Regardless of all that he’s using an X305 running the Denso, not the 16CU or the Magneti Spaghetti.

 

I agree with you as far as the AJ6 is concerned, if GM did use any of it, they did so under license, they did not "buy" the engine. Jaguar used the AJ6 in all sorts of models before during and after the Ford takeover.

 

I completely agree with you. If you want bragging rights just put NOX In it.
You saw the improvement it made on Top Gear. An XJS V12 Beating a New Turbo Porsche Ferrari etc.
Or if you want 500 horsepower there are Jaguars like the 5 liter XKR that will do it and as soon as you sign the papers not after giving a pile of cash to a mechanic. Chances are you can find a good used XKR cheaper than you can get the same 510 horsepower in your V12 from a mechanic.

 

This is good information. You see for decades I’ve been working with that black thing on the top of the engine with 12 spark plug wires going to it. Trying to get the engine to work the way I want it to rather than follow the dictates of California’s pollution laws.
Now you’re telling me and everyone else that the distributor is just a digital device I can hook my lap top up to and with a few key strokes replace all the work I’ve had to do changing springs and weights around?

Sign me up!! Explain to me where the prom chip is so I can pull that and replace it with one more to my liking?

AJ6 engineering won’t modify my ECM to take advantage of E85 and you’re telling me I don’t need them anymore, I can do it myself?

Please and if you do nothing else explain a way to advance the timing without having to crawl underneath to look at the timing marks on the bottom of the engine when the distributor is on the top?

If you do that Then I’ll admit that yes Jaguar built most of the V12’s digital.
I eagerly await your response.

 

If using a marelli XJS just drill out the distro plate thingy and physically turn it to your desired advance for that delicious high octane fuel.

 

In Ivan's case none of the XJS electronics apply of course. As noted, it's got a Denso ECU (with probably some sort of Motorola processor) and UV erasable eprom.

It controls both the fuel and the dual 6cyl Ford EDIS coil packs in wasted spark, and semi-sequential (2 fuel injectors fired simultaneously) EFI.

The XJS's Magnetti Marelli Microplex MED123 boxes (which are nearly identical to the MED120 Microplex boxes run on the 12Cyl Testarossa) are totally digital. Probably the real difference is software. The only thing the box didn't have was an analog Demux. The otherwise empty dual tier Marelli distributor serves that function.

Whether the Marelli box could at one time be programmed by interface, or if the chips were pre-programmed before being soldered down on the board, all that knowledge has been lost to the Italian sands of time and Italian record keeping at Marelli.

Anyone wanting to try to hack one would be well advised to visit Magneti Marelli Dinoplex, SAE701 and Microplex Repair and Restoration Documents

Marelli Digital IC Functions: (2 or so different ICs vs MED123)

IC1 Input Processing, Map Timing MC68705R3
IC2 Down Counter Advance Timing HCF40103BE
IC3 Down Counter, preset to 48 HCF40103BE
IC4 Ignition Pulse RS Latch MC14044BCP
IC5 Generates Clock and AP enable for Counter IC2 & IC3, Latch Reset 2&3 for IC4 MC140801BCP
IC6 Preprocessing for IC5 HCF4011BE
IC7 RPM Processing HCF4070BE
IC8 TDC Sensor LM1815N
IC9 RPM Sensor, IC1 Reset LM2903

Ivan's ECU is of course a Denso and unrelated in any way to Lucas. It controls the semi-sequential EFI (2x injectors fired at once) and wasted spark dual Ford EDIS 6cyl coil packs. Although there are tuner followings for early-ish Denso ECUs I was pleasantly surprised that a group thought they could do something with the 100797-5986 variant. I'm guessing it has a Motorola ECU like most Densos of that era. If Ivan ends up figuring out how to decipher the UV EProm tables, or even better yet, finding a comparable eeprom to replace it with, that alone will be interesting even if no other progress is made.

~Paul K.

 

Yep.. that has to be Bradly Smith's (of New York) twin Whipple supercharged XJS. Bradley used to haunt the Jag-Lovers forums in those days. Hell of a nice guy. I was sickened when we found out his heart surgery didn't afford him the extra life he would have and should have been able to spend enjoying that car. Most of what you want to know can be found out by googling his name + Supercharged XJS.

Bradley Smith XJS in Detail

~Paul K.

 

OH Yah, that looks like it will keep you busy, before it runs good!
hope i'm wrong!
has anyone have an original MAP for the XJS V12, timing and fueling, on paper?
it would seem a PreHE map would make better sense for performance engine, much simpler!

