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Really.. really low dyno pulls - 07 GT500 123mm/tune

6K views 40 replies 18 participants last post by  JamesBrown 
#1 · (Edited)
Really not sure what all to say about. I know the dyno is JUST a tuning tool, but I had very reasonable expectations going in this morning. I'll start with the car first:

'07 GT500 (31k miles)
JLT 123mm
VMP tune (tune for 127, not sure if that matters)
FRPP 3.73
Moser street axles

Pre-dyno maintenance:
Fresh 5W-50 Motorcraft oil
TR6IX gapped .035 (not my first choice, but original plugs were in it and were bad)

Dyno:
Dyno Dynamics, which seem to run ~13-15% lower than a dynojet

Air temp:
Humid 80 degree morning

Numbers (best of 4 runs):
388/365 :frown: pulling in 4th

Low GT500 dyno - Album on Imgur

Soo, not sure what to say about it. Again, i know it's a tuning tool but the torque curve is shockingly low, and this is totally ignoring the fact that I expected to make in the 440 range on this dyno.

You can see from the dyno a/f bung, it was a very solid line in the 11's afr. Seems a little rich I guess, but nothing crazy, just nice and safe.


Other potential variables:
Little bit of gear whine and maybe some rotational vibrations from the rear, as well as some unhappy noises during sharper parking lot turns. I haven't gotten to spend a lot of time looking into it. Maybe need to check the rear for shavings :shrug:

Dyno owner was a little surprised at the numbers too. "What do these things make stock again?"

Moving forward:
Maybe need to check compression? Car seems to run fine, and gas mileage isn't great, but not awful. Nothing really pointing to an injured or lowered comp motor. My average speed per tank always settles around 25-27mph with a mid-lower 15's mpg for a tank. That seems about right for basically all city driving and 3.73's.

I also added a pic of the plugs I pulled out of the car. Cyl 4 & 8 on the backside were pretty gross, and especially #4. Plugs 2-3 were pretty oily, with a mild coating around the tops of each. Nothing visible around the electrode area, and the car doesn't smoke.

Also overlaid (somewhat) my dyno over a stock car on the VMP dyno. Not good.


Super frustrated with the car, as I really bought the thing to not mess with it much and yet, here I am doing all this work to get it to stock GT500 levels.
 
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#2 ·
Air/fuel ratio in the 11's is not rich.

You'll have to do some investigating to find the problem. I'd start with checking the engine's health with a compression test. I'd also get the tune dialed-in for what you have on the car.
 
#3 ·
Yeah, I'm more than a little afraid of what i'll find checking compression, but I can't worry too much yet. Judging by how 'basic' the car is, I don't know that i'd be all that surprised to find something awry in the test.
 
#4 ·
How fresh is the gas and could have any Stabil in the tank? Also, dyno results vary based on a number of physical factors of the dyno itself (such as proper maintenance).

If those two things aren't a factor, maybe data log and send to VMP?
 
#5 ·
Fuel was all fresh, it's basically my DD. One thing to note I guess was that I popped the low-fuel light right when I was getting to the dyno. Does the ECM treat anything differently in that condition? Also had traction control on (I assume the operator didn't turn it off).

One thing I do want to check on is get the operator to send me a couple other graphs of some vehicles I can get a good baseline on from recently. Things pulled in the last couple weeks, etc and then I can see if other known quantities like LSX cars, etc are also looking on the low side.

Data log is a good idea. I really really don't think it's tune related, and probably a combination of other factors, but worth checking on.
 
#6 ·
If it sensed wheel spin on the dyno, traction control could have cut fuel/applied brake.
Never get in boost with low fuel. On the dyno, it could run lean, pull timing. On the street, fuel can leave from the fuel pickup, bad things can happen.
 
#8 ·
That's true. Had some wheel-spin issues the very first pull of the day, so then he jumped to pulling in 5th (showed 363) that pull. I assumed everything was all good after that. Definitely should have filled up, oversight on my part for sure.


I wouldn't base too much on one dyno run. Fill that gas tank full (of good 91-93 premium) and find a different dyno.....if the results are still low, then start investigating. It's like getting a second opinion before doing surgery. :)
Unfortunately this was the best of 4 pulls. Amusingly made a little more each pull. First was a 5th gear, measured 363, then a 372 and then a 384 (i think). Maybe I should have done another 20 pulls to make the rest of the power I was missing 0:)
 
#10 ·
My understanding of the two intakes is that the actual airflow of the two are so close that the tuning doesn't matter, but hell, hopefully i'm wrong.
 
#12 ·
Another thought... Did you by chance know what your IAT2 number was? If it was high for whatever reason, your computer would pull timing resulting in low power.

The traction control could definitely have been a problem if your wheels were slipping on the dyno, but a lower fuel level should not have been. On the street, you run the risk of fuel sloshing aft in the tank during hard launches possibly exposing the fuel pickup to air, but since you were not moving, you had adequate fuel available unless you were basically empty. This is why you'll hear: "stay out of boost with less than 1/4 tank," which is smart when out driving.
 
#15 · (Edited)
Never go on a dyno without datalogs.

Your car (if healthy) will make 425-435 sae at sea level on 93 on a Dynojet all day every day bone stock.

Cold air and tune= 500
Add a 2.50 and its 530

We've done hundreds and hundreds of 07-09 and IF they're healthy they are all the same (+/- 5pct).

Use TR7-IX plugs next time. That is not your immediate issue but what you are using are incorrect and should be gapped at 032.

