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High Oil & CHT Temps - airflow problem?

lostpilot28

lostpilot28

Well Known Member
I spent the better part of last night reading the multitude of threads here on VAF regarding inlet/outlet size ratio in regards to improving cooling drag and lowering CHT and Oil temps. I also spent a lot of time recently researching getting a larger oil cooler. I'm beginning to think that a larger oil cooler may not help me.

My "problems" are slightly high CHTs (typically around 385 degrees cruising at around 170 mph TAS, in 83 (F) OAT). I also suffer from "high side of normal" Oil Temps around 215 (F) which creep up to the high 220's if I increase the power setting. If it's hotter outside things start getting even warmer under the cowl.

One thing I noticed that makes me think my cooling problem is related to my exit airflow being too small is that I can see a very small amount of oil exiting the side of the cowl by the upper/lower cowl seam. I guess this is the only silver lining I'll get for having a slight oil weep...but it appears to indicate that my exit air is not sufficiently large, and my bottom-half of the cowl pressure may be too high. Now I'm thinking about louvers instead of a bigger oil cooler. I'd really hate to cut into my nicely painted cowl for something that may not work, though! :rolleyes:

There's so much information on these related topics it's pretty tough to figure out which direction to start in. I considered removing the upper intersection fairing to increase the exit airflow, but I don't know if that's a good place to start troubleshooting. I'm appreciative of any suggestions on where to start.

My setup is an RV-7A, ECI 0-360, carbed, Catto 3-blade prop, Sam James cowl and Plenum, dual P-mags, piston skirt squirters, Niagra 20002A oil cooler. My temps aren't horrible, but I'd like to lower them a bit if possible.
 
Just to rule out another problem, what is your EMS system that is measuring these temps?

Certain EMS systems may register temps higher than actual if there is a poor ground between the EMS and the sensors.
 
Caution: marginal advise/comments may follow.

My understanding is that the piston squirters reduce CHT at the expense of higher oil temps.

You may be able to retard your P-mags and get lower temps (power trade-off?)

When I had high oil temp problems I verified the sensors; that the cowling seal was fine...then opened up the lower cowl around the exhaust and finally added louvers. Each of those two lowered the oil temp by maybe 10 degrees C I think. I would have to verify that from a post and pre/post flights may not have been under identical conditions.
 
breister said:
Just to rule out another problem, what is your EMS system that is measuring these temps?
Click to expand...

I'm using two MGL Voyager EFIS systems. Granted, they both read from the same engine monitoring module, but I did use a laser thermometer and checked my oil temps and CHT temps immediately after shutdown on a few different occasions. I aimed the laser where the probes are mounted and recorded the results. The laser did read around 10-degrees (F) cooler, but I attribute that to reading the outside of the housing while the actual probes were inside the engine. Either way, I'm looking for more than a 10-degree improvement, so even if they were reading a tad warm, I'd want to try and do better.

Ron Lee said:
My understanding is that the piston squirters reduce CHT at the expense of higher oil temps.

You may be able to retard your P-mags and get lower temps (power trade-off?)

When I had high oil temp problems I verified the sensors; that the cowling seal was fine...then opened up the lower cowl around the exhaust and finally added louvers. Each of those two lowered the oil temp by maybe 10 degrees C I think.
Click to expand...

My P-mags are running on the less agressive curve, so I can't (won't?) retard it anymore. You may be right about the piston skirt squirters. My ECI owner's manual states that if you use them that you should use a larger oil cooler than the one supplied in the Van's standard FWF kit.

How did you open up the lower cowl, exactly? I've read about others cutting it back (forward, technically) so that from the side it's angled a bit. Is this what you did? Mine is 90-degrees to the fuselage, currently.

Radomir said:
Are you cruising at 50ROP (aka the hottest point)?
Click to expand...

I am running between 75 and 100 ROP...if I go to 50 or less, my CHTs creep up to the low 400's.
 
IMHO, the Niagara 20002A oil cooler just simply has inadequate cooling capacity for an IO-360 engine, especially if you have oil squirters in it.

I watched the temps in our RV-8 on a recent X-C and with the new SW cooler, got 180-195 in cruise with 210 max in an extended climb.

I was running 100 deg ROP too.

A bigger oil cooler sure wouldn't hurt, but it probably wouldn't make a dramatic change in CHT either. Getting the pressure differential bigger from topside to underside and thus more air over the cylinders is about the only thing that could help that.
 
