Tuning injection timing by ear

[cujet]

So, my twin started making a bit less power in the RH cylinder (the one farthest from the gov). In fact, it would not even make black smoke any more. So, after changing the inj and pump (did not help) Rocketboy adjusted the timing thereby increasing the pump stroke. As you would expect, that cylinder now makes a loud diesel knock.

I suspect there is an underlying problem with the timing of the cam lobe, or some unusual wear going on.

In any case, I wondered if any of you guys tune by ear. It is obviously easy to tell when there is too much advance, by the loud knock. There must be a point where the engine is "quiet enough" but powerful and efficient.

Obviously, in my case, the spill timing was a bit shy in the power department due to maximum pump stroke issues.

Chris

[SteveU.]

Flatten/worn cam lobe? Check lift height.

Hope I'm wrong
SteveU.

[ronmar]

Or a problem with the roller on the cam follower.  Seems to me Hotater had a problem with one that caused the injector timing to shift at random.

I figured out a way to fire an inductive pickup timing light using the injector noise when the popet valve opens.  It takes about $35 in parts from Radio Shack, but it is pretty simple to make.  It might be pretty handy to balance a twin.  If you are interested, I can post a drawing and parts needed.

[cujet]

ronmar,

Of course I am interested!! Bob and I have been thinking about doing this for a while. However, we never spent the time to develop a system. I would be eternally in your debt for such a drawing!

Chris

[cujet]

I will take a good look at the internals soon. For now, it took about 11 flats, or almost 2 turns of the adjuster to get the power even.

I am fairly certain the roller is the problem.

Chris

[ronmar]

Here is what you will need to put one together:

1. Inductive pickup automotive timing strobelight.
2. Radio Shack Mini-Amp #277-1008  http://www.radioshack.com/product/in...Id=2062620&cp=
3. Radio Shack Electret mic element #270-092  http://www.radioshack.com/product/in...tPage= search
4. 2EA 1/8" mono audio plugs(to plug into audio amp)
5. 1EA AA Battery holder clip (to power mic element)  http://www.radioshack.com/product/in...entPage=search

The amp itself will need a 9V battery, the mic will need a AA, and you will need 12VDC for the timing light .  Assembled as per the attached drawing, and with everything powered, clip the timing light inductive pickup over the coil of wire comming from the audio output.  Once this is done, increasing the amp volume while taping the mic element on the bench, or flicking it with your finger should cause the strobe to fire. Depending on the sensetivity of your timing light, you may need more or less coils for the light to trigger off of.  Mine works well with 3 and the volume control on the amp just below mid range.

To use, hold or attach the mic element to the top of the injector, or down on the side of the injector body below the retaining plate/clamp.  You can use a mechanics stethescope to find a good place.  I taped mine in place with electrical tape.  You want the conducted noise from the injector, so a good physical contact is in order.  Apply power to everything, and make sure all the cables are routed safely and start up the engine.  Increase the amp volume thumbwheel slowley untill the light just fires reliably in time with the exhaust sound.  Too much volume control and the light will start to trigger on other noises bouncing around in the engine. Point the light at your timing marks.  This is best done in a darkened place, so be carefull of those spinning wheels-O-death. 

In my case, setup as above, this audio amp fires the light at the start of the injector pulse.  I wish I could capture the image, because it was pretty cool.  I removed my injector from the head and re-attached it to fire upwards.  While hand cranking, I pointed the strobe at the injector tip.  The strobe flash caught the first 4 1/2 inches of the fuel spray out of the tip.  Another surprise was where the actual firing was when running.  I re-checked my spill timing and it was at 20 BTDC.  The strobe flash on the flywheel shows the injector firing at 2.5 BTDC.

Enjoy!

[mobile_bob]

Ron:

i take it the 3 turn coil presents enough impedance so that the amplifier does not see it as a short?

in any event it works huh?

anyone know of an inxpensive inductive timing light?

bob g

[mobile_bob]

check that, looks like at least 50 of em on ebay
what would be cool would be to put all the stuff inside the light
amplifier, loop and a power supply, ic regulators? and then bring out one line for
the mic pickup,,

bet you could sell those like hotcakes!

i would buy one.



bob g

[BruceM]

Wonderful job Ron! When I have time for some more Listeroid twiddling, I'll be using your idea to check timing. 

I was wondering...did you change your engine timing based on the strobe, or is 20 degrees BTDC spill really where it should be (at 2.5 degrees, really)?

[ronmar]

Bruce
   No I did not make any changes to my timing.  By all other indications, my engine is runing great.  You do bring up an interesting point though.  Where SHOULD the injector fire on a slow speed single?  I can see where spill timing came from.  Simple, no special tools or PHD to setup are required, but it assumes some pre-requisites are in place.  Injector pump is sealing and building pressure correctly, and the injector pop pressure is set correctly.  Without measuring equipment, these are unknowns, but they will have a bearing on where the injector fires in relation to the spill timing point.  Now that I have a reasonably accurate way to measure it, I may do some fuel consumption VS injector timing tests.  But I first need to find the time:)  I have an exhaust heatex design burning a hole in my brain that I want to build a prototype for...