Is it possible to get 500bhp out of the 4.2 litre XKR V8?

[MPowerMark]

Hello all, not long to go now before the Porsche goes to a new home and i will be in the market for an XKR. I'm probably going to be looking at something on a 08 reg and a coupe.
My question is this, with the new 5.0 litre engine that is installed in the facelifted XKR producing 500bhp i was wondering could that figure be matched by the 4.2 litre engine that will be in the car i plan on getting? I've read something about changing the supercharger pulley (or something in that nature) to achieve some extra BHP but also a good remap and sports exhaust? Possibly all done for less than £2k? Or am i being alittle too optimistic to think an extra 80 horses could be achieved for such little money?

[NormanD]

MPowerMark said:

Hello all, not long to go now before the Porsche goes to a new home and i will be in the market for an XKR. I'm probably going to be looking at something on a 08 reg and a coupe.
My question is this, with the new 5.0 litre engine that is installed in the facelifted XKR producing 500bhp i was wondering could that figure be matched by the 4.2 litre engine that will be in the car i plan on getting? I've read something about changing the supercharger pulley (or something in that nature) to achieve some extra BHP but also a good remap and sports exhaust? Possibly all done for less than £2k? Or am i being alittle too optimistic to think an extra 80 horses could be achieved for such little money?

You won't get 500 horses with what you have mentioned but you can with fitting a different Supercharger

You can then get over 500 easilly for road use and I've had 600/650 for track days

In the UK contact TLJaguar on 0118-976-2899 post code RG40 4TS

There was a six page write up on my car in last May's Jaguar World and the modes they have done

[designXKR]

You could also talk to Kevin at DesignXKR in Andover. He has done a lot of work on upgrading the XK.

01264 333523
or [e-mail]

[P700DEE]

Pulley upgrades, really only shift the power band a bit, Jaguar did a fairly god job with the charger as standard. For any long term running the heat effect of the Eaton charger is too much and saps power. The best solution is a twin screw but you need a lot more than £2k. Fast easy reliable power increase at the touch of a button, NOS, even helps cool the engine.

[avos]

Am with P700DEE, it is very hard (read expensive) to come in the direction of 500 BHP with a 4.2 and stock supercharger (and especially sustained high power output, not just a short power run on the dyno…), 2000 will make a change but not sustained 500 bhp.

There are many commercial companies to call besides the ones mentioned here (i.e. paragon, elite performance, paramount-performance, racing green, eurotek, eurtoys etc etc), and I am sure they are happy to talk you thru what they can offer you.

[jgaxkr]

Norman I am glad to see you are now up to 650 bhp,I knew it was only a matter of time. What have you done to increase your horsepower this time? How much boost are you running to get that? Have you updated your intake setup?

[NormanD]

jgaxkr said:

Norman I am glad to see you are now up to 650 bhp,I knew it was only a matter of time.
What have you done to increase your horsepower this time? How much boost are you running to get that? Have you updated your intake setup?

Here is a picture of the indution, what you can't see is that I have the later MAF unit and a little black box to fool the ECU

As I said for track use, although I have used it on the road, is to speed up the supercharger which with the KB and the corrct tools just a 5 min job
Can't remember the boost I get then but have also had a be-spoke re-map

[Marquis Rex]

NormanD said:

Here is a picture of the indution, what you can't see is that I have the later MAF unit and a little black box to fool the ECU

As I said for track use, although I have used it on the road, is to speed up the supercharger which with the KB and the corrct tools just a 5 min job
Can't remember the boost I get then but have also had a be-spoke re-map

You seemed to have kept the AJ26 throttle pot- is there a reason for that? Is your engine based upon an Aj26 base or did you retro fit the earlier throttle?

[NormanD]

Marquis Rex said:

You seemed to have kept the AJ26 throttle pot- is there a reason for that?
Is your engine based upon an Aj26 base or did you retro fit the earlier throttle?

My car is a '99 4Lt

I have since fitted a 4.2Lt but had to keep the original throttle or the ECU wouldn't Talk to it
If one changed the throttle and engine ECU then that wouldn't then Talk to the gearbox or the intruments

[jgaxkr]

I have a 2000 XKR that uses the throttle body from a later 4.2 engine with not problems at all.

[NormanD]

jgaxkr said:

I have a 2000 XKR that uses the throttle body from a later 4.2 engine with not problems at all.

