FordGeek dyno's and mods his GT500

Discussion in '2007 - 2014 Shelby GT500 Tech' started by Uncle Meat, Jul 24, 2006.

  1. "Ladies and Gents,

    I'm an enthusiast, but not a purest. I have a hair over 250 miles on my car and I've done the dirty deed; I've made some modifications. First, let me start by saying: PLEASE NO FLAMES! I'm posting reality here folks, not what FORD might have told us. There, I said it and it was like therapy - on with the results.

    Today, I worked with the folks from Strictly Performance here in Houston to swap out my gear. First thing, always, is a baseline dyno run. They have one of the more current models of the dynojet. Some folks think that the method utilized by this dyno tends to underate horsepower; regardless, the numbers are usually pretty close whether you use a dynojet, or a Mustang (another type of dyno). We pulled 3 runs in 4th (standard stuff) soon after I arrived at the shop. The relative humidity was high - about 87% (hey, this IS Houston), and the intake air temerature was running at a whopping 98.4 degrees. This kills some power, so I was expecting to see anywhere between 415 - 430 horses at the wheels. Keep in mind that stick shifts usually have a 15% parasitic loss in the drivetrain; add some serious heat to that and you lose a bit more. I saw the dyno thread that someone posted earlier. Many of your thoughts around 450 - 460 hp at the wheels are simply not realistic; but it sure would have been nice. The best of the 3 runs was as follows:

    HP: 412.9 Torque: 409.2

    These are good, but definitely NOT what I expected; even with the heat. However, one thing that immediately was obvious is that this puppy pulls like a mule right until the rev limiter kicks in and everthing shuts down (between 6,250 and 6,500 rpms). Given that at the higher RPM the engine was still increasing horsepower output, I felt that the 4.10 gearing I was planning on installing was going to make a difference. Basically, my thoughts were that the power/torque curve would shift to the left (steeper gears get you in the sweet spot of the rpm range sooner). I've enclosed some pictures of the install for your pondering.

    BTW...while we were installing the gear, I felt it appropriate to change out the exhaust. The stock mufflers are simply too quiet for me! I want to HEAR the power. I chose the Flowmaster American Thunder 2-chambers for the job. I have them on my Terminator and love the way they sound; I have some pictures of the before and after from the rear of the car. I think it looks pretty sweet; and, of course, they sound amazing with the 5.4 liter!

    After, the gear and exhaust install (which took a total of around 2 hours), it was back to the dyno. We only ran it twice, and the best run was...can I get the envelope....

    HP: 446.5 Torque: 421.9

    Now that's what I'm talking about! If you do the math, this equates to around 525 crank horsepower; 25 more than what this bad boy comes with. And folks there's more good news, the horsepower was still climbing!!!! Oh crap I could have pissed on myself, especially after I saw that the air intake temperature was at 104.2 degrees! It's amazing that we could pull those numbers, with that kind of heat. The only bad thing is we don't know which of the two modifications caused the spike in power because we did them both at the same time. I have a small video clip of the dyno run below; I'm standing in front of the car and you can hear my new exhaust sing to me. Robert, I may need help if it's too large for me to upload to my post.

    For those of you that have your Shelby's, the gear change fixed the "problem" we've been experiencing with the little jiggy the car does coming out of first. I think it was simply a bog given the lower than needed gearing.

    And now I have some general observations that you may find interesting now that I've inspected my car from top to bottom:

    1.) Forger about changing the lower pulley to increase boost There is a nub on the water pump that's only a hair from the crank pulley. In my opinion, it's going to have to be machined in order to accomodate a larger crank pulley. The aftermarket may figure it out, but I just don't see a way around the nub. Of course, you could change the pulley, but the stocker is just barely big enough to clear the ribs on the supercharger snout; it's going to be nearly impossible to use a smaller blower pulley without changing the whole snout itself; which by the way will most likely set you back $800 - $1,000. With the terminators, swapping a blower pulley was a ten minute job using the extractor tool, and usually set you back $120 - $130 (includes buying the extractor tool). Again, someone may come up with a way, but I've worked on cars long enought to know it isn't a trivial matter.
    2.) My speedometer will display higher than actual readings due to the gear change. This will go away as soon as my boys at Strictly get the algorithm template and we can begin to tweak the engine.
    3.) The front fascia does indeed have the mountings for an aftermarket break cooling kit. I have a picture below of what the mounting extension looks like. All you'll have to do is punch out the pattern through the fascia and you'll be sucking fresh air in no time.
    4.) If you change gears, you most likely will need a new pinion bearing. The stockers are on there like an SOB and we ended up breaking ours. No problem though, it's usually good practice to swap them out during any gear change. Other than that, the switch went smooth as butter.
    5.) In my opinion, the mufflers are the real reason the car doesn't quite deliver straight off the showroom floor. Their big, heavy, and seem to be designed to reduce noise, not increase power. I have a picture of them outside the car. Besides, the flowmasters are coated black so they look much stealthier than these loud ass brass looking things.
    6.) FORD has tuned the Shelby very nicely. The oxgen/fuel ratios never devidated between 11.8 and 12.4 all the way through the dyno pull. This is a very safe range; but I'd like to see it run just a bit leaner and see how the car responds.
    7.) KILL THE CATS!!! As soon as we can begin calibrating the computer, the Cats are coming off. During the last dyno run I could tell the car was struggling to breathe in and especially out. The air filter assembly is hideous and a cold air kit will defintely do wonders. The Cats are just to damn big and holding back a lot of power.

    I tried to capture everthing I could. If anyone has questions, just post a response and I'll help if I can. The bottom line is, these care are defintely going to push past the 600 hp mark. It's only a matter of a few months before that's exactly where I expect to be. Until next time...this is the Geek signing off."

    Original Thread:
  2. Wow- if they did that well with Flowmasters- cant wait to see what will happen when you put an even better muffler on one-
  3. Man wish i could have one, I only have a v6 :(

  4. Just find a really steep hill in your area, drive to the top of it, turn around pointing downhill, and giver your V6 hell. If the hill is steep enough, it'll feel just like a GT500. You should be able to find a recording of GT500 exhaust sound at full-throttle going through the gears online fairly soon (if not already), and you can burn a CD to play for the appropriate sound effects.

    Problem Solved!! :p ;)
  5. Ricks your my hero LOL that is great. :D :rlaugh: :lol:
  6. can you post the dyno graph? I would like to see the HP/torque curves....

  7. I'd like to see the results when people, including Richard at Strictly, start messing with the Silver Oak processors in the GT500. Before I make the leap on one of these cars, I want to see, besides the price go down, what kind of numbers (track times and dyno) these things will get with minimal mods.

    I hope somebody has saved all the old threads where people were speculating as to the GT500's performance (and potential) -- interesting to see who is/was right and who has to eat some *****.:D
  8. to funny :lol: :rlaugh:
  9. Thanks for the posting Uncle Meat! Good to see someone is doing the research for those of us who ar planning on buying and driving the hell out of one of these beasts. As soon as the speculators get done paying 15k + over sticker I will find a way of putting one of these babies in my garage. Even if i have to wait for a used one.
  10. Thanks man, this is the kind of info I have been waiting for. This helped me to decide to get a GT500 for sure, they just have to make at least one more model year of her or I get one used but who would be the fool to let one go for even sticker after its used?...
  11. Man I wish my Gt put out that kinda of power