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Lower than expected horsepower with supercharger

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Old 04-12-2012, 07:06 PM   #1
jason999
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Default Lower than expected horsepower with supercharger

Hello,

I have 2001 auto convertible vette. Its was stock with a magnaflow catback. I installed an A&A Vortech with a 3.6" pulley. It made a little better than 370 horsepower on a Mustang dyno. The tuner seemed disappointed that he couldnt get more out of it without detonation. He said that it wouldnt take timing like most.

What are your thoughts? I had 93 octane fuel. He suspected that the catalytic converters could be in poor condition.

How would you know if the cats were bad?

The kit made around 10 lbs of boost. Is my power unusually low? All thoughts on my horsepower and ideas on the cause welcome......
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Old 04-12-2012, 07:23 PM   #2
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Originally Posted by keck739 View Post

How would you know if the cats were bad?
Backpressure test using a tech2 (or whatever is the most recent software GM uses now). It gets plugged into the 02 sensor before the cat and then you go for full throttle runs to get readings. You'd have to do both sides. Do you have any connections at the local Chevy dealership? Someone should be able to hook you up.

The other alternative is to gut the cats and re-dyno.
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Old 04-12-2012, 07:28 PM   #3
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Your horsepower numbers are low, my car made 534hp/476tq at the wheels with a 3.6 pulley at an altitude of 5,500ft. Did you replace your stock fuel injectors?
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Old 04-12-2012, 07:33 PM   #4
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Your numbers are not just really low they are crazy low even for a mustang dyno.

How does the car feel?
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Old 04-12-2012, 07:35 PM   #5
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Its an A&A...





and yes, the power is low, even for an A&A!!!!!
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Old 04-12-2012, 07:58 PM   #6
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Originally Posted by 2003VETT View Post
Its an A&A...





and yes, the power is low, even for an A&A!!!!!
It's nice to see someone else stir the pot for a change, but you just got to your computer before I did!
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Old 04-12-2012, 08:09 PM   #7
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Get him to email you the tune and post it here. Do you remember how much total timing was in there? Something else is definitely wrong. Even if you are only running 10* of timing 10 lbs is a significant amount of boost.

Time for some headers.
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Old 04-12-2012, 08:38 PM   #8
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Find a new tuner !
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Old 04-12-2012, 08:55 PM   #9
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I replaced the injectors with 60the lbs and i have a bap. The car feels fast. I left black marks at 30the mph or so in an auto. The tuner seemed to expect 400 hp. We got 381 corrected.....

What should my car make on a mustang dyno?
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Old 04-12-2012, 09:34 PM   #10
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Quote:
Originally Posted by keck739 View Post
I replaced the injectors with 60the lbs and i have a bap. The car feels fast. I left black marks at 30the mph or so in an auto. The tuner seemed to expect 400 hp. We got 381 corrected.....

What should my car make on a mustang dyno?
Any codes?
Maybe just for the heck of it, take it to another dyno.

Last edited by Shirl; 04-12-2012 at 09:38 PM.
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Old 04-12-2012, 09:34 PM   #11
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Quote:
Originally Posted by keck739 View Post
I replaced the injectors with 60the lbs and i have a bap. The car feels fast. I left black marks at 30the mph or so in an auto. The tuner seemed to expect 400 hp. We got 381 corrected.....

What should my car make on a mustang dyno?
If your leaving black marks at 30 MPH then the car is making more power then 380 at the tires.

Post your tune, up here if you can and go run on another dyno. My old vette was sitting at about 420 it was a 100K mile engine with some early 1997 LS1 heads that were hand ported and a cam. No supercharger or anything like that. It would pull like a freight train but It wouldn't catch rubber from anything over 15MPH.

However your car should be able to lay rubber at highway speeds.
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Old 04-12-2012, 09:40 PM   #12
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Low numbers.
Try a different tuner and dyno.
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Old 04-12-2012, 10:33 PM   #13
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Thanks for all of the replies. I trust the tuner and i dont care about getting big numbers. I just want to get the power that i should. Another dyno run would be great for comparison but i dont have quick access to one. What have others made on a mustang dyno?

Im leaning hard toward xs power headers and high flow cats. I was just curious if anyone had other thoughts....

Car is much faster. When up in boost it will start spinning even before it shifts. Can spin at higher speeds like around 30-
50mph. I dont know exact speed but thats a good guess....

What would a dynojet normally show for 380hp on a mustang? I had heard 450rabbet or so??
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Old 04-12-2012, 10:36 PM   #14
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Plugged cats ?? That will kill power for sure....
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Old 04-12-2012, 10:36 PM   #15
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Quote:
Originally Posted by mmartinez View Post
Your horsepower numbers are low, my car made 534hp/476tq at the wheels with a 3.6 pulley at an altitude of 5,500ft. Did you replace your stock fuel injectors?
What other mods?
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Old 04-12-2012, 10:42 PM   #16
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just got my 02 back today from having Magnuson TVS2300 installed along with Kooks headers and catted X pipe. It is making 477 RWHP and 535 Ft# of Tq. at 10# of boost on a Mustang Dyno. Would be more except had to take timming out at higher rpm due to maxing out the fuel pump.
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Old 04-12-2012, 11:12 PM   #17
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Quote:
Originally Posted by BUBBAS 01Z06 View Post
Plugged cats ?? That will kill power for sure....
So if its thegood cats and i put test pipes on would i need to change the tune or would it be safe and faster with this tune?

Car has 65k miles btw and no codes. Is it still likely to be cats?
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Old 04-12-2012, 11:31 PM   #18
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Quote:
Originally Posted by Milan View Post
Get him to email you the tune and post it here. Do you remember how much total timing was in there? Something else is definitely wrong. Even if you are only running 10* of timing 10 lbs is a significant amount of boost.

Time for some headers.
Quote:
Originally Posted by Sponge Vette View Post
Find a new tuner !
For sure something is wrong and if that tuner cant find it you need a new one. Even on a mustang dyno per say they run about 10% to 12% lower than is still way to low..... NEW TUNER....Robert
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Old 04-12-2012, 11:44 PM   #19
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For sure something is wrong and if that tuner cant find it you need a new one. Even on a mustang dyno per say they run about 10% to 12% lower than is still way to low..... NEW TUNER....Robert

Tuner felt like it was the cats. Sorry for crazy wording on some messages..... big fingers on little smart phone.
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Old 04-12-2012, 11:44 PM   #20
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Default low dyno numbers.

Your car with a properly installed [email protected] kit, with long tube headers and cats would make 450 on a mustang dyno since your car is automatic. I have an automatic 2000 which was dynoed on a mustang dyno and it dynoed 460 without my cam and my exhaust modification. I had hi flow cats and during the dyno session it was laying down some and all of a sudden it shot the guts out of the cats through the exhaust pipes!! I have the debris to prove it. gutted cats, new cam, rev kit, dyno tune 525 rwhp on mustang dyno.. went to dynojet dyno...570rwhp. automatics dont dyno well because 3rd gear never really locks up. sticks dyno better because they place it in third and go! dont worry, you will run right with a stick and if you race, they always screw the shifts up anyway. You win!
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