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Oil Cooler Location

N

npowell

Well Known Member
I am building an RV-9A. I am working on the cowl, and looking ahead to the baffling. It looks like the oil cooler can be mounted on the rear of the baffling, or on the firewall.

What are the pros and cons of this decision?

Thanks in advance for your thoughts and comments.

Neal Powell
RV-9A
 
My oil cooler WAS mounted on the firewall when I made first flight in September 1997. I had constant high oil temp problems including 3 aborted takeoffs because of engine missing from what I believe was vapor lock. Moved the oil cooler to the engine mount behind the #4 cylinder and oil temp dropped 30 F. I had about 75 hours of flight with oil cooler on the firewall and over 2,100 hours with it behind cylinder #4.

IF you live or fly in a HOT environment, I do not recommend mounting the oil cooler on the firewall.

This is my experience. Others will tell you that their firewall mounted cooler works great.
 
FYI - The new and improved baffle kit comes with the hole pre-punched for placing the oil cooler behind the #4 cylinder.

Do a search, this subject comes up from time-to-time and there is a lot of info out there on it.

FWIW, mine is behind the #4 cylinder and here in the south I had no problems with high oil temps, even after a long climb.
 
Baffle

I asked Ken Krueger this very question at Vans tent in Oshkosh because I had so many stories of cracked baffles. He said without question he would mount on the baffle, the newer baffle kits have addressed the cracking issues and Gary Sobek was also there to confirm his experience of vapor lock and poor cooling. I was all set to mount on the firewall with materials to do so but now am leaning to the baffle mount.
 
What Does Van's Say?

npowell said:
What are the pros and cons of this decision?
Click to expand...
I doubt that any opinion offered on any topic, however bland, neutral or innocuous that opinion might happen to be, will not go unchallenged by someone, somewhere convinced he is armed with a more clear eyed, righteous grip on the facts. Throw in a little technical complication and.....well....just review the topic du jour, fuel systems, key word, "both."

Let's cut to the chase. You trusted Van's with your confidence and your money when you committed to build an RV. The reputation of Van's is based upon a steadfast focus on reality and giving the builder the most bang for the buck. By sticking with Van's suggestions as clearly called out in the baffle kit instructions, it will become plainly obvious what Van's opinion regarding this specific query is. The pros and cons you seek is just inviting an eager peanut gallery to talk among ourselves.
 
As others have so wisely stated, follow Vans recommendations on this. Yesterday's flight in the early evening saw ambient temps in the 90's and oil temp in the low 190s. No signs of baffle cracking either.

RV9 - 160 horses, FP prop, just over 380 hrs. :)
 
I Vote for the #4 Baffle

I put the cooler on the #4 baffle in my 2001 8A. The baffling around the cooler cracked repeatedly, and I finally ordered replacement parts from the new kit and replaced the baffling in that quadrant. I put the cooler behind the #4 cylinder in my new 7, too. The new kit is much better than the old one. The baffling in that area is made out of stainless. There is a doubler there and a brace across the top that was not in the old kit. Also, the cooler is mounted so that the outboard flange is attached to the angle at the corner there rather than just screwed into the baffling.

My oil temps have always been good in the Memphis summer. In the winter when the temps are below 50 degrees I block off the front of the oil cooler with a piece of .063 aluminum. Otherwise my oil temps wont get above 140 degrees.
 
I purchased my baffle kit from Vans about 1.5 years ago. How can I tell If these are the new baffle system or the old?
 
Tbone said:
I purchased my baffle kit from Vans about 1.5 years ago. How can I tell If these are the new baffle system or the old?
Click to expand...
The newer baffle kit is improved including much clearer to understand drawings and instructions. In addition, the 3 key pieces of aluminum baffling that the oil cooler is mounted to has a distinctly different coloration than the rest of the aluminum parts and is heat treated in such a way that the material seems to machine almost like steel. It will turn cherry red when you sand it. The oil cooler area also includes a reinforcement the older baffle kits did not have. The most obvious giveaway that defines the newer baffling is an access hole (normally plugged) located directly above each spark plug to facilitate periodic maintenance:

2eknnza.jpg
 
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Tbone said:
I purchased my baffle kit from Vans about 1.5 years ago. How can I tell If these are the new baffle system or the old?
Click to expand...

