2002 DX150TLRA Ignition -Timing - Number of sparks per cylinder

[boscoe99]

[captainj]

Thanks Rodbolt,
I going to try and take her to the water to see how she runs. I'm going to check the timing at WOT to see if they advance the same.
I had not ever checked the timing on the other cylinders since I bought in 2002.
I will report back after I take her out.
Thanks to all

[captainj]

Thanks Boscoe , that was very informative that make since to me. That gives me a better understanding of how it works. Where did you find that information?
Thanks,

[99yam40]

I couldn't find the error you are talking about. The only time I have mention BTDC was when the ecm was bypassed the timing went to 7 BTDC and when. I was telling what was marked on the flywheel.
The problem is #1 fires at 3 ATDC and 2-3-4-5-6 cylinders fire a 7 ATDC.

just to show what i read.
no big deal but I had to go back and look again

"I checked the timing because the manual says it should be 3 BTDC so I checked it. It is correct on #1 but on the other five cylinders are on about 7 ATDC.
I have never seen different timing between cylinders before.
When engine is in cold start mode all cylinders advance to TDC and as engine warms up timing on #1 goes back to 3 ATDC and the other five go to 7 ATDC.
When the throttle is advanced the timing advances but they do not advance the same #1 cylinder is advanced more than the rest.

[zenoahphobic]

Welcome to the modern world of ECU functions (and manufacturers not letting on). I am surprised by the surprise that no one knew you can have different ignition timing between different cylinders of the same engine.

Engines of today completely shutdown some cylinders. In affect providing "zero" or no timing whatsoever.

I do not know what is the ECU supposed to do on this particular engine, but it is clear it is easy and open to manufactures to taylor specific inputs to each individual cylinder, be it ignition timing, fuel injection timing and quantity, valve timing and opening amount, and so on.

[99yam40]

Zeno, yes they could do a lot of things, but who knows if they would change the timing of all cylinders except #1 to be off spec at idle.
That was the main question that no one has the answer to or why they would do that.

To me it is not the correct thing to be doing, but I am not a Yamaha engineer.
Think about it , we have heard /read before to look at multi cylinder motors as multiple single cylinder motors tied together with a crankshaft. Running some of these motors at a different spark timing does not make sense

And if there are so few of these motors around he may never get the answer he is looking for unless Yamaha would happen to give it to him.
Or find another motor or ECU to play with and check it himself

Thanks Rod and Bosco for the info on injector timing, we all have learned something new from this

[zenoahphobic]

Yam99 , I don't agree, think it does make sense, each cylinder as a separate engine.
When multiple engines are used we don't share timing between them. Though we do pitch the propellers as if they are performing as one engine.
Your right we need someone with the same engine to do the same test.
I base my view on the fact that the OP has said his motor has run absolutely fine since new (2002).

[boscoe99]

Yam99 , I don't agree, think it does make sense, each cylinder as a separate engine.
When multiple engines are used we don't share timing between them. Though we do pitch the propellers as if they are performing as one engine.
Your right we need someone with the same engine to do the same test.
I base my view on the fact that the OP has said his motor has run absolutely fine since new (2002).

If each cylinder is of the same design (I have no reason to believe there any differences between cylinders) and they are operating at the same temperature at the same RPM and witht the same load, what could possibly be the reason that some would need more or less advance ignition timing than any other cylinder?

Different engines are not connected together. Different cylinders of the same engine share the same crank shaft.

Trivia question for the day. Why are some distributor cam lobes that operate breaker points machined at unequal intervals from other cam lobes on the same shaft, thus causing the breaker points to open and the spark plug to fire at different points? Come on fairdeal, where art thou?

[zenoahphobic]

If each cylinder is of the same design (I have no reason to believe there any differences between cylinders) and they are operating at the same temperature at the same RPM and witht the same load, what could possibly be the reason that some would need more or less advance ignition timing than any other cylinder?

Different engines are not connected together. Different cylinders of the same engine share the same crank shaft.

Trivia question for the day. Why are some distributor cam lobes that operate breaker points machined at unequal intervals from other cam lobes on the same shaft, thus causing the breaker points to open and the spark plug to fire at different points? Come on fairdeal, where art thou?

Today's improvements to engine performance tend to be in small increments; the 2%'rs. As we looked at that ignition curve on previous thread suggested (to me atleast).
So where ever we can make a small change we are able to do this because ECUs can easily cater for whatever.

You are only correct that each cylinder, or at least the crankshaft within each cylinder share the same rpms. All the other parameters are not "exactly" the same because of design constraints! So individual adjustments make sense.

Without straining my brain too much, I think your distributer cam lobe question centres around that 360 degrees cannot be evenly divided within many 4 stroke engines. It's "all about the beat". Harleys sound is because they are uneven and classically different firing order V8s have distinctly different "bomperty bomp bomp".

[rodbolt17]

do what ??????
any 360* circle can be evenly divided.
now do they program the ECU to fire everything at the same time????
who knows.
kinda like why did Yamaha machine the heads and ports to give different compression pressures.

[zenoahphobic]

do what ??????
any 360* circle can be evenly divided.
now do they program the ECU to fire everything at the same time????
who knows.
kinda like why did Yamaha machine the heads and ports to give different compression pressures.

Think about it (famous Rodbolt saying) a Harley doesn't fire it's cylinders 360 divided by 2 equals 180 degrees apart. Similarly other engines using common big end V engines are not equally divided timing.

Firing order decision has its primary consideration to the type of balance (harmonics) produced. A four cylinder is not balanced, for example.

[99yam40]

z said 360 degrees cannot be evenly divided within many 4 stroke engines

why not?

[cpostis]

I wondering if anyone has input on this, that I posted earlier:

"Although #1 cylinder is the same bore as the others (fact), the piston diameter is smaller than the others (fact). #1 cylinder has the port that sends gasses to the O2 sensor (fact). Does this have anything to do with the variance in timing? For that matter, can anyone tell me the engineering reason for the smaller diameter piston"

Thanks!

[zenoahphobic]

I wondering if anyone has input on this, that I posted earlier:

"Although #1 cylinder is the same bore as the others (fact), the piston diameter is smaller than the others (fact). #1 cylinder has the port that sends gasses to the O2 sensor (fact). Does this have anything to do with the variance in timing? For that matter, can anyone tell me the engineering reason for the smaller diameter piston"

Thanks!

If that is true, and no reborn had occurred, then the explanation could be that cylinder gets hotter (probably more correct to say can't get rid of its heat as the others, and therefore it may expand more. The manufacturer cautious to avoid possible seizure or atleast close tolerances creating greater friction.

[boscoe99]

I wondering if anyone has input on this, that I posted earlier:

"Although #1 cylinder is the same bore as the others (fact), the piston diameter is smaller than the others (fact). #1 cylinder has the port that sends gasses to the O2 sensor (fact). Does this have anything to do with the variance in timing? For that matter, can anyone tell me the engineering reason for the smaller diameter piston"

Thanks!

I wish I had an answer for you.

The parts catalog shows the same part number piston being used in cylinders 1,3, and 5. Rings are all the same part number.