I have read a lot of the post here but many of them seem very outdated. I wanted to update and get more performance from my jag but the article listed parts and companies that no longer are available. I know I have an american version of this sports car but because its over 20 yrs old I can not take off all the smog crap and return it to the car it was supposed to be. I am on a budget so I want to get as much as I can from what I spend. I am also a Harley owner and believe when something breaks down you upgrade. I only have 40k miles on it and its all original. I am not interested in keeping it original I want it fast, sporty and unique. I want to do simple things to start with like exhaust and speed chip. I contacted the company that was listed to be told they stopped making that ECU device. I am hoping to really make this a unique machine with 18 inch wheels and possibly a blower or other speed boosting device. I figure if I can put together a check list I can start with the small stuff and as things go bad upgrade them. If I do a little every year I can reach my goal. This jag reminds me of my 93 Harley, it had California smog crap on it so it couldnt get out of its own way. After 5 years people couldnt believe how fast it was for as heavy it is. Trouble is it stops like a tractor trailer and no way to fix it do to its weight. I know this is a well engineered car, but I also assume it had some power and fuel robbing modifications to appease the USA DOT. This has always been my dream car so I dont want to destroy it or over modify it but I do want to being out the best it can be. Its sad to see all these great cars being parted out and sold for 4k or less. I am hoping to find companies in the USA but if not exclusive. If a part is better in Europe I will accept it. I am open to all suggestions except cutting the body. I want the body to stay as it was originally. If there is a site that doesnt get too technical, I am not a machanic I understand a lot but have little practical experience. I dont need confusing data or percice figures just direction. ie a TKO600 is better than a Richmond but install a 3.31 diff is plain english to me. That said getting into the exact gear ration for each gear is too techical. Yes this will be on the road but it will be country roads with no cops, lots of corners, and no other drivers. So I dont mind if it doesnt meet dot as long as it hauls *** and I dont feel every crack or pebble in the road. Is their a updated source to show what upgrades are available. The one I got dates back to 1998 and not edited or added to since. It would be nice if someone is keeping up with new technology but I understand once its done ..then its done. Few worry about suspension or newer trans after they replaced it.

 

im also new to the jag and if you want to make it unique and fast ditch the V12 and drop in a v8 motor. the race car versions of this in v12 made 550hp which was almost all custom. if you had 20k laying around u could do it. but a v8 and with a 5spd conversion is going to be 10k. Im sure others will chime in later.

 

BUT XJS was born to be a V12 cylinder engine ,all aluminum,overhead cam!

got a little mud on the tires,and the car

 

Sorry one of the reasons this is my dream car is because of v12. Sorry misstypef above, i can remove all smog stuff to bring ip power if i can find ignition control module.

 

You can take a look at this website:

THE JAGUAR V12 ENGINE / AJ6 Engineering

Roger Bywater was an engineer for Jaguar and does a good job of highlighting what can be done to improve the performance of the Jaguar V12 and what is a waste of time.

Cost Effective V12 Upgrades Guide | aj6 engineering

 

The AJ6 Eng stuff is really good. After that, swapping out the GM400 auto for a manual box is easily the best mod to get more rear wheel power. There is a guy on here ICSAmerica who knows all about it.

 

I have a concern about going to a manual transmission because the foot room is limited. I often hit the gas and break at the same time so I worry about adding a cluth to the same area.

 

The XJS manual pedal box (as used in the 6 cylinder cars) is a direct bolt in fit and the brake pedal is a normal manual size. Also various aftermarket pedal boxes fit fine. eg
https://xcessivemanufacturing.com/ja...pedal-kit.html

 

What's your definition of 'hauls ***'? What are you expecting, or what level do you want to reach? Nowadays Grandad's Honda Accord V6 is faster than a lot of performance cars of yesterday.

As you may have gathered, squeezing more power from a V12 isn't easy or cheap. Another 50 horsepower might be fairly easy but, after that, not so much.

Manual trans swaps are very effective, as mentioned. So are conversions to GM's 700R4 four speed automatic.

Removing the emissions stuff alone won't put you into hauling *** territory, not by a long shot

On the bright side, suspension upgrades are easy, effective, and relatively inexpensive.

Cheers
DD

 

Actually, probably the easiest thing to do is sell your car and buy a later 6.0 car and drive it as is. That will give you approx 40 hp over a USA market 5.3 and a 4 speed transmission as a bonus.

 

There is a lot of power in that V12 if that is your goal. But, learn the difference between gross horsepower and net horsepower. Someone will tell you that a Chevy 350 makes more horsepower. It doesn’t. Not when you measure them apples to apples. Your V12 has 262 horsepower DIN
the same year Corvette makes about 210 horsepower DIN. A V12 puts out big block Torque numbers even though it’s only 326 cu in. Additional power is Affordable if you have skills but expensive if you have to buy those skills. When raced against Corvettes of the same era it beat them. But you need to be reasonable. That is a heavy car, over 4600 pounds before stuff is added like fuel and people.
Stock it is geared to go 150 mph and properly tuned it will!!!! If you want to shred tires you’ll need to make changes. Some are simple and affordable others are darn expensive.
Ignition is simple. But the fuel injection is controlled by the ECM.
Don’t be afraid of the fuel injection system. Once someone walks you through it pointing out what things are and what you can and cannot do to it it’s simple.

If you really understand Harley then a V12 is actually a simpler version times 6. 12 cylinders instead of 2
but no push rods or rocker arms.

The stock fuel injection system is extremely reliable. But!!!!!!! Not very flexible. In other words you can’t just chip it.
What you can do is replace it. There are no plug and play replacements so you or someone will have to sort of figure things out.

I was terrified of that process but once someone explain things. It’s not so bad. What does fail on Jaguars are the sensors and the wiring. But again once you know where the sensor is and what it’s job is it’s simple to replace.

The smog stuff can be neatly removed and saved. Don’t throw it away! Timing can be adjusted to European specs.

oh and hoses. They get old and crack. Just replace them by getting a really good quality hose ( no hardware store stuff ) unplug one end and plug in the new replacement then follow it to the other end and repeat. About every 5 years do that and you won’t have problems.