and no 1 way that covers EVERY situation. There are theories and general ways of thinking, however, and most will apply in most cases. Hence the word MOST.

Rick

 

This is a perfect example of seeing an effect (lower power) and associating an unrelated cause (not enough backpressure). It is a common misconception and nothing you should be ashamed of.

Chris

 

No - interpreting again.

LOW not NO backpressure! RRREEEEAAAADDDDD!!!!

As you are dodging the questions about your experience and any testing or expertise in this subject, you should probably back down and OUT of this thread.

Until you have tested and actually done any real research and R&D for these cars, your interpretations and assumptions are only attempts to save face. At least let us know how you can possibly attest to facts you have never tested of verified, other than reading it somewhere. Even though the resource is deemed very reliable, the result of which is in general terms, not specific.

Rick

 

Oh yea..forgot. Again you were out of context. Too much backpressure is a bad thing (for performance), not enough is also a bad thing, as velocity and scavenging (both highly related) effects will suffer a bit, and lower power with ZERO backpressure, unless a car appropriately built to work specifically like this. You know - over 800 HP or so in an FI/Nitrous car - well then, by your posts, maybe not.

Rick

 

Hey were all not pros at back pressure and exhaust part, but take it easy. We know your the pro... explain without being a d!ck. Everyone has different ways to doing exhaust. Take it easy take breaths chillax Expalin it and dont talk down to people, even if they make comments. Your a sponser, remember that(for your sales ) Even is we all can't "read" and are dumba$$es.

Chris

 

OK - so I'm not talking down to anyone - I was attacked and told I was completely wrong and didn't know what I was talking about. I'm entitled to defend, whether a sponsor or not, what someone with less experience under their belt is throwing around.

If the attacker is going to post wrong info - and it can be corrected for everyone's good and education - there is benefit for that.

For the record - I didn't start the SH$T slinging - but do have the right to defend it. Why is it that when a sponsor defends what they have a right to, and are proved correct, that the attacker who continues to taunt, is deemed as innocent?

Double standard...hmmm...

I know many are not backpressure pro's - which is exactly why my main post was so long - to educate on just that, as well as support my research and development. Many spew lots of crap on these boards, and if your post count is high, many will believe you by default - it's not always the case. Look at my posts before passing judgment on me...I help and answer questions FAR more than asking them.

Rick

 

BTW - my post #35 on this thread, is my first response to the first attack. That user never responded back and was replaced by another - HyperSprite, who felt compelling enough to start his own uprising.

Although I did have to defend a few attacking statements in that post, the 'book' I wrote was the supporting information. HyperSprite gave a link to an article, which I agreed with and complimented, by the way, and he came back at me...again putting me is a defensive position.

Normally I would defend via PM's and not hijack a thread like that, and for the OP, I am sorry for that. If I disappeared, you'd all think he was right, when is wrong in much of what he has posted, therefore, I had to correct it appropriately.

Again - sorry for any problems this may have caused anyone. It was initially, purely educational in intent.

Rick

 

I completely agree with Rick on this one. Exhaust systems need a little bit of back pressure unless they are fully built n/a motors or turbocharged/supercharged or nitrous fed motors.

If you have ever disconnected your exhaust you would know exactly what he's talking about. You gain top end but your low end suffers. What he is trying to explain is by adding a muffler or resonator, you increase back pressure by a little bit and you take away a little bit of top end and bring back the low end. It makes a lot of sense.

This is why top exhaust manufacturers like greddy, HKS, apexi, JIC, and many others have a muffler + resonator on their cat-back systems and not just one muffler or no muffler at all.

 

Thanks for that...and another note as well:

The power band with a ZERO backpressure design as mentioned above, will kill the entire power band up to about 6200 RPM...only then dos it begin to make itself up. If you can rev to 7200-7400, you can take advantage of this increase, all the while loosing MANY 10ths and car lengths in a race due to the power loss in 90% of your power band.

Rick

 

Yup.

The only time a single pipe going back is useful is when you have a fully built motor which runs a very high compression ratio and a wild race cam with a very lightweight flywheel. At that point, you won't even be in the lower rpm's so it makes a lot of sense to stay in the upper rpm's. See folks, you can learn something from your sponsors on the forums.

 

I don't mean to step on ya...but:

A single 3" is pretty much equal to a dual 2 1/2" setup. If the Y is made properly to flow right, get the pulses in order, and the muffler is good flowing as well, it will work great. Personally - I prefer a true dual. There are two sides to the engine - two sides to the car - two wheels on each side of the car as well.

I like the ability to absolutely tune the exhaust for performance and balancing the pulses properly. Scavenging the gases, and tuning for that, is much easier on a true dual.

Rick