Thread: 3.5 and 4 inch exhaust... whos gottem

Any car making over 350 crank Hp a single 3" exhaust is a restriction as per Berns stainless

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Interesting to read. I know many people making big hp on a 3". Not saying what was stated was false just interesting.


BTW I hope all is well bro. You should try to make it this way for the Convention.

The challenge quickly becomes getting the piping to fit. The resonator that is on my 97 was a hand build 4 inch can. It is tucked up high & tight and that car is not slammed by any means and I have still managed to drag it over speed bumps. Cost is also major testicle for most as 3-1/2" mandrel is well, not cheap.

If you are after more of a fun car you can always expand the exhaust tunnel and give up some of the interior creature comforts...

I've found on a few sites that the 350 hp range is where 3 in would start becoming restrictive.... How restrictive when wanting 400 hp, not so much when so much fab is involved at least in my life right now. One day someone with nothin but time will hopefully post his before and after dyno charts from his full 3" to full 3.5 or 4"

Not to mention we only make that in boost unlike a all motor car it's kinda a balancing act for both hp and drive ability. Personally I'm going to have a 3.5 inch dp and then bring it down to 3 inch after where I set it up for removal for track days.

If I ever put the big boy pants on and throw a big turbo on a big bore engine then I'll continue the 3.5 after the dp. Maybe do something like split to duel 2.5 inches underneith the oil pan for clearance then switch back to single 3.5". As for the rear suspension hump it seams like the only thing to do is notch the frame out. One thing is for sure though I'm def gonna hold that stainless exhaust by lam park as the model to go by its mighty purity.

I'd still like to see the 3.5/4" exhaust that exists out there have a pic and description in this thread. Full... Side exit... Bumper exit... Hood exit... Whatever get'm in here

There are simple and easy ways around the 3" becoming restrictive. Run it out the hood or bumper, length wont affect flow especially if its somewhat straight. Or if you want the full exhaust, run a 4" downpipe and where it goes under the car transition it to 3" for clearence. By the time the exhaust gas reaches the section it merges down to 3" it will have cooled enough that the 4" is not needed anymore. Higher hp #'s create heat and with heat the exhaust gas wants to expand so a larger ID pipe is not needed the entire length, in theory

Here's mine

always is lol Couldn't resist calling it out.

I know - that was intentional - the exhaust on the 97 B14 might as well of cost me my left nut




But it's purrrrrty, is quiet and works great.

I have the same on my 425whp S13, lol. My favorite sounding exhaust for an SR. Sad to see it go when I swap everything over to my S14, lol.

Not to go off topic but the old Blitz NUR Exhaust for the S13/S14 sounded awesome from the distance at night in the mountains.

The old APEXi 3-1/2" from the late 90's was nice but dam it was loud.

I had a Greddy Power Extream 2 on my old S13 and it sounded very good too, all stainless with a nice huge stainless resonator.