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Discussion Starter #1
I guess spike is what the problem is called, not 100% sure.

I'll be drivin along and can boost to 12/13 psi fine in first gear... if i make a fast shift into second, somtimes it will hit fuel cut, somtimes it won't. same type of thing... if i'm in 4th gear at a low RPM and floor it, i'll hit fuel cut (14 psi)

what causes this? somtimes it happens somtimes it doesn't? I'm using a 50 dollar MBC right now, but it also happend when I had a Profec B (sold)


what is supposed to keep boost from spiking? on an profec e-01 would I have this same problem *assuming i set it up correct*


_ Justin



Mods: Apex-i Intake, 3" exhaust turbo back (No cats)
 

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A Supra with a stock ECU is going to hit fuelcut between 11 and 13 PSI, variables depending. There are many ways around this. Most get the Lexus AFM/550inj combo. Some go with the FCD but either way, you better have the right supporting mods and a way to monitor your A/F ratio if your just going to defeat the fuelcut purpose.
 

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Discussion Starter #3
Thanks. That much I know, I have plenty of supporting hardware on the way... what i'm asking is how to prevent boost spike.

I have the MBC (and at one time an EBC) set at 12 PSI but the boost will go far past that at times. Why, and how do I prevent that?
 

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When you set your boost controller, what gear did you do it in? If you did it right, you probably wouldn't be hitting 12-13 in first gear. Set the boost in 4th gear. The other gears should end up having lower boost than 4th because they put less load on the car. Set your boost in 4th gear and be done.

If that doesn't solve it then you might want to look into a different boost controller. The Profec B notoriously sucks and lots of MBC's are terrible too.
 

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Discussion Starter #5
haha, nice way to put it trent :)


alright, so. Is there anyway to have a constant throughout all gears? I want to be able to hit 12 PSI in 1st, 2nd, 3rd, 4th, and 5th, without going over...


I am going to be putting in 550's, MAF/T, e-01, and an emanage, so i've got the right hardware, is what I want do-able?
 

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With a good boost controller, you should be able to get close to that yes. I don't count 1st because it's over before you blink. A good boost controller should be able to regulate it if you tune it correctly. I set the boost in 3rd or 4th (preferrably 4th) and 2nd and 5th should follow along with what you set it to. If first lasted longer you would probably get to it.

It's been awhile since I only ran 12psi, so you may be able to get it to do that in all gears. Again a good boost controller is key there.

If tuned in 4th gear, the boost you make might vary in other gears by .5 to 1psi in either direction, but if it's working right and so is everything else (no boost leak, good vacuum lines, no exhaust leaks, etc) then theoretically you should be able to yes.
 

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Discussion Starter #7
great, thanks :)

EVERY line is new on the engine, and its in good condition... the only reason i'm running 12 PSI is cuz the CT26 maxes out at 16 i read, and its on the stock headgasket... (10,000 miles old) so I don't want to push anything to far


Thanks for your help.

Justin
 
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