Cowl Exit Airflow

[ghatch]

I have been looking in the archives for several days and cannot find the video I have seen showing tufts at and around the cowl exit hole. As I remember the video indicated that there was significant air entering the exit hole around the sides. I did find this video but it not the one I'm looking for. http://www.youtube.com/watch?v=CrvQeOGzJ7s

Might any of you folks know about this problem or know where to find the video. I'm having oil cooling problems and suspect insufficient airflow probably at the exit and not the entry.

Thanks you,
Gerry

[rvbuilder2002]

Gerry,
I know these types of problems can be frustrating, but may I suggest you eliminate simple things first.
As of this morning, Van's web site lists that 7189 RV's have been completed and flown. A very small percentage of these have shown to have any type of cooling issue after engine break-in was completed (and then usually only in rather severe temp conditions which you are not likely experiencing this time of the year, or because of modifications to the engine resulting in more than standard power output).
If you have a highly modified engine (or alternate engine) installation then you may have to look at other means of resolving it, but if not, I would suggest you investigate the numerous other simple to resolve causes before investigating major modifications.

[L.Adamson]

I remember a video in which the owner moved the oil cooler from behind the rear #4 baffle, to the front horizontal baffle in attempt to get better cooling. It didn't help. Turned out the lines were mixed, where they connect to the engine.........or something to that effect. The cooler was moved back to the rear baffle location, and all was well. My 6A, with it's #4 rear baffle location, has been fine from day one.

L.Adamson --- RV6A

[RV8RIVETER]

I think this is the thread you are looking for.

http://www.vansairforce.com/communit...owl+exit+video

The square exit has been shown to be far from ideal. There are better ways to do it. I think the easiest is the way Dan Horton has rounded his exit. Although it would seem doubtful that it alone will improve your cooling problem.

http://www.vansairforce.com/communit...d=1#post511667

[ghatch]

Thanks guys. The video you listed is not the one I'm looking for but it is similar. I've tried all the simple easy fixes with only marginal improvements. I'm convinced it is airflow that is the problem. My outlet to inlet ratio is 1.5. I'm using a James cowl and plenum and I have SW10599 9 row oil cooler mounted on the the rear baffle recessed 7/8" from the cylinder fins. I used all 45deg dash 8 ss hoses. I've added louvers to the bottom of the cowl. My engine is a Aero Sport Power IO-375 B1B (8 to 1 compression) developing 195hp. My cyl heat temps are good (340-370 and less LOP) and within a few degrees of each other.
I plan to increase the volume of the plenum in an attempt to show down the airflow and I would like to smooth out the exiting air and eliminate the reverse flow. I forgot to mention that I have an AWI 4 into 1 exhaust with turned down exit. If all else fails, I will add a second oil cooler in the cyl 3 area. I have not yet removed the Vernatherm. My temps are OK if OAT is below 60F.

Thanks for you help.

Gerry
RV-7

[RV8RIVETER]

Your cooling issue can be summed up as either not enough oil flow thru the cooler or not enough air mass flow. I don't see how you would need a second cooler if all parts of your system are working as they should.

Have you tested the vernatherm?

Have you tested your oil temp probe/reading?

Do you have an exhaust duct on the outlet of the cooler or do you just dump the air into the cowl?

If it is the latter that may be an issue, not enough Delta P.
Air flow being directly related to the pressure differential across
the cooler, you may want to try to duct the outlet to an area of low
pressure, like near a cowl exit.

[flyboy1963]

Gerry,
I am not a mechanic, but the AME who did build my (our) plane did this.
without instrumentation to know the exact temp of the oil going into and out of the cooler, it's hard to say the cooler is not dropping the temp x degrees.
...so it could be in a good location already.
The other question is; how MUCH oil is being directed thru the cooler by the vernatherm. If it is only opening 50%, then you are only cooling half the oil you could be.
Talk to a mechanic, and although not simple, adding or removing washers from the vernatherm I believe is the way to adjust a functional unit. If it is not functioning to spec, it may not be allowing oil to flow to the cooler, and could requie replacement rather than shimming. ( excuse the terminology if incorrect.)

[swisseagle]

Hello Gerry

Look on the webpage of Larry Vetterman (RV-Exhausts), he has there a documentation about the fairing he has done to improove the situation of the airflow.

http://www.vettermanexhaust.com/
bottom of the page.

Regards Dominik

[DanH]

Originally Posted by flyboy1963

.....other question is; how MUCH oil is being directed thru the cooler by the vernatherm. If it is only opening 50%, then you are only cooling half the oil you could be.

The vernatherm is retracted when the oil is cold, meaning the bypass port is open. Most oil flows through the open bypass port. A little flows through the cooler.

The vernatherm extends when the oil is hot, blocking the bypass port and forcing all oil flow through the cooler.

Cold = port open
Hot = port closed

Vernatherm problems come in two varieties.

(a) The vernatherm is not extending properly when warmed. Remove it and test it in a hot liquid bath.

(b) The extended vernathern is not seating in the port properly. Unscrew it and examine the conical end. Hopefully you'll be able to see a nice even seat mark all the way around the cone.

[ghatch]

Again, thanks for your input. I'm at condition inspection time now and will remove the vernatherm to inspect and test. I have seen Larry Vetterman's post and have talked to him several times. He's convinced it is the exit airflow based on his detective work. He is as Y'all know a great believer in removing the vernatherm and installing a cockpit controllable valve to regulate oil flow into the oil cooler.

Thanks,
Gerry