Running lean @low RPM
Turbo Mini Forums

When I push de pedal from low RPM (from 1000 to 3000) the engine leans out.. I don't have this problem when I push the pedal slowly.. I thought it was the carb oil, but the oil is fine (tried several oils). Before I'm going to adjust the needle; does anyone have an idea/solution for this problem? On the street it's terrible to drive in combination with a grey diaphragm and paddle plate. Above 3500 everything is fine.. @cruising speed AFR is around 14.

Specs; Hiff44, T3, Phase 2 cam, MJ ignition, standard turbo pressure regulator.

Welcome... i recolgnise you n the mini from a youthbe vid?

Stronger spring in the carb?

I run a supercharger and I don't care the TB is on the wrong side.
VEMS + 12 PSI + Liquid Intercooler = Small Bore FUN!

Thanks Dave! This one? https://www.youtube.com/watch?v=hUY6QsDFlZk

A stonger spring will make the whole RPM range more rich, isn't it? I'm using the green one..

spring or dashpot oil would be first port of call

The resistance of the dashpot going upwards to allow more air in, is effectively what creates acceleration enrichment as airspeed is forced to increase through a smaller gap pulling more fuel from the needle/jet area.

Of course that isnt to say a different needle profile or jet height may not be needed too.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

I'd definately try a stronger spring. If you don't have one you can double up two standard ones as an experiment.

Phil.

WWW.TURBO-MINI.COM

I"ll try 2 springs tomorrow and let you know the results!

Tried a standard and green spring together.. Same problem; look @ https://www.youtube.com/watch?v=dhqb1SluV4o

Any other ideas?

Not quite following the problem ?

You're not even on the throttle, very low load, no boost....and there is only a very very brief period you could call lean ?

But it doesnt look to be affecting how it drives at all ?

I'm not really seeing a problem ? Is it whatever you're describing affecting how it drives ?

And if you believe there is a problem....what has changed from when it last ran good until now ? Or has it always been like this ?

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

Part throttle lean off pipe fitted?

Interesting!
I have a similar issue when i am cruising off boost with part throttle. The afr is hovering around 14.5 -15.5 and the car starts hesitating slightly which is annoying when cruising in traffic but once boost comes in the fueling is spot on around 11.5.
Do you think the thicker oil will help in my case?
Cheers

Sounds like the same problem Burcy! At cruising speed AFR is fine (rich), but when I push the throttle it start spitting a little (no backfires or something like that) and AFR 15 - 19.
@Stevieturbo; when the revs rise the mixture become more rich. There really is something wrong.. It feels like driving an engine with a very lumpy cam..

Removed the double springs and placed the green one back in the dashpot. Dashpot is moving well.. Yesterday, in combination with the double springs, I used a thin oil, so I tried a 20W50 today.. same problem exists.. Blanked of the lean off pipe, same problem..

Look at this; https://www.youtube.com/watch?v=QzBfhOTB4iI
This isn't not quite normal as well..

Burcy. It's sounds like your fueling is spot on.

In the 13's at last!.. Just

Your right it is set up really well to be honest, maybe it's me just being a bit picky with it being lumpy off boost.
A good thrashing at Blyton this weekend may cure it 😃

for the hesitation it could need a set of plugs, maybe try the next warmer set.

Yes i moved to the darkside

Instagram @jdm_brett

Roland imo you looking at it the wrong way round imo if its too lean at part throttle / low throttle and even idle then you need to move the base mixture

12lb+ spring and 20w40 ish in the dashpot on a standard metro turbo needle the fueling off boost on that needle is very very good

Yes i moved to the darkside

Instagram @jdm_brett

Cheers fellas,
I have ordered some bpr6es and bpr7es plugs. I run a mega jolt so no need for a more powerful coil . I have had problems with plugs in the past when things have got too rich.

The symptoms do sound like the dashpot is moving upwards too quickly. You mention the dashpot is moving well - is there resistance to the piston moving upwards? I'd say to check you haven't blocked the port to the float chamber with the plenum gasket, but with it leaning out so much just revving the engine it is likely to be something else causing it.

I find something similar, opening the throttle sharp tends to cause a brief lean out which as mentioned above seams to be the piston is rising too fast to allow enrichment. I tried thicker oil which helped but anything heavier than 20w caused me to have a slow throttle response (which feels like serious turbo lag). Instead I am trying to reprofile the needle in the area that covers acceleration. Have a look at the link below:

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

https://www.youtube.com/watch?v=cCc3MylBTfk

Fuel pressure seems to be ok..

I'm going to change the dashpot on monday.. a weekend off with my wife has my priority right now

Could it be the temp compensation Bi- metal in the HIF leaning out as it gets hotter. if you flush more fuel it cools down again ??

Edited by Sir Yun on 29th Apr, 2016.

That sir, is not rust, it is the progressive mass reduction system

http://aseriesmodifications.wordpress.com/

Problem solved so far.. Changed the piston of the HIF,still using the original dashpot. Mixture is still a bit lean at low RPM, but the engine is feeling fine when I push the throttle.. The rest could be done by customizing the needle. Thanks for your help guys!

What was up with the piston to cause the problem?