Exhaust Suggestions

[Kibwe Walker]

If you are NA search for the "fireman exhaust"

since you have no rear diff to get in the way it looks like this


engine ======flowmaster 40 series about where the rear diff would be if you had one (single in dual out) to tips of your choosing on each side. Get a decent muffler shop to do it and you should come out around 300-400 depending on the tips you choose.

The 40 series on a NA 3s sounds pretty good (deep grumble) with a bit of raspy on a quick stab of the throttle. Also note that if your baffle system works in your plenum when the baffles shift for high rpm your exhaust tone switches from a deep grumble to a F1 style high pitched scream. Its pretty cool IMO.

[Kibwe Walker]

Originally Posted by jstarr427

custom is always good, I've got the borla with no mufflers and a 3sx DP and it sounds good. I'd like it to be louder, so im considering replacing the resonated tips (when they're off it sounds nasty ) either way for an NA I wouldn't do 3" back... 2.5" is good for a non turbo, anything really bigger than that and you'll lose torque and maybe a bit of power from the lack of backpressure... someone correct me if I'm wrong here but that's what I've been told several times.

You will lose a bit of bottom end yes but bottom end just spins tires in a NA anyways. You more than make up for it on the top side as I had 3" all the way on my SL.

You don't need backpressure in your exhaust, that is antiperformance. What you do need is delta pressure or a change in pressures because its the difference in pressures that causes gases to flow from a area of higher pressure to a area of lower pressure (down hill).

With that said the less back pressure you have and more cylinder pressure you have from the exhaust stroke the faster your exhaust gases exit the chamber (delta pressure), and that exit speed is crucial in a NA as it helps scavenge from different cylinders and also helps in coming fresh air come in when both valves are open briefly.

The more backpressure you have the more likely exhaust gases are going to revert back to the combustion chamber when both intake and exhaust valves are open and that spent exhaust gas hurts perfromance by displacing fresh o2 and inhibiting further combustion. So you want as little back pressure as possible well if you want more peak hp .

[veerfour05]

Originally Posted by Kibwe Walker

You don't need backpressure in your exhaust, that is antiperformance. What you do need is delta pressure or a change in pressures because its the difference in pressures that causes gases to flow from a area of higher pressure to a area of lower pressure (down hill).

With that said the less back pressure you have and more cylinder pressure you have from the exhaust stroke the faster your exhaust gases exit the chamber (delta pressure), and that exit speed is crucial in a NA as it helps scavenge from different cylinders and also helps in coming fresh air come in when both valves are open briefly.

The more backpressure you have the more likely exhaust gases are going to revert back to the combustion chamber when both intake and exhaust valves are open and that spent exhaust gas hurts perfromance by displacing fresh o2 and inhibiting further combustion. So you want as little back pressure as possible well if you want more peak hp .

Great post +rep for you sir.
That's a pretty brief explanation of NA exhaust tuning, but you get the idea. Like I was saying it is complicated, but if you know what you are doing you can actually put the VE of the engine over 100%.

[THE Phreak]

I'm getting mine done too, what sort of piping should I be looking for?

Cut peices that are welded together? I looked into mandrel bends and for some reason once you mention mandrel they charge extra.

[RedHotChiliStealth]

mandrel is the only way to go
dont even think about anything else

[THE Phreak]

Originally Posted by RedHotChiliStealth

mandrel is the only way to go
dont even think about anything else

And going mandrel is usually expensive, right?

[Kibwe Walker]

Originally Posted by THE Phreak

And going mandrel is usually expensive, right?

Yes but a 3" exhaust offers good flow up to and over 600 hp.

So its not likely to choke anything on a NA or even most tdo4 TT's unless you are pushing more than that hp.

[veerfour05]

Originally Posted by RedHotChiliStealth

mandrel is the only way to go
dont even think about anything else

x2. It may be more expensive but it is worlds better.

[jay04]

Backpressure is that wrong word here. You don't want any backpressure. Thats like sticking a potato in the muffler. Exhaust velocity is the right word. To maintain good velocity i suggest 2.5 on an NA unless u plan on doing cams, turbo and shit. Now on some cars you will not see a difference between 2.5 and 3.0 exhaust diameter. Anyway here is some more info:

The best way to make more power with the exhuast is to set it up in a way to promote exhaust velocity. Which is not nessesarily larger tubing. The tubing diameter selection is dependant on the amount of exhaust it will have to flow.

"As most of you know, the design of turbo exhaust systems runs counter to exhaust design for n/a vehicles. N/A cars utilize exhaust velocity (not backpressure) in the collector to aid in scavenging other cylinders during the blowdown process. It just so happens that to get the appropriate velocity, you have to squeeze down the diameter of the discharge of the collector (aka the exhaust), which also induces backpressure. The backpressure is an undesirable byproduct of the desire to have a certain degree of exhaust velocity. Go too big, and you lose velocity and its associated beneficial scavenging effect. Too small and the backpressure skyrockets, more than offsetting any gain made by scavenging"

Jay Kavanaugh, a turbosystems engineer at Garret

[jay04]

If your exhaust shop doesn't have mandrel bender, I've gotta good sit you can order the bends from.

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