Megajolt Rev limit
Turbo Mini Forums

Does anyone have any ideas on how so set up a rev limit system using the MJ? I mean hard cut out; from what I gather the rev cut output on the ECU is only a trigger for a rev cut system. Any ideas on what you could use? How hard would it be to build a relay with earth and live, rev cut signal from the ECU, +ve from the EDIS in and +ve out to the coil (which is cut when the trigger comes live)? Is it obvious I have no electronics experiance?! What does everyone else use or does everyone else just use the soft cut?

I just use the soft cut currently at 6500rpm which retards the ignition if you go over the set rpm, You can most definitely feel it and I just back off (or more likely---change gear)! when I feel it. I guess I would only bother with a hard cut if I was really up against the mechanical limits of the engine..

website:- http://www.terryhunt.co.uk

To be honest why do you really need a rev limiter, on a road car you should be able to regulate your right foot to achieve this!

An idea I did have for the megajolt was an overboost cut, this would use one of the user config outputs to cut the ignition totally in the event of overboost, useful if ever a hose to the actuator split etc.

A hard cut is probably of limited use but I mised a gear once and I was able to go past my soft cut quiet easily. I was thinking more for sudden loss of traction or missed gears. The overboost cut is a great idea though!

I have done this for the megasquirt and edis. It works OK as a last resort on the hill climber. The drawings I did are in work I will post them up tomorrow if nobody else does some. I should be able to give you some part numbers too.

Ben

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

I was thinking about altering my map so at high boost values (which you should not see) set the timing to 0 degrees so it will at least soft cut. Also atmospheric values above 4000 revs i set to 26 degrees in case something went wrong with the MJ map pipe when on boost.

-MINI CLUBMAN 1380 TURBO-

Good thinking T3 .... will do that sort of thing to mine too

Every day is a school day ...........

How fast and how expensive ...... the same question...

Rev limiter on EDIS

Below are two circuits showing two ways of rev limiting when using edis. In both cases I am planning on using the second shift light output from the MS unless I can think of something better.



1. This circuit simply cuts the +ve feed to the coil pack. This could be quite harsh when it comes in, but it will stop over reving. If it fails to work you will lose the rev limiter, but the engine will run fine.



2. This second circuit only cuts sparks to one of the coils. This will be less harsh and should work OK. Again this is fail safe.




Components

I use a relay from Maplin. It is a 6v/6A relay. Part number: RP68Y

http://www.maplin.co.uk/Module.aspx?TabID=...No=2512&doy=7m9

The freewheel diode is any old diode.

Where the drawing says MS just use your configurable output from MS or megajolt. I have tested this on my mini, but not yet on the turbo.

Ben

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Ah excelent! This will give me a nice project to work on. Thanks dude!

You realize that when you cut power to the coil(s) you potentially generate a spark which is not timed correctly with all the consequences of such a thing. I don't know how many people have used such a rev limit method and it may not be an issue but I wouldn't feel comfortable with that especially with a boosted engine.

Jean

http://www.jbperf.com/

Cutting the positive (the first circuit) will not have this problem I don't think. Good point though. Unfortunately with the EDIS system you are stuck with a circuit like this as you can't control the coil control in the edis its self.

When we use this we use it as a last effort. The retard revlimit is the first limit.

Ben

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

Actually thinking about it I have got another circuit that will work and not cause any sparks. I was being a bit dim.

I will draw it up on monday and post it.

Ben

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

OK, here we go. The new improved circuit. Don't know why I didn't think of this in the first place. I reckon this should work without causing any out of time sparks.



Any comments welcome.

Ben

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.