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75-100 is definitely helping some but it's not really enough. You really need to go way ROP (or just a little LOP) to drop the temps. That's why my preference is "little LOP" over "a lot of ROP" for exact same CHT.

Have you tried LOP? Since you're carburated, you may need to play with things a little, but it's been done.. I had no troubles (using LSE III), and I know Pete H. has done it too on his P-Mag equipped plane.
 
Radomir, I don't think I can get LOP with my carb setup ...I seem to get a little rough while my EGTs are still climbing. They max out at 1400 or so, but it's rough running already, so then I can only enrich the mixture.

Neal, thanks...and I think this is one path that I can take for a potential resolution. Is there any specific information on what I should be reading for a pressure differential?? I can easily make a manometer and measure upper and lower cowl, and even do so at various places...I just don't know what a good ratio should be. I'm also not sure if I should be checking different areas under the cowl, and not just comparing the top to the bottom.
 
I really haven't a clue what kind of pressure numbers to look for, but if you could rig up something to measure what you're actually getting in flight, that might provide useful data for someone who does know.

Some friends of mine who built an RV-10 two years ago put these kind of louvers on the lower sides of their bottom cowl and it seems to work very well for their plane, but they did it before painting:

http://www.rvtraining.com/html/atp//html/products_pics.html#louver11
 
How many hours on the engine and what is the spread of CHTs(ie what does "around 385 mean")

If you are still breaking the engine in these temps do not sound that bad.
 
Sonny,

What sender / EFIS are you using. I know with SkyView you have to select between 2 different sending units. (1/4 and 5/8 NPT). If you have the wrong one selected you will get a incorrect temp display.
 
N395V said:
How many hours on the engine and what is the spread of CHTs(ie what does "around 385 mean")

If you are still breaking the engine in these temps do not sound that bad.
Click to expand...

Hi Joe, 385 is around the average. The spread is probably within 10 degrees of each other. The SJ plenum keeps things pretty close together. The ECI cylinders seemed to be done breaking in around 7 or 8 hours...I have 86 on it now. I'm not so much worried about the CHT's as I am the Oil temps. 215 on an 83-degree (F) day seems a little high...not terrible, but high enough that I want it lower.

apkp777 said:
Sonny,

What sender / EFIS are you using. I know with SkyView you have to select between 2 different sending units. (1/4 and 5/8 NPT). If you have the wrong one selected you will get a incorrect temp display.
Click to expand...

You have to do the same with my MGL Voyagers...but I've made sure they're setup correctly.

I suppose my biggest fear at this point is replacing the oil cooler ($$) and still having a problem with airflow. On the other side of the coin, I don't want to start cutting holes in my cowl and not have that fix the problem, either! I may try cutting back the exit area 1-inch at a time like one of the other threads mentioned and see what happens. If it improves, great...if not, at least I won't have giant holes cut in the lower cowl. :rolleyes:
 
I respect your opinion

Neal@F14 said:
IMHO, the Niagara 20002A oil cooler just simply has inadequate cooling capacity for an IO-360 engine, especially if you have oil squirters in it.

I watched the temps in our RV-8 on a recent X-C and with the new SW cooler, got 180-195 in cruise with 210 max in an extended climb.

I was running 100 deg ROP too.

A bigger oil cooler sure wouldn't hurt, but it probably wouldn't make a dramatic change in CHT either. Getting the pressure differential bigger from topside to underside and thus more air over the cylinders is about the only thing that could help that.
Click to expand...

But it seems to depend on a lot of factors, and nobody has nailed them all down yet. Lots of discussion in other threads. I had to add a shutter to get my temps up on my IO-360 using the standard vans cooler. It stays blocked most of the year. I do agree though, it does not hurt to put in a better cooler, other than your wallet I guess.
 
OK, I pulled the trigger and bought the Aero Classics 10-row oil cooler. I'll report back with my results in a couple weeks.

Neal, I got your message. Thanks for that! It helped me decide on what to do. I only hope I have enough room to fit the 10-row behind the #4 baffle!
 
Picked this thread for the following because of the premise in the original post....increasing exit area to cure a cooling problem, which seems to be everyone's first thought.

RV-8 stock exit area is about 0.41 sq ft.



I built my cowl to accomodate swappable exit area panels and made two for the first flights. Here's an example:



At 6 hours I'm now running the smaller of the two. The entire cowl exit area is within the red line.....about 2/3 the area of the stock exit.



