| Author | Message | ||
     Jlnance |
A question for all you gearheads. Everyone "knows" that a dirty air filter will hurt your gas mileage because the dirt restricts the flow of air. Now, right in the center of your throttle body or carburetor throat is a butterfly valve, which is there specifically to restrict the flow of air. And the more it restricts, the better your mileage. So what gives? | ||
| Beachbuell |
As you open the throttle (give it gas), that butterfly valve also opens, thus in turn letting more gas into the mix. The faster you go (twist the throttle) the more the valve opens, the more gas you use. So, if you drive like grandma (butterfly valve not opened much) the better your mileage or less gas is used. If you on the other hand ride like Miguel Duhamel (butterfly valve wide open) more gas is used, lesser gas mileage. Make any sense ? | ||
| Glitch |
So what gives? Think of it as a throttle for air. You don't want full on gas all the time. Same goes with air, you don't want full on air all the time either. | ||
| Kdan |
Well, you need full on air if you've got full on gas. Of course when you add less air, the magical properties of the throttle body reduce the fuel flow simultaneously! | ||
| Blake |
I don't know that a dirty air filter will hurt fuel mileage. Actually, I doubt that it does. I know that a dirty filter can hurt engine power output. | ||
| Newfie_buell |
A dirty air filter is kinda like someone shoving a sock in your mouth....... OR someone holding their hand over your mouth and nose. OR someone with asthma without their puffer. It just can't breathe | ||
| Midknyte |
sitting in a strip bar without your glasses OR | ||
| Newfie_buell |
Now Midnyte the solution to that one is to get reeeeeeeaaaaaaaaaalllll close. | ||
| Tramp |
....or getting a lap dance while you're wearing hockey goalie armour..... | ||
| Doon |
Tramp, that is the only way my wife will let me get lap dances now | ||
| Tramp |
that's odd- she lets me have 'em regardless of what I'm wearing  | ||
| Swampy |
Or like restricting the flow throught the carburetor and causing the vacuum to rise in the intake trac, enrichening the fuel charge to the engine. Or in the case of fuel injection making the engine think its under load and enrichening the fuel delivery to the engine. The butterfly restricts the air flow down stream from where the fuel gets intoduced(with the carb) | ||
| Tramp |
dude- enough with the double-entendres, already..... it was only a lapdance..... | ||
| Court |
You said a double-intended? How many times? | ||
| Jon |
Ooh...they're talking French! Let's listen... | ||
| Pammy |
OK, lets say that fuel has to have air to burn, capice?(throw a little eye-talian in there for you Jon) In the case of fuel injection, the bike is equipped with a TPS which has direct input into your ECM which translates to your injectors the amount of fuel to deliver to your engine. The further open the throttle, the more fuel will be delivered(as translated by the TPS). In parallel with this occurance, the throttle plate will(manually) open to allow more air to, in turn, aid in the burning of the fuel. If there is a restriction beyond that, of say the air filter being clogged, the air/fuel mixture will be inappropriate and could result in the wasting of fuel(unspent). It could/will also cause some premature fouling of plugs(ineffecient burning of fuel, furthermore) | ||
| Pammy |
A mass air flow sensor would help with the situation. | ||
| Blake |
As would an O2 sensor and the resulting adjustment to the AFV.  | ||
| Jon |
Wow. I'm impressed. MOVE OVER SPOCK! PAMMY'S THE SCIENCE OFFICER OF BADWEB!! More Romulan Ale please...with a twist... | ||
| Oldog |
You neglected to mention the 13,000 feet of wire connecting all of the various "do-dads" [ I think that is a technical term ] - an dat fuel pup thing in da tank, Cain U-uns gets a MassHairflow senser to hook up to da 'puter- "Mountain ese" | ||
| Rocketman |
It's worth noting so as not to confuse yourself about actual fuel quantity delivered (actually, it may confuse you thinking about it, lol) , the TPS is not the governing factor. It gets a little more involved beyond the TPS. A TPS sensor will only tell if the butterfly is closed, wide full open, or anywhere between closed or wfo. Between closed and wfo there is no way of knowing exactly where the butterfly position is from TPS input. Please note, I am by no means a F.I expert. I rely upon diagnostic equipment and the correct publications when I'm fixing such problems. Rocket | ||
