Any FI Experts Out There?

[MCRIDER007]

Can anyone explain what is going on with my fuel injection that I get both increased power and 15-20 percent better gas mileage with the temperatures are above 90 degrees? This was really apparent yesterday returning from WFO-4 on the North Cascades Highway and then riding down into the furnace they call Eastern Washington. Riding through the mountains it felt like I was a gear down in power, so much so I was wondering if I had a brake dragging. My riding partner said he hadn't noticed it on his bike and we really were not that high of elevation (between 3500-5000 feet). Once we got back in the hot temperatures I seemed to have a lot more power everywhere in the RPM range and the gas mileage went from 40 to 47. Conventional theory says cooler temperature results in denser air and more oxygen which in turns leads to more power (not sure about the effect of air temperatures on fuel economy). What is going on with the FI (or sensors) to make my bike run so much better in hot temperatures?

 

[radman]

Wasn't an increase in power at higher temps-it was an increase in power at lower altitudes. High altitudes reduce the amount of air the atmosphere can pump into your motor, the map sensor knows this, and adjusts the mixture as well. Back in the old days one rode a bike into the mountains and soon had no power left unless he re-jetted to compensate. No more. But the power loss at altitude is real-and the original reason the supercharger was invented, for use in aircraft-not to increase power, but to compensate artificially for power loss at high altitude. It was only later that some whizzo figured out that supercharging at sea level resulted in massive power increases. He also invented the "rod through the pan", covered in chapter 2.

 

[MCRIDER007]

Wasn't an increase in power at higher temps-it was an increase in power at lower altitudes.  High altitudes reduce the amount of air the atmosphere can pump into your motor, the map sensor knows this, and adjusts the mixture as well. 

Can you give any further explanation about the map sensor -- what inputs it uses and what it does?

I am used to riding in the high desert at 5-7000 feet elvations and am very aware of the power losses at those altitudes. Normally, the air contains about 2 and a half percent less oxygen per 1000 feet of elevation so if you go up 4000 feet you can expect about a 10 percent power loss. When I came down the mountain yesterday I think we only dropped about 2000 feet before hitting some pretty high temperatures but by then the "power" seemed to be fully restored. It seems like it had to be something in addition to lower elevations.

 

[radman]

MAP=manifold absolute pressure. You'll see it attached to the throttle rail with a vacumn line plugged into the bottom of it. Senses manifold pressure and regulates the injector pulse width accordingly. There is also a Intake air pressure sensor in the air cleaner assembly, which is responsible for generating a signal based on intake air volume, hence temperature sensitive. Strangely enough, my experience with Frank has been just the opposite of yours, when hot out, Franks performance suffers. However, the heat here is accompanied by high humidity, which displaces air and oxygen in volume, and may throw the whole mess off.

 

[ionbeam]

Perhaps it was the gas. In my town my gas comes as reformulated gasoline. The oxygenates are typically MBTE or methanol . If I drive .2 miles outside my town I can get un-oxygenated gas and my mileage and performance goes up immediately. Fuel requirements change from state to state and often within a state, perhaps you got a different blend.

Was this change in performance new or has it always been like this?

(As radman sez) Feejer has two air pressure sensors, Atmospheric and Intake air pressure. These can be checked through the Diag panel.

Just some thoughts.

Alan

 

[MCRIDER007]

Strangely enough, my experience with Frank has been just the opposite of yours, when hot out, Franks performance suffers.  However, the heat here is accompanied by high humidity, which displaces air and oxygen in volume, and may throw the whole mess off.

I would expect that performance would go down in high temperatures, especially with low humidity. Normally, the best conditions you can have (for performance) is to be at see level with cool temperatures and high humidity. Now I have a bike that seems to like high temperatures and low humidity, I am just wondering if I have some sensors that are malfunctioning in cool temperatures.

 

[MCRIDER007]

Perhaps it was the gas.  In my town my gas comes as reformulated gasoline.  The oxygenates are typically MBTE or methanol .  If I drive .2 miles outside my town I can get un-oxygenated gas and my mileage and performance goes up immediately.  Fuel requirements change from state to state and often within a state, perhaps you got a different blend.
Was this change in performance new or has it always been like this?

I don't think I can blame the gas for what I experienced since it all happened with the same tank of gas -- which I had previously filled twice at the same station.

I first noticed a dramatic change in gas mileage when I took a 3300 mile trip through most of the Western States and had varied weather conditions. The riding speeds were very consistent but the gas mileage was consistenty higher, sometimes over 50, when the temperatures were over 90 degrees. The elevations didn't seem to make any difference (in mileage) at all. If it was cool I got 40-43, when it was hot I got 48-52.

Yesterday was the first time that I rode in conditions where the temperatures changed so quickly, I am talking about 30-40 degrees in about 25 miles and that is when I noticed what seemed to be a 10-15 percent increase in power.

 

[ionbeam]

All the important sensors can be read from the Diag panel if you have a few minutes. Next time you are riding in the Twilight Zone take a short break and check it out.

Hmmm, when was the last time your air filter was checked? (shooting in the dark...)

