1984 Jaguar XJS V12 5.3L HE (11.5:1 CR)
Posted: Tue Feb 17, 2009 4:47 pm
Hi all,
I just recently converted my 1984 Jaguar XJ-S to Megasquirt after getting tired of tweaking with the original Lucas 6CU ECU. I wanted to leave the original wiring as stock as possible so I could go back to the original Lucas ECU if I had to (smog checks, fried Megasquirt, etc.) so I ended up cannibalizing a junk Lucas ECU for the case and connector, and grafting the Megasquirt-II v3.57 onto it:
http://crosstalk.atomz.com/~ross/jagstu ... 999857.jpg
http://crosstalk.atomz.com/~ross/jagstu ... 066320.jpg
http://crosstalk.atomz.com/~ross/jagstuff/megasquirt/ (tuning files)
The Megasquirt was purchased fully assembled from DIY Auto Tune, along with an adapter harness and some GM coolant temperature sensors that I didn't end up needing (used all the original sensors, just had to change the wiring for the IAT sensor so that it referenced to ground and not TPS vref.) The modified ECU case tucks into the original location in the trunk, and aside from a serial cable snaking out of it and heading into the passenger compartment it looks completely stock as it's mostly hidden by the carpeting in the trunk. The stock injector resistors are bypassed and the Megasquirt is running in peak and hold mode with a 1.1ms open time and the pwm duty cycle set at 21%. The firing mode is set to 4 squirts per cycle alternating, with both cylinder banks running off of one VE map and the passenger side 02 sensor. I connected a WB 02 sensor to the driver's side O2 sensor bung and used it for tuning, but haven't bothered to switch to dual VE table support with two O2 sensors as the difference in AFR between banks when working properly is negligible.
Right now the system is handling fuel injection only with the timing signal coming from the output of the stock Delco HEI ignition. I have the ignition output of the Megasquirt connected to the full load signal line coming from the vacuum switch mounted in the engine compartment, that way I can drive a MSD ignition box or possibly another HEI module to control ignition timing at some point.
A future project may be to move the Megasquirt ECU to a location underneath the dash (there's a nice spot underneath an access panel in the engine bay where a vacuum reservoir currently resides) to shorten the cable runs and remove the need for a vacuum pipe running the length of the car, but that would make the installation decidedly non-stock.
Overall, I'd have to say this is the best modification I've done so far on this car. The throttle response has greatly improved, the engine starts and idles better than it ever has, and it pulls better at WOT as the original ECU was running way too rich at full load. It can also break the wheels loose on dry pavement, which is something it never could do before no matter how well it was running. It feels like a completely different car, thanks Megasquirt!
- Ross.
I just recently converted my 1984 Jaguar XJ-S to Megasquirt after getting tired of tweaking with the original Lucas 6CU ECU. I wanted to leave the original wiring as stock as possible so I could go back to the original Lucas ECU if I had to (smog checks, fried Megasquirt, etc.) so I ended up cannibalizing a junk Lucas ECU for the case and connector, and grafting the Megasquirt-II v3.57 onto it:
http://crosstalk.atomz.com/~ross/jagstu ... 999857.jpg
http://crosstalk.atomz.com/~ross/jagstu ... 066320.jpg
http://crosstalk.atomz.com/~ross/jagstuff/megasquirt/ (tuning files)
The Megasquirt was purchased fully assembled from DIY Auto Tune, along with an adapter harness and some GM coolant temperature sensors that I didn't end up needing (used all the original sensors, just had to change the wiring for the IAT sensor so that it referenced to ground and not TPS vref.) The modified ECU case tucks into the original location in the trunk, and aside from a serial cable snaking out of it and heading into the passenger compartment it looks completely stock as it's mostly hidden by the carpeting in the trunk. The stock injector resistors are bypassed and the Megasquirt is running in peak and hold mode with a 1.1ms open time and the pwm duty cycle set at 21%. The firing mode is set to 4 squirts per cycle alternating, with both cylinder banks running off of one VE map and the passenger side 02 sensor. I connected a WB 02 sensor to the driver's side O2 sensor bung and used it for tuning, but haven't bothered to switch to dual VE table support with two O2 sensors as the difference in AFR between banks when working properly is negligible.
Right now the system is handling fuel injection only with the timing signal coming from the output of the stock Delco HEI ignition. I have the ignition output of the Megasquirt connected to the full load signal line coming from the vacuum switch mounted in the engine compartment, that way I can drive a MSD ignition box or possibly another HEI module to control ignition timing at some point.
A future project may be to move the Megasquirt ECU to a location underneath the dash (there's a nice spot underneath an access panel in the engine bay where a vacuum reservoir currently resides) to shorten the cable runs and remove the need for a vacuum pipe running the length of the car, but that would make the installation decidedly non-stock.
Overall, I'd have to say this is the best modification I've done so far on this car. The throttle response has greatly improved, the engine starts and idles better than it ever has, and it pulls better at WOT as the original ECU was running way too rich at full load. It can also break the wheels loose on dry pavement, which is something it never could do before no matter how well it was running. It feels like a completely different car, thanks Megasquirt!
- Ross.