Autom. advance spark timing

[Synchro909]

Originally Posted by Werner

Special question to Synchro: Why is it a problem for you to get spare parts etc. from the USA?
.

Werner, The trouble is, the United States Postal Service is not sending mail to this part of the world any more. I cannot attest to the accuracy of information I received a while ago but they say it is because President Trump defunded the post office so aggressively. Where that is the reason or not, I can't say. I (and every one in the SW Pacific region) just know we can't get anything by post.
I'm waiting for some enterprising person in say, Canada to start forwarding mail from the US.

[emf]

I was told by Nu-Rex that their auto advance would not work with a Model B distributor. With my B engine set up the way it is, the B distributor would not provide enough advance at higher rpms. I finally went 'all in' and put a Mallory unit and never looked back. The only problem is that it destroys the original look of the engine compartment.


Frank

[Y-Blockhead]

Originally Posted by emf

I was told by Nu-Rex that their auto advance would not work with a Model B distributor. With my B engine set up the way it is, the B distributor would not provide enough advance at higher rpms. I finally went 'all in' and put a Mallory unit and never looked back. The only problem is that it destroys the original look of the engine compartment.


Frank

And a B engine with two 97's doesn't?? I like your air filters.

[Werner]

Today I mounted the NuRex centrifugal phaser. The stroboscope/flashlight ignition lamp indicates 0 degrees when idling and 28 degrees at high RPM. That's how it should be.

However, the engine "rings/knocks" very clearly when going uphill; I have to reduce the ignition timing at about 5 - 6 °.
Is that normal?

(The cylinder head is planed off by 0.08".)

[alexiskai]

How were you handling your spark advance before, when you did it manually?

[Werner]

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Guten Morgen,

with the hand lever the ignition was at -3° and with the lever almost down (gap 1/7") at 25°.

It is noticeable that with the automatic ignition advance full throttle uphill the engine pings more at 45 mph than at 35. If I go back 5 or 6 degrees, the knocking stops, but then there is a lack of traction.

[Synchro909]

Originally Posted by Werner

Guten Morgen,

with the hand lever the ignition was at -3° and with the lever almost down (gap 1/7") at 25°.

It is noticeable that with the automatic ignition advance full throttle uphill the engine pings more at 45 mph than at 35. If I go back 5 or 6 degrees, the knocking stops, but then there is a lack of traction.

Werner, the last thing you need is pinging. That means the timing is very much too advanced and it does great damage to the bottom end of the motor. I wonder whether you are expecting too much from the engine. How is it unmodified? It clearly is running higher compression if you can get it to ping at 25° advance. That's about the maximum advance for a 5.5:1 head. On one of my engines, I run a 6:1 and gave up on a Model B distributor very quickly. Instead, I run a standard A distributor and with the aid of a timing scale on the front of the motor and a timing light, I made a fitting I screwed to the side of the distributor. It has a screw in it that works like a throttle stop on the carburettor to limit the movement of the top plate. I set it to 22° so no matter what I do with the steering column lever, it cannot go past 22°. It works very well but I can get a ping at low speed if I press the accelerator too far.
When you hear pinging, push the lever up till it stops. That is as much as you can do on those hills.

[nkaminar]

My computer adjusts the timing for different conditions such as cruising down the highway or going up a hill or idling. My computer resides under my hat.

[jack backer]

Stock compression engines are tolerant of timing deviation, manual spark is effective.Higher compression engines require mechanical spark control to avoid detonation.

[old31]

What am I missing here, other than brain cells.

Yes, the device is clever. The ONLY advantage i can see is for those that can not hear the engine.

It has a cost associated with it that is not needed.

It takes mechanical knowledge to install.

You have introduced 1 more item that has the chance to break or not work and cause damage.

I don't think it does a better job at regulating the timing, as long as you can hear the engine.

So, unless someone can show me the advantage I am 100% with NK.

[jack backer]

Timing for a model a engine for optimal performance is roughly 1 degree advance per each 100 rpm.. for instance 10 degrees advance at 1000 rpm… both accelerating and decelerating. That being said,at 4.2 to 1 compression the engine will perform adequately adjusting it manually,if that is your preference.

