Top Speed

I don't know about the rest of you, but when I found out that my 99 GT had the gutless top speed of 108, I was disgusted. Does anyone know what kind of top speeds a minimully tinkered with Grand Prix (GT or GTP) can achieve with the speed limiter removed? With the strength of the engine, I would think that it could hit 135 with confidence. Does anyone know why GM limited GP's to such a weak top speed? Insurance reasons maybe?

A little not-so-fun fact: If you look at the back of a Motor Trend magazine (or it could be Road & Track) where they list the stats of cars they've tested, they've got the stats of a 99 Grand Prix GT listed with the top speed of 108 highlighted with an asterict next to it. If you read the notes at the bottom of the page, it states that anything with that particular asterict means "uncommon results," or basically "uncommonly slow compared to anything else we've tested." That's almost as embarassing as my spelling.

I do believe you could hit 135 with the reprogrammed pcm, this also get rid of your rev limiter and speed limiter.

Grand Prixs don't have a governer that you can disconnect, they have mini computers that tell them what to do, if you get a reprogrammed pcm then it will take care of this problem.

this guy is just upset cause he can't afford a grand prix and is stuck driving a ford ranger

hahahahahhahahahah

do you know who even makes bentley......go back to your tickle me elmo site little kid

jjubeck, I lost U here.

DarkTint: OEM speed for the GP is set up tp be 120mph. Why, because of the tires that it comes from factory. The speed limit can be removed reprogramming the PCM(ECU). IN my case the fastest I have driven my GTP was 145MPH and the car still had more juice to go by, just that I did not push it further. If your car just reaches 108 then check what is holding it. I only read Road & Track when new models come out but deffinetly I know that they are biased(corporate brives from Japan or Europe, not sure and is a shame)towards anything that is not american made. I really love what this great country has to offer and the great automobiles it can produce...

Sorry there was a guy in here yesterday that was talking crap about Grand Prix's, and cursing out the moderators I guess they took his posts out.

Well I know with my 99 gt it does have a rev limiter and the damn thing wont go over 108. There is plenty of pedal left in it and I'm only at about 3000 rpms by this time. The new pcm should fix this though.

128 here gtp

Is the 128 with the limiter or without?

with, I have a stock pcm, It dies as soon as the heads up says 128 it cuts out

my 98 gtp used to cut out at 108 too.

fast, rock said 128mph not 108mph. I think you should check your car PCM. It is not normal to stop accelerating a 108MPH

Only if he was still in 3rd gear

Well, yes but usually when looking for high speed you would not stick the shifter on 3rd(I assume he did not). Basically what I do when racing instead of play with shifting I use the performance shifht to start and after 75 I realease it so it do not fall back for more torque but keep pushing on high gear for higher speeds(even tought would have less acceleration).

----''fast, rock said 128mph not 108mph. I think you should check your car PCM. It is not normal to stop accelerating a 108MPH"----

kilroypr, dude, i know what he said..and i said 108..it was a comment to everyone, not necessarily a reply to the previous message. i know that im not the only one that had their gp to cut out at that speed. some gps were limited to that speed. the pcm was set at that. and it didnt matter what gear it was in. i dont know if it was something that iv heard or read but i think it depends on the period it was built---somewhere around 98-99model years

I want to know how fast my car will go after i get a digital pcm!? Im running a 3.4 pulley, CAI, 8mm wires with autolite 104 plugs, 160 degree therm, Ubend and resisnator replaced with straight pipe, flowmaster mufflers. What do you guys think i will be able to do with these mods. top speed.

just wondering

My guess would be about 150.

rock, i have basically the same setup as you. i was doing about 135 when my engine light came on for some reason but had plenty of juice to keep on going. so yeah, 150 is a good guess

Did you ever find out why your check engine light came on? Did the light turn off after you slowed down?

I have a GTP and my speed-o goes up to 110, so if i were to max out, and when i peeked at 110mph on the speed-o, would my OHD continue to show increasing speed?

