Ignition advance for economy when crusing

[Guest Nigelstephens]

Thanks to the MY16M ECU I have been very happy with my Sport i performance and smoothness.

However fuel consuption has never been that good at about 38-42 mpg.

 

I am doing a little research before a dyno session and would be grateful for some help with the question of ignition advance for economy.

 

I specifically trying to leave out the mixture setting for now in this discussion unless it is necessary.

 

As a simple test I pulled up in a layby when the engine was at running temp. I then held the throttle to get an engine speed of 3000rpm. Keeping the rpm steady I altered the ignition advance using this map point. The initial setting was 29 BTDC.

 

These are my results.

< 25 engine loose speed and faulters

26 - 31 smooth and engine gradually increases rpm

>31 speed continues to increase and engine sounds heavy.

 

This suggests that at this map point of rpm and throttle opening (1,6 to those with an MY16M) the range of 26-31 BTDC is what I need to use.

 

These are the questions I have.

1. If I were to use 26 rather than the 31 would this be the better economy setting?

 

2. On a dyno does the difference in torque show up eaisily for a test such as this. That is, at constant roller speed changing the timing will effect torque. Is it easy to see the torque values change and to arrive at a more exact timing value.

 

3. On a dyno does for best economy, does one adjust for max torque and then back off on the timing advance slightly to reduce torque (say by 5%). Or how is it done correctly?

[Ryland3210]

I haven't seen vacuum advance on boats or motorcycles. I know a little about them as applied to automobiles having studied and tuned them for many years. Here's a simple description to get you started.

 

Vacuum advance on automobiles is used to improve economy when the engine is under light loads. When the throttle is wide open, it is eliminated to prevent preignition.

 

Since boats get relatively low miles per gallon, I wondered why my V8 powered 18 footer (5 mpg) has no vacuum advance. The main difference is that at cruising speed, a boat motor is producing such a high percentage of maximum, that the vacuum advance would be defeated anyway. At idle speeds, more fuel is consumed without vacuum advance, but the idle is smoother and more controllable at low RPM, and the difference in consumption is small relative to 5 mpg at cruise. In the 34 footer I once owned, even more so, since 1.1 mpg was typical.

 

For example, back in the 60's, before environmental issues were a factor, some automotive distributors connected the vacuum advance to a port just above the carburettor throttle plate to defeat it at idle to make it smoother. I found that by connecting it to the intake manifold directly, idle speed rose significantly and I was able to save fuel by adjusting the idle screw back down.

 

Decades ago, motorcycles did not have nearly the power they do today, so they were in the same situation as boat motors. In addition, most single or dual cylinder engines had no distributor with a breaker plate to make it easy to implement vacuum advance. Finally, of course, is the added cost and complexity of adding vacuum advance.

 

Bottom line is that for engines under partial load, such as 90 hp motorcycles at cruising speed, I have no doubt that vacuum advance or its equivalent would reduce fuel consumption considerably.

 

I haven't looked into it, but with today's computer controlled motorcycle engines equipped with numerous sensors, it is certainly possible for the mapping of ignition timing to include the equivalent of vacuum advance. It may be that yours already has the equivalent.

 

I'm sure others will weigh in with specific answers, and I'm looking forward to that.

[Guest Nigelstephens]

Yes, the MY16M by Cliff Jefferies has a 15 x 15 map for fuel and another grid for timing.

The y is throttle opening and the x is rpm. This corresponds to a vacuum control in that different values can be set for 15 throttle openings at the same rpm or visa versa.

[Ryland3210]

Yes, the MY16M by Cliff Jefferies has a 15 x 15 map for fuel and another grid for timing.

The y is throttle opening and the x is rpm. This coresponds to a vacuum conrol in that different values can be set for differnting throttle openings at the same rpm or visa versa.

 

My 1300 cc 850 pound Yamaha Venture with 4 carburettors, full fairings, saddlebags and luggage compartment gets about 48 mpg cruising at 63 mph and 43 at 75 mph. I think compression ratios are about the same. If fuel/air ratios and timing were the same, that leaves at the least, valve timing and engine temperature as other causes for the lower economy.

