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Detached Member
Join Date: May 2003
Location: southern California
Posts: 26,964
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Why do you get flames out of the exhaust of some PCars?
Just curious, I know its unburned fuel, is the phenomenon exclusive to turbos, or cars with radical timing. I think it happens on deceleration, is that true? Sorry, I thought I posted this in the general 911 forum, not the rebuilding forum. But if anyone has thoughts, I'd love to hear them.
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Hugh Last edited by Hugh R; 11-09-2006 at 05:56 PM.. |
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11-09-2006, 05:52 PM
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Join Date: Mar 2005
Location: Edmonds, WA
Posts: 81
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Im not quite sure of the cause, however when i hollowed out my cat, i was able to shoot a flame every time i were to shift at high revs into 3rd from 2nd. Just about a month ago i installed headers and a dansk 2in 2out muffler, havent been able to do it yet.
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-Riley .:1987 911 Carrera:. - Receiving Much Needed Love In Summer 2011 .:1993 BMW 325is:. - RIP Feb 2011 |
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11-09-2006, 08:50 PM
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The trick I believe is this...
1) You need cams with some overlap. 2) You need fuel injection that runs rich on overrun. My understanding of the mechinism is that when you suddenly close the throttles, that fuel continues to be pumped into the cylinders. Because of the throttles being closed, the speed of cumbustion is slowed down due to lack of air, even though the engine is still pumping mixture through since it is being driven by the wheels. The result is that the unburnt fuel is eventually burned in (and out the back of) the exhaust system.
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John '69 911E "It's a poor craftsman who blames their tools" -- Unknown "Any suspension -- no matter how poorly designed -- can be made to work reasonably well if you just stop it from moving." -- Colin Chapman |
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11-10-2006, 12:53 PM
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Detached Member
Join Date: May 2003
Location: southern California
Posts: 26,964
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Kind of what I thought. Thanks!
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Hugh |
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11-10-2006, 08:12 PM
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Join Date: May 2005
Location: Loxahatchee, florida
Posts: 2,894
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yes it's unburned fuel when you down shift it hits the turbo and ignites like a blow torch. really cool looking very common to turbos that have a free flowing exhaust system.
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88 turbo Guards red Targa slant nose, and yes I am a horsepower junkie, 3.4liter,7.5 to 1 JE pistons, Adjustable WUR, Imagine fuel head, 1 bar waste gate headers,allthe cis toys. Now apart to become the next EFI monster. fabbing my own intake, headers Individual throttle bodies, MS-3, pauter rods, Xtreme twin plugged heads, gt-2 evo cams cop's. 2019 Silverado 6.2L |
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11-16-2006, 01:39 AM
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resident samsquamch
Join Date: Oct 2005
Location: Cooterville, Cackalacky
Posts: 6,815
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I think this thread needs a picture of this phenomenon
 (my current desk-top):
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-jeff back in the saddle: '95 993 - just another black C2 *SOLD*: '87 930 GP White - heroin would have been a cheaper addiction... "Ladies and Gentlemen, from Boston Massachusetts, we are Morphine, at your service..." - Mark Sandman (RIP  )
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11-16-2006, 06:55 AM
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1969 Porsche 911E 2.0 E
