I love the sound of a tuned six cylinder and love the tan on black interior color combo in the XJR-6, but I would like to get about 70hp more out of it. After owning a 03 XJ8 and a 99 XJR the XJR-6 seems way to sluggish for it power. Im sure most of that is the 4 speed vs the 5 speed of the x308s but for 322hp its slower than my 03 XJ8 with 290hp. My question is has anyone ported an Eaton M90 from an XJR-6. I know Eatons are well tuned factory and thats why I never ported my 99 XJRs but that car was quick enough with just the basic upgrades.

Any insight on this subject would be appreciated. I would just like to see it run low 14s, nothing to far out there.

 

I have a 1996 XJR6. And after coming from owning a '93 XJ6 for 5 years my R is no slouch! However, my father leased a pre-owned 2000 XJR a couple years back so I know EXACTLY what you mean as you mentioned you used to have a '99 with the 370 horses. It's night and day difference.

The Mina Gallery makes parts strictly for cars like ours, interior/exterior, performance, everything. And they used to carry an upgraded supercharger pulley for the 95-97 XJR6 cars, which automatically added 35hp. It was around $500-600 and I keep kicking myself for not buying it a year ago...I called a few weeks back and they said they stopped carrying it months ago because no one was buying it!! Not Cool.

I think you and I should start a petition to bring that product back specifically designed for our cars. That would bring it pretty darn close to the early V8 XJR performance.

What did you mean by "ported" as you mentioned above?

 

You might wanna do some browsing here for ideas and vendor links, etc. Anything that can be done to an M90, these guys have done it !

http://www.sccoa.com/

As of a couple years ago (when I was a member) there were some XJR owners in the group.

Cheers
DD

 

Euro toys sells that same pulley for the X300 XJR model. That alone though would not do enough. The transmission being a 4 speed vs the X308 five speed is most of the problem. The internals seem to be geared way to long for a car of its power. The five speed from what it seems can achive the same top end but adds that extra gear to shorten the gear lengths keeping the car in a tighter RPM range.

Buy porting I mean widen the supercharger ports and then have the existing parts port matched to receive a higher air flow capacity. If that can be done with a big enough gain then it will be worth it, anything else thats available for the X300 models isnt worth the money in my opinion.

 

No loss on the pulley. I've heard from a couple guys who tried 'em and then removed 'em

The power increased for an intial burst was good but the air charge becomes too hot so quickly that power drops off.

Better intercooling can only help.

DD

 

If you want more acceleration change the diff, I am not sure of your ratio but I am sure a 3.77 would make quite a difference. Just bolt it in & off you go.

 

I went from the 3.27 to a 3.58 on mine and felt a definite improvement. Not an oh-my-god-it's-like-a-different-car change, but it did make a difference.

Also, the timing modification bracket sold by Andy Stoddard is easily worth the $100

Cheers
DD

 

You should try a 3.77 that will really make a difference. I have read about Andy's modified bracket, it seems like a great upgrade. Have you considered having the blower ported. I have had work done by http://www.stiegemeier.com/ they specalize in Eaton blowers. I have seen on the XJR owners forum an adapter plate to increase boost. If you replace the pulley you will see an increase in boost. To cool the charge try water methanol injection it really works.

 

i have a m90 of a 97 xjr for sale if your interested? also have a 01 xjr one too

 

What type of rear end does the X300 have? and where did you get gears for it? I have been trying to find out what type of rear ends both the X300 and X308 have since I purchased my 03 XJ8. If I can get better rear end gears that would be perfect I just need to bring down the top end in the X300 so I have a tighter RPM range but information and performance upgrades for Jags are hard to come buy, besides pulleys, exhaust, and intake.

I have millions of Ford parts because I part out Lincoln Mark VIIs. If the Jags have Ford rear ends that would work great.

 

Thanks for the offer, but I buy my Jags with less than 30,000mi on them and then send the supercharger out to be rebuilt while I replace all gaskets and clean the surrounding parts.

 

Hmmm. I dunno what kind of differential it is.

Earlier Jags had a Dana design (Dana 44, I think, essentially) but I'm not sure about our X300s. I assumed "Dana" but never actually knew for sure.

Anyhow, I bought a complete rebuilt differential so it wasn't a matter of ordering individual parts.

Cheers
DD

 

The earlier jags did have something very close to the dana 44 but things were different once you got into it.

No big deal though I just didnt want to pull the rear end from the jag because once its apart I need some direction to go in to finish it asap. I tear down cars as mentioned and cant have it in the way while I research and run part numbers to figure things out.

I will be buying an X300 XJ6 for a daily driver soon so ill just tear the rear off that one and park it while i figure things out. I dont want to leave a nice XJR-6 outside while I build a rear end.

 

X300's have the salisbury diff which came with or without limited slip. ratio was 3.51:1 if memory serves, I know I wrote it down in my car's diary, I had a new rear end put in about two years ago

 

Thats great! Thank you for the information. If salisbury is the type of rear end thats all I need to know.

But still my original question has anyone ported the M90 supercharger and was it worth it? The rear end will help but I still need more power.

 

This is a reply to a very old post but I would like some xjr6 owners to chime in. I have ported my sc and I have to say that bottom end torq was lost but additional power was put up on top. My sc pulls from start to finish with no sc cut off, but that is not due to the port but to the true cold air intake that i fabricated and installed. I only wish that i installed the intake before the port, I think I would have been alot more happier. the next step would be a larger tb intake and throttle body and or a larger lower pully at 15 od. Any one out there with the same experiences? chime in, let me know how to get that bottom end torq back.