When u hit the limiter its like killing the power. Your car should not increase in speed.

sweetness, yeah me ses light comes on to sometimes at high speeds also, I dont its that big of a problem... probably a misfir again... ive checked before on the tech 2 and it said something about a miss fire on #2 and #5 Cylinders. so who knows. I dont speed past 90 that often anyways only when racing, seeing its winter.. i got sno tires on and spd rating it 99mph anyways...no point of racing either

bigfootkevin are you asking if you HUD(head up display) will keep going up? that is a yes... I dont know what OHD is. So i figured you were asking about the HUD

bigfootkevin are you asking if you HUD(head up display) will keep going up? that is a yes... I dont know what OHD is. So i figured you were asking about the HUD


lol, yes, sorry i dunno why but i was trying to call it the over head display.

Darktint, it's just like what rockford0384 said about the light..it was a misfire for me too. no problems now tho. i had to get autozone to scan it and erase the code for the light to go off

When the ses light came on sometimes a could pull over right away turn my car off and let it sit for about 3 minutes and start it back up and it would go away (ses light) but if i drive with it on at high speeds for a while, it takes about 1 to 2 days till it turns off itself when going at lower speeds. about 2-3 hours worth of running/driving.... fyi thought you might want to know

sorry to bump this kind of old thread, but does anyone know where i could get a chip for my 98 gt?

DHP

http://www.pfyc.com/store/merchant.mv?Screen=PROD&Store_Code=PFYC&Product_Code=GP3012&Product_Count=0&Category_Code=GPUNDER

thanks for the link. damn thats expensive.
i was wondering if anything here would have the same results:
http://search.ebay.com/search/search.dll?cgiurl=http%3A%2F%2Fcgi.ebay.com%2Fws%2 F&krd=1&from=R8&MfcISAPICommand=GetResult&ht=1&SortProperty=MetaEndSort&query=grand+prix+chip
mainly i just want to top speed increased and i dont know if anything there would actually improve that

I have been able to pump 147mph on my car. It has so far Thrasher CAI, 3.4" Thrasher Pulley, 180 tstat, 8mm wires, Leaking Exahust Manifold(LOL) and the SES has come on when racing and usually is misses. Got to reset it with scan tool thought

i have a stock 1999 grand prix gt sedan that i've had up to 127 and it didn't cut out but didn't wanna push it any farther

i have a stock 1999 grand prix gt sedan that i've had up to 127 and it didn't cut out but didn't wanna push it any farther


:eek7:

Did you buy it new? Are you sure it's stock? My 99 GT Coupe is limited to 108. :banghead:

i bought it used, so i was trying to figure out if it's been modified, but i haven't taken out the pcm, so i might do that today and see what i've got, but i did have it up to 127 according to the HUD and it still had a little left in it.

lucky...

anything on ebay that would boost top speed? that chip is pretty expensive

ok not to brag but my 2004 comp g has a 140mph speedo and i burried it the day i test drove it (salesman wouldve loved me for that) i believe thats all the pcm would allow. the specs say my car will reach 142 and the regular 04 gtp's are 126. Also i want to point out that there are many fibbers in this forum. Now im not saying any names or calling anyone a lier but seriously no one in this forum will like or dislike you more depending on what it is that you drive and or own so STOP! And just a tip but yes pcm are set up from the factory on the speed rating of the tires it comes with from the factory(for safety) However a pcm cant see you so if you change tires, such as snow tires nobody cares including your pcm in turn your car will go just as fast(i wouldnt recomend it though) pcms are very smart but not that smart.

And just a tip but yes pcm are set up from the factory on the speed rating of the tires it comes with from the factory(for safety) However a pcm cant see you so if you change tires, such as snow tires nobody cares including your pcm in turn your car will go just as fast(i wouldnt recomend it though) pcms are very smart but not that smart.

Still, you canna' change the laws a' physics! If the tires won't grip, you won't go as fast.