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Louvers needed or not?

swisseagle

Well Known Member
Hello,

I'm in the proces of installing the cowling. Now the question pops up, if louvers are needed or not?

I live in switzerland, so in the winter it is cold, in summer it can go up to 85-100? fahrenheit.

It is a RV-7A with IO-320

For sure it will be easy to do it now, before painting. But I only will do it when it looks neccesary.

Thanks for any input!
 
Hi Dominik

I live in Sydney Australia and have an IO-360 in my RV7, I have difficulty getting the oil temperatures high enough in winter (it does not get cold here so to speak) and have blocked off 3/4 of my oil cooler, which is mounted on the rear of the plenum.

It is spring here at the moment, temps around 27C and I still have my oil cooler blocked off and temps are just getting into the 170F range.

So I would hold off on the louvers.

Cheers
 
I live in Minnesota USA, which has a similar temperature range. I found that if anything, I have too much cooling for my IO-360. I was very careful to fit the baffles tightly, and to seal gaps with high-temp RTV to prevent air from leaking around the baffles instead of going through either the cylinder cooling fins or the oil cooler.

I'd be surprised if you need louvers; I'd build it and test fly first. If you have cooling issues, louvers are easy to add afterwards.
 
I live in Maine with similar weather. RV8A with o-360-A1A and the oil cooler shutter works well to fine tune cooling in winter and summer. No louvers.
 
Hi Dominik,

I have a 6A with an O-320 and suffered from high CHTs until I added louvres. I believe the outlet hole is too small, so there is not sufficient airflow through the cowling. The louvres dropped my CHTs by at least 40F, so much so that for this winter I think I will block half off with speed tape. The oil temperature also came down slightly, but has never really been an issue.

My view is that, yes, louvres are required, especially for a nose dragger.

Pete
 
You need the oil cooler louvers (or something else to simulate it such as a removable plate or aluminum tape)

Oil cooler louver kit from Vans

You do not need the cowl louvers like shown in the picture below

08-07625b.jpg
 
If you need to add louvers, you have another issue. :)

I have to disagree, after 4 years of chasing all the other alternatives I came to the conclusion that there was just no enough airflow through my cowl. Louvers fixed the problem in one go. They are going into the 7 in the garage during build.

Pete
 
Having many, many cool running hours behind -320 series engines (carbureted and injected) in the Texas Gulf Coast region (very hot and humid), and I believe your odds of needing supplemental cooling are extremely low. But as others have said, fly it first then make any corrections. But I'll bet you a Swiss watch that you will have zero issues.

-360 series - that's a totally different story.
 
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I think the experience range will make it difficult to know until you're flying. The conclusions I have come to are that, in general, ECI nickel cyliders tend to run hot, at least on the IO-360 installations. I could easily have formed an incorrect conclusion though:eek:

Are you committed to painting the plane before first flight? If not, then it is easy to establish during flight testing but after engine break in, if there is a problem. If there is, you can add louvers during flight testing. That's what the testing is for. I had heat issues and enlarged the exit area a bit to also allow for a bit more room to keep the exhaust from hitting either the cowling or the engine mount. I was VERY glad to have decided to wait with paint until I knew everything was right.

With my ECI engine I continued to have high CHT (after solving the high oil temps and opening up the exit area a bit) and I fabricated and installed a fairing around the engine mount where it attaches to the firewall at the exhaust outlet. This fairing helped lower my CHTs between 10 and 15 degrees. I fly out of Livermore, California and summer temperatures routinely exceed 100 degree F/38degrees C.

If you are committed to painting first, and don't mind the look of louvers then I don't see any down side to installing them during the build. If you see temperatures that are lower than you want you can always block them off.
 
...I fabricated and installed a fairing around the engine mount where it attaches to the firewall at the exhaust outlet....

A friend with a -7 has okay oil temps but higher than desired CHT. Any chance of a photo of this?

Thanks,

Dan
 
If you do a careful thread search, you will notice that many 0-320s have a tendency to run warmer than, say 0-360s, on RVs. It is problematic enough that Aerosport and Mahlon have both encouraged going to the extreme of drilling out the carb jet. I am in this boat and have spent the past 6 months going through the various routes to get temps down and am close to getting to the point of doing the carb jet and/or adding exit air, either through louvers or dropping the exhaust exit a bit.

However, there is also ample evidence that many 0-320s seem to run cool enough. Thus, my suggestion would be to hold off on painting the cowl and don't install the louvers just yet. I have had the cowl on and off so many times in the first 100 hours that I am very thankful it is not painted. Sure, I could have protected the paint job, but it would have made taking off and reinstalling the cowl hassle enough that I might not have removed it as often as one should during the first 100 hours.

Anyway, just another opinion, FWIW. Good luck.
 
