CC29: The Right Exhaust Size Isn't Bigger

Our simple male minds always seem to dump into a "bigger is better" mentality. For many things this sort of thinking make sense. But for exhaust diameter, the logic breaks down.
A bigger exhaust CAN flow more air than a smaller one. But how much your engine CAN flow is a different amount of air. The goal of the exhaust is to flow the air the engine is capable of processing in the most efficient way it can. After tuning, improving airflow on the inlet, raising boost, and other upgrades the need for a larger exhaust is clear. The engine can support more airflow, so the exhaust needs to support it as well.
But there needs to be a realistic view of what the engine is capable of doing before the size of the exhaust can really be determined. The point is, the exhaust size is a tunable factor just like spring rates, the ride height and the damper firmness. More isn't always better!

[@McLovin0826]

Love these videos, your transparency is second to none

[@Heeltoe.]

I appreciate that!

[@subynut]

Really appreciate the down to earth explanation. It allows me to apply this same theory to my Subarus as well!

[@Heeltoe.]

It's good information to have.

[@1stGenCRXs]

This is especially true on a NA motor. I put a 2.5” on my B16 and it lost low end power. Put a 2.25 in resonator in the middle and got the most uniform power band. Funny thing was, I was much younger then, the guy at the muffler shop warned me that I was going to lose power but I wanted big!

[@Heeltoe.]

NA is such a special animal. There is absolutely a right way to do it and believe it or not sometimes the best way to know is by trial and error, AKA "Testing." A build B16A with big cams may have liked the 2.5" but probably only at top end.

[@1stGenCRXs]

@@Heeltoe. so true! That’s one great thing about the internet and forums now days. When I put the K24 in there was no question I was putting a 3in system in. So much data available on the web about what works. Back then it just didn’t exist like it does today. Others have done and shared the testing.

[@PiterStreak]

Solid topic marcus. I have to agree bigger isnt always better. I have pushed your 3" ATLP on the 3rd gen TL to 620whp without issues. The best sounding exhaust for that platform in my opinion. Unfortunately i made the mistake of going custom to squeeze as much out of the system and sound wise its no where near as good as the ATLP. A buddy of mine went from a 2.5inch tsudo to a custom 3 inch single exit. This was done because everyone and their mom in the 3rd gen tl community says single exit 3 inch is better measured by the butt dyno. Well, my buddy, who is also supercharged made 0 horsepower extra after going single exit from his tsudo. Made 506whp with the tsudo and made 506whp again with the single exit. Bigger isnt alwas better.

[@Heeltoe.]

Interesting about your buddy. On a 3g we definitely see a bump going from 2.5 to 3.0. Maybe there is more to the story on either side. Anyway, hard to say the same results will be there for all people. It's called TUNING!

[@joeholt7578]

The late 80' SLP did a single exhaust for the Firehawk and it was worth 15 hp more. But they couldn't give it away because everyone thought duals were better looking.

[@Heeltoe.]

A car like that 100% is only going to do well with dual outlets. Even the camaro and firebird in the 90s and 00s had a single exhaust to a transvers muffler with dual outlets in the back. Fastest way for a carmaker to make a car boring is to hide exhaust, and best way to make it sporty is to put dual outlets.

[@djsthemetereman]

Yes functionwerk sounds deep & aggressive plus paired with high Flow cats it sounds terrific but I also like the way ATLP sounds as well. IMR America has one but they use resonators & not mufflers so it's an even different sound, so great subject

[@Heeltoe.]

We'll find out how they compare directly in an upcoming video. IMR didn't incorporate the active valve.

[@djsthemetereman]

@@Heeltoe. That's true with IMR exhaust but yeah it would be great if someone would compare all 3 exhausts

[@jasonsharp4951]

I recently bought a 2008 TL type s. Was wanting to get an ATLP exhaust. I was interested in the 3” setup. Plan on getting a 3.7 intake and TB and probably a few other things with a tune. My question is do you think I should go for the 3” or 2.5” setup. I am wanting to stay NA

[@Heeltoe.]

If you are going to be doing those air/fuel upgrades and tuning and want the most peak power then it can make sense to do the 3". For more balanced gain and the resonator option to keep the interior sound lower, go 2.5"