Whats the best way to make a 3.6 auto XJS faster?
Discussion
Hi all....as per the title...to save me getting a V12 instead!...obvious ones...lose weight (the car, not me!)..air filter...straight through rear silencers....what about stuff like AJ6 Engineering high torque manifolds etc?...anybody tried them?...and...is it possible to reprogramme the autobox to hold lower gears longer?...any info appreciated...cheers..
TWINTURBODAVE said:
Hi all....as per the title...to save me getting a V12 instead!...obvious ones...lose weight (the car, not me!)..air filter...straight through rear silencers....what about stuff like AJ6 Engineering high torque manifolds etc?...anybody tried them?...and...is it possible to reprogramme the autobox to hold lower gears longer?...any info appreciated...cheers..
Get a 4.0 or a v12 instead.Unless you have some special affinity for the 3.6 you'll be throwing money down the drain as the car won't be worth any more at the end of it.
its hard to get any big gains from any AJ6 without spending a hell of a lot of money.
there is a chap over on another forum trying to do that from a 90 XJR, and really struggling to find parts.
even looking at trying to use Aston Martin parts, but again it all comes down to how much do you want to spend. i have the K&N panel filters in two of mine, but again these are very smaller gains i reckon. K&N say 3%, but i think its closer to 1%.
personally i think a manual box conversion is the best way to improve performance over an auto. obviously it doesn't give you more power per say, but it makes the available power much more usable/ accessible.
later 4.0 xjs has the electronic sports mode box, if you want to stick with auto. does make a difference using sports mode. i have it on my 93 4.0 sovereign auto
there is a chap over on another forum trying to do that from a 90 XJR, and really struggling to find parts.
even looking at trying to use Aston Martin parts, but again it all comes down to how much do you want to spend. i have the K&N panel filters in two of mine, but again these are very smaller gains i reckon. K&N say 3%, but i think its closer to 1%.
personally i think a manual box conversion is the best way to improve performance over an auto. obviously it doesn't give you more power per say, but it makes the available power much more usable/ accessible.
later 4.0 xjs has the electronic sports mode box, if you want to stick with auto. does make a difference using sports mode. i have it on my 93 4.0 sovereign auto
XKRacer said:
Put a manual in it....... Swap for a supercharged AJ16........
I put a supercharged V8 with a manual in my 3.6 when I had it
Hi...that sounds awesome....please elaborate....did you do all the work yourself?...and you are saying that you mated a v8 s/c engine to a 5 speed getrsg box?....what were the main issues?....and what about the electrics/ECU?....do you have any photos?...its sounds awesome..I put a supercharged V8 with a manual in my 3.6 when I had it
I just had what I think is a good/great idea! 
.....how about buying a V12 and then replacing the diff with a higher geared 3;54 from a 6 cylinder car...it would be punchier than the V12 's 2.88...should be quite rapid to 100 mph plus....
I already have a set of Koni gas adjustables and lowering springs...and perhaps I could get my hands on the Jaguarsport anti roll bars...a bit thicker than standard?....plu twin K 'n' N air filters....and straight through rear silencer pipes...crikey, I am licking my lips as i write this! lol....its exciting...
What do you think?.....does this have the basis of a satisfying road racer?....
How can I hit 350 bhp cheaply?...I think that would be a nice meaty motor....
.....how about buying a V12 and then replacing the diff with a higher geared 3;54 from a 6 cylinder car...it would be punchier than the V12 's 2.88...should be quite rapid to 100 mph plus....I already have a set of Koni gas adjustables and lowering springs...and perhaps I could get my hands on the Jaguarsport anti roll bars...a bit thicker than standard?....plu twin K 'n' N air filters....and straight through rear silencer pipes...crikey, I am licking my lips as i write this! lol....its exciting...
What do you think?.....does this have the basis of a satisfying road racer?....
How can I hit 350 bhp cheaply?...I think that would be a nice meaty motor....
TWINTURBODAVE said:
Hi...that sounds awesome....please elaborate....did you do all the work yourself?...and you are saying that you mated a v8 s/c engine to a 5 speed getrsg box?....what were the main issues?....and what about the electrics/ECU?....do you have any photos?...its sounds awesome..
