Pontiac Firebird 1967-2002 - Speed limiter

Hey guys i have a 98 trans am that according to the door code it came with z rated tires but it wont go faster than 120 mph !
Ls1 no mods 6 speed 3.73 gears ! Whats the deal my wifes 98 t/a automatic climbs well above 120

If it came with Z-rated tires then the stock speed limiter should be 162mph.... If no Z-rated tires then it will be 118mph.... You may not have the stock ECM in the car and was swapped with a car without Z-rated tires.

A handheld programmer can fix this i believe. I just bought a Hypertech and there is a option for this.

Kuhny, Welcome to LS1tech! SEARCH will be your best friend around here.

3.73 gears are certainly not stock so that car has at least that modified.

What RPM's are your turning at your 120MPH?

In 5th @ 125mph "its 5mph or so off" its only around 4000 rpms or so . But i can take 1st through 4th 6000 rpms

What speedometer is in this car?

155 mph

Just.... wow.

That is the rating of your tires, not the limit of the car.

It wont run faster than 120 mph
Its limited for some reason Ive had my automatic ta speedo buried guessing 160 mph 2.73 gears

Paul Bell asked which speedo was in my ta i said 155 mph

It wont run faster than 120 mph
Its limited for some reason Ive had my automatic ta speedo buried guessing 160 mph 2.73 gears

163 is the limit...that is set in the computer. Not your tires. And just on a side...it is very very irresponsible to go that fast on public roads.

I was on an old air strip never said i was on a public road. And if the car didnt come with z rated tires it was computer limited to 118 mph if equiped with z from factory 162 mph limit

It is very irresponsible your right but your mom loved it!!!!!!!! ;)

Just.... wow.

That is the rating of your tires, not the limit of the car.

The max speed of the car set in the PCM was determined by what tires originally came with the car from the factory. The Z rated tires were part of a package that included the higher MPH speedo.

Kuhny, if your speedometer is indicating the correct speed (EG: It reads 50 when you're traveling at 50) the PCM's ratio is correct but it's from another vehicle with the lower max speed set.

Alright man i appreciate it . Which programer should i buy? to do away with this.

The Hypertech Max Energy will allow you to move the Top Speed to the speed rating of the tires. If you raise it all the way up it will take it to 255mph,which you will never see.

Ok thanks guys for all the info . Check out my vids on youtube 22kuhny