| Tramp |
onthemoney.rocket.  our "science director", Pammy, is a tad mistaken. if the TPS (THROTTLE position sensor) were the governing factor in actually setting throttle position....it would be a self-cancelling interaction. think about that... actually, your 02 sensor has far more to with reading your rate of burn than does your TPS. Please note: I AM a bosch-certified FI (K-Jet, L-Jet, Lambda, regina, etc.) technician, with a very long history of working with FI, from VWs in the '70s, to the present... half an education is a very dangerous thing, esp when it comes to electronic management on motorcycle systems. (Message edited by tramp on July 12, 2006) | ||
| Sparky |
So, what about the converse of a dirty air filter -- "No" air filter or, practically speaking, a filter that filters but offers no restriction? Better mileage or worse? More power or less? I'm thinking that these answers would show up in a dyno comparison of a bike with and without a (clean) air filter factoring in monitoring fuel consumption. Anybody done this? | ||
| Blake |
Tramp, It depends upon which mode of operation one is discussion. In open loop mode, the O2 sensor does nothing and the TPS is very influential in determining fuel delivery. Being owner of a racing and high performance shop, don't blame Pammy for ignoring the closed loop mode. | ||
| Hootowl |
I'm pretty sure the TPS sends an analog voltage to the ECM to tell it exactly how far the throttle plate is open. If it only told the ECM that it is either open or closed, the exact position of the TPS within the throttle body and the elaborate TPS reset/zeroing/offset value storage procedure would not be so critical in making the FI bikes run well. Also, my understanding is that the air pulses in the intake tract are too great to make use of a mass air sensor. The "wind" across the wire is not constant enough to accurately determine the amount of air flowing into the engine, hence the use of the O2 sensor equipped speed density system. Jeff | ||
| Tramp |
you missed the point- the TPs does send intel....it tells the ecm what the throttle position is... it doesn't utilize strictly the throttle position to vary the ratio. saying that the throttle position sensor tells the brain what position the throttle is at, and it uses that info to change the position of the throttle is very commonly misapplied circular 'logic'. we're all aware that the tps is, indeed, influential in dictating fuel delivery. trouble is, it does this through means aside from strict throttle postion...unless you're under the impression that it's a cis system, which it is not. throttle position dictates air ratio, as well. injection is simpler to understand, for the most part, than is carburation. (edited so as not to offend anyone) (Message edited by tramp on July 12, 2006) | ||
| Hootowl |
No, I get that part. Your right hand determines how far the throttle is opened, the TPS just tells the ECM how far you have decided to open it. "there is no way of knowing exactly where the butterfly position is from TPS input." I believe this to be incorrect, the TPS does indeed tell the ECM EXACTLY how far the throttle is open. Jeff | ||
| M1combat |
Yeah... Doesn't the TPS "sense the position of the throttle"? Once it does that... Does it not tell the ECM about it? Once that happens, does the ECM not then tell the injectors how many ms to spray? Of course that's assuming steady throttle... The Buell EFI (and I'm sure many others) will also track movement in the throttle so it can get a jump on what it thinks you'll do next. Like when you whack open the throttle, it kind of assumes you're headed for WOT and gets a head start on the fuel delivery so to speak (like an accelerator pump of sorts...). I could be wrong. If I am, I would rather be right. Please splain this to me . I don't care if you have certs or not... Just be right  . | ||
| Tramp |
hootowl- i didn't pen the part you believe to be incorrect. as to the other part, 'someone' is confusing their cause and effect. | ||
| Tramp |
m1- you've posted nothing there that contradicts what i've posted, nor that i would contradict. what the TPS intel does NOT do is reset the TPS or the butterfly, themselves. 'someone' is confusing fuel volume for throttle plate/butterfly position. get it? of course, in discussions where credibility can be purchased, all bets are off. |
