I had my 1989 TWR Coupe converted to a Getrag 265 5-speed manual transmission back in October. In preparation for that conversion, I purchased 16CU ECU unit from Just XJS in the UK and shipped it to AJ6 Engineering in the UK to have it re-mapped as a “Super-enhanced ECU” for a 5-speed manual transmission. Since installing the SE-ECU, my car has run terribly. When I re-installed my OEM ECU, it ran fine, although not all that exciting. I purchased the re-mapped ECU from AJ6 to make the car faster and more fuel efficient. But the SE-ECU made the car undriveable. It sputtered and lost power when accelerating above 2500rpm.
I complained to AJ6 that the ECU is not programmed correctly. We wrote back and forth for months with no real solution. I offered to ship the SE-ECU back for troubleshooting, which eventually I did. Roger Bywater, the proprietor, tested it and reported there was nothing wrong with his ECU, that it must be “the car,” without specifying what that might be. He suggested changing out the O2 sensors. I found a post here from 15 years ago where a purchaser of the SE-ECU reported very similar symptoms to mine, and he resolved that problem by replacing the throttle potentiometer.
I got the ECU shipped back to me from AJ6 just earlier this month. I reinstalled it with new O2 sensors and a new throttle pot. SAME PROBLEMS! Car runs beautifully with the original ECU, but again, there is no noticeable improvement in performance with the original ECU. The Getrag transmission makes the car much faster, but I paid a considerable amount for the ECU that appears not to work.
Testing the throttle pot with the SE-ECU, it runs rich with a minimum idle of 2000rpm, and when I hit the throttle, it still sputters and sounds like fuel is flooding the piston chambers. Heavy sulfur odor from the catalytic converters working overtime.
I’ve re-installed the original ECU again for now. Does anyone have any suggestions as to how to get this to work with my car? I wonder if the re-map for a “manual” is just running too rich for the engine.
Why would the car run fine with the original ECU but terribly with the re-map designed by the man who created the emissions system and the original ECU?
Used stock standard tuned OEM ECU, but had different fuel pressure or different injectors.
Used stock fuel pressure and injectors, but a modified ECU.
Did TWR have a different CR or different camshaft to standard ?
Do you know exactly what is different about the TWR engine ?
Even so, have POs changed anything you do not know about ?
I hope your exchanges with Roger have not sunk into hostilities.
There is not a lot you can do with the OEM ECU.
He could only change the fuel map cells which are determined by RPM and manifold vacuum. That takes into account timing advance which is a function of what Lucas did with the dizzy.
The HE engines do have the fuel pressure modulated by the vacuum but that all comes out in the wash anyway. Different story if you use a non modulated FPR.
My guess would be Roger has made assumptions about your car concerning the above issues. Chances are one of those assumptions is not correct.
I hope you can easily check the FPR and injectors to see if they are correct part numbers. You could have the dizzy checked by an auto ignition specialist.
If not sure about the camshaft you could take off the cam covers and check the part number on it.
As your car runs well with the original ECU, maybe if Roger had that as well as the SE-ECU he can see what is the difference that accounts for the poor running you report.
if you could borrow a third ecu, that might help determining if your original is mapped differently than stock. of course, you could also borrow another xjs and try both ecu’s in it.
Unfortunately, I am not certain what, if anything, is different about my particular engine or ECU. I suspect that my particular TWR was really just a cosmetic/appearance variation without any performance modifications. My mechanic has told me that there appears to be nothing out of the ordinary about my TWR powertrain as compared to a standard XJ-S. I will double check with my mechanic to see if he thinks there could be a different fuel pressure or set of injectors.
I provided my VIN (SAJNA5846KC149023) to Bywater at the time he created the re-map and told him it was cat’d for California with a Marelli ignition. The substitute core ECU was part no. DAC6338, which he told me meant that it was a non-cat’d Marelli car. He told me that didn’t matter, because he could re-program it for any purpose.
No obscenities have been exchanged, but frustrations have been voiced.
I cannot add much other than to say l have had my ECU reworked by Roger along with 2 fuel map chips and have had no issues.
Your original Vin# will most likely be of very little use since so many of the changes carried out by TWR were not documented.
This is a bit of a late reply, but I have a similar setup to you, with a 5 Speed transmission and the modified 16CU from AJ6. I too had been chasing some running issues. Mine mostly manifested when the car was hot, it would act like it had a bad case of the vapors and power would be down like it wasn’t getting enough fuel. After replacing a few parts (fuel pump, O2 sensors). I determined that it was the alternator.
