I realize suggestion#1 might have been to by an XKR....but I'm looking for suggestions on ways to increase the performance of my 2003 XK8...without major work or creating problems for the drive train.....does anyone have any thoughts about air intake and performance chips actually being of any value...and if so....what kind of results I ight see....?....thanks for indulging a enthusiastic Jaguar newbie...

 

Hi, trogers... and welcome...

I'm no performance expert... however I always read the same answers... bolt-ons... headers, air intake, muffler and in general exhaust system, chip... and then build up from there...

On my explorer I have a tune, air intake and muffler... since I have not dyno'ed it, I don't know if it has more power... but there is a definite "peppiness" to it after those mods.

I read that the xk8 rear end is more that of a cruisers' not like a corvette, for example, if you wanted more punch at the start-line, you could invest in changing the rear-end...

cheers!

 

thanks....I doh't tihink I want to go that drastic by switching out the rear end...but the other modifications make sense....thanks for the reply...I'm rellay like a sheep going to the slaughter on this stuff.....I don't wnat to destroy the originlity of the car..but I would like a little more zip....you've given me somehting to think about...thanks again...

 

no chips available, and depending on your budget, you could do a few things:

1. adjust the throttle cable (see the FAQ in this subsection) this actually returns the throttle body back to original parameters, mine was lacking the last 20+% of the throttle plate opening.
2. modify the exhaust
3. high-flow catalytic converters (from our sponsor Nameless Performance)
4. twin-screw supercharger (from one of our member's own designs)

there may be a few other suggestions that I can't really think of right now...it is late.

 

How difficult is it to install a supercharger in these car? I know for the explorer you get rid of the upper inteke, need bigger injectors, a computer tune, pulleys belts...

What about just NoS?

 

Nos not a good idea in these cars. you can't retard the timing. I would start with exhaust and go from there. As far as supercharging goes i do remember seeing someone that was successful in doing it. You could start with simply buying an eaton M112 for short money and sticking that in. No injectors needed but if you get super serious about mods they can be limiting.

 

Avos' twin screw kit is only intended for XKRs.

The thread on supercharging the XK8 is here: https://www.jaguarforums.com/forum/x...d-works-49685/

but an an XKR makes so much more sense when you look at the effort and results.

 

isn't there a company which makes some kind of universal turbocharger kit designed to hang off the exhaust, toward the rear of the car? not that I'd want to be the guinea pig for such an experiment, of even do it if it was proven to work, however that might be an option.

 

Pistons are different on supercharged to lower compression.

 

Swapping for an XKR would be your best, and least hassle, ROI.

 

Turbo lag is already there on optimized systems, now imagine turbos on the back of the exhaust, it will take a long time before you build up pressure in the full exhaust, so result will be massive turbo lag.

If swapping your car isn't an option, and performing (the admirable) work fishman has done, you might want to consider a wet NOS system, but I am not an expert on this area.

 

I have been tempted to fit a couple of Rotrex superchargers which are a kind of turbo/supercharger hybrid.

But the OP has said he doesn't want to get into any major work that might cause probs........ so basically there is nothing you can do, the absolute best thing you could do is change the exhaust system from the 'manifolds' back.

Even NOS has probs, quite a few people who have fitted NOS to there XKs have melted pistons, I would call that a major prob!

 

Agree with the exhaust, especially as a good exhaust note gives more sensation of what you already have.

 

Keep in mind the car does weigh 4000 pounds. It would take significant work to get serious acceleration.

 

You probably have a lot of experience with different exhaust configurations. What parts of the exhaust seem to be the most restrictive, or rather make the most power when replaced? The catalytic convertors, the rear exhaust, the central muffler? Or is it more that everything needs replaced in order for any one part to make a significant difference?

 

I believe the company you are after is STS. While it doesn't seem like it makes much sense, it does work fairly well. I know a guy who has that setup on a GTO, of course that engine has a couple more liters to throw around.

On an XK8 I wouldn't head down that road though. You really need to be able to tune the vehicle when you get into radical changes like adding forced induction, and as far as I know there aren't too many tuners out there who tune Jaguars.

Without getting serious into mods you are probably only going to see maybe 15 - 20 HP. In my mind that's not enough to bother fooling around with, it would be tough to even feel the difference, and may cause more issues with the car acting up. I say, be happy with what you have. If you can't be happy with it, get something else that will make you happy.

 

I have had a fair bit I must admit..... The most constricted area are the cats, just by changing them and keeping the original exhaust will give you a different exhaust note and more power.
If you want all out performance go for 200 cell cats and under axel exhaust. If you want something that is not over noisey but also some performance gains then you need 200 cell cats, cross over, 2 silencers in front of the suspension and then 2 resonators at the back, you will get a nice exhaust note and no annoying drone.
Don't expect much change out of $3000 and gains of around 15-20bhp, which to be honest just the sound will make you feel faster, the extra bhp you will hardly notice

 

Hi, I have a 2003 XJR. Can I stick a chip in it, and what would you reccomend thats not going to strain the s/charger. With thanks

 

There is not a chip out that works on these cars,it is all snake oil and BS.

For a simple quick upgrade, swap out the pulleys to either a bigger bottom pulley or smaller top, cheapest bang for the buc and you can actually feel the difference.

Dont do both unless you want to get into cooling upgrades as well and spending mucho $$$

 

There are 3 things which give an engine more HP and TQ, one is air, two is fuel and 3 is cubic inches or as our english friends say cubic centimetres.

There are several ways to increase air and should be done in tandem, unless there is a bottle neck and ALL engines have them, usually it is the valve train or exhaust that is the major restriction.

I have read that on XK8/R's it is the exhaust, so getting more air into the engine will do no good and will usually cost you HP, if the engine cannot handle more air.
The best way to get HP is to do all 3 places at once with a goal in mind, because just putting on a cold air intake will do very little if you cannot get the air out the other end.

Study up on the engine and do NOT throw money at the engine without knowing what the benefits are and what problems it might cause.

If you go cubic inches, you will still have to fix the air problem and you will need bigger injectors and so forth.

Worst thing you can do is spend a lot of money and get very little gain or worse a car which does not perform as good as stock.

I built a 93 vette that could take any stock Z06 in the 1/4, I know many people who spent $5-6k on engines and rear ends and could even come close to my car, this is not bragging, this showing you that if you spend wisely and research you can get a car that performs well and you spend less than someone who just throws money at the car.

Also very important, the rule of thumb is, that if you add 50 hp to the engine you need to beef up the drivetrain.

Good Luck!