I will need to upgrade the EFI system for my LS 300, I'll probably go with a coil on plug system, but more importantly I'm wondering what the difference is between a tonewheel and just taking the signal from the reluctor wheel and hall effect sensor in the stock distributor.
Is the resolution better with a tone wheel? Do you not need to worry about the distributor rotating?
Educate me please.
Unless there was a pretty special distributor, yes, the high number toothed tone wheel gives you much better resolution and accuracy.
And there should not be a problem with the distributor just spinning and doing nothing. Although, I would look to see if anything is driven off of it- as a blanking plate over the open hole looks better.
Is the oil pump driven by the distributor? Could still cut down the distributor if so.
So going with a tone wheel, what do I need to know to build one? Or should I just wait till I get the Megasquirt system (or whatever I'm going to use) and build based on that?
In reply to Mr_Asa :
Different systems will probably support different tonewheel configurations, and likely have something that's a sort of default, or a few options that it's prepared to use just by selecting something in the config.
So I'd choose a system first. There are possibly some that are so common everything supports them, but that's beyond me.
Mr_Asa said:So going with a tone wheel, what do I need to know to build one? Or should I just wait till I get the Megasquirt system (or whatever I'm going to use) and build based on that?
Unless you have access to a laser cutter, buy one.
If you REALLY want to make one, the teeth are evenly cut, and the missing tooth references a time before TDC of cyl 1. It's 90deg BTDC of 1 for a 4 cyl, 60 for 6, and 45 for 8.
What I've seen for MS, it looked like you could tell it the tone wheel.
I'm mostly aware of 2- the 36-1 tooth Ford, and the 60-2 (two are missing to make sure you see it) for Bosch. I know that there are others, but those are the two I've worked with.
Dumb-ish question, does the 300 share any front end dimensions with the small block Ford?
Somewhere I'd read that a 3.8 harmonic damper is the same dimensionally as a 5.0-5.8 but neutral balance, and a lot of them have a 36-1 built in.
You'd need to convert the rest of your accessory drive to multirib belt if this is a possible route, but this should be simple compared to slicing and splicing a cylinder head.
Alternately, you could put a small trigger wheel on the distributor. I'm 99% certain that MS can be configured to read a wheel that runs at cam speed.
Pete. (l33t FS) said:Dumb-ish question, does the 300 share any front end dimensions with the small block Ford?
Somewhere I'd read that a 3.8 harmonic damper is the same dimensionally as a 5.0-5.8 but neutral balance, and a lot of them have a 36-1 built in.
You'd need to convert the rest of your accessory drive to multirib belt if this is a possible route, but this should be simple compared to slicing and splicing a cylinder head.
Alternately, you could put a small trigger wheel on the distributor. I'm 99% certain that MS can be configured to read a wheel that runs at cam speed.
I wasn't sure, so I went looking. The '96 4.9L had a 3-tooth wheel that can be swapped out fairly simply. I'm searching for a part number for it in particular but I found the balancer part number. Ford F6UZ6316A
In reply to Mr_Asa :
That, by itself, would be enough for MS to control spark through a distributor and batch-fire fuel, which is all you're going to be able to do anyway unless you rig up a cam position sensor.
Well, I think you might be able to do waste spark ignition if you had a missing tooth wheel.
In reply to Pete. (l33t FS) :
Hrm. How much resolution does the cam position sensor need before I need a full tone wheel?
In reply to Mr_Asa :
If you are using it in conjunction with a crank trigger, all it does is let the computer determine if it is on 153 or 624. It can be a half moon, or it can be just a single tooth, like for instance a EFI distributor with five of the reluctor's teeth ground away. You will still need to have a trigger wheel on the crank that has a missing tooth, so the computer knows where the engine is in the firing order. I don't THINK that it's able to determine that from a cam tooth.
Ok, enough for more, better questions after research. Thanks.
