well i was wondering if it would be possible to override the speed limiter on my friends 91z?

tia,
Taner

 

Yes, through a re-burn of the chip.

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Mike

'90 IROC-Z, 5-speed, ZZ4, G1 Trick Flows
Moderator SEThirdgen

 

I wasn't aware of any thirdgens having a speed limiter.

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The ones that came from the factory without Z rated rubber were speed-limited.

 

I'm not aware of ANY thirdgens coming with Z rated rubber. At least the early ones got V-rated 16" tires and S-rated 15", and did not have a speed limiter. I'm well aware of the LT1 cars having speed limiters with non z-rated tires, but this is the first I've heard of thirdgens. I've even looked at PROM code, and none of the stock BINS have had an rpm dependant fuel cut off selected. I haven't spent much time looking at the speed density cars, but I still don't believe they had that limiter.

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I know that SOME must have come with a limiter since my old 90 305 TBI Camaro (15" wheels, H-rated tires) would shut down the party at ~118, ditto my 1991 V6 powered RS with the same tires. Not sure of TPI cars, but it would stand to reason that if they did it for the low pered models they'd surely do it for the higher powered ones.

The cheap way to do it, without reburning a chip, is to simply rig in a toggle switch in one of the 2 wires going to the VSS (near the tailshaft of the trans). Doesn't matter which wire. When you flip the switch the ECM will lose it's MPH reference signal. The speedo will go to 0, but you'll keep right on truckin'.

 

there was a link on thirdgen.org i printed out the instructions, it sounds like exactly what you said however right off of the computer. i will do that next week

thanks!

 

The 91 TBI Firebirds have a limiter, I turned it off in the chip for my friends car when he went from 2.73 gears to 3.42's. His top speed after the swap was like 80-something mph since the speedo was way off.
It is funny driving his car cuz it seems to accelerate sooooo fast, if you are judging by the speedo.

I don't know if the TPI cars have limiters, all the bins I use already have the limiter set to 255mph.


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1986 Trans Am WS6
LT4 350, LT4 Hot Cam, T56, 52mm TB, MSD 6A & Blaster 3 Coil,
LT1 3.42 Posi/Disc Rear, Lakewood LCA's & Adjustable Panhard Bar,
Eibach Lowering Springs, 17x9 WS6 Wheels, T-Tops,
Custom 4" CAI w/ K&N Filter, 160*stat.
Autometer TriplePod with Phantom A/F & Boost Gauges.
High Speed Run: 157mph
Best 1/4 mile run: 14.94@91.67mph This was with the LG4 carb setup.
WS6 Trans Am.

 

Keep looking at stock bins. Most of the 305 automatics have a speed limiter at around 115 MPH. The "better" tpi cars have a speed limiter at 255 MPH, making it useless. The rev limiter is set to about 10,000 RPMs, again making it useless.


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1991 Camaro Z28
350 L98 w/ T56 (originally 305 LB9 w/ T5)
318 RWHP, 419 RWTQ
12.803 @ 108.50 MPH (1.932 60')
Member: SoCal F-Bodies
ThirdGen 4-Life!

 

I guess i never looked at any 305 auto BINS because they were of no use to me. All of the 5 speed and L98 BINs I've seen had the 255 limit. Oh well. Jimbo backs down and admits defeat.

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Lounge lizard,

is that the only way for this car?????????
or can i put a switch on the vss wire off of the ecm?

 

I've not heard of that mod, but it doesn't mean it won't work. I know the VSS is essential for various things but can't remember if it would have a negative effect if you lose the signal when driving at WOT. I'll pass word to GMTech to poke his nose in here.

Otherwise, IMO I would just find someone who can change the value mentioned on the chip and be done with it.

[This message has been edited by Lounge Lizard 6 (edited June 22, 2002).]

 

Like mentioned before, all these cars have speed limiters AND rev limiters, but different cars/options have differenent speed settings, and the RPM value is set too high that you will never hit it. I burn lots of Speed density PROMs, I know this for a fact as well. When I burn PROMs, I set the speed limit for the max, which is 255. A stock '92 L98 RPM cuts out at 10,031 RPM

As for the "other" mod to bypass the speed limiter (i.e. disrupt VSS signal to the ECM) that works, but it can also cause drivability problems. I know alot of people who had stalling problems everytime they did it. The ECM uses speed input for a variety of things. Not to mention, if you have speed density TPI (VSS Buffer internal to the ECM) then you will also loose your speedometer and have no clue how fast you are going.

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