Got on the dyno, down on power - Forums at Modded Mustangs
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post #1 of 94 Old February 6th, 2013, 11:15 AM Thread Starter
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Got on the dyno, down on power

Got the car on a dyno after my cam install, and the numbers are pretty low. 250hp/260ft lbs. I should be at least 275hp, and over 290tq from what I've seen.

He showed me that there was a difference in fuel trim between bank 1 and bank 2 of 17%, so it would be pointless to try to get power out of it until it's fixed. It's not throwing any codes though, which is good... but makes finding the problem a little harder.

He got the idle and the driveability locked in, though. Full throttle AFR's are 12.1, it starts right up and idles at 800, runs really smooth and feels like it pulls harder than it did before I put the cams in, but the numbers on the dyno are definitely off. When I'm driving, I don't feel a miss or knocking or any breaking up. It's not blatantly obvious to me that there's an issue.

He thinks it's a spark problem and told me to put new plugs in and front O2 sensors because maybe I fouled them up by running the car untuned for a few days. But I don't know if that would make a 30hp difference. What else could cause a bank-to-bank difference in fuel trim like that? An exhaust leak on one side before the front O2 sensor maybe? I just want to cover all the bases before I go back and try again next week.

01 Bullitt #03179 | HP292s cams | 4.10s | Other stuff
87 GT 5.0L 5 speed | TW170's | Cobra intake
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post #2 of 94 Old February 6th, 2013, 11:29 AM Thread Starter
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The more I think about it, the more I think it's an exhaust leak on one side... probably from the x-pipe to header joint. What's an easy way to check?

01 Bullitt #03179 | HP292s cams | 4.10s | Other stuff
87 GT 5.0L 5 speed | TW170's | Cobra intake
04 Yamaha R1


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post #3 of 94 Old February 6th, 2013, 11:38 AM
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same dyno?

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post #4 of 94 Old February 6th, 2013, 11:40 AM
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One way to check is to have someone cover you exhaust tip with their hands while you listen for any leaks in the system.

If there's any leaks you should be able to hear it pretty easy.



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post #5 of 94 Old February 6th, 2013, 11:44 AM Thread Starter
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Originally Posted by me2dumb4college View Post
same dyno?
It's my first run, I don't have a baseline. But this shop tunes mustangs constantly, the tuner is very reputable, and he said I should be making at least 270hp at a minimum. He's gonna charge me next to nothing to run it one more time after I fix everything just to make sure.

01 Bullitt #03179 | HP292s cams | 4.10s | Other stuff
87 GT 5.0L 5 speed | TW170's | Cobra intake
04 Yamaha R1


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post #6 of 94 Old February 6th, 2013, 11:53 AM
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Try using throttle body cleaner it will burn white smoke so you should be able to find the leak
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post #7 of 94 Old February 6th, 2013, 12:00 PM
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List your engine mods that you and your tuner think should yeild 275/290.


12.25 @ 111 mph w/ CMS stage II cams
10.95 @ 119 mph NX 150 shot
6.96 @ 102 1/8th mile
Best 60', 1.43
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post #8 of 94 Old February 6th, 2013, 12:23 PM Thread Starter
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HP292 cams
Bullitt intake manifold (twin plate throttle body)
BBK CAI
BBK Underdrives
UPR offroad X
Flowmaster catback

This was on a Dyno Dynamics machine

01 Bullitt #03179 | HP292s cams | 4.10s | Other stuff
87 GT 5.0L 5 speed | TW170's | Cobra intake
04 Yamaha R1


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post #9 of 94 Old February 6th, 2013, 12:26 PM Thread Starter
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01 Bullitt #03179 | HP292s cams | 4.10s | Other stuff
87 GT 5.0L 5 speed | TW170's | Cobra intake
04 Yamaha R1


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post #10 of 94 Old February 6th, 2013, 12:27 PM
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Get rid of the flows for a straight through muffler
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post #11 of 94 Old February 6th, 2013, 12:29 PM Thread Starter
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I don't think my catback is causing my problem

01 Bullitt #03179 | HP292s cams | 4.10s | Other stuff
87 GT 5.0L 5 speed | TW170's | Cobra intake
04 Yamaha R1


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post #12 of 94 Old February 6th, 2013, 12:34 PM
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I didnt say it was the main prob but chamberes mufflers are restrictive compared to a straight through style. Do a tune up, change o2s, use fuel injector cleaner.
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post #13 of 94 Old February 6th, 2013, 12:40 PM
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Re: Got on the dyno, down on power

Still running stock exhaust manifold? Long tubes would probably help out a lot with those cams.

98 GT conv. PI intake, MHS stage III ported PI heads/Stage 3R Bullet Cams,
JLT RAI, 90mm MAF, BBK 78mm TB,
LT headers, Mac o/r prochamber,
FRPP underdrive pullies, FRPP 4.10's,
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post #14 of 94 Old February 6th, 2013, 12:41 PM
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Re: Got on the dyno, down on power

Cover exhaust tip with hands huh? They would have to be pretty hardcore that shit is really hot.

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post #15 of 94 Old February 6th, 2013, 12:44 PM Thread Starter
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Just pulled a plug out of curiosity, of course it's a Motorcraft OEM

I'm pretty sure they're the original, because it's brown and the electrode is almost gone

Damnit... all that work putting cams in and I didn't think to change them!

I feel stupid now lol

01 Bullitt #03179 | HP292s cams | 4.10s | Other stuff
87 GT 5.0L 5 speed | TW170's | Cobra intake
04 Yamaha R1


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post #16 of 94 Old February 6th, 2013, 12:45 PM Thread Starter
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He says to run NGK TR6's gapped at .38

Damnit, I still can't believe I didn't even think about changing the plugs before going

01 Bullitt #03179 | HP292s cams | 4.10s | Other stuff
87 GT 5.0L 5 speed | TW170's | Cobra intake
04 Yamaha R1


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post #17 of 94 Old February 6th, 2013, 12:45 PM
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Did you degree the cams
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post #18 of 94 Old February 6th, 2013, 12:46 PM Thread Starter
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Quote:
Originally Posted by AdaBoNGT View Post
Still running stock exhaust manifold? Long tubes would probably help out a lot with those cams.
Stock manifolds, yeah

But I think I'm gonna put some longtubes in before I go back for another run

This tune is fine for every day driving until I can get everything tuned up

01 Bullitt #03179 | HP292s cams | 4.10s | Other stuff
87 GT 5.0L 5 speed | TW170's | Cobra intake
04 Yamaha R1


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post #19 of 94 Old February 6th, 2013, 12:47 PM Thread Starter
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Originally Posted by Cobra123089 View Post
Did you degree the cams
No, but if the cam timing was out of spec he would have been able to tell me

01 Bullitt #03179 | HP292s cams | 4.10s | Other stuff
87 GT 5.0L 5 speed | TW170's | Cobra intake
04 Yamaha R1


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post #20 of 94 Old February 6th, 2013, 12:48 PM
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Re: Got on the dyno, down on power

Quote:
Originally Posted by ham sandwich View Post
Stock manifolds, yeah

But I think I'm gonna put some longtubes in before I go back for another run

This tune is fine for every day driving until I can get everything tuned up
Just remember you are going to need a shorty mid pipe with the long tubes. Or you could cut/Fab up your current one.

98 GT conv. PI intake, MHS stage III ported PI heads/Stage 3R Bullet Cams,
JLT RAI, 90mm MAF, BBK 78mm TB,
LT headers, Mac o/r prochamber,
FRPP underdrive pullies, FRPP 4.10's,
SLP LM1, built 4R70W 4000 stall.
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