Megajolt connection
Turbo Mini Forums

I,m back again with questions on Megajolt - I,m just no good with electronics.

Just got round to mounting the MJ unit as part of the wiring marathon and had not previously noticed that the connection for the laptop is different to the one on my other car.


What sort of connection is this, please ? and do I still need an adapter of any sort to link to the laptop ?

The lead has a sort of phone plug at both ends, then that pulgs into a sort of adaptor for the laptop.

Sorry if this is of no use to you.

I have started posting on Instagram also my name on there is turbomk1golf

Nothing is impossible it just costs more and takes longer.

Maplins do them I think

It's an RJ11 connector. You need to patch up a lead to suit this to convert it to either a DB9 (parralel) or USB connection depending on if your laptop has the parallel port.

What I did was make a lead up via:

RJ11 male/male phone lead ---- RJ11 to DB9 adapter ---- DB9 to USB

RJ11 cable - http://www.ebay.co.uk/itm/ADSL-Broadband-M...=item4acd1d3b04

RJ11 to DB9 - http://www.ebay.co.uk/itm/DB9-female-to-RJ...645ca1">RJ11 to DB9</a>

DB9 to USB - http://www.ebay.co.uk/itm/USB-to-Serial-RS...=item461a9abd4d

Edited by adcyork on 11th Feb, 2014.

Im not the best with computers either. Got all my stuff from trigger wheels. May be a few quid more, but at least you know its all compatible. Also the trigger wheels support is second to none! Any issues they will be happy to talk you through whats going wrong

Hehe sell it and buy a NODIZ.. less wiring (No ancient EDIS module), bluetooth for communications, easy :)

Thanks everyone -TM comes up with the goods yet again !

I have a new coilpack a new EDIS and a new MJ so no chance that I will be switching to NODIZ any time soon.

No probs, when you fancy the upgrade let me know :)

I just made my own rj11 to db9 serial lead in my build thread, it was a faff to solder but I think a neater solution to the adapter supplied to convert the two

Looking around I have found a ESB to LAN ethernet connector which looks as if all I need to do is plug that to the RJ11 male to male and then into the laptop - or am I being stupid again ?

I believe you need to go through a usb adaptor. Thats what I had to do on mine...

LAN is an RJ45 connector, same style as an RJ11 but 8 pins wide instead of 6.

Also the LAN transmission protocol is a lot different to good old RS232 which is what you need.

Basically you have to convert USB (unless you have an old enough laptop to have a genuine serial port) into RS232 serial which is usually the DB9 connector.

The newer MJs, and my TechEdges, use the RJ11 plug/socket instead of a DB9 because it's smaller neater (and they only use 3 of the 9 wires anyway).

Unfortunately 99% of the basic USB to serial convertors only convert it to a DB9 plug/socket, hence the string of adapters adcyork suggested above to get it to an RJ11 plug.

If you're brave (as per Carl above) you can make your own cable to do the RJ11 to DB9 conversion, I'm sure Autosports labs or their suppliers must sell them ready made up but I also made my own and soldered on the DB9 for my TechEdges.

Otherwise it's the string of convertors already mentioned, you will be very lucky to find a USB to RJ11 (RS232 serial protocol) convertor direct in one piece at a sensible price.

EDIT - typo (and I quoted the wrong number of pins and I didn't use a modem cable, I bought the RJ11 connectors.... having a bad day....)

Edited by Rod S on 11th Feb, 2014.

Schrödinger's cat - so which one am I ???

Thanks Rod.

I have a proven RS232 so I,m part way there !

Double edit...

Just looked at the Autosports site and it seems they are using the 4 pin version of the RJ11, not the 6 pin I'm familiar with but if you want to make up your own cable, google (images for) "Megajolt serial cable" and it gives you the wiring diagram.

Schrödinger's cat - so which one am I ???

The diagram confused me a little until i had everything in front of me, the db9 in the diagram is the face of the female connector, and the megajolt rj11 is looking at it as if it were in front of you. Could make for some mistakes if you aren't careful and double check

I,m back again -sorry

I have a DB9 to RJ11 cable and an RS232 as well as a male to male RJ11
The RS232 clearly plugs straight into the laptop. The adapter to RJ 11 plugs male/female DB9 no problem and the other end is a 6 pin RJ11 which fits straight into the MJ unit.

I,m pretty good with welder, grinder and spanners but this electickery just does my head in.

Will the above work or have I bought the wrong DB9 to RJ11 adapter, despite the help above ?

Edited by Rod S on 15th Feb, 2014.

Schrödinger's cat - so which one am I ???

Obliged to you again Rod.

My MJ is 4 pin and it looks as if the RJ11 connector will align with the centre 4 as you say.

I,m some way away from trying it yet but have no doubt I will report back !

You could always power it up on the bench with a battery and check that you can connect to it.

it what i did only t find out i'd soldered the MAP sensor in upside down.

Gives you the chance to flash it with new firmware too.

What the mind can conceive the mini can achieve
MITP 2012 17.01 seconds 1/4 mile against "The Don"
MITP 2013 16.83 seconds 1/4 mile

Yes lee I know, but I am such an idiot with these things I might knacker it by connecting something wrong!

It's very difficult to do something wrong with RS232 serial cable wiring that will do any harm, well apart from plugging it into the 240V mains perhaps.....
If the Rx, Tx, GND connections are in the correct order it works, if they aren't, it doesn't talk.......

I agree with Lee, try it indoors first with the MJ off a battery. If it's a big battery (ie, car battery) or some other high current 12V supply (I use and old PC PSU which can also do really high currents at 12V) just use a sensible fuse (like 1 or 2A) in the supply.

Schrödinger's cat - so which one am I ???