Why not?: Flywheel as crank position sensor

[peejay]

They didn't see the advent of home chip burning.

I am fairly certain that any version of Motronic is thoroughly hacked by now. For sure the Motronic used on 5 cyl Audis is.

One of my pet projects is grafting a 60-2 wheel on an old Audi mill so I can use a M4.4 system from a late 1990s Volvo. Because it is OBD-II, tuning changes can be made by reflashing through the DLC, rather than burning chips. There aren't too many other options for controlling a five cylinder engine, anyway. (I've also been looking into the Atlas 5 cylinder engine, which also uses a 60-2 crankwheel, but tuning GM PCMs designed around variable cam timing is not particularly fun, even before thinking about hammering it to work with a smaller, more turbocharged engine)

Volvo put a 60-2 shutter wheel on the backside of the flywheel. VWAG put a 60-2 on the back of the flywheel on some models, and in a VERY interesting move, they have a 60-2 rear main seal on some models. Works a lot like the wheel speed sensors built into wheel bearings on some cars with ABS. External sensor picks up magnets embedded in the seal.

[MadBill]

the cam position signal is required to tell the ECU whether the piston at top dead center is pooooshing out exhaust or compressing the fresh mixture (when going with sequential injection). if you have a 4 cylinder engine, you don't need the cam position signal, but you sure do with an eight.

Err... the cam turns at half crankshaft speed on any four stroke, so a crank sensor can't tell if a particular cylinder is on the compression or the exhaust stroke.

[arlancam509]

the cam position signal is required to tell the ECU whether the piston at top dead center is pooooshing out exhaust or compressing the fresh mixture (when going with sequential injection). if you have a 4 cylinder engine, you don't need the cam position signal, but you sure do with an eight.

Err... the cam turns at half crankshaft speed on any four stroke, so a crank sensor can't tell if a particular cylinder is on the compression or the exhaust stroke.

yes, you are correct. what you will end up with is an out of phase injector shot - either at a closed intake valve or an open intake valve. it will still run, but one scenario will cool the intake valve.

[MadBill]

FWIW, many years ago a friend of mine was dynoing a 495" BBC with Lucas mechanical timed injection. Part way through the session it was discovered that the injection was 360° out of phase. He said that when corrected it had no effect on power but the idle quality improved. (Throttle response, etc. could well have suffered...)

[Leftcoaster]

VWAG put a 60-2 on the back of the flywheel on some models, and in a VERY interesting move, they have a 60-2 rear main seal on some models. Works a lot like the wheel speed sensors built into wheel bearings on some cars with ABS. External sensor picks up magnets embedded in the seal.

Peejay, any idea which VAG engines utilise this rear main seal 60-2 sensor, part numbers, & how reliable they are? Thanks

[HiPer Express]

the cam position signal is required to tell the ECU whether the piston at top dead center is pooooshing out exhaust or compressing the fresh mixture (when going with sequential injection). if you have a 4 cylinder engine, you don't need the cam position signal, but you sure do with an eight.

Err... the cam turns at half crankshaft speed on any four stroke, so a crank sensor can't tell if a particular cylinder is on the compression or the exhaust stroke.

It can, some new diesel engines dont have cam sensor, crank sensor just detects acceleration, that way it knows if injector is firing on the compression stroke.

[Brian P]

That strategy isn't limited to diesel engines. I have a fuel-injected single cylinder Honda motorcycle engine, and a two-cylinder 180-degree-crankshaft Yamaha motorcycle engine (thus having an uneven firing order), which only have a crank sensor. Any engine with an uneven firing pattern - V-twins, Ducati "twin pulse" V-fours, etc - this strategy is possible. It is also possible with a three-cylinder even-firing in-line engine.

[n2xlr8n]

FWIW, many years ago a friend of mine was dynoing a 495" BBC with Lucas mechanical timed injection. Part way through the session it was discovered that the injection was 360° out of phase. He said that when corrected it had no effect on power but the idle quality improved. (Throttle response, etc. could well have suffered...)

Kinda like my batch-fired 2200cc / cyl injected 4 cylinder.

Not ideal idle.

[peejay]

VWAG put a 60-2 on the back of the flywheel on some models, and in a VERY interesting move, they have a 60-2 rear main seal on some models. Works a lot like the wheel speed sensors built into wheel bearings on some cars with ABS. External sensor picks up magnets embedded in the seal.

Peejay, any idea which VAG engines utilise this rear main seal 60-2 sensor, part numbers, & how reliable they are? Thanks

It's mainly used on newer engines that used the old timing-belted watercooled block.

As far as I know, it's used on a small handful of 2.0 TDIs in North America. (Only two or three years) Beyond that, you need to contact Marc at EFI Express, as he sells the seal and sensor and wiring, which is suitable to convert an old watercooled VW four or Audi five.

From what I have been able to gather, the gasoline and Diesel are different part numbers because they time the missing teeth differently. Either way if you buy the parts from Marc or try to source them locally from whatever year of TDI, it comes out to about $350-400.

