Another RV8 "thought experiment"

[Chassis 33]

Right, moving on from my what if I use an electric oil pump idea, is it possible to use the cam sensor on the later dizzy-less timing covers to drive the "crank sensor" with an aftermarket ECU?

As I understand it, the cam wheel has 4 different length markers for the sensor to pick up on GEMS and Thor systems so the OEM ECU can figure out which cylinder is actually firing. Could this wheel be replace with an equally spaced setup. The cam operates at half engine speed as we all know, so if the wheel had two missing teeth 180deg apart the ECU would know no difference right?

So that's the theory, what are the practical issues with this?
Regards
Iain

[tribbles]

IIRC the crankshaft spins at twice the speed of the camshaft.

ETA: Just read you'd already taken that into consideration... Ho hum. Shouldn't have had those beers earlier!

ETA2: You'd need to balance it, and also the number of teeth would probably be fewer (might confuse it)...

Edited by tribbles on Wednesday 25th June 21:19

Edited by tribbles on Wednesday 25th June 21:21

[stevieturbo]

I would say a cam only trigger setup should work fine, as long as the ecu can understand it.

Some are more versatile than others.

It aint that difficult to throw a trigger onto the crank pulley though.

[dilbert]

The ECU is pretty "fast". I'd be thinking about stretch in cambelts or chains. Since it's the piston position that you're trying to time against, I'd go with the crankshaft.
If the camshaft is geared, which I doubt, perhaps you'd be OK. As it goes you might be anyhow, but why risk the pain.
I don't know what the timing window actually is at peak revs, in terms of milliseconds, but I'd bet it's not a lot.

Edited by dilbert on Thursday 26th June 16:32

[Chassis 33]

Good point re the cam chain stretching and throwing timing off. Hadn't thought of that! That's another great idea dismissed then!
Regards
Iain

[GreenV8S]

Unless you going for sequential injection you don't need to know the cam phase - it's a heck of a lot easier imo to put a toothed wheel on the crank.

[stevieturbo]

GreenV8S said:

Unless you going for sequential injection you don't need to know the cam phase - it's a heck of a lot easier imo to put a toothed wheel on the crank.

Agreed..


FWIW.

Lots of Toyotas, Hondas, Nissans all use a camshaft based sensor for ecu triggering on a lot of cars.

[CNHSS1]

as Stevieturbo says al ot of nissans use the cam angle sensor CAS system. i know a few guys that run the emerald with a cam trigger on 16v turbo'd nissan engines. VEMS actually make thin stainless foils cam discs that replace the std nissan jobbie inside the distributor so no need to make one of your own. i believe other OEM copy distrib discs for other engine types/makes were under development from VEMS too

[stevieturbo]

Although the OE cars that use a cam based trigger....

Tend to have dual triggers inside. One for rotational speed and the other for no1 tdc position reference.

Although I dont see why a single trigger wheel with a missing tooth shouldnt work.

[CNHSS1]

yep nissans use 360 mini slots on one 'track' and a second track with 4 slots at 90deg, one of which is larger than the other 3 to denote TDC. the VEMS foil disc just utilises a std 36-1 trigger pattern and ignores the second pickup
will see if i can find a pic of the std setup

Edited by CNHSS1 on Friday 27th June 17:03

[dnb]

The VEMS Nissan trigger disc I have is 24 slots + single sync 1 pulse. So therefore it doesn't ignore the second trigger.

I admit there were a number of versions...

[350Matt]

The first emerald set-up I ran for about 3 years triggered off the dizzy signal so only 4 pulses / rpm this worked generally well.
The limitation of it was all the slack in the drive up to the dizzy meant a less than stable rpm signal at idle ( + /- 50Rpm) and potentially you can't run the ignition timing as accurately as you can with a crank trigger so you can't push the limits as close

In summary - put a crank trigger wheel on it

Matt