LOL yes it would seem so mate!

You've got the power to run a 12.4 if you can get it off the line cleanly.

With a sub 2.0s 60' time it's a 12.4, no doubt. Get some drag radials

 

Well the cost to get it to where it is at the moment is quite substantial , as i'm sure you can imagin as you know some off the trips , plus , plus i had to do and that's without the engine re build
So i think i will sit back for a while and see how the other guys get on , and how they push there cars , as i am sure as Avos has said there seems to be more room for improvement

That said who knows , maybe smaller pulley , water/meth , or nos ??????????????

 

Hmm... was hoping to see it trap at least 118mph with 520+whp... whats your elevation at track level?

Great testing and feedback!!! This data is very hard to come by for TS equipped cars!!!

I hear you there... The newer 5.0L SC jag's can make about 500whp with minimal mods too, so a 5.0L XFR, XKR, can be a cost effective alternative to modding your 4.2 in some ways...

Although the TS still represents higher overall potential, as the blower is good for 600+whp, which a the 5.0L + TVS don't think can do...

 

Thanks for being courageous enough to share these results Davey! Not to depreciate them as 12.8 and 115mph with traction issues is still extremely fast, however I too was expecting much faster considering your car is producing 529rwhp. Assuming your car is capable of a 12.4 at 115mph with a sub 2 second 60 foot, this is still confusing for me as there is an XFR on the forum which has ran 11.9 numerous times at 119mph with 480rwhp. As your car is 400kg lighter and more powerful I was really expecting your car to thrash it. Again, I don't mean to critisise what you have achieved as I'm only seeking an explanation purely for educational purposes as I myself am considering a TS for my STR. Could it be that weather and track conditions were a major factor too?

 

There are a few things.

My XJR weighed in at 1760kg without driver, 1/4 tank, no spare/jack and everything out. So Davey's would have been close to 1950kg on the day.

XFR runs a lower diff ratio than the XJR's 2.87

XJR runs 255's, XFR runs 285's or wider.

XFR has the E-diff, Davey's XJR has a Quaife.

There is more to it than just power.

My XJR trapped 105mph at the same track for what it's worth.

 

I can't comment on the results, as I wasn't there and I have no experience with 1/4 mile results anyhow, other than a lot of factors can influence the end result.

But please note, the average 516 rwhp on the 3 dyno runs where measured on a dynapack dyno, which is different from the more traditional chassis dynos (ie dynojet/mustang etc), as the wheels are taken off and the unit is attached directly to the axle. That means that in these figures you do not have the losses of the wheels!

My best guess for Davey's setup is somehere around the 470-480 rwhp on a dynojet type of chassis dyno.

 

I new there would be more discussion over this , for me i cant spesk to mutch about the finer points , it goes a bit above me , but i can say its very difficult to compare eggs with eggs , as the base lines are always different ??

For me i got what i wanted ...A nice 4 door family saloon that has that extra something ...and i still have a big grin when i drive it , so am i happy YES.

1/4 mile times are an extra , but fun to do with the guys .

I'm sure someone with more know how and enthusiasm would do a lot better , but me and my car drove to the track as is, and no letting down of tyres etc. and just run the 1/4
Will i try something next time , maybe will i go further with the engine ,maybe

I will sit back for a while and see what others do , I'm sure this is just the start of the xjr mod journey

But i say again am i happy YES ,and i know if i'm sitting side by side with another xjr i now the result

One final point ....Thank you Avos for what i have and also Cambo who has know about this project since the very start ( Nuremberg ring )and shared many pm's

David

 

The most important thing It would be interesting to see in future what it could achieve with the mods Cambo suggests such as wider drag radials, emptied boot and low fuel if you decided it was worth the effort. I think coil suspension would also help with the weight transfer on launching. Thanks again for sharing the results and I hope you continue to enjoy the car.

 

Dave, you can compare your fastest run data to my 12.377/111.9:

You were slower by:
60ft: 0.254
330ft 0.439
660ft 0.485
1320ft 0.433

You can see that your problem really is the first 100m/330ft. Your X350s overall gearing ratio for 1st, 2nd and 3rd gears are 11.97, 6.72 , 4.37 vs X308s 10.98, 6.69 and 4.30. This makes more easier traction problem for you at 1st gear depending on the rear tire type and size you use. Right sized DRs would save you .4-.5s ( at least ) . My XJR had way less peak power and about the same weight ( spare wheel set + 25kg extra weight in the boot + 1/4 tank. ). Even I had big DRs, I needed extra weight to compensate poor airfield track. X308s 117K miles driven old suspension gave nice squat at launch. X350 is a bit different, I guess.

