Biiiiiig flameout. Is this good.
Biiiiiig flameout. Is this good.
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Discussion

charge

Original Poster:

561 posts

265 months

Wednesday 14th August 2013
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Had a brisk run home last night from fellow beards and jumpers meeting at Essex PCGB last night, and after a bit of 'sustained' acceleration, had the road light up behind me between gear changes, then a big prolonged burn on the overun. Never had this last month, but had a full from scratch re-map at Owen Developments due to drivability issues at cruising throttle.
Does this mean it is too rich, or just unburnt fuel on throttle shutdown, ignition back off?
I see this stuff going on at Le-man with the GT2 993's back in the late '90's, but should this be happening on a road car?
I calmed down considerably when I encountered a fully tooled up battenberg 5 series, but got me thinking, would it warrant a tug if they spotted flame ( obviously would with a proper bit of acceleration!)?

JamieG

911 posts

254 months

Wednesday 14th August 2013
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Good man - sounds awesome!!! Can't help on the technical side just disappointed I didn't get to the meet this month to see the beast!

drpep

1,761 posts

197 months

Wednesday 14th August 2013
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That sounds fking awesome. As long as its not damaging the car, I'd love to have a fire-spitting dragon!

charge

Original Poster:

561 posts

265 months

Wednesday 14th August 2013
quotequote all
Hey JamieG.
We will have to meet up next time.
Often get there if the weather if good and there are no speakers trying to sell polish/ wheels/ ICE.
Just like to mill around the cars and chat to the guys, sink a beer and hopefully have a good run home!

Rockster

1,515 posts

189 months

Wednesday 14th August 2013
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No. Not good. And a sign the custom tune/flash needs tweaking. At least

The excess fuel being burned means unburned fuel passed through the combustion chambers. Well, most of it. Some gets on the cylinder walls and this washes away oil and dilutes the oil. Both of these are bad.

I'd advise you to get this sorted out sooner rather than later.

911p

2,361 posts

209 months

Thursday 15th August 2013
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If you have cats they'll get destroyed by running that rich as well.

Beautiful car though!

charge

Original Poster:

561 posts

265 months

Thursday 15th August 2013
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No cats, so no bother there.
I was thinking, maybe it is just all the air and fuel on boost, that sudenly shuts down between say, gear changes which fills the exhaust with a surpless of unburn fuel. I mean you see racers doing it, with the might of Porsche motorsport behind them in endurance racing. And I am sure they would not have fuel washing the bores out on them?
Also, how does the long arm of the law veiw such stuff. It is odd that it never happened before the re-map, and the two lambdas read much richer running than they do now, and economy is much improved.
It just dont make sence.

996TT02

3,342 posts

169 months

Thursday 15th August 2013
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My understanding is that this is to do with ignition timing rather than excess fuel.

Effectively on the ovverrun ignition is too late resulting in exhaust valve already open by the time the mixture is burning, so some of it burns in the exhaust system rather than in the cylinder.


Jim1556

1,838 posts

185 months

Thursday 15th August 2013
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Either way, for the miniscule cost of wasted fuel, it looks awesome!

Case in point:



Though I'm sure most prefer this:


johnycarrera

1,935 posts

259 months

Thursday 15th August 2013
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Don't think it's a big deal unless you want the engine to do 100,000 miles.
The race cars have their engines rebuilt regularly.
Ask the guy who mapped it what the problems could be, would think it would only petrol wash the bores if there was a fueling issue, however you've just got a little excess burning off on the hot exhaust........

Nice

egbert

449 posts

250 months

Thursday 15th August 2013
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Perfectly normal for a tuned engine with no cats, notch up some man points whenever it happens.

anonymous-user

83 months

Friday 16th August 2013
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Rockster said:
No. Not good. And a sign the custom tune/flash needs tweaking. At least

The excess fuel being burned means unburned fuel passed through the combustion chambers. Well, most of it. Some gets on the cylinder walls and this washes away oil and dilutes the oil. Both of these are bad.

I'd advise you to get this sorted out sooner rather than later.
I doubt that.

Unburned fuel is in the chamber for 2 out of every 4 strokes, in any case.

charge

Original Poster:

561 posts

265 months

Friday 16th August 2013
quotequote all
egbert said:
Perfectly normal for a tuned engine with no cats, notch up some man points whenever it happens.
Need some man points this week! Had a guy round to fix my aircon, and he was like Mungo out of Blazing Saddles!

Made me feel like this