About 3 years ago I converted my '82 CrossFire 'Vette to TPI. I purchased a 355 short block, installed new cam with 222/222 deg duration .447 lift plus 1.6 rockers, Chev. 993 heads with 2.02/1.60 valves. As part of the conversion I installed a VSS at the transmission where the speedo cable connects, this has always been a weak point as the cable is in a bind because of limited clearance, and the speedo and VSS stops working. Is there a better solution for the VSS? Also lately the car has been runnig poorly at part throttle, hesitating and sometimes backfiring through the exhaust. At WOT the car runs strong. I have been to the local drag strip where it runs in the 8.80s to 9.00s in the 1/8 mile. Any help would be greatly appreciated as I love to drive this car.

 

Why did you put a VSS on the tranny? You should have just used the stock mech drive cable without some kind of VSS adapted to it and use the ORIGINAL 82 VSS, it's a little yellow box w/ an optical emitter/receiver plugged into the back of the speedo.



the optical unit:


screws in here:


there's a mirror rotor inside the speedo, that'll reflect the optical emitter's beam and the receiver will pick it up, the yellow box translates the pulses and sends the into to the ECM.

 

[QUOTE=Twin_Turbo]Why did you put a VSS on the tranny? You should have just used the stock mech drive cable without some kind of VSS adapted to it and use the ORIGINAL 82 VSS, it's a little yellow box w/ an optical emitter/receiver plugged into the back of the speedo.

I purchased the ECM and new wiring harness from Jim's Performance. He told me the the original VSS did not put out the proper volage signal for the new ECM. The new VSS was included in the kit I purchas from him.

Using the original VSS would be simpler, but will it plug into the new wiring harness? Do you know if this signal does anything else besides controlling the lock-up converter?

Any and all input and help is greatly appreciated.

 

yeah, the VSS signal is used for reseting the IAC positions during driving and some other things.

I wasn't aware of the signal differences, seems weird though, why would GM change it if so many other things remained the same between TBI and TPI systems...like evolution some was changed some not. Relocating the VSS to the tranny to be used w/ an electrical speedo is imaginable but why change the complete signal and all....weird

 

Twin Turbo,

I was wondering about the possibility of re-locating the new VSS to up behind the speedo to receive its input from the speedo cable rather than on the transmission and relieve the stress on the cable.

Since it lookes as though you have had your speedo out, do you think this is a possibility?

Thanks.

 

or locate it by the cruise control transducer

 

I'm assuming you have mechanical speedometer.

I used one of these:
http://store.summitracing.com/partde...0&autoview=sku

And I spliced it into my speedometer cable using one of these:
http://www.madvet.com/-/shop?frame=1.1168

No binding problems.

 

 

carriljc,

I do have a mechanical speedo, and the VSS pictured from Painless is the rascal that's causing me all the problems. This short piece of cable is just the ticket. Thanks.

 

that must be the difference, 4 pulses per revolution, i think the original one has 2 pulses per rev.

 

TPI uses pulses in 2 flavors. If you have a Mass Air Sensor style you need 2000 pulses/mi. If you have speed-density you need 4000 pulses/mi. Can't remember on an 82, I think it is 4000 ppm. LT1 and TBI are both 4000ppm.

As a side note, you can buy a 90 degree adapter to go on the transmission so the cable isn't slammed into the tunnel. Corvette Central and most of the catalogs carry them. That is what I used on my '69.

 

If we knew the number we could probably look up what VSS pulse you're supposed to be using.
I bought the wrong one the first time (ended up eating the cost because I forgot to return it).

 

Thanks all for the input, keep em comming.

I have gone through 2 of the 90 deg adapters, the gears just don't seem to hold up, and it's a bear getting to without removing the crossmember.

Does anyone think the lack of VSS input at this time is contributing to the problem with part throttle cutting out and backfire problem?

The ECM is 1227727.

 

OH, screw all that adaptor crap, literally, I just drilled a hole in the driver's side/tunnel, where the 700 tranny cable goes, I have a sending unit, and get over with it going under the car to the speedo...I routed it under the carpeting and it's slicker than snot....

now if the speedo output is on the pass side, I dunno, but still, just another hole and up and over the tranny hump from INSIDE the car....

I don't even have a screw on connector for the cable shroud, just did the end/tip into the sending unit, secured the shroud end to the floorboard with paneling adhesive, and sealing the hole also...and had over with it....

only been through one overhaul in 8 years, still going strong....

typical, anything I do, lasts,
'
what some 'cures' for like the 700r4 3/4 clutch pack are useless....

in fact the cores for 700r4 are near worthless here in Jax Florida these days....

am getting a 2004R, and have done with it,.....

GENE

 

for that ECM. I'm using the 1227730 and they're supposed to use the same pulse counter. Should work fine once you get that 16 dollar adapter....unless you've managed to damage it. I'd try it..it's only 16 bucks.

 

TT - www.diy-efi.org/gmecm has all sorts of great info on this kind of thing.

 

I'm glad I fell on this thread...

I have the MAF setup off a Trans Am with a ???? ECM. The ECM doesn't have the number on the outside as it is a rebuilt one from Blue Streak in Canada. Should I be using the stock setup or the $85 VSS add on and get a flex cable? There are two versions - 40-45 tooth driven gear or 34-39 tooth - apparently the 34-39 was the most common but I'd prefer to hear from someone who actually has an 82CFI.

As far as the TV/Kick Down cable, would I just get a universal one...they seem long enough as the CFI seems it will be too short?

 

The '82 Crossfire already has a MAP sensor, so I'm using a speed density system. This does not require a mass air sensor and the additional space it requires.

 

I decided on MAF as the computer will adjust v. me burning PROMs. I've heard the MAF is more forgiving will the Speed Density is more tuneable.

 

The maf is more forgiving to changes,cam swaps.injectors,headers etc....the speed density is easier as far as air cleaner ,you can just hook up a air filter right on to the end of it without having to worry about maf plumbing.
The tv cable you could use one from a 87-89 trans am
The maf computer is a #1227165.