Wind deflectors and engine temps?
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Stellar HDF Member
Joined: Apr 2012
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From: Maryland
Wind deflectors and engine temps?
I've got a pair of JES wind deflectors for the 2018 Heritage. I'm wondering what their impact may be on engine temps. Unfortunately I don't have a PV for the bike yet and can't monitor the ET for differences (with and without the deflectors). The deflectors are mounted on the outside of the grommet leaving a decent gap between the deflectors and the forks for air the pass through. The deflectors appear to be shaped to channel the air through that gap and towards the engine. I can feel a lot of air coming through that gap. At the moment I can't tell if the bike is running hotter or not. Once thing I can tell, my right hamstring is feeling some heat. Left side is fine. I've seen mixed opinions on this, but little in terms of testing or useful measurements. Anybody got any good info on this to share?
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Joined: Sep 2013
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From: Wisconsin
I read on-line somewhere that a guy measured a small temperature increase with fork wind deflectors installed.
A week ago, I rode through Needles, California. The ambient temperature reached 121 F in the desert near Needles, 117 in town.
No issues with engine temperature. The bike ran fine and there were no temperature alarms or single cylinder operation.
I have my JES deflectors mounted inside the windshield mounts which narrows that gap. They look better to me that way.
A week ago, I rode through Needles, California. The ambient temperature reached 121 F in the desert near Needles, 117 in town.
No issues with engine temperature. The bike ran fine and there were no temperature alarms or single cylinder operation.
I have my JES deflectors mounted inside the windshield mounts which narrows that gap. They look better to me that way.
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Stellar HDF Member
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From: Maryland
So I talked to the guy at JES (I don't recall what he said his name was - because I'm terrible with names). Basically, he stated that the wind deflectors don't cause issues with engine temps. He did say that there are trade-offs with using them. Without prompting, he described the main trade-off, which is that you will feel additional heat on your legs and crotch area. That is exactly what I'm experiencing. My right hamstring can get a little toasty. He said he put a fair amount of design and testing (too include wind tunnel) effort into the deflectors development and that he knows exactly how they effect the air flowing around the bike. He says the heat that I feel on my hamstring is expected based on how the deflectors were designed to work. The heat felt on the leg/crotch area can be misinterpreted as the motor running hotter, but he says it's not. It's just a byproduct of how the air is being controlled and how it impacts that particular area in terms of evacuating heat.
So there's that... Take it for what it's worth.
Me... I'd still like to seem some measurements. I'll probably be revisiting this question when I get a PV for the bike and can monitor ETs. I'll probably also get an oil temp gauge just for kicks.
So there's that... Take it for what it's worth.
Me... I'd still like to seem some measurements. I'll probably be revisiting this question when I get a PV for the bike and can monitor ETs. I'll probably also get an oil temp gauge just for kicks.
Last edited by T^2; Aug 13, 2019 at 12:35 PM.
Road Warrior
Joined: Jul 2012
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From: Ohio
I've got a pair of JES wind deflectors for the 2018 Heritage. I'm wondering what their impact may be on engine temps. Unfortunately I don't have a PV for the bike yet and can't monitor the ET for differences (with and without the deflectors). The deflectors are mounted on the outside of the grommet leaving a decent gap between the deflectors and the forks for air the pass through. The deflectors appear to be shaped to channel the air through that gap and towards the engine. I can feel a lot of air coming through that gap. At the moment I can't tell if the bike is running hotter or not. Once thing I can tell, my right hamstring is feeling some heat. Left side is fine. I've seen mixed opinions on this, but little in terms of testing or useful measurements. Anybody got any good info on this to share?
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Stellar HDF Member
Joined: Apr 2012
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From: Maryland
There is a significant difference in heat felt in that area with the deflectors installed vs. running without them. The difference is significant enough that it is unmistakable - definitely not conjured up by ones imagination.
Road Warrior
Joined: Jul 2012
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From: Ohio
Did you feel the heat without the deflectors?
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Stellar HDF Member
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Not really. At least nothing remarkable/memorable.
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From: Cleveland Zoo
It's a vicious circle. It's one of the things I'm so glad I left behind when I traded my touring bike and why I'm now enjoying a bike without a windshield.
Windshield caused buffeting for me, fork wind deflectors reduce buffeting but make more heat for the rider and probably the engine. Some said remove the wind reducing devices when it gets hot but that's when everybody rides so the buffeting is there with just a windshield. On some bikes the buffeting is so bad it blurs vision at highway speeds.
The right thigh heat on my Street Glide was terrible, so glad to now ride in the comfortable wind.
Windshield caused buffeting for me, fork wind deflectors reduce buffeting but make more heat for the rider and probably the engine. Some said remove the wind reducing devices when it gets hot but that's when everybody rides so the buffeting is there with just a windshield. On some bikes the buffeting is so bad it blurs vision at highway speeds.
The right thigh heat on my Street Glide was terrible, so glad to now ride in the comfortable wind.
Road Master
Joined: Aug 2007
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From:
I ran a thunderheads on my Night Train with no heat shields for 13 years, now everything feels cooler, or I just don't feel it anymore. To the point move air away from an air cooled engine heat will go up, just depends which you would rather deal with wind or heat.