Boosted on stock 2.5" exhaust

[robvas]

Rather than peak HP & torque the curve of each is what i would be interested in. Broad flat curves are another set of goals to chase.

On this combination it looks like once it hit 450hp, there were gains to be had from the bigger exhaust

Interestingly enough as the RPM's climbed the advantage narrowed back down. Almost wonder if tuning the length of the headers or some other thing would change that.

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[sk47]

Almost wonder if tuning the length of the headers or some other thing would change that.

Hello; On an ENGINE MASTERS episodes they did just that. Tried different collector lengths among other things. Collector length made a difference. A sweet spot for their engine combination at around 18 inches. They also tested stepped headers with no real benefits as i recall. (Cavet again for a particular engine combination)

Hello; My recall was faulty there is a difference with that particular turbo setup. I detail more in a later post.

 

[illtal]

He just wants to know what does a full 3" get you from there. 910? 925? 945?

Well that's the thing, I don't think many of us will do that kind of testing because it's expensive. You would need to run back to back testing in a pretty short amount of time.

Most of us would just install everything then run it. If it's that important for him to know he can do it himself the. Let us know his results if he so chooses to do so.

Many people just do what they like on here then show the fruits of their labors after the fact.

 

[sk47]

Hello; Watched an ENGINE MASTERS episode season n6 episode 15 again. The have a V8 with a turbo. A 5.3 liter LS (LM7) iron block truck motor with upgrades. They run cast iron exhaust manifolds Hooker Headers specified for a single turbo application.
Turbo is an S480 with an 80mm billet wheel 1200 HP capable but tuned down to 600-700 HP. They use several sensors, back pressure included. Idea of episode is to try configurations a person might rune on the street.

They run 4 inch and later 3inch exhaust pipes with the purpose of finding out what adding mufflers will do to HP and back pressure.

4 inch straight pipe (open exhaust) yields 617.2 at 6000 peak HP & 575.5 torque at 5400

3 inch pipe with flomaster chambered muffler yields 547.6@5900 HP -519 @4800 torque
3 inch pipe with summit turbo muffler yields 461.8 @6300 HP-449.3 @4600 torque.
3 inch pipe with floMonster (straigh thru muffler) yields 579.7 @6000 HP 542.0 @5300 torque
3 inch pipe with no muffler yields 572.6 @5900 HP -536.4 @5000 torque

Kinda odd that the floMonster straight thru muffle beat a 3 inch straight pipe.

4 inch straight pipe short (open exhaust) yields 617.2 at 6000 peak HP & 575.5 torque at 5400
4 inch straight long (open exhaust) yields 623.2 at 6100 peak HP & 579.9 torque at 5400
4 in pipe with a Flomaster 4 in chambered muffler) yields 604.1 @6000 HP -563.2 @5300 torque
4 in pipe with Flomaster pro series yields 617.7 @ 6000 HP -580@5300 torque

Two items of discussion among the three on the show. First they felt the down sizing from the 80 mm turbo to the 3 inch pipe may have been the biggest problem with the 3 inch pipes. The other is do not place the restriction close to the turbo.

Frieberger suggested letting the turbo be the muffler and I guess just run as big a straight pipe as you can fit. The reason seems to be backpressure hurts a turbo system.

Have to take back my recall of an earlier post. pipe diameter can make a difference. I need to look back to see what system the OP plans to use. Likely be a different story with a supercharger. No easy answers I guess.

 

[engineermike]

On a turbo, exhaust restriction downstream of the turbine compounds. Turbines run at a pressure ratio, like 2/1 or 3/1. So adding 1 psi backpressure downstream of the turbine can add 2 or 3 psi upstream. This is with back pressure that's already really high vs SC or NA. Then, the additional backpressure reduces airflow into the cylinder, hurting things even more. You want the pressure downstream of the turbine to be as close to 0 psig as possible.

The PD blower is the opposite end of the spectrum where the backpressure can not possibly affect airflow rate any measurable amount. The only downside to backpressure is the pumping losses.

Centrif and NA are in the middle, as backpressure affects flow and pumping losses, just not as much as with a turbo.

The mechanisms are VERY different.

