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Old 01-22-2020, 03:15 PM   #1
Boxer1687
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Default Speed limiter removed?

Does anyone know if thereís a way to remove top speed limiter on a late 90s Impreza. Fuel cuts at 110MPH. Around 4800RPM.

1998 Impreza OBS 5-speed manual.
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Old 01-23-2020, 02:34 AM   #2
WoodsWagon
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I don't think most of the 90's non-turbo ECU's had any aftermarket tuning support, so changing the speed limiter at its source isn't an option. You could put an interrupt switch in the VSS input signal to the ECU. That will cause a code & check engine light and will make the car more prone to stalling if you coast up to a stop and push the clutch in, but it may also eliminate the speed limiter. Depends on what the default value was for a failed VSS input. Having it switchable would prevent the drivability issues, only cut the circuit when you're on a speed run.

Worth a try, the ECU's easy enough to get to under the passenger carpet and you can trace the wire from its appropriate pin at the ECU connector and cut it a couple inches back from the plug.

There's not much reason to be going 110+. Make sure your tires are rated for those speeds and are in good condition. Just saying.
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Old 01-23-2020, 12:56 PM   #3
Boxer1687
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Quote:
Originally Posted by WoodsWagon View Post
I don't think most of the 90's non-turbo ECU's had any aftermarket tuning support, so changing the speed limiter at its source isn't an option. You could put an interrupt switch in the VSS input signal to the ECU. That will cause a code & check engine light and will make the car more prone to stalling if you coast up to a stop and push the clutch in, but it may also eliminate the speed limiter. Depends on what the default value was for a failed VSS input. Having it switchable would prevent the drivability issues, only cut the circuit when you're on a speed run.

Worth a try, the ECU's easy enough to get to under the passenger carpet and you can trace the wire from its appropriate pin at the ECU connector and cut it a couple inches back from the plug.

There's not much reason to be going 110+. Make sure your tires are rated for those speeds and are in good condition. Just saying.
Hey thanks a lot. I was also thinking about putting a grounding switch to the speed sensor. Donít know much about electrical but thatís why I asked for options. My tires are 2002 Wrx rims and tires. If I plan to keep the car more time, I wonder how a 6 speed trans from a 04-05 Sti would do with this N/A engine. The trans on this revs too high at 65mph. Close to 3k. Feels like itís asking for a sixth gear. Love this engine. Most reliable engine Iíve had in all 6 Subaruís Iíve owned. 241k. Thatís why I only want to change the trans eventually. And rebuild the engine later. Trying to keep the RPM low.
Thanks again
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Old 01-24-2020, 12:59 AM   #4
WoodsWagon
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You can change just 5th gear without removing the transmission from the car. Rear transfer section needs to come off (shifter & driveshaft too) to get to them but it's doable. The 5th gearset out of a 02 WRX is a lot deeper overdrive.

Sti 6spd is $$$$ and not worth doing on a <300hp car.

Tire speed rating is shown in the code on the sidewall. https://www.tirerack.com/tires/tiret....jsp?techid=35
Another consideration is the age of the tire, which is stamped into an oval spot down near the rim on the sidewall of the tire. Often it's hidden on the inside-side of the tire because of how the tire was mounted on the rim, so you may have to crawl behind the tire and look with a flashlight.
https://www.tirerack.com/tires/tiret....jsp?techid=11

Hauling ass on old tires and beyond their speed rating is a recipe for disaster. If you have a blowout at 100+ it can be hard to correct quick enough to still be on the road by the time you regain control.
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Old 01-24-2020, 05:48 AM   #5
Boxer1687
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Quote:
Originally Posted by WoodsWagon View Post
You can change just 5th gear without removing the transmission from the car. Rear transfer section needs to come off (shifter & driveshaft too) to get to them but it's doable. The 5th gearset out of a 02 WRX is a lot deeper overdrive.

Sti 6spd is $$$$ and not worth doing on a <300hp car.

Tire speed rating is shown in the code on the sidewall. https://www.tirerack.com/tires/tiret....jsp?techid=35
Another consideration is the age of the tire, which is stamped into an oval spot down near the rim on the sidewall of the tire. Often it's hidden on the inside-side of the tire because of how the tire was mounted on the rim, so you may have to crawl behind the tire and look with a flashlight.
https://www.tirerack.com/tires/tiret....jsp?techid=11

Hauling ass on old tires and beyond their speed rating is a recipe for disaster. If you have a blowout at 100+ it can be hard to correct quick enough to still be on the road by the time you regain control.
Thanks you guys for your the options, didnít know you can even do that to the transfer case. I will carefully try that out.

My tires are but 6 months old and still have a lot of thread left. Canít do much driving without stopping in the city of Chicago. But when Iím on the country twisty roads is where it matters. (Miss the Colorado roads)
Again thank you guys. I have some homework to do 👍👍
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Old 02-04-2020, 06:46 AM   #6
Ronietta
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the trans, 96 legacy auto, has 2-speed sensors. the front one drives the speedo which then sends info to the ECU. the rear one is used to determine ''when'' more power is needed in the rear.

the speed limiter is in the programming of the computer, ECU. if you find out how to disable it, be sure to buy better tires, because the ones on the car are not rated for over 110 mph.
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