David's GT500 Troubleshooting Thread

Alright David....thought we could come together to figure this issue out. Please post in detail the events leading up to last nights results at the drag strip. Maybe we can put our heads together and come up with some ideas on what the issue is.

Clogged cats was one possibility....and I found this quote on another forum for those that dont think you can melt/clog the factory exhaust.

"I had my 08 GT500 blow the cats...I had recently upgraded the blower pulley and all that goes with it...was launching down a freeway on ramp at WOT when it looked like a chalk bag had just exploded behind the car...turned out it was ceramic particals and dust...pulled the cats off and they were falling apart...I bought the car with 558 miles on it and the guy mostly just idled around...I am sure it was running rich and burned the cats..."

Clogged cats would allow the RPMs to rise, but feel like the car isnt really going as fast as its supposed to.

One possibility anyways

Send me that datalog file if you got it, want to look at it.

Well, ok.

1. Took the car to the drags before any mods to get a baseline. Result with DR's was a 12.8@110

2. Added 2.59" pulley, 08 style Balancer, 90mm idler, C&L CAI and tunes from Justin at VMP. Took the car back to the track after the mods and on the same DR's went a crappy 12.9 & high 13 at 108 ish. Clearly something was off with the car.

3. Thought I may have accidentally loaded my 91e10 ethanol tune and retuned the car. It seemed to be running better? So back to the track I go Friday night. One pass which netted only a 13.2@109.8 clearly something still off. Not worried about the ET but the mph being indicative of my HP numbers which should be around 520-540 RWHP with my mods. The trap speed is more like that of a car producing about 300RWHP.

So now after data logging the car I will send the results to Justin for a look. However, if it was a detrimental tune issue Im pretty sure I'd be throwing codes. I have not thrown one code. This leads me to believe something else is to blame. I thought clutch? But the clutch is not slipping. The blower belt isn't slipping. My voltage is strong both at idle and under acceleration. So now I'm really just running out of possibilities. The cats being clogged is a possibility? I'll know after tomorrow. The car only has 7500 miles so it's not that. I just changed the plugs to the TR6's and the stock plugs looked good. No excessive meltdown, discoloration, etc.

So. Let's hear it. Anyone got any viable ideas?

Leonard 95 wrote:Send me that datalog file if you got it, want to look at it.

Whats your email address? I will send you:

1) Idle to 6k (neutral rev)
2) 3rd gear pulls (there are 2 of them)

Double post ftl!

07Shelby500 wrote:Double post ftl!

What double post?

Yeah. Mr. I deleted my double post.

07Shelby500 wrote:Well, ok.

1. Took the car to the drags before any mods to get a baseline. Result with DR's was a 12.8@110

2. Added 2.59" pulley, 08 style Balancer, 90mm idler, C&L CAI and tunes from Justin at VMP. Took the car back to the track after the mods and on the same DR's went a crappy 12.9 & high 13 at 108 ish. Clearly something was off with the car.

3. Thought I may have accidentally loaded my 91e10 ethanol tune and retuned the car. It seemed to be running better? So back to the track I go Friday night. One pass which netted only a 13.2@109.8 clearly something still off. Not worried about the ET but the mph being indicative of my HP numbers which should be around 520-540 RWHP with my mods. The trap speed is more like that of a car producing about 300RWHP.

So now after data logging the car I will send the results to Justin for a look. However, if it was a detrimental tune issue Im pretty sure I'd be throwing codes. I have not thrown one code. This leads me to believe something else is to blame. I thought clutch? But the clutch is not slipping. The blower belt isn't slipping. My voltage is strong both at idle and under acceleration. So now I'm really just running out of possibilities. The cats being clogged is a possibility? I'll know after tomorrow. The car only has 7500 miles so it's not that. I just changed the plugs to the TR6's and the stock plugs looked good. No excessive meltdown, discoloration, etc.

So. Let's hear it. Anyone got any viable ideas?

whats happening with the cats tommorow???

Supersnake wrote:

07Shelby500 wrote:Well, ok.

1. Took the car to the drags before any mods to get a baseline. Result with DR's was a 12.8@110

2. Added 2.59" pulley, 08 style Balancer, 90mm idler, C&L CAI and tunes from Justin at VMP. Took the car back to the track after the mods and on the same DR's went a crappy 12.9 & high 13 at 108 ish. Clearly something was off with the car.

3. Thought I may have accidentally loaded my 91e10 ethanol tune and retuned the car. It seemed to be running better? So back to the track I go Friday night. One pass which netted only a 13.2@109.8 clearly something still off. Not worried about the ET but the mph being indicative of my HP numbers which should be around 520-540 RWHP with my mods. The trap speed is more like that of a car producing about 300RWHP.

So now after data logging the car I will send the results to Justin for a look. However, if it was a detrimental tune issue Im pretty sure I'd be throwing codes. I have not thrown one code. This leads me to believe something else is to blame. I thought clutch? But the clutch is not slipping. The blower belt isn't slipping. My voltage is strong both at idle and under acceleration. So now I'm really just running out of possibilities. The cats being clogged is a possibility? I'll know after tomorrow. The car only has 7500 miles so it's not that. I just changed the plugs to the TR6's and the stock plugs looked good. No excessive meltdown, discoloration, etc.

So. Let's hear it. Anyone got any viable ideas?

whats happening with the cats tommorow???

David just so happens to know someone with a factory midpipe he can borrow for testing.

Dont know who this angelic like person could be to help with such a noble cause....

Shelby10' wrote:

Supersnake wrote:

07Shelby500 wrote:Well, ok.