 

[robvas]

On a turbo, exhaust restriction downstream of the turbine compounds. Turbines run at a pressure ratio, like 2/1 or 3/1. So adding 1 psi backpressure downstream of the turbine can add 2 or 3 psi upstream. This is with back pressure that's already really high vs SC or NA. Then, the additional backpressure reduces airflow into the cylinder, hurting things even more. You want the pressure downstream of the turbine to be as close to 0 psig as possible.

The PD blower is the opposite end of the spectrum where the backpressure can not possibly affect airflow rate any measurable amount. The only downside to backpressure is the pumping losses.

Centrif and NA are in the middle, as backpressure affects flow and pumping losses, just not as much as with a turbo.

The mechanisms are VERY different.

Do roots and twin screw blowers behave the same?

 

[engineermike]

Do roots and twin screw blowers behave the same?

yes.

 

[illtal]

Also, on a turbo setup, the turbo itself is a restriction. The restrictions caused by the turbine housing size and turbine design plays a role on spool and needed exhaust piping diameter requirements.

This is why you see tiny turbos on Ecoboost V6s that spool very quickly and are limited on what can be made on the top end. It works for OEs because these cars aren't normally driven at high RPM.

At some point, even with an open exhaust there will be a hard stop restriction after a certain amount of flow. The turbine housing simply will not be able to flow any more amount of exhaust through the turbine housing.

To this point Garrett is the only Turbo manufacturer that maps turbine flow for their products.

I did a whole lot of research on this topic before I swapped to turbo. Sure interesting how all of it works.

 

[Hammerhead13579]

Steeda dyno'ed their 2.5" X-pipe and it gained 8whp & 9wtq peak...and at least this amount throughout the entire curve. Assuming they aren't screwing with the data this proves 2 things:

1. A convergence of the exhaust streams is beneficial
2. Eliminating the smaller (2.25") diameter tubing before and after the resonator is worth something

So let's say we do this on a car around 700whp (about +75% from factory) and go up to 2.75" or 3", wouldn't it be safe to say an X mid-pipe section would make an extra 12-14whp?

I've thought about putting this on my car and like OP it would be nice to know the expected gains from this type of modification on a boosted car.

https://longtubeheaders.com/products/ford-mustang-15-20-gt-mid-pipe

 

[Autopart101]

Steeda dyno'ed their 2.5" X-pipe and it gained 8whp & 9wtq peak...and at least this amount throughout the entire curve. Assuming they aren't screwing with the data this proves 2 things:

1. A convergence of the exhaust streams is beneficial
2. Eliminating the smaller (2.25") diameter tubing before and after the resonator is worth something

So let's say we do this on a car around 700whp (about +75% from factory) and go up to 2.75" or 3", wouldn't it be safe to say an X mid-pipe section would make an extra 12-14whp?

I've thought about putting this on my car and like OP it would be nice to know the expected gains from this type of modification on a boosted car.

https://longtubeheaders.com/products/ford-mustang-15-20-gt-mid-pipe

I made 940whp Catless LTH into stock catback with resonator deleted.

 

[Hammerhead13579]

I made 940whp Catless LTH into stock catback with resonator deleted.

I'm not sure how this is relevant to what I posted... congratulations?
Also, headers isn't stock exhaust and removing the resonator isn't stock exhaust...

 

[Autopart101]

I'm not sure how this is relevant to what I posted... congratulations?
Also, headers isn't stock exhaust and removing the resonator isn't stock exhaust...

Why don't you make changes and pay for Dyno time and answer your own question?

 

[Hammerhead13579]

Why don't you make changes and pay for Dyno time and answer your own question?

Why don't you actually contribute something useful?

 

[Autopart101]

Why don't you actually contribute something useful?

I have shared many Dyno pulls on this forum. Before after results. What have you contributed?

 

[Hammerhead13579]

I have shared many Dyno pulls on this forum. Before after results. What have you contributed?

I wasn't going to respond because you seem really daft but I couldn't resist.
First off, can you read? We are talking about stock exhaust here. Do you have stock exhaust? No? Then shut up and move on.
Did you modify your exhaust (minus your headers) after your supercharger? Do you have a dyno for this dyno man? No? Then shut up and move on.
Did you contribute anything to this thread besides boasting about your HP figure on your car with modified exhaust? No? Then shut up and move on.

If you have nothing to say that is relevant or helpful to this particular discussion on this thread then YOUR POST IS A WASTE OF SPACE. Is this simple enough for you to understand?? With your level of reading comprehension I really don't know

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