pikey7

I seem to be having a few issues with the running since I had my last play.

I removed the ISV and the purge valve system (and just connected up the two hoses in the engine bay), And I replaced the hoses on my MAF with some larger ones. I have a Kokeln stage V turbo with a 70mm inlet, so I got a 70mm pipe with a single outlet for the BOV (the oil return is gone aswell as I have a remote breather, non-circulating), then an adapter to the existing MAF housing. I know that the air between turbo and hotwire is a lot clearer.

The problem I have, is that the tuning is now totally different. I seem to be running 2-3 leaner on the WB, and I've noticed that when I let off the throttle now, the A/F drops to 9 momentarily, and then raises to full lean (over 20 and off the scale).

Now I realise I need to add a bit more fuel to get the on-throttle tune back, but I've never seen that richening off before. Have I messed something up here?

TIA for responses, I'll be having another play later to see if i've messed something obvious up.

pikey7

I forgot to mention, when the engine goes rich, it stumbles. It also does this when I stop accelerating, not just backing off (so a slow gradual aceleration to a certain speed will provoke it aswell)

Well, I had a look, and I can't see anything obviously amiss. No disconnected hoses or anything.

I was thinking, could it be some blowback from the turbo compressor fooling the hot wire/MAF in some way (now it's got a nice clear patch between them)? Surely 10mm on the pipe diameter wouldn't make that much difference though?

Bengt Sweden

The MAF is extremely sensitive to where you put it. Even rotating it may make a difference since flow is not uniform across if you do not have very long straight pipes in front of and after it.
I had the same problem as you mention when shifting. I found that moving the MAF further away from the turbo and the BOV improved situation a lot.
Bengt