SOHC_MShue

Has anybody used a chipped obd1 ecu to tune an automatic obd2 civic? I keep getting people that want to do this, but i havent heard any definite answer on whether or not it will work or not. I know the obd2 cars are suppost to have a seperate controller for the tranny.

SOHC_MShue

any ideas?

RC000E

Man...I looked at this thread earlier but without my Helm's in front of me I just left it up to someone else. I'm about to go back down into the garage, while I'm down there I'll determine an answer for you. Check back later.

SOHC_MShue

Thanks for checking I greatly appreciate it

RC000E

Well, after doing some reading, being I have to read cause it's not like too many of us deal in auto trannies, I've discovered a couple of things.

Without doing a ton of reading an research based on the hydraulic flow and control in these two trannies it seems pretty apparent that it's not completely cut and dry. I'll explain:

First, knowing the OBD1 trannies have lockup control solenoids, I first attempted to verify that the lockups on the OBD2 trannies function the same and have the same resistance to be sure the OBD1 ecu doesn't get fussy. OBD1's spec out 14-25 ohms and OBD2 12-25, so yes it's highly likely they will agree and function with either ecu.

I then looked at the basic hydraulic control system...and that's when I discovered fuzzy logic.

The OBD2 "PCM" (ECU..whatever you wanna call it) incorporates the transmission control unit internally unlike Accords and what not. The OBD2 cars have gear selection inputs to the ecu along with mainshaft and countershaft speed sensors. The ecu uses these inputs, coupled with the speed sensors, a barometric pressure sensor, and other various system sensors to "learn" the driving habits of the owner. This generally takes more presedence on various grades, and load conditions.

This is where the shift control solenoids and the linear control solenoid come into play. The shift control solenoids actually influence line pressure to the modular valve, etc. blah blah blah. The linear control valve basically works between the shift control and the lock up solenoids. In essense, with these "line interrupt" solenoids, the ecu can influence how and when the tranmission shifts.

There is though still a basically identical tranny beneath all the addition equipment that goes along with the fuzzy logic system. See, the basic OBD1 tranny is more simple, load based, shift at certain speeds, when certain pressures are reached, as to where the OBD2 tranny can shift more freely based on driving habits and load. It essentially allows the ecu to choose which gear to place the tranny into, versus having a more manual system.

Now, based on my own logic, and my prior limited experience with trannies, I suspect that upon the failure of this fuzzy logic control system that the tranny will still function. I believe it will basically fall into functioning more like the OBD1 variant. In my experience though, as far as running trannies with the lock up disabled, tranny life will suffer a bit.

So, in the end here, I can't give you a 100% yes or no. I can say though, if I had the options before me...yeah I'd try it. I believe that the tranny will still function fairly normally. Things I don't know though are how harsh it may shift, if it'll hold certain shift points, or if you'll have any driveability issues.

If I could find a willing test subject, I'd definitely try it out.

Sorry I couldn't help more.

SOHC_MShue

thanks for finding all of that info for me. Interesting stuff for sure. I think i may have a couple of people that will be willing to let me test this out so we shall see if it works out or not. Hopefully it does because using emanage or something of that nature sucks. I've used that before on an auto obd2 civic and it isn't fun to mess with.

JDMs1eeper

nice Matt. Let me know too. I need to convert Courtneys car to obd1 to get tuned this summer.

Thanks RC000E