When the car was hot, both my aftermarket electric radiator fans would be running, plus the AC, etc. The alternator must’ve been tired and wasn’t generating enough power and the car was effectively running on the battery. (Battery gauge would show just under 13 volts). I replaced the alternator and it has transformed the car. - Battery gauge shows above 13 volts when hot and now I can drive it like any other car. FWIW - My car has the Bosch 115 Amp alternator, I did not replace it with a more powerful unit.
Thanks for your input. Unfortunately, mine runs the same, hot or cold. Plus, it runs perfectly with my original ECU installed. Problems with the engine sputtering and choking on fuel while accelerating only occurs while the AJ6 Super-Enhanced ECU is installed in the car. If it was a bad alternator, I imagine it would do the same thing with either ECU installed. Wouldn’t you think?
We will try a pressure check next time I get my mechanic down here. Even so, why does the car run fine with the original ECU? I sent the SE-ECU back to Bywater and he insists it is mapped “correctly,” which I doubt. Or at least I doubt it is mapped correctly for some pre-existing condition in my car. I hate trial and error and it costs a fortune to ship the ECU back and forth.
So the enhanced ECU causes an apparent overfuelling when you accelerate ?
But not otherwise ?
Is that the crux of the problem ?
On top of the base fuel map the TPS will add fuel if rotated rapidly.
The ECU is supposed to add more fuel the faster the TPS rotates.
You can try accelerating less aggressively and see if that makes a difference.
The idea is to see what happens at the same throttle position and RPM with both rapid and slow rotation of the TPS.
If you have a steep hill you can drive up it and try and maintain a fairly large throttle opening and particular RPM to duplicate an engine condition causing you grief when you accelerate on the flat. The hill climb will be steady state, the TPS not rotating rapidly.
I doubt if Roger fouled up the base fuelling map, I expect he made it a bit richer for those operating conditions you want such as better acceleration. I am not sure if he did increase the effect of the rapid rotation of the TPS. I bet you could do that within the ECU if you wanted.
It could be the original ECU claimed to work O.K. is just below the overfuelling limit that prevents ignition. The enhanced one is just above that limit, at least under some operating conditions.
I can see your point about changing ECU’s making the difference. But when you change these, you DO have to disconnect and reconnect the vacuum line to the side of the ECU. If there is anything about that connection that differs (maybe the orientation of the vacuum line is slightly different, as it plugs into the ECU), that can lead to a vacuum leak, this would be problematic.
One way to check this: the other end of the vacuum line connects to the intake manifold balance pipe, which runs across the rear of the engine. At the rear, center of this pipe, you will find the vacuum line. If you take that loose, and put a plug in the rubber hose (find a large screw or small bolt and push it in), and then, go to the boot/trunk, and take loose the vacuum line from the ECU. Blow into it; it should be impossible to push air (since it is plugged at the other end). If you can push air, you have a leak somewhere; you may even hear it, if the leak is in the boot.
Roger’s mapping of the ECU for the SE-ECU package does indeed increase fueling over the stock factory map. And the stock factory map runs a bit rich anyway. So, if you have a richer map and a slight vacuum leak, this would lead to symptoms you are seeing.
Checking for the leak should take more than 10 minutes.
FYI: Roger’s work on these ECUs is to remove the chip, solder in a socket, and then place a new programmed chip in the socket. I have read these chips out for several of his offerings, and I know the changes he has made to the programming. There’s not much on the SE-ECU, modified for a manual transmission: slight richening of the fuel map, and deleting the overrun cutoff that is required for the automatic. The change for a manual is one byte, literally. Roger is able to test these ECU’s, and I am pretty sure he does this, to be sure to avoid the very situation you are having (e.g., customer claiming a bad ECU). Of course, it IS possible you DO have a bad ECU, but let’s eliminate the other possibilities first.
Always a good idea to make 100% sure the ECU sees accurate vacuum signal and clean RPM signal.
If you do have a vacuum leak the ECU sees what it thinks is larger throttle opening than actual, and that moves the operating point on the fuel map to a longer injection pulse and more fuel.
My experience with the manual conversion was the engine stalling between shifts, which I read about before hand might happen, caused by the “overrun cutoff”. I sent the ECU over to Roger describing everything. The other mod I made was replacing the stock fuel regulator’s with an adjustable one, increasing the fuel pressure to 40 psi cured my "hot engine restart stalling fiasco " Aftermath is no stalling & runs great.
Mine is Marelli as well ('89 model year, built Feb '88), My mechanic has been asking around and heard from friends that maybe the SE-ECU wasn’t as compatible with a Marelli. Yours took a little customized adjustment but otherwise worked out, correct?
Have you tried dropping the fuel pressure to confirm it’s overly rich? An adjustable FPR would let you drop the mix across the whole range. What’s the current fuel pressure?