You don't have knock sensors so it wasn't pulling timing for that. High downstream temps can pull half your timing. None of the things you cited (gear tension, etc) will drop noticeable power.

11.2-11.7:1 is absolutely perfect.

Rich for your car is lower than 10.9:1

If you bought the tuning from us, we have a qualified team of techs available on the website at vmpperformance.com and the Customer Support tab.

I just happened past here. So if you need assistance and questions answered, please contact us.

The JLT 123/127 use exactly same data

Sent from my SM-G935V using Tapatalk
 
#17 · (Edited)
Slowly backing off the ledge. Compression was all pretty aiiight

1 - 178
2 - 178
3 - 179
4 - 178
5 - 170
6 - 178
7 - 178
8 - 175

Tested the lowest cylinders 5 & 8 twice. 5 stayed solid, but 8 bumped from 171 to 175. I assume as the motor was getting colder.

Not sure what other cars come back with compression wise, used a harbor freight compression checker that i've had for a few years now. Mostly concerned about consistency across cylinders and they're all within a healthy range IMO.

Sooo, now? Guess i'm going to tighten up that plug gap a touch, button it back up and talk with VMP, maybe grab a couple street pull datalogs. Car runs pretty strong, but glad that it looks like it's not immediately pointing to motor health. so it's time to work back through other variables. The dyno itself probably being the largest unknown
 
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#21 ·
Feels strong on the street, especially when outside temps/humidity drop a bit. I can't always blow away the tires in 2nd, sometimes it'll scramble for traction a bit but it'll mostly grip and go. Dyno itself could be low, just talked to VMP and going to grab a couple logs, but probably end up booking a different dyno as well as trying some 1/4 passes to assess a trap speed. Ykno, or run down a Camaro or something

Put it on a DJ and I would have somebody pull some fuel out. Anything sub 11.5:1 is on the rich side IMO. My 07 made 445std with a cheap cai and stock tune.
Was just looking into other dyno options, seems like a few other in the area. Delk is close-ish, but they using a Mustang and another local place uses a Dynocom. If the car doesn't make power on a dynocom, then it won't make make numbers anywhere lol

And this is why BJ/VMP is da place ta go. :rocker:
Lee
Totally is, just had a good chat with Travis. Going to grab a couple logs and at least get them looked over. Need to grab a damn wideband for this stupid car (damn you 2007 technology!)
 
#29 · (Edited)
Small/unhelpful update: Intercooler pump definitely works, it was like a hot tub in that little Moroso tank when I popped the lid off.

Placed an order for a lower temp thermostat, and while I was at it I went ahead and picked up an '08+ crank pulley, and VMP 2.4/90mm/pulley tool. :shrug03:

edit: We need a build-thread section around here



Oh nice, that's good to know as well. I'll try to plan for that accordingly.
 
#32 ·
Just noticed your in the Nashville area where did you get your car dyno? I had my car dyno at NMRA Bowling Green by VMP when I did my mods if you can wait until September that's where I would go. My car heat soaked a few times on the dyno but Justin let it cool down between pulls. Shortly after that I purchased the VMP dual fan heat exchanger and that made a huge difference. Good luck sorting it out as VMP are awesome to work with.
 
#35 · (Edited)
Figured i'd keep this thread rolling along as I work towards expected numbers.

Got a Roush boost/vacuum gauge installed over the past few days (takes me a little while to get wiring/line routing to my liking) and had a few questions around expected boost/vacuum delivery over load/rpm's.

Vacuum:
First startup when the car is cold i'll idle around 1k and pull -18 vacuum and at the ~750 base idle I'll be right around -19 (and some change). On throttle close cruising around, i'll pull -20-21 vacuum.

Booooost:
First, I left my hose a little too long so I could route it correctly, and do need to shorten it. On initial lower RPM WOT, boost will jump 0-5psi almost instantly, and then push to ~7 4-5k(ish) and around 6k it'll be creeping close to 8psi. In much cooler temps last night it was creeping up on 9.

Weather is quite humid here and ~90 when making a more detailed account of the boost delivery.

Is this sort of behavior expected? Naturally, the stock inferred boost gauge basically pegs straight to 9psi all the time without much of a climb. Maybe I need to check the connections for the gauge?
 
#37 ·
Booooost:
First, I left my hose a little too long so I could route it correctly, and do need to shorten it. On initial throttle cracking open boost will jump 0-5psi almost instantly, and then push to ~7 4-5k(ish) and around 6k it'll be creeping close to 8psi. In much cooler temps last night it was creeping up on 9.

Weather is quite humid here and ~90 when making a more detailed account of the boost delivery.

Is this sort of behavior expected? Naturally, the stock inferred boost gauge basically pegs straight to 9psi all the time without much of a climb. Maybe I need to check the connections for the gauge?
This does NOT sound normal if I am interpreting what you are saying correctly. Your boost shouldn't jump on "initial throttle cracking" and be 7+ at 6k unless you are standing on the gas pedal. If you are getting boost when just cruising around, something is amiss. Not sure if that's what you meant with your description or not.

Boost is a function of demand (stand on pedal and demand to go fast now) and not a function of rpm (no set boost per rpm).
 
#36 ·
Sounds about right for stock supercharger and pulley.


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#39 ·
Much better update this time.

Literally didn't change anything. Swapped spark plugs for some cooler SP471 Motorcraft and ran the car on an actual dynojet. A humid 90deg inside the shop and pulled 525/518.

Pulled up some results from other intake/pulley/tune GT500's and we were all ~5-8whp of each other, across many years of dyno'ing these cars.
 
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#40 · (Edited)
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