high afr on cruise
Turbo Mini Forums

just want to check others opinions here...

basically afr is about 14.5 -15 cruise in the summer in my turbo mini. full throttle/boost afr is usually between 10-12

I took it for a spin a few weeks ago (ambient temp about 8 degrees), cruise afr was over 15, sometimes 16 under more load ie cruise up hill. the engine isn't too happy running like this, misfiring/running rough. though its fine on full throttle and idle

full throttle its about 12

what do people think here? is the low intake temp likely to be leaning it out. obviously the initial charge is cooler, but then its intercooled, I have decent air flow over the ic

I have thought about cleaning/renewing the plugs, is there anything else that I could do to improve this?

cheers, dan

16 afr on the motorway should still be fine but under any load you want to be the other side of stoich imo 14afr or richer

on all my road engines i have given them maybe 1/2 turn richer on the carb through the winter
it will be down to ambient air temp

Yes i moved to the darkside

Instagram @jdm_brett

I run around 16.8 to 17.5 to 1 on cruise , you need a powerful spark ,and have to run the plugs around 1.1mm , which is a bit big for high boost .

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

I will agree with the others, it is purely down to the cold temp.
The carb can only sense the difference in pressure between the plenum and air in the carb, which is independent of air density, so will naturally run a bit leaner when the air is colder/ more dense, but I wouldn't have expected it to make much difference really.
Could also be to do with the fuel condensing due to the cold and not burning as well, but unlikely in a boosted engine.

this dose not apply to you much but ive not used the aem afr with the mini yet but on my hilux ute
im running about 16 17 idle/cruse at any sign of load it moves from idle jet to the main witch is set for 14-15 and if u open the secondary its set for 13 smack on these numbers all get slightly richer with more rpm due to how ive set the air correction jets
ive fixed my wandering readings it turned out to be a badly worn dissy/timing chain both flapping in the breeze..

this is using the 32/36 DGV carb on a 2000cc 8 port reverse flow head engine with 270,000kms

have you got the water heated type mani? if so try plumming it up so the flow comes from the head to the mani then to the heater then reterened to the lower hose
this way when its cold u want ur heater on both for you in the cab and ur mini gets a worm blanket too..

cheers for the replies. I only use the car in the summer, it was just a late run in it as I had a broken foot for part of the summer so didn't get much use out of the car

if I remember rightly on the way to retro rides in the summer it was leaning out ever so lightly off boost on the big hills there. maybe half a turn richer wouldn't hurt it anyway?

1.1mm gaps, isn't that huge? I think cleaning the plugs might help. how does opening the gap up improve things? is this because the gap is larger so must the spark be to breach the gap?

the inlet isn't plumbed in, I don't plan on plumbing it in either. cant risk losing power by warming the inlet charge!! though I see that this would benefit things if routinely running the car in cold weather

cheers again, dan

I have taken Roberts line and run up to 16:1 on cruise (even leaner when just whiffling along in top, in traffic -which is not very often to be fair !)
Drops to 12:1 as soon as I floor it

cheers dave (and Robert), I might give this a go. cant see me being out in it before spring now but will look at sorting this for when its next on the road

cheers, dan

Robert, or anyone else who may be able to help...

how does opening up the plug gap work, how will this improve off boost lean running?

what might the implications of this be when running max load and high boost?

I plan to do this soon, not had any free time to work on the car. would be good if someone could explain the above to me

cheers, dan

it makes it possible to ignite a leaner mix , since the spark is bigger because it has to jump a bigger gap .

high boost can create enough cyl pressure to make it too hard for a big gap to spark so it missfires .

when I mapped(hacked chunks off his needle), david (tadges) car, I set it a little richer since he is not running a msd cdi ignition like I am , which drastically increases spark energy.

Edited by robert on 26th Dec, 2013.

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

thanks so much for the reply Robert, its very much appreciated.

I currently run just std megajolt ignition. not sure what the spark size/strength is on this in standard form? I will try opening the plug gaps up a bit. am going to try to squeeze in a larger/more efficient intercooler soon, so will need to get it over the rollers again for a tune up. this intercooler will possibly make it run even leaner. my compression ratio is low! (circa 8:1), currently only running 13psi, I hope to up this to around 18. im thinking that maybe I should try the gaps at around 1mm?

yes give it a try .

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

cheers, I will do. I will take it for a test run in the next week, weather permitting

cheers, dan

The standard plug gap for the ford ignition system i.e. what your using with the Megajolt is 1mm and is what you should be using anyway.

Cant remember what I set them at before, however they were smaller than 1 mm

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as above i have had the same issues with some motors and overcome this on the odd engine by setting the plugs to 0.025"

Cheers gents. The gaps have been reset to 1mm, going to test it soon, if it ever stops raining!