Pete in PA Posted February 12, 2006 Share Posted February 12, 2006 When I took my test ride to check the head bearings and suspension work I just completed, I did it naked. (the bike not me) Something I've never done before. For the FI guys the airbox inlets face almost perfectly forward, one on the left and one on the right, usually shrouded in plastic (the upper fairing) to stop any direct air blast. Fresh air is let in through the little slots, one on each side of the upper. Does it sound right that the fairing is also regulating the amount of air going into the airbox? Now I understand that it's not air tight in there but I think it almost acts as part of the airbox. When I took my ride the bike didn't quite run right, it had it's flat spot (again) at 3500rpm that I had got rid of with carb tuning. Since the left airbox intake is easily accesible, I covered it with my gloved hand while riding and the bike instantly ran like normal. I went home and duct taped the left one closed and the bike ran perfect from idle till redline, just like it always does. I also would then cover the other one with my hand with the throttle lock on and it would instantly kill the engine so I know I have an air tight airbox. So I've got some questions. If the bike can breath through 1/2 it's normal intake, how much performance are we losing? Kind of throws out the K&N air filter debate doesn't it? Could we ram air the bike and gain some power or at least open up the fairing holes and rejet? Now today I'm almost done with the rest of my maint. and putting all the tuperware on but now it's snowing so I can't test it again. Unless I suddenly developed a fuel or carb problem, I can't think of anything else. Keep in mind I've had my bike dynoed and can do first gear power wheelies with stock gearing so it's at full power. Quote Link to comment Share on other sites More sharing options...
scott s. Posted February 12, 2006 Share Posted February 12, 2006 i have a 01 been rebulding so road it naked a few times.i saw no differance in performance from 0-100.the ram air hits at high speed by pressurising the air box and you get a mild supercharging effect.i have read that ram air on a carbed bird delivers to much air. Quote Link to comment Share on other sites More sharing options...
bartonmd Posted February 12, 2006 Share Posted February 12, 2006 I think you're correct Pete... although I believe I got rid of that situation by not putting the air stoppers at the front of those tracts where the oil cooler lines go through... I guess that may be why I had to re-jet even though I have just punched baffles and a K&N filter... Mike Quote Link to comment Share on other sites More sharing options...
shovelstrokeed Posted February 12, 2006 Share Posted February 12, 2006 You are on the right track with the idea that the fairing acts as a part of the air box. Run naked and the flow into the box is greatly disturbed which is the probable cause of your rough running. The reason you were able to cover part of the air box and improve the running at such low RPM is that the motor doesn't really require all that air, especially if it is turbulent, at that low an RPM. The air box inlets are designed to work in conjunction with the fairing ducting. If you search around under NACA duct, you should be able to determine the air flow through one of them at a velocity of 176 fps, which represents 120 mph. Take into account, as well, the pressure increase at the location of the duct inlet due to aerodynamic force and you will, no doubt, find that rather than restricting flow, the system is enhancing it. That is the key. This is a system, with various components contributing their percentages to the whole. Remove or modify one of the components and you effect the entire system and won't necessarily see the results you might expect. An example might be that of a hypothetical friend of mine. Ed Racerboy decided his air duct, which had a strange taper to it, starting narrow at the front and increasing in diameter towards the rear, was too small. "I can do better than those dumb factory engineers", says Ed. Off to Home Depot for some 3" diameter dryer hose. Hacks the snorkels off the air box and fits the hose around the remaining stub. No room inside the fairing so he routes the hose over the top of the radiator and ties it to the lower triple clamp. Voila!! Loses 4 mph off his 1//4 mile trap speed and the bike is so flat that his ET drops 2/10th of so. He now gets to find out about plastic welding and finally winds up having to buy a new air box cover for his Z-11. Now this is a hypothetical guy, no resemblence other than name to anyone who might be posting here. Quote Link to comment Share on other sites More sharing options...
