StevieB
|
| posted on 23/9/06 at 10:38 PM |
|
|
Megasquirt/jolt + some other bits
Hi,
Can anyone explain (in very basic terms) the whole megajolt/squirt thing and whether either can be run on an R1 engine.
I've done a bit of basic reading and like the sound of it, but there's a lot of complicated material to work through before it makes
complete sense - I'd rather get a simple answer as to whether it's worth me bothering any further or not.
Also, does anyone know of any means by which you could put a display in place that would also show speed/revs/fuel etc. (home made digidash,
basically).
Cheers
Steve
[Edited on 23/9/06 by StevieB]
|
|
|
|
|
SixedUp
|
| posted on 24/9/06 at 08:28 AM |
|
|
Simplistically, MegaJolt and MegaSquirt are programmable ignition and injection systems respectively. So, they do the same thing as a modern car (or
bikes) ECU, working out how much fuel to put into a cylinder, and then when to fire the spark.
They work this out based on a combination of factors, the two most important of which are the RPM and the load that the engine is under, using a table
(or map) which tells it for RPM "x", and load "y", ignition advance should be "a", and fuel should be
"b".
The advantage is that you can reprogram the map, changing the entries to exactly suit your engine, and since its all done electronically, its
accurate, and not dependant on things like springs and weights and stuff. Generally you get optimum running at all speeds and loads, which means
better throttle response, lower fuel consumption etc etc.
The disadvantage is that they're possibly more complex to install, and lot more complex to set up as you need to either create that initial map,
usually on a rolling road, sometimes taking a day or more on the rollers, or fine tune an existing one to your particular engine setup.
As to whether or not its worth you bothering, the R1 will already has an ECU, so unless you're going to modify the engine, I'm not sure
how much you'd gain by going down this route.
Re the home-made digidash, people have done this in the past, but it tends to involve stuff like PIC programming, and electronics to interface to the
sensors. You'll also be limited to "off the shelf" displays, which are going to be hard to make into something that looks smart. If
you're going with an R1 engine, and fancy a digital dash I'd look at the Acewell range. I'd be surprised if you could build
something as cheaply as they sell them for...
Cheers
Richard
|
|
|
oliwb
|
| posted on 24/9/06 at 08:39 AM |
|
|
Basically,
Megajolt - is an ignition controller...it replaces the distributor and dishes out spark to the engine. The way it differs from the dizzy is that it
doesn't have any moving (wearing!) parts so you never need to replace anything like points etc. This also has the add on effect of allowing it
to accurately dish out the sparks at anything up to 19,000 RPM say. Whilst none of us will probably ever use this it does mean that 6,00 rpm is a
lazy idle which it can accurately cope with where as a dizzy would be struggling much past this to mantain its accuracy.
Another way it differs is that it has more inputs and adjustability than a dizzy. Most dizzy's working using bobs and weights to control the
advance curve. This basically means that as the revs build the advance becomes greater. You can change these weights etc to alter the curve but in
essence it will be what it is and theres not much you can do about it. In order to help these some dizzy's run a vacuum advance which means
that when the engine is under extra load it moves diaphragms etc utilising a complicated system of levers and pulleys and again alters the advance
curve. Now the megajolt does this differently as YOU are able to attach a computer and tell it exactly what the advance should be at certain revs,
ie. with a dizzy you could have some control other idle advance say 10 degrees btdc, and max advance say 30 degrees. Where as the megajolt will break
it down as such:
<1000 rpm - 12 degrees
1000 rpm - 15
1500 rpm - 19
2000 rpm - 20
2500 rpm - 23
3000 rpm - 26
3500 rpm - 29
4000 rpm - 31
4500 rpm - 34 and so on
This gives the engine much better mid-range pull and smooths out the advance curve making it last much longer. You really need to see graphs to
compare, have a look at:
http://www.cate1.co.uk/megajolt/mapping.php
The megajolt can also use another input. Where the dizzy uses engine speed and position in cycle (with possible a crude vacuum advance) the magejolt
uses, engine speed, position in cycle and either a TPS or MAP. This makes the advance curve 3 dimensional. The TPS gives a reading of how much
throttle is being applied and the MAP is like the vaccum advance in that it senses engine load using pressure. Without getting to far into it they do
the same as the vacuum advance but as with RPM they can break things down into a much finer scale and so smooth out the curve much better. It also
means that you can still use a computer to tell it whatever you want it to do at a given setting. Suddenly ignition tables take on a horizontal plane
aswell, eg RPM against MAP or TPS = Ignition Advance.
This all makes for a more reliable, precise ignition system which also makes the car a bit more economical and will give it more torque and pull
better in the mid-range (such as when over taking) It wont give any more power than a well setup dizzy but it does make it easier to get the most
from the engine.
Megasquirt is a total package that also controls the fueling ie. is fuel injection rather than carbs. The new ones will also incorporate a megajolt
to control ignition also. The question comes down to whether you want to run carbs or throttle bodies and injection. You may get a slight bhp
increase with injection but the main advantages are with the accuracy associated with it (like with the megajolt).
Its a bit like using a PC and word processor in prefference to a type writer. They have the same final result but one is more user friendly and more
(accurate??)
For your R1 you can use either of them as they are applicable to any engine (pretty much - a strimmer might be pushing it a bit). If your R1 is
injected you'll need a megasquirt to run it all in which case get a new one which will control ignition aswell. If your engine is carb'd
you'll only need a megajolt to run the sparks...But of course you could always use the existing R1 electronics - just to confuse things!
Sorry for the length but I couldn't find a simple explanation anywhere so this can be it and we'll reffer people to it in future.... 
HTH. Oli.
Edit - Damn it Richard how fast do you type!
[Edited on 24/9/06 by oliwb]
If your not living life on the edge you're taking up too much room!
|
|
|
StevieB
|
| posted on 24/9/06 at 08:43 AM |
|
|
Cheers for that!
I'd looked briefly into the Megasquirt thing and got all excited about the prospect of making my own ECU. But I guess for a bnike engine, the
bike ECU is a nice, small and already set up box that plugs straight in.
As for the digidash, I didn't know if there was a (simple and well known) way of getting the Megasquirt display to show the additional info -
then I could have a cool display bespoke for my car.
I just wanted to be a bit different to the usual Acewell/R1 clocks that everyone else uses. Guess I'll just have to fall in line and fallow the
flock! 
Cheers
Steve
|
|
|
Hellfire
|
| posted on 24/9/06 at 08:03 PM |
|
|
Steve, if you've already got a fuel injected R1, whats wrong with the good old-fashioned Power Commander PCIII USB?
Phil
|
|
|
StevieB
|
| posted on 24/9/06 at 08:26 PM |
|
|
I haven't got anything under the bonnet yet - still a way off that!
I was doing a bit of a search on how to make a digi dash and was hoping that the Megasquirt would be the way forward in terms of having a computer
that reads revs etc.
I'm doing a lot of planning for my dash and I just don't want the run of the mill acetech or R1 clocks and savage switches. The problem
is that the alternatives are just as boring or very expensive.
Sounds like I'll just have to be a good sheep and follow the flock though 
|
|
|
