Lean on light throttle

dburone · Dec 29th, 2005, 09:33 PM

My actual turbo setup reaches a good mixture when on boost, but when im going soft on the gas, around 1500 to 2000 rpm with around -10 to -5 PSI of vacuum, the mixxture gets lean, very lean, but is it dangerous on these conditions?
I guess not. as soon as i step on it or boost raises above -5psi, mixture gets around 13:1.
Thanks

velardejose · Dec 30th, 2005, 12:26 PM

Hi
Its because its a carbed turbo

It lacks vac signal at the venturi to pull gas at low revs
You could try using a smaller diam venturi so the main circuit starts earlier

velardejose · Dec 30th, 2005, 12:28 PM

Btw, I had a similar condition...
I managed to cure it using a bigger idle gas jet so the mixture gets richer via transition circuit

**wes** · Dec 30th, 2005, 12:51 PM

on EFI Nissan's the ECU maintains a 14:1 ratio @ idle. Sounds like yours is normal. 13:1 under boost is lean though, I would try for high 11's for longevity.

dburone · Dec 30th, 2005, 04:03 PM

Im going to try what velardejose says.
I know that ideal AFR on boost is 12, bot with a carburator it isn easy at all to get the ratios you want at different stages of boost.
ill try that and tell you what happens.
Thanks!!

velardejose · Jan 13th, 2006, 03:48 PM

Hi
Any news?