A few of us are interested in adding a little more power, considering pulley and/or ECU upgrades, and it would be worthwhile to know how Jaguar themselves did it on the XKR-S. I hope some of you know and can fill in the blanks. I recall reading something about what they did, and I think it was with modifications to the intake manifold and/or cylinder head, as opposed to running higher boost levels by changing pulley sizes.

If they did it that way, that is a very good way to make more power as the engine will make the added power with a minimum of added stress. Basically a supercharger spins and pushes more air into the engine under pressure. The act of pressurizing air heats the intake air, and the factory intercooler's purpose is to reduce that heat before it enters the combustion chamber. Higher boost pressure increases air temps, and the problem of hot intake air is three-fold.

Hot air is less dense, and that reduces the amount of oxygen used to create power from. You may have heard the term "heat soaked", and that refers to the loss of engine power caused by the intercooler and engine's stuggle with the higher temps. This can normally occur when driving in very hot weather and when driving aggressively in motorsports, with both over-whelming the intercoolers ability to keep intake air temps (IATs) in check. Power is lost in this way, as well as any intervention from the engine's management system to keep it running safely.

Higher IATs also increase the propensity of pre-detonation in the combustion chamber. That is basically the air and fuel mixture self-igniting prior to the actual spark from the spark plug. Engine management likely includes a knock sensor which "listens" for detonation and gives constant feed-back to the computer which adjusts a variety of things to prevent harmful detonation. The use of high octane fuel reduces the propensity to detonate, but the "requirement" to use it as opposed to "recommendation" to use it may indicate that the engine's ability to protect itself may be limited.

And lastly, high IACs raise exhaust gas temps (EGT) and that's not good for engine longevity either.

It's common when increasing boost levels on forced-induction engines to increase the intercoolers size to effectively reduce the IATs. The stock engine's intercooler is not effective enough under stock boost levels under aggressive or hot driving conditions, so raising boost levels higher does require comprehensive consideration.

Engine management tuning is an approach to allow an engine to handle higher boost levels. Higher volumes of fuel injected can cool combustion temps, and ignition advance/timing can be dialed back a little as well. The engine's management computer will also have many sensor inputs that it uses to adjust operation, and safeguards to try to reduce damage. The extent of the tuning, changes to factory safeguards, and the conditions under which tuning was performed, will dramatically affect whether the tuning will protect satisfactorily. Tuning on a dyno is one thing...and tuning under real-world conditions in hot weather, at high and low altitude, and under high-load conditions typical of motorsports is quite another.

Jaguar would have spent millions of dollars to perfect the engine management system, and if we are to trust a re-tune of that we should insist on a comprehensive explanation of what changes were made to the factory tune, and under what conditions it has been tested so we can understand the risk of using their tunes.

One approach to more effectively cope with high intake air temps is to use something called water-injection. This can basically be either a single spray nozzle injecting a fine mist spray into the pressurized airflow entering the intake manifold leading to the combustion chambers, or individual injectors spraying into each individual cylinder chamber (direct injection). The water droplets vaporize in the airstream, and absorb heat as they change state from liquid to vapour. I don't know which, if either, have been successfully used on the XKR, although I have seen reference to some trying it.

I've used both water-injection and a custom tuned ECU on a car I've used on the road course for a number of years. They've allowed me to significantly raise engine power with higher boost, and survive the stresses of motorsports. And I'd be quite happy to find a safe power upgrade path for the XKR!

Bruce

 

Here is a link with some more info:
http://newsroom.jaguarlandrover.com/en-in/jaguar/press-kits/2011/03/xkr-s_12my_press_kit_010311/

The engine is hold back from the start, not without reasons of course, for 1 they topped of the torque curve to preserve the gearbox for instance. Am not sure if all so called tuners understand the ECU thoroughly enough and know how to tune it right. But 1 tuner seems to already have proven that you can push it just on an ECU tune already to 590 bhp. Am not saying this is a safe tune, as you rightfully say, it will depend on how/where you use also.

I have been pioneering for many years, and it has been proven now that the "old" 4.0/4.2 blocks are pretty strong, but this remains to be seen for the new 5.0 ltr engine.
All will depend on usage, full power all the time (ie track use) or occasional power usage/street driving. For the latter you could increase obviously the power more before you start fatiguing material due to heat.

The mild boost level increase from a pulley on the 5.0 SC (so not to be mistaken with one on a 4.0/4.2 engine) will not push it to the limits in that you would require water-injection systems, although again it depends on the usage.

What is the plan in terms of how you want to use the power, and how much do you want to add?

 

Thank you for the link and information. The article claims the power increase came from a different fuel tune and performance exhaust ...

"The surfeit of power produced by this system meant that it was a relatively simple matter to liberate an extra 40PS and 55Nm over the standard XKR. Remapping the engine's fuelling characteristics and increasing exhaust gas flow through the use of an active exhaust system has lifted total output of the 5.0-litre V8 to 550PS and 680Nm. This is the most powerful Jaguar road engine ever made and allows the XKR-S to hit 60mph in 4.2 seconds and reach the magical 300km/h barrier with ease.
The Performance active exhaust system that helps provide such spirited power also produces a thrilling motorsport-inspired soundtrack to aurally reward the enthusiastic driver."

