The technical aspects of this thread are way over my head, but whatever you guys get from this... sounds like there's a pent-up demand for this upgrade in a nice kit form.

 

So has anyone done this to a X300? I have a '95 XJ6 that could really use a performance upgrade, and it already has a crank position sensor, and cop ignition, so it sounds like it could be a nice upgrade. Even though it is not a XJS V12 and a bit of a sleeper, it would be nice to get a little more out of it.

 

maybe rob beeres I6 blower kit could help you out.

 

I've been looking into the same options for my '85 XJS. This caused me to do a lot of research on the 16CU that's currently in it. I've come to the same conclusion...If you're not changing to distributorless, then it's not worth it. If you go with the new MSIII, it's capable of going wasted spark or sequential. DiyAutotune sent me the modification diagrams for the standard MSIII to make it compatible with the v12 (Like the MS3X). You'll have to use the peak and hold drivers ( which is only an LM1949 ), for the low impedance injectors. You'll probably want to batch fire the injectors, so you won't need 12 of them for your application (perhaps 6). The more I look into this, the more I appreciate what's already in it. I'll probably relocate the ignition amp though. BTW, I have all the diagrams etc. for that GM HEI that's already in it. If I had a Mirelli I would definitely be more interested in changing it. I'm also looking into the idea of building an EDIS system that plugs into the existing ignition for distributorless operation. This would create a resource for modifying the existing system without having to go through all the tuning that is required for aftermarket systems. Since I do have a background in embedded system design ( Mostly Sil Labs 8051 derivative cpu's ), I should be able to figure it out. Just not sure if I have the time to do it yet. You might also be interested in looking at what this guy did ( Back in '03 ), to his XJ12. He used 2 GM computers to do it ( pretty impressive ). http://www.fixedbygary.com/efi/index.html

 

Yes, it also needs that signal to pin 16 for the ECU to determine the timing for the injectors. If that signal is not there, nothing will happen.
..

 

Correction, I believe it's actually pin 18 of the ECU ( Speed signal )

 

Absolutely agree!

Greg

 

nice system, when i did my standalone fueling computor, back in 1994-5 i used all sensors from GM stuff(thank heaven for GM). my ECU is SDS,simple digital systems, with a hand held programmer box, after getting used to it,I do like it!

and talk about over ones head on tech, i'm a far better mechanical tech than an electronic tech. there was almost nothing on the net,back then, for such things, more came out of OZ. than here.

but after much time, testing and TUNING,it actually runs good.

like the TV commercial, BACK IN MY DAY THEY DIDNT HAVE ALL THIS FANCY SHMANCY STUFF.

 

YOU GUYS DONT KNOW HOW GOOD YOU GOT IT! hehe.

and a complete kit form, would be great, not counting the price, that could make or break the deal!

 

On another note, the GM ECU's have been hacked in every conceivable way...there's a lot of info on them....I've been following the diyefi boards and those guys seem to be REALLY savvy on this stuff. I'm probably not going to go that route though. I would like to make my own system. As far as the injectors are concerned, you'll find that sequential won't cut it...especially when you go further up the power curve, the injectors are open more often than they're off. That's why I want to keep the 16CU and perhaps modify the spark control instead. I'll have to program my processor to send out two SAW signals synced to the falling edge of PIP. If I ever get the time to do it. Retiring next year, so that should give me some more time...that is if a loaf of bread doesn't go past 100 bucks by then.

 

You can find more on the GM ECU projects at ThirdGen.org

 

HEY Mag, go for it

as you know austin is a techy town(computor nerds).

when Nissan came out with there super GTR R35, saying computor cannot be hacked for power mods, well along comes this guy and asked if he could borrow a box,he'd give it a try, comes back around a week later, put it in doner car, plugs in his laptop,and like magic got 70 more WHP. on the dyno.

gotta love modern electronics, i'm kinda caught in the middle with it! but i do believe in it 110%.

 

and yes, GM electronics fit the american mind set so easily.

german elecs seem complcated.

english are unusual to say the least.

Japanese are easy to understand, and OZ is refined USA!

that my take on it.

 

last but not least, talking with my SDS ECU guys,the owner of the company worked for GM Delphi for 10yrs!

 

Greg,
Have you ever measured the resistance values of your throttle potentiometer? Mine is not working and I'll need to replace it with something. I've read that the Tru-Tech TH59T can be used to replace it...But I don't know how it's resistance values compare to the original Potentiometer. Since I have an '85 as well, yours should be the same one. BTW, thanks again for all your other answers to my questions.
...Doug

 

For those not wanting to use the MegaSquirt facility for ignition systems on Pre HE V12s but wanting to substantially improve the V12 ignition anyhow when going to MS, I have a viable and cheap alternative to Opus and Crane optical. This alternative came about by the failure of the Opus and then the highly recommended Crane optical system on my old S2 V12. In fact, two Crane modules died - the first after 12 months and the replacement coincidentally about 12 months after that. I had the Crane modules on the radiator support panel too!