Pete. (l33t FS) said:Dumb-ish question, does the 300 share any front end dimensions with the small block Ford?
Somewhere I'd read that a 3.8 harmonic damper is the same dimensionally as a 5.0-5.8 but neutral balance, and a lot of them have a 36-1 built in.
You'd need to convert the rest of your accessory drive to multirib belt if this is a possible route, but this should be simple compared to slicing and splicing a cylinder head.
Alternately, you could put a small trigger wheel on the distributor. I'm 99% certain that MS can be configured to read a wheel that runs at cam speed.
More looking, the 302 has the same snout dimensions as the 300, but the hub length is 1/8" longer.
When it comes to tone wheels, more teeth are better up to a point.
Don't go less than 24. The ones Bosch uses are 60. What does Megasquirt recommend?
As for the cam/distributor sensor, a single tooth is fine. All that is needed is some way to synchronize the crank tone wheel cycle to the compression cycle.
It will depend a bit also on the MS version, on ms1 v2.2 board high count tooth wheels and VR sensor inputs are some significant modifications. On a ms2 and onward v3, 3.57, microsquirt, ms3 pro any of the high tooth count wheels 36-1, 60-2 all work just fine. The only thing that is a little tricky is the Audi tri-tach (944, UrS4, etc) and likely out of scope.
The "best" setup is the highest crank count that you can read without sync loss (rpm dependent usually) and a single tooth cam. If you have timing chains with no belt stretch possible then a cam only setup is nearly as good but you want plenty of main pulses 12-1 would be my min. The "fast start" cam sensor features aren't used on MS and not an advantage with how the code is written at the moment.
I have to say the most common and nearly universal is 36-1 crank and 1 pulse cam.
The difference in tooth count becomes apparent at higher power levels where the tuning window is narrower.
A higher pulse count gives the ECU a better picture of what the crank is doing.
So a 36 tooth crank signal provides data at a rate several orders of magnitude over a points or per-cylinder signal
These folks have you pretty well covered, but I will say this from my analog experience. If I have the option of crank trigger or dizzy trigger, I always take the crank. I don't care how new the timing chain is, it has play. That frustrating engineering achilles heel called tolerance. You might also be surprised at how much flex, tolerance, and harmonics are in the cam itself. I've watched sparks on a timing light bounce all around 3-4 degrees
Many of the major manufacturers realized this and put the distributor up front before all the harmonics could be induced (putting the timing gear adjacent to the chain). But until you get tolerance in the drive sprocket, the chain pins or rollers, the cam sprocket, and the teeth between the distributor and drive gear, there is plenty of accuracy lost in when the dizzy trigger actually signals.
A reluctor on the crank itself has zero tolerance. The only possible tolerance is from crankshaft deflection and there is nothing you can do about that. When you bolt a reluctor to the crank, when it points north, it's north. Not 2 degrees north east.. I say go with a crank trigger.
In reply to Curtis73 (Forum Supporter) :
300s have a gear drive for the cam, my friend. Might get some backlash in that, especially going crank-cam-dizzy, but I wouldn't expect it to be that bad.
In reply to Mr_Asa :
You still run into twist issues as everything gets noodly. Probably not as big a problem on a 300 as, say, a small block Chevy, but it exists.
There are also weirdnesses created by oil pump harmonics, and people like belt drives because gear drives cause too much mechanical noise in the distributor and valvetrain.
Mr_Asa said:In reply to Curtis73 (Forum Supporter) :
300s have a gear drive for the cam, my friend. Might get some backlash in that, especially going crank-cam-dizzy, but I wouldn't expect it to be that bad.
True, but you might be shocked at how much play you get, especially because for every 1 degree at the cam you have 2 at the crank. Pete put it perfectly.... Noodly. You have rockers/followers whacking on different side of the lobes, lash in the gears, crank noodles, etc.
My money is on crank trigger. Heck, Summit might have one in stock.
Edit... Looks like MSD used to make one, but it was $400.
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