I'm trying to help out a friend and it's going to result in my first chance to custom burn PROM's.

The car is an 85 firebird. it has an 88 TPI 350 harness/computer/PROM/MAF from a z28. The PROM is unaltered. The engine is a 350 with a T56, heads, headers, SLP runners, cam, aftermarket injectors, etc. I don't know much about the specs on the cam right now. All I know is that the car lays down on the top end big time (the motor should pull to at least 5500 but it's pretty flat at 5 and up) and basically isnt living up to it's potential. All I know so far is that the BLM's are around 118 below 3000rpm under light load. No AFPR right now.

Basically, it needs a chip set up for the car. So, we're looking into getting tunercat, a pocket programmer etc. I already have diacom +.

Question 1: diacom-plus identifies the prom ID as 141 - or $8d. I assume this can't be right, as $8d is a SD system? Otherwise diacom will scan the car fine at 160 baud with an 88 5.7 TPI VIN. Anyone know why it might read 141?

Question 2: how do you guys get around the painfully slow 160 baud interface? I'm used to the 8192 on my 91 Z, the 160 baud just seems awful. Do you just have to live with it?

Question 3: diacom has a field called "spark control counts". is this the knock sensor?

Question 4: does this ecm output timing data? There is none on the interface

thanks!!

 

If he swapped to an 88 computer, his baud rate should be 8192 just like your SD computer.

The spark control counts field should be the number of times that it detects a knock.

I'm not sure about the timing data. I haven't had my scan tool on a 165 ECM yet, but I don't think my 85 ever gave me any timing info. You sure you've got the scan tool set up for a 165 ECM and not for the original 85 ECM?

 

With Diacom you have to give a VIN# that matches the ECM, what year are you using? If you are NOT using an 1990-1992 VIN#, then you are NOT using SD. Does it show MAF gm/sec airflow? Also, are you using the special TPI cable for MAF cars?

The Prom ID of 141 is strictly an id number maintained in the eprom which can be changed in the "Constants" by TunerCat. In fact, Diacom does not display the actual Prom Type ($8D or $6E) anywhere - because that information is not in the ALDL data stream (to my knowledge). I use my Prom ID# to match the particular number of the BIN I am working on. The fact that decimal 141 matches hex 8D is coincidental.

 

Yep, I used the VIN off my dad's 88 IROC (350 TPI).
The data seems to make sense, but it is just SLOW updating. at least a second per frame if not a bit more.

The only thing that was odd, is that diacom said that it may be difficult to scan the ECM and that I should use "diagnostic" mode instead of ALDL mode. So I used diagnostic mode and never tried ALDL mode. Maybe I need to use ALDL mode?

thanks for your help!

 

Yes - the MAF shows gm/sec airflow. i think it was around 6-8 at idle and it got up to 50ish with light around town driving.

I don't have any special TPI cable. I just have the standard ALDL cable. So far I've used my standard ALDL cable on my 91 350 TPI, and a 95 B-body with no problems. Do '165 need some kind of special cable?

Thanks!

 

You may not be able to fix this with a new PROM. Fact is - the TPI curve is flat at those RPMs. Siamesing helps ... but it doesn't TOTALLY get rid of it.

Tim

 

I suspect this is because you are using the "Standard" cable. For 1985-1989 MAF TPI Cars, you must use the special cable to get "full" speed. I have heard from some MAF TPI users that they could operate with the "Standard" cable, but only in Diagnostic Mode or Slow ALDL mode. To get full ALDL (and speed) you need that special TPI cable.

Diagnostic mode causes certain settings to be "overridden" so the scan tool is not giving you a true reading.

 

thanks. i'm guessing i'll need to bleed some more $$$ to diacom for that special cable. I'll do a search on here to see if anyone has made their own or has mods to make it work.

with regards to the TPI RPM limits, is that true even with the SLP runners? or is it the base that is restricting it.

thanks again

 

well, i took the first step today and ordered one of the ZIF-ECM adapter thingies.

I have a question though. As I mentioned in the first post on this thread, I am going to be working on a friends' fairly heavily modified firebird.

My concern is that even if I do get the BLM's in the 126-130 range, is there going to be any noticable increase in performance? I still don't really undersatnd how the BLM's and WOT affect each other, or if WOT is a fixed fuel ratio, or uses O2, or what. But I can say that his car feels better at part throttle (crisper, torquier?) than at full throttle. does this have something to do with it? All I know right now is that everything I scanned indicates the BLM's are around 118, so I think i need to make a fuel injector constant change.

thanks.....