I have been asked a number of times about the modifications that I have made to my 2005 XJR so I will discuss them here.Smaller pulley along with upgraded rotors and gearing.

Ported SC

Upgraded cooling system:

In line additional SC radiator

Upgraded Bosch SC Pump

Twin 6” fans

Water/meth injection system

200 cel cats

X-pipe in place of center muffler

Quaife LSD

Range Rover inlet pipe

Stage I cold air intake.

 

I purchased a used SC and sent it off to be modified by a company that is now defunct. The pic is of the SC I purchased and you can see the ablative rotor coating coming off.

On the installed SC you can just see a small amount of "porting" they did at the point of the "V" inlet at the top.



I had the smaller pulley put on the snout where machining was required.
A later set of rotors along with slightly different gearing was installed.
Some porting was done.

If I were to do this again I would ONLY do the smaller pulley as everything else was probably a waste of money.

Many say the smallest pulley over revs the SC and produces too much heat. I will address the heat issue later.

The smallest pulley gives great mid range punch and I rarely go to the red line anyway.

When the SC was off I could see a lot of soft carbon in the elbow below the TB and in the charge coolers which were basically ineffective as a result.

 

On the upgraded cooling system I added an upgraded Bosch SC pump along with an additional in line SC radiator with two 6 inch fans in front.

Part of the cooling also comes from the water/meth injection system. More on that later.

The fans are thermostatically controlled and when they are running, along with the main fan, the volume of air going thru the engine compartment is quite considerable.

"Blockage" from all of this at cruising speed seems irrelevant as I never over heat.

 

The main reason I added this was to help keep the elbow thru the charge coolers clean. As my crud build up was probably substantial starting about 60k miles in my estimation.

I sacrificed the cabin filter in order to place the pump and water/meth container which is on the small side.

You can see the oil catch can in one of the pics and it does catch quite a bit of "fluid".

 

The 200 cel cats were purchased from Paramount in the UK and are bolt on not welded in place.

Had some trouble with the "mini cats" where the O2 sensors were installed.

On hard acceleration I had clouds of smoke behind me.

When removing the "mini cats" no issues at all and no cel warning.

I also did not notice any appreciable extra exhaust noise as a result of these 200 cel cats.

With the X-pipe replacing the middle resonator I do notice more of a growl when accelerating hard but no annoying cruising drone.

 

Quaife LSD.

At the time I purchased this they were hard to find as apparently back then Quaife sold off their stock.

Now it seems they have it available according to a recent post in this forum.

I bought a used diff and intalled this LSD myself along with new bearings. Quite a lengthy process.

It is by far and away the best modification that I have made.

Take offs are startingly quicker and neck jerking on a good surface and pulling out into traffic is predictable and safer!

 

A number of members have stated that the RR inlet pipe has a better flow than the original XJR one.

When I measured it and compared there were significant differences where the RR is wider inplaces.

Some aluminum mods were required to fit this.

 

Cold air intake.

This I did myself for around $30.

 

All other mods I have made have been cosmetic and electrical.

Raised boot spoiler.

Led lights and stronger low and high beam bulbs.

Complete Vanden Plas set of seats with pin striping and trays .

Audiovox screens in head rests with rear seat console media contols and wireless headsets for the passengers I never carry.

Projector door puddle lights that project a leaper.

VACM and Bluetooth modules added.

Rear reversing camera.

Android tablet connection to head unit.

 

Hi John,
I re-read with interest this thread following your advices here under:
https://www.jaguarforums.com/forum/x...1/#post2294773

Could you please comment on the carbon build-up?
Could there be means to reduce it to extend the nominal cooling efficiency over time?

 

I had forgotten about this thread!

Ok so when I took off my supercharger to have it modified I was quite surprised at just how bad the soft carbon build up was and this was at about 100k miles.

I surmised that it must have been bad starting at around 40-50k miles.

So I have installed two "products" to help keep things clean or at least cleaner. The simplest was the oil catch can on the high load breather side and it does catch oil preventing it from
being reingested in the inlet tract.

Te second, more difficult and more expensive, was to install a water/meth system.

The water/meth system helps keep the inlet tract clean as it "washes" over components in the inlet tract. It also has a cooling effect under hard acceleration and prevents ignition retardation due to pre-ignition.

It also allows running on lower grade petrol without knocking/pre-ignition.

This is all on the 4.2 SC cars. The 5.0 cars have much better oil control.

I hope that answers your question.

 

Looking back at the blower pictures, it looks like they ported quite a bit of the V. Look at the two casting circles inside the V, the ported blower goes into each of the circles. Any chance you had a before/after dyno when doing the blower mods? I'm debating sending the blower off to Stiegemeier for rebuild/porting. Stiegemeier Porting Service ? Jaguar

Have you altered the engine software? I wish HP tuners was available for this car.

 

I do not have before and after dynos just claims from the guy who did the porting. He was a well known person who sold out to another company. They did a lot of work not just the porting and gave me estimated gains for each modification.
Those mods were: porting, upgraded rotors, upgraded gear set,and a smaller pulley which required snout grinding.

I did notice that after those mods the car's mid range acceleration was noticeably better and in the beginning I was afraid to do too much pedal to the metal as I would be well over 100 mph so quickly it came as a surprise.

I have not altered the engine software.

 

 

Yes, thank you.

 

Hey great post. I just popped in and took a look. A majority of gains with the twin helix SC's porting wise is at the inlet side. This generation gains a lot less than the previous one. I've had a lot of experience porting these over the years for various different vehicles. Any restriction removed on the inlet side is a big deal as these are air movers not compressors. You can however ruin a blower with a poor port especially around the V area Larger MAF, TB, Intake tube, inlet porting are the best mods. Not sure where the restrictions lay on these cars but we seem to be limited by MAF and TB sizes regardless. My little v6 with an m90 sc had an 85mm TB, 90mm MAF and 3.5" intake tube. It always saddens me that we don't have great support for these cars.

 

i'd like to hear more about the Quaife LSD. I just purchased a XJR and plan to do the smaller pulley and the LSD seems like the other best addition. I found their website, but don't see one for our platform. Does anyone know if these are sold here in the USA? Also, i'm fairly mechanically inclined and wonder if I can handle this add on.

Quaife site

 

I had to buy from the UK when I found mine as at that time Quaife sold of their stock of that type. My understanding is that they are now available according to another post somewhere.

Installing it was my first time doing it. I watched lots of Youtube videos and bought the tools necessary and followed the adjustment procedures. I did buy a used diff to do it.

It makes one heck of a difference!

Look thru this thread: https://www.jaguarforums.com/forum/x...05-xjr-177242/

Also Cambo wrote a very useful thread on differentials.

 

QDF3W37 is the specific Quaife that I used.

https://www.motorsport-tools.com/qua...ntial-kit.html