I am in this boat and have spent the past 6 months going through the various routes to get temps down and am close to getting to the point of doing A) the carb jet and/or adding exit air, either through B) louvers or C) dropping the exhaust exit a bit.
First we exercised option C. Then we implemented option A) with first a #41 bit and then #40.

We considered option B but decided that option C was easier and better.
 
If you do a careful thread search, you will notice that many 0-320s have a tendency to run warmer than, say 0-360s, on RVs. It is problematic enough that Aerosport and Mahlon have both encouraged going to the extreme of drilling out the carb jet. I am in this boat and have spent the past 6 months going through the various routes to get temps down and am close to getting to the point of doing the carb jet and/or adding exit air, either through louvers or dropping the exhaust exit a bit.

First good data is needed by closely monitoring all CHTs and writing down the results at several flight conditions (or by using a data logging EFIS). Second determine what 'cool enough' is - in my book its cruising at < 380F all cylinders and climbing at < 400F all cylinders, all weather conditions.

Carb jet drilling specifically fixes lean running - lean at 6 to 8,000' to determine if you are running too lean at full rich mixture (expecting at least a 150F EGT rise - if not your jet could be too small). One symptom is hot CHTs, but probably not worth drilling the jet just to get the temps down.

When the engine is running at the right mixture high temps are due to either air being wasted in the cowl, or insufficient flow through. Its easier to fix the former by ensuring a good seal at the front, including the top ramps, and working on the baffling. After all of that I had to install louvres to get the crusing CHTs reliably below 380F.

However, there is also ample evidence that many 0-320s seem to run cool enough.

It is dependent on airplane type, 4s cool better than 6s, don't know about the rest. Aslo see first point!!

Pete
 
All good points. And you left out checking the plugs and pistons and fuel flow for signs of lean operation.

Our plugs were always nearly white, no scale on the pistons and fuel flow was almost 2 gal/hr below what is specified.

Before we would cruise between 380F-405F and without powering back have no idea what the temps would reach but they would go sailing past 450F towards meltdown.

Don't know how much of a difference opening the cowl made because we could never leave the in all the way, but like others, the CHT drop by increasing the opening 5/8" was over 30F and probably at least 40F-50F:eek:

But we were still lean like nearly every other carbed D1A O-320 9A.

After chasing all of those other things for a year first then opening up the cowl and jet, now we cruise below 380F all cylinders and almost alway climbing below or near 400F.

Somewhere on here there is a link to an article from an EAA member that did an excellent job of documenting all of the steps he took chasing this problem which was cured by opening the outlet and drilling the carb just as it fixed ours.

If you are committed to painting first, and don't mind the look of louvers then I don't see any down side to installing them during the build. If you see temperatures that are lower than you want you can always block them off.
Except that louvers may not be as effective as opening the outlet and installing a fairing.

I have a 6A with an O-320 and suffered from high CHTs until I added louvres. I believe the outlet hole is too small, so there is not sufficient airflow through the cowling. The louvres dropped my CHTs by at least 40F ... My view is that, yes, louvres are required, especially for a nose dragger.
Pete
Yes in many cases the flow is too little, but I think that there a number of fixes that show that open the outlet is at least as effective. I think after much research most folks that install louvers don't place them in the proper location (e.g see Pipers and Bonanzas)

Does anyone have a carbed O-320 9 that runs too cool? haven't see one.

There are a number of NACA studies that are available on the net that address cooling in more detail than most folks would care to try and understand.

You can chase it as long as you want ... or just fix it...
We stopped chasing it after about a year of trying all of those other things... As soon as the engine warranty we carefully increased the jet...
 
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Yup...post #39 from Bob Cowan. I borrowed Bob's templates, traced them on some old file folders (stiff paper) and then did some modifications for my own installation.

Thanks for the reference thread post Dave.
 
Here is the link to a well written story of the trials of getting CHTs down..
http://www.mnwing.org/Sept2011.pdf

A friend sent us the link just as we were finishing the cowl mod and getting ready to drill the jet.
Thank again John for finding and forwarding it.

It was nice to know we weren't the only ines that discovered this was the path to lower Chts.
 
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PS When I sealed the inside face of the ramps in the upper cowl I gained a few knots ( 3 or 4 - wasn't being very scientific at the time) as well as better cooling!!

Pete
 
Here is the link to a well written story of the trials of getting CHTs down..
http://www.mnwing.org/Sept2011.pdf

A friend sent us the link just as we were finishing the cowl mod and getting ready to drill the jet.
Thank again John for finding and forwarding it.

It was nice to know we weren't the only ines that discovered this was the path to lower Chts.

The thread is quite old and the link is broken. Does anyone have that document still available and could share it with me?

Thanks!
 
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