Hi All,

i will do my best to describe what has happened, but my technical knowledge here is poor so i may have mis understood some of the results and what they guys were saying.

I first went to power station with a GTEC chip and PRV set to 1.2 bar in 5th. I had this setup for about 1 week before getting this checked.

Went on the rollers with this yesterday - it was running way to lean for them to do a full power run.

SO this morning i Went back to them after changing back to the standard chip with the PRV set to 1bar in 5th. (only other engine mods is drilled air box K&N filter and miltek exhaust system and bailey DV26 dump valve)

I was so hoping this would give normal fuelling but although better it is still lean. See the results in pdf format here:
http://www.unlockme.co.uk/POWERSTATION.PDF

IMPORTANT NOTE the Lambda graph line needs to be shifted back by approx 9 secs / 750 RPM - as there is a delay in measuring this (i think thats what he said). (this is the reading from the probe up the tail pipe - approx 9 secs to register). This delay made it difficult to interpret the graph.

He was sat in the car during the power run watching a digital display he had attached to the steering wheel. I belive this showed him live fuelling iunformation (wide band lambda sensor i think). What he was saying is that when the car comes on boost this reading was at about 0.92 where is should be closer to 0.80. The reading did eventually dip to 0.82 but only much later on (approx 6000+ revs). He feels this is way to late.

So what i think he is saying that at the point the boost comes in it is running to lean and the fueling only gets about right much further down the rev range.

They did various checks to rule out the feul pump (its ok they think), so he suggested it might be the Mass air flow sensor. - Does this sound possible?

He did acknowledge that he had not seen any 20VT results himself so had nothing to compare them too, but in his opinion the fuelling was inconsistent. (he did 2 power runs)

BHP stayed pretty much the same on both runs at approx 230.

The bad news is that i have a track day tommorow which i am keen to go on. One of the staff members rekons i should be ok for track as the fuelling is ok when on sustained boost. The other guy was more conservative and thought it best not to track it.

Very helpful guys and very accomadting with getting me in. At £58 i felt very good value.

So does anyone have any toughts on these graphs or any ideas why my car would be running lean on the standard chip and amazingly lean on the GTEC chip.

Look forward to some expert advice

Thanks

Dan

Could be the MAF. Have u cleaned it recently?

Ross

if just cleaning the MAF sorts it that would be great - will see if i can find a guide.

would you track the car with those results Ross?

I dont know what the lambda reading converts into afr, but i wouldnt bother. Check the guide for cleaning the AFR but be VERY VERY CAREFUL, as this can be broken easily. Carb cleaner should do the trick. Allow to dry before re-fitment.

Ross

lambda x 14.7 = AFR

For example 0.85 x 14.7 = 12.5

well reading the problems people have had breaking MAF's i am not keen to do this myself...

I guess its yet another visit to Motormech....

Any other ideas what could also cause the car to run lean? Lambda sensor maybe?

Also, can someone explain to me what it really means for a car to be running lean - i know its underfuelling but how would a running lean cause your engine to blow up?

Are there any other fuelling graphs posted on the forum to compare?

Lots of questions i Know :-)

Anyway thanks for all your help so far.

Dan

mine ran lean as it came on boost with the gtec/prv @ 1.2 bar combo..BUT... as soon as my accelerator cable was tightened up properly it sorted itself out and was fine...doesnt make any sense to me; maybe someone on here can explain it?

If your cable was loose then your throttle position sensor (TPS) might not show its 100% open.

Therefore if the ecu would change the afr position on the map.