The ECM and TCM communicate over the high-speed CAN bus - the TCM also gets info from the gear selector, the steering angle sensor and the ABS module.

The TCM is definitely able to control the engine via requests made to the ECM - it has to, in order to match engine speed when shifting gears. I know I've seen it somewhere that the TCM will also do it if the engine is putting too much strain on the transmission, but I cannot find it in the workshop manual.

 

See what I mean this add popped up as soon as I put up the last post.
Jim




Jaguar Xkr Chip $69
www.gfchips.com

60 Horsepower Performance Chip Dyno Tested and Lab Proven

 

Lots of threads this week about the extent of what we don't know about ECU tuning. Bottom line is that the ECU/TCU will reduce power as it chooses regardless of pulley and ECU tuning of ignition and fuel maps. The power increases shown on the dyno under minimal engine load (strain) are restricted by the ECU/TCU under real world high loads. Seat of the pants impressions under less demanding loads and normal use are that the engine is more responsive, smooth and fuel efficient, and that makes perfect sense.

I think this thread best addresses your particular question. It has the same tune as BigCat09's where he showed a dyno power increase of 90bhp, yet there was no measured improvement in acceleration.
https://www.jaguarforums.com/forum/x...vs-tune-76368/

Bruce

 

Bruce - This also makes sense as my car feels much faster in daily driving, but on the strip I was only able to manage 12.3's at around 117 MPH allowing the transmission to shift. The trap speed is few miles an hour faster than stock tests.

Now that I have the capability to record ECM data it will be interesting to see if the ECM si restricting boost by closing the intake or retarding the timing. One of these was occurring as the car felt like it was losing power at the end of the 1/4 mile.

 

It seems certain the XKR-S has a different factory tune and it is a faster car with more horsepower. So what makes it faster if it is not the tune and horsepower? Suspension & aerodynamics? Something else?

 

Well, looking purely at straight-line performance, compared to a standard XKR it has:

• Different ECM tune
• Performance Active Exhaust
• Stronger torque converter
• Different TCM tune (probably)
• Different e-diff and DSC tune
• Different Active Dynamics tune
• Wider rear tyres
• Lighter wheels
• Better aero

I guess it's the combined effect of all of those.

 

never went over 85mph? I went almost 150 in my 1964 e-type.

 

With the optioned performance pack/active exhaust on the standard XKR the following differences are do not apply (they are the same on both models):


Performance Active Exhaust
Different e-diff and DSC tune
Different Active Dynamics tune
Wider rear tyres
Lighter wheels

 

For the 2014 UK models, the Dynamic Pack and Performance Active Exhaust are now standard on the XKR. Not sure if they've done that in other markets (yet).

And the aero difference between the Speed Pack body kit (which is part of the Dynamic Pack) and the R-S body kit is small - only 1% difference in lift. Might be a difference in drag coefficient, but no-one's mentioned it.

So, the main differences between DGL's car and an R-S are the ECM and TCM tunes and the torque converter.

 

I think the bottom line is that the ECM/TCM combination will reduce power as it is programmed to do, so the conclusion is that real success in tuning the XKR to XKR-S performance levels will most likely involve reprogramming the TCM in addition to the ECM. The interaction between the two units is significant and will affect the real-world outcome. Reprogramming the ECM alone is apparently not enough.

Even though the XKR-S has a beefed up torque converter, I suspect the torque converter in the XKR is probably adequate to manage the increased engine power. Over the long haul it'll wear out quicker if you pound on it hard, but the ZF transmission gearing is the same in both cars. A properly tuned ECM/TCM combination should be able to achieve nearly the same power and shift at the same points as the XKR-S.

The real bottom line seems to be that reprogramming the ECM alone doesn't do the job!

Lots of apples-to-oranges comparison opportunities in the data in that thread, but still very interesting. For straight-line 0-60 acceleration the improved suspension in the XKR-S is probably not super significant, so it's back to this combination effect of the ECM and TCM interacting with each other. Also, the participants seem to feel they have real power improvements available at rolling speeds, but the measured times from dead stop show something is holding back. IMO, this would be consistent with the idea that both the ECM and TCM need to be reprogrammed together if you really want the improved power measured at the dyno to be available when you're out on the street or the track.

It is almost certain that we need to know more about the TCM programming.

Cheers,
Rick

 

I will ask my dealer if the Dynamic Pack and Performance Active Exhaust came standard on my 2014 XKR purchased in North Carolina a couple of weeks ago. This Jaguar USA press release about the 2014 XK series says the Dynamic Pack and Performance Active Exhaust are still considered options on the XKR in the US market.

I tend to agree with your conclusion that the main differences are in the ECM and TCM tunes, and I believe that both need to be reprogrammed if you want to achieve really useful and optimal gains in the XKR while driving. Dyno measurements may show great numbers, but if the TCM or interaction between the ECM/TCM and torque converter siphon that power off what do we really get?