That's interesting
Two questions, one, why did you change to the 4.2 thottle body
and did you have to do any other mods to make it work

I take it then you have the AJ27 engine, mine is the AJ26

Edited by NormanD on Friday 1st April 09:31

[Marquis Rex]

NormanD said:

Here is a picture of the indution, what you can't see is that I have the later MAF unit and a little black box to fool the ECU

As I said for track use, although I have used it on the road, is to speed up the supercharger which with the KB and the corrct tools just a 5 min job
Can't remember the boost I get then but have also had a be-spoke re-map

The later AJ34 airbox has a solenoid operated valve that opens on the dirty side to lower the manifold depression or loss.

The AJ26 and AJ27 had a manifold depression or loss of about 115 mbar at peak power at an overall engine airflow of 1100 kg/hr. The AJ33 has a manifold depression of 130-140 mbar at peak power, with the flap opening. This is at an overall engine airflow of 1300kg/hr. If the flap wasn't there (like on the AJ27)it would cause an inlet manifold depression of about 7-10 mbar higher. So are you using the earlier airbox or later type and if the later is the solenoid operated flap hooked up?

Edited by Marquis Rex on Sunday 3rd April 10:52

[NormanD]

Marquis Rex said:

NormanD said:

Here is a picture of the indution, what you can't see is that I have the later MAF unit and a little black box to fool the ECU

As I said for track use, although I have used it on the road, is to speed up the supercharger which with the KB and the corrct tools just a 5 min job
Can't remember the boost I get then but have also had a be-spoke re-map

The later AJ34 airbox has a solenoid operated valve that opens on the dirty side to lower the manifold depression or loss.

The AJ26 and AJ27 had a manifold depression or loss of about 115 mbar at peak power at an overall engine airflow of 1100 kg/hr. The AJ33 has a manifold depression of 130-140 mbar at peak power, with the flap opening. This is at an overall engine airflow of 1300kg/hr. If the flap wasn't there (like on the AJ27)it would cause an inlet manifold depression of about 7-10 mbar. So are you using the earlier airbox or later type and if the later is the solenoid operated flap hooked up?

Yes I have the later type with the solenoid operated flap hooked up
I also have the later MAF unit so I don't get the reduced air flow from the early unit
As you see I have a much better induction tube from the MAF to the TB
Also a K&N filter

[Marquis Rex]

NormanD said:

Yes I have the later type with the solenoid operated flap hooked up
I also have the later MAF unit so I don't get the reduced air flow from the early unit
As you see I have a much better induction tube from the MAF to the TB
Also a K&N filter

Did you measure your new manifold depression?

[NormanD]

Marquis Rex said:

NormanD said:

Yes I have the later type with the solenoid operated flap hooked up
I also have the later MAF unit so I don't get the reduced air flow from the early unit
As you see I have a much better induction tube from the MAF to the TB
Also a K&N filter

Did you measure your new manifold depression?

No I didn't as I was also fitting a much larger KennyBell supercharger on as well

[jgaxkr]

What is the simplest way to measure manifold depression? I have a vac/boost gauge will that assist me? I would like to see what my car has.

[Marquis Rex]

jgaxkr said:

What is the simplest way to measure manifold depression? I have a vac/boost gauge will that assist me? I would like to see what my car has.

Yes, that's how to measure it, but you must make sure you've able to do it somewhere where you're able to attain WOT/FULL Load and preferably peak power. JMost of the datum figures I have are taken before the throttle body somewhere- at a tapping- or you could do pre and post throttle. The Jag Supercharged already has a little vacuum line post in the plenum where it says "V8"- so a T could be taken off (although this is post throttle). Pre throttle is more useful. The lowest numbers I've seen are on speed density cars like the M3 CSL and the new Dodge Hemi where there is no necking down for the MAF sensor.
I was wondering if it would be possible to convert the Jag SC to speed density- probably not because it's boosted.

[jgaxkr]

I have a 3.5" tube for my intake including the air meter. It runs thru the inner fender to a cone filter. Here is a photo. Where do you suggest I take the other reading?

[Marquis Rex]

jgaxkr said:

I have a 3.5" tube for my intake including the air meter. It runs thru the inner fender to a cone filter. Here is a photo. Where do you suggest I take the other reading?

Its tough on the XJR/XKR. Normally I would say it informative to have a pressure tapping post throttle but definately before the super charger. However, because of the layout, it's difficult, due to the way the duct curves round on itself pre and post throttle. It's also not ideal to take a tapping on a bend as readings will be tainted due to flow seperation.
In your case I'd take a reading on the black (rubber/sillicone?) duct before the junction going into the throttle. I'm compliment this with a tapping POST supercharger so you know how much boost you're getting as well as the losses in the intake tubing

[NST]

jgaxkr said:

I have a 3.5" tube for my intake including the air meter. It runs thru the inner fender to a cone filter. Here is a photo. Where do you suggest I take the other reading?

Damn that looks clean!

What mods have you done to the car?

NST