Hey guys. So I just got my new performabuilt tranny and stall put in. Car shifts great and seems to be running great other than the fact that it feels way down on power above 5krpm and mostly just once I hit 3rd gear.

My mods are
K&N CAI
1.6 rockers
918 springs
ls7 lifters
36# injectors
CC306 Cam
Stock heads with a 5 angle valve job and mild porting
Longtubes
3"ory
magnaflow catback (no cats)
performabuilt lvl 2 4l60e
performabuilt 3200 billet converter (1.69 STR, the tightest one they offer)
3.73 gears
PCM4less tune

That pretty much sums it up.

Here are a few of the things that I think might be contributing to this, in no particular order. Let me know what you guys think. (Mind you, it seems slower than stock from 80-100)

1) Stock unported throttle body
2) Stock fuel pump
3) lack of a dyno tune

 

your stock fuel pump could very well be killing it. When my car felt flat on top, i came find out i had around 20 psi of fuel pressure at 5000 RPM and in the mid 15's for WOT AFR's i would get a fuel pressure gauge on it as soon as possible. my 17 year old stock fuel pump apparently got weak and couldn't supply enough fuel for a bolt on car

 

Back to basics, log some data and see what isn't working. If nothing there, then the tune is off. Don't overlook simple stuff like plugs & wires, fuel filter.

What does it do, just run out of steam? kind of stop accellerating? Is it the same in all gears?

& check what the guy above said.

 

It pulls, but nowhere near as hard as it should. I just went out for a run with my buddy to see if I was just imagining things. He has an 03 Mustang, full bolt ons, 5 speed, full suspesnion, 9psi kenne bell blower. He traps 118 in the quarter and he just ate my lunch, big time. His DR's were helping him too, but he pulled on my like a freight train after I got through most of second gear. Third gear he was gooooooooone.

The fuel pump was my first thought. When I check the pressure, do I need to have an in car mechanical gauge to check it out?

Also, what's the best way to check plugs and wires?

For logging info from the PCM, what software do I need to get and where can I get a cable?

Thanks for your help guys.

 

It just doesn't seem to pick up much faster than it did when it was stock with 2.73 gears and a CAI with the muffler deleted.

 

You could do some checks of the FP when its just idling with the vacuum line off and see if it is low, or if it's healthy and it just doesn't have enough volume for ***** out, that is a different matter and you need to tape the gauge to the windshield or something or get it on a dyno and monitor it with a gauge.

For plugs and wires you are concerned with worn out plugs with too big a gap and rounded out center electrodes or else too hot a heat range (detonating) and if your wires are stressed and misfiring you would probably notice it breaking up - you might be able to spray it in the dark and see some sparks indicating they are leaking through the insulation.

Logging software - well there's freescan, PCMCOMM, and Datamaster which all need a cable which you could get at AKM cables or else on the for sale forum where I see them all the time - careful if you get one with serial port and don't have an old lappy - they have USB versions as well. And of course you need the laptop to get the data - anyone serious about tuning his car has one of these setups, but you also gotta know what the hell you're doing too...

And last but not least, if you lost to a blower car, too bad, I'd kill you, too

 

Bingo!

 

bkpliskin:
The car needs to be data logged with Freescan or Datamaster. Since the PCM doesn't have fuel pressure logging won't help with that but it will show ignition timing and if the PCM sees evidence of detonation. If the PCM sees knock it could easily be pulling 10 or more degrees of timing advance and that will make top end very weak. As has been mentioned, check the plugs. Especially if they are platinum tipped. The factory plugs are notorious for shedding those pucks and your spark gap may now be .020" to .040" bigger than you originally set and it would have a similar effect to what you describe.

 

How old is the fuel filter? It's cheap to replace.

 

Regarding logged data, if he's really running lean, it might show high short term and maybe long term fuel trims and/or fuel injector pulsewidths maxing out as it tries to add fuel.

 

Thanks for all the input guys.

I'm testing the fuel pressure with a windshield taped gauge on tuesday and will also be replacing the fuel filter.

The plugs are NGK TR6's and the wires are just summit wires. They both have about 1,000 miles on them.

I am also running the LT4 KM, so I would hope that my engine wasn't sensing that much knock.

KevinBlown95TA - I will be able to claim an N/A victory over this KB Mustang soon enough. He had the advantage of running DR's, 5 speed, dyno tuned and has a fully adjustable suspension. He traps 118 in the quarter. I'm running a stock headed, stock bottom end, stock suspension, 4 speed auto N/A LT1 that has not been dyno tuned and is running cheap khumo's and a potential fuel/spark problem. We went from about 30-35 up to 115 or so and he pulled about 5 cars on me. I have plenty of room for improvement.

 

I'll also be getting freescan and a usb cable for my laptop. These are things I should have anyway, having owned and been modding an F-Body for 5 years now.

 

Thanks for the input guys. I tested the fuel pressure and it was the problem. At idle I've only got 40psi and at WOT it drops as low as 20-25psi. I ordered my new 255lph pump and it will be here tomorrow, just in time for me to do the trap door mod and have it running great for my first ever trip to the drag strip on Saturday.

 

yeah that's exactly what my fuel pressure looked like when i noticed it running flat on top, glad you found out your issue

 

How much power do you think it was robbing me of, given where the pressure should have been, where it was acutally at and my mods?

I'm working on finishing up the trap door swap right now.