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Boost Problem...

SleepingTalon

By SleepingTalon,
in Engines & Forced Induction

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SleepingTalon Contributor

SleepingTalon

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I've got a weird issue with the rb25det Im running. The motor was just rebuilt with wiseco/eagle combo, and arp headstuds, with cometic gasket. The car is running an HKS 2540. When the motor was stock, before the rebuild, it was running 19psi (1.3 bar). With the rebuild on the car, if I try to run more than 16psi (1.1 bar), the car will "buck" and "breakup" all the way through the powerband. I would like to run UP TO 22psi (1.5 bar) on race fuel. I tried putting in race fuel thinking that it could be engine knock and timing getting pulled, because on the dyno plot, as soon as the higher boost level (more than 1.1 bar) comes in, the the car not only "bucks" but the power immediately drops down like the stock ecu is pulling timing. However, even with the C16 (117 octane) it still did the same. The car is making good power, even at only 1.0-1.1 bar, but I wanna run more boost. I've checked the plugs, and they are fine, and tightly gapped. I've also checked for vacuum leaks, and the system pressure tested fine. Could a bad coil cause this...? What else could be causing this problem? Just to let you know, Im using SAFC and adjustable fuel pressure regulator for fuel control, and the air/fuel ratio is perfectly flat at 11.8. Any ideas or suggestions would be greatly appreciated. Thanks again!

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SleepingTalon Contributor

SleepingTalon

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Has anyone had problems with tuning with SAFC at power levels of 300rwkw or more? That's about where I'm at right now with this thing, but I need to be able to run more boost. Bad coils are the only guess I have at the present moment, so I'm at a loss. It's pretty much a misfire, but at very low boost levels. Anyone else experience anything similar with their car?

Edited by SleepingTalon
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https://www.sau.com.au/forums/topic/101981-boost-problem/#findComment-1871037
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paulr33 Grand Master

paulr33

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Posted

maxing out the stock airflow meter will simpy mean you drop the bottom load point on the maps, so it will still work youll just loose accuracy as once you goto 5v your tune map becomes one dimensional

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SleepingTalon Contributor

SleepingTalon

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Well, it's like a misfire. So Im not sure what that could be. The plugs are tightly gapped, and the only thing I can think of is that a coil could be going bad. Any ideas of what that "bucking" or "miss" could be? I wasnt sure if the car would do that if the AFM just started missing "airflow counts" or what it would do.

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