🔧 Technical Exhaust cutout for boost

[Pro Stock John]

Stock exhaust was 2.75 for this engine.

2.5 it is.

 

[Pro Stock John]

Mr Ice cream we should be on the same team but you hatin' on this 2.5" setup.

Let me know when we are lining up, you got 250rwhp on me.

 

[IceCreamAssassin]

Mr Ice cream we should be on the same team but you hatin' on this 2.5" setup.

Let me know when we are lining up, you got 250rwhp on me.

If you want to do 2.5” that’s fine. I’m just really having a difficult time understanding how you are coming to the conclusions you are. Like the difference between a 2” and 2 1/2” (because you don’t want 3”) with the same exact layout and muffler/piping…. The 2” with just sound more raspy and hire pitched. Also aiming the exhaust down at the ground under the car will make is resonate and seem louder than it really is. I used to have dual 2 1/2” stock exhaust after the cutout, legit sounded like the car had a bad miss because so quiet and big cam. ( there is a video of it in my thread). You do you man, just trying to help you do it logically. Just because you want quiet doesn’t mean you can’t have it flow semi decent as well. If it doesn’t then you are gonna be running super rich when the cutout is closed because of all the less air movement.

 

[Yaj Yak]

Stock exhaust was 2.75 for this engine.

2.5 it is.

that stock exhaust for that engine had a turbo on it too?

 

[Turbocharged400sbc]

This irks the hell outta my inner gearhead.

I'm going to hose clamp a duck call to your exhaust when you're not looking

 

[Jimy Bilmo]

This irks the hell outta my inner gearhead.

I'm going to hose clamp a duck call to your exhaust when you're not looking

Whistle tips

 

[Pro Stock John]

Not sure why you guys are stuck.

 

[Yaj Yak]

i'm pretty sure you're the only one stuck in this thread

 

[Jimy Bilmo]

1.5" or bust.

 

[Jimy Bilmo]

Wait wait wait.... hear me out.

TESLA SWAP

 

[Turbocharged400sbc]

I would rather he keep that stump grinder of a LS motor

 

[Pressure Ratio]

3" dumped exhaust will still be pretty loud based on personal experience, so at a minimum I'd go with 2.5".

The exhaust size has less to do with volume if the exhaust than what it's capable of flowing. Some mufflers are designed for sound wave cancelation. Then besides that you can also add quarter wave resonators, or what ever the exhaust industry is calling them. It is literally a just a tube that is a specific length that runs off the exhaust. It is a specific length because sound waves enter it, bounce off the end of the tube and head back to the exhaust opening. The entering sound wave ends up canceling the outgoing sound wave. This is a great way to eliminate exhaust drone too.

My Capri had a 5" downpipe to dual 3.5" aluminum exhaust. With out tail pipes the car was loud and shook the ground at idle.

With just installing the tail pipes, the car was whisper quiet. Like on a pass the Turbo was louder than the exhaust. Just adding length to the system and directing the sound and pressure waves out the back of the car made a huge difference. With some effort, the right parts, math, and tuning, you can change the exhaust note and volume dramatically.

I'd do at least a dual 2.5 or a single 3". Because what happens if you like the quiet exhaust a lot? But can't use it at more than partial throttle? I'd say do it right and make the quiet exhaust useful for more than idle and 15% throttle. Then the 4" is for max flow and power as well as a party trick at cruise night.

 

[Jimy Bilmo]

Then besides that you can also add quarter wave resonators, or what ever the exhaust industry is calling them. It is literally a just a tube that is a specific length that runs off the exhaust. It is a specific length because sound waves enter it, bounce off the end of the tube and head back to the exhaust opening. The entering sound wave ends up canceling the outgoing sound wave. This is a great way to eliminate exhaust drone too.

He doesn't want a helmholtz resonator, already mentioned that to him.

 

[Pro Stock John]

I'm not doing exhaust to the rear for a few reasons one is that my fuel system takes up most of the underside of my trunk area, I run two fuel pumps.

I'm not doing 3" either I have done that before and I'd need to add in a big muffler to get it as quiet as I want.

I think a 2.5" with a canister style muffler turned down at the rear will get it done.

I live 1.5 miles West of Wrigley Field and get stuck in a lot of traffic.

