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Using fuel pump cam lobe for a trigger

bobxyz

Board Member
Joined
Aug 29, 2014
Location
Boulder CO
I forget where I saw it, but someone who did this ground down the fuel pump lobe to make it more pointy. I don't know if it would matter since the main timing is off the crank toothed wheel.

That DIY sensor is a Cherry Semiconductor, now ZF electronics, GS100502. They seem to be on backorder most places, but are in the $45 range when available.

I also remember that someone said to reinforce, shrinkwrap over, or silicon encase, the wires going into the sensor for better reliability.
 

MikeSr.

What, me worry?
300+ Club
Joined
May 27, 2003
Location
Acworth, Ga. USA
I am going to use a Microsquirt- so I am limited to 2 injector channels. I could run COP ignition.
I thought about using a CAS , which I still may do- I tend to overthink things lol.
 

bobxyz

Board Member
Joined
Aug 29, 2014
Location
Boulder CO
I am going to use a Microsquirt- so I am limited to 2 injector channels. I could run COP ignition.
I thought about using a CAS , which I still may do- I tend to overthink things lol.
Buried in the MicroSquirt documentation is a critical table that shows the supported uses for the multi-function optional feature pins - there's 7 of them for MicroSquirt, and the table is not quite correct - see: link

Without a CAS, you could use 4 pins for SPK A,B,C,D and run wasted-COP mode ignition (where each COP fires twice per engine cycle), or if you're running true logic-level coils/cops, you can wire them in pairs (AC/BD) and use just 2 pins in wasted spark mode. The advantage of this is that it frees up the SPK C,D (mis-documented as B,C) pins for other uses.

For basic installs, you won't run out of pins, but if you want some extra features and some warning lights, you may be tight on pins.
 

bobxyz

Board Member
Joined
Aug 29, 2014
Location
Boulder CO
With just a factory 60-2 crank wheel, you can do:
- semi-sequential injection (paired 1+4/2+3, setup for 2 squirts/cycle)
- wasted spark ignition with a dual power-stage and a dual-coil, using 2 SPK outputs, or
- wasted COP ignition with logic-level COPs and 2 SPK outputs

If you add a once-around cam sensor (either a hall sensor + fuel pump lobe, or hall-sensor through the valve cover, or a LH2.2 distributor with 3 of 4 vanes removed, or that VW sensor), you can do:
- full sequential ignition using 4 logic-level COPs, and 4 SPK outputs
- you're still limited to semi-sequential injection due to only 2 MicroSquirt INJ outputs

With a DSM CAS, you can do the same as immediately above.

Remember, there were millions of cars made that used batch-fire injection and either a distributor or dual-coil wasted spark, so it's a pretty reasonable setup.
 

bobxyz

Board Member
Joined
Aug 29, 2014
Location
Boulder CO
No, there's way too much speed variation, especially during cranking, to time 4 sparks accurately enough off of a single cam trigger.
 

mickeys240

Member
Joined
Jan 31, 2005
Location
Portland/Washington
Yes. You have to know Swedish.
https://www.overboostracing.se/

His site is in english, and he does have a Video about it. I think he spoke about it in ONE english video. HE has done it himself and talks about how to set the Pick up for it.

I called him and left him a Message and I'll get the specifics on it soon. Its about 4PM in Sweden, so his either closing up shop or getting ready to go home for the DAy.

I know that he spoke about that he disagrees with using a timing wheel on the front of the engine. I'd take his word on it being okay for use for timing the engine.
https://www.youtube.com/watch?v=mosH-RdeWsI
 

culberro

Ronald Culberbone III
Joined
Feb 10, 2010
Location
Redmond, OR
How about using a 4 slot hall trigger?

That should work just fine. That's how the LH 2.2 (and earlier) cars did ignition.
Edit: this will only work if you use a missing tooth for a reference, or use a distributor for spark and run batch injection.

If you want to run sequential, you will need a missing tooth at cam speed. If you want to run semi-sequential batch fire, you can get by with 2 triggers per cam rotation. But the starting will be a struggle to get sorted as the speed with cranking varies a lot (as bobxyz mentioned). This is how a lot of pertronix systems work on motorcycles, one pickup per cylinder ran at cam speed.
 
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mikep

The MP
Joined
May 24, 2003
Location
38? 27' N 75? 29' W
The aux shafts with rough cast blank where the pump lobe goes could possibly be modified to give more teeth/gaps, but unless you go with more than 4 (and do it really precisely), I don't know how beneficial it would be.
Mind you, I am an absolute microsquirt idiot.
 

bobxyz

Board Member
Joined
Aug 29, 2014
Location
Boulder CO
Years ago, Mario at thedubshop.com was trying to make a version of his cam sync sensor (similar to the cbperformance AC VW one) that included a tiny toothed disk and optical sensor. I don't know if he ever finished this.
 
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