Lean on Part Throttle
Turbo Mini Forums

Looking for some help with a fuelling problem I've got.

1275 low compression unit running a garrett T3 metro turbo at 7psi with a HIF turbo carb. The cars been setup on a dyno but still isn't running right. Before it went on the dyno it would run very lean, 16-17 on my AFR gauge on boost and on part throttle it would go off the gauge to 22 and cut out completely a few times. This was traced to a faulty fuel pressure regulator and now it runs at around 12 on boost but still lean off boost on part throttle! With part throttle (around 30% id say) it sits anywhere between 14-19 if you move from part throttle to 50% or full throttle to fast it will lean out and go off the gauge. My though is it may need a different dashpot spring or needle? Has anyone got any ideas? im new to turbo minis and carbs in general so though I would ask!

Cheers for any ideas!

What oil does it have in the damper?
Do you have the part throttle lean off pipe connected?
Which spring and needle do you have fitted?

In the 13's at last!.. Just

its got 3 in 1 oil in the dashpot
Part throttle lean off pipe is disconnected and blocked off
I dont know what spring its got in it, guessing its the standard HIF turbo carb spring what ever that was? I believe its a DDB needle in there at the moment.

Interested to find out if there is anyone out there with a similar setup and what spring they are running?

Cheers!

generally thicker oil makes it richer as it comes on boost or hen you open the throttle, essentially the more the damper holds the venturi shut the faster the air travels through it and the greater suction on the jet, Bernoullis Principle.

std oil grade would be 20/50,

Edited by Joe C on 12th Aug, 2019.