Hey guys, I'm planning my 2015 budget for the car and I'm reading up on the Marelli issues. I really don't want my car to burn up so my first reaction is to eliminate the problem. Should I invest in the megasquirt ecu? Who has tried it and about how much does it cost all together? I'm a newbie here so bear with me if I ask a question that's common knowledge. I really love this car and want to keep it for a long time, and of course make her growl!!!

 

I've not used Megasquirt myself, although I am seriously considering it for a Sunbeam Tiger project. A few people I know have built systems, one for an MGB and another for a Chevy drag car.

It is very powerful, very flexible and because of that has a pretty steep learning curve. You basically start from zero and design the ECU from the ground up.

If you already know a lot about fuel injection systems and how to make fuel maps OR if you have time and are willing to invest in learning, then it's great.

If you want something that is a bolt on system that will get you running quickly, then Megasquirt probably isn't what you are looking for.

Would be interested to know what you decide to do and how the project goes.

 

That's the problem... I don't know jack but I'm quick to learn!

 

Are there other plug 'n' play, ready systems available?

 

If you main concern is simply avoiding fire then there is no real reason to dump the Marelli. Just keep it in good condition condition (plugs, wires, dist rotor) and pull the cap for inspection every so often (maybe every 12/12?) and the chances of a Marelli fire a pretty slim. A module or coil could still fail but you'll feel the drop in power and know to stop driving.

Not trying to discourage a change if you really have your heart set on doing so but it's a fair bit of work just to avoid a fire.

By now everyone here (and any other Jag forum) should be aware of the Marelli thing and know what to look for. We shouldn't be seeing Marelli fires

Cheers
DD

 

I am looking into a system called Emerald. It has come highly recommended by a guy that has been using it for about 12 years. (I think).

Anyway, like Doug, I will tell you the same thing. From what I have read, the people who suffered a Marelli meltdown, were most likely those who were owners who were not totally understanding of what exactly happens to a Marelli car to cause the meltdown. A V12 Jag will run smooth, even on six cylinders, because it really is two inline 6 cylinders tied together by a common crank. Where the real fault comes in, is not knowing that if your V12 Marelli Jag suddenly loses power, you need to immediately pull to the side of the road, and shut it off!

The only communication between the Marelli ECU, and the Lucas ECU, is the speed signal sent to the Lucas by the Marelli. As it is, either bank could stop firing, and the Marelli ECU would only signal speed of the engine. Not if 6 cylinders are firing, or all 12. Just the speed of the engine. So, what happens, is the Lucas keeps signaling the injectors to fuel the injectors at the rate to continue existing speed. With that, raw unburned fuel continues to flow, right into the cats, and the cats, already heated, do their job to burn off any unburned fuel. They super heat, and well......

To wind this up, if you know your car, its "normal" operation, I doubt seriously, that you will ever suffer the Marelli meltdown, even if you have the Marelli misfire. Then, as Doug advises, keep the plugs changed regularly, service the car as you should, and "maybe" even do the silicone under the rotor, and the Marelli should give all the performance you want in a stock V12 Jag.

 

What would be really cool would be to be able to shut off one bank when you are cruising.
if you could shut off one bank of injectors when you are travelling (at the national speed limit of course) on the motorway you could save a shed load of fuel just running on 6 cylinders.
Have the other bank wired into the kick down switch and when you booted it all 12 cylinders come on line.
Brilliant idea, why hasn't anyone thought of it?
I'm sure that a large list of reasons as to why it can't be done will shortly follow!

 

Didn't Cadillac do that with one of their cars in the 80's?
Don't think it went down too well though ...

Larry

 

I think that Corvette had a system with 2 ignition keys, each controlling a separate bank of injectors?

