Cam Sync Adaptor questions

[TeeJayHoward]

Thinking about ignition solutions in between work-things.

1) For something like the Clewett cam sync adaptor, can it be installed with the engine still in the car, or do you need to pull the engine in order to drill the camshaft for the M5 bolt?

2) For something like the distributor cam sync modification, I'm assuming that they install a toothed gear with a missing tooth and a sensor in the dizzy (which spins at half speed, right?) to detect camshaft location. Is this accurate?

3) For a DIY solution, why has nobody stuck a hall-effect sensor in the (bored out) #1 spark plug hole of the distributor cap pointing down at the rotor and disabled the weights? Wouldn't this give you a home signal just like the dizzy mod? Is the pulse length too long to be useful (bad resolution?) for EFI ignition systems or something? (And if that's the case, why not just thin the rotor blade to solve it?) It seems like a fairly obvious solution but I've not heard of it ever used anywhere, and I'd figure "Replace your rotor and cap and there's your cam position sensor with zero effort" would be a major selling point. There's gotta be an obvious issue here that I'm missing.

edit: Hell, for the DIY idea, why not just replace the rotor with a missing-tooth wheel instead of thinning the blade, and there you go. Why do you have to send your dizzy in to get worked on at all?

[stownsen914]

Will be curious what people have tried here. The synch/cam sensor position doesn't require the level of precision that the crank sensor does. As you say, it's more of a "home" signal that needs to occur within a range to distinguish the firing from non-firing stroke.

[spuggy]

Originally Posted by TeeJayHoward

1) For something like the Clewett cam sync adaptor, can it be installed with the engine still in the car,

Clewett's turbo scavenge pump/sync sensor can certainly be removed/replaced with the motor in the car.

Originally Posted by TeeJayHoward

or do you need to pull the engine in order to drill the camshaft for the M5 bolt?

Some cams already have drive holes; either for roll pins or tapped for bolts.

It'd be easier with the motor on a stand. But may well be enough room to do it, there's not a huge amount in the way.. Kind of a judgement call.

Originally Posted by TeeJayHoward

1)
Thinking about ignition solutions in between work-things.

Errrrr.... As I understand it, sync isn't used for ignition at all. It's only used if you want sequential (as opposed to batch) injection. Plenty of guys run without sync.
.

[TeeJayHoward]

Originally Posted by spuggy

Errrrr.... As I understand it, sync isn't used for ignition at all. It's only used if you want sequential (as opposed to batch) injection. Plenty of guys run without sync..

Huh... So how does the ECU know the difference between the compression and exhaust strokes? Does it just trigger the coil during both strokes and count on the mixture being leaned out too much during the exhaust stroke for it to matter?

[stownsen914]

Originally Posted by TeeJayHoward

Huh... So how does the ECU know the difference between the compression and exhaust strokes? Does it just trigger the coil during both strokes and count on the mixture being leaned out too much during the exhaust stroke for it to matter?

For some setups, yes. It's called wasted spark. Older setups like Electromotive that only run a crank sensor used wasted spark. It's a fine setup for ignition only.

[spuggy]

sync isn't used for ignition at all. It's only used if you want sequential

Dang it, should have written "necessary" instead of "used" in both places...

A modern ECU can certainly use the information if "knows" what stroke the cylinder is on. That's what cam sync is for.

Wasted spark works fine. The factory used batch injection with the 3.2 Motronic, I believe. For either, ECU only needs to "know" where TDC is (which it can get from the "missing teeth"), not what stroke the cylinder is on.

There are better ways to do it ~40 years on...

Sequential Fuel Injection
Sequential means that each injector for each cylinder is triggered only one time during the engine’s cycle. Typically the injector is triggered only during the intake stroke. True sequential injection requires the ECU to know not only where top dead center is, but also which half of the cycle the engine is on. TDC on a 4 stroke occurs 2 times during the cycle, once on compression and once on exhaust. MoTeC references all timing events that occur within the ECU, to Top Dead Center Compression. This generally requires an input on the engine’s camshaft to provide the ECU with a SYNC signal. Once the ECU is synched, injection timing can be optimized to provide the most efficient mixing of fuel and air into the cylinder. Control of injection timing can lead to increases in midrange torque while decreasing emissions and fuel consumption.

Semi-Sequential Fuel Injection
Semi-Sequential means that 2 or more cylinder’s injectors are triggered at the same time, but only 1 time during the engine’s cycle. This requires the ECU to be synched with the engine’s cycle.  Typically injection timing is retarded from the optimum timing point for full sequential by an angle which is equal to 1/2 the angle between 2 cylinders in crankshaft degrees. On a V8 Chevrolet, the injectors for cylinders 1 and 8 would be triggered at the same time. They would be triggered 45 degrees late for cylinder number 1 and 45 degrees early for cylinder number 8. Degrees between 1 and 8 = 90 ; 1/2 of 90 = 45. Semi-sequential allows optimization of injection timing which typically leads to increases in midrange torque and a reduction in fuel consumption for equivalent power compared which Batch fire.

...

Batch Fire
Batch fire means that 2 or more injectors are triggered at the same time once every crankshaft revolution. If the ECU is synched with the engine’s cycle, the injection timing can only be half optimized as fuel is injected both on the intake stroke and on the power stroke. Companion cylinders are paired in batch fire mode similar to wasted spark ignition modes. The advantage of batch firing is that the ECU needs only to know where TDC is. This means that a sync on the cam is not required. The disadvantage to batch firing is that the Injector Dead Time is doubled for the engine’s cycle. This leads to a decrease in fuel flow and typically requires a larger, less efficient injector to be used to make up for the loss of flow. On High Horsepower applications this means the idle quality will suffer tremendously

From http://www.motecusa.com/catalog/Section22.pdf