AFR and mileage

[dennisj]

Conversation split from another thread talking about fueling and the GT-Rx Kit in regards to engine temp. Ed. - Todd

Den, using a digital infrared gauge, I noted a 40ºF drop at the heads on the few I remembered to note. YMMV, but as Sasha above states, you can feel the difference.

Thanks for the response Todd. 40 deg. F is significant, that's close to a 20% temperature drop. Do you know if Piaggio did anything to reduce the lean mixture of these bikes in their later year models? My Cali Touring is a 2014 model year and I don't believe I'm having the lean mixture symptoms discussed in your posts. I mentioned 250 deg. F readings on my cylinder barrels, I was wrong, I was measuring on the heads too. That doesn't seem excessive to me. Also, I have no hesitation, flat response, poping or backfiring either. My spark plugs don't show overheating at 4500 miles either. My bike seems to run and behave just fine. Did I just get lucky? Am I naive to the actual combustion conditions inside my engine?

I really like what you did with your GT-Rx fueling package but can't tell if I really need it.

Den.

 

[roadventure]

My bike seems to run and behave just fine. Did I just get lucky? Am I naive to the actual combustion conditions inside my engine?

Dennis,

I too have similar experience to yours. I don't know if my bike is running too lean or not as I have not had it run on a dyno with a fuel gas analyzer. But, it does run very well based on the time I have been riding it. I would prefer better fuel mileage and rear tires to last more than 6000 miles but the California does have a big engine that is seems to be designed with performance in mind and not the ability to sip fuel. Rear tire wear........... well that is still a mystery to me.

Regardless of the manufacturer or model I consistently hear from knowledgeable people that the OEM fueling set up is too lean. I wonder if what we are really experiencing is that as we get older and think back to our past experiences we are trying to apply rules that worked then to engines designed now. True, you can't argue the "ideal" 13:1 air/fuel ratio that many strive to reach but is that something that really applies to modern internal combustion engines? Could it be that our engines require high octane gas because they ARE designed to run hot? I wonder.

 

[dennisj]

Hi Dave,

For the first time I was able to get 37 MPG during an easy riding tank of fuel. That is about 5 MPG above what my previous averages have been, though I typically rely upon the ECM to give me the economy figure, this time I did it the old fashion way at tank top off. I'm preparing for a fifteen hundred ride through New England next week so I'll have more chance to get more data. Having 4500 miles on my engine now may be a factor.

As for your "theory", I think you are onto something there. I recently did a little research about the ideal A/F mixture ratio and found numerous credible sources warn that there is no such thing, it's actually a range which is demand dependant. The correct ratios can vary from 11:1 on down to 17:1. Much of the discussion dealt with the various compression ratio, valve timing, induction method and alcohol content of the fuel as well as intended use of the vehicle, such as street, track or hauling a load. So I now wonder about the wisdom of creating a dynamic fuel mixture apparatus that would constantly deliver a 13:1 air/fuel ratio. The bottom line for me is the fact that my bike runs GREAT right now, so I'm not looking to improve its rideability or increase its power, or even to lower its temperature. As it stands now my bike feels cooler than a HD Road King, plus, once in the wind, I'm not concerned about the temperature from a riding aspect.

Additionally, I have used an infrared thermometer to measure the Cali 1400 Touring's cylinder head temperatures and did not find them to be excessive. Though I will admit that I don't really know what the ideal external head temperature should be. The fins at the middle of the side of my heads, about 5" below the "MOTO GUZZI" stenciled on the valve covers measure an average of approximately 250 degrees F. when I pull over at the side of the highway during a 3500-4000 sustained RPM ride. These reading were taken on a sunny day of about 80 degrees F ambient temperature. I've repeated it a few times and seen about a 20 degree differential, with a range of about 240 to 270 degrees at various times. I'll be bringing my thermometer with me this trip, which will give me a chance to also measure my buddy's Road King for comparison.

I do like your thinking on this subject, and we should try to get together and talk more about it. I only live about a hundred miles from you (I'm 15 miles south east of Philadelphia). Maybe we could get together some time for a Barley Session and talk Moto Guzzi wrenching. I'll leave contact information on my Home page.

Den.

 

[roadventure]

Hi Dave,

Maybe we could get together some time for a Barley Session and talk Moto Guzzi wrenching. I'll leave contact information on my Home page.

Den.

Dennis,

I would like that! I too am planning a ride on my California. I plan to start in Ocean City, MD (about 130 miles from home) and ride on U.S. Rt 50 across the country to Sacramento. From there I want to go north along the Pacific coast and head back east through the northern U.S. or Southern Canada. I don't have a schedule (except I will be gone for about three weeks) so this could vary somewhat.

I know, in reality, there is no true ideal air fuel mixture ratio. That is just an average, and a gross one at that. When I was working on getting my Yamaha Road Star (carb) running more efficiently the dyno was showing an air/fuel ration ranging from around 10:1 through 15:1. We selected jets that provide closest to 13:1 when running at a constant 3000 RPM, which was close to the engine speed at 65mph.

With computer controlled fuel injection and a closed loop exhaust monitoring I would think that one could get much closer to the best air/fuel ration at varying engine speeds and loads. I expect this is what Todd has done with his fueling solution for the California. Having the tools (computer precision) and the experience to interpret what they are trying to tell you makes a huge difference.

I just got back from a ~260 mile ride today and I must say, that engine put off some heat. But, then again, it was 94F today, so that ability to get much cooling at all wasn't very good. I am hoping I won't learn what this engine feels like in 110F ambient air temperatures.

 

[GTM®]

I recently did a little research about the ideal A/F mixture ratio and found numerous credible sources warn that there is no such thing, it's actually a range which is demand dependant. The correct ratios can vary from 11:1 on down to 17:1.

Stoichiometric Combustion puts AFR ~14.7:1 for water-cooled engines. Low side of 13.X:1 has been long proven for fuel/air-cooled motors by thousands of dyno hours/monitoring. I personally have hundreds of hours with Guzzi engines with this type of R&D at Dynojet in Vegas, not counting my time locally and on Cycle World Mag's dyno.