Running rich - BDD needle
Turbo Mini Forums

I will be taking my car for rolling road now it's nearly run in, after I've done an oil change with some CTV.

But, I'm wondering if i have an issue I need to sort before I go RR...

At idle I'm getting around 13 AFR and it starts and runs great. Little bit of a lean misfire when pulling away without getting the revs up a little, but I need to play around with damper springs and oil for that.

What I'm concerned about, is as soon as the car starts to come on boost, or driving up hills, the AFR goes really rich - around 10-11:1, and seems to fluctuate a lot.

I'm using a standard BDD needle, which should be a fairly lean needle to start with apparently. I also have double springs in the dashpot (which seemded to help the low rev misfire), but thinking about it - that should make it run leaner under boost, because it will stop it moving enough to use the richer end of the needle?

Which makes me think I've got a problem which I need to sort before RR? Could an air leak between carb and maniold cause this? Or maybe a badly adjusted/angled float valve? Fuel pressure was 3.5psi at idle - although I do need to recheck this. FPR was brand new.

1994 Mini Mayfair, 1330, Mspd Ph2 cam, Benross turbo head, 9:1, GT1752, TT Intercooler, MegaJolt, BMW M3 leather seats.

That AFR on boost is fine Ian, better to be on the rich side. Extra safety net.

Seems a bit rich to me! Also, seems to bog down when it goes this rich. Had boost in first gear and outs like it didn't have chance to to this rich, and it didn't bog down at all, went quite well with AFR of 12ish.

1994 Mini Mayfair, 1330, Mspd Ph2 cam, Benross turbo head, 9:1, GT1752, TT Intercooler, MegaJolt, BMW M3 leather seats.

Acceleration enrichment is controlled by the damper... try a thicker oil
13afr at idle on a bdd iirc (going back a few years in the memory) should be set to idle aroun 12.5 afr so your not far out
11 afr on boost is not drastic unless you're getting plooms of black smoke ( i usually see it around 9afr or richer than 10 as i can see 9 lol)

Also dont forget this needle is profiled tonuse the part throttle lean off pipe

What this does in the even of non part throttle
I.e snap open throttle its actually aids richness ( its lean off effect is zero )
Something to think about

Tweeking the needle and having an adjustable lean off system (bleed valve)
Refinment with this carb is endless

I used to love tweeking and dataloging

Yes i moved to the darkside

Instagram @jdm_brett

Get it on the RR. Check the needle is right at a steady load/rpms then you can try and iron out the acceleration enrichment.

Will get it RR'd but want to check I don't have other issues first. Good job I did, found small split in the servo hose which was causing my first spot at low revs.

Running much better now, no flat spot pulling away, and now back to one dashpot spring, 80/90 oil in dashpot, even reconnected the lean off pipe.

Still feels a bit flat when it starts to boost. Didn't seem to be going as rich anymlre, around 11.5-12 under boost. Might check the plug gaps are OK, almost feels like a weak spark.

What plug gap should I run with BP7s and Megajolt?

1994 Mini Mayfair, 1330, Mspd Ph2 cam, Benross turbo head, 9:1, GT1752, TT Intercooler, MegaJolt, BMW M3 leather seats.

Im sure Shaunas is on bp6's with absolutely no issues.

I ran 6's when running 1bar with no problems. If you're running a little rich it's easier to foul the colder 7's.

Phil.

WWW.TURBO-MINI.COM

I ran 6es @2 bar with water meth no problem

Yes i moved to the darkside

Instagram @jdm_brett

OK I do have a new set of 6's I'll give them a try. Went for 7's as I'm running fairly high compression.

What gap should I use?

1994 Mini Mayfair, 1330, Mspd Ph2 cam, Benross turbo head, 9:1, GT1752, TT Intercooler, MegaJolt, BMW M3 leather seats.