 

That’s great information. I wonder if that would work with the Lucas? I’ve always had to pull the distributor, move it a tooth and set it back into place. I’ve never messed with the few Marelli distributors I’ve owned. My knowledge of the Lucas was so hard won I tended to treat Marelli’s as foreign. ( pun intended, I’m sorry)
I went searching for power and response and found the early distributor ( pre HE ) the easiest to work with. The curve in the in the later HE distributors is so opposite what historically worked for me I kept going back. No I’m sure I can’t get the later modified distributors to meet smog laws. I’d silver solder weights on and change springs around. Then grind weight off etc. Never got an HE distributor to generate what I consider a proper curve.

 

Moving the offset front CPS sensor bracket on the Marelli car really just fools the ECU into thinking TDC is in a different place... so effectively it moves the whole map...(Similar to turning the distributor) BUT I imagine the internal MAP sensor goes some way in compensating for the ignition advance. There's what's called the "Andy Bracket" for AJ16 and AJ6 engines with CPS which changes where the sensor sits in relation to the crank to add a few degrees of advance. Makes a nice difference and works on a similar principle... Those ECUs also control both Fuel AND Spark.. so engine speed at idle is automatically compensated.


36CU ECU

Here's the guts of a 36CU ECU, as you can see there are a number of digital ICs on at least one board. Maps are in the chip that Roger modifies/replaces and there has to be a programmed processor there too.



16CU ECU

This is the 16CU (also with digital ICs on board) as you can see, it's less sophisticated than the 36CU, but it still operates similarly. Rogers site explains some of the differences.

~Paul K.

 

Possible Solution...Ceramic coating the exhaust ports. Here is a technology that make a Turbo XJS much more possible. The Jag V12's long exhaust port is particularly problematic. Distance is time so lots of heat energy passes from the exhaust port to the cooling system. Price seams reasonable.

https://dsportmag.com/the-tech/educa...or-more-power/

 

icsa, you mention thermal Ceramic coating of the long exhaust port, i did that to my exhaust ports after polishing , and the complete PreHE head surface(after resurfacing my specified amount), including the valve seats and valves !
done by SWAIN tech ,in NY! top of the line coating company, also the gold coat of piston tops!
26yrs ago , i guess ahead of the curve for engine mods!
so far no problems, i did the head surface trying to keep in more heat expansion to push the pistons more, not have it going into the cooling jackets, that may contribute to Famous Jag V12 overheating!

 

An xkr doesn't have a v12. End of story. I'll do a lot for the satisfaction of a v12.

 

Adding turbos makes it fast. Probably push it to about 600hp with pump. That would at least wax a new ss Camaro.

 

Of course there's pain, anything worthwhile is hard. Yes there is a standalone out for jags, if someone asks I'll dig it and find. It's $4000.

 

Honestly I enjoy my xj12 for more than my 98 xjr. Only thing I liked about my xjr was the cornering ability, and whine.

 

I too fell in love with Jaguar’s V12 so much so I started to stockpile them. The ones I bought were mechanically perfect ( 50 ) and out of all I looked at most were. One with a loose oil filter had connecting rods out both sides of the block but it got him home. ( talk about lack of mechanical awareness, “I just had my oil change and I smelled oil all the way home, then it got real noisy” )
Several others I looked at and passed on were obviously neglected or worked on by butchers.

 

A lot of the Jag overheating issue has nothing to do with the ports.
it is often people neglect reading the owners manual and failing to oil the distributor. Yes oil the distributor. Something like page 65 in my manual.
What happens is the advance mechanisms freeze without oil. Engine starts and runs fine but the timing is way off. = overheating.
another thing is low on coolant. There are two radiator caps. Which do you check?

or it could be as simple as leaves and trash between the radiator and A/C.
Or simply fail to flush the anti freeze semi annually.
Finally rubber rots on time not mileage. “Oh it’s only been 5000 miles since I replaced them all a decade ago.
Oops. It might also have to do with the lack of numbers on the instrument and people assuming the worst.”oh-oh the needle is more than 1/2 way across that means it’s overheating.

 

I've got a catalog from these folks from near 25 years ago: https://techlinecoatings.com/tech-li...gine-coatings/ They're nifty folks and unlike some other coating companies, sell *MOST* of their coating products (including internal engine stuff) for DIY and small shop application. Not bad prices either. So it makes it easy for those with a good shop toaster oven to apply their own piston top, valve back, sideskirt, adn bearing coatings.. and even on the heads with a kitchen sized oven.

~Paul K.

 

thermal ceramic coated ,ported exhaust manifolds, 26yrs ago.
seems i'm the only one on this site that has ACTUALLY had the ceramic coatings done , NO pix says its not happened, just a talk show!
i spoke with Grp44 head engine builder 1994, he said they would of had there engines coated, but was not available then, it was just coming available!