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Discussion Starter · #1 ·
Ok so I have been reading thru the shop manual I just got and I have a really stupid question... It looks to me, and from what I remember the problem with the fuel cut was all in the vane meter. Now It looks like the fuel cut off is just a sensor switch inside the vane airflow meter... If this is true that would mean to get rid of that cutoff all someone would have to do is to wire the pump to a switch so that that switch inside the vane airflow meter was not a problem anymore...

Is this true? IF so why have more people not done this to get rid of the problem?
 

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its not really a switch, its more or less when it reaches the end of its range. what your talking about though is the vaf hack, the issue being though that you will run lean because its doesn't know how much boost you are making.
 

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Discussion Starter · #3 ·
well im not really talking about pulling the vaf... I am sayin leave it there BUT run the pump off a switch so that the ecu is still getting all the info and tell the injectors how much to put in but the car has no way to shut off the pump...
 

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it doesn't shut off the pump though, it shuts off the injectors :|

if you wanna really wire your pump on at all times though, go for it. there's a 2 pin connector near the sti that can be wired to itself to make the pump always on, wont make a difference though.
 

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you can always take off the top of the VAF and see where the connector touches when it shuts off fuel...then coat the contacts with maybe nail polish or something?
 

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I don't think boost cut is like the speed governor, it doesn't have it's own sensor, it kicks in when the VAF reaches a certain point in the map but I don't think there is any extra signal sent to the ECU for this to happen, which would mean, boost cut happens in the computer and that's why it gets eliminated by changing/rewriting the chip in the computer.

If you cover the point that the VAF reads at and boost cut occurs (electronically) you would also be blocking out any air readings going to the computer.
 

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you can however put a rubber stopper in the vaf to keep it from going all the way back. regardless its a bad idea and will lead to the destruction of an engine.
 

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Discussion Starter · #9 ·
Ok... So does anyone know if the probinator ship is still avalible somewhere?
 

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I don't think boost cut is like the speed governor, it doesn't have it's own sensor, it kicks in when the VAF reaches a certain point in the map but I don't think there is any extra signal sent to the ECU for this to happen, which would mean, boost cut happens in the computer and that's why it gets eliminated by changing/rewriting the chip in the computer.

If you cover the point that the VAF reads at and boost cut occurs (electronically) you would also be blocking out any air readings going to the computer.

Being that these cars are factory swine rich cars, I don't think that leaning it out is a bad thing :)

Btw, the VAF door is open almost 100% when it sounds the beep and cuts fuel. You're not going to be missing much on the map :)
 

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Discussion Starter · #12 ·
so zach your sayin that just puttin a stopper in there would be ok? I just wanna know how I can make more boost without that cutout cuz it looks ertarded when your racin someone and that boostcut keeps kickin in... BUT at the same time I dont want to blow the engine again... :(
 

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yes, take it apart to be sure, ymmv.

just make sure you run 91+ octane, and you'll be fine.
 

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Discussion Starter · #14 ·
hmm.. I think I am just gonna get the probinator chip just to be safe... might as well do it right...
 

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Being that these cars are factory swine rich cars, I don't think that leaning it out is a bad thing :)

Btw, the VAF door is open almost 100% when it sounds the beep and cuts fuel. You're not going to be missing much on the map :)
Years ago, on Robs car, 91 GT (we only had 88-89 chips at the time), I tried two different ways of limiting the VAF's travel.
The first one I tried a thick (1/2") piece of weather stripping stuck to the back wall inside the vaf. It didn't come close to limiting the vaf at the right spot.

For the second one, I drilled and tapped an M6 hole into the back wall of the vaf, then used a long M6 bolt and put a nut on it, I screwed the bolt into the threaded hole about 1 1/2" in and locked it there with the nut. Even by stopping the back flap 1 1/2" away from the back wall the car still hit boost cut.

At which point I decided stopping the flap door to eliminate boost cut was going to limit the intake air so much that there wasn't much point in Rob boosting over 12lbs.


I remember a picture on this site of someones VAF, he had drilled a screw into the top of the VAF to stop the flap from hitting the boost cut point, you could see he had drilled and plugged several holes before getting the crew in the right place to stop boost cut.
By the placement of the screw I could tell he was stopping the main air flap and not the back of the V, his screw sat between the front and back of the V and looked to stop the VAF flap just over half way opened. Judging by the fact that all the other holes where plugged off, you can assume this was the most he could allow the flap to open without hitting boost cut, otherwise he would have left the screw in one of the other holes and probably never drilled the last one.
^ This guy's work was butchery to say the least, the holes looked to be plugged with clear caulking and I could never figure out why he drilled his holes to stop the front flap right in the path of air flow and not the back flap out of the path of air flow. But you could clearly see that he had to limit the flap quite a bit to avoid boost cut.

(Searched for the above thread and pictures but I couldn't find it).


P.S. I know the flap goes almost all the way opened before you hear the Beep when testing the VAF as per the workshop manual (Why I attempted it as a quick fix on Robs car in the first place) but it would seem to occur sooner in the path of the VAF flap when the engine is actually being driven at WOT.
 

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Discussion Starter · #16 ·
hmmm thats an interesting detail... but like I said I will just send in my ecu and have him put the chip in it for me.
 
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