 

In answer to the 26 versus 31 degrees advance question, when I used to experiment, I found that the more advance the better in terms of economy, although the engine ran a little rougher when very advanced. I think this was due to missfiring. There are limits. At extreme advances, say beyond 45 degrees, there can be missfiring if the mixture isn't compressed enough, and the potential for preignition.

 

The Yamaha is water cooled, so temperature is more consistent than air cooled. You didn't mention temperature. The MG mapping might have to be more conservative to prevent preignition if there is no input into the map for engine temperature. In other words, to prevent preignition crossing a desert in the summer at high speeds, versus reasonable economy at 20 C in the rain.

[Alex-Corsa]

The MG mapping might have to be more conservative to prevent preignition if there is no input into the map for engine temperature. In other words, to prevent preignition crossing a desert in the summer at high speeds, versus reasonable economy at 20 C in the rain.

 

The original MG mapping has parameters for engine temp and air though air temp isn't that well mapped causing on cold days higher consumption that it should, and richer AFR measured at the exhaust as well.

I get an aprox. 43-49mpg on cruising to speeds 60-95mp/h,using my own developed chips.AFR varies 12.2-12.8 between those rpm

[Guest Nigelstephens]

Alex

Thats quite a similar AFR to mine between 12.5 to 13.0.

How do you measure yours. By free O2 with a lambda sensor?

[Cliff]

Alex

Thats quite a similar AFR to mine between 12.5 to 13.0.

How do you measure yours. By free O2 with a lambda sensor?

 

That AFR is what people use when aiming for best power. I would think 13.5-14 would be better for economy.

[Alex-Corsa]

Alex

Thats quite a similar AFR to mine between 12.5 to 13.0.

How do you measure yours. By free O2 with a lambda sensor?

 

I use the Innovate LC-1 kit with XD 1 indicator.

Sensor is pluged to the header exaust ca.50cm after the cylinder exhaust hole

It is real time and I believe one of the most accurate in the bussines.I think there can be a difference in what actually going on and what really is between different AFR measurment units.

 

In your case I would fisrt look at the synchronization of the TB's and definatelly the TPS voltage to be set correctly on both TB positions (0 and 3.5')

And or you have to programm the fuel map a bit leaner to (as stated) reach a mid 13-14 AFR.

 

And yes the AFR I have targeted is for best power.Though at the end for me it is quite OK with the cosumption therefore I leave it as is..

[Guest Nigelstephens]

If I adjust to lower than 13.5 I get loss of power and roughness. There is a definate barrier to going below this value. That is why I was wondering about the effect of timing and tolerance of mixture. Would moving the timing +/- BTDC have any effect?

 

I would think it was an inacuracy in the LC2 but my plugs are often sooty indicating rich mixture.

[Alex-Corsa]

If I adjust to lower than 13.5 I get loss of power and roughness. There is a definate barrier to going below this value. That is why I was wondering about the effect of timing and tolerance of mixture. Would moving the timing +/- BTDC have any effect?

 

I would think it was an inacuracy in the LC2 but my plugs are often sooty indicating rich mixture.

 

All I know is afecting the timing will change also the AFR as well, so there you have it, in summary.Reduce the timing and it will be a leaner effect to the exhaust AFR , i.e. but I think this prehaps won't be as "healthy' as when only the fuel map is changed to achieve the same "leanness"(while still have optimum timing on the spot unchanged).IF the timing is correct don't mess with it, you'll only have to check out fuel and temprature parameters,cause you'll do more harm that good..

AFAIK LC1 works faster than LC2 and is been concidered as the most accurate of the innovate line.

 

 

 

P.S> you could try their forum as well

http://www.innovatemotorsports.com/forums/index.php

[Ryland3210]

All I know is afecting the timing will change also the AFR as well, so there you have it, in summary.Reduce the timing and it will be a leaner effect to the exhaust AFR ,

 

First, let's recognize that measured AFR on the basis of an exhaust gas sensor is different from the physical AFR delivered by the intake system.

