Viewers suggestions as to who has the best large body quick response butterfly air intake? Who makes the best throttle kit with the larger intake cone, filter box, air filter and butterfly (AJ6, Simply Performance, Mobeck Tekniske or other)? Best type of air filter with high air flow for my 1989 XJS HE with ABS brakes (paper, foam, cloth)? What is the best filter that fits in the original filter housing, brand and part number?

Who has the best fuel injection kits with the hoses, cups, injectors to be installed onto the existing fuel rail, with an easy plug and play? What is the recommended manufacture and part number for spark plugs and wires? What is the recommended manufacture and part number for injector cables?

Thanks for your recommendations.

 

[QUOTE=Patrick 1989 XJS;2893269]Viewers suggestions as to who has the best large body quick response butterfly air intake?
AJ 6 Engineering
Who makes the best throttle kit with the larger intake cone, filter box, air filter and butterfly (AJ6, Simply Performance, Mobeck Tekniske or other)?
AJ 6 Engineering (see end for points about Mobeck)
Best type of air filter with high air flow for my 1989 XJS HE with ABS brakes (paper, foam, cloth)? What is the best filter that fits in the original filter housing, brand and part number? ITG foam. https://www.itgairfilters.com/

Who has the best fuel injection kits with the hoses, cups, injectors to be installed onto the existing fuel rail, with an easy plug and play?
Genuine Bosch injectors if the OEM fuel and ignition as modified by AJ6 is kept. new are available and this guy has the best prices:
https://www.ebay.co.uk/itm/335645109...Bk9SR-zCu6DyZg

BUT, cleaning up and refurbing the old ones is all that is normally needed.
What is the recommended manufacture and part number for spark plugs and wires? What is the recommended manufacture and part number for injector cables? NGK BR7EFS, Magnacore 8mm.

ALSO: Mobec offers an entirely different proposition from AJ6. Mobeck replaces all the OEM ignition and fueling components including injectors, ECU fuel rail etc. It is a far more expensive (about 5,000USD+) and bigger change from OEM than AJ6 which costs around 30% of that. I have no experience of it, but someone on here may well have and might give us some info. What Mobeck does is to upgrade the ignition and fuelling to modern standards and adaptive peformance of fuelling and ignition.

FWIW, I highly recommend the AJ6 stuff. It transformed my car and those of my friends who have fitted it.

 

Will concur with Greg with a caveat and two additional comments.
First I have no experience upgrading for higher performance as you are obviously interested in doing.

Refurbishing the OEM Bosch injectors is far less expensive and easy to do. Clean them in kerosene or some other solvent, replace the filter baskets (get a kit), test for flow and spray pattern and you are all set. No need to buy pre cut hoses either. Buy a roll of EFI hose at an auto parts store. Cut ten pieces to desired length, I did mine at 2 3/4" IIRC. 1A and 1B hose are longer. Clean and re-use ferruels or get new ones.

Second, I have used a set of both NGK 8mm wires and a set of 8mm wires from Rock Auto. Both came custom length cut for each plug. One set was well over $200 four years ago. The other set was about $40 . Absolutely no difference noted in operation.

 

I'd seriously consider a transmission swap and differential ratio change to make the most of your planned upgrades.

With or without upgrades the TH400 trans and 2.88 diff ratio blunt the available power

Just something to think about

Cheers
DD

 

I so agree with Doug's point. The induction and ignition upgrades mentioned above will make a very noticeable difference to the V12's liveliness, and in the Mobeck case perhaps 5% more fuel effficient with the extra benfit of modern electronic reliability. However in terms of extracting substantially more BHP from the engine, say going from UK spec 12.5:1 CR's 295 bhp to (say) 340, that is just not possible with the HE engine withour major, major internal work and using pre HE heads.

A manual gearbox will make a big difference because of a) the BHP the autobox absorbs goes instead to the rear wheels, and b) you get more advantageous gear ratios, so get better off the line performance and higher cruising ratios. So if you want a great deal more performance, the induction mods and a manual box is the ticket.

