| Author | Message | ||
     Swordsman |
This could possibly be a Knowledge Vault topic, but it's more of a "why" than a "how" question, so I dunno. If it's in the wrong spot, I apologize. There are a few things about the XB that I don't understand. 1.) I keep hearing that the cooling fan has something to do with emissions, that without it the bike would need a catalytic converter, or need to be water cooled to meet emissions requirements. I have absolutely no clue on this matter. Why would air cooling have any effect on emissions??? 2.) Why does the TPS ever need resetting? Once the correct position has been established, what causes it to get out of sync again, if everything is electronically controlled? I think I had another question, but I can't remember what it was at the moment. Thanks for any input! ~SM | ||
| Swordsman |
Oh! I just remembered the other question! If I'm not mistaken, the aftermarket exhausts don't have the servo that controls back pressure. That servo is obviously there for a reason... isn't there some negative effect from removing it? Thanks! ~SM | ||
| Darthane |
1) The base reason for the fan is to keep the rear cylinder at a manageable temperature. The reason it runs when the engine is off is to keep from 'cooking' the oil that's sitting in the head, no longer being circulated by the engine. 2) Normal wear and tear means that over time the throttle plate seats itself differently. Could you go 100K miles without ever resetting it? Possibly, but chances are your bike would run better if you had. 3) Depends on your definition of 'negative'.  | ||
| Swordsman |
Darthane: "1) The base reason for the fan is to keep the rear cylinder at a manageable temperature. The reason it runs when the engine is off is to keep from 'cooking' the oil that's sitting in the head, no longer being circulated by the engine." Well, I know it's for temp management, what I'm curious about is why it would have any impact on the emissions? I read that in a thread just yesterday, and I've read before that there was some debate over making them water cooled for emissions reasons. I don't understand why temperature affects emissions, or if it really does. I'm assuming it does, since it keeps coming up. ~SM | ||
| Fdl3 |
Darthane said it best and more to the point. If you STILL want additional ramblings... 1a) I have never read that the fan had anything to do with emissions. I cannot see how it could since it has no bearing on the actual combustion process. I always understood the purpose of the fan was to draw air to the rear cylinder due to it being blocked from the primary airflow by the front cylinder; and it comes on after the bike is shut off to help prevent oil "coking"/"cooking" in the rear cylinder head. Meeting emission standards has more to do with the efficiency of an engine's combustion process, not whether the engine is liquid-cooled and/or has a cooling fan (although there could be indirect benefits). 1b) For some reason, people have equated the idea of liquid-cooling being *necessary* to pass emissions, or to meet some future emissions demand. This is hogwash, as evidenced by the current Buell engine (and certainly others I am sure) meeting current and future emission requirements without the aid of liquid-cooling. It is noteworthy that the Buell engine does so without a catylic converter! Other liquid-cooled engines cannot do so without a catylic converter. It seems that using liquid-cooling has become a "quick-and-easy" attempt to meet emission requirements, rather than tackling the root problem - more efficient combustion. If an engine were more efficient at burning off the gas/air mixture, there would be no need of a catylic converter - the sole purpose of which is to burn off any gases not originally burned off by the engine. If we allow the EPA to force/mandate liquid-cooling in an effort to control emissions, we have only ourselves to blame... 2) Physical wear and tear of hardware components may require periodic TPS resets. 3) As I understand it, the purpose of the exhaust servo is to better preserve low-end torque characteristics under low RPM loads. As the RPM load increases, the servo opens up so that airflow is not impeded to the point of hurting top-end performance. If one seeks all-out top-end performance, I could see the servo possibly being a "negative". Edited: You see, I like to spell "efficient" like "effecient". I don't know why. It is just a quirk of mine, I guess. If we are honest, we all have specific words that trip us up. To this day I still have trouble knowing when to use "affect" versus "effect".  (Message edited by fdl3 on July 21, 2006) | ||
| Staindus |
Out of curiosity could you use the stock muffler with the Race ECM/Airfilter? | ||
| Perry |
A water cooled engine has more consistent temperature, therefore the tolerances can be tighter - parts expand/contract less, or perhaps just more predictably. And air cooled engine has to be engineered to deal with a wider temperature range, and some of those allowances force tradeoffs (engineering is always tradeoffs) that may not be in the best interests of emissions. Strict emissions requirements tend to force a leaner air/fuel mixture so that all the fuel is completely burned. This in turn creates more heat... which may necessitate a fan. Without the fan, the air cooled engine would presumably have to be designed to either tolerate more heat, or with some other changes to run cooler - and these changes may in turn cause emissions problems. Before someone flames me please note I'm not arguing that water cooled is better for emissions, or that the fan is or isn't required for emissions - only trying to point out some of the engineering tradeoffs between heat, emissions, cooling technology, costs, aesthetics, etc. that point out how the fan MAY arguably have an effect on the issue. Personally, I think without the fan the bike would have to be designed to have more airflow around the rear cylinder - meaning some more ugliness. | ||
| Diablobrian |
yes, but on the 12 you would need to tie or pin the flapper in the open position since the race ecm does not use it. | ||
| Staindus |
So on a 9 you wouldnt have to pin the flap? Are there any down sides to doing this Diablo? Sorry if this was already discussed. I looked in the KV but the search kinda stinks. | ||
| Diablobrian |
there is no valve/flap in the stock 9 pipe just watch your plugs, you may run a little rich in places in that configuration. | ||
| Wademan |
I had a guest professor come in to our energy conversions class (six months ago) and talk a lil bit about emissions and such. Combustion temperature and fuel mixture are both variables when you talk about emissions. The two baddies in the combustion process are CO2 and NO. I am not sure which one of those products are thought to be worse by the emissions regulations people but.... as combustion temperature increases your NO emissions get greater and your CO2 emissions go down. There is a curve for this and it is not linear but the point is temperature does have an effect on emissions so it is possible that the fan was put there for emissions purposes in addition to the oil cooking issue. Rock on. | ||
| Darthane |
...hence the long, dirty, 'warm-up' that liquid cooled engines suffer from. Air cooled engines reach operating temperatures much faster. Incidentally, that is what I was referring to in the Fan Discussion thread when I mentioned that cooler wasn't always better. | ||
| Lenb |
...hence the long, dirty, 'warm-up' that liquid cooled engines suffer from. Air cooled engines reach operating temperatures much faster. Not necessarily true. Liquid cooled engines have thermostats that restrict the flow of coolant until the engine has reached operating temperature. Liquid cooled bikes I have owned (and own) warm up pretty quickly. Air cooled engines probably take longer to warm up as the cooling fins radiate heat while the engine is trying to warm up. |
