He is correct


Very useful site please read guys http://web.tampabay.rr.com/redroby/3liter/exhaust.html

They are right, but a muffler's purpose is to reduce sound output, not horsepower! By reducing back pressure in an exhaust system, you increase high-end horsepower at the cost of low-end torque. You can compensate for this by increasing the velocity of the intake charge. Increasing the intake velocity has the added side effect of increasing back pressure, because there is more air to be evacuated during the exhaust stroke. Note that if you increase intake velocity past the limits of the exhaust system, the gains you achieve are diminished to the point of being non-existent. That power will be there when you do upgrade the exhaust system, which is why something as simple as upgrading the exhaust system can result in huge horsepower gains

There are limits to every situation, but a turbo of that size i doubt it's a wrong doing ..... If he's wrong for doign it then why do IHRA cars run no exhausts at all jsut a pipe off the turbo thats about 2 feet long

 

No, hes wrong and now your wrong because, and allow me to make this clear, a turbo engine always operates with higher back pressure on the head then would ever be considered remotely optimal in any situation.

Also, we don't need to worry about increasing intake velocity, we can merely increase our boost. That page you liked to was by no means a definitive tuning guide for cams and exhaust systems and while it made a few good(though obvious to any tuner) points, it doen't mater a whole lot to us.

We want to do what ever we can to reduce back presure at the head. This is our form of parasitic loss, equivalent (although far less then) a superchargers. We do not get a free lunch, even with turbo's

So now that we have established that we want to reduce back pressure at the HEAD as much as possible, the question we have to ask here is, whats the best way of doing that.

First, lets quickly go over exhaust on a n/a car. Exhaust is never a constant stream of air, but is actually a series of high pressure pulses followed by vacuum(or at least area of far lower pressure). These pulses are pulled forward by the vacuum in front of them. If you go with an exhaust system that it simply to large, this harmonic system breaks down, and you lose power. Generally going to an overlarge exhaust system increase back pressure at the head, and makes you lose power that way. Not having enough back pressure is fairly uncommon on a street car.

On a turbo car, this theory does not really apply a whole lot for 2 reasons.

A. The turbocharger itself ruins the harmonic pulses and breaks down the system. It turns from a harmonic system to a sewer pipe. At that point, bigger is better.

B. Turbos spool based upon pressure differential. Higher in the turbine, faster spool, lower in the downpipe, faster spool. When you step on the gas with a full 3 inch O2 eliminator for instance, you are going to get boost significantly faster, and those few PSI are already adding far more power then any affect harmonics might have played (which is zero anyways.)

So on a turbo car, after the turbine wheel, bigger is better, and non existant is best. a larger exhaust will create more power at EVERY RPM. If you think Im wrong, feel free to dyno it yourself.

 

Yes, the size does affect spool. Bigger spools faster. The problem is fitment and expense, and the diminishing returns you gain, but never theless, you never lose power, 3, 4, 5 or 10 inch, bigger is better.

Roll your eyes at someone else, after you learn what the hell your talking about.

 

ok, you win. Bigger is better. Spool is quicker with bigger pipes. Please, you're the one getting upset at a smiley for christ sakes!! . Sentitive aren't we. I undestand.

 

My understanding about turbocharged cars is that the most powerful exhaust is just a magaphone pipe after the turbo. In other words, the bigger, the better. My friend who races rally cars and works on them told me this. I should expect he knows what he is talking about since those guys go for maximum performance and they all do the same thing......

 

You are right, but to some extent. The downpipe on a turbo car is supposed to be .5" bigger than the turbin wheel, and the catback is supposed to be stepping up in size.

Since you have a Z, you probaly know that the fastest stock turbo z32s have two 3" exhausts.
In Japan there are several cars with 3"downpipes and 4" exhausts PER TURBO that make 750rwhp at like 22psi, no NOS. And that is with a set of twin TD06-20Gs. In teh US, with the 2.5" exhaust on a TD06 z32, they cannot touch 700rwhp, yet, at 30 psi.

I agree that if I put a 6"downpipe and a 8" exhaust that will kill the low and midrange, but my exhaust is only slightly bigger that the turbine major.

I KNOW that this turbo is huge, and that the exhaust should have been 4" ALL THE WAY, but putting a 5" with no muffler will improve the spoolup by a bit and improve the topend by a lot.

Check out the duno chart of the R95 Apexi exhaust. It is 95mm catback. The car in Japan did 36whp from a catback, and it still had teh stock downpipe. The spoolup was only 100-200rpms slower compared to the N1 3" exhaust.

 

Exactly, that is why we created something like a megaphone exhaust on ours.

3.5" o2 housing
4" downpipe
5" exhaust

George

 

Break some records!

You have to try for Pump Gas record, Stock 4G HP Record, Stock 4G Trap Speed Record! Besides your stock engine...thats as serious as it gets!

 

Hey George, obviously your car is treated as an off-road, race car, right? Otherwise I don't see any muffler shop doing a catless exhaust....... Anyway, I see why you went somewhere else for your exhaust as it had to be fabricated. My question to you is, do you guys do exhaust installtions in you shop?

Thanks,

 

tell you what, its stock, why don't you walk up to IHRA mechanics and designers and tell them that their exhausts are wrong.... I mean hey they only run a section of pipe off the turbo that can't apply much back pressure now can it?.... someone is doing sometihng right....


Hey boost when do you guys plan on getting the car started and begin tuning? I hope you make some small vids of it on the dyno or atleast on the track

 

Is that directed towards us or SuperZ?

George

 

first paragraph isn't to you it's to "itsstock" the second half is... when are you guys planning on getting the car started, i mean how far are you from it?

 

The only things left to do is install the IAT sesnor for the AEM, and relocate the battery to the back
Hopefully tomorrow night I will drive it

 

man, i feel for the local people who have to put up with listening to that monster.... please take a short video

 

man i had my wastegate open like that on my RRM turbo and i thought it was loud at 5 psi I can only imagine that sucker at 22 or whatever you wind up running hahahahah

AWSOME!!!!!!!