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Old 05-17-2013, 07:38 AM   #241
roger 04 rt
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Originally Posted by JRose View Post
How are you guys getting such good gas mileage to begin with!?!?

I'm at a steady 44mpg, and I'm still following break in!
In the case of my example, I'm just using the book figures for a steady 56 MPH. Who ever drives like that? Still it gives me the numbers to explain what's happening. My rationale applies to every power configuration.
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Old 05-17-2013, 10:58 AM   #242
ebrabaek OP
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Originally Posted by roger 04 rt View Post
While you're getting a test LED for the Secondary Air Sensor (unless, in the unlikely event, it turns out to be some twisted implementation of a crankcase ventilator), here's why you report better gas mileage even though you have more fuel dialed-in to the PC V.

What I say is that you're getting about the same MPG (which is pretty good since your engine is running much better), and your computer is erroneously reporting better gas mileage.

The Short Story
Assuming a 10% richer mixture: 1) mileage is the same because the extra fuel injected is converted to power at 50% efficiency--meaning 10% more fuel equals 5% worse gas mileage. However, you will naturally run in a higher gear some of the time offsetting the 5% loss. 2) The fuel computer calculates that it is using 10% less fuel than than it is so it reports 10% better gas mileage.
Could be that some do ride in higher gear, but I do not., or should I say have not.


The Detail

Spec: F800GS at 56 MPH, 62 MPG (your mileage may vary )

For the sake of example let's say that a mileage test-run is made at a steady 56 miles per hour. Whether or not you have a PC V installed it takes about 9.3 horsepower to go 56 MPH on bikes like these. Based on the F800GS spec at 56 MPH, it will use 0.9 gallons per hour. You can then calculate the BSFC (brake specific fuel consumption--lbs. per hp per hour) as 0.9 gallons which is 5.4 lbs. divided by 9.3 HP, for a very respectable 0.58 lbs./hp/hour. This is consistent with many gasoline engines.

Now add 10% to the fueling and you will find that the BSFC increases about 5%. The reason is about half the added fuel finds unburned oxygen to mate with and engine produces 5% more power. So BFSC is now worse at 0.61. That's the first half of the story.

Next, an 85 HP engine that's cruising at 9 HP, has a throttle opening of 15-20 degrees (est.) so it wastes a lot of energy creating manifold vacuum (aka pumping losses). When you ride in a higher gear, the engine turns more slowly so it has to make more torque to produce the same horsepower (fifth gear requires 13% more engine torque than 4th on an F800GS). To make more torque you have to open the throttle more, as a result, the pumping losses go down (slightly lower manifold vacuum) and so does the BSFC--meaning better miles per gallon.

So the added fuel increases BFSC but the higher gears sometimes reduces BFSC for a net result of no real change to mileage.

As far as why the fuel computer is reporting better gas mileage, here's my explanation. The fueling computer calculates gas mileage by: 1) knowing the injector flow rate (the tolerance is pretty tight), 2) counting the miles driven since the fuel computer was reset, 3) adding up how long the injectors have been turned on since reset, and 4) dividing that (3) into the miles driven.

When the PC V adds (for example) 10% to the injector pulse the fuel computer doesn't know it, and underestimates the total fuel used by that same 10%. If your mileage was 60 MPG it will now be displayed at 66 MPG. (If you use an LC-1 to shift lambda and richen the fueling, the fuel computer displays correctly since the BMSK is still in control of the pulse length. )
I am not getting the same gas mileage. I am getting 3-5 MPG better mileage. It is really quite simple.... It took an awe full lot of throttle to move the bike at a given environment, and now with fuel, and air better mixed for power, it now takes less throttle to move the same bike+rider. The MPG read out is verified by miles driven divided by Gallons filled in the tank. First I was cautiously optimistic, but then as the miles went by, it became clear to me that the fuel consumption had gone down a little, specially in the 40-50 MPH dirt roading. It is not an error. While I agree with your assesment above, that is primarily based on the higher gear/lower rpm. That is not the case with me. But simply average riding....town....rural.....dirt...Lots of dirt....etc.
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Old 05-17-2013, 10:59 AM   #243
ebrabaek OP
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Originally Posted by JRose View Post
How are you guys getting such good gas mileage to begin with!?!?