 

Thanks for the suggestions. I have seen the transmission upgrade, but will that devalue the car if the transmission is changed? Is the outer case staying in the car, and can they change the internal parts to change the gear ratio? I have talked with the owner Rodger from AJ6, and he is going in for eye surgery, and he said that there is currently a backlog and not sure when he can get to my upgrade. He did not say what parts are available. He is in his 80s. Does he have another person working with him on providing AJ6 parts and going to keep the company open?

 

A manual gearbox would be the cat's meow for sure but I was actually thinking of the popular 700R4 swap..... which is relatively painless.

Some may remember that I went from the 2.88 final drive to the 3.31 ratio. It's like driving a different car. Huge improvement in acceleration. Of course the revs are a lot higher which might not appeal to those doing a lot of high speed, open road driving. That's where a 700R4 transmission would be an advantage. The overdrive 4th gear brings a 3.31 down to something like 2.55

The 700 also has a very low first gear which adds a lot of oooomph when accelerating from a dead stop

Cheers
DD

 

Simply going to a properly tuned stand alone ECU and opened up intakes will take a 295hp spec car to 330hp, Mobeck has shown this in his dyno videos.

if top HP is the goal, of course the flat head is the way to go but you can still squeeze some extra power out of an HE.

 

Roger does not have a successor, as far as I know. He certainly did not when we chatted a couple of years ago. If he eads this, good luck with the eye surgery, Roger.

 

I could be contentious here but a larger throttle body adds only noise, if you don't deal with the inlet manifolds the gains are negligable, it is the manifolds where the problems are unless you are increasing the car beyond 6 litres larger throttle bodies are pointless, then you need to deal with the exhaust. What is true are the gains from addressing the fuelling strategy and injectors - the standalone ECU - and that means ditching the 80's / 90's tech, fuel pressure is too low really in a standard system and the early generation Bosch injectors aren't great, at the pressures run by the V12 out of the factory the spray pattern is awful, plus the constraints of the day had injectors fired in groups of three. There are a lot of compromises on the V12 the 'emissions' control and all the crazy vacuum take offs and solenoids simply to cope with challenges of starting and smooth running that a more modern ECU can deal with without the nonsense.

I have Roger Bywater enhanced ECU sat in the cupboard along with a full set of new injectors (early type) as I have transitioned to an Emerald based distributorless system - but be under no illusion this is a ton of work -

At the end of the day the only way you will really prove the gains is a before and after dynamometer session - otherwise results are subjective / speculative.

 

How's the car coming along, Ben?

 

Over the years and two different V12 Jags I've done a lot of amateur experimenting. My amateur conclusions, FWIW.....

Low restriction exhaust: I've had several different configurations. Minimal power increase. However, the engine seems to rev into the power band more quickly/easily.

Gutting/removing cat converters: Same as above.

Cold air intakes: Good for making noise but that's it.

Ignition advance schemes: Slight improvement in throttle response, perhaps.

Bywater Superenhanced ECU: Works as advertised. You can feel the difference. Worth the money, IMO.

Modifying the TH400 transmission: Several simple, low cost mods work wonders. More aggressive kickdown and higher-RPM shifts points. With or without engine mods you can make a world of difference in your driving experience.

Final drive ratio: Everyone already knows my opinion on this. The 2.88 diff means you're hardly ever in the RPM range where you can feel any power. I cannot over emphasize the difference made by changing the gearing.

Cheers
DD

 

Doug
What final drive ratio would you recommend, and
What does it do to the fuel consumption?

 

Thank you for your input and information. I am not really too interested in turning my Jag into a high performance car. I already have an Aston Martin DB9. But since I am replacing or rebuilding everything on the car, I figured that I would upgrade some of the systems. I am installing a new stainless steel Bell Exhaust without the cats and first silencer and installing a Simply Performance resonator and enlarged tailpipe. I hope the car is not going to be too loud. I do want to keep the car looking close to the original, except without the extra clutter in the engine bay. Furthermore, I have decided to go with the installation of the Mobeck standard kit that keeps the distributor. I am also going to upgrade the air intake with the larger Simply Performance butterflies because I can not get the AJ6 ones. I am going to change the air filter to foam or cloth and keep the original air box with a larger cone and opening in the back for the new butterflies. I have only seen two styles of air intake cones. The cones from AJ6 and Simply performance. I like the AJ6 intakes cones the best because they look like the original cones. Do you have any parts of the AJ6 kit that I am looking for and want to sell? I just had the transmission rebuilt, but I would make some changes in the gear ratios if the work will fit in the original case. Any ideas as to what can be done to the transmission and stay within the original case? I don't really care to see a Dyno report to find out how many HP were added with the changes, I just want to feel the change without too much noise unless it is at higher RPMs like my Aston Martin.