The simple way to tell is the drawings that came with the old baffle kit were drawn by hand and looked like copies of copies of copies. The new kit includes very clean CAD drawings.
 
Neal,
I'm one of those guys that didn't deviate from Van's plans. I figured they designed a good solid airplane and hey, I'm not an aeronautical engineer. I used the firewall fwd kit and stock oil cooler (7 tubes) mounted aft of the #4 cyclinder. I live in Tucson Az where it's hot. My oil temps had been running 220 - 230 degrees until I installed the wheel pants and gear leg fairngs. Now my oil runs 208 in cruise. The increased airspeed from the fairings increases airflow thru the cooler. I fly early in the morning (0530) this time of year when ambient air temps are 85 degrees at a field elevation of 2000 ft. If I had to do it over I would buy a larger oil cooler (9 tubes) and install in the same location. When you install the oil cooler mount it as high as possible just keep it from chaffing on the top cowling. I could have gotten mine about 1/2" higher. The higher the better because the lower portion of the cooler is blocked by the cyclinder head. I talked with Scott at Van's several weeks ago and suggested they supply larger oil coolers in their firewall fwd kits and or suggest a larger cooler for folks living/operating in high heat environments. I hope this helps you make up your mind.
Charlie, Tucson AZ
 
49clipper

Its a matter of choice. Mine is on the firewall and have never had hot oil. 95 degree takeoffs at 85 mph and prolonged climbs and never over 195 on the oil. I have done lots of mods on all the rest of the baffling though. The baffling on any airplane is lots of trial and error. I fabricated a circular funnel shaped oriface (1 5/8" hole) to go into the three inch sceet hose going to the cooler and it warmed my oil up a bit (which I needed) and helped cool down #4 cylinder. Mine ran way too cool till I got that adjusted. Just lots and lots of T & E.
Jim
RV-6 160hp Sen fp
 
In today's building, it's best to follow Van's recommendation. Mine has been on the firewall for over 16 years without problem. But back then he didn't have a recommendation. The "plans" didn't go forward of the firewall except for the cowling.
 
OK, so what is the hole for?

In Rick's photo, he mentioned that hole is for maintenance. I have that hole, and its not obvious to me what the heck its for. I have it taped over for now as fundamentally I dont like leaks in baffling, but wondering what the purpose is at least before I permanently plug it!!

Oh, and I have my cooler behind the #4 baffling, but used a slightly oversized cooler and my oil temps are too cool (low 170s) at cruise, even in summer..... :-(

Tim
RV8, phase one!
 
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Redwagon said:
In Rick's photo, he mentioned that hole is for maintenance. I have that hole, and its not obvious to me what the heck its for. I have it taped over for now as fundamentally I dont like leaks in baffling, but wondering what the purpose is at least before I permanently plug it!!
Click to expand...

I don't have that hole, but I wish I did ;-). I presume it is to slide a socket extension down to the top plugs.
 
reinforcement

I ahve one of the newer baffle kits and moutned mine according to plans. The one thing I did differently, following the advice of a local builder who posted on here (thanks Andrew) was to put a piece of alum angle reinforcement along the corner where the two baffle pieces are joined with the oil cooler. I'm hoping this prevents any cracking from occurring.
 
Thanks

Thanks for the comments. I really appreciate learning from your experience. I have the new baffle kit and will be mounting my cooler on the baffle behind the #4 cylinder.

Thanks again,

Neal
 
I will be starting the cowling soon, then onto the baffling. Do the new Vans baffle kits allow you to mount the larger 8432 SW coolers without significant mods?
 
Mine is Firewall mounted without any problems or high temps in over 600 hours, and no cracked baffles. I also have high compression, injection, C/S, electronic ignition, blah blah... Point is, part of the issue with oil coolers and engine cooling is to allow enough 'mass flow' out of the cowling exit area. My bottom cowl is for the O-360 engine (needed for an IO-320) which has about an extra inch in heigth of exit area so that may be the major difference here. YMMV... :cool:
 
#14 08-09-2009, 11:00 PM
Redwagon Join Date: Jan 2008
Location: Cupertino, CA
Posts: 32

OK, so what is the hole for?

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In Rick's photo, he mentioned that hole is for maintenance. I have that hole, and its not obvious to me what the heck its for. I have it taped over for now as fundamentally I dont like leaks in baffling, but wondering what the purpose is at least before I permanently plug it!!

