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95 Thunderbird LX
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So me and a few friends purchased a retired autocross car from a fellow competitor. It's a 95 Bird LX with the 4.6 with a plan to get it prepped for 24 hours of LeMons. Before we throw money into the cage work and other safety equipment we gotta sort out our speed issue first.

From what I can tell we have a Jet chip part number 75911 and I assume it should have the governor delete. I say assume, because the details I have read so far don't mention that being a part of what it does. Yet every post I see says most chips do remove the governor. With our gearing at 3.73 and shorter 255 40 17 tires we are probably right around the 80mph mark of governor cutout.

We have installed new plugs and wires. It runs like a champ all the way to 80mph no matter whether you are rolling gently on the throttle or punch it. It also has a shift kit in it.

Also just to list some other mods:

Shift kit is a TransGo AODE/4R70W-HD2

Jet Chip 79511

3.73 with LSD

Aftermarket torque converter

JBA 1626s shorty headers with no cats and I believe dual Magnaflows

Messy CAI that probably does more harm than good

Any help you may be able to provide would be great. We know the driveshaft needs attention for higher speeds, so that will be taken care of but I imagine we will probably top out at 110 on most straights. It's also not a street car, track only so we aren't running around trying to break the needle on the speedometer next to your wife's Camry. If there is a cheap or free way to rid ourselves of the issue, that's our best option. With LeMons, stuff has to be cheap, and a different $300 chip is not really a good option for us.

Untitled by hatchethairy, on Flickr

Untitled by hatchethairy, on Flickr

Untitled by hatchethairy, on Flickr
 

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The jet chip is crap. You will have to replace it with another with a proper tune to get rid of the speed limiter. Don’t worry about the cost of it, I have never seen them ask about tuning expenses at the BS inspection. As for the driveshaft, I think you will find that an issue sooner than you think. I ran a Cougar in Lemons for a while with a 5.0 and M5R2, which has a shorter driveshaft than the 4r70 and so a higher critical speed. When I ran 3.27 gears I was fine, but when I went to 3.55s, I broke the tail shaft off the trans due to the high speed vibration. Of course we were hitting almost 140 on the straight, so depending how your track is later out, it may or may not be a problem. Also you should seriously consider a manual trans swap. An automatic is OK for autocross where you basically lock it in 2nd gear, but on a real road course, that trans is going to drive you nuts.
 
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95 Thunderbird LX
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Discussion Starter #3
Track would be Heartland in Topeka which I imagine we would hit 115 at most on the front straight. Honestly I'm not sure if this car will be what we decide to run. We are planning to bring it to a private track day at Hallett in a couple months, but want to sort the speed issue first or it's just a waste. The idea is that we can all assess whether it's something we want to move forward on or get a different car entirely.
 

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The MN12 makes for a fun lemons car, but I can tell you from experience, it will never win. They are very heavy, and even with a ton of weight reduction, you will still be 500lbs heavier that the really competitive cars. You can offset that with more power, bigger brakes, and bigger tires, but buying 13” cobra pads and rotors and 275/40/17 tires every race gets expensive! If your goal is to have fun road racing a v8 powered car, then carry on. If your goal is either to be competitive, or to get into Lemons for as cheap as possible, then it is not the car for you.
 

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Discussion Starter #5
I think you are pointing out what we were beginning to suspect. I fear we are too competitive to run something this far from the pointy end and I prefer lighter more agile cars.
 

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So me and a few friends purchased a retired autocross car from a fellow competitor. It's a 95 Bird LX with the 4.6 with a plan to get it prepped for 24 hours of LeMons. Before we throw money into the cage work and other safety equipment we gotta sort out our speed issue first.

From what I can tell we have a Jet chip part number 75911 and I assume it should have the governor delete. I say assume, because the details I have read so far don't mention that being a part of what it does. Yet every post I see says most chips do remove the governor. With our gearing at 3.73 and shorter 255 40 17 tires we are probably right around the 80mph mark of governor cutout.

We have installed new plugs and wires. It runs like a champ all the way to 80mph no matter whether you are rolling gently on the throttle or punch it. It also has a shift kit in it.