 

[Yaj Yak]

The exhaust size has less to do with volume if the exhaust than what it's capable of flowing. Some mufflers are designed for sound wave cancelation. Then besides that you can also add quarter wave resonators, or what ever the exhaust industry is calling them. It is literally a just a tube that is a specific length that runs off the exhaust. It is a specific length because sound waves enter it, bounce off the end of the tube and head back to the exhaust opening. The entering sound wave ends up canceling the outgoing sound wave. This is a great way to eliminate exhaust drone too.

My Capri had a 5" downpipe to dual 3.5" aluminum exhaust. With out tail pipes the car was loud and shook the ground at idle.

With just installing the tail pipes, the car was whisper quiet. Like on a pass the Turbo was louder than the exhaust. Just adding length to the system and directing the sound and pressure waves out the back of the car made a huge difference. With some effort, the right parts, math, and tuning, you can change the exhaust note and volume dramatically.

I'd do at least a dual 2.5 or a single 3". Because what happens if you like the quiet exhaust a lot? But can't use it at more than partial throttle? I'd say do it right and make the quiet exhaust useful for more than idle and 15% throttle. Then the 4" is for max flow and power as well as a party trick at cruise night.

 

[Jimy Bilmo]

Oh, now we're at least up to 2.5" from 2". Next you'll tell us you're running it to the rear and have a helmholtz resonator added to kill any drone.

 

[Yaj Yak]

is anyone ( Pro Stock John) opposed with me changing the title?

cuz this ain't about others.

 

[Pro Stock John]

Fine i'm back to 2 then.

 

[Yaj Yak]

Fine i'm back to 2 then.

 

[Jimy Bilmo]

 

[Yaj Yak]

thread's like this miss M@ being around to just cockslap serious engineering info into the mix with a hint of sasss.

 

[Yaj Yak]

thread's like this miss M@ being around to just cockslap serious engineering info into the mix with a hint of sasss.

To the first question, it's a fundamentally flawed question. You're making unreasonable assumptions that just because a turbo is physically larger, it is more efficient, which is not necessarily the case. Also, you can in no way assume that because a turbo has a larger compressor, it also has a larger exhaust turbine or housing. Fail number one.

To the second question, if you're trying to choose a pipe size, you need ALOT more information. One incredibly important piece of info you're missing is pipe length. Your head loss in a pipe flow situation will be determined both by pipe cross section AND length. You also need to determine an acceptable quantity of head loss over the course of said pipe length, as there is NO way to have zero loss over any nonzero length of pipe (or likewise, any finite diameter of pipe).

So, now, give us the maps for both the turbine and compressor of both turbos in question, as well as the pressure ratio and airflow numbers for the motor in question and we'll work on an answer for that one....and while you're at it, fill in the necessary info for your second flawed question as well.

Your thread blows dude.

I think I still have my pipe flow fluid calcs excel sheet...

Ridiculous iterative calculations, and silly if-then loops and shit, but it does a bang-up job calculating pipe flow stuff. The only real right way to get an answer in doofus's second question though. Wonder if he has any more silly questions with incorrect answers to make himself feel cool...

almost applies to this thread..

 

[Yaj Yak]

You still made unreasonable assumptions in BOTH questions.

You assumed that just because one turbo has a larger cold side, it will also have a larger hot side. Very unreasonable assumption.

You also supposedly calculated a pipe flow question with no regard to pipe length, so you calculated nothing. Even more unreasonable and wrong.

This thread is a waste of space.

fuck he had some gems.

 

[Bob Kazamakis]

I'm not doing exhaust to the rear for a few reasons one is that my fuel system takes up most of the underside of my trunk area, I run two fuel pumps.

I'm not doing 3" either I have done that before and I'd need to add in a big muffler to get it as quiet as I want.

I think a 2.5" with a canister style muffler turned down at the rear will get it done.

I live 1.5 miles West of Wrigley Field and get stuck in a lot of traffic.

What’s your tank setup look like? I’ve got dual 3” with a stock tank and the cars decently low. F and A body rears aren’t all that different. Tip sits behind the quarter panel

 

[Fish]

thread's like this miss M@ being around to just cockslap serious engineering info into the mix with a hint of sasss.

I just miss M@