getting destroyed off the line in a race with an Audi earlier today has left me wanting some more pickup out of my XJS. I was just wondering if anyone had recommendations for me that wouldn't be too pricey. I have been looking to upgrade the exhaust system to be a little louder, but now im also taking preformance into play.

 

What year and engine ?

Cheers
DD

 

its a 1992 v12 convertible, sorry about that.

 

take off the rear resonators, they're really restrictive. also, there are some air intake kits that are not TOO expensive, and give the car a nice growl (or just cut / modify the existing ones).

both of those things will give you a little better kick down, and certainly better sound.

a major issue wih the xjs off the line is weight, so, that's a tough bridge to cross, yanno?

-best of luck.

 

Check your diff. If its a 2:88 it will always be a turd. Get a 3:54 at least. On top of the formentioned.

or Put in an LT-1 like I did.

 

@lass .. imo, i don't like the 8's in the car, even if they do get more power.

however, good call on the diff, i forget how to check that though.

 

Nitrious Oxide will put a pep in your step.

 

Not just an 8 also a six speed manual.

Anyway, jack up the rear. MArk the driveshaft and mark rear tire on the side with chalk. Rotate the DS until you get one rev of the tire. Almost 3 revs of the shaft and at least one tire rot is probably a 2:88/1

 

Its true the the 2.88 diff is a major limiting factor in off-the-line acceleration.

I was able to improve performance of my XJS with:

2500 rpm stall speed converter
Shift kit
Modified kickdown circuit
A/C compressor cut out
AJ6 Engineering Superenhanced ECU
Low restriction exhaust
Low restriction air intakes

It still was not a rocketship off the line, but it was better....and the ECU really helped mid-range torque. Acceleration in the, oh, 45-90 mph range was quite a bit better.

With just 3 speeds and a 2.88 diff it is important that the trans doesn't shift too soon...as they often do....so check that out.

Cheers
DD

 

yeah, totally forgot about the 6-speed, my bad. Assuming that the car does have the 2.88:1 rear diff, are there any terribly big issues with swapping that out? (minus the obvious labor involved).

 

I've been looking at the ecus... a little expensive, but very nice.

also, how does one cut out the A/C compressor? i've wanted to do that, as i don't ever use the a/c in any car, but haven't figured out how as the belt runs right across it.

thanks!

 

If you're NEVER gonna use it just unplug the connector at the compressor clutch. The pulley will then just free-wheel. No drag from the compressor.

Your defroster/defogger won't work as well and it really isn't good for a compressor to never be used, but you wouldn't be the first.

On mine I used the enrichment switch on the throttle turntable to activate the kickdown and then used to kickdown switch as a full throttle compressor cut-out. Pretty easy....just some wiring and a couple of relays.

If you really want to do it I'll post the details. I'm not 100% certain if a '92 has an enrichment switch, though

Cheers
DD

 

Not that the XJS gets good gas mileage as is, but I'm pretty sure that if you go to a 3:54, the mileage gets much worse then what it is.

 

*grins* aye, that it would. i wonder if there is any type of compromise... i doubt it without having a 6 speed front that you could just make sure to shift at low rpms. either way it's not like the car was designed for gas millage, so...

 

Of course, since it comes with a 2:88 stock and a V12 that puts out 300hp, I suppose it wasn't really built to go fast either...lol!
Don't get me wrong though, I love my 84!

 

yeah... wish the v12 put out a little more power, but.. I'd rather have the looks then go buy a camero just like every kid these days. (no offense to those that own classic cameros, I'm referring to the "daddy bought this for me" kids that know nothing about cars....ran into one of them the other night)

 

I just bought my 88 xjs - good info on this thread...thanks guys!

 

Just a suggestion/question, did you try throwing it down into 1st, keeping the break down while you rev up the RPM's and then launching it?

 

I saw this article on a 600hp XJS. A guy in NY put two superchargers on a V12. I would imagine having a low restriction exhaust and the supercharger whine would make for some interesting noises. No doubt would surprise the odd Camaro or two.

Mike

http://www.jcna.com/library/news/2002/jcna0079.html