 

It seems to me the influence of timing on apparent (measured) AFR is due to how complete the combustion is. I'm assuming by "reducing" you mean retarding. I'm interpreting your result as an indication by the sensor of more complete combustion, i.e., less unburnt fuel. But that implies that timing was too far advanced to begin with. If the timing was optimum, I would expect measured AFR to indicate richer on either the advanced or retarded direction.

 

Does that make sense to you in your experience?

[dlaing]

If the timing was optimum, I would expect measured AFR to indicate richer on either the advanced or retarded direction.

 

Does that make sense to you in your experience?

Optimum timing is what you want for both power and efficiency.

If the engine runs rough above 13.5 AFR it could be because the timing is too advanced.

I am not sure, but retarding the timing and leaning the fuel may give the desired result or enrichening the fuel and advancing the timing. I think the only way to find out is to try, but certain symptoms can give you a clue. Popping and surging usually indicate lean while pinging usually indicates too much advance.

The Guzzi has a primitive temperature regulation system, so it is difficult to keep the timing point at the opimum.

In the infamous ECU thread, we discussed the accuracy, or the lack there of, of the WBO2 wide band oxygen sensor. In the rich mixture ranges that the Guzzi uses, the sensor is PROBABLY measuring CO. If the mixture is lean there is no measurable CO. If it rich, CO increases, but optimal burning also reduces CO as sub-optimal burning can increase CO, so it is not a perfect indicator of mixture.

The WBO2 reads CO, so if the timing is advanced beyond optimum, the burn is more complete and the meter reads low CO or lean.

If the timing is retarded from optimum, the burn is less complete and the meter reads high CO or rich.

Those are generalizations, and there is more to it than that. At some points the WBO is measuring Oxygen, which correlates very differently to the AFR then does CO.

If we were just measuring residual oxygen incomplete burning and lean conditions could both indicate lean.

If the WBO2 sensor is reading O2 then timing's effect on AFR reverses from what we observe measuring CO. Going to the retarded side of optimum could result in unburned O2 and a lean reading. If the timing is advanced from optimum burn is more complete and the O2 is consumed giving Rich reading.

Whether the WBO2 is relying on O2 or CO to determine AFR depends on how much O2 there is in the exhaust. So, it is easier to find optimal fuelling and timing at richer mixtures. When we start trying to make it economical the WBO2 readings become less accurate. For that reason it may be good to start rich, with more advance and then work your way slowly to your goal.

Interestingly WBO2 makers often claim things like 0.1% accuraccy, and yadda yadda yadda, but independent testing show great desparities between sensor units, even when using the same sensor.

This is not to say the tools are useless, but they should be treated as imperfect, much like a wood meter stick that varies with temperature, humidity, parallax, and presbyopia

Using multi-gas analysis, of course, will provide a more accurate analysis of the mixture.

Also, I think an Exhaust Gas Temperature sensor could be as useful as the WBO2.

[Guest Nigelstephens]

Thanks for the detailed explanation.

 

For interst sake I logged my AFR over a 2 hour journey. Was able to build up a map correction table in Excel and apply it to the ECU. I was very weak at WOT settings. I then tried it on the road. What a difference! so much smoother and more power. The AFR is a good indication as by experiance I have come to know what my bike likes. However, I reaslise changing the timing may upset this interpretation, from what you have said.

 

Im having my first dyno session tomorrow will look at exhaust gas analysis with interest.

[raz]

Thanks for the detailed explanation.

 

For interst sake I logged my AFR over a 2 hour journey. Was able to build up a map correction table in Excel and apply it to the ECU. I was very weak at WOT settings. I then tried it on the road. What a difference! so much smoother and more power. The AFR is a good indication as by experiance I have come to know what my bike likes. However, I reaslise changing the timing may upset this interpretation, from what you have said.

 

Im having my first dyno session tomorrow will look at exhaust gas analysis with interest.

Please keep posting your experiences, I like the idea.

Would you care to share your current map? I'm still running the map Cliff provided, it would be very interesting to try yours as a starting point. I think I'll postpone closed-loop till next winter.

[Guest Nigelstephens]

Please keep posting your experiences, I like the idea.

Would you care to share your current map?

 

Sure. I will get the dyno out the way and send you a copy.