OK so we all know my last tune was with eurocharged and the results were great! After sometime the performance dropped off and the car felt stock.

So today RSC flew in the guy actually writes the tunes for the majority of these companies. He used to write the tunes for the Porsche factory and also worked at Bosch dealing with ECMs so he knows much more than anyone I've spoken to. He wants to stay unnamed but I can contact him with questions and will see him again Friday for a final look over before he leaves.

So today when I brought the car in and placed it on the Dyno it put out 348 HP at the wheels so I was dead right about it losing power. Now why it was loosing power is more complex than it losing a tune. The Eurocharged tune was still in place but not being used as it was not properly referenced in the "mapping table" in the ECM. The interesting part is why it wasn't being used.

I'm going to explain this the best I can, but Jag/LR ECMs have 8 tunes. One is flashable and the primary tune. This is what Eurocharged and all the other companies flash. The other 7 are not flashable and are used when the ECM detects an out of parameter soft or hard fault. The Eurocharged tune is awesome but it caused an intermittent misfire which is no big deal, but when the ECM adaptation detects that misfire a certain number of times it knows to default to tune 1-7 until that condition is gone. Keep in mind these conditions are hard coded and can not be changed. Once the condition has stopped for a certain amount of time the ECM notes that then has to determine which tune to go to. Normally this should be the flashed primary tune, but if a checksum is wrong, which in my case it was it again thinks something is wrong and stays at that tune. This checksum CANNOT be set unless the ECM is in the car when the tune is applied and must match what is in the ECM. If not soon as you step outside of a known parameter a number of times you will end up with one of the 7 static limp home tunes that protect the engine from the particular issue that the ECM has detected. This is why you can pretty much lose every senor but a crank sensor and the car will still be somewhat drivable.

Whats even more interesting is that there are higher performance tunes already on the ECM you just have to map to them correctly and change the checksums. We could have used an existing factory Jag tune and gained 40HP, as the maps are already there.

Now lets look at the dyno the blue line shows what the car dynoed at when I brought it in this morning. Pretty bad after getting 530HP at the wheels after the tune. Once he cleared the misfire, changed the checksum he found a problem in the Eurocharged tune. If you look at the other screenshot you see the long term fuel trim which is set to -4.7% across the entire rev band. This was also causing a problem and setting off soft codes especially when the car was pushed. He set that back to zero cleared the misfire, and in 95 degree near 100% humidity it did 500 rear wheel HP which correct for temp which puts us back around the Eurocharged 630HP. Also keep in mind the ECM retards the timing in 95 plus degree weather.

He had nothing but bad to say about the Eurocharged tune and said there timing was spot on and looked great. So please by all means they did a fine job but missed some steps that ALL tuners with Jags are missing as they are not the ones writing these tunes, but maybe modifying them. This is something that he has been trying to figure out for months as my car is not the only one having this issue.

I also have to mention another tidbit of information I found out which is if the ambient temp is 95 or more for a set period of time(forgot how long) the ECM will revert back to a safer timing to prevent pre detonation. until the ambient temperature is lower.

You can get the ECM back to the primary tune by disconnecting the battery but as soon as it cross the parameters you are back to square one due to the check sum..

So to sum it up the adaptation was causing the problem and will continue to do so. He made a couple changes to the Eurocharged tune so we don't cross have the same problem again but if I do it will eventually revert back to the proper tune. He also made some changes to adapt to my high flow cats which are now being installed. It wont affect top end HP but will increase power in the midrange.

I'm picking the car up tomorrow after the cats are installed and will drive it a few hundred miles and he will check the ECM for any of these adaptation errors and try to resolve them.

I have to thank RSC for connecting me with the ECM guru and Eurocharged for having a powerful tune, but I wish they would have communicated with me instead of telling me what I was telling them was impossible, it obviously isn't.

So thats where we are now with ECM tuning on these cars, I'm going to continue working on this and hopefully will be able to stay on that primary tune more so than not.

He also lifted all the TCU limits and update the software as well as changing the shift speed which is now 22% faster. Huge difference in the how the transmission feels and the power that you actually feel.

If you have any questions please let me know and I will ask the tuner when I see him Friday.

 

Great info. Amazing to see that 8 separate tunes are loaded into the ECM. I do not understand the checksum portion. Does that mean that once the ECM reverted back to tune 1-7 due to a misfire and after waiting a set period it wants to go back to the primary tune, it simply does not recognize the custom tune because it can not identify it correctly as the primary tune? Wonder why 7 additional tunes, what is the difference between them. Seems to me that even if that "checksum" is correct, if you push the car on a hot day or simply push it hard enough, it may automatically select one of the alternative tunes, in your case one with nearly 200 HP less. Wonder if that can happen to the stock tune, as well? Last week I drove my stock XKR on a day with temps over 100 F and it definitely did not feel as fast as it did before. Hope it is temporary...

 

Yes the flashed tune had the wrong checksum.. look at it this way you are reading a book at page 17 for performance, for whatever reason you started reading another chapter. Now you want to go back and look in the index and guess what its telling you performance is page 48 which is wrong. So checksum is more complex as it may be used for validation of the tune, and verifying its a valid tune for the vehicle..

