Trigger Wheels

[vlad01]

[vlad01]

[jarred]

I'll post high rpm testing with a scope soon, probably next week. With the chip manufacturer's reference wheel tooth geometry the sensor is good to 15 kHz (cycles/second) which translates to 900,000 rpm (cycles/minute) divided by triggers on the wheel, or 1,800,000 rpm/triggers with the 1:2 reduction in the distributor. But, with that tooth geometry I can only get 44 teeth in the distributor, or 22 triggers per crank rotation. So that makes for ~81,000 rpm bandwidth. Fast enough? 22 is obviously less than the standard 36-1 wheel, but I know people have run type 4 engines on the 8 holes in the backside of the flywheel. In discussion with the chip manufacturer there shouldn't be any problem in bumping that up to 26 to 32 per crank rev. The prototype only has 16 per crank rev because I CNC machined it with a 1/8" carbide bit. The final version will be water jet which can cut the small geometry.

The advance mechanism in a distributor only rotates the points plate. In my setup the trigger is mounted on the shaft so there wouldn't be any way to use the distributor's mechanical or vacuum advance. You wouldn't want to anyway, the advantage of programmable spark is the ability to nail the advance curve for maximum power.

[jarred]

Here's the Hall effect cap and trigger being tested

http://www.youtube.com/watch?v=VhYKuitVLIY&fea...4Xz9llpRWQ

[piledriver]

I'm running with 6 "teeth" (pressure plate bolt through holes) on the flywheel again: If you have a solid signal it's no issue except perhaps at cranking RPM, and not much then. (equivalent to 12 in the distributor)

You will be just fine.
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Current daily driver---73 Square, 1.8L T4, MS3+MS3X/sequential w/LS2 coils 80 miles/day.

[jarred]

I think I've run across your flywheel setup and considered doing it myself. But I own cars with both type 1 and 4 engines so I thought this could work for all the above. Yours is running fine? The 16 tooth was just a prototype, the smallest I can machine with given the end mill I had at the time. The Hall sensor can pick up 3 mm teeth before the pulse width begins to decrease. So, I'm going to try ~26 tooth (13 on crank equivalent) which is about as small as I care to machine. Could be water jet cut instead, but I was quoted a $200 minimum for about 12 pieces.

[piledriver]

I'd stay with 24 as MS2/3 "generic wheel" code requires even# crank teeth:
It would see 26 in the distributor as 13 on crank as noted, which would need custom wheel code.
I suspect other ecus have similar requirements...

Also, 24-1 would be seen as 12-1 and allow fallback if you lost the sync sensor.

I actually just switched back to the 6/1 setup to make room for an serp belt ac pulley I made from a Ford PS pump unit... I still prefer having the sensors out of harms way. If I ever pull the motor I'll drill 5 more holes to go 12-1.

Setting up the noise filters with a new sensor for my flywheel with an extra balance hole "visible" to the sensor is always interesting. (depends on the sensor)
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Current daily driver---73 Square, 1.8L T4, MS3+MS3X/sequential w/LS2 coils 80 miles/day.

[jarred]

Good point, 24-1 it is then. Are you using a VR or Hall effect sensor?

[piledriver]

[jarred]

Hall is definitely easiest to deal with and what I have been testing so far.

I've setup and run an engine on EDIS which is pretty straightforward. I was just looking over the Tuner Studio MS setup for generic trigger wheels. It seems that you can use any tooth count, not just 24-1, 36-1, etc. as long as the number divided by two is still an even number (even crank triggers). So for the purpose of attaining theoretically more accurate timing (if it matters) 28-1 would be preferred to 24-1 without any drawback. I ask because I'm re-machining the cap to be more like a distributor cap with it being located on the OD of the distributor rather than the ID. I originally used the ID to save on material cost but the ID being part of the casting and not a machined surface is likely to not be very dimensionally accurate... and the 009 distributor for example has been built in 3 countries in at least as many plants. Anyway, the larger cap means I can fit a larger wheel in so i figure I might as well do it.

[piledriver]

Above a certain tooth count, I suspect you are nuking rubble.

I'll be trying out a 16-1 wheel in a Mallory Unilite I have had gathering dust for >10 years.

It (or some variant) looks like a VERY easy way to go sequential. Only one sensor required.

You could do the same with a std Bosch distributor, you would probably want a better hall sensor (points location w/custom wheel above it ala compufire, only using a gear tooth sensor w/integral magnet)
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Current daily driver---73 Square, 1.8L T4, MS3+MS3X/sequential w/LS2 coils 80 miles/day.

[jarred]

Maybe you didn't look at my youtube vids? I have a hall sensor, machined wheel, and a machined cap that houses the hall sensor which mounts up using the stock b*tch clips. Takes about 3 minutes to install the hard parts and will fit many bosch distributors. Twisting the distributor as normal aligns the wheel with TDC. With a 24-1 wheel I tested it to 10,000 rpm and produces a perfect 5V digital signal on an oscilloscope. I'm just moving on to prototype #2 to fix a couple of things I didn't like in #1. This is a much cheaper solution than scrounging up a Mallory and it uses a modern hall effect sensor: internal magnet for field biasing, automatic gain adjustment, bandwidth to 40 kHz, automotive spec temperature range, zero speed tooth detection, and the ability to switch any voltage up to 24 volts.

[Mike Fisher]

jarred, what is your car/truck #990 at the Mt. Hood Rally?
_________________
https://imgur.com/user/FisherSquareback/posts
69 FI/AT square Daily Driver
66 sunroof,67,70,71,71,71AT,72,72AT,73 Parts
two 57 oval ragtops sold
'68 Karmann Ghia sold

Society is like stew. If you don't keep it stirred up you end up with a lot of scum on the top! - Russ_Wolfe/Edward Abbey

[jarred]

I co-own Hintz's old RX7 turbo. The frame/sheet metal that one of the differential mount bolts into is coming apart so we are probably out for the season.

[Mike Fisher]

Oh, well it sure looks like Fun!
_________________
https://imgur.com/user/FisherSquareback/posts
69 FI/AT square Daily Driver
66 sunroof,67,70,71,71,71AT,72,72AT,73 Parts
two 57 oval ragtops sold
'68 Karmann Ghia sold

Society is like stew. If you don't keep it stirred up you end up with a lot of scum on the top! - Russ_Wolfe/Edward Abbey

[piledriver]

[jarred]

Yeah, I think it's a lot easier than all the bracketry on other EDIS style installations. After I test it on a vehicle I'll probably start offering them for sale. What is STF?

[supersuk]

STF = Shop Talk Forums
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68 Fastback Build: http://www.thesamba.com/vw/forum/viewtopic.php?p=5396323#5396323

[ravivos]

Are these trigger wheels still available?
was thinking converting my ongoing build 2021cc T34 engine to MegaJolt... any thoughts?

Ravivos.

[supersuk]

Yes, still available. These trigger wheels will work with any system that needs a 36-1 trigger wheel.
_________________
68 Fastback Build: http://www.thesamba.com/vw/forum/viewtopic.php?p=5396323#5396323