This thread highlights just how little info is out there about these cars even to Jag owners. I still have no luck finding an 05 XKR shop manual even on CDrom.
There seems a presumption that the XK8 motor and transmission are significantly weaker than the XKR. Is that really the case? I would suspect the motors are identical with the possible exception of cam profile and maybe compression - which either could have been lowered via pistons or head chambers - if it was at all.
Do they use a different transmission? Anyone here know the compression ratio difference between them?
Isn't an XKR drivetrain basically an XK8 drivetrain with a blower added to the motor with corresponding computer software in the ECU?

 

Transmissions, cams, pistons, and suspension are different. Heads are different as well, as the "R" does not have the variable cam timing. I dont know of any manufacturer that has ever made a forced aspirated motor with the same internals as a N/A offering. It wouldnt last and they could not warranty it.

 

The BMW 3.0 in the Z4 and the new JTS engines of Alfa, both have variable valve timing and all of the gizmos currently used in modern engines. Probably even more so than the Jag. Both of them have off the shelf compressor kits available. Sold in relatively large numbers across Europe at least. Is it wise? Agree, probably not. Warranty is out for sure. Will the engine be less reliable? Probably. I do seem to remember however that some of the compressor conversions has a two year warranty if mounted by a proper workshop.

I just don't understand what makes the Jag so special, that it cannot be modified in any way. Just doesn't makes sense to me at least.

 

@Jagnor
This is what I posted some time ago to just give a rough idea what the work could be if you would put the R supercharger on a 8 engine. This might be the cheapest road as you can buy all the components relatively cheap, but lots of things need to be investigated/tried:
https://www.jaguarforums.com/forum/s...ad.php?t=29136

Good luck.

@dfwx
All info (workshop manual amongst others) which is also available to jaguar dealers, is to be found on www.jaguartechinfo.com. Just get a day subscription, make sure you have a day of, and download whatever is possible to download.
The last workshop manual in CD form was version 21, and included all info until the 2004 models. There isn't any difference to your 2005 form a 2004, you can still find these on ebay, just check the version.

 

Personally I have no plans on modifying my Jag. But I have mounted Haltech e11v2 on my Maser alone in my garage, and I've done a lot of work on my prior Lambo Espada V12. I'm just very interested in the technical side of things. So if someone says you cannot do this or cannot do that, I'm just interested in why.

your XKR sounds to be the business! Someone probably told you that wasn't possible or feasible too 600 hp? That's a lot!! How has it hold up?

 

That's my weak spot, just mention it can't be done is enough to trigger me ;-). Never thought I could get this much with relatively small mods, but then again the R engine was as such already a good base (except for the Eaton). Not sure how much engine hp it has, i can only measure rwhp, which is about 500 in max trim. I normally drive in 430-450 rwhp setup, and so far everything is holding, but then again I take good care of the drive train, and do not race the car (on a track that is).

The message was sort of a heads up, and for Norway it could be interesting to do considering the difference in price, heck I can make a special TS setup for that amount of money for an 8.

Now if you would do away with the standard electronics, then you will be able to get much more hp from an 8 even without supercharging it. This is what rocketsports had done, but also Paragon in the UK is working on a NA engine, not sure what he gets out in performance though:
http://www.paragondesignuk.com/xkproject.htm

 

For the record, I never said that putting a supercharger on an "8" cant be done, I just stated that it would not be worth the cost. I also am driven by the "you cant do it factor". I was told I coulnt get 500 hp on my 300zx TT on pump gas but I am doing that.

 

The XKR and XK8 do share the same transmission for some years. For my O5, the same transmission is used in XK8s and XJs of certain model years.

A REAL challenge with these cars is the extreme lack of info - even basic is difficult to find. For example, what is the compression ratio of my XKR (05)? I would be surprised if they used different differentials, axles, drive shafts etc due to costs of different components for the limited production number. What is the compression ratio for the same vintage XK8? It is very difficult to find such info.

 

I surely understand that according to the US XKR and XK8 price difference. But in Norway, where there is a 20 000 dollar difference between the two cars, I think you can tune it cheaper. Perhaps just 50%. It won\t be easy though.

Cheers, Jarle

 

These specifications are listed in the owner's manual--start here then navigate to your model and year:

http://www.ownerinfo.jaguar.com/extf...prod/index.jsp

2005 XKR - 9.1:1
2005 XK8 - 11.0:1

TTYL
David

 

I came back to this thread because I had found the CR ratios. There's not much to be done in boosting a motor already at 11-1 given premium gas is 93 octane. Water injection isn't going to get around that high of compression.

The ultimate motor project (for my XJS with a 454) was an aluminum donovan shortblock assembly I came across. Typically in the 650 to 700 CID application, it had been destroked to "only" 492 CID by making it very over square - big bore/short stroke - to maximize redline. In it's NA form it made just over 900 horsepower at a whooping 8200 rpm (the internals very built up) - but it also has 15-1 compression to do it. In supercharged form, at lower rpms, it's bigger displacement supercharged brothers were holding together at 2500 horsepower. So the bottom end could take anything I threw at it.

I had the compression reduced to 6-1 via different head chamber sizes and dished pistons - and had the pistons and head chambers ceramic coated. The amount of boost and - if wanted - NOS that could be pumped into that monster would have been off the charts. (A wild project as it was to have a twin screw supercharger blowing through an intercooler to provide some full time boost and then twin turbos with their intercoolers and wastegates to run the boost through the roof if desired - with cutoffs allowing using or not using the turbos in a twin exhaust systems and a 106 octane mini tank for when it was for max effort. It was a project abandoned when I decided my Covette Yellow XJS Coupe too much looked like a hotrod.)

Because of the Xk8's 11-1 CR, I retract my view that an XK8 could ever match an XKR in mod build-ups without redoing the shortblock internals - and then no $$ is saved at all. Since they do use the same transmission etc, NOS could do so as I think both have the same "breaking point", but that's something entirely different and generally not a relevant measure whatsoever. I suspect NOS is a very bad option for a current Jaguar motors.

 

They dont use the same transmissions either.

 

I had some bad numbers. You're right.

 

Allthough I agree that you probably wont get XKR numbers safely, I still don't think the compression of 11-1 will make it impossible to run modest boost. The Alfa JTS engine mentioned earlier, have a wopping 11.3 -1 and they still mount a supercharger on it. With no changes internally.

Would be an interesting project, if someone had the money and time

To busy with my Maserati myself.

 

The 4.2 engined ones do - the ZF 6HP26.