Guest rockmeupto125 Posted February 12, 2006 Share Posted February 12, 2006 Consider the possibility, Pete, that you were getting enough pressure to inhibit the flow of gas INTO the airstream of the carb...effectively leaning the mixture. By occluding the intake and bringing the intake pressure closer to barometric, the gas was again able to atomize from the jets in a more stoichiometric ratio, and the performance was regained. Quote Link to comment Share on other sites More sharing options...
Pete in PA Posted February 12, 2006 Author Share Posted February 12, 2006 I think you're correct Pete... although I believe I got rid of that situation by not putting the air stoppers at the front of those tracts where the oil cooler lines go through... I guess that may be why I had to re-jet even though I have just punched baffles and a K&N filter... Mike But the airstoppers are there to seperate the hot air coming off the oil cooler from cool ambient air for the airbox. There appears to be some performance to be gained here though I don't have the patience to get it. (and the heavy mods to the fairing) I've got some more thinking to do. we got 5 in. of snow so I won't be riding for awhile anyway. Quote Link to comment Share on other sites More sharing options...
bartonmd Posted February 13, 2006 Share Posted February 13, 2006 I think you're correct Pete... although I believe I got rid of that situation by not putting the air stoppers at the front of those tracts where the oil cooler lines go through... I guess that may be why I had to re-jet even though I have just punched baffles and a K&N filter... Mike But the airstoppers are there to seperate the hot air coming off the oil cooler from cool ambient air for the airbox. There appears to be some performance to be gained here though I don't have the patience to get it. (and the heavy mods to the fairing) I've got some more thinking to do. we got 5 in. of snow so I won't be riding for awhile anyway. Oh, I didn't take them off... I just don't recall them being there when I put the thing together... Mike Quote Link to comment Share on other sites More sharing options...
Flitemdic Posted February 14, 2006 Share Posted February 14, 2006 There was some talk here when I first became a member about Ram air and the carb'd 'birds. Can't find it for you now, of course, sorry. Anyway, the discussion ended up that the airflow into that area prior to the filter would be so overwhelming as to cause running issues at anything other than idle speed- pressure issues, air/fuel ratio issues requiring rejetting, etc. I don't remember the conclusion being turbulant airflow, but rather amount of airflow, and the necessity to reshape and/or restructure the box area prior to the filter- (below the filter)- and that that would take alot of mathematical modelling to appreciate any true difference. That, and the necessary restructuring of the intake area through the fairing made it unlikely that I, myself, was going to do it. I wonder about removing the fences at the oilcooler intake area, though. It seems that maybe that may cut a little of the turbulance created by running the air through the fence, and increase your volume just enough to make a positive difference. I would think, however, that difference would disintigrate at speeds at which the incoming flow would have overwhelmed the turbulance issue anyway. (As someone famous once said though, I could just be talking out of my ass here. ) Anyway, that's the thoughts that came up when I was reading through this. Quote Link to comment Share on other sites More sharing options...
tomek Posted February 15, 2006 Share Posted February 15, 2006 Lottsa people went insane,lost all the remaining hair,grey,,etc trying to tune( jet) homemade ram air systems.Don`t do it. Quote Link to comment Share on other sites More sharing options...
Pete in PA Posted February 15, 2006 Author Share Posted February 15, 2006 I'm not doing any alterations to my fairing/airbox but I do find it odd that Honda appears to not have the carbed XX's up to their full potential. When I rode it naked I didn't go much over 70 so any ram air effect was minimal. It appears it is a turbulence issue or just getting more air into the airbox. I'll say it again, makes what airfilter you run a moot point. Makes me think of the 80's bikes that had the airbox removed and ran 4 individual filters. At least they were given all the air the engine wanted. Quote Link to comment Share on other sites More sharing options...
Pete in PA Posted February 17, 2006 Author Share Posted February 17, 2006 Rode it yesterday before work and too work. I had all the plastic on except the 2 inner pieces that surround the insturments and the 2 white dividers. It ran great! So it's not starving for air, it's the turbulance that causes the problem. Quote Link to comment Share on other sites More sharing options...
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