Hey folks,
I just bought a 1992 Camaro RS ( 305 L03) T.B.I and one of my first modifications was that I just changed my rear end gears to a 373. I don't have any problems with drive, but when I go into overdive and the transmission has made it through all 3 shift points and I'm cruising along, as soon as I get to 3,000 rpms, my car stalls for a quick moment. I can't get past 3,000 rpms.. Is it a rev limiter or a speed sensor causing this? and is there any way that I can bypass either of them. I already bought that Hypertech chip and it didn't help increase the speed limiter or rev limiter. Any suggestions would be greatly appreciated.
Sincerely
Keith Martini

 

Welcome to this site, its allways nice to meet new members, to answer your question, its best for you to go to this and read how to do it your self, hope I have been some help, and I am sure that Ill talk to you in the future.




1WickedSS


https://www.thirdgen.org/newdesign/tech/unlimited.shtml

 

You are hitting the speed limiter. It is comming on a lot quicker because you are using your old speedo gears and your car is getting a VSS signal for a much faster speed than you are traveling. Speedo gears will put your limiter back to 112. You can also bypass the limiter as linked above or just change it in the prom with a new burn.

 

Welcome Aboard!

Assuming that your L03 has the factory fuel cutoff settings, and assuming that you had 2.73 rear gears, changing to 3.73 gears would lower the fuel cutoff MPH from the target 118 MPH to 86 MPH.

The factory ECM programming limited MPH to about 118, due mainly to the tires installed on the vehicle from the factory. Cars equipped with "Z" speed rated tires (like the IROC-X and TransAm) had the fuel cutoff MPH parameter set at 254 - the maximum allowable number in that parameter. Since 254MPH is not likely with most of these cars, many consider that there is no speed limiting, when in fact there technically is a limit.

Just doing the rough math, you can follow the logic:

Tire diameter - 26"
Tire circumference - 2.166666'
Tire RPM at 60 MPH (and revolutions per mile)- 775.6973

With 2.73 gears
Driveshaft RPM @ 60 MPH - 2118
Engine RPM In OD @ 60 MPH (0.70:1) - 1482
Engine RPM in OD at 118 MPH - 2905

With 3.73 gears
Driveshaft RPM @ 60 MPH - 2893
Engine RPM In OD @ 60 MPH (0.70:1) - 2025
Engine RPM in OD at 86 MPH - 2905

Considering the notorious innaccuracy of the factoy tachs, and their tendency to read a bit high, your "3,000 RPM" cutoff is clearly expected.

If you correct your VSS gearing so that the speedometer reads correctly, you should once again be able to achieve a higher RPM in OD, but only to 118MPH.

I'm presuming that the HyperScrap PROM is still speed limited, since they would not want to be subjected to any liability for tire failures and circumventing any factory safety programming. You may end up burning your own custom PROM to solve that situation and improve several others. A lot of valuable information about that is available here.

 

Once again, my research, endless drivel, and slow connection is blown away by a few terse sentences. Shifty has your problem covered, and with a lot less waste of bandwidth.

 

If it makes you feel better vader, your "drivel" makes for pretty good reading. And as for keithmartini, please learn from my mistake, if you start burning proms, keep your original for a spare and buy a few extras to play with. That way you'll have something to fall back on if your chip or programmer mess up. Ask me how I learned that

 

I just wanted to say thanks... 20 minutes @ radio shack and another 30 minutes installing an On / Off switch to the V.S.S and I was good to go. I appreciate the help.. Now my car screams past 3,000 rpms..
Thanks so much..
Keith Martini

 

dang speed limiters were set at 118? thats weird.... in my car stock ignition and drive train 155 hehe but it was an lb9 iroc so that might have made a diff.... i dont know

 

Varies through the years. Initially some of the tbi cars didnt have it set (maxed out to 255) but the later years had it set.

 

I believe the Irocs wern't limited to 118 because they came with Z rated tires unlike other models.. which never really made any sense to me.. they were all technically suppose to be sports cars.. now you know whats lame? My LS1 TA's speed governer kicks in at 160 which it can do just fine in 5th gear and then ur stuck with that whole extra gear

 

Maybe that's why my '94SS tops out at 163 MPH?

 

you get an extra 3 mph? thats no fair! or maybe its cause factory speedo's are normally calibrated a few mph over? I dunno, mine only goes up to 155 and then has a little line after it and it goes a little past there then the fuel cuts out..

 

94 SS? Did they make that one especialy for you?

 

Impala.

 

91 ANTT TBI cars have the speed limiter set to 114 from the factory.

 

I knew that I have a one track f-body mind.