3" or 4" turboback exhaust setups.

[diambo4life]

Ok....i really hate the exhaust on #476. I feel like it has one bend too many and I was wondering what the general consensus was on exhaust routing in these cars. I would like something that is as straight as humanly possible that can let the car breathe. Can you guys post your setups please? I personally like Magnaflow mufflers....oval even though #476 came with a round one. Anyone with 4"? Any fitment/clearance issues?

 

[gaylantvr4]

I have had both 3 and 4 inch exhaust and the 4 inch was close to the ground and with a lowered car was a pita to navigate around bumps. If your looking for peek power the 4 inch made more peek power but it felt as if i lost alot of low end power. so i switched back to a 3 inch and the low end came back but lost the gained peek power. For a street car i would stick with 3inch. The 4inch drowned alot when crusing

 

[prove_it]

4in is overkill unless your running a 60lb/min turbo or bigger. If you do go 4in, spend the money and get oval exhaust, it's still only 3in tall, but flows like 4in due to the oval.

Plenty of people have run 3in exhaust into the 700hp range. Yes, straight is the best, but straight up through the hood is the most free flowing. O2 housing design makes a huge difference too. That's always the weak link in my opinion.

Also are you dumping the wastegate to ground?

 

[CutlassJim]

Quoting gaylantvr4:
If your looking for peek power the 4 inch made more peek power but it felt as if i lost alot of low end power. so i switched back to a 3 inch and the low end came back but lost the gained peek power.



There is no way this is a true statement if this is a turbo car. The only way to lose low end from an exhaust is increased back pressure causing a higher boost threshold. So unless you are saying that the 4" exhaust had more restriction than the 3" then I call BS.

 

[turbowop]

I agree. Turbo cars are all about pressure differential. You want the least amount of back pressure on the outside of the exhaust housing as possible to allow the turbo to spool up faster. There is plenty of backpressure in the manifold and turbine housing already. You shouldn't be seeing power drop at any RPM with a larger exhaust on a turbo car.

That said, NA cars can benefit from a tuned diameter exhaust to create velocity and help scavenge exhaust gas from the cylinders.

 

[JNR]

4 inch is too big on these unless you are running some crazy setup.

If you really want that though and you have limited ground clearance then look at oval tubing...will cost more and limit your muffler choices but then again these are near the rear bumper so transition back to round after coming up again.

 

[diambo4life]

Car has a 3" exhaust on it even though it's not a true 3" since it starts as a 2.5" at the O2 sensor housing and then flares out to 3". The bend by the diff seems to have been banged up and constricted it some. Yes...wastegate is externally dumped. I drive this car all the time on the street so it has to be reasonably quiet and also be legal for IFO FIS class. So hood exit (which would be ideal in weight savings and least exhaust restriction) is kinda out of the question. My car is also lowered so I can see the big 4" being an issue. The weight too....Sigh. Just being undecided what I want to do with it. Thanks for the input.

 

[prove_it]

A true stainless 3" system will weigh around 20lbs, if that. With stainless the wall thickness is much thinner which is where the weight is. Also, I've seen good results with a thick wall aluminum set-up, which sheds loads of weight, but the thicker walls make for about a 3.5" OD pipe.

 

[CutlassJim]

I've been intrigued by cat back aluminum set-ups but I've heard bad stuff about even the more durable AL's resistance to corrosion. There was a kid in my area with a 3" aluminum setup on his SRT-4 and it sounded amazing.

 

[prove_it]

We did a aluminum cat back on a GTR, a full aluminum exhaust on a 800hp 2G and neither car melted the piping. As long as it's a good 1/4" wall thickness, I don't think it would melt. In theory it could, but only seen it on thin walled piping.

 

[JNR]

Wouldn't 1/4" thk aluminum defeat the purpose of any weight savings? Alum is about 1/3 the weight of carbon steel and ss is a little heavier than cs...

I take it that was actual pipe used vs tubing then?

.083 wall thickness is pretty stout for stainless and is the bigger wall thickness on typ ss tubing. Seems that would be aroubd equal wt to the alum mentioned... .049 inch would probably be sufficient and there is .035 available too but getting pretty thin.

 

[CutlassJim]

Quoting prove_it:
We did a aluminum cat back on a GTR, a full aluminum exhaust on a 800hp 2G and neither car melted the piping. As long as it's a good 1/4" wall thickness, I don't think it would melt. In theory it could, but only seen it on thin walled piping.



I'm talking about corrosion from the elements. North east boy checking in.

 

[prove_it]

No one I know had used their aluminium exhaust in winter, so hard to say, but my guess is that it won't like the salt.

As for weight, it's still fairly light. Close to SS from what I remember, maybe a couple lbs more. The cost was less which helps.

 

[diambo4life]

Decided I will just keep my exhaust and add a manual cutout to the DP.