burgundyja

burgundyja

Well Known Member
I have a 200hp 8a no scoop under the prop. I have low cht temps in the winter. I was thinking about making a half box that would bolt on over the air filter and force about 80% of the air from that side into the filter. I think this should raise my cht and give me more mp. has this been done before? it would come off in the summer. if you think it would block to much on one side i thought about making one for the other side and putting in a small filter on that side.
 
cht

when it was 50 outside they where 270 to 290. when it got colder I tried blocking some of the exit air and i was able to get the hottest up 360 when it was 15 outside. that is with maybe half of the total exit air blocked. that is why i am thinking if i can block 40% before it hits the cooling fins that would be better. and it could give me more hp:D
 
Cowl Exit Plate

If my buddy Dan Miller is lurking here today, his set up is pretty cool. He has mounted a simple plate between the exhaust pipes held on with clamps around the exhaust tubes. That plate blocks a major portion of the Cowl Exit area. He can easily take this on and off for summer ops. He reported a 20 deg rise in CHT's and a slight rise in oil temp. as a result.
There are some really sophisticated cowling exit modifications that you might search for that do the same thing and reduce cooling drag. I thought Dans idea was clean and simple and gets the job done.
 
Reduce the cowl exit area

I agree with this approach. You should try reducing the exit area from the cowl to decrease the air flow. Done well, it will be more effecticve with less drag.

JonJay said:
If my buddy Dan Miller is lurking here today, his set up is pretty cool. He has mounted a simple plate between the exhaust pipes held on with clamps around the exhaust tubes. That plate blocks a major portion of the Cowl Exit area. He can easily take this on and off for summer ops. He reported a 20 deg rise in CHT's and a slight rise in oil temp. as a result.
There are some really sophisticated cowling exit modifications that you might search for that do the same thing and reduce cooling drag. I thought Dans idea was clean and simple and gets the job done.
Click to expand...
 
Are you sure your CHT's are reading correctly? As long as your oil temp is OK and you are developing full power, I don't see what the problem is with cool CHT's. If you need to warm your CHT's (?) then limiting exit air sounds like the best solution. Blocking one side of the inlet air doesn't seem like a good idea. The only good thing about it may be that you will only cook 2 of your cylinders. Of course you'd have uneven temperatures on critical parts of the engine, and you are probably blocking air that should be going through your oil cooler. My CHT's run about 320 in the winter, 350-360 in summer and that's fine with me, but I wouldn't be unhappy if they were cooler. Cool is good when it comes to CHT. You might want to try a cooler spark plug (reverse thinking here). A cooler plug carries more combustion chamber heat up through it's body into the head - keeps the firing end of the plug cooler, but transfers more heat energy into the head, hence possibly higher CHT's. This is for the benefit of the spark plug and may not result in much CHT increase and may also affect combustion efficiency. You can check with Lycoming or ECI and get an approved spark plug chart with different heat ranges. If you're running an electronic ignition, your choices are more. I don't think you have a problem though. I would measure the accuracy of my CHT probes before I went any further.

Scott
 
i have done the exit air thing

but i was thinking that all that air was just going to waste. so i should be able to use it. I think if it works i could even put a flap in the back that can be opened. also about the 2 hot and 2 cold i could put a smaller scoop on the other side and have 3 small tubes that go to the alt, fuel pump and oil fillter. maybe even some extra air on that side for the intake. the exit air block works but if i do that i think i want to make a cowl flap. has anyone done this? it would be easy to do in the middle of the pipes but harder on the sides.
 
Search for cowl mods

burgundyja said:
but i was thinking that all that air was just going to waste. so i should be able to use it. I think if it works i could even put a flap in the back that can be opened. also about the 2 hot and 2 cold i could put a smaller scoop on the other side and have 3 small tubes that go to the alt, fuel pump and oil fillter. maybe even some extra air on that side for the intake. the exit air block works but if i do that i think i want to make a cowl flap. has anyone done this? it would be easy to do in the middle of the pipes but harder on the sides.
Click to expand...

Do a quick search. I know Larry Vetterman has doen this as well as others. Look for the thread on cowl exit tuffting.
 
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