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Discussion Starter #1
Earlier this year, I had a procharger installed on my car running 8 psi. The car ran great and all but a couple months ago, I decided to gets some 3.73's to give it a little more kick but now it seems like I have no more power up top. That really baffles me since centri blowers are suppose to make more power in the higher rpm's. I never put the car on a dyno before I had the 3.73's put on but I took it to one about a week ago and the car only made 325 rwhp. After tuning it with the diablo a bit they were able to get it up to 340 rwhp. I figured with headers, catback, xpipe, plenum, 75 mm throttle body, I would be at or above 400 rwhp. On top of that, it stopped making power around 5200 rpm. Anyone have a clue as to why my car is so underpowered? Did installing the gears directly or indirectly cause me to lose power? The car did seem noticeably faster when I had the stock gears in. Im kinda tempted to put the stock ones back and and see where im at. I dont know. Any suggestions are much appreciated
 

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Procrastinator
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dyno results show your power, gears just fake power. Steeper gearing will make it feel like it pulls harder, and it will by a little, probably skewing how you feel the pull. Though I dont think it would feel slower up top. Gears dont really affect power, maybe something went wrong elsewhere. How do you not have numbers from before, didn't you get it tuned for the blower? You should have numbers from that.
 

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Discussion Starter #3
dyno results show your power, gears just fake power. Steeper gearing will make it feel like it pulls harder, and it will by a little, probably skewing how you feel the pull. Though I dont think it would feel slower up top. Gears dont really affect power, maybe something went wrong elsewhere. How do you not have numbers from before, didn't you get it tuned for the blower? You should have numbers from that.
I had it tuned after I got it but it wasnt on a dyno. There was no dyno in town where I lived at the time
 

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Procrastinator
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well trouble shoot other issues, gears are the second to last thing before power gets to the ground, they wouldn't be the cause of loss of power.
 

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gears only increase acceleration and make the rpm band different, but they wouldnt make you seem slower up to you would just hit the revlimiter sooner. it sounds like the tune might need some tweaking but id bet the gearing isnt the issue.
 

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Are you running out of fuel? Those number are way low..
 

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April 2012 ROTM
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325 at 8 psi does sound low.....check the belt...are you gettin enough fuel? openin up the intake and exhaust should help a good bit...
 

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Baker Jr.
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Yep, dont expect 400+ on 8lbs bro, i made 370 with like 10, a 3.45 pully
 

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Baker Jr.
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Nice, i wish i could run long tubes,id help alot but cams are soon :)
 

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Yep, dont expect 400+ on 8lbs bro, i made 370 with like 10, a 3.45 pully
you cant go off the amount of boost for power... it all depends on the motor/set up.... at 8 psi I made 465rwhp... cause boost is nothing more then a measurment of back pressure in the intake it is not a measurement for how much air is going into the motor
 

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He said he has..

"I figured with headers, catback, xpipe, plenum, 75 mm throttle body"

And that power is really low 8lbs or not..
 

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He said he has..

"I figured with headers, catback, xpipe, plenum, 75 mm throttle body"

And that power is really low 8lbs or not..
I agree... unless this was on a mustang dyno... or the numbers were not corrected and the DA was crap..... thats why I always look at dynos as a tuning tool not a be all when it comes to how much power is being made....
 

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US Air Force (retired)
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Do you have an automatic transmission? Do you have a catted X-pipe?

Gears do not affect engine performance. A ProCharger at 8 lbs of boost should get around 350 rwhp through a manual transmission. That would be maybe 320 rwhp through an automatic. TB/Plenum might get you 10 more. Headers (yes, I've read about the incredible gains from headers) sometimes don't give much of a gain.

My car dynoed 385/370 before the headers were installed. But the tune was too lean at 6000 rpm. After the headers were installed and before the new tune it dynoed right at385/370. Boost before the headers was 8.9 lbs. After it was 8.9 lbs. The only thing we could determine is the catted x-pipe was still restricting the exhaust because we should have see the horsepower numbers go up and the boost numbers go down.

I really don't think the gears are the problem. My 3.73s really woke my car up.
 

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Baker Jr.
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Must have had 4.10s in it and you didnt even know :eek:
 

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