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Too Slow

 
ccmustanggt99
New User
Posts: 18
Joined: 10/07
Posted: 05/07/09 08:24 PM

I have a 99' GT with 70k on it and all I have done to it myself is an off-road Xpipe, SLP loudmouth exhaust and BBK Cold air intake. The trouble I'm having is my car seems to top out at 120mph......from what I've read 99-04 GT's should top out around 140 maybe 150. Could there be a speed limiter or a governer on there? If so how do i take it off or return it to stock? Confused  

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Michael Johnson
Enthusiast
Posts: 397
Joined: 12/07
Posted: 05/08/09 05:43 AM

Ok, I don't even want to know where you are trying these top speed runs, but yes, you should be able to break 120 mph. What gear are you running in at that speed? Is the top speed limited by aerodynamics, or RPM? In other words, is the RPM flat out, or do you have RPM left, but the car won't go any faster. Are you the original owner of the car? Do you know if the rear gear has been changed?  
Michael Johnson
Associate Editor
5.0 Mustang and Super Fords

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ccmustanggt99
New User
Posts: 18
Joined: 10/07
Posted: 05/12/09 12:28 AM

Yes, I can't say that where I am doin these runs are perfectly legal, but it is on a very long stretch of road with no hills. Ok back to your question. I'm in 5th gear. Not much is changed with my aerodynamics, I've added a 99 Cobra bumber cover, and a Cervini's Stalker Hood. I have plenty of RPM's left. I know I'm not at Redline. And no I'm not the original owner, I bought the car used in 02 with 32K on it from a dealer. There were no said words on if the car had upgraded gears or not, nor a tune of any kind.  

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Michael Johnson
Enthusiast
Posts: 397
Joined: 12/07
Posted: 05/12/09 06:05 AM

Ok, if you have a stock gear in the car, what may be happening is in 5th gear the engine may not have the torque to gain RPM, and reach a higher speed. If the engine was more in its powerband, it would be able to achieve a higher speed. Does the car feel like it's cutting out at 120 mph, or does it feel like it can't get over that speed? You need to find out what gear is in the car, and maybe find a dyno that you can make a couple runs to see if the car will in fact surpass 120 mph. If it will do it on a dyno then you know your is aerodynamically challenged, and unable to achieve a faster speed. At that point, a higher numerically rear gear would be a good idea to get the engine more in its powerband when in 5th gear.  
Michael Johnson
Associate Editor
5.0 Mustang and Super Fords

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ccmustanggt99
New User
Posts: 18
Joined: 10/07
Posted: 05/12/09 08:13 PM

Well my car has no problem accelerating easily to this speed of 120, the engine does seem to be hindered once I reach 120 though, like its hitting the cut-out point where the engine shuts off. It kinda makes a bogging down sound. I do plan on getting my car on the dyno and possibly tuned for my exhaust and cold air intake, if this doesnt create a problem. Besides going to a dyno how would one find out if they have different gears in the car? I dont have the money to make passes on the dyno at Brenspeed near where I live at the time. Thanks for the help.  

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Michael Johnson
Enthusiast
Posts: 397
Joined: 12/07
Posted: 05/13/09 05:13 AM

Ok, it is possible someone prior to you put a speed limit on the car. If the engine feels like it's cutting out, it's probably cutting out fuel and timing - like a rev limiter. If the car doesn't have a chip in it, the speed limiter could've been added using a handheld tuner. It's a good idea for you to have one anyway so I would start shopping for a handheld tuner. It will be a good investment for you.
As for the gears, you need to get under the car to see if the tag is still attached to the differential cover. If it is, I believe it will have the gear ratio on that tag. If the gears have been changed, the tag is probably not there since everyone usually throws it out when they change gear ratios. If the tag is not there, you'll have to resort to turning the driveshaft, and comparing the rotation of the driveshaft compared to how many times the tire rotates. It's not as scientific or 100-percent accurate, but it's the cheapest way to figure that out. you can also try finding another 99-04 GT, and compare your engine RPM with that car. Good luck.  
Michael Johnson
Associate Editor
5.0 Mustang and Super Fords

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ccmustanggt99
New User
Posts: 18
Joined: 10/07
Posted: 05/14/09 08:54 PM

Ok thanks I'll look into those here over the weekend. I do plan on getting a tuner b4 taking my car to the stang doctors at Brenspeed. but not sure what to get....so many choices. I'm thinkin SCT or a DiabloSport tuner. Thanks for the help.  

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Michael Johnson
Enthusiast
Posts: 397
Joined: 12/07
Posted: 05/15/09 05:16 AM

For the handheld tuner, I would go with whoever Brenspeed uses. If that's who's going to be working on the car, go with who they use. They may sell both, but check and see. Either one you choose will be perfect.  
Michael Johnson
Associate Editor
5.0 Mustang and Super Fords

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99gtstang
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Posts: 2
Joined: 01/10
Posted: 01/11/10 01:11 PM

i can tell you that aerodynamics is definetly not the problem. my stock 99 gt easily hit speeds of at least 150. i swapped to 3.73 gears last year and now my top speed is in the range of around 120 so that could be a possiblity. hope this helps you out a bit  

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