cardo0

I'm guessing that is the "adaptive strategy" and the long term fuel trim is doing it's job. And this would be more pronounced/noticeable if the ECM was recently powered down. A lot of drag racers notice this as their time slips improve after a recent battery disconnect even though the engine becomes hotter after each run.

Will it fully correct your lean problem? No! I highly doubt that as the data blocks in the fuel map table need to be replaced/upgraded.

Good luck and let us know what works. Please.

Buccaneer

This analogy is not correct when we are talking about an 84 stock ECM. That ECM along with the 82 or for that matter the GM1227747 and GM1228746 which are much newer (late 80s early 90s) and do not have short term or long term trim tables. What you have is a VE low table and VE high table which is not a trim table per-say. Those two tables go from idle to 2,000RPM (low table) to 2,000RPM to 5,700 - 6,300RPM (high table) depending on ECM.

It also has a SA main table and SA extended table and that's it. The VE table is not a short or long term table like the much newer ECM/PCM (90s) that you are referring to. Jus sayin'. I'm very familiar with all the ECMs mentioned. By unplugging the ECM on a CFI, it only resets the IACs and will need to relearn idle, it does not reset any VE or SA table.

The OP is talking about early 80s CFI, not late model Camaro/Corvette.

cardo0

Well I'm not going to say your wrong as I have never looked at software and fuel maps for an L83 ECM. But I have looked at the data log for someone having problems with his CFI and I recall seeing short term trim data and long term trim data. And IIRC I observed closed loop and open loop operation. As you describe it there would be no closed loop operation and only open loop operation with fueling control by ROM tables.

What I'm saying is you have to have some adaptive learning to have closed loop operation determined by the O2 senor. Or else what am I missing??

Buccaneer

OK, let me start off by saying I'm not looking for an argument here at all, just wanted to make it clear to the OP what is and what isn't with a CFI system.

So let's start here... There is a chance that you did in fact see what you mentioned. However, if you did see that, it may have been a modified CF with a non-stock ECM installed and that would go along with what you described or maybe the datalog software used may have called it that.

Next...There is absolutely no "adaptive learning" done with a 82/83 or 84 CFI ECM with the O2 sensor (that stores VE settings within the ECM as a function of a trim table). The O2 sensor senses either a lean or rich condition and sends it to the ECM to either add more fuel or subtract fuel on the fly based solely on the mentioned tables high/low. They are not altered as you drive and that's what I think you are saying anyway as "adaptive trim". There is no short term or long term "learning" in ROM for fuel. This is exactly the same with the above mentioned ECMs. The term you are talking about from what I'm seeing is an actual table(s) named short term fuel trim and long term fuel trim in the software which is used with the newer style ECMs. You are correct about that, just not in this case.

Anyway, the 82 ECM was never fully hacked as it were, nor the 83 that I'm aware of. The 84 was hacked enough to make provisions and we used to produce the performance chips for the 84 only. One reason we stopped was it was extremely hard to find the correct chips for us to burn and when we could find them or the prices were very high since they were somewhat rare. Also the failure rate was rather high and not worth the time and effort to create them. BTW: Those 84 chips were actually the same chips that were in commercial arcade game machines.

Red1990VT

Kind of hard to tell what the improvement was. Did you by any chance dyno the car before the modifications, to get a baseline with which to compare the after mod results?

cardo0

So I got a chance to look this up and your right Buc the L83 cars/ECM's did not have adaptive strategy . Adaptive strategy wasn't used until somewhere in 1985 and the L89.

I still want to learn how the closed loop adjusts fuel using the tables. I don't have any software to look at let alone an L83 to data log but I am interested as there are plenty of low mileage '84 vetts on the market and I really like the old school GEN I blocks to. Your RENEGADE intake really enables performance for these cars.

No argument here Buc, just sorting things out.

Buccaneer

Glad you found the info on the CF ECM. Honestly, I didn't think they did that in 85, I thought it was later they started using that adaptive strategy system only because they were still using TBI in late 80s and early 90s.

So, have you ever looked at TunerPro R/T? It is a great app for what it does with the early ECMs. It is different than the other app's out there used for the newer/late model cars in how it displays both VE/SA tables. I happen to like TunerPro only because I have been using it so long and percentages work better for me in my head to work with.

The settings that you need to have the ECM use and control VE correctly in CLOSED loop is vast as you already know. I don't know exactly where to start on that subject since it gets real deep fast.

The ECM settings are not as granular as the later model ECMs. Hence you still have power left on the table at the end of the day of tuning. All you can do is get it close to what A/F you want at idle, cruise and WOT and that's why a heated WB 02 sensor is essential for any tuning and a stock narrow band 02 will not work. You will constantly chase you backside with a NB.

