Air temp sensor vs mpg question

badger · 04-06-2005, 06:15 AM

How does the air temp sensor affect the Motronic system? Could it switch the system between open and closed loop? The reason I ask is, this winter, I consistently got 31-32 mpg regardless of how I rode. The last 2 tanks have been 36 and 38 mpg respectively. Most of my riding lately has been commuting to work in the morning and home in the evening. Just curious

roger albert · 04-06-2005, 07:22 AM

No, has nothing to do with open and closed loop.
Will run richer though, so if you're on the throttle a lot, you
should see less mileage, assuming you're holding the throttle about
the same. 38 to 31 is a stretch, but 32 to 36 is not much more than 10%, and is pretty plausible.

peakrunner · 04-06-2005, 09:47 AM

Could also have something to do with "Winter" blended fuels. They sucks so hard!

badger · 04-06-2005, 10:03 AM

Just filled up. 39 mpg. All riding in temps above 45F. In the winter (when I was getting 31-32), the temps were rarely over 32F and usually around 20-25F in the AM and 28-32F in the evening.

acook · 10:27 AM

I must be living right my 03 gets 46 to 48 mpg . I allways check every time I fill-up. Last check was 164.9 mi gas light wasn't on yet. I pumped in 3.373 gals. This is commuting in LA traffic 150 miles a day. This has been this way since I bought it. Only mod is cat removal other wise it's stock. 14,400 miles on the clock.

roger albert · 04-06-2005, 12:28 PM

Yeah, those mileage figures are much lower than I see too.
I was only commenting on the seasonal difference, but sure,
they're low in general for anything other than a constant thrash.
Good point on the fuel. I wonder...

badger · 04-06-2005, 12:39 PM

I've gotta check if the bike still has the CCP. I'm the third owner of the bike. The second owner didn't really know much about it. Only rode it 2K before selling it. Since then, I've found out it has KN filter, superduct intake, hyperlites (I knew it had Ohlins, clear lenses and Suburban high bar kit, and peg kit when I bought it.)

JonyRR · 04-06-2005, 01:12 PM

a somewhat clogged OEM-type K&N and having the CCP pulled (to put the machine in 'open loop' mode, disregarding the 02 sensor input at steady-state throttle opening) can cause some mileage drop, as well as having a rich mixture indicated on the plugs, and more chance of carbon deposits....combine that with 'winter blend' , 'oxygenated' fuel (oxygenated by alcohol, ie gasahol) and I'm not surprised to see a mileage drop. I read somewhere here that a flowbench test revealed the OEM-type K&N flowed LESS than a stock air filter (I believe that was from Erion Flory, if my short-term-damaged memory serves)...

jduke · 04-06-2005, 01:13 PM

Also, do you spend more time warming the engine in during the winter rides?

Anton · 04-06-2005, 02:35 PM

I've always seen worse mileage in winter. Usually on carberated bikes with big jets. I always assumed had to do with the fuel not atomizing completely and not fully burning.

badger · 04-06-2005, 05:03 PM

Quote:

Originally posted by jduke
Also, do you spend more time warming the engine in during the winter rides?

I get on, pull up the enrichener thingy, start the bike and go. After about 3/4 mile, I turn off the enrichener thingy. When warm I don't use the enrichener thingy.

My K and N is the power filter version. Looks like more surface area than the standard air filter.

gdobler · 04-07-2005, 09:23 AM

I didn't think the "enrichener thingy" actually enriched anything. Correct me if I'm wrong, isn't it a fast idle thingy?

Anton · 04-07-2005, 09:37 AM

I believe all the enrichener thingy does is move the throttle stop up.

badger · 04-07-2005, 10:02 AM

Quote:

Originally posted by gdobler
I didn't think the "enrichener thingy" actually enriched anything.

It enriches my cold starting experience...

Ole Bike · 11-09-2005, 05:58 AM

Quote:

Originally posted by badger
How does the air temp sensor affect the Motronic system? Could it switch the system between open and closed loop? The reason I ask is, this winter, I consistently got 31-32 mpg regardless of how I rode. The last 2 tanks have been 36 and 38 mpg respectively. Most of my riding lately has been commuting to work in the morning and home in the evening. Just curious

Cold air is denser and so the ECU should cut the fuel; but this should not affect mpg. It is possible the ECU maps just aren't too precise for winter driving. ????

Lots of other winter differences such as amount of time for fuel to evaporate, fewer easy rides in the countryside, loss of whatever Stabil restores, humidity in air, oil thickness, grip heaters (.05 HP), etc.

SergioK · 11-09-2005, 06:48 AM

I've found almost all engines like colder temps. The cold dense air packs in more O2, more air, more fuel, more of both, more power, thus I tend to get into the throttle a bit more. Yes, I admit it, I like power and it feels good.

roger albert · 11-09-2005, 08:06 AM

> Cold air is denser and so the ECU should cut the fuel

on the contrary

The Sea Dog · 11-09-2005, 03:20 PM

The "enricher thingy" is merely a fast idle lever, no change in fueling, the motronic takes care of that for you. If my slightly dodgy memory serves me correctly there is however a barometric sensor in the mortonic mix somewhere. . . . . .

Regardless of how much I "give it the berries" my average still doesn't dip below 40 mpg, that's real proper Imperial gallons mind, not those imitation things that you guys have over there

That's with Induct, and Staintunes 2-2 full system, though it was the same before with just the Remus cat eliminator and standard cans.

Even really thrashing the tits off it, never less than 39/40, but usually with fast road riding it's 48-52, lots of advanced obs' smooth and flowing, little braking, does it for me !

Toodle Pip

shovelstrokeed · 11-09-2005, 03:53 PM

There is no air density measurement.
Cold air is denser but that requires more fuel not less.

Air density is inferred from Air temp/barometric pressure measurement but that can be off an easy 10% as humidity is not accounted for anywhere.

Now add that fuel varies in specific gravity and the EFI makes no compensation for that so a lighter fuel flows more for a given injector pulse and up goes fuel consumption. More fuel related is that the oxygen improved fuels have less BTU/lb than regular old dead dinosaurs and you have your answer, kinda.

roger albert · 11-09-2005, 04:44 PM

> Cold air is denser but that requires more fuel not less.

exactly, That was the point that I attempted to make.

Damn, I'm still learning the stuff Ed knows. Lots of catching up to do. I just started to play with humidity while jetting a pocketbike a few weeks ago. Temp was stable from mid morn to late aftn, but jetting changes were required. Oldtimer explained I was ignoring humidity. I looked at some old notes from school afterwards and there it was. For whatever reason, that element had never really stuck in my mind. I'm finding gaps in my understanding a lot faster than I can patch them.
Damn.