1. Took the car to the drags before any mods to get a baseline. Result with DR's was a 12.8@110

2. Added 2.59" pulley, 08 style Balancer, 90mm idler, C&L CAI and tunes from Justin at VMP. Took the car back to the track after the mods and on the same DR's went a crappy 12.9 & high 13 at 108 ish. Clearly something was off with the car.

3. Thought I may have accidentally loaded my 91e10 ethanol tune and retuned the car. It seemed to be running better? So back to the track I go Friday night. One pass which netted only a 13.2@109.8 clearly something still off. Not worried about the ET but the mph being indicative of my HP numbers which should be around 520-540 RWHP with my mods. The trap speed is more like that of a car producing about 300RWHP.

So now after data logging the car I will send the results to Justin for a look. However, if it was a detrimental tune issue Im pretty sure I'd be throwing codes. I have not thrown one code. This leads me to believe something else is to blame. I thought clutch? But the clutch is not slipping. The blower belt isn't slipping. My voltage is strong both at idle and under acceleration. So now I'm really just running out of possibilities. The cats being clogged is a possibility? I'll know after tomorrow. The car only has 7500 miles so it's not that. I just changed the plugs to the TR6's and the stock plugs looked good. No excessive meltdown, discoloration, etc.

So. Let's hear it. Anyone got any viable ideas?

whats happening with the cats tommorow???

David just so happens to know someone with a factory midpipe he can borrow for testing.

Dont know who this angelic like person could be to help with such a noble cause....

I see another 1am night. Call if you need some help.

Go off road "H" pipes.

They dont make an H pipe for the GT500 unfortunately. Although the new 2011s come factory with them. 07-09 come with X's

Correction: Looks like MRT makes one. Might be worth a try David if this is fact the issue.

I sent a email back to Jawwad a config file for datalogging, same file Justin sent to me. Really need to know the spark (timing) and iat's, at least that will let us know if timing is being pulled in higher rpm's.

The mrt one is just one you cut the x part out and install the h-pipe part, nothing to do with cats.

This is a good one... Like mentioned above. I doubt the cats are clogged given the low miles. Spark plug (which was my problem) have been replaced. No codes, etc.

The problem is somewhere within the data log. Too bad we didn't data log at the track on Friday.

Really dyno would be the best bet right now, get er done!

Really dyno would be the best bet right now, get er done!

Double post again

double post!!

double post ftw!

Double Post FTL!

Double Post FTL!

Shelby10' wrote:They dont make an H pipe for the GT500 unfortunately. Although the new 2011s come factory with them. 07-09 come with X's

Correction: Looks like MRT makes one. Might be worth a try David if this is fact the issue.

I believe the 2008 GT500KR came with an H-Pipe out of the factory.

Well, to eliminate some variables we removed the stock mid pipe today to see if the cats may be choked off. Very hard to tell so the factory mid pipe was converted to an off road unit. Lol

Car sounds good. Hard to tell if it made a difference in power. Made a couple spirited runs out in wagoner county after the modification and it felt strong. I'll need a retune for the removed cats, then most likely back to the track or to the dyno to look at the parameters. Still have a set of FRPP 373's sitting in the garage waiting to go in.

ShelbyJosh'09 wrote:

Shelby10' wrote:They dont make an H pipe for the GT500 unfortunately. Although the new 2011s come factory with them. 07-09 come with X's

Correction: Looks like MRT makes one. Might be worth a try David if this is fact the issue.

I believe the 2008 GT500KR came with an H-Pipe out of the factory.

Sort of...it wasnt an actual one piece H pipe. They basically did what MRT is selling. They cut the factory X out and welded up an H. Shelby does that in house.

Anyone else want to see about scheduling some dyno time at vangs? I'm sure we can get a group deal.

Oh and just in case anyone is curious the IC pump is working fine.

i might be up for it. id like tp compare numbers on a dyno jet to the dyno dynamics. would help me greatly in comparisons of my gains to others(right now i think im ahead of others in gains from comparable parts)

David, get us some info and pop out a new thread. I might be up for this also!

Id be down for a dyno day.

David I posted your issues on another forum and got some feedback.

http://www.fordgt500.com/forums/showthread.php?t=9733

"No failsafes, no codes, right? Bad cat wouldn't do that and he'd had to have used some kinda badass gas to blow them up that quickly. Now that you've gutted them, does his tune have the downstream sensors turned off? If not, he'll be getting a check engine light soon. No biggie, but he needs to have them turned off and Justin's tunes do not have them off (generally). Has he checked:

All CAI connections, including the sleeve to throttle body....check the underside of the clamp
How much boost is he making? The factory gauge should be around 12psi at sea level
Does he have the MAS installed in the correct direction into the CAI? (It happens)
How do you know the clutch isn't slipping? Have you put it in 3rd and nailed it?
If all of the above are in line as they should be, pull the battery cable and let it sit for 30 minutes. Hook it back up. Re-load the tune (you don't need to go to stock first).

Start the car.

Let it idle for 1 minute. Turn on AC and let it idle 1 more minute. Turn off AC.

Take it out on the highway....4th gear, starting at 3000 rpm and nail it. If it doesn't show 12-13 psi, datalog it and send it off to Justin again.

Worst case scenario, throw on the stock airbox and tune and take it to the dealer. That really is the WORST case. You don't want to do this if you don't absolutely have to. They'll know it's modded because of the idler pulley even if you have the "stock look" upper.

Keep us informed. (My money is on the intake and if so, he's running way lean and needs to stop racing it til it's fixed. Go to a dyno and get a proper a/f.)

bj"