I'm assuming the performance exhaust improved engine airflow at the stock boost level, and the air/fuel ratios were leaned out a little to make more power from that airflow. That may have been as far as they needed to go to make the desired power increase necessary for this upgraded model, and maintain reliabilty under varied use. Others could probably push this engine to well over 800 hp.

I'd be quite happy with an additional 40 hp to avoid warranty and reliability concerns, and even that would likely challenge a variety of things when I occasionally run it on the race track.

Bruce

 

Then personally I would go for just a tune and maybe an exhaust as well, though the price for the latter will be relatively high for what you could achieve. At least it will be less obvious that you have changed something with just a tune compared to a pulley or water spraying kit.

But regarding the tune, I would investigate first very well if the tuner thouroughly understands the ECU programming. For one they need to be able to detect and remove the current restrictions, and next need to understand what the best combination is for improvement. It is not just air to fuel rations, but also ignition timing and possibly valve timing. Not something everyone just knows and understands, and only very few might have info about the original map with details where to find what (invaluable ;-)).

Some EU tuners do offer a warranty with their tunes, but not sure how that would work between countries though, and last but not least, as the engine is relatively new (/new technology), chances are high that Jaguar will come with new versions of software, so check if the tuner already does the latest, and also what it would cost to retune it when an important fix has come out form Jaguar.

 

All good points to check...thank you. 40 hp without increasing airflow with a lower restriction exhaust or pulley kit would definitely need more than fuel tuning. I think it could be tough to find someone to trust the computer tweaking to. Hopefully the vendor's ECU tuning thread will end up instilling confidence. Thanks again.

Bruce

 

Here is just an example tuner, that offers even a free warranty:
Customchip Jaguar XKR 5.0 V8 Supercharged 75 510 pk

 

I'm feeling fairly certain as to the direction I would want to go to make more power, if I can satisfy myself about some issues. My main concern is managing temperatures under occasional track use where heat is a problem for basically all stock cars. While the stock air-to-water intercoolers are perfect for street use, prolonged high load use can easily over-whelm them. Running the supercharger at higher boost with a pulley change is just going to make things worse. Water-injection would manage this problem, but installing that while it's under warranty could create a whole set of other problems.

I could try to make more power by increasing airflow at the same boost level with a lower restriction exhaust, but I just can't see a cat-back system being much of an improvement over the stock active exhaust. The main restriction would be the catalytic converters, and the available cat-back systems do not remove those. If anyone has results to the contrary please let me know.

So that leaves tuning the ECU to run leaner air/fuel ratios and more advanced ignition timing. If either of those were tuned too aggressively they could cause pre-ignition (detonation), so the key will be to tweak them carefully. I can also use higher octane gas (94) on the track to pull me back from the threshold of pre-ignition under track conditions.

I'll be following the discussion in the ECU Tuning Group vendor thread, but I don't want to clutter up their thread, and will update this as more information becomes available.

Bruce

 

Have only experience with a sports cat on my car, and there it does help a little in performance with the stock exhaust, and also adds more sound. But for just performance it would be too expensive for the little it could gain.

I agree with changing boost levels adding addition heat, so for track days it would better go for just the ECU Tune, I would contact ziptune also to discuss it with them; their tune only version with warranty is 565 bhp and 700nm. I have no ties with them, but their offer seems very interesting.

Would also ask ETG, there are some valid questions for them, one of course is what they can do without the pulley of course. I’ll take it they get their tunes from Germany so they might have some knowledge there on cars that do extensive German Autobahn or the Nürburgring.

Assuming that when you go on the track you are not racing close distance with others (so even less airflow….), then a way to combat heat in the engine bay is to work on aerodynamics (you can force more air thru the radiators this way), not sure what is available for the XKR, you might want to have a close look at the XKR-S, that car has at least proven to work right on the Nürburgring at full power.

 

The Ziptuning website (frequently asked questions) indicates that the manufacture's warranty remains in effect in Europe if having service work done at Ziptuning and other independant shops, as opposed to the dealer. I assume they state that because a dealer would be able to detect an ECU modification, and use that to void warranty. I believe all warranty work in Canada must be done at a Jaguar dealer, so it would void my warranty immediately.

The website also states that any on-going manufacture's software updates would reset the ECU back to standard programming, and the Ziptuning changes would be lost. I'm not sure customers would even be aware if an ECU update had been done when taken in for scheduled service during the warranty period, and I can see refusing to let them do it would be an issue with warranty coverage.

Ziptuning states that software updates seldom happen when a car is older than 3 years, and while they do offer free re-tuning, I wonder if it's possible that they might negate an important manufacturer's "fix".

I think the reality here is that tuning your ECU will be detectable by the dealer and will void your warranty. However, once the warranty has lapsed it won't be an issue, and the dealer will not care.

Bruce

 

As far as I know a dealer will not check if an ECU is tuned for normal service, so there you would be safe. As the engine is relatively new, one can expect ECU reflashes and then you lose the tune of course, but Ziptuning, ETG and I think almost everyone will provide you with a new version if that is needed.

The good thing is that with young cars they offer the engine warranty (or even drivetrain one, not sure), so it doesn’t even matter if Jaguar would know, and the external insurer they use seems an international one, so worth checking out I would say.