short flat spot when flooring the gas
Turbo Mini Forums

Has anyone made the same experience?: I have a short (maybe 0,5-1sec) leanout when flooring the gas pedal. On my wideband lambda meter I can see that the AFR goes to 15:1, then comes down to 12,5-13:1. It is just a for a very short time, and if I had not the lambda reader it would have count it to turbo lag. But as soon as the AFR goes to the 12,5-13:1 you can feel how fast the turbo spools up, so I want to get rid of this short leanout. On my n.a. engines I can see that the mixture even richens to 12:1 (for about 1 second) when flooring the gas. But on the turbo the opposite happens. What do the lambda meters speak on your turbo engines when flooring the gas? Any ideas what causes the problem? Thanks! Harry

PS: Yes, I have enough oil in the dashpot. (15W-40)

Bimmer Twinky headed and turboed A-Series:
http://www.minifreunde.at/harry/projects.htm

Have you tried blanking off the "part throttle lean out pipe" on the carb ?
Mine runs better when this is blocked, it also made a difference to a friends motor who had a similar flat spot to you.
Worth a try ......

Phil.

WWW.TURBO-MINI.COM

Almost definately this pipe...
I found that if you accelerated very slowly from cruise, you'd stay at around 14:1 even as it's gettign up to reasonable boost!
Blocking the pipe sorted it!

I blocked this pipe already. But maybe it is not 100% leakfree - I will doublecheck! So your lambda reads a short enrichment when flooring the gas?

Bimmer Twinky headed and turboed A-Series:
http://www.minifreunde.at/harry/projects.htm

Still does it even now...
It's pretty momentary - less than 0.5 seconds i think, but it is definately there...

Was really bad with the balance pipe connected though...

I just assumed it was the response of my lambda / ECU display that was giving me a bogus reading... Maybe not!!!

Edited by turbodave16v on 12th Jul, 2004.

I can see the short lean condition on the wideband AND the narrowband lambda readers. I run them parallel at the moment, because I wanted to see where the limit of the narrowband sensors is. BOTH show the same leanout! (short, but definitly there!)

Bimmer Twinky headed and turboed A-Series:
http://www.minifreunde.at/harry/projects.htm