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Post by Kenho21 on Mar 31, 2019 13:05:02 GMT -5
Picked a pair up, but I'm not convinced on whether or not I want to actually use them. Supposed to drill holes in the airbox cover and install them. Opinions?  |
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Post by tiny on Mar 31, 2019 14:18:49 GMT -5
What are they and what do they do?
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Post by jackrides on Mar 31, 2019 14:25:26 GMT -5
If the airbox has a filter in in, drill holes and leave them open?
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Post by Kenho21 on Mar 31, 2019 19:15:36 GMT -5
If the airbox has a filter in in, drill holes and leave them open? I just hate it when someone comes along spewing common sense and stuff haha. I guess I figured they would add a bit of filtration, but your point makes me look at it as perhaps just more added drag when I’m trying to achieve less. Is there much performance benefit to drilling an airbox in the first place? |
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Post by oldgeek on Mar 31, 2019 19:28:15 GMT -5
Not really unless your engine needs the extra air. Screwing with the airflow even a small amount will require re jetting the carb. Most people just pull the rubber snorkel from the top of the airbox, that alone provides plenty of air unless you have something like a hyper race setup.
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Post by Kenho21 on Mar 31, 2019 19:36:37 GMT -5
That’s kind of the conclusion I was starting to come to. However, I am about to retune both of my scooters since I recently acquired them and I’m on the tail end of a mild overhaul. That’s why I was debating it in the first place.
Maybe I’ll just remove the snorkel or open it up a bit and call it good.
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Post by ThomasTPFL on Apr 1, 2019 1:13:28 GMT -5
I’ve got a handful of them. Never used them. I drill holes in my airbox on the dirty side of the filter so those things would be redundant. Then my airbox falls off and I use an old sock. Then I step in something gross and need the sock so I use a bit of curtain. Eventually I’m gonna cut enough off that girlfriend notices then I’ll be in trouble.
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Post by ThaiGyro on Apr 1, 2019 1:36:54 GMT -5
haha! I belong to a few Honda thumper and CRF forums. The most common misconception for a CRF250L is that many believe that the Honda engineers have starved the engine, so they mess with the air-box inlet or drill the sides and add those same goofy-ass filters..to let more air in. Supposedly. Problem is that is doesn't allow the well engineered (resonent) flow to happen properly. I achieved +0.8 dyno hp on mine by simply removing the backfire screen. I first looked at how the engine was designed to flow and perform. Built for low end torque. The prior owner added an Acropovic full exhaust system. Low end torque reduced, mid range reduced a bit, top end torque reduced...but top end hp is up 1.1 hp. Nice for near $700...People just listen to the wrong info
As stated above, if you want more tuning problems, worse fuel economy and a noisy intake, have fun!
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Post by Kenho21 on Apr 1, 2019 5:55:57 GMT -5
Well thanks for talking me down before I broke out the drill haha.
My girlfriend (who is a neural engineer and a smart cookie) actually expressed the same sentiment you guys have. I mentioned cutting into the air box to allow more airflow and without hesitation she hit me with some thermodynamics (which she studied for fun while working at a brewery in undergrad) logic and explained how much sense that does not make hahaha. Proportions of airflow and density blah blah blah. Without her and you guys, I’m a mild idiot and will do things accordingly...and thank everything she’s not into scooters or she’d make me look bad quickly.
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Post by ThaiGyro on Apr 3, 2019 7:16:40 GMT -5
To give you an idea...my '75 Yamaha TA125B came with 28mm Mikuni's. I used 32 mm Lectrons, that barely fit side-by-side, but that engine made ~30 hp. (Stock was ~24) Problem was that it could not do a 10 lap race. Six...OK, eight was marginal. Sucked up fuel! If we had air-box technology in 1975, I am sure it would have been waaay more efficient.
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Post by ThaiGyro on Apr 3, 2019 22:28:20 GMT -5
Not sure how much is out in web-land regarding 2 and 4 stroke air-box technology, but must be quite a bit. When I have questions, I have a few go-to peeps. One is a professor at Graz University in Austria. Dr. Mario Hirz. He has done much research on air boxes, plus fueling systems. Has given me some good tips over the past few years.
Others are aerodynamic gurus, who helped with my race car wing replacement and air-box location. (After I ate the wall in the rain in Seattle) The problem of adequate inlet air flow is an issue on all vehicles for very different reasons.
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Post by Kenho21 on Apr 3, 2019 23:17:35 GMT -5
Sounds like you’ve had your go arounds with the wind haha.
Appreciate all the insight.
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