 

The much ballyhooed "V4-6-8" system. Yes, it was a dud....but it's been so long ago that I can't remember the specifics

Cheers
DD

 

Foggy memory, subject to correction, but I *think* the ZR1 Corvettes of the early 90s had a switchable power setting so that the owner could set the car loose with a less-experienced driver with less worry. There was a separate key-switch in the console....that used the ignition key.

Your mention of a 2-key system might be correct as well, perhaps on later models? One of the keys was 'chipped' for a lower power setting?

I think the lower power settings operated by simply reducing injector pulse width and retarding ignition timing. Someone with a good memory will come along

Cheers
DD

 

Switching fuel, ignition off isn't a great idea. The resistance of the cylinders that were not "working" only drop performance, which requires the other cylinders to work harder, which burns more fuel, not less.

I try and read everything automotive I can get my hands on. But like a retired friend of mine, who was a R&D physicist once told me....it takes a certain amount of energy to move and overcome the relative rolling resistence and weight, regardless of how you do it.

Like the article I read the other day...clearly showed that unless we figure out how to produce electricity much more efficiently, even electric cars can't be a answer. If we tried to go total electric, even if feasable, would take far more energy than we can produce.

 

it takes X amount of energy to move X amount of weight,X amount of distance!

Diesel engines do it best with high torque, and not much HP.

they just loaf along pulling the weight, so less fuel is consumed, to cover the distance!

course D fuel has more BTU energy than gas or petrol.

 

doug GM uses a different approach nowadays, most of there engines and many other companies are using cylinder deactivation(pioneered by Cadillac).

the world of electronics has made it possible.

and because they can hold a valve slightly open, there is little pumping losses.

as supercharged mentioned.

as i understand it its something to do with electromagnetic lifters,or some such, but it does work, and makes big V8 get reasonable MPG.

the car industry is in a great and wonderfull change, we are the new Dinasaurs!

 

if anyone has noticed a lot of manufactures are touting Magnetic suspension control!

yup,, a GM Cadillac patent for the 1st production car!

who in hell ever heard of Magnetic OIL, in a shock absorber????

 

and OP , i use an SDS standalone ECU, on my 1978 XJS V12.

google SDSefi, lot of info and many yrs experience!

 

A fair amount of newer cars do shut down cylinders when not in use cruising. My 2014 GMC Sierra 6.2 goes from 8 to 4 cylinder when I'm just cruising and the computer doesn't "anticipate" a sudden need for power. There is even an icon that shows V8 or V4.

The early Cadillacs did it using more mechanical control than today's computer controlled cars and had a harder time. One of the big issues with the newer cars is still a smooth transition between 4 and 8 cylinder operation.

 

I also have an electronic ECU in the back of my head. Like was mentioned earlier, take care of the Marelli, and know what to look for and it shouldn't be a problem. But I still have that nagging "what if" in the back of my mind. And because of that, I still think of computer controlled ignition from time to time.

KWE is a British company that refurbs the XJS. One of their options is computer controlled ignition. They use the Omex engine management system. Probably complicated, but known to work.

 

I am about to go the MegaSquirt route. If you are handy have an understanding of how EFI works then MS is a very cost effective way of upgrading the ECU.

I will be doing mine in stages. I have 2 MS2 V3.0 complete ECU's so I can get one going fuel only while I modify the other with additional ignition outputs.

Initially using the MS2 for fuel and the Marelli for ignition. The MS2 only has 1 HV ignition output, so I need to modify it for 2 logic level ignition outputs so I can fire the 2 Marelli modules. The MS2 is capable of 6 logic level outputs to directly drive coil packs, but needs modification to the PCB circuit. If you are not able to this going with a commercial system might be easier.

 

Megasquirt is your best bet in a 25+ year old car. Fresh system is a fresh start . I am a ASE cert mechanic n all that good bs ,This is the route I will be going with mine ms3pro is a great system for the price it can not be beat . Good level of inputs on it perfect for our cars. The only other option I have found is the electromtive tec3r for 2500 no real difference but a price tag in my opinion someone correct me if I miss something.