Measuring stock exhaust restriction - Page 3 - 3000GT/Stealth International Message Center

FWombat · 09-19-2005, 08:30 PM

Here are a couple of pictures of the new exhaust used in the second half of the testing:

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mjannusch · 09-19-2005, 09:04 PM

It'll work better at speed if the tip points straight back. With it angled out like that it is pushing exhaust out right into the main airflow around the car. Neither good for exhaust efficiency, nor overall aerodynamics.

Multiades · 09-19-2005, 09:06 PM

Quote:

Originally Posted by mjannusch

It'll work better at speed if the tip points straight back. With it angled out like that it is pushing exhaust out right into the main airflow around the car. Neither good for exhaust efficiency, nor overall aerodynamics.

It most likely has a lower impact on either than another bend would. I bet it fills into the low pressure zone at the bumper pretty well (just only on the left side).

FWombat · 09-19-2005, 09:18 PM

The tip definitely doesn't extend past the bumper, so I doubt there is any aero penalty for the overall chassis. As for the exhaust pushing into high pressure...I dunno. There's probably some truth to that, but I'm not sure it's more than the flow losses from an additional bend...

doctorstupid · 09-20-2005, 02:03 AM

Quote:

Originally Posted by mjannusch

It'll work better at speed if the tip points straight back. With it angled out like that it is pushing exhaust out right into the main airflow around the car. Neither good for exhaust efficiency, nor overall aerodynamics.

What about Bernouli's principle? Shouldn't the air rushing past the tip more perpendicularly (that's a word, right?) help pull it out? I always thought that was the idea behind these angled exhausts everyone has.

VR-4ever · 09-20-2005, 06:34 AM

The angled style exhausts pay homage to the supra. It was neccessary on that car with a big exhaust I.D. to clear the axle with the least restriction.

Now... about the airflow thing... your exhaust gases are under more pressure than the air around it, so you could point the damn thing anywhere and be fine. I believe the way you have yours setup is sufficient.

If you want to do something about airflow, install a diffuser.

But that's another project......

mjannusch · 09-20-2005, 06:42 AM

Quote:

Originally Posted by VR-4ever

Now... about the airflow thing... your exhaust gases are under more pressure than the air around it, so you could point the damn thing anywhere and be fine. I believe the way you have yours setup is sufficient.

Sufficient - yes. Optimal - no.

I'm sure it'll be fine, but if you are trying to extract maximum efficiency, it really should exit straight back.

FWombat · 09-20-2005, 09:22 AM

Quote:

Originally Posted by VR-4ever

The angled style exhausts pay homage to the supra.

I'm not paying homage to any damn Supra; I'm just trying to make the straightest exhaust I can without cutting the bumper.

Multiades · 09-20-2005, 10:30 AM

Quote:

Originally Posted by FWombat

I'm not paying homage to any damn Supra; I'm just trying to make the straightest exhaust I can without cutting the bumper.

Right, which is exactly what they were doing (but probably 10 years ago).

Some of it *might* come from the need to do that with large piping, but I bet most of the reason they do it is becasue fewer bends = less flow losses.

VR-4ever · 09-20-2005, 11:10 AM

^Thank you.

I wasn't saying you were going for that look at all.... just replying to Chris.

09-19-2005, 08:30 PM	#21 (permalink)
FWombat AEM Veteran Join Date: Jul 2001 Location: Tacoma, WA Drives: '94 VR-4 Trader Rating: (14)	Re: Measuring stock exhaust restriction Here are a couple of pictures of the new exhaust used in the second half of the testing: __________________ Brian Geddes '94 Danube Blue VR-4 Replacing everything that moves. '94 Pearl Yellow VR-4 It's dead, but its drivetrain lives on!

09-19-2005, 09:04 PM	#22 (permalink)
mjannusch Pro xfercase destroyer Join Date: Feb 2001 Location: Hudson, WI Drives: 2005 Toyota Prius Trader Rating: (15)	Re: Measuring stock exhaust restriction It'll work better at speed if the tip points straight back. With it angled out like that it is pushing exhaust out right into the main airflow around the car. Neither good for exhaust efficiency, nor overall aerodynamics. __________________ -Matt '95 3000GT Spyder VR4 (11.838@117.56) '91 3000GT VR4 (Project for 2008)

09-19-2005, 09:18 PM	#24 (permalink)
FWombat AEM Veteran Join Date: Jul 2001 Location: Tacoma, WA Drives: '94 VR-4 Trader Rating: (14)	Re: Measuring stock exhaust restriction The tip definitely doesn't extend past the bumper, so I doubt there is any aero penalty for the overall chassis. As for the exhaust pushing into high pressure...I dunno. There's probably some truth to that, but I'm not sure it's more than the flow losses from an additional bend...

09-20-2005, 06:34 AM	#26 (permalink)
VR-4ever The silver car. Join Date: May 2002 Location: Virginia Beach, VA. Trader Rating: (11)	Re: Measuring stock exhaust restriction The angled style exhausts pay homage to the supra. It was neccessary on that car with a big exhaust I.D. to clear the axle with the least restriction. Now... about the airflow thing... your exhaust gases are under more pressure than the air around it, so you could point the damn thing anywhere and be fine. I believe the way you have yours setup is sufficient. If you want to do something about airflow, install a diffuser. But that's another project...... __________________ FOR SALE: 6 speed transmission - $700, 6 speed transfer case - $350, 6 speed intermediate shaft - $50. 513 AWHP at 17psi/93oct. Ride Of The Year '05. Best of show, East Coast Gathering '07. Best all around 3000GT/Stealth, National Gathering '07. Modified Magazine, June '08.

09-20-2005, 11:10 AM	#30 (permalink)
VR-4ever The silver car. Join Date: May 2002 Location: Virginia Beach, VA. Trader Rating: (11)	Re: Measuring stock exhaust restriction ^Thank you. I wasn't saying you were going for that look at all.... just replying to Chris.

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