Since the tables are not adaptive and static, you get what you get from each cell by virtue of a percentage and what the 02 is seeing and sending the voltage to the ECM and then trying to maintain that A/F commanded at the RPM. There are soo many variables in this entire process it makes your head spin. Lots of chances to get it wrong and "prang" a motor. The GM manual does have some info on this, but it's definitely in its simplest form.

My best advice on this is... Some of the best, if not the BEST info you can find on this subject on the web can be found on ThirdGen site, http://www.thirdgen.org/forums/tech-boards/ in the DFI and ECM and TBI section. Also, IMO "Rbob" is the most knowledgeable person there to ask. He is a plethora of CFI info dealing with tuning and TunerPro. I'm sure there are others as well. I think that http://www.dynamicefi.com/ also still has some good info on his site too. I could also post a portion of my low VE table if you want to take a peek.

rorrapalooza

Buccaneer, that'd be really great if you could. Ive been mulling over doing an ecm swap to the 7747 ecm pretty hard since ive heard the 84 ecm is "untunable," and ive heard you need a tune to get the most out a set of aftermarket headers.

Since im a college student that is foolish and full of energy but not quite broke, I was thinking of also doing the Tremec TKO-500 swap from Kiesler engineering this summer, but ive heard you need some changes to your computer to go from auto to manual.

regardless, it looks like ive got a lot of reading ahead of me to understand ecm tuning.

eutu1984

I saw this thread over on Gearheads EFI forum and thought it might have some helpful info for what you are doing. Hope it helps. http://www.gearhead-efi.com/Fuel-Inj...rs-please-help

cardo0

I guess I'm not understanding this as keisler has gone out of business and SST bought their assets.

Something along of C4 owners overlook for a manual overdrive is a ZF6 swap from a later model C4 (1988-1996). I believe all the correct parts will swap w/o modification. The ZF6 is a very strong trans though kinda heavy. FORD put a lot of the ZF5 trans in their pickups but I can imagine quite the headache to convert to fit the sbc - but they are strong andcheap.

IMOP, if you're in school spend your valuable time on book study and use cars just for transportation. Unless you have the time to support a major hobby along with the funds it's gonna drag you down and quickly become a burden rather than any fun at all.

rorrapalooza

Sorry, I meant silver sport transmissions

The zf6 is temping, but from what I saw they were expensive unless maybe I could find one out of wreck. I drove my dads 2013 grand sport and found 6 speeds to be one too many for me after daily driving a 5 speed for a few years, but maybe I could get used to it.

Don't worry about my grades too much, I stay focused during the school year, and since I stay focused I get enough scholarship money back to support a hobby or two. I just think that with the career field I'm going into (military), I wont be able to find time to do a full auto-manual conversion until several years after I graduate, unless I can do it over one of my summer breaks.

cardo0

OK Buc, I'll take your advice but research this when I have more time. I need to focus on tuning the trans in my '94 4L60E. I need to fix what my tuner did to my pump pressure and get it to shift at the right RPM. I need to school up on TunerCats software and get this fixed as a priority. It has a slow leak/drip of trans fluid to.

Thx for info and I do visit TGO quite a lot. I see the RENEGADE is popular there also.

cardo0

Well I assume you have the 700R4 trans now. It's just that those are fairly cheap or should I say relatively cheap to your other options. For less than $2k for can have a rebuilt (performance rebuild to) 700R4 swapped in 1 day - any day of the week. This will keep you going when you need transportation.

Now the DN 4+3 is the opposite and can dig you into a hole if you need it for transportation. After market swaps can be problematic and most can't be serviced by anyone but you.

It looks like you are mastering tuning your own car now and that will only help you in the long run for using the car for transportation.

Well enough preaching here and good luck with whatever you choose.

Buccaneer

Yep! It's a great place for ECM info for sure. Lots of material to read. Yeah, I don't go there much anymore since we are not doing business full time right now, but I do go there from time to time to see what the latest is with the CF guys. Seems to be doing well there and works great with a 383 or high cube motor for sure.

Here is my low speed table with 3D graph, enjoy. Sorry, I won't post the high table... kind of top secret, for my build anyway. This is TunerPro R/T early version before version 5. I use this version because I'm the most familiar with this one. The newer version is good, but I didn't want to learn a new app just to finish my tune. Since I'll be changing heads, cam and gear...again, the tuning process never ends. Hopeing to send the car down the track in mid 12s, maybe lower depending on how aggressive I get with the new tune.