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Discussion Starter · #1 ·
I freed up the intake (FMIC), and exhaust (3", custom Y pipe), and I hit fuel cut in every gear at > 1/2 throttle. This is on STOCK TWINS. I have no boost controller, boost is stock. It seems like it happens right around 15psi.

Is there anything I can do to get past FC? Can I use a FCD or a good boost controller to "LOCK" in boost at 14psi? Can that even be done?

Thanks!
 

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Discussion Starter · #3 ·
Is this 2J map sensor a real solution, and has it been proven to work? Can a boost controller limit boost? It can't make the boost less than the WG spring, I know that. What are the stock twins set at? I am really overboosting on a stock set up!


I think I will pass on the injectors at this time. I think mine worked better now they were cleaned.
 

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someone asked this question a few weeks ago and someone did a mini write up on how the safc could remove or raise fuel cut to occur at higher boost. i forget exactly how it works though but he seems to know what he's talking about. wish i could remember his name.
 

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everyone says the stock ecu runs really rich, take it to the dyno with an afc and tune the a/f to ~ 12:1 should bump the fuel cut up a little bit, if not get bigger injectors and pull the extra fuel out w/ afc and should raise fuel cut quite a bit

The stock map sensor maxes out at 14-15 psi so it hits fuel cut... Makes me wonder how these mines ecus have 'no fuel cut' yea they take out the coding for fuel cut, but how would they know how much pressure is in the manifold?

2jz map sensor has a higher range (16-17 psi?? i dunno) but all it does is scale down the map sensor voltage, so on stock injectors you will run lean
 

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anything that sacales the map signal down will work.

Zenner diode will eliminate FCO. Of crouse be careful though it's like adding a FCD to a 7m.

2J mapsensor is with 440 CC injectors are the perfect match since it's stright off a 2j from japan.

for 5$ i'd get the zenner diod, you should be safe if you are just doing 15 PSI.
 

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Pete your y-pipe is probably _TOO_ good, that's what's making it hard for the wastegates to hold stock boost!

Whatever you use for boost cut, I'd really watch out to make sure you don't boost much higher than 15-16psi. 'Cause with a boost cut device of some sort, the ECU will fuel at 15+psi as if you were at 15psi. And you've already got a very well flowing exhaust, making the cylinders fill better than the ECU ever tought they would. So basically, for those two reasons, much more air's coming through then the computer thinks, and I bet you will run leaner than you would like to past 16-17psi. So yeah, when you install the boost cut controller just keep an eye out on the boost and I'd really let off if it climbed much higher than 15 or 16psi.

But I don't know how to hold a lower boost short of using the throttle, porting hte WG holes (if there's any room in there...), going with external wastegate, or using smaller dump tubes for the WGs.... hopefully 15psi is right about where it starts to hold 'cause that seems pretty safe.

Shiva
 

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remember too you don't want to go much more on the cermaic turbos... they will nuke
 

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I hit fuel cut at 35-40% throttle with my car. Thats with a AFC and 440cc. I havent tuned yet, so thats most likely the problem. Get a FCD or BCC as a last resort, do it first with a AFC/wideband and some bigger injectors if needed.
 

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The boost controller cant really lower boost below stock levels, but it will effect how the wastegate is opened. I use the AVC-R from Apex'i and it allows the boost to come on at lower levels since the wastegate is held closed until the max boost is hit. You may want to consider enlarging the wastegate holes by 1mm or 2mm though. Even with the best boost controller it still might not be able to control the boost since youre exhaust is so open, unless you allow more exhaust to bypass the turbine
 

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Power fc?
 

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Discussion Starter · #13 ·
this sucks because i built a car i really cant drive hard until i figure out this FC issue!

Does anyone know what the stock spring is on the stock twins? I know it reads 9psi on a totally stock set up, but with all that back pressure and intake restriction, what does it really read?
 

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The wastegate spring should move at approx. the same psi as a totally stock setup, but with an exhaust that flows so well, it just cant bypass enough gas from the turbo, so it's not holding that 9psi.

Maybe ask Trev (supraturbo1987) if he has any trouble holding stock boost, since he has an opened up exhaust, too.

So maybe the first step, just get rid of the boost cut. It might be best to bite the bullet and pay $75 or whatever and get a Greddy BCC for an mr2. But the zener diode, or a mechanical device that bleeds off boost going to the map sensor, could do it for you too.

The next step would be to verify the minimum boost the wastegates will hold. Install a ball-and-spring type of boost controller, that _might_ actually help reduce your minimum boost very slightly. Hopefully you can run only like 15-16psi.

If it starts to climb higher than that... I dunno, man... you might have to rig something up with those wastegates. Maybe shorten the small arm that connects the actual valve to the rod coming from the actuator... if its slightly shorter, the valve should swing open wider. Or port the WG passage, or maybe make the actuator rod adjustable... hopefully something simple will work well enough.

Shiva
 

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Discussion Starter · #15 ·
Shiva,

All I want to do is run the stockers @ 14psi, nothing more. I'm not looking to run 18+psi. If I could keep the boost down to right @ fuel cut, then I would BE HAPPY! It's more than fast enough at this setting.

Thanks!
 
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