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Post by humanshield on Mar 31, 2015 22:03:23 GMT -5
Anyone else ever run into anything this crazy?
I know this is gonna sound nuts, but every time I ride and there's strong headwinds I get some hesitation in the scooter.
It's not really the wind itself slowing the scooter, it's a momentary loss of engine power. And it seems to coincide perfectly with gusts. I'm sure it's the engine dropping power slightly. Full throttle seems to overcome the slight surges. That's why I don't think it's the actual wind causing the surges. It happens mostly while cruising at 75-80% throttle.
I have the intake snorkel removed so there is a round opening facing the wind going into the intake box.
On one hand I think....nahhh...that couldn't be happening.....but it certainly seems to be.
At this point I have no evidence, just WAG's But I swear it seems that in headwinds, more air is forced into the intake and it causes mixture issues.....possibly a slight leaning of the mixture? Or maybe just out of aerodynamics, a low pressure area develops right in front of the intake hole so it gets less air into the carb? That would tend to richen the mixture just a bit.
Maybe it's just that headwinds put more demand on the motor which causes the slight hesitation...but that is NOT how it feels.
Not sure yet but something's going on. On really calm days it doesn't do it at all. Or at night when the winds all die down. No surging whatsoever. Only when there's some good headwind and it's strong enough to buffet the scooter around a bit.
You might assume I'm running a bit lean but if I increase the main jet size at all it bogs down badly. If I raise the needle, same thing. So if anything it seems to be borderline rich. Plug color is really good.
Anyone else ever experience anything like this?
Im gonna do some experimenting with this to try to find out what it is. Very odd.
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Post by 90GTVert on Mar 31, 2015 23:56:09 GMT -5
It's windy today so even the little 4 mile ride is "fun". The air/fuel ratio hangs around 12:1, then a wind gust hits and it drops to 16:1 and bogs for a few seconds. So on a day like today I get hit in the side by wind and pushed that way and the bog drops forward acceleration so it feels a little like being surprised by a push to the side and a stop at the same time. At least it's better than strong headwinds. Then the combinations of gusts and steady winds with the bog from the gusts can make it bog off and on for quite a while while and stay on the lean side. It's done this for quite a while. I assume it has something to do with pressure/turbulence in the airbox since I opened it up long ago and it does not act this way under other heavy loads like pulling up a hill. It's only wind. I've also heard of this complaint from people using pod filters. Yet another reason that leaving the air box alone can be a good thing. I'm just keeping mine as-is for the sake of consistency during the project. It isn't an issue for my test runs and such because I don't do any performance or fuel economy stuff when it's windy.
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Post by humanshield on Apr 1, 2015 7:24:27 GMT -5
Brent, Beautiful.....thought I was crazy. You always come through Time for another donation. I still have the stock air box but I'm using UniFilter green foam in place of the OEM paper. I also have the elbow snorkel removed but I'm gonna put it back on and see if it helps. I'm wondering now if the chinese engineers were aware of this issue and that is the reason for the snorkel elbow?
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Post by 90GTVert on Apr 1, 2015 9:24:15 GMT -5
Could be. Possibly to keep it open without any restriction a hose could be attached and routed under a fairing somewhere not sucking up engine heat, but out of the open.
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Post by humanshield on Apr 3, 2015 13:07:03 GMT -5
I was able to confirm without a doubt that the snorkel DOES prevent that surging in windy conditions. Put it back on, rode 25 miles on a gusty day....not one surge. Took it off...surging returned.
So that snorkel is designed to prevent the surging caused by changes in air pressure at the airbox intake and also probably to help prevent water entry into the intake.
Problem is...the power is down significantly. I lost about 4 mph top end and acceleration took a big and noticeable hit as well.
So, I have to find an alternate intake set up.....or convert the scooter to F.I.
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Post by 90GTVert on Apr 3, 2015 13:10:55 GMT -5
Have you re-jetted yet? You'll lose power switching back and forth because the snorkel cover will change the jetting requirements.
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Post by humanshield on Apr 3, 2015 14:10:55 GMT -5
Well, the way I see it I have a BBK so I want to maximize air flow. As far as I can tell the snorkel is definitely going to cause some restriction either through turbulence or increasing the flow path length.
What is your experience with sock filters or POD air filters?
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Post by scooterpimp on Apr 3, 2015 17:37:50 GMT -5
Sure it isn't all those donuts slowing you down?
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Post by Fox on Apr 3, 2015 20:48:24 GMT -5
I've never done any wind tunnel tests but I am fairly certain that when you are riding along at speed that there is an area of vacuum that partially envelops the scooter (most likely in the area just behind the leg shield by your legs and feet) caused by the front fairing parting the air and the faster you go that area undoubtedly increases so if I'm right then it's logical to assume that a strong gust from the front could cause the vacuum envelope to bulge which in turn could cause a momentary loss of air to the carb so you get a rich bog. That's my theory anyway.