Yesterday I set the IO-390X at 24" initial and 2450 RPM, then climbed from 1500 to 7500 at only 100 knots. The stable CHT range was 328 -345F.....still too cold. I need to make another panel and shrink exit area even further.

This is a radical example. To be fair, I made a lot of mods during construction to optimize cooling performance. Further, from an aero standpoint the -8 (narrow belly, exit more forward)may be a little easier to cool than the -7 (wide belly, exit more aft). However, we all know of well crafted RV's with stock cowls and baffles and no cooling issues. I'd suggest optimizing what you have before cutting bigger or more holes in the bottom of a cowl.
 
How to lean?

Not trying to hijack your thread, Sonny, but I have been wondering what the procedure is for leaning a carburated engine considering LOP or ROP operations. How do you actually determine the peak? I'm a bit chicken of operating in that area, so I do the old standard and do the big pull until I get roughness and then enrich until the engine runs smoothly. To determine the peak, do you actually hold at the rough point and then check temperatures? Do you lean from this point and watch the change in temps? How long does this typically take? As I said, I'm a bit worried about operating at this point and have a lack of understanding. My engine does well with the big pull, but I'd like to check and see if it can be improved on. I typically enrich until smooth, and then if EGT's are over 1450F, enrich a bit further until about 1450 for the highest. They all seem to be fairly close, <50F delta.

Radomir (and anyone else who came up with a best practice), I'd be interested in how you operated your engine.
 
I use the engine monitor for that.. it makes things easier... Pull back power if you're worried about breaking something and lean any way you want. I prefer just normal linear leaning.. no big pulls..


If you're coming down in a few weeks, let's go flying and we can play with it..

PS.. *never* use an arbitrary EGT number for leaning.. it just doesn't make sense..
 
trib said:
Not trying to hijack your thread, Sonny, but I have been wondering what the procedure is for leaning a carburated engine considering LOP or ROP operations. How do you actually determine the peak? I'm a bit chicken of operating in that area, so I do the old standard and do the big pull until I get roughness and then enrich until the engine runs smoothly. To determine the peak, do you actually hold at the rough point and then check temperatures? Do you lean from this point and watch the change in temps? How long does this typically take? As I said, I'm a bit worried about operating at this point and have a lack of understanding. My engine does well with the big pull, but I'd like to check and see if it can be improved on. I typically enrich until smooth, and then if EGT's are over 1450F, enrich a bit further until about 1450 for the highest. They all seem to be fairly close, <50F delta.

Radomir (and anyone else who came up with a best practice), I'd be interested in how you operated your engine.
Click to expand...

Hi Tim,
I didn't start leaning until after 50 hours, per ECI's recommendation. But, now that I do lean, I make sure I'm at 75% power or less. Whether that's because of Density Altitude, or just pulling the power back. Anyway, I just pull mixture slowly until I get roughness, and then I note EGT. It's typically right around 1400-degrees F. At that point, I richen it up 75 to 100 degrees and call it good.

I'm sure there's a better way, more effective way to do it, but I haven't learned it yet! On my recent flight to Reno I was burning almost exactly 10 gph. Not great, but better than full rich by far.
 
Radomir and Sonny,

OK, so how long do you let it stabilize to check the peak temp? I use the eng monitor, but don't let it hang at the rough point. Once I pull back to the rough point (what I've heard called the big pull), I gently enrich until it runs smoothly, then check EGT. This doesn't give the transient time to die down, so EGT's are actually lower when I begin enriching from the rough point until smooth. If over 1450 at the smooth point, then I enrich it a little further. Not sure why, just initially was concerned I was a little high and figured if leaning it ROP until it ran smooth was good, a little richer wouldn't hurt if above 1450. I know not to use this as a temperature to lean to, but only use it in a conservative manner for this self-imposed peak operating EGT.

Radomir, do you use the vernier and keep leaning until you see a temperature drop- is that how you determine the peak? Does it run rough at this point? I guess once you determine that, then you would enrich 50-100F.

Oh, and yes I'm planning on coming to Charlotte on either 11/6 if weather is decent, 11/7 as the rain date. I'm looking forward to seeing TeamRV. More than likely there will be several other RVs with me.
 
Tim, it sounds like you're getting roughness lean of peak. The reason it looks that way is that I'm assuming your EGT readings should be close to instantaneous. The "transient time to die down" that you mentioned should be only a couple seconds. Unless you're not using digital gauges...then maybe it's longer. My EFIS changes very fast, though.