Oh, and I have my cooler behind the #4 baffling, but used a slightly oversized cooler and my oil temps are too cool (low 170s) at cruise, even in summer..... :-(

Tim
RV8, phase one!

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Last edited by Redwagon : 08-09-2009 at 11:04 PM.


Tim
The new baffle kit comes with plugs that screw into this hole that you can remover with a screw when it comes time to access it for plug removal. No need to plug it permantately.
 
Change of Plans

Thanks again for the great responses. Although I said above that I would be mounting mine on the #4 baffle, I have now changed my mind. I have an O-320 with a conical mount, and I had to butcher both rear baffles extensively to install them. Since the left rear baffle has few adequate attachment points, and will never be as sturdy as it would be on a dynafocal mount, Van's is now advising me to mount my cooler on the firewall.

I will use an adjustable closure inside the 3" scat to adjust the airflow to the cooler. A friend did this on his RV-6 and he actually has to partially close his valve in order to have his oil warm enough.

Thanks again for the great discussion. By the way, LOTS of things from the FF kit don't fit properly on my older, narrow deck O-320.

Neal
 
oil cooler loc'n

as others, mine is on the baffle behind #4, and works very well. no cracking with proper bracing. save the firewall real estate for other things.
would definitely advise the adjustable louvers to save yourself the hassle of guessing when to cover the intake or exit air as seasons change, or even if morning to afternoon temps in spring & fall vary widely in your area!
 
oil cooler

Contrary to most, I have the firewall mount on the 160hp, sen FP prop, RV-6and have a partial baffle over the 3" SCAT to the cooler. I never see over 195F on the oil. At 95 degrees and it is normally at 185F. Normal cruise is at 5500 ' to 8000'. Don't know why, but it just works. At he baffling, it should be better, but you can't prove it by me.
 
New Baffle Kit Access Holes

DarylT said:
snipped
OK, so what is the hole for?

--------------------------------------------------------------------------------
In Rick's photo, he mentioned that hole is for maintenance. I have that hole, and its not obvious to me what the heck its for. I have it taped over for now as fundamentally I don't like leaks in baffling, but wondering what the purpose is at least before I permanently plug it!!
snipped
Tim
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Tim
The new baffle kit comes with plugs that screw into this hole that you can remove with a screw when it comes time to access it for plug removal. No need to plug it permanently.
Click to expand...

Darrell,
You mention that the plugs screw into the holes. What are these plugs made of? Could you post a photo or two of these plugs?
Thanks
Charlie Kuss
 
Baffle kit access holes

Those two holes are to slip an socket extension through so you can torque/remove the rear spark plugs. Van's provided Tinnerman washers in the baffle kit that use a screw/nut to "plug" the hole. Instead, I covered the hole from the inside with a strip of baffle mtl that can be pushed aside.
 
Notes

I just replaced the #4 baffle assembly due to corner cracks. Some notes:
An early post in this thread said the new kit comes with the oil cooler opening already cut out. That's not the case. I called Vans thinking I got a bad part. Gus Funnell told me, "We don't cut it out because a builder may still elect to mount the cooler on the firewall." Also a good thing because I cut my opening a bit further outboard and lower than the plans instruct.
All the pieces I received were made of aluminum not stainless as mentioned in another post.
 
Have it mounted on firewall on the RV6 with only 2" hose to it and it runs cool even with the positech cooler. You can get about a 10 degree drop using a Stewart Warner and you can double the airflow to it by going up to a 3" hose.
I had a 2nd oil cooler mounted on the baffles on my last plane (a Velocity). Used doublers for that section of baffling and made 2 braces to minimize vibration and add integrity. Worked well with no cracks.
 
rv9av8tr said:
I'm doing Van's baffles right now on my -9A. I tried to fit the oil cooler to the rear baffle.... and it interferes with the engine mount!! I've sent Van's an e-mail tonight for advice as to why this happened and how to resolve. Anyone else seen this happen?
http://www.mykitlog.com/users/display_log.php?user=n539rv&project=161&category=0&log=88709&row=1
Click to expand...

Mike, you should trim part of the aft flange enough to clear engine mount. If you look at the drawing, you can see that you only need two (or three) long spacers made from aluminium tube. That's because the remaining one just holds on the fore flange (and not both flanges) due to the aft flange corresponding portion trimming.
 
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