UPDATED- AFM induced fuel cut

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Postby Gary » Mon Mar 14, 2005 10:02 pm

makarov wrote:So, could someone exlpain how to disconnect the vacuum line (which one etc...) and why this would not be advisable? I suppose unregulated the car could over-boost. On an otherwise stock car, how much boost will it generate?

- Dave


There is only one vac line to turbo pressure sensor.
It will not generate more boost on stock car but it will remove the FC entirely.
Let say if the wastegate failed to open and you didn't realize it, FC is the only thing to protect your engine.
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Re: UPDATED- AFM induced fuel cut

Postby RIalltrac » Tue Mar 15, 2005 12:18 am

alltracman78 wrote:
erolit wrote:I Don't want any fuel cut at all, ever, not once. Is there any way i can find whatever it is that cuts the fuel (Relay? Solenoid?) And smash the crap out of it with a spade?


:rofl:

I've been thinking about using a second bc for fuel cut. I think the setting it up will be kind of a pain.
I will get around to it one of these days....


I'm thinking about doing this as soon as I can scrounge up enough cash for another boost controller. I dont see why it would be so hard to set up. yank the line to the pressure sensor, set up a mbc and dial it in. Once you have it dialed in to create the boost you want your fc to hit at remove it and stick inbetween the mani & sensor. Wham whole new fc. then just retune another to regulate how much boost you want to run. At least thats how I plan on doing it, anyone care to disagree?
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Postby erolit » Tue Mar 15, 2005 7:18 am

No that sounds like an ideal set up actually, and it is what i have.

Its basically a user-adjustable mechanically engaged fuel cut - far easier IMO to built a $5 fuel cut than set it up eletrically.

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Postby furpo » Fri Mar 18, 2005 1:19 am

i fully agree with erolit's conclusion. i had my car on the dyno not to long ago and found that with the vucuum hose to the pim pungluged the a/f ratio became richer but timing was not effected. with the plug disconcted the mixture became very rich and timing was retarded.

i got rid of my fuel cut by putting a 4.3V zenier diode between earth and the pim plug inside the ecu (ie no cutting of wires) i have run up to 16 psi with no fuel cut. that is enough on to distroy the standard turbo.

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Postby ChrisD » Sun Mar 20, 2005 7:41 am

furpo wrote:i fully agree with erolit's conclusion. i had my car on the dyno not to long ago and found that with the vucuum hose to the pim pungluged the a/f ratio became richer but timing was not effected. with the plug disconcted the mixture became very rich and timing was retarded.

i got rid of my fuel cut by putting a 4.3V zenier diode between earth and the pim plug inside the ecu (ie no cutting of wires) i have run up to 16 psi with no fuel cut. that is enough on to distroy the standard turbo.

roger


How did you measure timing???
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Postby furpo » Sun Mar 20, 2005 10:56 pm

with an ignition advace plot using a scope. the same way you would do a plot for a car with a dizzy.

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Postby gpmarzan » Mon Mar 21, 2005 12:49 am

so isnt putting a mbc to the turbo pressure sensor same thing as disconnecting the hose? like Gary said. Whats the point on putting a mbc then if you can just remove the vac hose?
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Postby RIalltrac » Mon Mar 21, 2005 1:19 am

because if you set up your boost controller for say 16 psi, when the boost hits 16psi its going to open the boost controller up and allow 16 psi worth or pressure to hit the sensor, and in turn initiating fuel cut. You keep the fail safe of FC, which is something I definately want to keep. for safety reasons.
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Postby gpmarzan » Mon Mar 21, 2005 1:55 am

RIalltrac wrote:because if you set up your boost controller for say 16 psi, when the boost hits 16psi its going to open the boost controller up and allow 16 psi worth or pressure to hit the sensor, and in turn initiating fuel cut. You keep the fail safe of FC, which is something I definately want to keep. for safety reasons.

but if you set the boost controller up to 16psi for the sensor, the sensor is still programed to hit fuel cut at 12psi, so when you pass 12psi, you will hit fuel cut way before you hit 16psi on the boost controller. the way to use the mbc with the sensor is to set it to a lower psi setting, correct? so that means you will set the mbc to less than 12psi while boosting to whatever you set your other boost controller to, which basically means no fuel cut-same as disconnecting the vac hose. am i having brain farts? let me know if i am. :twisted:

edit: i dont know if we're on the same page, chris, but your plan is to use a mbc as a fcd right? i think a mbc will eliminate the fuel cut entirely for the reaon i stated above.
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Postby RIalltrac » Mon Mar 21, 2005 12:31 pm

okay let me clear my head, from what I understand a mbc will allow you to build boost to a certain point, once that point is hit the mechanism inside the mbc will open an allow pressure through to your waste gate actuator thereby opening the waste gate and limiting boost to what ever it is you have it set at. Now if you set an mbc up to whatever it is you want fuel cut at, for me I'll use 16 psi, and place it before the pressure sensor but after the manifold. When the manifold reads 16 psi, the mbc will allow pressure through to the pressure sensor, and since the pressure sensor kicks on at 10-12 psi 16 psi will be more than enough to kick it into Fuel cut mode. Now just correct me if I'm wrong as to how an mbc works, because if it works the way I think it does, the mbc could very well act as an fcd. I would think turning the setting down would just allow you to hit fuel cut at whatever the factory setting is, because you'd be allowing any pressure over what you have it set at through the mbc, example you set it at 5 psi anything over 5 psi is going to get read at the pressure sensor.
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Postby gpmarzan » Mon Mar 21, 2005 4:42 pm

ok i got it down now. i thought it over again and yea youre right. :doh: thinking of having 2 mbc got me all confused.
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Re: UPDATED- AFM induced fuel cut

Postby Rallly » Fri Dec 16, 2016 5:53 pm

91 Celica AllTrac oem turbo

After disconnecting the rubber hose(blocking it with a bolt) that goes to the turbo pressure sensor, my fuel cut has been gone, YAY:)
With the nipple capped on the sensor side my oem boost gauge is always showing MAX boost in my gauge cluster.

With the nipple NOT capped, oem boost gauge goes up and stays at 1/4.

Car seems fine both ways but I wonder if with it capped showing full boost on cluster if this will alter what the ecu does with fueling?

Any ideas?
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