How is the fuel pump lobe phased on a stock camshaft? Is it the same for aftermarket? I'm doing a lot of reading about EFI and Ignition triggering and I'm wondering if I can make use of this wasted space once I convert...

_________________
Brooks

'72 Dart Swinger
'71 Plymouth 'Cuda

Cheap, Fast, Reliable
Pick 2!

You want to make use of the wasted space to do what exactly?

He won't be using a stock fuel pump, so he's thinking about using the pump lobe as a cam position sensor somehow. There are several EFI gurus on the site, they will chime in shortly I'm sure.

No idea on phasing. You or somebody would have to look at a cam and measure this. Why not use the distributor as a cam position sensor?

Lou

_________________
Home of Slant6-powered fun machines since 1988

That is definitely an option. I'd like to go COP or near the plug like the LS motors. Figured if I didn't need the dist, I could blank it off and give myself more room for wiring, fuel line, etc. Take out the dist and fuel pump and that side of the motor gets roomy quickly...

Are most people running off-the-shelf cams? If I have one ground, I'm thinking I could have the fuel pump lobe ground more aggressively, centered on TDC #1 and use a prox or other digital indicator to get a noise free signal...

Just thinking outloud...

_________________
Brooks

'72 Dart Swinger
'71 Plymouth 'Cuda

Cheap, Fast, Reliable
Pick 2!

Machine the lobe completly round and install a magnet(s) or some other trigger "monument", anywhere you want it.
The 1/2 speed of the cam will need to be accounted for. (install 3 magnets, 120 degrees apart? )
Timing chain & gear slop is always a consideration... that is why "crank triggering" is preferred.
DD

Forgive my ignorance...why 3? The speed of the cam IS the speed of the ignition sequence. I understand 1 for indexing or 6 for straight sequential triggering, but 3? Help me learn...

_________________
Brooks

'72 Dart Swinger
'71 Plymouth 'Cuda

Cheap, Fast, Reliable
Pick 2!

Good point... 6 is likely the better number, based on the cam's speed.
(I was thinking crankshift "trigger wheel", with 3 positions)
DD

It's an interesting thought, but I think Doc's point is significant... The slop in the timing chain will guarantee that your spark is not much more accurate fired from here than from a traditional distributor. As time goes by the firing point will become more erratic... Whereas a crank sensor guarantees a "dead on" trigger point no matter the age of the sprockets and chain.

- Mac

Agreed, but that same slop effects cam event timing. Which is more important, ignition timing related to cam or crank? I don't know, I'm just asking the question

_________________
Brooks

'72 Dart Swinger
'71 Plymouth 'Cuda

Cheap, Fast, Reliable
Pick 2!

don't know about all engines,, but the HD diesel engines I am familiar with have both a cam and a crank sensor,, the cam sensor is only active when starting the engine, as you can get piston position from a crank sensor, but you also need the cam sensor to determine if a particular piston is traveling down on a power stroke or down on an intake stroke. Once the crank and cam sensor are unified,, the ECU can figure out where the cam is based upon crank sensor readings, when that happens the info to the ECU from the cam sensor is disregarded and the crank position alone determines when to inject fuel. Crank position is used because, as Doc mentioned,, the cam position is subject to chain and / or gear lash errors.

Fit gear drive timing? Noisy but available.

regards,Rod

I would think that spark timing is more critical than cam timing, though both are obviously important. Valves open for a significant duration of time, but a spark fires in a critical instant of time.

- Mac

The cam position isn't used for fine control. It's there to determine which cylinder to fire or fuel 1/6, 2/5 or 3/4 since they happen at the same measured crank position.

_________________
Joshua

I'd think you'd want 3 triggers on the crank, then 1 trigger on the cam to determine when cylinder 1 is to be fired.

The cam trigger would have some lead so that the ECU would know that the next crank trigger is #1 cylinder.

The ECU then counts.............

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes