I just have a couple of questions for the experts here....i have done a little bit of reserch on this....but just wanna be sure before i lay out the cash and fry my brain for nothing....I have an 85 TA and a 95 GMC Suburban....is the process for burning PROMs for both of these vehicles the same? Can I burn a PROM for the Suburban and invoke highway mode? Also, since the transmission is electronically controlled, can I adjust the shifting RPMs from the ECM or is there another brain just for the tranny? I really like the suburban for its room and comfort, but hate filling it up with gas so often (42 gallon gas tank)...My goal is to somehow get 20 mpg on the highway....Would swapping from the TBI to TPI be worth the effort?

 

Burning process is the same, different chips of course but still the method is the same. I haven't played around with the 95 as much as I would have liked. It also depends on if your truck is a MT or auto. It seems through my normal sources that MT uses a 2732 eprom, same as the TBI f-body's and the common 7747 truck ecm's, while the auto uses a 27C512. Either way, same thing. I'm not sure about the highway mode because I don't exactly have the time or reason to find out BUT there are other ways to go about it. The pcm controls the trans and there are lots of options in Tunercat to change the line pressures and shift points. There is enough to change to keep you busy for a while .
As for going TPI. I would do it if you could find it cheap and complete. On a stock motor wanting to make the most low end torque possible, TPI wins. Definatly keep it below 4500rpm else TPI becomes a BIG problem. Shouldn't be an issue since even in the stock code, the 95 trucks had a fuel cut-off of 4500rpm. If you drive the truck enough then do the TPI swap, it'll probably pay for itself in a year in gas. That too depends on how heavy your foot is .

 

JPrevost pretty much said it all. I have a 94 and burn my own chips. Yes the shift points can be changed in the computer chip. I havent done anythign serious yet but Im going to have to with in a couple weeks when I get my 383 running so just letting you guys know Im going to need alot of help im sure. Also does anyone know of some scanning software I can buy. I have an autoxray right now but would love to have a program like WinALDL but I cant get it too work on mine. But my ecm sends info to pin M b/c I have no pin E so Im guessing maybe its an 8192 baud rate No one seems to know and you guys are my last hope.

Josh

 

yeah it's 8192 baud. I use Diacom, not sure of any other good sources for freesoftware. Might be able to hack diacom and figure out the aldl data stream locations and how they're computed. Then use some of the freeware that uses the max32 interfaces. Lots of the freeware out there have an easy way of manipulating the raw data through some kind of lookup text file. If you can't hack diacom just ask TunerCat if he knows where the aldl data locations are else last resort maybe somebody on the www.diy-efi.org mailing lists would know.

 

Thanks for the help guys....i just got the truck a couple of weeks ago, but i love it so far! I did my first 'mod' yesterday by installing an electric fan in place of the clutch fan....seems to have a bit more power now....If i were to swap to a TPI setup would i have to swap ECM too? or would the stock computer drive the TPI setup? sorry to be asking questions that i am sure have been answered already, but the search engine is down so I ask them anyways... I do already have a TPI that is in the 85 TA that i would be able to use...don't drive the car anymore cause body is in bad shape....so please clue me in....BTW what kind of mileage increase do you think I might get from that swap?

 

badburban , Try http://www.ttspowersystems.com/dm_dload.htm#Trucks it will let you log 20 runs and after that you have to buy it. You can get the cable for him or try www.akmcables.com .

 

JPrevost,

Thanks that helps. Nobody has ever been able to answer my questions even here. Thanks for your help. One other Question how hard would it be to modify the free software. I'll admit Im no computer expert but my dad is. I know a little programming (C, and VB) but just enough to be dangerous.

70RS94Z,

Thanks Ill check it out.

AFootVoyager,

If you really want to help out your 95 get rid of the tbi heads. They are terrible. Then maybe go to a tpi set up at the same time. Hey a good website for us Fullsize guys is www.fullsizechevy.com I frequent there and is a good board but they dont know much about burning chips but we have thirdgen for that.

Josh

 

IMO, your asking for a poor trade off.
When you buy a burb or some such vehicle, mileage shouldn't be a concern. Anything you do to try and invoke a lean cruise will instantly start cutting into engine life. there is no free ride in tuning. That's one item that is a universal truth. While on a light car you can min that shorter life effect, as weight increases, the load goes up quickly and then life expectancy drops.

You might consider getting a BBC version. The larger engine allows you to run at a lower engine load for any road condition.

With nothing done other then careful driving style, my 454 TBI just did 15 MPG on sections of a 1K mile trip thru the hills of WV.

Your also wanting information on your PCM, ecm is engine management module, PCM is powertrain control module.

And yes there is editing available for the tranny, a visit to www.tunercat.com will let you see what all is available.

 

Is this not a ThirdGen f-body site? We've (all of us) put a lot of effort into helping everyone. Unless your vehicle fits the site charter. . .

RBob.

 

RBob I didnt mean to offend anyone. I didnt mean to sound like an a-hole. I was just commenting. If it came across any different then that then I am sorry. I asked my same question a few months ago on here but with no replys. But I never expected anyone on this site to know about my truck. But this seems to be the best site I know of when it comes to prom related to things. So you guys are my only hope on these things. I soon will be working on the chip for my 383 (hopefully within 2 weeks) and will need lots of help im sure and will have to ask for the help of the excellent people who take their own time to help some stupid novice (me) who knows absolutely jack about these things. I think this is the best site on the net for a newbie to come and learn. The likes of Grumpy. Traxion, JPrevost, and many many others who share their invaluable knowledge with newbies like me is what makes this site great. Ive been to many other sites who get mad when a newbie comes on and asks a question. They will make fun of him for asking a question. Well that is just wrong. He is a newbie for a reason and that is b/c he doesnt know everything or else he wouldnt waist his time asking for help. I hope this site does not turn into one of those sites and the mods keep it as one of the best on the net. I plug this site all the time telling about how great you guys are and how much you know becasue it is true. Well Im done and I would like to say sorry again for it I came across as anything different then I meant. Sorry.

Josh

 

It can be difficult to converse over a text only medium. The written phrase is all we have to go by. In this regard it becomes important to choose words carefully.

I understand your frustration with being new at this and not getting answers. The ones that make fun of others are the ones that are in trouble themselves. Just keep plugging away, it actually does become easier.

RBob.

 

That's what I've been doing for the last 3 weeks! So far all of my nagging quesions have been answered...and I have been saved from "circular tuning hell" a couple of times.

:hail:

 

There are times when I just don't have the time, and just don't visit here from time to time. Heck I even take off for a few days from time to time. But, the only people I won't return an email to are those that have been rude. So if you get in a corner, just write.

It will help if you at you leisure read thru the Final Answer posts, I've tried to write a series of postings explaining engine stuff and how that relates to prom stuff. The more homework you do in advance will save you grief in the future.

And believe it or not you can ask a guestion that no one has an answer to. Well, at least a guestion I don't know an answer to. LOL