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Megasquirt Timing Check - would this idea work ?


Hybrid_From_Hell

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Ok,

as the bump on my head means I can't do much :im-ok-smiley-emoticon: I have still been doing some minor thinking .............

I have a huge number of peeps ask me about checking tooth / timing TDC issue, I have tried all sort of ways inc a video,

but still they either set it wrong or can't grasp the various waqys to check, however nicely I explain it sometimes !!!

Now, I have had a small eureka moment (as oppossed to a WTF moment) and was wondering ........

Megatune when powered up shows the sensors that work etc and also the spark angle, which is normally a where it stopped number.

so, my question is

With megatune on, if you where to manually wind the crank nut around and turn the engine over, if you ensure the "Gap" goes past the VR sensor,

and then wind it around to show the ENGINE at TDC will the megatune not now show the spark value, and it should be 10 degrees ?...as such if it reads not 10 then

trimming within the software would then correct timing (although it will still show wrongly on megatune)

So, has my bump just made me dafter or would this work ?

Fire away :lol:

Nige

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To calculate the gap position the ECU has to see all the teeth going past the VR sensor and it normally takes at least 2 full revolutions of the crank to be "confident" in what is a gap and what isn't. It doesn't know which is the missing tooth gap as such but just makes a "guess" based on the frequency of the other pulses as the teeth pass the VR sensor. If it sees 600 pulses go past in a second and every 36 ish pulses there's one that's twice the size of the others it figures that's that gap.

To manually turn the crank at a speed fast enough and constantly enough for the ECU to make sense of it is beyond the capability of mere mortals and certainly beyond the capability of anyone who can't figure out how to use a timing light !

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I must admit that of all the things I am looking at doing (modified axles, modified brakes, roll-cage, seats, megajolt) confirming that I have the timing wheel on the right way round is the one that drives me nuts!!!!!!

First time it was the wrong way round, now it is correct (I think) I am not happy about the TDC pointer as it may have been moved and is not easy to see/cant be seen directly in line!

Currently I am considering a peg in the spark plug and a timing wheel to check it, my concern is of course about punching a hole in the piston!

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I am pretty certain that the key way in the crankshaft is exactly lined up with cylinder 1&2 crank pin, therefore if the pulley/damper is being removed to fit the 36 tooth timing sprocket, its a simple case of offering the sprocket up to the pulley/damper with the gap inline with key way then rotate it however many teeth the correct way and fit.

Or mark the outer of the pulley in relation with the key way and mark the block between two known points eg. Bolt holes to align the pulley at tdc, then clock the sprocket to suit the vr sensor and mark the point at tdc, remove and fit the sprocket to the pulleny/damper then refit to the engine.

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I must admit that of all the things I am looking at doing (modified axles, modified brakes, roll-cage, seats, megajolt) confirming that I have the timing wheel on the right way round is the one that drives me nuts!!!!!!

First time it was the wrong way round, now it is correct (I think) I am not happy about the TDC pointer as it may have been moved and is not easy to see/cant be seen directly in line!

Currently I am considering a peg in the spark plug and a timing wheel to check it, my concern is of course about punching a hole in the piston!

Thats how i did mine. A 4.6 doesnt have a timing marker

Drilled out a spark plug, put into cylinder no1. long bolt through, dial guage on end.

Rotate engine back and forth to find tdc, then move trigger wheel to the correct position

Mark, drill

Just make sure its bolted back up same way it came off :hysterical:

post-19862-0-79291000-1385844992_thumb.jpg post-19862-0-08961400-1385844992_thumb.jpg

HTH

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Excellent explanation Bingy - top work!

The most accurate way to check TDC, is to do what Missingid proposes and use a degree wheel and a stop on number 1 piston, and the most accurate way to do that, is to remove the head and clean the piston crown.

Turn the engine by hand until the stop touches the piston and note the reading; turn the engine the other way by hand and note the reading; then add the two degree readings together and divide by 2 - the answer is TDC. When the degree wheel is set at the answer position, the accuracy of the timing case pointer and the mark on the crank-pulley, or flywheel can be checked.

Bingy's method is fantastic for when the head is in place, but two variables need to be considered. How much carbon is on top of the piston crown - which will affect the reading slightly? Can we be 100% certain that the bolt inside the old spark plug is moving freely and not sticking a bit, or moving sideways a little, when we really want it to rise vertically, which it can't do?

If I didn't want to remove the head I would use Bingy's method. Am I right in thinking that the timing can be adjusted on MS and that it is called the trim angle? If so; slight error in the Bingy method could be adjusted anyway,

Cheers Charlie

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I fixed a bolt in a hollowed out spark plug, turn engine one way, mark pulley, turn engine other way, mark pulley, TDC is in the middle of the two marks, simples :)

I had no carbon on the piston -I'd had the head off :)

I don't understand wtf Nige is on about though, lay off the chablis old man :)

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Use a manometer to check for TDC on No1 …………… as it will also ensure that the valves are closed and thus fool proof.

Old drilled out plug ………….. ¼ adaptor for plastic pipe screwed in to plug ……………… a couple of feet of ¼ (6mm) tube ………………..a bit of wood and some cleats to make a U bend ……………. add a little water …………….. job done

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