Everything was done by me to a large degree....... XKR 4.0 with a dodge viper T56 ran it on a Motec M800 that was 10+ years ago.... Clutch was an XJ220 from AP racing with the hub plates changed to 26 spline to match the T56I took it all out and put the car back to standard (kind of) and stuck the gearbox into my XK8, sold the XJS for £8K last summer
I still have the engine mounts I made if you are interested
I would stay away from a V12..... Cost even more to tune than the 3.6
If you want 350bhp, I'd get a V12, convert it to a manual gearbox, change to the 3.54 diff and then get a few bits from AJ6 Engineering to perk it up. I've got a V12 manual as above, but with the 2.88 diff which means it's good for 'economy', but could be a fair bit quicker. Might swap out the diff this summer, if funds allow.
HaylingJag said:
6 ltr XJR-s ?
The power you're looking for, suspension your looking for and all built by Tom!!
D
Hmmm...that does make sense, doesnt it?...However, from everything i have read, they are not quite as fast as we might imagine...they all have cat converters, and so even though they produce more power, that power is robbed by the exhaust system...i think ( i might be wrong) that the Pre He's are actually quicker..because they have the flat heads and breathe better...plus I think I actually prefer the non-bodykit look....or perhaps a Lister kit...but I would still consider one...The power you're looking for, suspension your looking for and all built by Tom!!
D
HaylingJag said:
6 ltr XJR-s ?
The power you're looking for, suspension your looking for and all built by Tom!!
D
On second thoughts...that does sound like an idea...it would be a great base...i would have to convert to manual....and tune the engine to 350 bhp....i think i would have to buy a slightly scruffy example...mechanicaly sound, but perhaps cosmeticaly a little used...simply because i would feel guilty about modifying a XJRS...and would want to deplete the remaining good cars...because I do think they are iconic...to Jag people at least! The power you're looking for, suspension your looking for and all built by Tom!!
D
....naki said:
its hard to get any big gains from any AJ6 without spending a hell of a lot of money.
there is a chap over on another forum trying to do that from a 90 XJR, and really struggling to find parts.
even looking at trying to use Aston Martin parts, but again it all comes down to how much do you want to spend. i have the K&N panel filters in two of mine, but again these are very smaller gains i reckon. K&N say 3%, but i think its closer to 1%.
personally i think a manual box conversion is the best way to improve performance over an auto. obviously it doesn't give you more power per say, but it makes the available power much more usable/ accessible.
later 4.0 xjs has the electronic sports mode box, if you want to stick with auto. does make a difference using sports mode. i have it on my 93 4.0 sovereign auto
Hi...what Aston Martin parts could be used?...there is a chap over on another forum trying to do that from a 90 XJR, and really struggling to find parts.
even looking at trying to use Aston Martin parts, but again it all comes down to how much do you want to spend. i have the K&N panel filters in two of mine, but again these are very smaller gains i reckon. K&N say 3%, but i think its closer to 1%.
personally i think a manual box conversion is the best way to improve performance over an auto. obviously it doesn't give you more power per say, but it makes the available power much more usable/ accessible.
later 4.0 xjs has the electronic sports mode box, if you want to stick with auto. does make a difference using sports mode. i have it on my 93 4.0 sovereign auto
TWINTURBODAVE said:
Hi all...just to update...I have just purchased a 1978 Pre He XJ-S V12!.. auto...been stored for some years now...should be an interesting project...
Post some photos..... be interesting to see it and how you get on.. Now fit some K&N's, straight through pipes (removing the centre exhaust) and cut the air filter tubes down and pipe the cold air from the front valance. Makes a huge difference. Then AJ6 ECU.... 
Just to add, I added the K&N's and the exhausts and it really did not make too much difference then I had the injectors Ultra sonically cleaned (by KWE) and piped in the cold air from the valance and wow, what a difference, especially over 80 mph!
Edited by V12 Migaloo on Friday 25th January 12:00
Also WIN SPEED changed my coil for a FIAT coil..... removed both coil packs. I think this helped with the spark as well as my last plug never gets clogged up now..
Edited by V12 Migaloo on Friday 25th January 12:02
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