pat12spe

Ok, this isn't your average stupid tbi - tpi questions. I've researched and researched this to no avail and thought I'd try to be a little more general in my questions. Who here has done the swap from tbi to tpi? If you have, which way did you go....MAF or speed density? My problem lies with the VSS. I have a 91 TBI and I bought a wiring harness for an 88 camaro (I wanted to go MAF). The MAF camaro's didn't have a VSS hookup until 89 (their speedos are cable driven). But then, people have told me I could only go speed density because of the VSS pulse signal. All TBI's and 86-89 Firebird TPI's VSS signal runs 2000 pulses per minute. Apparently, the speed density runs 4000 pulses per minute. My question is when you did the swap, what did you switch to MAF or speed density? And did you have any speedo or torque converter lockup problems? If so, what solutions did you use? Thanks for the help in advance.

60504

I went from TBI to TPI and kept the speed density setup on my '92. You need to bypass the VSS buffer, which is under the dash on the passenger side, just left of the PCM. I have the 92 Camaro GM service manual with all of the wiring diagrams and found the correct pins/wires to use.

Speed Density is your best bet as you won't need any additional sensors...I am still using the TBI MAP for my setup. I don't know what to tell you about the 88 harness and your 91 car...

pat12spe

So you don't need to buy a dakota box if you bypass your buffer? I've talked to people at S&P and he said the only way to go is with a dakota box, but then again, he probably just wanted to sell me a harness. I'm not going to use the 88 harness unless there is some way I could have a MAF setup but I doubt it. I'm on the lookout right now for a speed density harness, but haven't had any luck. Right now, I'd be willing to buy a new GM harness provided it was just plug and play. Which aftermarket harness would you say is the easiest to use?

60504

Yes - the speedometer will work just like it should by simply bypassing the VSS Buffer. There are 2 wires that must be spliced so they eliminate the buffer.

I am using a GM 92 TPI harness that I got from a friend a few years back, but I wouldn't know where to get one now...Perhaps Hawks or House of Camaro would have one. I wouldn't recommend an aftermarket harness for a setup that was originally available from GM - stick with factory parts as much as possible during the swap to ensure less problems along the way.