Just had my subaru classic engine rebuilt ran in fine now when I took it for mapping with apexi power fc the mappers told me the car can't be mapped cause the fueling and air ratio all over the place and it would be better buy simtek cause I can run it without the maf, cars also never idled cuts out all time been told this is down to the ecu not been good enough for my setup

Spec
Rebuilt engine forged pistons sti rods acl shells
Vf23 turbo
Front mount
3" exhaust
440cc injectors
Apexi power fc
Blitz cone filter

Thanks for any help

 

You have a fault somewhere the Apexi, whilst old technology, should be good enough for those mods, could be a failed maf

 

Ok thanks are they just trying sell me ecu that the car really doesn't need

 

I built the engine and spent ages trying to get it to idle, looking for leaks, tweaking the ICV etc. We took it to group B motorsport to go on the rollers, Steve Simpson had a go with it but the problem is the MAF readings are jumping around all over the place and He thinks it's down to the fact it has a cone filter and MAF and the air is pulsing irregularly. We have fiited a front entry turbo, it was previously 90deg inlet, but it wasn't idling prior to the change either?

 

has anyone tried just switching the MAF sensor?

 

No, it's sounds obvious but it runs ok over 2.5k, the maf reads fine, it just can't cope with the idle?

 

Its perfectly possible for this condition to exist, I agree that the first port of call should be to swap the maf for a known good one. A cone filter will not cause the air flow to "pulse" it could change the air flow distribution through the maf and affect the cooling effect but it will not "pulse" it, that needs maf reversion which can't happen at such low air velocities
Sounds that possibly the sensor is contaminated enough to cause it to malfunction on low air flows but work well enough to allow the engine to run reasonably at higher air flows
Substitute its OEM ecu to prove its not an Apexi aberration as well, they are renowned for bad behaviour.