Autosport Labs

Hello All,

I am new to the forum. It is a wet and miserable Sunday in my part of England, so I have spent the day reading up on engine re-builds. I am going to have a go at a 3.5 block as I was given one yesterday. It will replace the current lump that is EFI. I am not going for an agressive cam, just one with good low end torque. The EFI will be retained and it is a flapper AFM.

The distributor is the limiting factor when it come to water so I have been looking at EDIS. Megasquirt is OTT for what I want so I am now considering Megajolt. I have a few questions.

Will it work with my EFI system?
Anyone done this?
I can't find any maps, so do they exist or can they be worked out?

Regards,

Paul.

Juist to add:

I will go for the MAP option. Can the MAP sensor be external. The reason is that I would mount the Megajolt unit in the cab behind the drivers seat where the ECU is.

Would I then use the rubber tube that is currently used for the dizzy vacuum advance?

Paul.

Hi Paul....and welcome

mrcheese wrote: Will it work with my EFI system?

Don't see why not. Fitting a MJLJ in parallel to an OEM EFI system is quite common

mrcheese wrote: Anyone done this?
I can't find any maps, so do they exist or can they be worked out?

There's a whole load of stuff that you will probably find useful at http://otly.mysite.orange.co.uk/

mrcheese wrote: I will go for the MAP option. Can the MAP sensor be external. The reason is that I would mount the Megajolt unit in the cab behind the drivers seat where the ECU is.
Would I then use the rubber tube that is currently used for the dizzy vacuum advance?

The MAP version of the MJLJ has the MAP sensor internally to the unit, so all you need do is connect the bulkhead connector on the MJLJ to a suitable vacuum take-off point - with the existing take-off point for the dizzy probably being fine. I wouldn't want 20 feet of tube, but the install on my rally car had about 6 feet of vacuum pipe and that worked fine....

Hi Paul,

Welcome, and glad you made it through the forum's registration process!

For the hose distance- the subject hasn't been discussed here too much much, but it was an old topic on the Megasquirt forums and 10 feet of hose only has a signal delay in the low millisecond range. You should be quite fine with your fitment behind the seat.

As far as integrating it with your EFI system- no doubt that it looks to the existing distributor for an RPM signal. you will need to figure out how it senses that signal and then choose one of the several options for feeding this. You have a choice:

(all covered in the "Vehicle Installation" section (HOW TO link at the top)

- TACH_OUT on MJLJ - I use this with my Megasquirt V1.1 tach input, which works well
- PIP on EDIS - also may work to feed the RPM signal

Failing the above, if your EFI system needs to see a high-voltage spike that the stock coil normally produces, you could implement the high voltage adapter circuit also shown on the Installation Guide.


Regards,

Thanks Brent. The ECU takes a timing signal from the negative of the coil. I will need to figure out what levels it is seeing and how many pulses per revolution. Anyway, the problem seems to be one that should be relatively easy to overcome. I need to do some more investigations. I have heard that a few people over here have already done this in challenge trucks.

If anyone is interested in the EFI system I have then check this link out.

http://www.pixeltechnology.co.uk/wedge/ ... ection.pdf

If I find out more I'll post in case it helps others.

Regards,

Paul.

Paul,

I have an up and running Megajolt on my Rover EFi flapper system. It was relatively easy if slightly long winded to get set up. Hopefully these are a couple of useful tips.

Trigger wheel - I bought one specifically for the Rover from a site advertised on here, trigger-wheels.com I think. It bolts right onto the back of the standard front pulley.

Interfacing to EFI - I used four diodes, one from each coil through a 6k8 resistor then on into the EFI loom. This worked fine. You may (should) already have the 6k8 resistor, it's a little black square with two male spade connectors on it that looks like a gender changer, but it is often missing. I tried using the 18v zenor approach instead of the 6k8 resistor but that didn't work so well.

Timing - My engine would not start when hot with the default 10deg advance that the EDIS gives on limp home. But when I have the Megajolt connected and set the timing to 6deg it starts first time every time. So don't condemn the system if you have problems starting - try and back the timing off.

Leads - Don't pay too much. I got a set of 8mm leads made to my spec and delivered for £45.

I haven't tried to map it yet as getting some axles on it is a higher priority!

Regards,

Cliff

Thanks to everyone for their replies. On another forum I was offered a built Megajolt unit for a very good price. It has been built, but not fitted and the owner has now gone Megasquirt. I just need to change it from TPS to MAP.

Trigger Wheels in the U.K. supply all the extra kit I will need (wheel, sensor, EDIS-8). It all depends on what I decide to going hunting for at the scrapyard.

Regards,

Paul.