Since it is possible that any given engine could have a defect that might appear during the warranty period then I also recognize that as a concern. I plan to trade the car before my warranty expires to avoid dealing with all such problems. But I'm a lot more concerned about the infotainment display and dozens of computers and electic motors crashing then I am the engine developing a problem.

I've had 100% reliability with two forced induction engines that I increased boost on 6-8 psi and then pushed relentlessly for years under gruelling track use. Power increased by ~140 hp on a 2L, and ~140 hp on a 3L. I was successful because I carefully researched the causes of engine failure, and how to avoid them. Detonation and heat are the key issues, and the focus of this thread. Increasing boost 1.5 psi on the 5L S/C Jag is very little, as is adding 65 horsepower as BigCat09 has demonstrated with pulley and ECU upgrades.

ECU flashes are already used to make more power by several automobile manufacturers including Jaguar, and are available from after-market suppliers for just about every performance car. They've got this technique figured out, but we as consumers should still do our homework to satisfy ourselves for our uses, and know their requirements. ECU flashes require minimum 91 high octane gas to avoid detonation...no cheaping out with 87 or 89 like some who lease apparently have been known to do. That's how you avoid detonation with an extra ~40 whp with ECU flash, or 65 with ECU flash and pulley.

Be aware that some have found the increased power to feel less than stunning. Around town doesn't even tax our stock power levels, so extra power could easily go largely unnoticed. But if you do use all the power you've got on the street, strip, or race track...and would like more...then this is the way to get it. And you should definitely make that decision with the understanding that in the unlikely event of an engine problem developing that its repair might not be covered by warranty if your dealer is aware of your modifications. And that would likely apply to suspension modifications as well.

Bruce

 

i would love to retain the conservative stock ECU map for the peace of mind,, given that,, which upper pulley should i go with for 4.2 XKR?
if ECU is mandatory,, who can help remotely?

 

If you are running w/o water/meth injection 1.5lb pulley is better. 3lb pulley gives more power, but it also gives higher IAT2 temps, which leads to ignition retard and power loss.

 

In fact there's a torque/h.p. limiters in an ECU. It's possible to reflash a XKR to XKR-S, which will gvie you an additional 40hp, also it is possible to reflash an AWD X351 from 340hp to 380hp.
But i still can't find a way to remove a torque limiters for AJ33/AJ34/AJ133 engines, even with a firmware downloaded from an ECM and disassembler. There's a lot of code, indeed.
I'm not a big fan of remapping, since a stock maps are pretty good and failsafe and IMHO all we need is to remove a limiters.

 

Okay boys and girls; lets not forget appendix A: Traction. Stiffer rear springs and wider/better rubber should HIGHLY be considered if you start adding power to a 500+hp car. A Tune a pulley nets 600bhp according to reviews and propaganda - my non tuned car will be faster than a tuned car without suspension/tires simply with coilovers and PS2 295's

 

It will be faster from a stand-still start. But when it comes to acceleration from 100 to 250+ kph it's a different story.

 

how to reflash to XKR-S?

 

You should use a SDD to do that, but it requires some "expert" skills to do all the things right.
I don't think it's a good idea to write a how-to in a public access, since some operator's mistakes may lead to an expensive failures.

 

no OBD flashes/remaps available for these cars?

 

I don't know. I prefer to use manufacturer-tested firmwares.
Also, flashing via OBD-II may lead to mistery fail-safe modes, which will be caused by improper calculated CRC.

 

This is an awful car for that kind of driving. If that's what you're going for then get something that you can put a giant turbo on.

Again though - and I promise I am not trying to be argumentative - but if that is the goal then downforce should be of a very high consideration as should suspension. Power is for bragging rights. In order to use power, there are many other factors that equally need to be addressed.

I once bet money on lap times in a 190bhp car vs a claimed 1000whp car. The spec miata(gutted and purpose built) got way faster lap times than the TT350Z with no low/mid range on 24" wheels and factory brakes/suspension. This is extreme although a very true story.

 

Not that awful. Our cars are brilliant, we can drive them calm and have a good time or we can put a pedal to the metal and have a tons of fun.
Sure, a suspension and downforce would be a huge improvement for handling on a high speeds, but, then, it comes to dirver.
Once i was able to beat a 2011 XKR and 2014 Panamera Turbo on a track, while i was driving mine 2004 XJR (but it took a lot of efforts to stay behind a Mini Cooper). Well, after a 5 Chevy Caprices, i've used to own, mine XKR and XJR have AWESOME handling.

 

You've got that backwards. Stiffen front springs to tame the rear. Here's a comprehensive list of things that can reduce oversteer on a car with the propensity to break the tires loose under power and cornering loads.

http://www.tirerack.com/tires/tirete....jsp?techid=58