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Discussion Starter · #1 ·
Hello All,

first post here!!!

All accounts of below info is @ the race track on closed runway.:)

Here is my issue i have a 12 gt auto with 3.73gears boss intake C&l Cai and offroad h pipe no cats..and handling mods. Ever since i installed my 3.73 gears i have been hitting rev limiter at 135mph and car will back off. This is not a normal top end speed as far as i know, the other day i was able to get up to 150mph but 90% of the time i can only get to 135 so myself and my tuner are stumped. I have been well passed 160 before the gears change at the runway track. So what could be wrong something maybe in the tune? what speeds do you guys get to with 3.73 or 4.10 gears? i have put a link to my you tube video showing it. thanks everyone

2012 gt mustang rpm cut off - YouTube
 

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Did your tune change the speedometer output reading? Is the speedometer/tach giving you the true speed? The higher gear ratio you have from stock is making your driveshaft spin faster for a given RPM; this makes the cars computer think it's going faster than it really is. I'm guessing your speed is off around 25 MPH (going from a 2.73 to a 3.73 as an example).
 

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Back to the tuner then. If you could reach the speeds before, and the tuner changed for the rear gear, and lifted the top speed (yes?), then the tune has to be at fault.
 

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I have a 93 race tune on my 2012 GT with 3:73 gears and I've hit 155 mph on a open track and my rev limiter never comes on since the tune, so it has to be the tune not turning off the limiter!!
 

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Discussion Starter · #9 ·
Who's the tune by? Data logging your car and submitting that to your tuner may help correct your issue.
I use steeda Gus, i always get great tunes with no issues from him, but for some reason we are having this issue. He contacted SCT to have a look at it also i hope we get it fixed soon or i will have to drive to steeda to do-it in person. Thank you all for your insight.
 

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I use steeda Gus, i always get great tunes with no issues from him, but for some reason we are having this issue. He contacted SCT to have a look at it also i hope we get it fixed soon or i will have to drive to steeda to do-it in person. Thank you all for your insight.
Have you tried returning it to stock and check your limiter then?
 

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Discussion Starter · #11 ·
Have you tried returning it to stock and check your limiter then?
No i didn't try to return to stock, because i have to many mods and i am afraid it will not run correctly. But i was able 1 time to get to 150 on this tune and setup. Its like it hits redline before it can shift to 6th, i must have been at a lower speed different gear to do that.

I am waiting to see what sct says now
 

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Discussion Starter · #13 ·
update

Here is an update to issue i will try it tonight when i get to tthe track and let you know if it worked.
Tom, I’ve had some expert minds from SCT and other sources look at the file, none of them are seeing a "smoking gun" in this one. All of the rev limiters appear in order and we are not sure how the shift would be affected, but what we did notice based on the shift schedule is when you punch it at 85MPH, it looks like (if the RPM reference is correct) that it will downshift to 3rd gear. I then have it set up to command the upshift to 4th around 102mph. That might be the coincidence we are looking for. It may be that after the downshift to 3rd, not enough time has elapsed to command the 3-4 shift and the computer can’t react fast enough.

Is that what is happening is that you are downshifting to 3rd at 85mph? If so, the fix may be to change the downshift points so that it will downshift into 4th at 85mph and not 3rd. I have spent the better part of an hour reworking the entire shift strategies, converter lock ups, torque reductions, etc.
I want you to try this file here and see how it behaves. Let me know.
 

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Here is an update to issue i will try it tonight when i get to tthe track and let you know if it worked.
Tom, I’ve had some expert minds from SCT and other sources look at the file, none of them are seeing a "smoking gun" in this one. All of the rev limiters appear in order and we are not sure how the shift would be affected, but what we did notice based on the shift schedule is when you punch it at 85MPH, it looks like (if the RPM reference is correct) that it will downshift to 3rd gear. I then have it set up to command the upshift to 4th around 102mph. That might be the coincidence we are looking for. It may be that after the downshift to 3rd, not enough time has elapsed to command the 3-4 shift and the computer can’t react fast enough.

Is that what is happening is that you are downshifting to 3rd at 85mph? If so, the fix may be to change the downshift points so that it will downshift into 4th at 85mph and not 3rd. I have spent the better part of an hour reworking the entire shift strategies, converter lock ups, torque reductions, etc.
I want you to try this file here and see how it behaves. Let me know.
Just in case I come across this problem, how did it turn out?
 
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