Custom Crank Angle Sensor setup

[Jason Broadhurst]

Let me get this straight, with a crank mounted chopper wheel it will only fire batch without a separate camshaft triggered input? Can't the ECU count the chopper teeth and know where it is in relation to any particular cylinder's position?

Next question, can the stock optical CAS be converted to something more reliable than optical? I guess not but the question stands.

1) The crank can be TDC for compression or exhaust stroke, and that is the problem with only a crank sensor. It will run wasted spark fine, and only semi sequential injection. Cam sensor can tell the ecu when it is TDC compression, for full sequential ing/inj

2) Not really, but there is nothing wrong with optical and like I said the resolution is pretty much the best I have seen on the nissans.

[Glenno]

Optical is fine as long as they can't get dirty.

[Billzilla]

I reckon it makes fuck all difference to use the cam vs the crank.

Blown alcohol and nitro engines have massive cylinder pressure and are mega sensitive to ignition timing and they run off a belt about half a metre long with no idlers..

There could be a bit of difference due to the number of cylinders - With four cylinders or fewer on an in-line engine the valve gear gets a hard time due to the cyclic loads as the valves open & close. With five or more, things smooth out. Those engines you mention have eight, so the valve gear would run relatively smoothly I suspect.
Something like a WRX with a four-pot boxer engine would have a pretty rough time. I think I remember reading something along those lines in a Racecar Engineering magazine years ago, by the Soob WRC team.

[260BC]

To get this straight.

For sequential spark there has to be a camshaft speed (half engine speed) sensor to signal TDC on each cylinder's firing stroke. That sensor may also be configured to signal engine RPM as well, or, a crank mounted sensor can be used to do the same thing.

[260BC]

Misc things.

On the cam belt 'varition' thing with the VG30DET, there was a bit of variation which showed up on the test thingo, at low RPM if I recall right. This was put down to the heavier valve springs being used and a stiffer 'racing' cam belt. No one is saying this 'variation' was sufficient to affect performance of that engine.

The single cam VG30ET I'm considering has an optical triggered distributor which is gear driven off one belt driven camshaft. Which sounds sloppy to me and I would like to get rid of the whole distributor seeing the VG30DET's six coil CDI system will be used.

No one seems to have a problem with still using the stock distributor's trigger system with a six coil setup but I'm looking at alternatives anyway. Seems like the only improvemnt which could be made is to use a cam and crank sensor combo as we have been discussing.

[Norbie]

For sequential spark there has to be a camshaft speed (half engine speed) sensor to signal TDC on each cylinder's firing stroke. That sensor may also be configured to signal engine RPM as well, or, a crank mounted sensor can be used to do the same thing.

Correct. With a single crank-mounted sensor you have to run waste-spark ignition, not that there's anything wrong with this? I run my 2JZ waste spark, Rz used to as well (not sure about his new Autronic setup) and he made silly power that way.

[260BC]

Are there any other benefits of waste spark? I just don't like the idea of the coils using more current and throwing more spark than they have to, even with a CDI system.

[KDog]

I wouldn't be concerned about running wasted spark. It is way better then running a dizzy adn associated crap.
Although if you can get a crank/cam trigger and not do it then you might as well. I don't know anything about your engine so can't give specific trigger plate options (but I've never had a problem with thin plates and hall effect sensors).

[GTSBoy]

But the thing to remember here is that if you go wasted spark because you're going without a cam speed CAS, then you also go to non-sequential injection.

Swings and roundabouts.

[260BC]

Oh well fuck wasted spark then. Thinking it may be possible to use a cam wheel for the TDC sensor setup, anyway, lots to think about.

[Billzilla]

Are there any other benefits of waste spark?

They're a good thing for boosted engines. No advantage on N/A engines.

[Norbie]

But the thing to remember here is that if you go wasted spark because you're going without a cam speed CAS, then you also go to non-sequential injection.

Does sequential injection have any benefit outside fuel economy and emissions? Once the engine is under a significant amount of load the benefits disappear because the injector has to be open much longer than the inlet valve is open.

[Billzilla]

Does sequential injection have any benefit outside fuel economy and emissions? Once the engine is under a significant amount of load the benefits disappear because the injector has to be open much longer than the inlet valve is open.

Depends how big the injectors are.

[GTSBoy]

Does sequential injection have any benefit outside fuel economy and emissions? Once the engine is under a significant amount of load the benefits disappear because the injector has to be open much longer than the inlet valve is open.

Depends how big the injectors are.

Yeah, what Bill said. If you have big ones, then they aren't open that much, and injection end point control becomes useful. You also get better idle and low rpm smoothness which is never to be sneezed at. Cars don't have to be cantankerous cunts of things to drive these days.