Hi all,

What are the best , most reliable upgrades for a 2001 XJR ? I would guess the supercharger's pullies and performance filter and exaust?

How can you remove the speed limiter?

Thank you!

 

Yes, pulleys are available from a number of vendors; IMHO, it would be utterly foolish to defeat the 155mph limiter. I have driven my R for many hours at triple-digit speeds; the aerodynamics become a serious issue over 140mph, the nose gets very floaty - not a healthy scenario - even absent atmospheric issues like wind gusts, crosswinds, etc.
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1999 XJR

 

Upper, lower pulleys, "cold" air intake, exhaust including higher flowing cats, ECU programming, larger intercoolers, cylinder head porting and supercharger porting. I know one who has a stoker crankshaft and another running nitrous. I did all the mods except stroke the motor and run the bottle on my '99 XJR. No major issues.

I agree with Markus, the car gets squirrelly at 130 + and at 145 it's a beast to control with a floater nose. My car was lowered also. Running a sturdy front spoiler would help.

 

I am interested in info on the stroker crankshaft. I know you can but a 4.2 crank & rods in a 4.0. Please post info mas that is interesting. I would like to go 4.5 or even 4.7

 

Arden makes a 4.5 stroker kit that includes crankshaft, rods, and pistons.

 

Not sure the price of arden makes it an interesting venture.

JGAXKR, there are so many places in the US that can make crankshafts and parts, why don't you try it? I would expect for crankshaft/conrods/pistons between $8000 and $10000 pending on materials/quality used. Might be interested too.

Andre.

 

Hi all!

Apprecaite your help! In fact I'm looking more on " light" upgrades and nothing internal of the engine. So far have only a KN filter..!
How many more HP would bring a set of pullies and boost??

Thank you!

 

for pulley upgrade, an ECU remap is in order - why not wait, and find a stuffed XFR (5.0l engine)... I wonder if the gen3 would go into the XJR......510BHP, nice. That car with limiter removed went 225mph....
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VF1000F

 

People have reported mixed results using different pulleys, seems the stock setup is pretty well optimized. The oiled air filter fouls the MAF on N/A cars but supercharged cars do not have this?
Some of the English tuning shops websites may suggest mods that yield significant improvements.

 

Remove the Screens prior to the Cats, and for more fun hollow out the Cats. :}

 

SC cars have a MAF i do and i´ve cleaned it

 

Here's what I've done with my UK '95 straight 6 supercharged XJR.

Pulley upgrades:
Tried both top and bottom then both together, all they feel they do is move the power down the range so quicker off the mark (more boost). Power gain was around 15bhp for one and 25bhp for both, improved torque at lower revs though. Problem is the XJR style of blower is less efficient at higher revs. Also some slip[page happens with the smaller top pulley, only option was a 'gator' supercharger belt to fully alleviate that.
*Recommendation?: go for the lower pulley upgrade with gator belt, trickier to fit but the better option.

Exhausts:
Mine is de-cat with only two rear straight through rear boxes and oval exits, all in stainless steel from the manifold back, best 500GBP I've spent on the car, results are awesome, more power, torque and sound burbling at lower revs and howl at full chat, lovely.
*Recommendation - de-cat at least, you will notice more power.

Intake:
Cold air intake is a must, the best result I had was replacing one inner headlamp with an intake into a 5lt pre-chamber ahead of the intake, MAF and blower, the chamber stabilises the flow to the MAF and as it pressurises at speed you get better feed so improved throttle response and power.
*Recommendation - cold air intake in place of your standard airbox at least, go for a premium brand filter, not a cheap styling one (won;t keep the harmful dust out of your motor and remember everything that comes into your intake goes through your supercharger rotor blades!)

ECU and Injectors:
Left it alone as it self re-maps for improvements - up to a limit, same for the injectors.
*Recommendation - leave alone unless serious power hikes then go bespoke ECU and injectors.

Fuel Pump:
Often overlooked, check yours is up the job still, I've replaced mine with a newer high-flow model.
*Recommendation - check fuel line/pump pressure and if not up the full flow pressure it will rob you of power, fix or replace for a newer race one.

Intercooler:
Upgraded with a higher flow bespoke one in the same place, marginal improvements moreso at higher revs, worth the money.

NoS:
I'm running NoS on variable feed up to +100BHP, that's the real dandy, hit the NoS and nothing else matters, with the other mods the NoS is the perfect tool, gas in and gas out, the cat really flies and will light the tyres from start (trac off!) and on 1-2 and 2-3 gear shifts.
*Recommendations: fit NoS and start with +50bhp, if you're happy with that stick with it.

Fuel:
Again often overlooked, use premium grade if available (improved combustion and flow, less vapour problems under heat robbing you of power) and avoid supermarket buys, they mix to fit fuel in and they don't buy from the leading brands front-line processing as many people say they do.
*Recommendation: buy the higher octane branded fuels.

Engine Oil:
Use the right oil, will make a difference with engine lag and friction reduction, fully synth is not always best, my six cylinder Jags (including my XJR) seem to prefer semi-synth, running smoother and burning none between changes.

Hope this sharing helps!

 

Good reading, thanks Steve!

The V8 XJR has two fuel pumps, replacing them is probably not needed for those upgrades. I think the injector might be the first bottleneck.

I'm not sure if a cold air intake is needed either, not for cold air anyway... I have the stock intake in place, and took a drive with an OBD2 scanner connected, and Intake Air Temperature stays at ambient temperature level as long as the car is moving, and won't start rising unless you stop for a few minutes. A cold air intake can of course help the air flow, as it may take some bends off the piping.

I wonder how much an E85 conversion would do in terms of cooling the intake charge..?

 

Probably correct on the V8 fuelling there but I do think the injectors are up to the job unless you're going big hikes. Air intake in placve of the front lamp (one or more) is beneficial for air-flow more than air temp, and once the road speed is up the the increase in air pressure within the intake improves things as I originally mentioned.

Cheers,
Steve

 

Steve I agree on the semi synth oil. Avos has proved the ecu/pumps and injectors are up to the job past 600bhp so I'm well out on a re-map, although it would be beneficial once the car is modded.

What are the dimensions/cost of your i.c. rad? Have you fitted the M112?
Also how does the 6-pot run on V-Power, my mate recon's it's a big improvement.