I'm just getting started with the DIY tuining. I have a C3 1228746 ecm. I don't see it mentioned much on this board, I gather because it has significantly limited capability (slower baud, fewer parameters available for tuning . . . ) as compared to other ecm's (7730, 7747, 8625). I am planning on buying a Prominator for the 8746, but after reading many posts on the DIY board, looks like I should first upgrade to a better ecm. Should I deep six the 8746 and convert to something better, or can I get the job done with it (and some aspirin)? I did see Ken73 just announce they're coming out with the SpeedReader, which should give the C3's new life. Advice appreciated

Good question. Right now there are a lot of options for TBI and then again, not so many.
The 7749 or an upgraded 7730 can run 2 TBI injectors in P&H mode, this was done and do a search for it. This will net you a faster aldl baud rate but it'll limit you to using code that was initially designed for port injection. Wet flow TBI has a lot of things it has to worry about other than just more AE. This is and the fact that the firing strategy of the 7749 is batch and even when made to do "TBI mode" it doesn't alternate injector firings, it fires both at the same time as TPI would in a double fire mode. This SHOULDN'T pose a problem with idle stability but it really depends on your intake.
Next is the "newer" TBI ecms found on the trucks up until 95. These ecms are actually pcms but you don't have to have an e-trans to get these pcms to work. There are again some guys that have converted to them and so you should do a search. TunerCat seems to be the only guy offering support for them so expect to pay $90 in just software. These are p4 ecms made to run TBI and their code is definatly superior to that of the c3's.
Now the speedreader... yes, the ultimate OEM computer mod. When it comes out it'll basically put the c3's ahead of the p4's in everything but processor speed (even that can be overclocked). I think with access to all 256kb of ram at sampling frequency's that double the p4's it's something to be considered for TBI users. This wouldn't require any repinning of the ecm harness and no memcals to worry about. You'd have the ultimate TBI control hardware since you'd be able to run any code you wanted and have direct access to disabling the code you didn't need or want. RBob has his copyrighted "Ultimate TBI" code that would be sold to just about everybody that buys the speedreader. His code is excellent, it has fan controls, better everything, and even nitrous controls! The man is a genious with code. I bet he's fluent in 01100010 01101001 01101110 01100001 01110010 01111001. Yes that spells a real word.
So if you can hold off until the speedreader is officially released then stick with the 8746 and it's code. I've been had great success with it but I was pretty alone in my travelings. Luckily the code was similar to the 7747's and so a lot of my questions were already answered in archives.
Really the limitation of TBI lies in the fueling code. For some odd reason there are things in the code that just make for tuning nightmares, like the async AE, terrible AE vs delta TPS, and annoying adders and biases all over the place. This is my opinion, not fact. For a completely stock and ultra low output motor the code works fine. Anything that has the potential of pushing a thirdgen down the 1/4 in less than low 14's is going to be frustrated with the stock code. There are patchs to help get rid of some of the annoyencies with the stock code. The code 43 is one really nice patch that disables the WOT knock test that's done on the first couple WOT runs of a freshly started engine.
So I think your best bet now is to go with the p4 TBI pcms. Right now I don't know when the speedreader is going to come out, if I did I might just tell you to stick with the 8746.

There is complete TunerPro (.ecu, .ads) support for the '94/'95 TBI truck PCM's (16196395, 16197427) running the $0D mask and it is expanding fast. I am working on other .ecu's as well. A lot of the problems with the C3 TBI ECM's have been corrected in the P4's such as a 50% delta TPS AE table, RPM corrections for delta MAP AE, no forced knock test etc. Just throwing this option out there. HTH

Good, glad there's an ecu file out for them. As far as the TPS AE in the c3's, going over 50% doesn't mean anything, it's the fact that in the 8746 only superman can reach anything above "6.2%" yeilding a table about as worthless as an on/off switch. So in the 8746 I don't even bother with the anything but the first 2 cells, then I focus on the MAP AE which seems to work out great. There is also code in the $61 mask (8746) that does more than just a table lookup. Like if the TPS delta is high enough it'll double the MAP AE. I think this is to get around the fact that the TPS AE code is so digital. This gives the AE a 3rd dimension if you would. Which is hard to tune for lack of comprehension. I don't have any good plan for how to tune it yet other than trial and error.

Im holding out for the speedreader. . . though I've had pretty good luck getting my new combo tuned with my 8746 $61, PROMinator, and a WBO2.

Q. Do we yet have a valid ECU or XDF (tuner pro 4.0) file for the 8746. There were problems with the VE table.
http://www.thirdgen.org/techbb2/show...hreadid=248062

I'm working on it now.

