Part Five: Ignition Timing

[Stump Shot]

My take on it .....The plug makers may want a consistent gap for more than the spark....they would need to spec there plugs for distance above the piston so everyone else knows the plug is not going to come into contact with the piston top at TDC taking that measurement into there calculations . Tinny amounts.. Yes...but most things are made to a industry standard if they are cross platform so something that is in theory ..moveable...has to start somewhere as a datum .

Hey there Simon, It just seemed very interesting to me that at jumping an .020" gap no change in amperage occurred from just going through the electrode itself and not jumping. So it seemed to me the .020" gap is somehow in tune with the electrode itself. How this all is to be this way I truly wonder. How much does it all matter, might be in one of the hot rod saws with super high compression, a few thousandths of an inch do start to become important.

 

[Motorhead]

Electromological

 

[Simondo]

Hey there Simon, It just seemed very interesting to me that at jumping an .020" gap no change in amperage occurred from just going through the electrode itself and not jumping. So it seemed to me the .020" gap is somehow in tune with the electrode itself. How this all is to be this way I truly wonder. How much does it all matter, might be in one of the hot rod saws with super high compression, a few thousandths of an inch do start to become important.

Hi Steve...that gap size is so common ....we set most plugs to it in many sorts of spark Ign engines. You could say there is a tinny bit of ignition delay and increase resistance the current generated has to cope with having a bigger gap but like you i can not see it making much difference in a measurable and performance related way. The plugs need to be consistent in seated to overall length (from factory) to reliably fit them into a wide range of engines. We stress a ignition system with a spark tester that requires the current to jump a "massive" gap compared to the plug so i figure there is plenty of latent redundancy in there that a few thou wont cause any agro with. A feeler gage works for me without giving me issues.
Now ...this thing with the auto tune saws needing a real accurate gap ! ? .....can the ignition units even detect any delay caused ? I really wouldn't know ....but its been said the 550 and 562 (560) can be fussy .

 

[Stump Shot]

One possible benefit might be on starting. With the motor not at operating RPM the modulated coil gives out a weak response. Having to use extra amperage here that isn't even available would seem to be a detriment. As far as a racing engine goes, might also be helpful to have a little extra spark available to light the fires. I would really like to just publish the raw data and let the chips fall where they may, but realizing where I am, I don't want to start the great spark plug war of '17, let alone ruin this thread. As it could be seen as two brands were clear winners by the numbers. I'm not convinced in that 100%, it was just too close. Then again in a race that comes down to split seconds would .01 ampere be the deciding edge? All I know for sure is, I went looking for the holy grail in spark plugs. This testing did not find it. Came out the other side with the fact that the gap was more important than I had believed. Even though they did teach us that in school, there just was never the why along with it. So for now all I can say is use your favorite brand, and gap them to specs. Then go have fun!

 

[Simondo]

One possible benefit might be on starting. With the motor not at operating RPM the modulated coil gives out a weak response. Having to use extra amperage here that isn't even available would seem to be a detriment. As far as a racing engine goes, might also be helpful to have a little extra spark available to light the fires. I would really like to just publish the raw data and let the chips fall where they may, but realizing where I am, I don't want to start the great spark plug war of '17, let alone ruin this thread. As it could be seen as two brands were clear winners by the numbers. I'm not convinced in that 100%, it was just too close. Then again in a race that comes down to split seconds would .01 ampere be the deciding edge? All I know for sure is, I went looking for the holy grail in spark plugs. This testing did not find it. Came out the other side with the fact that the gap was more important than I had believed. Even though they did teach us that in school, there just was never the why along with it. So for now all I can say is use your favorite brand, and gap them to specs. Then go have fun!

Hell no !! we dont want plug wars .....Il keep doing what im doing as there seems no prob..plus im not into the race or full on mod stuff anyhow . Nice bit of work with the test though Steve

 

[Stump Shot]

Hell no !! we dont want plug wars .....Il keep doing what im doing as there seems no prob..plus im not into the race or full on mod stuff anyhow . Nice bit of work with the test though Steve

Basically, I did all that to learn to go back to the basics. It was all that was necessary. Lol Oh well, I had fun doing it, I don't have to change brands and if nothing else might be a better mechanic out of the deal. So no regrets. Now for the hard part, I have to dream up another way to find that holy grail spark plug, it's out there somewhere. Lol

OK, Back to timing peoples, apologies for the derail.