Cheers,
Rick

 

The performance exhaust and dynamic packs for 2014 XKR models in North American remain as options. You can go to topix.com and run your VIN to get the build of your car which will show if you have the above options: https://topix.jaguar.jlrext.com/topix/i18n/index (if you want to pm me your VIN with you email address I will run the build for you and email it back to you).


You can also tell just my looking at the car. The exhaust center "X pipe" of the performance active exhaust replaces the 2 center resonators on the standard exhaust. The dynamic pack also includes the speed pack (body kit with increased speed limiter). If you car doesn't have the body kit it doesn't have the dynamic pack.


Even with the TCM not being remapped most of the 100hp gain from an ECM tune will be realized (and that is if the TCM is holding back the power). All dyno tunes on the XKR show substantial gains. At the very high end of the rev range some dynos show a decrease in the slope of the power; however, the curve never goes below the stock dyno numbers--it just increases at a slower rate. It is only assumed that the TCM maybe causing this. The pulley upgrade has also been mentioned as a plausible cause. This is why I started a survey thread on ECU tune satisfaction. I'd like to show on 1 thread what everyone has experienced with their tunes ad what the shortcomings are: https://www.jaguarforums.com/forum/x...-5l-sc-111917/

 

Rick,

Btw, welcome to the forum. These tuning discussions have been going on for a long time, and you're the most recent to join them. I'm glad you've been reading some of the old threads, and some of the best ones have been in the XF and XJ forums. There has also been off-line discussions where data-logs have been shared and analyzed to see what the ECU is really doing. There's a lot more work to be done, and we have many more questions then answers.

It sounds like your bottom line would accept setting aside some factory safeguards as you think it "should" be okay as these cars aren't likely to be pushed too hard. That would be true for some, but not for others, and depends on many factors. Custom tuning allows owners to take as many risks as they like, often with predictable results, but the mail out type tunes available for these cars would hopefully not have by-passed the factory's safeguards that they spent a fortune in engineering and testing to develop.

I'm one who tracked my car and could have actually benefited from increased performance. The lack of information about the tunes itself, and the questionable power gains when driven under demanding loads, topped my list of reasons why I chose not to touch the ECU. Your interest and needs will be different, but I would be carefully assuming that a tune developed for the XKR-S with known differences "should" be okay on an XKR. If we're going to make assumptions, a good one would be that Jaguar upgraded the converter for the 550 hp R-S model for a reason, and it just might be required when boosting from 510 hp to 600 or more on the XKR.

Bruce

 

You're absolutely correct that there are too many question marks in the underlying data we have available to us, but there's also evidence that a lot of people have enjoyed substantial performance improvements with few, if any, adverse consequences.

At the end of the day it's only money. I've hacked everything I've ever owned, from my childhood bike, to my computers, to my guitars, and why not a Jaguar XKR? Life is short, and I want to have fun. Sure there are risks, but IMO the preponderance of the evidence says the risks are relatively low, and the potential for greater enjoyment is pretty high.

Nonetheless, I would like to get to the bottom of this TCM/ECM interaction issue. I suspect it is essential to getting optimal gains.

Cheers,
Rick

 

I look at it the same way Rick, I've modded anything I've owned my entire life. If it breaks I'll fix it, if my Torque converter blows up I'll get a new one. I bought the car to enjoy and not have anxiety about each and every problem. I've had problems but it takes trial, error and time to sort out a modified car and you have to be patient, diligent and gather as many facts as you can. Which is not an easy thing in the Jag world, but damn rewarding!

 

100hp is a lot to leave on the table. If it can be released with an $800 tune and be reasonably safe it's a huge gain to enjoy.

 

My point exactly! Not easy to get to 600HP on any car for 800 bucks.

 

Thread resurrection - someone on another forum posted a link here on a thread regarding upgrading an XKR to the XKR-S ECU software. I'm interested to know where the belief that the XKR-S has a different torque converter comes from - the part number appears to be the same for all 5.0 supercharged XKR variants? If the R-S had a different/uprated torque converter then it'd have to have a different part number?

 

To my knowledge the torque convertor is the same on xkr/s the difference coming from the tune that is flashed into its tcm, perhaps higher more aggressive shifting points.

 

There does seem to be conflicting information regarding the upgraded torque converter. The press release for the XKR 75 specifically says:

"Upgraded torque converter to handle the increased torque"

And the book that Nigel Thorley wrote on the X100/X150 says about the XKR 75:

"The enhancements included a revised ECU, upgraded torque converter and other suspension, brake and exhaust changes which would find their way into a new XKR-S model."

It isn't clear whether the source for his info was just the press release or whether it came direct from Jaguar while he was researching his book but there have been quite a few discussions on whether the upgraded torque converter really exists including:

https://www.jaguarforums.com/forum/x...ks-etc-176106/