The other tunes are limp home tunes and some adaptive to the environment. Lets say you lose a cam sensor, but all other systems are reporting correctly. So instead of leaving you in the side of the road, it knows in this situation to use lets say tune 3, and throw a warning light and code. At the same time that tune will limit certain engine functions until you can get the car to the dealer. Once the sensor is back online and the code cleared the ECM looks for the "Primary" tune and if the checksum is wrong it will just stay where it is, not throw any codes but will leave you in a degraded state of power and usability.

Older ODB I systems and less advanced current systems would just throw you into a single limp home mode or just shut down altogether. So its a good thing but annoying if you are trying to extract more HP.

 

So should I now be good to go with getting the tune done on my 4.2 at your shop? Will your guy be able to do the tune rather than Eurocharged?

 

Personally I'd use RSC now, as Eurcharged just wrote me off and basically told me I was crazy. There is a dyno sheet here to confirm that I was correct. That leaves a bad taste in my mouth, sorry Jerry that was not cool. Although your tune is awesome, I can't deny that fact.

Plus the amount of knowledge I received today from someone who worked for Bosch designing ECMs and programming works Porsche race cars was more than every tuner put together x10. Plus I got the TCU tuned and the limits removed. I also have the tune on a handheld plug that he showed me on the dyno and PC that it works correctly. He also explained why the first one he gave me didn't work and the changes he made. My car was the test bed as its had the most problems with any tune because it sees regular track use. The car feels amazing now with the ECM and TCU tuned.

So if you want the total package, a tool you can keep and good support I have to say RSC.

 

yes sir start driving!

 

Wow, you must be happy to have the tuning guru look at your issues and explain to you what is going on. Very interesting stuff.


So now that you have the eurocharged (or should I say tune of your choice) tune applied as the primary tune with the correct checksum your car should revert back to it if for some reason your ECU shifts you out of it to one of the 7 hard tunes. The question is how long do you remain on 1 of the 7 hard tunes before your ECU reverts back to the primary tune and how often this is going to happen.


You mention one of the tunes has a hp increase of 40. I wonder if this is the tune used as the primary tune for the XKR-S.


Sounds like you have everything under control. You just need to find a way to keep your ECU in the primary tune. Great to hear you also had the TCU limits removed. Your car must be a beast. Thanks for the update much appreciated. Start Your ENGINE!

 

When I see him Friday for a "check up" I'll ask some more about what causes it to move between tunes and what they are for. It was a lot of information to take in over 3 hours and I asked A LOT of questions.

I'm thinking the S tune is on the ECM but I'm not sure so dont quote me just yet.

Yes I'm running the Eurocharged tune, he made a few changes to it but said it was a solid tune and not worth the amount of time it would take to get say 20HP.

 

This is all great news and excellent info! I searched but could not find your post referencing the first tune you ever had done. I was searching because I thought you had RSC do that one and had a problem with it hence your choosing Eurocharged.

 

..to take a working holiday in Aus, let me know!

 

I did have a problem with their first tune as it was a self tune and did not apply itself. Later they showed my why and also took the time to describe my problem to the tuner and flew the guy in for a week. I paid for two tunes and RSC responded to my issue while the other ignored me.

 

Ask him if he's planning any trips to Greece, I've got a room for him and a guest if he brings his laptop

 

what a journey ... great write up Max.

 

The high flow cats are going on today! I can't wait to hear it!

 

Start your engine and let the cat roar!


Finally! Looks like your perseverance paid off. Kudos to you Max! Enjoy!

 

Is there any way to know if ETS is doing the same thing as Eurocharged or has Jags learned to use correct checksum?

 

I was thinking the same thing. We should direct him to this thread and ask him...

 

In a different thread, and there are many on tuning the 5L SC, I suggested the tuners all put their knowledge together and work together to figure out how to configure a tune for these cars for the betterment of the tuning industry and the community. They need to figure out how the ECM and TCM work to create an effective product to sell. Then the individual tuners can package, differentiate and sell their finished product with confidence. This is how an industry grows and develops a product to serve the general community.


Many legitimate questions and concerns have been raised in the tuning threads with no satisfactory response from any of the tuners. They have simply been messing around with our cars. This is the only intelligent explanation we have on how our cars ECM actually functions. This leads me to believe most tunes provided for our cars are ineffective because the tuners simply just don't know how the ECM functions. Although their maps may be good they can't be effectively deployed. Finally, we have an explanation that makes sense.


I have been interested in having my car tuned for sometime to unleash all the reserved power to take it from 510hp to around 620hp. However, no tuner could confidently explain the effectiveness of the tune on the car. Without any confidence in their product I refused to buy into it. Finally, we are getting somewhere to understand how a tune works on our cars. Kudos to Max for his perseverance and tenacity. I'm sure there is still a lot more to learn about tuning these cars...

 

I'm going to give Jags a call tomorrow. I will direct him to this thread and see what he says. I have been think about getting my ride re-tuned anyway.

 

I'll be waiting to hear about Jag's opinions as I plan on getting his tune after I get my car back in a couple of weeks.

Thanks Ralph.