Alan

[i love the cool weather in the spring and fall -- New England Dragway here I come. Cold air = quick ETs and good MPH right up until it gets too cold for good traction.]

 

[MCRIDER007]

All the important sensors can be read from the Diag panel if you have a few minutes.  Next time you are riding in the Twilight Zone take a short break and check it out.
Hmmm, when was the last time your air filter was checked?  (shooting in the dark...)

Thanks for the input. Diag panel??? Guess I need to re-read my owners panel. Air filter check -- haven't looked at the air filter but I only have 6900 miles to date and haven't ridden in any dusty conditions so I doubt that the air cleaner is the cause -- but I will look at it.

Update: I just looked at the air filter (and it only took the removal of one panel and three other pieces and 17 screws and fasterners) and it was clean.

 

[ionbeam]

Guess I need to re-read my owners panel.

Hmmm, that would be the FSM [Factory Service Manual P/N 5JW-28197-10]

 

[jestal]

del

 

[twowheelnut]

Ouch. My head hurts.

 

[MCRIDER007]

The best conditions for engine power are cool air temp and LOW humidity...not high
I cannot come up with any likely rational to explain what you describe..... 

Ah Jestal, nice to see your input on this forum. It seems like I remember that engines developed the most power in cool, moist conditions because the air was the most dense and contained the high concentration of oxygen but if you say that low humidity is the best then I better recalibrate my logic.

After pondering this thread for the past 4 hours I have come to the conclusion that what I thought happened yesterday could only happen if something is wrong with my bike's FI in cool riding conditions, there just isn't any way it could be running normal when cool and even better in hot weather. I am going to find some secluded stretch of road tomorrow and do a bit more of a scientific test than the seat of the pants dyno evaluation that I did yesterday -- provided we ever get some cool weather to perform a good comparison.

 

[markjenn]

Sorry, but the most likely explanation for all of this is an inaccurate butt dyno.

- Mark

 

[Constant Mesh]

The FJR has two air pressure sensors:

Intake air pressure sensor

Atmospheric pressure sensor

Is this intake air sensor a MAP sensor or is it measuring the intake air vacuum?

I assume when the key switch is on before the engine is started that both sensors would give the same pressure reading. Or maybe one is reading zero vacuum and the other the atmospheric pressure.

I've noticed on the Honda ST1300 that it has a MAP sensor but doesn't have an atmospheric pressure sensor -- it isn't shown on the electrical schematic. I've seen on a ST1300 forum some grumblings from riders that their bikes run poorly at higher altitudes -- particularly their idle rpm is erratic at higher elevations. Might the absence of an atmospheric pressure sensor cause this?

From the service manual of a 1992 Honda Prelude I once owned I noticed it had a MAP sensor but no atmospheric pressure sensor. But, when I looked a little closer I discovered that it did have an atmospheric sensor that was part of the ECM unit and not an external sensor with wiring to the ECM.

 

[MCRIDER007]

Sorry, but the most likely explanation for all of this is an inaccurate butt dyno.

It could be an inaccurate butt dyno and it could also be that I can't tell the difference between riding uphill and riding downhill but it really didn't seem to make any differance, the FJR seemed to down on power going up or down. I don't think I have shifted so much to pass slow moving traffic since I was riding 750s. I probably would not have noticed so much if there was no traffic to pass.

After reading all the technical comments I have received, it makes me wonder if it was altitude related, the inherent loss of power at altitude combined with a FI system that is not compensating for altitude but the highest point on the NC Highway (Washington Pass) is only 3700 feet higher than Winthrop (and 67 miles away) and my power problems did not go away until I hit the heat which was about 25 miles from Winthrop. I felt like a fried egg but the FJR was running great.

Anyway, I am going to resolve this cool vs. hot temperature power question with some high gear full throttle roll ons between 2 fixed points. I just established a baseline at 79 degrees and am going to try and do a comparison at 60 degrees and 95 degrees.

 

[jestal]

del

 

[MCRIDER007]

Sorry, but the most likely explanation for all of this is an inaccurate butt dyno.

Anyway, I am going to resolve this cool vs. hot temperature power question with some high gear full throttle roll ons between 2 fixed points. I just established a baseline at 79 degrees and am going to try and do a comparison at 60 degrees and 95 degrees.

I completed my high gear "roll on" performance comparisions at 66 and 94 degrees and it appears that my FJR actually does run stronger at high temperatures, at least between 4000 and 6000 rpms. The difference is not great, about 4mph after about 200 yards, but it is the opposite of what one would expect since the air is about 5 percent less dense at the higher temperature. It seemed like most of the power difference was in the 4000-5200 rpm range because there was a substantial power spike at 5200 rpms at all temperatures.

I also did a comparison of how long it took to go from 3000 to 5000 rpms and the results were similar, the FJR was faster at 94 degrees.

Any theories regarding air/fuel mixtures or inaccurate sensors that could explain what is happening?

 

[Geezer]

Just wondering, have you done the Barbarian jumper modification or done anything to modify the ECU?