Hello out there! I've got a 1985 Pontiac Trans Am (named KITT) who's running a TPI 406 w/ a 6 Speed Tranny. Here's where the fun comes in. I'm coming home in June from a deployment, and I just ordered the Holley Stealth Ram setup. I'm putting in a 284/284 Cam w/ 0.480" of lift. I've been corresponding with Craig Moates, and I'm purchasing a complete tuning package from him. I've been browsing around and I think I may have run into a few snags:

1) I put in the 6 Speed tranny. Every time I let up off the gas the MIL comes on for a code 24 (VSS). Obviously in 1985 Electronic Speedos were unheard of, and as a result KITT does not have a working speedo. Will this pose any challenges as far as tuning would go? The VSS isn't hooked up to the computer, and I'm not sure how to go about doing so.

As far as I know the computer is the one that came in the car, the EPROM just lifts off the board. I've got a custom Hypertech Chip in it, with a part number of 7777. I tried to run the number through Hypertech only to have them tell me that they don't program chips like that anymore *yay!*. (By the way, the Hot Chip's box has a big red warning sticker on it that says "FOR OFF ROAD USE OR COMPETITION USE ONLY")

I'm an electronics technician in the Navy, and I know my way around Binary and Hexadecimal, it's just applying them to KITT that's gonna be fun (without blowing something up, which would be bad.)

2) I've got a single wire O2 sensor, and an AFR gauge, but it reads rich all the time. Me and the guys at the speed shop I work at think that Hypertech made an intentionally richer than usual mixture to compensate for the bigger cubes and the MAF sensor. Should I ditch the single wire O2 for another kind?

Other than that the car goes to the track and runs 12's all night long. I'm just looking for more oomph out of him, and I figured I put of EPROM tuning long enough. Any help that you vets could offer to help get me started would be wonderful. And if any of youse guys wanna take a holiday to Hawaii you've got room at my pad!!

Thanks again!

 

If its a Hypertech anything, throw it away.

If its an AFR gauge that reads from factory 02, throw it away
(useless unless a wideband)

The lack of VSS problem will need to be solved for proper ecm function.

The rest is using the button and going from there.

I highly recommend reading the "Tuning Guide Book " up top in the stickies.

later
Jeremy

 

Yep, I would do a search for "Dakota Digital" products too, they have something that can correct your speedo and VSS issue.

 

Thanks for your insight. The Hypertech chip is going in the trash (as soon as I figure this whole PROM thing out, otherwise KITT won't run). I e-mailed Dakota Digital to see if they had any neat and bright ideas about my VSS problem. If the VSS is not connected, what kinds of problems does that cause the computer? I'm trying to get a clear idea of how the VSS impacts the computer's settings and curves.

My O2 sensor is a stock single wire, yay, but the gauge is a quality Autometer one. You mentioned something about wide band? Those are the 3 wire variety correct? I read somewhere that they aren't that hard to wire in in place of a single wire O2. If this is true than I'm all for it. Any further insight anyone has about O2 sensors would be very valuable at this point. I've got 34 more days here... then I'm home and I get to spend some quality time wrenching on KITT. Thanks again!!

Paul

 

Nope, the 3 wires are the same as your 1 wire, except they have an electrical heater to get them up to operating temp quickly and keep them there even after long periods of idling. They are relatively easy to install in place of the 1 wire, and are usually recommended for use with headers.

Widebands are 5 or 7 wire. Widebands require a sophisticated control unit to keep them working and to interpret the signal. Innovate Motorsports sells a cheap one ($350) that I've used many a time. They're good enough for the average tuner, and can make tuning 10X easier. I recommend to everyone to put that money in their engine build budget, unless it's a stockish rebuild. EFI doesn't tune or calibrate itself, even in the magical "closed loop" hehe. You can put a wideband in place of a stock O2 if you do a little wiring of the control unit's output (scaled to a 0-1v, with a step function at 14.7:1). I've run my car that way for weeks at a time with no problems (I'm in China now though - no car ).

Prom burning is a steep, daunting, and difficult hill, but that's what makes it so rewarding. It's getting easier by the day for people to get into, though. It's about understanding control strategies, understanding EFI hardware, and general engine math. You don't have to be an EE, ME, or PhD to do it. Learn the acronyms early, though.

VSS is used in a few control strategies, such as idle control, fan control, and torque converter lockup (not applicable for you). It'll likely have an easier time idling with it, and that CEL will go away.

 

Jaguarsthatrun.com sells a VSS add on kit specifically for what you need. It plugs in between the transmission and your mechanical speedometer output. I'm using it on a Muncie 4 speed. The kit was around $70 with shipping. You will not be able to get the idle air control motor's throttle follower routine to work right without a VSS.

 

I haven't completed my project yet to make certain this is going to work, but my understanding of everything involved indicates it should.

Different vehicle, but I'm now running a drivetrain that uses the 40 "tooth" reluctor...what your 6 speed has as well? (if not, ignore me ) I'm also adding an electronic speedometer. MAF TPI.

The DRAC unit that was used for a few years on different applications (very common) takes the 40 pulse VSS signal from the transmission and converts that to a few different outputs. 2000PPM, 4000PPM, and 128000PPM, plus 40 pulse direct. (DRAC explanation/pinout) In my case, the 2000PPM output will "feed" the ECM what it needs, and another 2000PPM will feed the speedometer.

 

[B]

I bought one for $349.00, and after it arrived, I realized I needed the RPM converter, which will allow you to log to RPM, instead of logging to "time" only. This converter is another $100.00. Just a FYI so I can save someone some time as they can order it in the kit instead of ordering it seperately.

 

I know this is off topic, but I built my own RPM converter as well as MPH, CTS, MAP, and TPS. Cost me around $15 or less IIRC. I have posted this before and others have adapted it to their ECM's with success. Check it out here . It is the LM-1 Interface.zip file. HTH