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Old 01-04-2004, 01:40 AM   #1
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Default No boost gain

I mentioned in another thread about my fiero , I have a 87 fiero gt with a 93 3800sc.
I swapped the sc for a 95 model sc& throttle body. I used the smaller 93 pulley yet I have no more boost than I had with the 93 sc& throttle body. If I put the larger 95 pulley I can reach 5 lbs of boost (getting 9lbs now, same as befor swap)
Could someone give me a few ideas as to what I should look for?
I have a fairly freeflowing exhaust, CAI and that is about all the mods for now.
I did have a small leak where the egr tube went into the sc but I fixed that and nothing else I know of to be a problem. Any help is appreciated.
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Old 01-04-2004, 02:51 AM   #2
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Overboost protection? What PCM are you using?
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Old 01-05-2004, 12:01 AM   #3
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Pcm? same as ecu? I am really unsure right at this point after the deal with the Eprom and # not listed then finding it might be from some oldsmobile...... I found an ECU for a 93 ssei I am picking up tomorrow and giving it a shot. I dont see why I lost boost by adding a pulley close to where the alt use to be and getting more wrap around the sc pulley yet either but i am going to try to work on it tomorrow.
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Old 01-05-2004, 03:30 PM   #4
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I did find out I do have wrong eprom it is from a 94 olds n/a. Ordered new correct eprom , hopefully will make big differance. I got my boost to peak around 11lbs I readjusted the boost solinoid by loosening the bolts and pushing the solinoid down. I treid Jeffery'* bypass method with no sucess but just readjusting made the differance.
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Old 01-05-2004, 10:17 PM   #5
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11-12 psi sounds right for the 2.2" pulley, assuming you have a good intake. This time of year it should lean to the high side of that estimate.
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Old 01-06-2004, 12:03 AM   #6
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i have the 2.5 pulley.
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Old 01-06-2004, 12:05 AM   #7
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There ya go. That'* the difference between them. I have to use a 2.2" to get the same boost. Sounds like you fixed it!
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Old 01-06-2004, 12:18 AM   #8
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It really did make a noticable differance but i am going to go to the 2.2 pulley , I have to really whind the car out to hit that much boost, + I will have the correct eprom and will finally install the jet module this week hopefully. I did learn from buying the eprom I have 2.96 gear ratio..... kinda odd what you find out buying a eprom
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Old 01-06-2004, 12:20 AM   #9
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Going to the 2.2" with your setup would probalby hurt performance. Boost will drop off from heat loss. Don't go into the 2.2" without an intercooler. The performance charts on the M62 will show this.
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Old 01-06-2004, 12:25 AM   #10
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would you recommend staying with the 2.5 or possiably going a tad smaller to a 2.4 or 2.3. or do you not think it would be worth $90 for the differance of the 2.4 or 2.3? I guess i need to get eprom issue straight befor i go buying more. The guy @ parts dept said with the wrong eprom I could have major loss of power and the correct eprom could make a world of differance.
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