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Post by humanshield on Apr 3, 2015 20:53:41 GMT -5
Sure it isn't all those donuts slowing you down? Ouch ! To be honest...I went and picked up my donuts for tomorrow mornings coffee today....so....it's possible. I may not be able to hide behind the donuts...but they can sure hide behind my lard ass.
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Post by humanshield on Apr 3, 2015 20:56:04 GMT -5
I've never done any wind tunnel tests but I am fairly certain that when you are riding along at speed that there is an area of vacuum that partially envelops the scooter (most likely in the area just behind the leg shield by your legs and feet) caused by the front fairing parting the air and the faster you go that area undoubtedly increases so if I'm right then it's logical to assume that a strong gust from the front could cause the vacuum envelope to bulge which in turn could a momentary loss of air to the carb so you get a rich bog. That's my theory anyway. Love it! You may be right. I guess I'm gonna have to install a O2 bung and sensor set up. With all the money I'm already saving in gas, I can afford it on just that ! Might be the only way to figure out for sure if it's going lean or rich. Well, there might be other ways but the O2 sensor setup sure will be nice for future tuning and performance work....not to mention optimizing gas mileage.
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Post by 90GTVert on Apr 3, 2015 22:16:46 GMT -5
I've never done any wind tunnel tests but I am fairly certain that when you are riding along at speed that there is an area of vacuum that partially envelops the scooter (most likely in the area just behind the leg shield by your legs and feet) caused by the front fairing parting the air and the faster you go that area undoubtedly increases so if I'm right then it's logical to assume that a strong gust from the front could cause the vacuum envelope to bulge which in turn could cause a momentary loss of air to the carb so you get a rich bog. That's my theory anyway. Sounds good, but I have a wideband and can watch my AFR shoot to 15-16:1 when gusts hit.
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Post by 90GTVert on Apr 3, 2015 22:22:16 GMT -5
Well, the way I see it I have a BBK so I want to maximize air flow. As far as I can tell the snorkel is definitely going to cause some restriction either through turbulence or increasing the flow path length. What is your experience with sock filters or POD air filters? I used to use UNI filters on my old 4T. Don't recall this happening, but it was in the center of the scoot more shielded. I was gonna try out a few air filter suggestions I've heard on Project TaoTao sooner or later, but that's of no use to you now. I have a filter to fit over the carb, traditional style, a UNI that fits over the inlet of the airbox because I have heard someone say the best way is to remove the air box filter and put a pod on the inlet instead. I have a UNI sheet so I can cut a UNI filter to replace the stock one. All I can do is hypothesize/guess. My guess is there won't be a whole helluva lot of difference in any of them. I still use a stock air box just without a snorkel on my 90-110cc 2Ts with larger carbs and they work great. Maybe it's different with the 139QMB combo though. I've been wrong plenty before, so that's why I actually try these ideas when I can and report results.
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Post by Upgrayedd on Apr 3, 2015 22:54:00 GMT -5
Well, the way I see it I have a BBK so I want to maximize air flow. As far as I can tell the snorkel is definitely going to cause some restriction either through turbulence or increasing the flow path length. What is your experience with sock filters or POD air filters? I used to use UNI filters on my old 4T. Don't recall this happening, but it was in the center of the scoot more shielded. I was gonna try out a few air filter suggestions I've heard on Project TaoTao sooner or later, but that's of no use to you now. I have a filter to fit over the carb, traditional style, a UNI that fits over the inlet of the airbox because I have heard someone say the best way is to remove the air box filter and put a pod on the inlet instead. I have a UNI sheet so I can cut a UNI filter to replace the stock one. All I can do is hypothesize/guess. My guess is there won't be a whole helluva lot of difference in any of them. I still use a stock air box just without a snorkel on my 90-110cc 2Ts with larger carbs and they work great. Maybe it's different with the 139QMB combo though. I've been wrong plenty before, so that's why I actually try these ideas when I can and report results. i like that idea! a pod on the airbox inlet
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Post by humanshield on Apr 4, 2015 10:44:30 GMT -5
I used to use UNI filters on my old 4T. Don't recall this happening, but it was in the center of the scoot more shielded. I was gonna try out a few air filter suggestions I've heard on Project TaoTao sooner or later, but that's of no use to you now. I have a filter to fit over the carb, traditional style, a UNI that fits over the inlet of the airbox because I have heard someone say the best way is to remove the air box filter and put a pod on the inlet instead. I have a UNI sheet so I can cut a UNI filter to replace the stock one. All I can do is hypothesize/guess. My guess is there won't be a whole helluva lot of difference in any of them. I still use a stock air box just without a snorkel on my 90-110cc 2Ts with larger carbs and they work great. Maybe it's different with the 139QMB combo though. I've been wrong plenty before, so that's why I actually try these ideas when I can and report results. i like that idea! a pod on the airbox inlet Well, it might work but the longer the path and the more turbulence along that path you're actually creating a resistance to the intake. Many new cars use variable intake length manifolds to adjust the torque map this way for better performance. The Ford Taurus SHO for example.
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