markwild

Folks, my 98UK turbo has full-decat, K+N 57i and PE ECU Upgrade. It is set, via the ECU to boost to 1.2 and hold - with cut at 1.4.

I fitted a Hybrid FMIC this weekend and since I've found that the boost is not holding....

WOT in 3rd, 4th and 5th shows the boost climb to 1bar pretty quick, with blue light on AFR. Then, the boost can pulse between 1.2 (in fact I've only seen over 1.1 3 times in a dozen or more test runs) and 0.8, usually holding around 0.8-1.0. However, the pulses are not smooth, the boost increases and then quickly drops, as though I've backed off slightly

At the point of the 'back-off' feeling, the AFR decreases, sometimes going red !

I'm not sure if this can be put down to a leak - I guess if a boost pipe is intermitently leaking, it may just go under sustained boost, which might upset the mixture, but I'd have thought it would go rich, not lean....

My leading suspect pipe is the one from the bottom of the DV (standard)- not the I/C side, so I'm not sure this can cause the problem.

It is worth noting that my up-pipe is also leaking, which I'm fixing next Saturday (but I'm not sure it can be related)..

If it was boost only, I'd suspect a leak instantly, but does anyone know whether a leak would cause AFR effects, (can boost soleniod probs cause AFR weak mix display?)

It really does appear as though I've lifted off slightly, say 3/4 throttle type position.

Note that its not really violent and if the throttle is held at WOT, the red sometimes changes back to blue and the boost increases again...

Anyone any ideas...

Thanks,

Mark

markwild

Maybe I have the chicken before the egg here ----

On further road tests, I've found that the AFR shows blue for a time after WOT is applied (say at 80mph in 5th) and then drops to red. It remains at red, unless the throttle is lifted and re-applied - in which case blue is shown for a second again...

In my first post, I'm looking for a reason for boost loss to affect the AFR - but I think maybe its fuel starvation affecting boost - which seems more likely ....

I'm a bit short of facts here, so I'm hoping someone can help out - would the AFR show blue momentarily (a second or so) as throttle is applied if the fuel map was too lean ? Or is this more a symptom of fuel pressure loss, probably due to the pump either starting to give out or being over-stretched ?

Can anything else cause lean mixture - ?

I'm pretty sure that it was OK before I put the FMIC on, as I installed the 57i kit the week before and didn't notice this leaning out when testing it...

Thanks,

Mark

markwild

Anyone on this ?