Question about boost fluctuations / surging?
04-24-2005, 02:10 PM
#1
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Question about boost fluctuations / surging?
Installed a boost gauge last week and am noticing pretty severe fluctuations in boost / car performance. Boost will spike about 22lbs and the drop down to 12 or so then back up to 20 and then settle out about 18 and then taper off. As the fluctuations happen, you can feel the car's acceleration surging. I did a leak check to 15 psi and found nothing. I am not running an MBC at this time. This occurance happens almost all the time. Once in a while, the thing will work beautifully and max out at 18 or so and the acceleration will be very constant (until the taper which I know is normal). I logged boost and didn't see and problems with actual vs. requested boost. Wondering if VAG is sampling fast enough to catch the spike. This has been happening since I chipped the car. Since I have the flashloader, I put the "stock" program in and the car works beautifully. Boost no higher than 8 psi. Any ideas or other stuff to check? Is there a way to do a functional check on the N75? I am currently using the AWE vent gauge. Is there any way it the needle's inertia that moving it into the 20's?
04-24-2005, 03:23 PM
#4
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look at this deviation...
<center><img src="http://www.its.caltech.edu/~benitez/boost.jpg"></center><p>certainly because GIAC doesnt know what he is doing. No MBC, band aids, etc...
04-24-2005, 04:10 PM
#6
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Not that I ever agree with Eric, but yes it is likely the programming
The boost surging/throttle cut is reported on here all the time by GIAC K03 owners, and I've seen it on so many cars first hand to think it is just an isolated problem. I have nothing against GIAC - in fact my H box chip worked great and hardly ever did this, it seems like A and M boxes do it the most. There are some workarounds you can do - install an MBC in parallel with the N75 to limit the boost spikes, or tweak the N75 by turning the screw clockwise in very small increments (no more than 1/8 turn).
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04-24-2005, 04:34 PM
#8
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holy **** 22psi!?
I have the giac X and I just also recently added a boost guage. the highest I ever saw was like a 20psi spike. normally 19, mostly in 2nd gear, and between shifts. but definately never 22.
