Anyone use louvers to aid in cooling? - Page 2

elippse · #11 06-23-2010, 10:23 AM

Quote:

Originally Posted by f1rocket

Before you go to the trouble of mounting louvers, you may want to verify that the lack of exit air is the reason for your high temps. Most installations suffer from a disruption of the airflow into the pressure side (upper) of the cooling plenum. For me and many others, smoothing out that flow has resulted in a significant reduction, almost to the point of too cool. I tweaked the openings on my Rocket and smoothed the top transition and lowered my cylinder temps 40 dF!

Now if you like the look of the louvers, then I doubt it will hurt you and if you are constrained on the output side, the louvers will help. Anecdotal exidence suggests that there are a lot of A models flying that do not have louvers and do not have a problem with high temperatures so I suspect that you can probably fix your problem without them.

I'm not knocking anyone who has used them. Some of the installs are pretty cool, and I'm specifically thinking of Larry Vetterman's solution. If you were going to do it, I'd check out his solution.

I totally agree, Randy! The first thing is to make sure all of the cooling system elements, such as the baffling, are doing their job. Having good cooling design on the top of the engine and then just expecting the air to find its way out on the bottom is to do only half of the job. Just dumping the output of the oil cooler into the region in front of the firewall is not good design. Outlets should be designed to handle the flow just as well as the inlets. Placing a contracting duct from the outlet of the cooler into a rear-facing opening of about 3-4 sq. in. will solve your oil temp problems. Oh; and louvers are not as good as a single rear-facing opening! Will they work? Probably. But are they as efficient? Definitely not! Anything that's not efficient makes drag!

Capflyer · #12 06-23-2010, 10:58 AM

I installed two louvers, one on each side bottom of the cowling on my RV7. They only helped a little in lowering my CHT's, about an avg of 5 degrees. I tried a lot of different things trying to get my temps down and what worked the best ended up being the easiest, cheapest, and quickest solution.

Look at the lower baffles where they wrap around the cylinders. There is probably a gap between the baffle and cylinders so all that sweet cooling air is not flowing through the cooling fins of the cylinder and escaping out the sides. I was helping a friend do some work on his Tiger and saw that on his these lower baffles were sealed with RTV to the cylinder. At that point I had tried many things along with lots of time and money so why not. Not even half a tube of RTV later my CHT's dropped an avg of 40 degrees.

Give this a try before all the work of installing the louvers.

apkp777 · #13 06-23-2010, 11:02 AM

I do have all my baffles sealed up well. I will work to smooth the inlets a bit. Louvers seem like they will help.

burgundyja · #14 06-23-2010, 11:54 AM

I was just thinking about this. I was thinking about putting it on the top of the cowl. If I remember the top is low pressure the bottom is high. I have the oil cooler behind #4. If I mount the louvers just aft of the oil cooler I think it would drop oil temp. It could raise CHT but mine are low.

sprucemoose · #15 06-23-2010, 01:00 PM

Tony,

Before you make any big changes, consider that you are still breaking in a new engine, and they tend to run a little warm while the rings seat. Give it another 10 hours or so and see what happens. Also check your baffles like others have suggested.

Did you calibrate the oil temp sender?

A O-320 powered -9 with a fixed pitch prop just doesn't seem like an installation that would require louvers.

gmpaul · #16 06-23-2010, 02:47 PM

Has anyone had any experience with using louvers on a Sam James cowl?
My oil temp is fine but my CHTs run high.
My intakes are attached with about 4 inches of accordian type hose to the plenum.
Would this make any difference?

Thanks,

GP

db1yg · #17 06-23-2010, 05:07 PM

Hi GP,

The picture of the red RV9a in this thread is on a Sam James cowl. However, it is on the older long cowl which did not have the honeycomb core.

You indicated you were using "accordian type hose"--are you referring to orange SCEET or SCAT hose?? If yes, I would recommend you go with the rubber system James recommends which is very smooth on the inside. Also, as others have said, before you add louvers, be sure you have a good seal on your James plenum to engine attach, a good seal and the appropriate size openings for the lower baffles, a smooth track for inlet air, and as clean as possible an outlet area.

Cheers,

db

kentb · #18 06-23-2010, 05:37 PM

I think that the seal at the top of the engine behind the flywheel is often over looked. A lot of cooling air can escape from the high pressure top of the cowl out behind the spinner if this is not sealed correctly.

Kent

elippse · #19 06-23-2010, 08:20 PM

Quote:

Originally Posted by kentb

I think that the seal at the top of the engine behind the flywheel is often over looked. A lot of cooling air can escape from the high pressure top of the cowl out behind the spinner if this is not sealed correctly.

Kent

Right on, Kent! I have a friend with an RV-8 that was running much higher temps and he found that the seal you mention had gotten turned forward and was allowing the air out.

apkp777 · #20 06-23-2010, 08:20 PM

Quote:

Originally Posted by sprucemoose

Tony,

Before you make any big changes, consider that you are still breaking in a new engine, and they tend to run a little warm while the rings seat. Give it another 10 hours or so and see what happens. Also check your baffles like others have suggested.

Did you calibrate the oil temp sender?

A O-320 powered -9 with a fixed pitch prop just doesn't seem like an installation that would require louvers.

Thanks Jeff,

I spent several hours today redoing my baffle seals. I thought they were pretty good, but found that in fact, there were several leaks. Also, I can see the the inlets are difficult to seal up. I used foil tape and sealed it really well and found the my temps maxed at 198 (versus 215 before).

Still a bit warm, but definitely better, much better. At this point I feel comfortable where there at and I can begin to focus on progressing through my flight testing.

I ordered a set of louvers and am pretty sure I will install them. I am going to wait till I am out of Phase I, so that I have a good baseline set of data.

I still see my CHT's getting warm (430's). I think the louvers will do well to bring them down a bit.