Turbo Exhaust Theory

[blk94r33]

Good on you for striving to do your own research/experimentation to satisfy yourself that you've done it right - there IS a lot of BS and misunderstanding on the internet and its self propegating, I wish I worked out way earlier that even a lot of the more clued up seeming (and sometimes actually are mostly switched on) people have holes in their understanding of things, no one can have all the answers. A lot of the time given explanations for a rule of thumb which is correct are wrong in terms of reasons, and thats where things can go awry.

Having said that, all things being equal (no compromising bends, equivalent mufflers etc) I am absolutely sure that going to a 3" or bigger exhaust will cost you nothing anywhere versus a 2.5" system on your car. Any loss in torque anyone has experienced with a turbo car as a result of changing exhaust would more likely be tune related, or some other issue - especially if the airflow (in an airflow metered car) reaches levels which there is overly safe mapping for in that particular instance.

Bare in mind when changing a cars setup that there are always all sorts of variables at play, don't always assume that the most obvious thing (or the first thing you think of) is actually the cause of the final outcome.

Not %100 if that was sarcasm or not? But if not, cheers.

And yes, I'm happy to do my own research, at the risk of someone elses' pride and a few dollars out of my pocket, more than likely, i'll end up with a 3" exhaust at some point, and more than likely, make more power, for now I am keen to see what the 2.5" system can handle, and what happens on a fair/comparative dyno run when it's dropped. If it makes 11ty more killer-wasps, then 3" piping it is, an my exhaust guy gets proven wrong...

[BrOwnY GT]

Not %100 if that was sarcasm or not? But if not, cheers.

And yes, I'm happy to do my own research, at the risk of someone elses' pride and a few dollars out of my pocket, more than likely, i'll end up with a 3" exhaust at some point, and more than likely, make more power, for now I am keen to see what the 2.5" system can handle, and what happens on a fair/comparative dyno run when it's dropped. If it makes 11ty more killer-wasps, then 3" piping it is, an my exhaust guy gets proven wrong...

Make sure you update us with the 2.5" dyno sheet be neat to compare with the 3"inch one .. assuming you're vehicle is fairly stock

[Lithium]

Not %100 if that was sarcasm or not? But if not, cheers.

And yes, I'm happy to do my own research, at the risk of someone elses' pride and a few dollars out of my pocket, more than likely, i'll end up with a 3" exhaust at some point, and more than likely, make more power, for now I am keen to see what the 2.5" system can handle, and what happens on a fair/comparative dyno run when it's dropped. If it makes 11ty more killer-wasps, then 3" piping it is, an my exhaust guy gets proven wrong...

Wasn't sarcasm at all - see here: http://www.typology.net/quotes/maria.html

Forums are full of people who think they know more than they do and sitting on people who may actually be heading in a good direction, even if in a round-about way.

[ARTZ]

2:5 inch will be fine to 200kw.. Probably a bit more

But i still adivse you get the 3 inch bellmouth dump as this will make alot more of a difference than the whole exhaust..

Btw mine will be for sale shortly (hint hint ) 100$ delivered..

So is my turbo that made 222rwkw at 14psi...if ya interested...lol

[R31Nismoid]

250hp at the engine is only roughly 150rwkw. That is what a standard RB25DET makes.

A normal setup with a few mods is around 190rwkw so as said by Arthur thats around 300hp at the engine.

190rwkw is a LOT more than 300hp

300hp = 223kw

There is no way you are only losing 30kw to the drivetrain

Id say closer to 340-350hp @ 200rwkw would be much closer to the mark. So yes, 2.5" is going to be too small and I would not be surprised if there is gains noticed if someone went from 2.5" --> 3" with 200rwkw.

Might only be 5-10rwkw in the top end, but the midrange might see gains as would on/off throttle etc.

**Although** that includes having a nice dump pipe as well. If the dump/front area is only 2.5" then dropping the exhaust from the CAT - might not show up the actual difference. It's still being choked from the outset etc.

Either way 3" should have been chosen.

[eron]

Now, full 2.5" vs 3" is a lot more understandable.

What about:

Full 3", including 3" exhaust tip,

Versus

Full 3", with 6" exhaust tip.

We know 6" exhaust tip will be louder. But what about power along all the RPM?

Edited June 29, 2011 by eron

[wolverine]

We know 6" exhaust tip will be louder.

Really?

[R31Nismoid]

Now, full 2.5" vs 3" is a lot more understandable.

What about:

Full 3", including 3" exhaust tip,

Versus

Full 3", with 6" exhaust tip.

We know 6" exhaust tip will be louder. But what about power along all the RPM?

The tip have sweet FA to do with it.

A tip any larger than the exhaust itself = noise. There is no performance benefit.

[blk94r33]

2:5 inch will be fine to 200kw.. Probably a bit more

But i still adivse you get the 3 inch bellmouth dump as this will make alot more of a difference than the whole exhaust..

Btw mine will be for sale shortly (hint hint ) 100$ delivered..

So is my turbo that made 222rwkw at 14psi...if ya interested...lol

Lol, nice plug,,,

DE+T, stock ECU and intercooler, for now, 14psi is a bit down the track...

Car has become some sort of animal, boost comes in alot harder, 300rpm sooner, and holds all the way through, the VCT is very noticeable. 5psi by 2200rpm is very, "streetable"...

Just have to get the car on a dyno, and see what difference dropping the exhaust at the cat makes, if none, then i'll try a 3" dump/front, and then drop the exhaust again and see how things go...