charleslong
Member
- Joined
- Dec 14, 2001
- Messages
- 620
what would be a pretty good GUESSTOMATE on the top speed of a grand national? from the factory if it wasnt governed and with the mods he has?
what do grand nationals run tops
- Thread starter charleslong
- Start date
Welcome!
By registering with us, you'll be able to discuss, share and private message with other members of our community.
What mods are we talkin'?? I dunno what mine will run, honestly I wouldn't dare to find out, but with a mildly modded GN, putting maybe 350 hp to the flywheel, I'll bet these cars can run around 140 - 150 mph or so. I could calc. it out if somebody would give me the drag coefficinet (NERD ALERT!!). What is it for these cars, like around 0.33 or so??
I think they were governed at 125 or so from the factory, yes?
I think they were governed at 125 or so from the factory, yes?
somone had said the FBI got a chip w/o and gov in it and put an 87 T on a nascar oval and hit like 167mph with it.. but i dunno that is kinda high for a stock car.
then again.. once youve got enough power to run high 12s (which isnt hard at all) you could probably hit 160...
but like he said.. i wouldnt try it unless you had the right suspension parts and maybe the front of the car lowered to keep it from lifting.. but the back of the car will lift as well.. so you shouldnt really try any top speed runs unless youre going straight for a long long time
then again.. once youve got enough power to run high 12s (which isnt hard at all) you could probably hit 160...
but like he said.. i wouldnt try it unless you had the right suspension parts and maybe the front of the car lowered to keep it from lifting.. but the back of the car will lift as well.. so you shouldnt really try any top speed runs unless youre going straight for a long long time
Too fast for me!! 
I got mine up to 140 or so mph (according to the speedo in my buddy's '01 GT who was trying to keep up
) and I will never go that fast in it again until it gets some serious handling hardware. Very scary indeed. A stock suspended G-Body has no business going that fast, IMHO.
I got mine up to 140 or so mph (according to the speedo in my buddy's '01 GT who was trying to keep up
) and I will never go that fast in it again until it gets some serious handling hardware. Very scary indeed. A stock suspended G-Body has no business going that fast, IMHO.whitehot84
Well-Known Member
- Joined
- Jun 6, 2001
- Messages
- 6,097
140+
The reason the factory put the speed control in was because of the tires available at the time. They didn't want to assume any responsibility past that.
The reason the factory put the speed control in was because of the tires available at the time. They didn't want to assume any responsibility past that.
charleslong
Member
- Joined
- Dec 14, 2001
- Messages
- 620
cool guys, thanks for replying, where did you guys get the 140mph odometer? and how much did it cost?
charleslong
Member
- Joined
- Dec 14, 2001
- Messages
- 620
who is postons and does anyone have a pic of the dash?
thanks guys
thanks guys
Attachments
Re: 140+
Actually, there were tires available then with as high as a Z rating (149 mph+). These tires were used on the Corvette, the Camaro IROC's, and the Trans Am GTA's. Buick chose to speed limit the car primarily because of handling characteristics at speed without further mods, concern for long term engine life if ran at sustained high rpm under boost, and because of potential liability issues. The GNX got the Gatorback tires which had a higher speed rating (still not 149+ though) along with some suspension mods. But, it still had a chip-limited top speed although I don't recall the correct mph. Either way, handling characteristics at sustained speeds above 130 mph were a primary concern for Buick engineers and corporate lawyers.
The following is an excerpt from the GNX hardbound book given to the original buyers of the 547 beasts that describes the suspension mods. Most of them were obviously engineered in to allow for a good launch under boost as well as lateral stability and for improved handling.
"Because of the bigger turbo it was decided that more power and torque when coupled to the stock Grand National suspension and tires would have accomplished little more than wasted motion. The key was harnessing the power, and to accomplish this, race-type re-engineering was needed.
First, a longitudinal torque bar (engineering-speak for a ladder-style traction bar), approximately 30 inches long, was designed and fabricated from mild steel tubing. It mounts on the passenger’s side of the chassis, located at one end of the differential cover (upper and lower mounting points). Its primary function is to prevent rear axle windup and resultant wheel hop and traction loss. A fabricated mild steel cross member ties the chassis rails together and supports the forward end of the ladder bar. The cross member serves as a bonus function as a driveshaft shield preventing the driveshaft from falling and digging into the ground in the event of a U-joint failure. The center of the cross member is tunneled out allowing the driveshaft to pass through it.
The differential cover to which the ladder bar bolts (cast-in mounting points) is not a production Grand National piece. A custom cover made from heat treated aluminum alloy (60,000 psi yield strength), replaces the factory part. This was mandatory for the traction bar mounting, secured with special high-strength bolts.