[alexiskai]

I would be interested to see what happens if you drain the gas, put a couple gallons of high-octane petrol in it, and run those hills again. In Germany, you should be able to get 95, 98, or 100 octane. Try it and see if it makes any difference. This will help diagnose the issue.

[SonicRaT]

Originally Posted by alexiskai

I would be interested to see what happens if you drain the gas, put a couple gallons of high-octane petrol in it, and run those hills again. In Germany, you should be able to get 95, 98, or 100 octane. Try it and see if it makes any difference. This will help diagnose the issue.

I have the device installed in my '31 coupe with a 6:1 head and run 93 (US rated) almost exclusively. I was a bit concerned that I would need to add some additional adjustability through the lever when I set it all up, as most warned against the combination. However, I've not experienced any knocking or issues leaving my lever set at TDC. I've run it quite aggressively through a variety of driving conditions without a hitch so far. I haven't yet tried a lower octane, as most of the time it is mixed with ethanol here, but I've been curious if I would pick up a ping if I did.

[bavArian]

Standard petrol engines on cars today have a 9:1 compression or higher. I don't see how a 6:1 head could induce problems, even with the higher mixture temperature compared to direct injection.


Over here you can only get 95 octane or higher fuel, so I doubt it's a fuel problem.

[jack backer]

This is true but you are not comparing it correctly, Modern small piston OHV engines at 9 to 1 compression ratio has a different ( and way shorter) flame travel and the opportunity for detonation is way lower than an L head at 6 to 1 with 50 cuin pistons. On a modified A engine combustion chamber design can help create a detonation condition.

[TomInCologne]

Originally Posted by jack backer

This is true but you are not comparing it correctly, Modern small piston OHV engines at 9 to 1 compression ratio has a different ( and way shorter) flame travel and the opportunity for detonation is way lower than an L head at 6 to 1 with 50 cuin pistons. On a modified A engine combustion chamber design can help create a detonation condition.

as a combustion engineer... this is true,but don't forget that at the higher pressure the flame speed will be a lot higher than at the lower pressure...


Sorry, i was just trying to confuse matters more... ;-)

[alexiskai]

A lot of stuff can cause detonation at "normal" advance numbers, not only compression. For example, the plugs might be too hot, or there might be too much carbon build-up. Another possibility is that the owner makes a mistake with initial timing, so the actual total timing is higher than he thinks. I asked about octane because it's a test that would yield some information without requiring engine surgery.

[Werner]

Hi,


I always drive high-octane alcohol-free gasoline. I fill up with leaded fuel every now and then. (This makes the engine run much smoother.)

Modern iridium spark plugs, whose heat value I have now increased from 5 to 6 (NGK) for the test drive. No difference.

If I richen the mixture 1/8 on the choke spindle, the knocking is a little less.

The combustion chamber and the piston head are very clean, so I can rule out glow ignitions caused by carbon.

It is not engine knocking at low speeds and high loads, but the typical "high speed knocking".

Perhaps the NuRex's automatic advance is too fast. I will try to record the ignition timing with the strobe and camera while driving at the beginning of the engine pinging.

[jack backer]

Originally Posted by TomInCologne

as a combustion engineer... this is true,but don't forget that at the higher pressure the flame speed will be a lot higher than at the lower pressure...


Sorry, i was just trying to confuse matters more... ;-)

I had the opportunity to tune a Miller OHV conversion on a Model A what I found interesting is how much advance it would “take”. We didn’t map it but I would estimate it at 30 to 40 degrees..


Werner the gyro type advance curve is fixed, unlike a flyweight advance where you can adjust curve by altering spring tension. I would set base idle timing at 0 degrees as a starting point to “pull” the curve back to avoid detonation.

[Ruth]

This has been discussed in previous threads where it is suggested to set your 0° ½ way down the quadrant so you can retard the timing if needed. The Phillips/Nurex will advance the timing 30° and I have found instances where my engine doesn't want that much.