Tuning the X300/308

[Bisonhead]

Hi all, I am going to be picking up my first big cat next Tuesday. It is a XJ8 4.0 (x308) in black with the Celtic alloys...I cant wait!

I was wondering if there were any tuning options or 'de-riguer' items that can be fitted to these models. Im not looking to add power and wings etc. just subtle mods to allow the engine to breath a bit more easily and be more vocal when the situation arises.

I have had a good trawl on the internet today and cant seem to come up with anything other than Arden and BlueFlame or whatever it is.

Any help would be greatly appreciated!

[NormanD]

Have a look under XK8/Rs

There are many options, most can be done on the XJ8/Rs

[Jaguar steve]

I'd suggest you'd be much better putting whatever time and money you're prepared to spend on making sure the car is in as good a standard condition as possible before you even consider tuning it. If it were mine I'd put a few hundred towards a full fluid change including the gearbox and diff, have the third gen timing chain tensioners fitted and have a 4 wheel geometry alignment check and reset done.

It'll make a difference to the car's drivability if the breather system is clear, the throttle body and airflow meter are spotlessly clean and all the usual things like tyre quality, condition and pressure are attended too. Running a diagnostic scan to check everything is set up as it should be and investigating and clearing any stored fault codes is also worthwhile spending money on.

XJ's are hard on brake and suspension components so any failings or weaknesses here will need to be looked at as well. I'd also give thought to having a thorough rustproofing done.

Car detailing obsessives say quite rightly you can't polish a turd - I have the same view about tuning or sticking after market bits on, and that is there's absolutely no point in doing so if the car itself is not performing as well as it possibly can in standard factory specification first of all.

[Bisonhead]

Jaguar steve said:

I'd suggest you'd be much better putting whatever time and money you're prepared to spend on making sure the car is in as good a standard condition as possible before you even consider tuning it. If it were mine I'd put a few hundred towards a full fluid change including the gearbox and diff, have the third gen timing chain tensioners fitted and have a 4 wheel geometry alignment check and reset done.

It'll make a difference to the car's drivability if the breather system is clear, the throttle body and airflow meter are spotlessly clean and all the usual things like tyre quality, condition and pressure are attended too. Running a diagnostic scan to check everything is set up as it should be and investigating and clearing any stored fault codes is also worthwhile spending money on.

XJ's are hard on brake and suspension components so any failings or weaknesses here will need to be looked at as well. I'd also give thought to having a thorough rustproofing done.

Car detailing obsessives say quite rightly you can't polish a turd - I have the same view about tuning or sticking after market bits on, and that is there's absolutely no point in doing so if the car itself is not performing as well as it possibly can in standard factory specification first of all.

Thanks Jaguar Steve. This is the thing, a lot of that work has been done in the last 5000 miles. It has been maticulously maintained by the previous owner with receipts to prove. Air flow meter and throttle body im not so sure about, are these easily done at home?. It is also personal preference as well. Im not looking to release the devil within or change it beyond recognition, simply enhance the experience with a few basic changes. The V8 is very muted and I dont want to boot it everywhereto enjoy the sound (saw 4.2mpg instant consumption on the test runs!!)

[Jaguar steve]

Bisonhead said:

Jaguar steve said:

I'd suggest you'd be much better putting whatever time and money you're prepared to spend on making sure the car is in as good a standard condition as possible before you even consider tuning it. If it were mine I'd put a few hundred towards a full fluid change including the gearbox and diff, have the third gen timing chain tensioners fitted and have a 4 wheel geometry alignment check and reset done.

It'll make a difference to the car's drivability if the breather system is clear, the throttle body and airflow meter are spotlessly clean and all the usual things like tyre quality, condition and pressure are attended too. Running a diagnostic scan to check everything is set up as it should be and investigating and clearing any stored fault codes is also worthwhile spending money on.

XJ's are hard on brake and suspension components so any failings or weaknesses here will need to be looked at as well. I'd also give thought to having a thorough rustproofing done.

Car detailing obsessives say quite rightly you can't polish a turd - I have the same view about tuning or sticking after market bits on, and that is there's absolutely no point in doing so if the car itself is not performing as well as it possibly can in standard factory specification first of all.

Thanks Jaguar Steve. This is the thing, a lot of that work has been done in the last 5000 miles. It has been maticulously maintained by the previous owner with receipts to prove. Air flow meter and throttle body im not so sure about, are these easily done at home?. It is also personal preference as well. Im not looking to release the devil within or change it beyond recognition, simply enhance the experience with a few basic changes. The V8 is very muted and I dont want to boot it everywhereto enjoy the sound (saw 4.2mpg instant consumption on the test runs!!)

Maintainence is the key to keeping an older XJ going. There was a recall on earlier (pre 2000 model) cars to have the throttlebody replaced with the later version and if your car was one of the affected and has been in the hands of a caring and enthusiastic owner it will almost certainly have been done - but either way there's no harm in making sure the inside of the body is clean. Remove the air intake trunking, gently open the butterfly valve with your fingers and spray some carburettor cleaner around the body and butterfly valve then wipe off with a clean cloth. Take out the airflow meter (see another reply of mine) and clean.

If you fit an aftermarket air intake you'll have to find some way of replacing the supply of cold air you'll loose when you remove the original air filter box.

There are instances of people removing the rear silencers and replacing them with straight through pipes - this apparently makes the V8 sound err.. more like a V8 and if that is to your taste then why not? I'd keep the original silencer boxes 'tho, that way you can put them back on and enjoy wafting in silence once again when you've got tired of the constant drone and harmonic resonances that almost always go hand in hand with modified exhausts

There are a couple of videos on utube of a blueflame exhaust on an XJ8, including one with a baseball capped cretin redlining a stone cold engine down the road - watch and wince.

[Ecurie Ecosse]

I don't think there are many recognised routes to get big power increases out of the n/a X300 or X308 engines for low expenditure.

[AmitG]

Jaguar steve said:

There are instances of people removing the rear silencers and replacing them with straight through pipes - this apparently makes the V8 sound err.. more like a V8 and if that is to your taste then why not? I'd keep the original silencer boxes 'tho, that way you can put them back on and enjoy wafting in silence once again when you've got tired of the constant drone and harmonic resonances that almost always go hand in hand with modified exhausts

At one point I removed the rear silencers on my 4.0 XJ8 and replaced with straight pipes. The sound was absolutely epic on country roads but became rather tiring in town. I compromised by re-installing the silencers but having bigger diameter exit pipes (I think they might have been from an XK). That gave a good combination of silence when wafting but a lovely V8 note when "pressing on". It also looked good (IMHO).