Can Somebody Explain Please

[Guest Kennedy48]

Been thinking of upgrading my 2b. Engine, carbs? Iv have no idea where to start. Can someone explain a megajolt to me please as someone at work mentioned it the other day. What is it. How's it work. How much, what benifits, What do I need and any one got one???

Cheers

luke

[Longboarder]

The timing of the spark in any engine is firstly dependant on the revs. Simple distributors have a set of bob weights which do this job, crudely and usually only alter the timing from 1000 rpm to about 4000 rpm. This gives a two dimensional map of timing against revs.

Next most important factor is load which can be read as manifold absolute pressure (vacuum) or throttle position. A better distributor has a vacuum advance retard function which does a fair job of this but it is a bit crude. This is described as a three D map.

Next factors which are less important again are engine temperature, air temperature and barometric pressure. A distributor ignores these and to be honest air temp and baro pressure are pretty much a waste of time unless you are up an alp or in the arctic or gobi desert. Engine temperature probably is worthwhile although a smallish correction.

Megajolt allows a computer (ECU) to control timing very accurately and throughout the whole rev and load range. You can write a 'map' of timing against revs from 400 rpm to 8000rpm giving individual timings to each point on the map. This is 2D and effectively takes no account of load. With megajolt you can then write additional maps from 400 to 8000rpm for each individual load position. This is now 3D.

Example 2d map at 4000rpm. ..............................................timing 30 deg BTDC (and that's it. no variation for right foot position)

3D map at 4000rpm using four sample points for load ..........35 BTDC at 0%load

..............................................................................................41 BTDC at 25%load

..............................................................................................38 BTDC at 50%load

..............................................................................................27 BTDC at 75%load

..............................................................................................33 BTDC at 100%load

 

Each point on the map now takes into account revs and load and often gives slightly odd results as above which a dizzy cannot hope to match.

Most ECUs sample revs and load at many more points than the simple example above. My Omex does 10 rev points and 20 load sample points. Don't know what megajolt does. Add in further corrections for engine temp and air temp and you get the idea of moving toward hugely better control of spark timing which translates into a smoother driving engine, more power throughout the rev range and a safer engine. Makes a dizzy look like a very poor compromise.

 

Nigel

[Snapperpaul]

In the new year I intend to rationalise my growing barn full of spares, I think I have a lot of Megajolt stuff.

What you will need is first off a Megajolt, there are several versions, all work well, later models have more functionality and have on the fly switching between 2 choices of map.

The only reason I can see for this function is to have a map for most of the time and a dangerous close to detonation map for racing, or perhaps one for unleaded and one for super.

 

The next on the shopping list is a waisted spark coil pack, this replaces the single output coil.

To provide an interface between the Megajolt and the coil pack you will require a Ford EDIS unit this can run the coil pack on its own but only at 10 degrees btc, the Megajolt connects to the EDIS using 2 wires PIP & SAW and tells the edis when to ignite the coil.

To tell the Megajolt where the pistons are you need a crank position sensor, a bracket to fit it to the engine and a toothed wheel with 36 teeth ( 1 missing)

It's sounds complex and difficult but for me the most difficult job was finding a a good place to bolt the sensor bracket to the engine.

[Guest mower man]

Hi I'm hoping to put mega jolt on my car after Xmas have you any drawings ,photosof a complete brkt for the timing pickup on a pinto ,I have the plate that bolts to the front of the eng but no real clue how to configure the bit that actually holds the pick up ,thanking you in advance , have merry christmas etc mower man [mick]

[steve_wilson]

for the timing wheel i bolted a 36 tooth sprocket and ground on tooth off. this was bolted in front the crank pulley. when i had it in the right position i drilled and tapped through the sprocket and crankk pulley so i could stick a couple of bolts to hold it together too.

 

the sprocket or timing disc... whatever you use, has to be concentric. i had to turn a little collar to sit inside the sprocket so it would be pretty much a push fit with the crank pulley bolt.

 

 

 

as for the sensor bracket i used a bloke off here called "laserman" he has all the cad drawings and the laser cutting tools needed to be able to sort you out with the right bracker for around £6.

 

simple as that!

 

edit pic:

 

[Snapperpaul]

I have had 2 fixing methods, one required some metal welded to the sump and tapped.

The other uses extended bolts in the front auxiliary shaft cover with a support bar bent round the engine to bolt to a spare thread in the side of the block. Not pretty but works.

The important thing is that it does not vibrate and move the sensor.

 

 

Edited December 25, 2011 by Snapperpaul

[Guest mower man]

thanks people much appreceatited merry christmas mowerman

[Guest woolly]

Apart from all the above the real noticable diference is how smooth a pinto can run compared to a rotating distributor

[Dave R]

the bracket i use, flat plate from laserman

[Snapperpaul]

Neat plate from laser man is it just 2 location points?

[Dave R]

yes i think so..... picks up the tapped holes on the block

the box section mounting holes are slotted giving you a bit of adjustment, without altering the pickup gap

[Snapperpaul]

The flat plate will need to be thick or it will flex moving the VR sensor, megajolt is sensitive to sensor movement.

As I found out any movement causes the wires to break in the plug to the sensor which causes an intermittent signal.

I spent a looong time solving that problem, that's why my bracket is big and firmly bolted, the sensor wire is shielded, a thicker grade of cable so the wire strands are more durable and I have a strip of ally that is attached to the socket the wire goes in and 2" up the cable then heat shrink over that.

Edited December 27, 2011 by Snapperpaul