Author Topic: exhaust questions regarding max performance. (Read 6199 times)

carrizog60 · « **on:** February 28, 2007, 12:29:31 pm »

hello

i have one question that i would like to be answered by using some technical info,not just a "because i think"...

in a turbocharged engine what is the best option for maximum HP?regard that no noise or legal issues are in the line,just max hp in sight

-no exhaust at all?(i see dragster use that)
-exhaust with the same diameter of the turbo manifold?
-exhaust with smaller diameter than turbo manifold?(to create some back pressure)

and what about not just max HP but also low and midrange power?
any differences?

please give me your thoughts and i would appreciate that it was complemented with some technical backup

thank you

Slave2School · « **Reply #1 on:** February 28, 2007, 03:08:34 pm »

Alex, "What is a 6" pipe through the hood?"

935racer · « **Reply #2 on:** February 28, 2007, 03:20:06 pm »

I properly fitted downpipe with a transition right off the turbine with the small end being the same size as the turbine outlet, than transitioning 1" or more from that diameter. :twisted:

carrizog60 · « **Reply #3 on:** February 28, 2007, 04:37:18 pm »

so on turbos the bigger the better?
doesent any backpressure is needed?
and why is that?

RabbitJockey · « **Reply #4 on:** February 28, 2007, 05:07:50 pm »

you don't want back pressure on a turbo charged car because for one it is completely unecessary because you want backpressure at the manifold, at the head and the actual motor, have a turbo blocking up the ehxaust supplies more than enough back pressure. so the bigger the exhaust the faster the spool the faster you get moving. the other thing is also that diesel cam shafts have no over lap, so even on na diesels the bigger the better.

SMOKEYDUB · « **Reply #5 on:** February 28, 2007, 05:57:29 pm »

Quote

Alex, "What is a 6" pipe through the hood?
Quote
I can't put a big enough smiley face. That is just mint! LMAO

carrizog60 · « **Reply #6 on:** March 01, 2007, 05:16:58 am »

didnt understand that 6" post...

veeman · « **Reply #7 on:** March 01, 2007, 08:13:54 am »

Other than the obvious overtones, I'm assuming he meant a short upturned exhaust straight up through the hood like some people do. Zero backpressure post-turbo, short run of large diameter pipe.

I've got a shot of a Mk4 Jetta drag car with the exhaust pointing right up by the windshield... Pretty wild. I doubt you'd want to run that on the street, but I believe there are a few people that are running "straight pipes" under the car without mufflers or resonators.

carrizog60 · « **Reply #8 on:** March 01, 2007, 09:29:23 am »

but dont we need some king of backpressure for the best results?

and what is the size of stock 1.6 td exhaust?

veeman · « **Reply #9 on:** March 01, 2007, 09:36:19 am »

Just as Trev0bor said...

"you don't want back pressure on a turbo charged car because for one it is completely unecessary because you want backpressure at the manifold, at the head and the actual motor, have a turbo blocking up the ehxaust supplies more than enough back pressure"

So...in effect, the turbo supplies the backpressure needed to prevent reversion, etc. After the turbo, the exhaust can be as free as possible.

Quote

what is the size of stock 1.6 td exhaust?

On my mk1 TD, the exhaust was probably 1.75" or so at the downpipe. Probably some metric size. Now I've got a 2.5" downpipe and exhaust from the turbo back. Fits fine and isn't loud. I'm running a Giles pump and 20 psi and I can tell you that the thing runs great.

BlackTieTD · « **Reply #10 on:** March 01, 2007, 09:37:02 am »

Quote from: carrizog60

but dont we need some king of backpressure for the best results?

yes. backpressure is provided by the turbo.

Quote from: carrizog60

and what is the size of stock 1.6 td exhaust?

IIRC its around 1.5" but not exactly 1.5" as i think it was spec'd in metric.

dieselsnowmobile · « **Reply #11 on:** March 01, 2007, 02:23:20 pm »

This is what a 6" pipe through the hood is.

BruceM31 · « **Reply #12 on:** March 01, 2007, 02:51:38 pm »

that is a very inspiring image!!! lmao!

mtnbob · « **Reply #13 on:** March 01, 2007, 04:23:23 pm »

LOL :lol:

carrizog60 · « **Reply #14 on:** March 01, 2007, 04:34:00 pm »

:lol:

new giles monster pump? :lol:

Author Topic: exhaust questions regarding max performance. (Read 6199 times)

935racer