A/F leaning out
Turbo Mini Forums

Hi all,

I had my car on the Dyno on Saturday and as much it was and is going great the operator said he did not want to push it any more as it was leaning out a little too much for what he liked, (on 7psi it was going to 14.5 to 15:1, i raised the fuel pressure but made little to no difference, we just could not get enough fuel in and through the carb, it was using a BDD to start with and then BDG, we then cut around 1/8" off the bottom of the needle to have the needle all but out of the jet and still it was leaning out so i think it is a problem with getting fuel into the carb the pump supplies 40psi and i have it set up around 6psi at idle

i was thinking of trying the avonbar high flow seat and float bowl extention, has anyone used these at all?

or does anyone have further suggestions?

thanks

179hp on 12psi 1293cc of pure A series
14.0et @101 mph

Do you have the part throttle lean off pipe blocked off?

should only need 3.5psi on idle.

make sure you're pump isnt goosed or filters arent blocked etc.

i had the same problem and my pump was goosed.

On the Hif44 The bottom 1/4 inch is not used, at full throttle the piston sits at around station 12 (of 16) unless the spring is too heavy then it will sit even lower.

If you look at the BDD/BDG needles on http://www.mintylamb.co.uk/suneedle/ you will see that there is not much difference between them at station 12.

removing/blocking the part throttle lean off should enrichen it but even with it blocked I still need something richer than a BDD with my GT15 at 8psi

Have a look at my post on polishing needles It wont hurt to try...

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=159683

Edited by Turbo Tel on 22nd Oct, 2007.

website:- http://www.terryhunt.co.uk

just to be sure the part throttle lean off pipe is the one from the front mounting plate area to the side of the carb?

179hp on 12psi 1293cc of pure A series
14.0et @101 mph

Hi,
That's the one :)
Check the pipe for splits, common fault apperently.
Personally I can't see the part throttle lean off doing anything at full throttle.
I don't think you need the bigger needle valve until you get upto the 15psi mark....
Cheers,
Gavin :)

VEMs Authorised Installer / Re-seller. K head kits now available!

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website:- http://www.terryhunt.co.uk

ok well i have just been speaking to Graham Russel and he is not convinced it is a needle problem, i can stilll run 15psi and it goes super hard but still i can feel a surge mid to full throttle, i have not pulled the plugs to check but can the a/f meter lie if it is over fueled saying it is lean as it only measures burnt gas not unburnt????

either way i have the extension kit coming and the needle valve plus i will try the pipe trick and a leaner needle just to see how it is.

thanks guys

179hp on 12psi 1293cc of pure A series
14.0et @101 mph

This is exactly what I experienced. It went lean in fourth. Check the small fuel gauze inside the carb. Mine was clogged with grit and dirt.

Hi,
Check the above.
What are you measuring the mixture with?
Any air leaks in the exhaust before your measuring point will cause a lean reading when using a lambda sensor...
Cheers,
Gavin :)

VEMs Authorised Installer / Re-seller. K head kits now available!

WB/EGT gauges. Click here for customers write-up

Visit www.doyouneedabrain.co.uk

My Mini build diary

its a dyno dynamics dyno and it has its own wide band lambda in it which goes in my tail pipe (ouch) no exhaust leaks.

will strip it down tonight and have a look at the gauze, i remember changeing it when i averhauled it a few years back.

179hp on 12psi 1293cc of pure A series
14.0et @101 mph

Ohh..

Didnt realise that you were OK at 15psi... doesnt that eliminate gauzes etc if enough fuel can get through for 15psi then it must be Ok at 7?? But a standard BDD at 15psi?? surely you need more fuelling at that kinda boost? Hopefully you are not running 15psi without a wideband...

I think I read somewhere that if it gets so rich that its misfiring, O2 (unburned fuel AND air) can give a false lean reading but I'm buggred if I can find the reference..

Why the reluctance to polish a needle? you chopped some off the bottom of one of them!! It wont make it worse. Plus theres plenty of people out there running higher boost than 7psi without special valves and float extensions, I thought they wer eonly needed for extremely high boost.

website:- http://www.terryhunt.co.uk

yeah it can run on 15psi or more if i want to and it does not feel like it it running out of fuel more lile a lean out feeling.
I am more than happy to polish a needle and have printed off your thread on doing it, i am just covering all bases i guess, I have a range of needles so i will try them first before i mod one just to feel the different effects you know what i mean????

yes no O2 sensor fitted yet, i should do it but just have not done it.
the best needle i had results with as far as driving style goes and also the a/f ratio was was the BDG

179hp on 12psi 1293cc of pure A series
14.0et @101 mph

Please be careful...

As someone who has already taken out some pistons it scares me to imagine running 15psi without an AFR.. esp as you are already lean at 7psi...

Terry

website:- http://www.terryhunt.co.uk

yeah point taken, ok last night i put the std needle in in and blanked off the lean off pipe and it has made a big difference, prior to this i pulled my plugs out and they were not that white at all a bit dark if anything, i then fitted the BDG needle and then checked the plugs and after a quick drive they had a very white side to them flame side i guess, so i fitted the BDD back in blocked off the throttle lean off pipe and the plugs were darker back to an ok colour i think, without having a o2 sensor i cant be sure but i think it is better.

does anyone have a needle spec or a needle they have had good results with? i will start to measure mine tonight to see where i should polish it up etc.

thanks

179hp on 12psi 1293cc of pure A series
14.0et @101 mph

Grant, are you running forged pistons there? I seem to remember you talking about Omega forged...

Terry

website:- http://www.terryhunt.co.uk

yes Terry +20 Omega forged 7.6:1

do you have a thought?

179hp on 12psi 1293cc of pure A series
14.0et @101 mph

Well then thats a bloody good advert for forged pistons... I know my megas wouldnt take that!

Terry

website:- http://www.terryhunt.co.uk