Trigger wheel position
Turbo Mini Forums

OK, the search button police can have me because I'm asking the totally obvious....

But I need a sanity check, and can't find the obvious either here on on the Megasquirt site....


I've just modified a metro timing cover to give adequate clearance for the fan and am about to make a bracket for the VR sensor and weld the trigger wheel on the BACK of the pulley (spigot machined ready), BUT,

For Megasquirt, is the gap (missing tooth) at TDC or 90 degrees (I think I'm getting confused with megajolt/EDIS).

And is the best trigger at falling edge (last tooth before gap) or leading edge (first tooth after gap)....


I want to put the sensor about where the old funny square holder (which I've removed) went.

Rod.

And yes, the pulley is damaged, some moron before me obviously hit it to get it off, but it's just for the trial :):):)

Edited by Rod S on 14th May, 2008.

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

The "normal" method is to cut the missing tooth so that at TDC it is at 12 O'clock. Then put the sensor at 9 0'clock.

So as long as you put the missing tooth 90 degrees after the sensor you should have no problem.

You will need to set leading or falling edge in the software depending on your ignition setup.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Right, so it is still 90 degrees even with Megasquirt, I had a mindset that the 90 degrees was only for Megajolt.

Setting the leading or trailing edge in the sofware I can see, but the Megasquirt site doesn't make clear which is actually best....

Which are you using (mine will be similar to yours, VB921s (actually newer equivilants) to a coilpack).

Rod.

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

Hi,
90 degrees is best as it gives the ECU more time to calculate what it's got to do.
If you run 45 degrees advance on light load, then the ECU only has the 45 degrees before to calculate it.
Cheers,
Gavin :)

VEMs Authorised Installer / Re-seller. K head kits now available!

WB/EGT gauges. Click here for customers write-up

Visit www.doyouneedabrain.co.uk

My Mini build diary

This is the part of the MS2/Extra manual that explains.

http://www.msextra.com/ms2extra/MS2-Extra_Miss_Tooth.htm

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Thanks Paul,

I don't know why I couldn't find that for myself... maybe weldng or paint fumes.....

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

Right,

Mocked it up on the MG (N/A) engine that's going in first and looks like this.



I will weld a very simple plate type bracket to the timing cover which will be more than adequte for the positioning of the pickup.

I seem to be doing it different to most, so am I missing something that will cause me problems later ???

Rod.

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

Access to the sensor will be difficult. Also may foul the bottom hose.

Is there any particular reason why you do not want to fit it in the conventional manner?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

It may be just my warped mind, but it seems more logical to put it as close to the engine as possible and at the back to protect it from road muck and spray.

If I'm right, access won't be an issue as it wont fail !!!

Good point about the bottom hose, I'll mock that up tomorrow and see.

The real reason though is that I want, ultimately, to mount the trigger wheel on the inner boss of the pulley (ie, the bit that isn't rubber mounted for the damping) and I think I might be able to use that plate thing Leyland/Rover fitted on the back of the later pulleys, but only if I can get the whole setup really close in towards the engine.

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

OK,

Checked out paul's worry about bottom hose.
Nothing that shortening the hose wouldn't cure.
So bent up a few bits of metal

Bit of spot welding and TIG,
Trial without hose
Then hose shortened slightly

I'm quite happy with it, no offence to those who have gone the "conventional" way (trigger wheel or machined pulley outside the fan belt) but this suits me better.

Rod.

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

Well done.

Good to see other ways of doing things. Certainly the simplest mount I've seen.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

That is a convinient point for mountng the bracket!

good stuff!

Am i missing somthing or is this not wrong. If it 90 tdc then this is 180 out isnt it.

Its prob me thats just thick

Rick

Edited by Rob H on 15th May, 2008.

Yes,

My original post was because I couldn't remeber if it was 0 degrees or 90 degrees but the point is to set the trigger wheel relative to wherever the pickup is sited.

I chose to mount the pickup here because I think it's a better place for me so my trigger wheel will be attached to the back of the pulley 180 degrees different to the majority, but it will still pass my pickup 90 degrees BTDC.

Rod.

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

If you dont get the sensor 'exactly' at 90 degrees. Is this the end of the world? Or can it be adjusted on the pc once in place?

Cheers,

Ben.

Build Thread Click Here

In Megasquirt you can set an "offset" once it's up and running, I would guess Megajolt is similar.

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

Ahh rite cool, because ive put the engine in and now am fitting the sensor, its going to make it harder to get it exactly 90 degrees thats all.

Cheers,

Ben.

Build Thread Click Here