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  • 1996 - 2004 SN95 Mustang -General/Talk-
  • SN95 4.6L Mustang Tech

Weird power loss on dyno

  • Thread starter Thread starter Flysquirrel29
  • Start date Start date Oct 27, 2011
F

Flysquirrel29

New Member
Oct 27, 2011
4
0
0
Oct 27, 2011
#1
  • Oct 27, 2011
  • #1
***I posted this in the Mach 1 forum too... I don't think that's against the rules, but if it is please let me know and I'll delete***

Okay. So I HAD a 2004 Mach 1 until I put a P-1SC on it (8#s) and promptly threw a rod through the block... talk about carnage. I'll try and upload pics that'll make you laugh at me or cry for me as soon as I figure out how to. Rebuild went well (or so I thought):

-Old teskid block, had it honed and cleaned up.

-8.8 manley pistons

-h-beam manley rods

-Re-used heads

-Re-used crank but had it polished and balanced

-Valve job (replaced bent valves on number 4 and the machine shop said the rest were good... later I found out that shop has a less than perfect rep)

-Had the whole thing balanced from the harmonic balancer to the pressure plate.

-Built it using the factory disc and all the specs for an '03 cobra.

Then I dropped it in and drove 500 miles with break in oil without even coming close to boost. Changed to 5W30 synthetic and drove another 500 miles. Changed oil again and threw her on the dyno.

Now I have 39# injectors and I tried to go up to a 3.5 inch pulley (10 to 12 pounds of boost I think) and the guy tuning it said probably going to need 42 pounders. Set that aside for now, not the issue.

Did the initial fuel curve, everything looked fine, then went for a full power run. Made 9.7 pounds boost at 5800 rpm and ONLY 285 HP?!?!?!?! Then the boost climbed steady all the way to 11 or so at 6500 and between 5800 and 6500 RPM it dropped almost 100 HP.

I am totally stumped. Any and all help would be much appreciated.
 

trinity_gt

10 Year Member
Jan 31, 2003
3,125
81
99
Canada
Oct 27, 2011
#2
  • Oct 27, 2011
  • #2
What was the fuel pressure doing during the run? Got AFRs?
 
F

Flysquirrel29

New Member
Oct 27, 2011
4
0
0
Oct 27, 2011
#3
  • Oct 27, 2011
  • #3
AFR

I'm at work, left the print out at home... will post as soon as I can.
From memory... 11.5ish at 5800?

Fuel curve was still a little rough because it was early in the tune, but it was a little rich and hadn't started to lean out yet. Like I said it's probably going to need bigger injectors, but that doesn't explain the power loss when rpms and boost is still climbing steady, and power and tourqe look like they fell off a cliff.

Valves floating?
Bad valve springs?
Plugged Cats?

I'm going to comp and leak down test it this weekend and see what I get... just seems so underpowered from what it should be.
 
2

2002BLGT

Well-Known Member
Dec 18, 2003
2,945
4
59
Bedford VA
Oct 27, 2011
#4
  • Oct 27, 2011
  • #4
Flysquirrel29 said:
I'm at work, left the print out at home... will post as soon as I can.
From memory... 11.5ish at 5800?

Fuel curve was still a little rough because it was early in the tune, but it was a little rich and hadn't started to lean out yet. Like I said it's probably going to need bigger injectors, but that doesn't explain the power loss when rpms and boost is still climbing steady, and power and tourqe look like they fell off a cliff.

Valves floating?
Bad valve springs?
Plugged Cats?

I'm going to comp and leak down test it this weekend and see what I get... just seems so underpowered from what it should be.
Click to expand...

Saw a guy recently left a rag in his intercooler , I have also seen numerous Procharger intercoolers split apart after a short period of time for no reason as well , Mach1s dont have IMRCs so that takes that out of the equation , you didnt leave a rag in the intake did you LOL , what plugs are you running and what are they gapped at ? Were the cams degreed ? Compression test would be my next move.
 
F

Flysquirrel29

New Member
Oct 27, 2011
4
0
0
Oct 27, 2011
#5
  • Oct 27, 2011
  • #5
Gap

Gap is 34 if I remember correctly, i'll pull the plugs tonight and see if they have oil on them. They are as cold as I could buy at NAPA, i'll look at a box and post the exact number later. No idea on the cams... just took it to the shop and said fix 'em up. Starting to seem like I made a poor choice in machine shops.
 
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