Edit: EFI Express link

[peejay]

That strategy isn't limited to diesel engines. I have a fuel-injected single cylinder Honda motorcycle engine, and a two-cylinder 180-degree-crankshaft Yamaha motorcycle engine (thus having an uneven firing order), which only have a crank sensor. Any engine with an uneven firing pattern - V-twins, Ducati "twin pulse" V-fours, etc - this strategy is possible. It is also possible with a three-cylinder even-firing in-line engine.

Saturn used very specific spark plug wire lengths on a wasted spark coil, and a little bit of sleuthy circuitry, to determine if cylinder #1 (long plug wire) or cylinder #4 (short plug wire) was firing.

It worked extremely well except when it didn't. We replaced a lot of wires and coils at the warranty level because they didn't really tolerate corrosion. Oddly enough it seemed like only some cars would set a "cam sensor" fault... others would easily go their whole lifes with the kind of abuse a $12k car could get, and never have an issue.

[Leftcoaster]

Thanks

[j-c-c]

That strategy isn't limited to diesel engines. I have a fuel-injected single cylinder Honda motorcycle engine, and a two-cylinder 180-degree-crankshaft Yamaha motorcycle engine (thus having an uneven firing order), which only have a crank sensor. Any engine with an uneven firing pattern - V-twins, Ducati "twin pulse" V-fours, etc - this strategy is possible. It is also possible with a three-cylinder even-firing in-line engine.

Saturn used very specific spark plug wire lengths on a wasted spark coil, and a little bit of sleuthy circuitry, to determine if cylinder #1 (long plug wire) or cylinder #4 (short plug wire) was firing.

It worked extremely well except when it didn't. We replaced a lot of wires and coils at the warranty level because they didn't really tolerate corrosion. Oddly enough it seemed like only some cars would set a "cam sensor" fault... others would easily go their whole lifes with the kind of abuse a $12k car could get, and never have an issue.

Wait, the length of the wire was a factor with ignition timing?

Are you sure?

I have never heard this before

[peejay]

That strategy isn't limited to diesel engines. I have a fuel-injected single cylinder Honda motorcycle engine, and a two-cylinder 180-degree-crankshaft Yamaha motorcycle engine (thus having an uneven firing order), which only have a crank sensor. Any engine with an uneven firing pattern - V-twins, Ducati "twin pulse" V-fours, etc - this strategy is possible. It is also possible with a three-cylinder even-firing in-line engine.

Saturn used very specific spark plug wire lengths on a wasted spark coil, and a little bit of sleuthy circuitry, to determine if cylinder #1 (long plug wire) or cylinder #4 (short plug wire) was firing.

It worked extremely well except when it didn't. We replaced a lot of wires and coils at the warranty level because they didn't really tolerate corrosion. Oddly enough it seemed like only some cars would set a "cam sensor" fault... others would easily go their whole lifes with the kind of abuse a $12k car could get, and never have an issue.

Wait, the length of the wire was a factor with ignition timing?

Are you sure?

I have never heard this before

Not for ignition timing, for cam position sensing, in the sense of knowing where the engine was in the firing order.

On a typical four cylinder, 1 and 4 share TDC. What Saturn's engineers devised was a way to tell which cylinder was at TDC firing by monitoring the primary side of the (wasted-spark) coil, thanks to the fact that the #1 plug wire was about three times as long as #4 due to where they had mounted the coil packs. So, they were able to have sequential injection, and later on misfire detection with accurate cylinder identification, without a cam sensor.

The almost requirement of any engine nowadays to have variable cam timing makes this little bit of tech moot, but in 1991 it was a neat trick. All Saturn engines (meaning SATURN engines, not Ecotecs or SAAB or Honda V6s) never had cam sensors, they just monitored the ignition module.

[jred]

some of the guys over at shoptalkforums using megasquirt are using holes drilled in the flywheel for a crank sensor,,

[makin chips]

They didn't see the advent of home chip burning.

I am fairly certain that any version of Motronic is thoroughly hacked by now. For sure the Motronic used on 5 cyl Audis is.

One of my pet projects is grafting a 60-2 wheel on an old Audi mill so I can use a M4.4 system from a late 1990s Volvo. Because it is OBD-II, tuning changes can be made by reflashing through the DLC, rather than burning chips. There aren't too many other options for controlling a five cylinder engine, anyway. (I've also been looking into the Atlas 5 cylinder engine, which also uses a 60-2 crankwheel, but tuning GM PCMs designed around variable cam timing is not particularly fun, even before thinking about hammering it to work with a smaller, more turbocharged engine)

Volvo put a 60-2 shutter wheel on the backside of the flywheel. VWAG put a 60-2 on the back of the flywheel on some models, and in a VERY interesting move, they have a 60-2 rear main seal on some models. Works a lot like the wheel speed sensors built into wheel bearings on some cars with ABS. External sensor picks up magnets embedded in the seal.

What about the e67(i think. Might be e38) pcm in the 3.7L 5 cyl Colorado? It's used in everything up to the 6.2L V8's. What about that one?

I'm guessing that's the Atlas 5 you're referring to. Duh. Not sure how I missed that the first 3 times lol.