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Some boost and spiking questions


Guest bastaad525

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Guest bastaad525

Well as you've all predicted... the car is already starting to feel 'slow' again. I think part of it is the fact that I turned the boost back down a little bit. I had it to where it would run at 10psi, but the grainger mbc was allowing a little spiking in there, up to 11ish before settling back down to 10, and that got me nervous. So I turned it back down to 9 so it wont spike above 10. But I'm wondering, was it necessary?

 

I've seen a lot of people run 10psi safely, w/o the intercooler, with stock EFI. I'd like to turn it back up to 10, but should I worry about the small spiking? When it spikes it drops back down very quickly, like .5 second. The car is running good now, not too rich or too lean, pulled the plugs after prolonged 9psi running, they look perfect. The engine temp stays nice when on boost, right in the 160-180 mark, sometimes up to 190 if it's really hot out. I have yet to stay on the boost for more than 3-5 seconds at a time. Is that 1/2 second at 11psi enough to break anything? I know it's enough to break the tires loose when it comes on :) it doesn't do it anymore with the boost turned back down :cry:

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Guest bastaad525
:-P yeah I know... I already have an I/C, from a Buick GN, but it's gonna cost $$$ to get the piping done, and I"m all out of $$$, this swap cost me a small fortune :cry: In the meantime I want to get the most out of it that I can. If 10psi is safe (with a little spiking), I'd like to keep running 10psi. Just wondering if I should even worry about the spiking at all.
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Seriously, how much boost spike do people see with the stock turbo? I was spiking to ~10psi then levelling off at 5psi or so with the stock settings and an I/C. How normal is this? Or is it a product of the way my boost control is set up?

 

5 psi of boost spike is alot. Look into your boost controller and or intercooler set up.

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Guest bastaad525

yeah 5psi is a lot.... The only reason my grainger MBC is spiking at all I think is because one hose is a little too small diameter, and both hoses are a little too long, so the pressure has to fight it's way a bit farther to get into the wg actuator. Before I put the MBC I had no spike.

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Bastaad, I think you'll be alright at 10psi with a small spike. I've run my car at the strip at .8BAR (~11.5 psi) and I have no detonation or problems whatsoever. I check my plugs every other week and they're good. For normal driving I leave my boost at stock settings though. Only at the track I run the higher boost levels. I'm using a Trust Profec B and it doesn't spike at all btw.

John 82ZXT

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Yeah, no i/c on the runs. Soon though, right now I'm replacing my exhaust manifold gasket (what a huge pain it is), and then I'll be looking to get the i/c done. For track days, I just throw in some super conc. octane booster and it seems to keep the car running fine. Dunno how much it helps, but for 5 bucks, I'm not complaining. However, on extremely hot days, I keep my max boost to .65 (~9psi). Anyway, I guess I shouldn't push my luck too much.

John 82ZXT

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Guest bastaad525

you hit on another good point for me... I kinda like that my boost controller gives less boost when it's really hot out and more boost on cooler nights, without me having to adjust a thing. It's kind of compensating for the increased heat and lessening my risks of detonation when it's hot like that. I've been thinking of adding a gallon of touline to each tank of gas, to up the octane a bit and see if the car would put up with 11psi regularly. Last I read, one gallon to 10 gals of 91 octane would bring the octane up to like 94. The stuff is cheap at hardware stores and I know lots of hot rod guys use it on their high compression N/A motors.

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