 

[bikemike]

I like to think I'd rather have the spark plug fail before the motor when overheating. I don't believe hotter rated plugs spark hotter, they spark when hotter.

I think a sparking plug heat range on a 2 cycle that is run in short durations should be replaced with a cooler plug that takes less time to gain heat to clean out. But longer run engines like boats bikes or bucking saw should stay with the same or hotter plug to displace heat and prevent pre detonation

 

[MattG]

My take on it .....The plug makers may want a consistent gap for more than the spark....they would need to spec there plugs for distance above the piston so everyone else knows the plug is not going to come into contact with the piston top at TDC taking that measurement into there calculations . Tinny amounts.. Yes...but most things are made to a industry standard if they are cross platform so something that is in theory ..moveable...has to start somewhere as a datum .

FWIW, the spark gap is all about the spark. Too big and it won't jump.....too small and it will foul.

 

[Chainsaw Jim]

I think a sparking plug heat range on a 2 cycle that is run in short durations should be replaced with a cooler plug that takes less time to gain heat to clean out. But longer run engines like boats bikes or bucking saw should stay with the same or hotter plug to displace heat and prevent pre detonation

You think the plugs produce different temperatures?

 

[bikemike]

You think the plugs produce different temperatures?

No. I think it holds temp and in a 2 cycle engine the temp range is crucial to how a engine runs. A cool plug should warm up quickly and clean off quick. Start stop operations as where a longer runs keeps a plug dry of oily residue and a cold plug could get too hot and act like a glow plug and pre ignite the gasses

 

[Chainsaw Jim]

No. I think it holds temp and in a 2 cycle engine the temp range is crucial to how a engine runs. A cool plug should warm up quickly and clean off quick. Start stop operations as where a longer runs keeps a plug dry of oily residue and a cold plug could get too hot and act like a glow plug and pre ignite the gasses

A hot plug warms up quickly but doesn't dissipate heat as well. A cold plug dissipates heat faster and warms up a little slower. A colder plug will give a race application better performance than a hotter plug will.

 

[MustangMike]

Installing the SC kit on the Mustang also involved installing cooler plugs (that came with it).

 

[MustangMike]

Back on topic, I did a timing advance on my Brother's MS 460 today, which previously only had a dp muff cover installed. Took just over .020 off the key, and it seemed to wake it up nicely.

Only had Silver Maple available for testing, but I could dog it real hard in that w/o slowing it down, so I'm anxious to test it in some harder wood.

 

[shorthunter]

I've advanced some 46 and 66 3/4 of the key. They weren't hard to start there. I'll be playing with some of the 1124 soon and they may not get as much advance on them

I did half a key on the 460 I did earlier this spring, it would bite you if you weren't careful. Ran really well though

 

[mdavlee]

I did half a key on the 460 I did earlier this spring, it would bite you if you weren't careful. Ran really well though

Yep. They run crisp at half a key. Full key they can lose rpm

 

[mdavlee]

Back on topic, I did a timing advance on my Brother's MS 460 today, which previously only had a dp muff cover installed. Took just over .020 off the key, and it seemed to wake it up nicely.

Only had Silver Maple available for testing, but I could dog it real hard in that w/o slowing it down, so I'm anxious to test it in some harder wood.

Try .035" on one.

 

[MustangMike]

This saw is not ported, maybe on one of my ported ones (they have about .020).

Have you tested .020/.025 against .035???

 

[moparnut88]

A hot plug warms up quickly but doesn't dissipate heat as well. A cold plug dissipates heat faster and warms up a little slower. A colder plug will give a race application better performance than a hotter plug will.

This is what I was referring to in an earlier post. I was wondering if with the huge bump in compression if any one has changed the temp on plugs? And if so have they seen any gains in them?


Sent from my iPhone using Tapatalk

 

[bikemike]

A hot plug warms up quickly but doesn't dissipate heat as well. A cold plug dissipates heat faster and warms up a little slower. A colder plug will give a race application better performance than a hotter plug will.

Well I was on the right page with temps but it's been years since I was doing bike events and Change out plugs for different applications hillclimb bike are like top handle saws you fire it and on clean out you get is a few brapps of the throttle then go for 6 seconds, Didn't have a spot to hole shot and bring up engine temps and clean em out. Vs mx and enduro races where you bike was still a Lil loaded up at the start of a race and cleaned out by the time you went through a few gears. And that's where I get my plug comparison on how plugs make a engine perform depending on operating time

 

[MattG]

mx and enduro races

Stop it! You are making me all nostalgic...