I'm at a steady 44mpg, and I'm still following break in!
I don't know.....All I can report is what I get, or should I say, is getting with this setup. Sorry.
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Old 05-17-2013, 12:18 PM   #244
roger 04 rt
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Originally Posted by ebrabaek View Post
I am not getting the same gas mileage. I am getting 3-5 MPG better mileage. It is really quite simple.... It took an awe full lot of throttle to move the bike at a given environment, and now with fuel, and air better mixed for power, it now takes less throttle to move the same bike+rider. The MPG read out is verified by miles driven divided by Gallons filled in the tank. First I was cautiously optimistic, but then as the miles went by, it became clear to me that the fuel consumption had gone down a little, specially in the 40-50 MPH dirt roading. It is not an error. While I agree with your assesment above, that is primarily based on the higher gear/lower rpm. That is not the case with me. But simply average riding....town....rural.....dirt...Lots of dirt....etc.
Well I would never argue with you about your measurements. Miles driven and gallons put in the tank. On the other hand I don't see any way that your fuel computer can read correctly. It just doesn't have a way to account for the added. To be sure, I checked with Dynojet today. They confirmed that your fuel computer will not read correctly if you add fuel.
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Old 05-17-2013, 12:43 PM   #245
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Originally Posted by roger 04 rt View Post
Well I would never argue with you about your measurements. Miles driven and gallons put in the tank. On the other hand I don't see any way that your fuel computer can read correctly. It just doesn't have a way to account for the added. To be sure, I checked with Dynojet today. They confirmed that your fuel computer will not read correctly if you add fuel.
Fair enough...... So with that in mind..... How can this be plausible..... Is there something to the pulse length controlled by by the BMS-K, vs the higher volume demanded from the PC-5....??? I am stumped, as they clearly agree. Another thing is that I would see the low fuel light come on about 170-180 miles..... I now see it 180-190. I understand what you are saying, and are neither trying to be arrogant about this, merely just posting my findings. Have not gotten to the SAS light yet. Still working the studio.
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Old 05-17-2013, 02:19 PM   #246
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The BMW fuel mpg computer is cumulative. It just keeps adding fuel mileage to what is stored since the last reset and averaging it out. Reset at every fill up and mine is reasonably accurate, to within a 1 or 2 miles per gallon.

When the bike was new, I routinely got 57-58 mpg riding around my rural area. Now it is down to 54mpg, but I have an accelerator module and probably twist the throttle more. I don't know why anyone should get 44 unless they are doing a lot of freeway miles. The mileage does drop off quickly at those speeds.
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Old 05-17-2013, 02:35 PM   #247
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Just a couple observations having no meaning to your mileage anomoly. Looking at the fuel trim table (3), there is little fuel added between 4250 and 5000 RPM. There is very little to no fuel added betwwen 0 and 10% throttle opening. I have no idea how that corresponds to the way you ride. I do know this. I can go go from 51 mpg to 36 mpg with throttle manipulation. The biggest influence to my fuel mileage is my right wrist and if I see a 10 mile per tank or 2.5 mpg difference it is of no significance to me.

While I got ya, I was wondering. Back in the day I was involved with some small time auto racing guys fooling around with motors meaning I understand the value of a Dyno for the track. The Power Commander with Autotune is advertised as a device for those wishing to forgo the Dyno expense and such. If, and I mean if, one is going to accept the Autotune map, other than a piece of paper charting torque and horsepower, what value is the Dyno? One can run a Dyno tune today at 80 degrees with 10% relative humidity, tomorrow run at 60 degrees and 90% relative humidity with different results and different tunes. If we are going to plug in 13.2 or 13.5 and let it do its thing the value of the Dyno is lost as the A/F R will try to maintain the setting. Maybe there is value having a Dyno map, flipping a switch to the Autotune map, I do not know. Real world is different than a Dyno, even NASCAR changes the programming in the ECU to match conditions before the race not relying on the Dyno set up back at the shop.