Anyway, the reason it seems your LOP is because you're EGT actually rises when you start richening it up. This, of course, is predicated on the fact that I'm right about your readings being instantaneous.
 
High CHT's

Based on what your saying, you and I had the same results. Nothing you do will make any significant benefit, sorry to break it to you.

I used to chase this rabbit into his hole.

My 7A was built with at fixed pitch prop and a Carb on a 360.
I have a full engine monitor from GRT and all new probes. I could not get my CHT's below 420 on a hot afternoon and had to step climb to get to altitude.
So I went on a journey. I first put silicone in between the cylinders, put washers in front and rear of the baffles to aid in cooling. I changed out my baffle seals to help with directing cooling. I closed off the upper cowl fiberglass inside humps, cant remember what we call them. I change to a constant speep prop, this had no effect of cooling but did give my 7 way cool performance. I added Avblend and more expensive oil. I changed probes to check them for consistancy. I also calibrated my Carb. I put up with this for 760 hours.

I'm sure I have forgotten many other things I tried in vain. It's not your airflow either in or out.

Nothing made a meanigful change. Untill one day I found the magic bullet.

I ran out and bought it. It was more expensive.

I now have this installed on my plane, here are the results. my no. 3 cylinder will not get above 300 in cruise when it used to be 385, I can climb to 8000' at 85 knots without stopping for cooling off at 2 thousand feet increments on the hotest day. My temps are fantastic all within 15 degrees of each other the hotest in lean cruise is 340 and the hotest in climb never gets above 380 EVER.

I have found the fountian of Cooling youth.

Its called ....

FUEL INJECTION.

Ditch the carb

7A 816 hours
Team RV
 
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tadsargent said:
Ditch the carb

7A 816 hours
Click to expand...

Hi Tad,
Your CHT's seem a lot higher than mine, so I can understand your motivation to find a solution. Mine are in the mid 380's at cruise, so I'm OK...would prefer lower, though. That aside, I fail to see how Fuel Injection can lower your temps by almost 100-degrees F. Care to explain? :confused:
 
Just guessing....

Just guessing that it would have been a lot cheaper for Tad to have merely drilled the jet in his carb!:p
 
I would suggest that your engine is running too lean to begin with. Change the port size in the carb to cause it to run richer and you will see lower cylinder temperatures. I have had this experience on numerous engines.
 
I have an IO-360 with Airflow Performance injection. I have balanced all the injectors so my cylinders peak at about the same time. I run lean of peak in cruise all the time now. Here is what is interesting temp wise. At 10,000' running 2450rpm 50 degrees rich of peak I will typically see cyl hd temps in the 375degree range and oil temp 205. leaned to 50 lop my cyl hd temps are 330-335 and oil 195. Don
 
No, not at all.... false economy. If he did that, he'd still be burning ~10gph, instead of a smidge over 7 that he does now. I've said it here before, and I can only say it again.. if you're burning 10gph, you should "fix" that and look into LOP.. it *will* be cheaper in the long run.


PCHunt said:
Just guessing that it would have been a lot cheaper for Tad to have merely drilled the jet in his carb!:p
Click to expand...
 
Radomir said:
No, not at all.... false economy. If he did that, he'd still be burning ~10gph, instead of a smidge over 7 that he does now. I've said it here before, and I can only say it again.. if you're burning 10gph, you should "fix" that and look into LOP.. it *will* be cheaper in the long run.
Click to expand...

:confused: Not sure why drilling a jet would be "false economy"? My thought was that the high CHT's might possibly be a result of running too lean. With a drilled jet, you can still lean out to the same fuel flow in cruise, while having proper mixtures at higher power settings.

If the jet is too small, you can't make the mixture richer. But it the jet is a wee bit too big, you can always lean it out. Here's a good discussion of drilling a jet: http://gikonfly.blogspot.com/2009/01/lean-carb-enlarge-that-jet.html


LOP is rare in a carbureted engine. He went FI, so your LOP comment should work for him.

My $.02.

Just thinkiing some more, maybe your "false economy" comment means that in the Long Run, he will burn less fuel by being able to run LOP, and thus the change to FI will be more economical in the end. :cool:
 
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Temps

LostPilot, I can't explain the How, I can only offer the what. If I had to answer then I would say the fuel delivery is dramatically more efficient with a stream of fuel being put onto the intake valve.