 

Am preparing now the TS kit batch for the 4.2 XJR and STR, please let me know if you are in, as it will take a while before the next one.

 

Could I please get some details for the kit through PM? Or do I need to send you an e-mail?

 

I have a bunch of steel KB blower pulleys of various sizes. Have you tried a smaller upper puller or are you maxed boost wise for pump gas and or no belt slippage


Thanks!

 

Anyone got any actual experience of the effects on long-term reliability (or not) of doing this to your jag? I find it hard to believe that you're still gonna get 200k+ miles out of an engine/tranny that is squeezing maybe 620hp out of 4.2 litres.

 

Me too ;-)

When I started playing with my 4.0 engine, I also bought a 4.2 engine and tranny, to have it for just in case. At about 120Kmiles, I had a serious accident, and to repair the car it was easiest to take out the engine. As I have the 4.2 ready, I thought why not swap that one in, but it was not needed, the engine was in perfect shape even with the nicasil liners (I treated it always with ultra-low Sulphur fuel). I also swapped the tranny, which I had put in stronger parts for just in case.

With the 4.2 engine, I was already at around 450-470 rwhp iirc, and not long after at around 500 rwhp, and I have driven about 120Kmiles with that engine. No issues again, to my amazement as well.

Then I started my latest project, the 4.8 ltr engine, and on that one I have already 30Kmiles, where I build up the power in small steps. Am actually now ready for some dyno tests, to see where I am at for the moment, maybe next week (at least nog long anymore).

Of course increasing hp doesn’t increase longevity, by going to the limits of parts, you are also closer to dangerous boundaries. It’s important to react quickly if something doesn’t feel right, and don’t push it further at these moments and fix it 1st (ie on my car for example I had clogged fuel filters, faulty coils, not working 2nd fuel pump).
Also I do not drive on tracks nor long continues power stretches, as there whit the added heat you are at higher risk of breaking something, and there I would say tone the power down a little and put more effort on overall cooling. Good maintenance and care is important as well, so best oils, check plugs regularly, and never go full power when the oil hasn’t reached operating temp (which takes longer then coolant!). Last but not least the very efficient twin-screw setup that generates less heat and consumes less power from the engine does help as well, that alone gave me more confidence to get to higher levels than others achieved with the (h)eaton, but again never thought I could reach the power levels and without issues as well.

Every step up in power always made me very nervous and still am in the increases I am doing now, especially as I have no references (i.e. know anyone else that is at the power levels I am pushing it now again).

There must be a borderline somewhere and can only hope I will not find it ;-)

 

Avos, what were the "stronger parts" that you put in the STR gearbox? I am about to change the torque converter seal, and want to beef up the box in case I go for a TS kit later on.

 

I have the MB gearbox, and there for the TS kit you do not need any strengthening (nor for the 6HP26). If one is going to refurbish it anyhow, then go for the 800/900nm parts (box that is used for the amg's). I just did it as I didn't know how strong it could be, not because I knew where potential weak points could be. So far there have been no gearbox issues with anyone that is using the TS kit, that also counts for the ZF 6HP26 boxes like you have.

If you plan on having 600 rwhp or more, you could go for these (but I guess other parts will fail earlier at these levels):
EXEDY Automatics | 6R80 - 6HP26 Ultimate Performance

Of course if you are going to the track, ie continues high power usage, I would be more careful, but there as said I would tone down the power a bot and focus more on cooling.

 

Hi Andre,

OK you've had me drooling for about 3 years now! Your great post above about reliability just made it worse.
Has there been any more progress on a kit for 2007+ XKRs or have you pretty much labelled X150 as "never gonna happen"?

Thanks,
Neil.

 

Am not actively working on the x150 4.2 kit, I know what to do though, but would need to have a car close to me, and no one has offered that yet or asked me here. The ones that did are just to far away unfortunately.

As long as I have my car and circumstances allow it I will probably continue making kits, but I can't promise I will do this for long as it is a lot of work/administration etc.

 

Avos,


Have you been able to complete the kit for S Type R 4.2?

 

It is ready already for some time, the kit for the 4.2 XJR is the same as for the 4.2 STR.
I just had to wait until the dyno was done for Davey's XJR you see in post nr #294.