 

@Greg in France it's coming along, the wiring harness is finally sorted mostly, I have dry fitted then put back in the box, the injectors aren't in the engine because I need to machine my new fuel rails. Although I bought some rails and yes I bought the TWR manifolds I could not use any of them (not going to go into it in public but lesson learned is all I will say), I now have the facilities to do my own machining so at some point I will try to find a way to recover the manifolds and make them useable.

The ECU has a foundation program in it that should be enough to get the car to the dyno, crank sensor etc is installed, lambda probes installed and exhausts in place, distributor is removed, coil packs installed as is the aux air valve (which is ECU controlled), AC compressor is now in and the rad pack is substantially complete (AC is not piped up yet so the dryer is still here in the house, the condenser is nitrogen pressurised, engine has been lubed and now has oil so I can spin it on the key periodically but I haven't sealed up the cam covers yet as I want to see oil at those cams and lube the chains before I go for first start, All the mechanicals are now done but I have yet to resolve the pump and filter arrangement for fuel in the boot - I thought I had that sorted until I found all the rust under the rear window that is now resolved as are the insides of the buttresses, all painted up and ready for tank replacement but I need to repair the rear arch, sort the floor aka the Dynamat and then get the wiring harness in place - also need to sort out that darn 'Rochester' - still looking for a purge solution since all the stupid solenoids and timers are gone from under the bonnet.

Tearing out the interior to sort out the harness revealed more challenges and bodged repair of the rear right arch, I need to finish scraping the old sound proofing and residue off the floor so that I can paint and put in the 'Dynamat' which is sat in a box nearby.

I am seriously considering a ZF6HP upgrade but not until the car's on the road again.

Alas I am past the age where working in single digit or negative temperatures is something that I do - my lathe and mill are both under cover, both heated and they will stay that way till it warms up and I will then machine the fuel rails, I will be making hold downs for the fuel rails that bolt to the old injector hold downs, I already have the extrusions set waiting. This is all sized to function as a pulse damper though I am looking at a bolt on pulse damper for the fuel system which means these are a bit oversized but that's no big deal as only two injectors at a time will fire (I have not gone full sequential because that requires cam sensors and that means pulling the engine apart - big no thanks on that one ...





You did ask sorry if it bored anyone.

 

3.31

No discernable difference in city driving.

About 3-4 MPG less with higher speed (70 mph, let's say) open road driving.

But you'll have so much fun you won't care. :-)

Cheers
DD

 

Sure would be nice if you could make two sets of the fuel rails! They’re exactly what I have been looking for!

 

I'd consider making a second pair once I get through the lessons learned on the first ;-) ... be aware that these are not made to suit the hose barb types but a standard top and bottom O ring

 

I am going to go with the Mobeck EFI system. I have the kit but didn't look closely at the injectors to see if they are barbed or use O rings. In any event, I was halfheartedly kidding about you making a second set of fuel rails. I am interested in what you eventually come up with though, as this is something I plan on addressing when the motor is reassembled.

 

Just to add to what Doug said, I agree that changing out the diff is the cheapest bang for your buck you can do with these cars.

The 3.31 was installed from the factory from the beginning in XJS's, and was chosen to match the gears in the transmission. This ratio was also the favorite of Norman Dewis.

Then around 1980 the diff was changed to 2.88. I'm guessing that the fuel crisis prompted both the HE and the 2.88, so Jag could show some better MPG.

As the 3.31's ended around 1980, they are hard to find, but 3.54's from 6 cylinder XJS's are easier to find, and you can grab a rear sway bar from them too. Some folks take the whole IRS with outboard brakes, although I've heard that getting the hand brake to work is an issue.

Good luck,

Rob