It is interesting to note that only one cell, 15% throttle at 4500 rpm took fuel out. Not much can be done regarding both cylinders running the same map due to having one Lambda sensor.

This is the best technical thread going right now, I am very interested in the different opinions, results, and us all working this out in such a friendly manner. Wonderful.

Terry





Quote:
Originally Posted by ebrabaek View Post
OK Roger....
Here are the three screenshots.....
Fuel Map, which is a base map only to correct for the idle hop of the 8GS.....



Then Target AFR.....



Then finally the trims after a few K miles.....
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Old 05-17-2013, 03:52 PM   #248
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Originally Posted by terryckdbf View Post
Just a couple observations having no meaning to your mileage anomoly. Looking at the fuel trim table (3), there is little fuel added between 4250 and 5000 RPM. There is very little to no fuel added betwwen 0 and 10% throttle opening. I have no idea how that corresponds to the way you ride. I do know this. I can go go from 51 mpg to 36 mpg with throttle manipulation. The biggest influence to my fuel mileage is my right wrist and if I see a 10 mile per tank or 2.5 mpg difference it is of no significance to me.

While I got ya, I was wondering. Back in the day I was involved with some small time auto racing guys fooling around with motors meaning I understand the value of a Dyno for the track. The Power Commander with Autotune is advertised as a device for those wishing to forgo the Dyno expense and such. If, and I mean if, one is going to accept the Autotune map, other than a piece of paper charting torque and horsepower, what value is the Dyno? One can run a Dyno tune today at 80 degrees with 10% relative humidity, tomorrow run at 60 degrees and 90% relative humidity with different results and different tunes. If we are going to plug in 13.2 or 13.5 and let it do its thing the value of the Dyno is lost as the A/F R will try to maintain the setting. Maybe there is value having a Dyno map, flipping a switch to the Autotune map, I do not know. Real world is different than a Dyno, even NASCAR changes the programming in the ECU to match conditions before the race not relying on the Dyno set up back at the shop.

It is interesting to note that only one cell, 15% throttle at 4500 rpm took fuel out. Not much can be done regarding both cylinders running the same map due to having one Lambda sensor.

This is the best technical thread going right now, I am very interested in the different opinions, results, and us all working this out in such a friendly manner. Wonderful.

Terry
Thank you sir for that great observation. I too agree with that, and like to contribute it to all of us, most certainly Roger, as he have me outgunned, flanked, and powered, with his knowledge of the subject. All too often do you see people hacking at each other, and the message vanishes. I can only speak for myself regarding the dyno. I am a very skeptical person. I am not one to buy snake oil, and for one wanted to align myself with a trusted source (SSW/Epic Motorsports) Eddie have tuned with the Dynojet system for a very long time, and his bikes winns races. But.... therein lies, or so I though, lies the issue. I don't wanna race..... Just explore the dirt. So I presented the case to him, that power would be good, but control ,and efficiency was more important. And onward we went. Fast forward... I wanted the dyno to prove to me, that this stuff works. We all know the butt dyno, but only way to either document success, or failure, is to dyno before....during, and after. Make sure that we understand where the 8GS was with regard to fueling, before the install. We ran it, and I am very satisfied. This is one of the few cases, that the stuff you read actually is true. That said, do you need to dyno it now..... NO. If you trust my judgement on the subject, then I did the work, and paid for the "independent" research, and you can just go with the same map, as I have, and you should see about the same results ( providing you have the headers+pipe installed). The thing I like the most, is the easy way you as the end user can interface, and change the mapping, to suit. Perhaps as Roger briefly touched on, that the mapping is rudementery, but again end user friendliness, is great, and if you can use a flaptop, you will feel right at home.
Cheers....
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Old 05-17-2013, 03:56 PM   #249
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Originally Posted by roger 04 rt View Post
... To be sure, I checked with Dynojet today. They confirmed that your fuel computer will not read correctly if you add fuel.
Roger, did Dynojet have anything to say about their technology works with the SAS?
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Old 05-17-2013, 03:57 PM   #250
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Excellent explanation Erling, thank you.

