Anyone have any Idea what the top speed is on an 89 GTA TPI 5.7? I had the car to about 105 MPH,(The speedo says up to 140) and seem to be no strain on the motor. The tach was reading a little over 3000 RPM's. The car redlines at 5500. The strange thing is I had an 88 GTA with the same motor, and it redlined at 6500. Why are the Tachometers different on the 88-89's? I like the tach on my 88 better. Can the tachs be easily changed? Sorry for all the questions but I don't know who else to ask. You guys seem to know your S**T! I get some good help from you guys. I rarely answer any posts, because I really don't know too much tech stuff on these cars.
Later guys (Thanks)
Mike

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Smokin 1989 GTA- Bone stock except for exhaust. (no catalytic-stainless pipe into Flowmaster 2 chamber).

 

You could have 200 mph on a speedo but that doesn't mean teh car will go that fast. I had an 87 GTA and it went 145. My TTA would only go to 132 because it had a governor. That is most likely the problem, remove/change the chip to a higher top end setting. Most GN's change to 200 mph.

Pete

 

My 305 TPI used to go a needle-width below the 140 mark on the speedo. Since I've added a larger front air dam and the longer side air skirts, I probably don't have that much top end any more, but the car sucks down very nicely at 120 or so. With the gasping 305 and the 2.73 Borg gears, it takes a while to get there though. It's a good thing that southern Minnesota and South Dakota are so open and flat...

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

According to Road & Track, an '87 IROC automatic goes 149. Your car could be 3-4 mph faster because it's a Trans-Am and is therefore more aerodynamic. As for the tach, I know that in '86, you could get the 305 TPI with either a hot cam or a relatively mild one and the hot one got a higher redline. Of course this is on Camaros and Since I have no experience with T/A's or Firebrids it might be different, might not.

Incidentally the IROC also ran:
0-60 in 6.8
1/4 mile in 15.3@90.5 mph

 

Almost forgot; No third-gen (to my knowledge ever came with an electronic speed governor. Some of the auto tranny's, however, did have a "feature" that kept the thing from shifting into overdrive unless the throtle was at 1/3 or less. You could go all the way past redline and it wouldn't matter.
However, GM made a modified upshift valve for the B4C police package that defeats this ($15, I think) Worth looking into.
And if any one tries it, let me know how it worked.

 

Well, comming back from Texas Motorplex Our Fearless leaders got tangled up in a little race w/ 2 turbo.nitrous/who knows what else supras....and took off, I know I was running 4th gear, at 5500 RPM to catch up which according to the speed calculator is 154 or so MPG (I have 3.73 gears...) That was pretty fast hehe

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Corry Lazarowitz
clazarow@voicenet.com
clazarowitz@hotmail.com
1987 Pontiac Trans AM (GTA?) 350 or is it a 305?! TPI
SLP 1 3/4" headers, 3" cat back (stock cat
MSD ignition.
MSD Blaster SS coil.
3.73 Rear end gears
Accell 8.8 Wires
Bosh +4 Spark Plugs (Don't know if they really help but hell!)
Holley AFPR
Race Built Automatic trans ('vette servo, shift kit, tightly packed clutches)--just needs titanium gears now!
Newly gutted cat (the car gutted it's own cat!)
Hypertech Chip (Just found out I had it! :eek
More soon when funds are avail...

 

Actually, the ECM PROM program has a fuel cutoff based on vehicle speed. The VSS input triggers a cutoff at about 118 MPH on cars that were factory delivered with the 15" wheels and tires that were not 'Z' speed rated. The cars that were delivered with the 16x8 wheels abd Goodyear GatorBacks had the programming set at 254 MPH (the highest numerical value that can be programmed in that parameter). Effectively, there is no speed limiter fuel cut off on the 16" wheeled cars. If you reach the 254 MPH barrier, you have more things to be concerned with than fuel cut off.

I've got no experience with the Bucik V-6 ECM programming, so I don't know if there is a cut off point and where it may be programmed.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

Vader does that also apply to the tbi cars. mine doesn't have that cut off and it came with 16" S rated tires dut my buddies 91 firebird with 15" s rated tires had a cut off.

 

Yes, it does apply to the TBI cars. My 91' Bird will stop at 115.

 

Not that Vader needs any backing, but I can attest through the various eproms I have looked at that virtually ALL EFI thirdgens DO have a Fuel Cut-Off at a specific MPH. The only exception is the cars with 16" Z-rated tires installed stock as Jeff said, which is limited to the highest value possible on an 8-bit byte (255 or Hex FFs).

If you get into the Assembly Language or "bit twiddling" of the eprom, even this limitation can be removed by nullifying the comparison of the Vehicle Speed so it is never tested...then you can even exceed 255 MPH...if the rest of the car is capable of exceeding that speed.

 

Yes! I had always thought that I would need to change my chip, but since my tires came 16x8 it looks like I'm in luck. Ah vader you made my day.

 

My 88 TBI 305 doesn't have a speed governer. I had it at 4,000 rpm in fifth gear (T-5) which is a .63 ratio and with 3.42's just a few days ago. I calculated that out to be at 145mph. The car kept going faster but i didn't want to push it. I was pretty amazed.

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Pat Hirsz
www.iit.edu/~hirspat/MyPage2.htm
88 305TBI
Mods:Hooker Aerochamber 3" exhaust, no cat,SLP 1 5/8" headers and y-pipe March pullies, no smog, 180 thermo,
14x4 K&N, 3.42 gears(open), Ultimate TBI Mods,AFPR,MSD(ignition,coil&wires),Edelbrock TBI Manifold, 190ltr/hr fuel pump,
Eibach springs with KYB's all around,
Harwood cowl hood, Z-28 wing, fresh paint(black)
120,000 miles, 5spd, T-tops
0-60mph-7.2s-Gteched

92 RS, 305TBI, auto, 3.08 gears, 180 thermo, glasspack (no muffler)

 

Does anyone know if the carbed cars had the fuel cutoff? Seems impossible to me.