Also just to list some other mods:

Shift kit is a TransGo AODE/4R70W-HD2

Jet Chip 79511

3.73 with LSD

Aftermarket torque converter

JBA 1626s shorty headers with no cats and I believe dual Magnaflows

Messy CAI that probably does more harm than good

Any help you may be able to provide would be great. We know the driveshaft needs attention for higher speeds, so that will be taken care of but I imagine we will probably top out at 110 on most straights. It's also not a street car, track only so we aren't running around trying to break the needle on the speedometer next to your wife's Camry. If there is a cheap or free way to rid ourselves of the issue, that's our best option. With LeMons, stuff has to be cheap, and a different $300 chip is not really a good option for us.

Untitled by hatchethairy, on Flickr

Untitled by hatchethairy, on Flickr

Untitled by hatchethairy, on Flickr
So me and a few friends purchased a retired autocross car from a fellow competitor. It's a 95 Bird LX with the 4.6 with a plan to get it prepped for 24 hours of LeMons. Before we throw money into the cage work and other safety equipment we gotta sort out our speed issue first.

From what I can tell we have a Jet chip part number 75911 and I assume it should have the governor delete. I say assume, because the details I have read so far don't mention that being a part of what it does. Yet every post I see says most chips do remove the governor. With our gearing at 3.73 and shorter 255 40 17 tires we are probably right around the 80mph mark of governor cutout.

We have installed new plugs and wires. It runs like a champ all the way to 80mph no matter whether you are rolling gently on the throttle or punch it. It also has a shift kit in it.

Also just to list some other mods:

Shift kit is a TransGo AODE/4R70W-HD2

Jet Chip 79511

3.73 with LSD

Aftermarket torque converter

JBA 1626s shorty headers with no cats and I believe dual Magnaflows

Messy CAI that probably does more harm than good

Any help you may be able to provide would be great. We know the driveshaft needs attention for higher speeds, so that will be taken care of but I imagine we will probably top out at 110 on most straights. It's also not a street car, track only so we aren't running around trying to break the needle on the speedometer next to your wife's Camry. If there is a cheap or free way to rid ourselves of the issue, that's our best option. With LeMons, stuff has to be cheap, and a different $300 chip is not really a good option for us.

Untitled by hatchethairy, on Flickr

Untitled by hatchethairy, on Flickr

Untitled by hatchethairy, on Flickr
Hi Captain, Ken here, I'm surprised you have the cutout at 80 mph however, it's likely the rear gear. I'm running a 4:10 rear gear and had the same concern. Although I corrected the speedo with a 23 tooth speedo gear, the PCM doesn't look at that. It looks at the OSS sensor which is telling the PCM that the car is going about 105 mph when it's really going 80. The Tbird PCM is programmed to cut the injectors off a 105 because of the tire speed rating. If you unhook the OSS sensor, you should be able to go above 80 mph however the tranny will shift funny. I used a Quarter Horse programable control to change the NVBASE from I think 42 to 57. This lets the PCM know 80 mph is 80 mph. This is a street/strip car that is going 100 mph at top end at this time. If I want to go faster, I'll have to change that number or I believe there's another table that can be set to make the speed limit to 127 mph (Mustang setting).
 

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Discussion Starter #7
Hi Captain, Ken here, I'm surprised you have the cutout at 80 mph however, it's likely the rear gear. I'm running a 4:10 rear gear and had the same concern. Although I corrected the speedo with a 23 tooth speedo gear, the PCM doesn't look at that. It looks at the OSS sensor which is telling the PCM that the car is going about 105 mph when it's really going 80. The Tbird PCM is programmed to cut the injectors off a 105 because of the tire speed rating. If you unhook the OSS sensor, you should be able to go above 80 mph however the tranny will shift funny. I used a Quarter Horse programable control to change the NVBASE from I think 42 to 57. This lets the PCM know 80 mph is 80 mph. This is a street/strip car that is going 100 mph at top end at this time. If I want to go faster, I'll have to change that number or I believe there's another table that can be set to make the speed limit to 127 mph (Mustang setting).
Ken,

Do you have a link to the Quarter Horse program unit or any info on how to get that done? If I could get to 100mph for now that would be glorious.
 

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You can look up Moates.net and that should get you there. There is software that has to be bought and a steep learning curve to program. I would think that you have an off-road car, just pull the OSS wire off. It might shift ok because with an OSS open circuit, it simply will use other tables to shift the tranny.
 

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Discussion Starter #9
You can look up Moates.net and that should get you there. There is software that has to be bought and a steep learning curve to program. I would think that you have an off-road car, just pull the OSS wire off. It might shift ok because with an OSS open circuit, it simply will use other tables to shift the tranny.
Thanks for the info! We will give the OSS disconnect a try first and see what happens.
 
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