I know this, but the more modern the vehicle the more cost and mutilation of stock systems are needed. Right now I am just talking about 97+ XJ system, which is rather simple but still offers a bunch of problems to solve.Plechtan wrote: A. Megasquirtand other ECU systems are used on many street cars, Not just drag cars.
I don't know what the PCM would do if it was disconnect from the injectors, but I do know if you disconnect it from the coil rail it will throw a code. Also, the PCM will set a code if it is seeing 12.5 AFR at the O2 sensors when it wants 14.7. And what stock sensors can MS use? Would it be able to use the stock cam sensor on a distributor less system? What about the CPS? Sure you could go with the Hesco CPS relocation, but that just adds to the cost.B. A aftermarket ECU can be hooked up with the factory ECU, the sensors run to both units, but the injectors and ignition are controlled by the aftermarket unit. If you tune it right, you should not pop any codes.
C. The AW4 Is controlled by a TCU ( transmission control unit) the later model TCU gets its RPM signal through the Can Bus, but eariler units read it directly. So you could go to an eariler TCU. Their also useto be a guy making a box that would let you shif the AW4 manually and elminated the TCU.
97+ XJ TCU gets the RPM, torque converter clutch control, and a few others inputs over the CCD bus the PCM or a stand alone wire. They don't use the CAN bus, but the TCM needs the PCM. Yes, you could change to an earlier TCM but the PCM would throw a code because it also needs input from the TCM as well as the cruise control is gone.
One a older car with less computer controlled crap, or like his, a drag car, it wouldn't be too difficult. I am not very familiar with the OBD I jeep setup anymore, but on OBD II (96-97+), for all the reasons stated, it would be a major under taking and major expense.D. Megasquirt is not as much as a challange as you may think, Perhaps Tom could give us some more details on his install so you can get some idea of the work involved.
I agree with Tom as well that there is something left on the table using the stock system. And like you I enjoyed programing the Apexi.gradon wrote:Now that we've officially sidetracked the comp cam thread, that will work with fuel injection, here's my thoughts: I agree with both Chris and Tom. I loved tuning the psc1--it was a very fun process to wot down 50 with Nick and the laptop next to me, pull over in the shoulder, tweak a value, rewrite to the module, and do it all over again. I could only adjust the fuel, not the timing, and really only the open loop fuel trims.
If you have access to someone that can tune it for you locally. Its also plug and play, which is nice. And I know it can change other items much like a re flash can, but I don't have all the details on what.For obd2 Jeeps I think the best solution is the Unichip, due to the way it completely interfaces with the 3 harnesses going into the pcm.
I don't think that reflashing the JTEC 97+ PCM would give you much more power. You will still be forced to use the PCM's open and closed loop points and its emissions friendly back bone. Reflashing the PCM does have the ability to change a whole bunch of other stuff besides the fuel and timing tables.Another great option is the reflashed pcm.
Agreed, MS is probably better suited for use on earlier Jeeps.But for 95 and older jeeps, MS would be a good option for the DIY'er.
I'm not saying MS is a bad thing, or that it shouldn't be done. Its just that there will be trade offs, a lot of effort and a lot more cost that $300-$500 when all is said and done.
