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Anyone tried covering up the new Van's cowl louvers?

jcarne

Well Known Member
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I'm running in the low 300s on CHTs and it's only 29 degrees outside. Probably going to have to restrict some exit area.

I suppose it would be an easy experiment for me to just do but has anyone tried covering up the Van's cowl louvers? How much if any change was noted? I have been toying around the idea of putting electric cowl flaps in their place but don't know if its worth the expense/gain.

Thanks!
 
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Louvers

I'm running in the low 300s on CHTs and it's only 29 degrees outside. Probably going to have to restrict some exit area.

I suppose it would be an easy experiment for me to just do but has anyone tried covering up the Van's cowl louvers? How much if any change was noted? I have been toying around the idea of putting electric cowl flaps in their place but don't know if its worth the expense/gain.

Thanks!

Jereme
What did you end up doing?
I'm considering the Antisplat electric louvers but don't want to add the weight.
Also dont want a mechanical control.
If they aren't needed, maybe best not installed.
 
Larry, I would opine that the standard cooling exit provides adequate cooling unless you're going with a hot-rod setup. If you want to optimize things, there are plenty of things you can do (see Dan Horton's cooling threads), but if you're just looking for reasonable cooling performance, the stock setup should be fine.

Louvers are a draggy way to add exit area and cooling airflow.
 
Louvers

I believe that Vans made the louvers a standard part of the -A kit when the new style nose gear and engine mount was introduced, presumably to counter the additional obstruction in the exit area.

I would consider an adjustable blanking plate simply installed with screws over the louvers. It may be necessary to adjust it a couple of times per year, according to the seasons, or even only for initial setup.
 
I believe that Vans made the louvers a standard part of the -A kit when the new style nose gear and engine mount was introduced, presumably to counter the additional obstruction in the exit area.

Good info. I haven't seen an example of the updated nosegear kit.
 
Did not do any accurate testing but installed one louver on an already flying 9A and speed seems the same??
Fin 9A

The difference won't be big given the overall small size of Van's louvers (the difference might not be measurable without a lot of effort), but ejecting air at low velocity into the freestream is draggy. Beyond that, a bunch of little slots are less efficient than one larger opening. Drag reduction adds up - a little here and a little there, and eventually the difference will be apparent.

I look at louvers as an expedient way to add cooling to an existing cowl or cowl design where you don't want to re-tool.
 
Me thinks

I think the louvers on the new nose geared RV7A/9A might be less dragging than having the exit air flow thru the center area of the old style nose gear with all the stuff hanging there, not to mention the poor corner radius at the transition from the firewall to the bottom skin.
 
I replaced the louver in one side of my -10 with a cowl flap from anti-splat. I was surprised that it does not seem to make any difference in cooling and only costs about 2 knots in cruise speed when open.
 

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Larry, thanks for bringing this back up as I had forgot about it. Here is my take.

I covered the louvers with speed tape and it made about a 5-10 degree increase in temps. While I haven't done an accurate speed test it does seem that my cruise speeds for my typical setting have also gone up about 2 maybe even 3 knots.

My long term thinking is to still put cowl flaps in their place. The louvers absolutely are not needed during the winter or any weather relatively cool. However, hot summer day climbs I can see why Van's put them on. I also don't find they are needed on hot summer cruising.

Also, there seems to be a lot of negativity surrounding cowl flaps. In short, yes the RV does not NEED them but to be honest I don't think the stock setup is optimized for climbs (if it was the speed would be lower at cruise). So a guy has 3 options:

1. accept higher than 400 CHTs on the climb on hot days, especially if you want to climb below 115 knots indicated.
2. go to lengths that Danh does on baffles (it obviously works really well)
3. install cowl flaps, open them during climb and close for the rest of the flight and take a small weight penalty

Timing also matters, if I didn't have a Pmag my CHTs would be insanely low. Pmags are well known to raise CHT 20-30 degrees from a stock setup.

In summary, I have good baffles, not Dan good but pretty dang good, like to climb below 115 KIAS initially, and want to close some area during winter at all times. Sounds like cowl flaps will fit my bill. Hope this helps.
 
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Sorry I should probably know this but what is the concern about low CHTs? Isn’t cooler generally better?
 
Sorry I should probably know this but what is the concern about low CHTs? Isn’t cooler generally better?

I had the same question a while ago so looked it up in the IO-360 Lycoming Operating Manual that states, "For maximum service life of the engine, maintain cylinder head temperature between 150°F and 400°F during continuous operation." so that's what I'm using as a safe operating range.

https://www.lycoming.com/sites/default/files/O-HO-IO-HIO-AIO & TIO-360 Oper Manual 60297-12.pdf
 
I had the same question a while ago so looked it up in the IO-360 Lycoming Operating Manual that states, "For maximum service life of the engine, maintain cylinder head temperature between 150°F and 400°F during continuous operation." so that's what I'm using as a safe operating range.

https://www.lycoming.com/sites/default/files/O-HO-IO-HIO-AIO & TIO-360 Oper Manual 60297-12.pdf

when running cold CHT's below 300F I noticed I had some EGT readings that were slow to rise. I could not explain this. after I began using cowl inlet air dams to get the CHT's to be always above 320F or so, the issue went away. now I get a normal response from my EGT's. I don't know why cold CHT's would cause this or if it even was related. it is just my observation.
 
Steve Your slow EGT response with low CHT's might be indicating reduced efficiency in the fuel burn.... just my theory. Seems like combustion would be optimized at a certain temperature range, maybe you found the bottom end.

Any powerplant engineers out there who could comment?
 
Steve Your slow EGT response with low CHT's might be indicating reduced efficiency in the fuel burn.... just my theory. Seems like combustion would be optimized at a certain temperature range, maybe you found the bottom end.

Any powerplant engineers out there who could comment?

slow EGT's were only on one or sometimes two cylinders, but they were consistently slow to come up. I almost pulled a valve rocker to check the valve guide. after getting the CHT's up during the Winter months with cowl air blockage, this issue went away. all EGT's coming up normally. who knows? nothing conclusive.
 
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