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Discussion Starter · #1 ·
After my first dyno session when the supercharger was intalled and tuned (about a year ago), I had a best of 410RWHP and 410RWTQ, this was with the stock manifolds and an X-Pipe w/Cats (which I was told would benefit me because of needed backpressure :confused: ) Since then, I installed a 75MM throttle body, MAC Longtubes, MAC H-Pipe (No cats) and I also went from 17" wheels to 18" wheels. I went back to the same shop about a year later and dyno'd at 395RWHP and 401RWTQ. What could be the cause for the loss of power??? I am running Autolite 764's that are no more than 1500-2000 miles old (which are the same plugs from the original tune a year ago) gapped at .34.

Anyone have any ideas???

Suggestions????
 

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First thing I could tell you is ditch the 764's. Why don't you try NGK-8 and bring your spark up to .40 to .42. How was your A/F? MAF could be pegged? Need alittle more info .
 

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How was your A/F? Maybe from changing the TB, Headers and mid pipe it might have affected your A/F to throw off your tune and loose power? just a thought

Dave
 

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Well I'm sure there could be many reasons for this, but maybe your motor is just slowly dying.:confused: You have had a years worth of abuse on it already with the S/C. Just a thought bro.

Razor.
 

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You probably put alot of wear on the motor since you originally installed it. I am sure you didnt put a S/C on just for looks so I know you run the hell out of it almost DAILY dont you? Check your compression, you may have lost some. Maybe a ring job will get you back up in #'s. Also, if you put a non catted pipe on, I guarantee your Air/Fuel is out of wack and needs to be re-calibrated if you havent done it already.
 

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blowngt said:
and I also went from 17" wheels to 18" wheels.
What is the width of the tires? I lost 5rwhp going from stock tires to 315/35/17 drag radials. Spent way too much time tracking it down as it was a very consistent loss and I hadn't changed anything else. Confused the hell out of me for a while....
 

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Discussion Starter · #7 ·
akatherazor4 said:
Well I'm sure there could be many reasons for this, but maybe your motor is just slowly dying.:confused: You have had a years worth of abuse on it already with the S/C. Just a thought bro.

Razor.
I thought about that as well, but I hope not. The car has 8200 miles on it, about 6500 of them after the supercharger was installed. It's not a daily driver (I bought the car in March of 2001). I have the new dyno sheet with the A/F ratio so I'll get it scaned tomorrow and post it so someone can help me read it. Also, I changed my plugs yesterday and went from Autolite 764's to Autolite 103's. I'll take a pic of the old plugs later (only about 1500 miles on those plugs) and maybe someone can see something from their condition.
 

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I maybe looking at this to simply but everyone is leaving out the most obvious, to me, thing. The weather. It could be the heat and humidity doing it. Just a thought.
 

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17" to 18" wheels might have effected it. Also, I would stop running those Autolite 764's and move to Motorcraft 12C or 22C. I've heard that the autolites are stock heat range.

Alot of other things could have affected your #'s as well like others have said: humidity the same? temperature the same between both dyno days? same boost? Lot of variables there. Also keep in mind that now with the longtubes that you're exhaust is much more free-flowing.
 

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You can't compare STD and SAE numbers, the correction factor makes a difference in final numbers!

joe
 

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Discussion Starter · #11 ·
Well I've decided that I'm going to change the plugs, install a new blower belt, and get it re-tuned. I was going to wait until I installed the Bullitt Intake, but now I'm not sure if I want to go in that direction before the rebuild.

I'll post the results, whatever I decide to do.
 
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