rich idle?
Turbo Mini Forums

Maybe yins all can give some pointers.

I have a turbocharged midget that runs pretty good.

Here is my problem. My idle is pig rich and I can't lean it out.

I have a single hif4 carb(rebuilt). static fuel pressure is set at 2.5 psi. Has abd needle and 2 intertwined red springs(single spring is to light). 20-50 dashpot oil. timing is currently set at 10 degrees BTC at idle.
I have adjusted the carb by the book. runs good and Idles smooth. My wideband reads 10.5-11 to 1 at idle. If I raise the jet to lean things out(13-14 to 1 ratio) and lift the lifting pin, the motor dies.
When idling at 10.5-11 to 1 and I lift the lifting pin, engine responds normally.
the spark plugs are a little sooty but not terrible.
Any suggestions

adjust the idle mix so that when you lift the pin a couple of mm ,the revs slightly rise then it drops back to normal idle speed , whats the mixture then ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

what WB is it?

are you redig the WB directly or is it going via an ECU where the calibration could be off?

When jet is adjusted so that when I lift the pin, the rpm rise slightly and fall to normal, my far is about 11-1

Aem failsafe gauge reading direct.

When cruising or accelerating(boosted) afr are good, but at idle goes rich

earth offset joe ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

yep, thats what I was thinking, also Ive seen the gauge output incorrectly set if its changable, and likewise for the ecu input. and lets not forget the LC1 self calibration thingie.

But th AEM is nice and plug and play so ignore this!

Every engine build is different but A-series do seem to prefer to idle rich.
Mine idles best around 12.5 - if I push it any higher towards the magical 14.7 it's just crap (and being EFI I can put it anywhere I want with a click of a mouse).
Unless the plugs are actually fouling, I'd leave it where the best setting of the jet is for idle and only be concerned over what you see under load/boost (which you say is OK).
That's assuming the calibration and ground wiring are all OK so you know you have a genuine reading.

Schrödinger's cat - so which one am I ???

also ive found idle better up around 15 degrees advance, but you may not have the luxury of moving it.

often the dizzys were set at 8-10 degree with out the vac advance, and once connected th vac would pull the idle advance up a bit.

What's your compression ratio ? If it's low it will require more advance at idle, as Joe suggested. Mine was set to 16deg iirc. If you're running an ECU this is a simple enough job to do, if you're on a dizzy then it's more of an issue unless you adjust it, then limit the total advance.

Phil.

WWW.TURBO-MINI.COM

Timing is set at 15 degrees.

I did an experiment in the driveway today. When fully warmed up and idling, I disconnected the fuel pump power.
I expected the afr ratio to climb before engine quit.
afr stayed right at 10.5 to 1 until it stalled out.
weird.

mmm, thats not altogether supprising, it should give the same mixture right up until the flowt bow emptys and it sucks air, but i would expect a bit of stumbling etc before it died.


if your sensor is easy to get at could try pulling it and sticking somthing like a gas soldering over the sensor, this can give a pretty good stoic reading of 14-15:1