Thanks for all the replies. Trying to digest it all. You guys have laid out a few options that I have a few questions about.

1. Switch to a P4 ecm
- Q. what mods are required to the wiring to swap the ecm to a P4?
- Q. what mask would I run with the new ecm?
- Q. If I try to find a junkyard P4, what vehicle and ecm number(s) would be the best choice?

2. Switch to a 94/95 truck pcm
Q- same wiring and mask question as above

3. Keep the 8746 ecm
I like the idea of keeping the 8746, at least for now until I get more educated with the tuning. JPrevost, looks like you've been able to make it work for you, and my mods are far less than yours, so far.
- Q. If I buy a prominator now and speedreader comes out later, will the two be compatible, or will I have to start over and buy another prominator?

What will be harder, starting from scratch with a new ecm and mask , or work around the shortcomings of the 8746?

Sorry for all the questions. I really appreciate the vets sharing what you know with the new guys.

Hey man I am thinking of doing an ecm swap also. Instead I am thinking of just trying to use the one that we have and work with it.

Let me know if you have any luck. I am still trying to get all the stuff for it. Fun huh?

Bill

Finished doing the xdf file for the $61 mask. It will be released when TunerPro 4.0 gets officially released.
It's a LOT better than before , you all will like it or your money back .

xdf is the file format replacing ecu right Jon? That's awesome then, looking forward to its release.

Yeah, it's a lot nicer than ecu.

So when TunerPro 4.0 comes out, ecu files (i.e. 8746jonprevost61h.ecu) will be replaced by xdf's. What will be the advantages. Any idea when 4.0 is available?

Yeah, we've been beta testing for a couple of weeks . . .visit the site and search this forum for more info about new features and enhancements.

Here's something from a while back . . .
http://www.thirdgen.org/techbb2/show...hreadid=248174

If you are interested in the TBI P4's, I have created a very comprehensive .xdf for the $E6. I'll release it when Mark releases TunerPro V4.0.
I datalog with Datamaster, its fantastic IMO.
Ben.

I'm loving the xdf file format. I used to use TunerCat because of their advanced tdf compared to ecu. Then I ran into the problem where the tdf file couldn't have more than 99 items, yes, I had a LOT of stuff I wanted to include but it gave me an error. So I was using like 3 tdf files and 2 ecu files depending on what bin I was working on (some patched needed special definition files).

Hi guys! I know I popped in this post out of the blue, but I have a question and am sure you are the guys to ask! I have been looking for TunerproRT's datalog definition file for my 91 RS 8746 TBI for a very very long time now and have come up with nothing! And am very confused as to how to make my own definition file. I want to be able to use TunerproRT to datalog sooo bad that I would rather pay one of you guys to make a functional file for me! Please, dont think that I am lazy and just dont want to learn how to make one myself, it's just that my area of focus right now is on other projects and I dont have the time. So if someone could make me that file and wants to earn some side cash or something, PLEASE let me know and we can work a deal!
Thanks ahead of time!

Sent you an email.

Thanks you so much for your help adambros! Its members like you who make Thirdgen.org such a great place.

What's the benefit of using TunerPro to datalog as opposed to WinALDL, which is what I've been using?

WinALDL is a datalogging software. It will record all of the sensor data. But TunerPro you will use to actually edit the file that is located on the chip.

For instance if you data log and your BLM data is below 128 in any given cell, then you would use Tuner Pro to go to that cell and remove fuel becasue you are running rich. Then burn the new file onto a chip, put it in the car and do more datalogging and repeat the process.

I'm just getting started on this stuff myself. But I have seen it done and will take a whack at it myself.

There really isn't any. They both log the same information.

Now, when TunerPro v4.0 is released it looks like there will be several new logging features, such as a real-time dash display (much like what WinALDL has) in addition to user-selectable parameters to monitor & graph over time.

http://tunerpro.markmansur.com/beta/tpbeta.htm

Still in Beta, but you're welcome to have some fun with it. I'm getting closer and closer to releasing it every day.

I think there are still some issues with 160 baud dataloggong. I finally bought a 7747 and some pigtails so I can try it on the test bench. Once I get that up and running I will be able to flush out the remaining 160 baud issues. At that point, you should be able to datalog all of the 160 baud ECMs without issue. Just a matter of time.

You can import your ECU files to XDF files with TunerPro 4.0, btw.

Have fun, and me sure to notify me of bugs you run into. Keep in mind that the more information you provide (specific repro steps, files, etC), the better.

I'm considerably less interested in feature requests at this point. I've already had to cut a ton of things just so I can get this thing out the door in a reasonable amount of time. Still lots on the list for the 4.X series, though. Should loads of fun!

Mark