So I should mention I am a mechanic (and a Jag lover). I hit on this idea after reading a brief on the S3 HE ignition system in the S3 repair manual. I was very impressed and thought should my Crane system ever fail again this is the route I should take.
... Moving right along, what I did to my car was fit an HE ignition system to a Pre HE engine and it worked perfectly. The power, smoothness and hot starting was better. The idle quality was better too but the biggest improvement was over 5500rpm. The willingness of the V12 to really rev up and the complete smoothness up high in the rev range (regardless of high ambient air temperature) was what I most noticed. Fuel consumption improved a bit as well.

Mechanically inclined people who are Jag enthusiasts should find this mod fairly straight forward I think. When I began I was unsure if I could get the Pre HE advance mechanism to work and was worried if I might be wasting my money trying to get it all to work. I can confirm that it does work.
Since it was 10 years ago, I can't remember all the exact details but I don't think this shouldn't deter anyone.

So the mods involve acquiring an entire HE ignition system including distributor, coil[s] and the ignition module. Inside the Jag box I replaced the old GM 4 pin HEI module with a new one (it's just an off the shelf GM one as everyone I'm sure already knows). I located the wiring diagram for the HE ignition system and wired the system into my 1976 S2 V12 easily. You have to bypass the Pre HE ballast resistor from memory and make a harness for the non firing coil which is just wired in parallel to the firing coil. You don't need to do this if going single coil.

Basically, what I was attempting to do was to fit the reluctor and pickup mechanism of the HE to the advance of the Pre HE and keep the mounting points for the trigger board required for the early fuel injection system.
It can be fairly easily done but I can't remember which distributor body I used. Whatever way it was the phasing of the pickups to the distributor cap poles is identical to standard - NICE!
So this is the bit I can't completely recall but it was also pretty straight forward. I modified either the HE distributor by fitting the Pre HE lower distributor shaft and advance assembly, OR, vice versa I modified the Pre HE distributor by fitting the HE "breaker" plate with reluctor, pickup and upper distributor shaft to the PRE HE distributor. It is also possible I just fitted the HE "breaker" plate with pickup under the standard upper distributor shaft and the reluctor wheel fitted in place of the Opus wheel - I just can't remember; sorry.

Also, if you have a S2 you can't fit the HE ignition box to the S2 radiator support panel (doesn't fit) so I fitted mine to the R/H air cleaner; mostly because I was too lazy to be bothered putting it anywhere else. Interestingly, the heat never ever worried it.

At the time, since it was near Xmas and I didn't want to buy a new coil until I knew if I could get it to all work. Every later secondhand single HE coil at the Jag dismantler were showing significant charring inside the secondary or high output area so I was forced to go with the older dual coil arrangement.
I fitted the firing coil in the standard location on the throttle pedestal and the non firing coil went on the alloy brake booster bracket. Incidentally I never fitted a single coil as the dual coil worked so well I just left it alone.

I clearly remember the first start. Hardly any winding of the motor and it fired instantly. The idle was now smoother with almost no hesitating or popping when snapping the throttle open. The idle speed needed turning down and the cold throttle response was hugely better. Driving, the motor was quieter and the motor revved to 6000rpm significantly faster. In fact at 6-6500rpm the motor was entirely different.


This HE system with its capacity to increase current the higher the revs go makes for a really cheap high performance ignition system on the pre HE. If attempting this mod now, I would recommend a brand new modern single coil instead of the dual coil or secondhand single coil.

ps.
As I'm thinking about it, I must've used the original distributor body as it has the mounting holes for the early injection trigger board.

 

I think the easiest and best way to re-ecu a V12 is with the EFI system from a 90's Nissan 300Zx for the following reasons. but...you need two of them, 1 for each back of the V

1. Nissan system is from a peformance car and there is DIY tuning software available.
2. The Nissan system is mass air flow so it's dead accurate and easier to tune.
3. Harness is avabile and low cost.
4. Nissan system is coil on plug
5. For timing... Distributor rotor is replaced with CAS which is a high resolution optical trigger for fuel and ignition timing.
6. Nissan idle air vavle is seperate and can easily be adapted to the Jag manifold becasuse the design is similiar.

 

well my Crane system is working great 16yrs, had to replace one box, after i used a high current coil(burned it up). altho i do use a standalone fueling ECU,SDS.
it revs to 6500-7000rpm no problem, i set my rev limiter at 6750 at present its not pulling much if any after that, took a while to sort out, but all good so far!

BUT today i would absolutly use a CAS system, along with a fully adjustable ECU, both fuel & ignition, do away with that old fashioned distributor completely!

what icsamerica says is very good advice, and would be a great learning experience.

 

I'm glad my two Crane units failed - with hindsight. I wasn't that happy at the time but I feel the HE ignition system offers superior durability, reliability and performance to the Crane offering. Also if fitting an HE ignition system to a Pre HE you get an injector pickup for MegaSquirt at the ignition box as the HE injection system did it this way.

I would recommend reading a description of the HE ignition system. It is very impressive. Coupled with a modern low impedance coil you get a really decent (and pretty cheap) ignition system that very simply, varies current to the coil depending on load. It resists heat too.

 

I'd like to see more on this 300zx setup...icsamerica?