To insure lateral control and stability (absorbs axle side loads, locates axle during cornering), a tubular steel Panhard rod was handcrafted to run from the left axle tube to the chassis on the
driver’s side. Stock upper control arms were discarded and a steel member was mounted from the Panhard rod support bracket to the right side lower control arm fixture. This member also serves to tie the chassis together, splitting the torque load placed on the chassis on full throttle acceleration when the ladder bar pushes rearward. Without these beefing modifications, excessive chassis flex would occur as torque would be too much to absorb for just one frame rail.
One other alteration was the addition of a G-body rear seat back brace to add body rigidity in the area of the rear kick up section of the chassis. With the revised rear suspension geometry and ladder bar, the GNX exhibits unusual dynamics under acceleration. Conventional rear end squat, caused by front-to-rear weight transfer, is not the norm with the GNX. Actually the reverse is true. When torque-loading (power braking) the GNX to 5 psi turbo boost (the best way to maximize performance under controlled conditions) torque causes the rear of the body to rise 4 to 5 inches off the tires, as though there was rear-to-front weight transfer. It is the ladder bar which accomplishes this action."
As is obvious, the GNX (as well as all the TR's) were designed for 1/4 mile performance and not autobahn prowling, although with the appropriate mods one might venture for that. Regardless, drag racing is a purpose that they have performed incredibly well for 15+ years now.
Originally posted by whitehot84
The reason the factory put the speed control in was because of the tires available at the time. They didn't want to assume any responsibility past that.
Actually, there were tires available then with as high as a Z rating (149 mph+). These tires were used on the Corvette, the Camaro IROC's, and the Trans Am GTA's. Buick chose to speed limit the car primarily because of handling characteristics at speed without further mods, concern for long term engine life if ran at sustained high rpm under boost, and because of potential liability issues. The GNX got the Gatorback tires which had a higher speed rating (still not 149+ though) along with some suspension mods. But, it still had a chip-limited top speed although I don't recall the correct mph. Either way, handling characteristics at sustained speeds above 130 mph were a primary concern for Buick engineers and corporate lawyers.
The following is an excerpt from the GNX hardbound book given to the original buyers of the 547 beasts that describes the suspension mods. Most of them were obviously engineered in to allow for a good launch under boost as well as lateral stability and for improved handling.
"Because of the bigger turbo it was decided that more power and torque when coupled to the stock Grand National suspension and tires would have accomplished little more than wasted motion. The key was harnessing the power, and to accomplish this, race-type re-engineering was needed.
First, a longitudinal torque bar (engineering-speak for a ladder-style traction bar), approximately 30 inches long, was designed and fabricated from mild steel tubing. It mounts on the passenger’s side of the chassis, located at one end of the differential cover (upper and lower mounting points). Its primary function is to prevent rear axle windup and resultant wheel hop and traction loss. A fabricated mild steel cross member ties the chassis rails together and supports the forward end of the ladder bar. The cross member serves as a bonus function as a driveshaft shield preventing the driveshaft from falling and digging into the ground in the event of a U-joint failure. The center of the cross member is tunneled out allowing the driveshaft to pass through it.
The differential cover to which the ladder bar bolts (cast-in mounting points) is not a production Grand National piece. A custom cover made from heat treated aluminum alloy (60,000 psi yield strength), replaces the factory part. This was mandatory for the traction bar mounting, secured with special high-strength bolts.
To insure lateral control and stability (absorbs axle side loads, locates axle during cornering), a tubular steel Panhard rod was handcrafted to run from the left axle tube to the chassis on the
driver’s side. Stock upper control arms were discarded and a steel member was mounted from the Panhard rod support bracket to the right side lower control arm fixture. This member also serves to tie the chassis together, splitting the torque load placed on the chassis on full throttle acceleration when the ladder bar pushes rearward. Without these beefing modifications, excessive chassis flex would occur as torque would be too much to absorb for just one frame rail.
One other alteration was the addition of a G-body rear seat back brace to add body rigidity in the area of the rear kick up section of the chassis. With the revised rear suspension geometry and ladder bar, the GNX exhibits unusual dynamics under acceleration. Conventional rear end squat, caused by front-to-rear weight transfer, is not the norm with the GNX. Actually the reverse is true. When torque-loading (power braking) the GNX to 5 psi turbo boost (the best way to maximize performance under controlled conditions) torque causes the rear of the body to rise 4 to 5 inches off the tires, as though there was rear-to-front weight transfer. It is the ladder bar which accomplishes this action."
As is obvious, the GNX (as well as all the TR's) were designed for 1/4 mile performance and not autobahn prowling, although with the appropriate mods one might venture for that. Regardless, drag racing is a purpose that they have performed incredibly well for 15+ years now.
