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Black smoke under load

Lemon

Lemon

Member
Hi

My car has occasionally let off a little puff of black smoke under load, but recently has become suddenly worse.

PSH mentioned after I pulled out at the rolling road day last month on the Wirral.

Now it looks like I am running very rich initially from the Dyno sheets, but before I start looking at new head and valves, could it be something else. I appreciate the car has now done 138,000 miles so may be needing it, but to suddenly get worse suggests it could be something else making it worse than it need be.

Could it be a crankcase breather or turbo oil seal? Boost leak? Running rich too? Cycling valve?

It does not appear to be using anymore oil than usual, but uses the usual amount a Turbo that has been driven as it should uses [:D]

Any help as where to start looking appreciated.

Lee
 
Id be looking at ignition first, because you dont seem to be burning all of the fuel. If thats as it should be then Id be looking at the fuel system, because it would appear that too much is being delivered for the air ingested.
 
Thanks for that 944 man.

I have included a recent Dyno graph of my Boost and AFR.

Runs very rich to start and then goes lean on boost.

Someone suggested my air fuel meter may be not working as it should?

Any other thoughts

CD0CEE814EC742F194D1C25FA72A05E9.jpg
 
the graph doesn't suggest you have a boost leak. What are the mods you have made to the car? - FPR? chips?
 
ORIGINAL: edh

the graph doesn't suggest you have a boost leak. What are the mods you have made to the car? - FPR? chips?
Click to expand...

Promax Level 2 kit. So Chips, Uprated 3 bar fuel regulator, DPW and MBC.
 
OK - what condition are plugs, dizzy etc.. in? - what colour are the plugs & are they gapped correctly? maybe you just have a poor spark?

From what you said, this is a problem on WOT, so I don't think the AFM plays a big part.

 
Thinking about it, you may be losing a bit of boost (although nothing major) I haven't studied many charts with an MBC and DPW, but maybe the boost shouldn't drop off? - mine will hold 15psi all the way now. It used to look more like that when I had the LBE fitted. But a boost leak would make it go richer at the top end, so it's not the primary cause here.

 
Hi Lee

White smoke is oil, black smoke is unburnt fuel so as Peter says it looks like combustion problem - AFM? - sticking injector?

Mike
 
That Dyno sheet is not far off where you want to be, but if it's suddenly got a lot worse then I would suspect maybe your FPR is suddenly delivering too much fuel. How old and what are the state of your plugs? If they are not providing a healthy spark it could be leaving some fuel unburnt before the exhaust valves open

John at Vitesse told me that ideally you want to be around 14:1 when cruising around off boost, 12.5:1 up until the boost hits 7psi (0.5bar), and anything higher than 7psi should be 11.5:1

Your graph from last month is slightly lean until 3500rpm, then ever so slightly rich from 4000-4500rpm and then it goes lean again climbing to over 12:1 by the redline. It's always within 0.5 or 1 of where it should be so it's not dangerous and probably about as close as an off the shelf map can be.

However if it's changed drastically then summat is up [&o]
 
Hi guys

Thanks for the comments and help so far, will do a little more investigation re plugs, dizzy etc.

Going to have an interim oil service at Tech 9 in the next few weeks, so will also let them have a little look aswell.

Cheers
Lee
 
With that setup you should be getting around 300hp? I have a non S model with the lvl 2 kit producing 275hp. Unless the hp figure on the afr/boost graph is not the actual one.
 
Lee, just need to get a 'Beetle' as rumour has it, they put out more power on the rollers than 944 turbos anyway......![;)]

Runs and hides[:D]
 
ORIGINAL: barks944

With that setup you should be getting around 300hp? I have a non S model with the lvl 2 kit producing 275hp. Unless the hp figure on the afr/boost graph is not the actual one.
Click to expand...

Could be wheel hp not flywheel - suggesting around 270 flywheel?

Dynos vary in their results, so I wouldn't read too much into that. My 250 turbo made 285 HP on the Weltmeister dyno (same one yours was measured on I think) at 11psi with an LBE - would expect a bit more holding 15psi now with MBC and MAF.
 
ORIGINAL: barks944

With that setup you should be getting around 300hp? I have a non S model with the lvl 2 kit producing 275hp. Unless the hp figure on the afr/boost graph is not the actual one.
Click to expand...

Hi

Yes you are right it should be making 300bhp at the flywheel. The figure on the chart was wheel horse power.
It made 270bhp on the day at the flywheel, still 20 or 30 down on where it should be which is why I am trying to diagnose a few problems now.

Cheers for input

Lee
 
Are those Pro Max 951 chips old Guru Racing ones as they used to be? I would test with original chips & 2,5 bar fuel pressure regulator to see what happens.
 
some guesses,

Temp sensor might have failed so the engine thinks its cold.

tracks on AFM - see http://www.the944.com/ airflow meter.

Weak AFM spring - not supposed to be adjusted but I played with mine a bit with some success.

Boost leak.

good luck,
Tony
 

ORIGINAL: appletonn

Lee, just need to get a 'Beetle' as rumour has it, they put out more power on the rollers than 944 turbos anyway......![;)]

Runs and hides[:D]
Click to expand...

What even more than rusty smoky ones with c200k miles on the original bottom end? [:)]
 
ORIGINAL: 944Turbo

some guesses,

Temp sensor might have failed so the engine thinks its cold.

tracks on AFM - see http://www.the944.com/ airflow meter.

Weak AFM spring - not supposed to be adjusted but I played with mine a bit with some success.

Boost leak.

good luck,
Tony
Click to expand...

Thanks for that Tony.

Will do some more digging see what I can find

Lee
 
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