Terry
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Old 05-17-2013, 04:03 PM   #251
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Excellent explanation Erling, thank you.

Terry
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Old 05-17-2013, 07:19 PM   #252
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Roger, did Dynojet have anything to say about their technology works with the SAS?
Very good question. I didn't ask them because it is now apparent to me that if the sas solenoid is on so that fresh air can flow into the exhaust it will affect the O2 sensor.

The bigger question now is when (under what conditions) is the solenoid energized? Hopefully EB or someone else will do some riding with a test LED installed.
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Old 05-17-2013, 07:28 PM   #253
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Originally Posted by ebrabaek View Post
OK Roger....
Here are the three screenshots.....
Fuel Map, which is a base map only to correct for the idle hop of the 8GS.....



Then Target AFR.....



Then finally the trims after a few K miles.....
Thanks again for posting these. Also, I think we've talked enough about the issues related to mileage for now.

Is there one more map which is the result of the dyno tuning? Could you add that too? If you want to try some auto tune experiments you could ride with that map, put Autotune into the mode when it collects trims but doesn't apply them. With the sas valve off that would let you see you close the dyno map is to the target AFR map.
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Old 05-17-2013, 08:54 PM   #254
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Originally Posted by roger 04 rt View Post
Thanks again for posting these. Also, I think we've talked enough about the issues related to mileage for now.

Is there one more map which is the result of the dyno tuning? Could you add that too? If you want to try some auto tune experiments you could ride with that map, put Autotune into the mode when it collects trims but doesn't apply them. With the sas valve off that would let you see you close the dyno map is to the target AFR map.
I asked Eddie ( SSW Tuner) to leave the base map as a " zero map" as I did not want to impact the Fuel mileage....Just correcting for the off idle hop. He then after riding the dyno many times, and many power pulls, filled in the AFR based on that, and trying to create economy around cruising. He liked what he saw, and that afr, stuck'ed, as it was the power maker. I will try to get to the SAS tomorrow.....
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Old 05-18-2013, 06:15 AM   #255
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Originally Posted by ebrabaek View Post
OK Roger....
Here are the three screenshots.....
Fuel Map, which is a base map only to correct for the idle hop of the 8GS.....



Then Target AFR.....



Then finally the trims after a few K miles.....
Quote:
Originally Posted by ebrabaek View Post
I asked Eddie ( SSW Tuner) to leave the base map as a " zero map" as I did not want to impact the Fuel mileage....Just correcting for the off idle hop. He then after riding the dyno many times, and many power pulls, filled in the AFR based on that, and trying to create economy around cruising. He liked what he saw, and that afr, stuck'ed, as it was the power maker. I will try to get to the SAS tomorrow.....
This is making more sense to me now. Looking at 2% and 5% throttle, 1250 and 1500 RPM, the base map is +20%. The Trim map (which I'm assuming is not additive in the mode you're running but may be additive in the non-real-time PCV mode) has 25, 19 and 0, -13. What is the adjustment Trim limit programmed to on your PCV software?

This suggests the following to me: the 25 has hit a limit, the 19 has adjusted toward your 13.5 AFR for that cell. The 0 tells the Autotune not to adjust, don't know why it is there. -13% suggests that either a) this table is additive to the Base map and that it takes 20% minus 13% to hit your 13.5:1 AFR target (very reasonable) or that b) it takes 13% less fuel than stock to hit your 13.5 target (not a reasonable assumption). If I were you I would want to figure out for sure if the tables are additive.

When does the Off-Idle Hop that you mention occur? I guess it's after deceleration. I should program my LC-1 to 11.8:1 to see what happens on my bike with that annoying post decel, throttle on. This is a nasty side effect of overrun fuel cutoff.

I'd be interested in comparing the Trim table now to the Trim table when it first came off the Dyno. Can you post a copy of the original?

I'm thinking that all the Trim values of 10 were set by your tuner and that you have not got enough time in those cells for Autotune to adjust them.

RB
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