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I am getting ready to get 264 cams install in the car. Currently, I have the single turbo chip with out cams. Which chip do I need for single with cams. Anyone have on sitting around that want to trade for stock injector chip or single turbo chip.
 

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I'd run the current chip (18B) for a while and see how it works, or try the 18D which has been reported to work well with cams/single turbo upgrade. I had the 18B chip when I first installed the 264 cams and it seemed to do very well except that the idle was a bit rich -- around 12.8:1 -- but nice and smooth and steady. The car seemed to run good under boost and AFR looked good, though I only drove it a few miles and didn't boost very high in the higher gears, so I'm not sure what it'd have done at, say, 25+ PSI at high RPM in 4th gear.

Hoping to eliminate the slightly rich idle, I installed the 18C chip. With the 18C, idle speed was too low at around 550 RPM. I made some modifications to the vacuum lines on the intake side to increase the idle speed and took care of the idle speed issue. With the 18C chip the idle AFR flucuates from about 14.7:1 to 18:1 about every 20 seconds, momentarily cycling up to the 18 range then dropping back down. No major problems as a result, other than a slightly rough idle during the 5 seconds or so when it's waay lean.

I intend to reinstall the 18B chip and play with it to see if it's overall better, but I think it is. With the 18C I pull about 8% fuel from 5K RPM on up, and that gives me a nice AFR curve under high boost. So, I'm thinking that if the 18B chip isn't mapped to provide as much fuel on the top end, it might be about right without pulling any fuel up there. If I don't like the 18B, I want to try the 18D.

Another thing that I've seen/heard of on the 18C chip is that at high boost the AFR sometimes goes a FULL point or two lean for no reason once in a while -- with no changes being made to the VPC or fuel controller settings, I'm liable to get in the car some day and it's just running way leaner under boost than it was the last time I drove it. I know of 3 big single cars that have done this, and all of them happen to be on the 18C chip. Makes me VERY glad that I have the built-in wideband. I never saw my car go lean on the 18B chip, but that could be because I never drove it enough on that chip to have it happen. SO, I am NOT saying categorically that the 18C chip does this and others don't -- just that I've seen it on 18C cars, but have not had the opportunity to see it on others. I'd definitely caution anyone running a VPC to keep a watch on your AFR at all times when running significant boost.

Steve
 

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Steve-
What did you do to the vacuum lines to increase the idle speed? Thats something i want to try on my car..

-Aaron


Boost Junkie said:
I made some modifications to the vacuum lines on the intake side to increase the idle speed and took care of the idle speed issue.
Steve
 

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T the two power steering pump vacuum lines together. This tip was from SP.

BTW, you can just pull the PS line off the hose barb just aft of the throttle body to see what the result will be before you actually T the lines. It raised my idle speed by about 200 RPM.

Another thing I thought about trying is putting an MBC type valve on a dedicated vacuum hose from the plenum (and putting a one-way valve -- check-valve type -- and a filter on it). It seems that you should be able to use that MBC type valve to adjust the idle speed as it should more or less duplicate opening the throttle plate a little bit. I haven't actually tried it, though.

Steve
 
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