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AFM problems - I think?

caminperth

By caminperth,
in Western Australia

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Gradenko Mentor

Gradenko

Posted
Posted

caminperth, I've had this exact same thing happen to me twice in the last week, both times in really cold weather. Your first guess was right, I'm fairly sure its a voltage induced fuel cut. Its harsh too, like someone suddenly slamming the brakes for an instant.

A fuel cut defender is very risky. Because the AFM is at max voltage, the ecu really doesn't know how much load the engine is under and so can't fuel it at all well. Like flying blind. The ecu would just see flat 5V coming at it until the flow drops below 5V.

The only alternatives are lower boost on cold nights (painful for me with a bleeder), or a Z32 AFM and anything you need to get it working (ecu etc). I've heard of ppl using Z32 AFM's with blue screen SAFC's, and the SAFC II definetly supports it, but I think it'd be a cludge to get it working with our 5 dial jobbies. It could work though, the Z32 AFM's are still 0-5V, just using a different scale. The ecu can figure out closed loop for itself and the SAFC can compensate everywhere else. But it is still a huge cludge.

caminperth Grand Master

caminperth

Posted
  • Author
Posted

bam - you win.. good work.. :P

Gradenko/Paul - got it spot on.. thats exactly what happens. I supose i could run lower boost when it's cold - but thats painful cause i want to go faster and take advantage of the cold weather.. :P

hmm looks like a new ecu could be on the cards after a cooler.. i'm not interested on wasting money going down the path of dodgy fix-ups.. would like to do things properly because experience tells me it's the easiest and cheapest way.. :P

macka Veteran

macka

Posted
Posted

U can disengage fuel cut

When your SAFC is mapped on the dyno when your AFM reaches 100% your computer still pumps out pulses for injectors so the tuners just bump the AFC up or down accordingly

Its quite accurate but of course at the time u do reach 100% its time to upgrade to Z32 or MAP :)

Gradenko Mentor

Gradenko

Posted
Posted

I'm suprised ppl with upgraded turbos and stock afm's (aidwin?, macka?) aren't hitting the fuel cut in the this weather. We can't be flowing more air than them with our stock turbo, maybe our afm's are faulty? You two should go out "testing" tonight and get back to us. :P

ix9 Grand Master

ix9

Posted
Posted

I'm having the exact same issue with my car. So getting an SAFC-II tuned properly will eliminate this ?

I still dont know how the car senses boost ? anyone enlighten me?

Also getting an EBC in the next few weeks... I thought these negated the need for an FCD ?

Gradenko Mentor

Gradenko

Posted
Posted

Ours car's don't sense boost directly, but measure the air flow load (and density) through the afm. More boost = more air flow = higher afm voltage. So the problem we're having is, sensible boost + super dense air = max afm voltage.

Gradenko Mentor

Gradenko

Posted
Posted

Z32 AFM and SAFC-II should work.. in theory. Where's steve-sst when we need him?

The difference between cars could be explained by variance in the afm's operating voltage over a (up to) 10 year period. I mean, when the car was new, they had to deal with climates that included seasonal snow, so the afm should really be able to handle cold, dense air without freaking out. That's one possible theory, but it's probably not the right one. :P

caminperth Grand Master

caminperth

Posted
  • Author
Posted
Originally posted by Gradenko

Ours car's don't sense boost directly, but measure the air flow load (and density) through the afm. More boost = more air flow = higher afm voltage. So the problem we're having is, sensible boost + super dense air = max afm voltage.

i'm not sure if i'd call me running 0.9bar on a stock cooler "sensible" - but it's great fun.. :(

macka Veteran

macka

Posted
Posted

I have a series 1 blue screen for sale if anyone interested

Hasnt had much bloody use :D

Gradenko as Paul says i had a retuned Standard computer which removed my over boost cut(air volume) and 180kmh cut but since then ive sold it and running lower boost

In fact im not running any boost i was bored on the weekend so i took the turbo off

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