My carb jet was just shy of the largest one Kelly made. I spoke to Kelly several times and they told me the jet change would make a marginal difference.

You never hear of an injected motor running hot, at least I never did. Your setup works, If you don't like the numbers you are seeing don't look at them, they are not out of line for a Carb. However, if you want a change go Injected.

As for drilling the Jet, I owe it to Team RV to have an excellent operating machine for the task I am challenged with, I was not going to drill any part of my fuel delivery system in an attempt to "fix" something, nor was I up to fooling around with a carb.

Radomir and I worked on this for many hours, He can back any claim I make, as can Ron Schreck

It works fantastic now and the only thing I did was remove the Carb.
 
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With your typical aircraft fuel injection system, you've got liquid fuel being sprayed right into the intake port of the cylinder head itself. It should come as no surprise that this pulls a lot of extra heat away as the fuel vaporizes and cools dramatically as it gets sucked into the cylinder during the intake stroke.

In a carbureted Lyc, most of the fuel vaporization (and the cooling that happens during that process) is happening down below your engine, inside the carburetor and sump plenum chamber, then the air/fuel vapor mixture is getting heated up as it travels up thru the sump plenum, then the intake runner tubes, and by the time it reaches the intake ports it has warmed up considerably. Very few suspended droplets of liquid fuel are remaining in the stream by then to do much cooling by means of evaporation.
 
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I fought high CHT forever.

The last and best fix is to drill out the jet.

You just got to have more fuel to cool with on climb out.

You can still pull the mixture and cut the fuel burn for economy.

Its easy and works.
 
New Oil Cooler update

I finally had the chance to fly this weekend with the new 10-row oil cooler. I can't give a real comparison because the OAT's were 40 degrees cooler than before! But, the oil temp never went above 172 (F) with the outside temp of 50. That's very reassuring.

Also, the CHTs appeared to be much lower, I'm guessing because the oil was dissapating more heat (and of course the cooler outside air). They were pretty solidly in the 350's. I am curious how much of an internal temp difference the OAT makes. I'd like to think that it's relavent, just not the most significant thing to keep temps down.

I'm looking forward to next summer when the temps are back up! Maybe this weekend it'll get above 65 and I can try it again. So far, I'm pretty happy.
 
That's really good news!

For what it's worth... I'm still getting just about the same CHT and oil temps in the RV-8 with the cooler autumn outside air temps in the 70's-80's here in Texas as I was when they were in the 90's and 100's during the summer. The cooler weather isn't really impacting the engine operating temps much at all yet for us.

Much better to need to install an oil cooler block-off plate for winter flying than not having enough oil cooling capacity when you need it ;)
 
Just wanted to give an update on this old thread. I'd had a few private messages asking how the new 10-row cooler is working out, and I hadn't been able to give a good response due to the flying weather not being hot enough. Well, last weekend it finally warmed up enough to get some good numbers.

At the highest, the OAT was only 83 degrees F, but I managed to push the airplane pretty hard for 30 minutes, and threw in some maneuvering to get the temps up and slow the airflow down. My oil temp got up to 205 (F), but after levelling off and heading home it went back down to the high 190's. Late last year I departed for Reno around 9 a.m. one morning and I don't think the OAT's were above 80...and after 30 minutes of level flying at a fairly high power setting, my oil temps hit 232 F.

It may be too early to give the new cooler 2 thumbs up, but it's looking pretty good so far.
 
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How are your oil temps holding?

Sonny,

After 2 summers with the large cooler, what are your results? Were you ableto mount the 10 row cooler on the baffle?
 
Hi Tim,
Yes, just barely. It did a great job of dropping my oil temps 15 degrees. Instead of getting into the 230's at the highest, I was getting 218 or so. Along with blocking all the leaks in the plenum, blocking the heater scat tube in the summer, and adding the curved cowl-exit ramp, I now haven't seen my temps go above 210.
 
Sonny,

Do you have any pictures of the curved cowl exit ramp? I replaced my cooler with the supposedly more efficient, definitely more costly (but same size) Aero Classics cooler, but had no change in performance. I would have thought with over 50% more fin surface area it would have made a difference, but no joy. It is a pretty cooler though. On my 6A, I don't see fitting a larger cooler on the baffle being possible. My temps aren't too bad. I can keep it below 210 during cruise on the hottest days if I don't lean it out to the max. I'd like to get temps <200 and be able to lean for the most economical cruise. I was thinking of bumping the cowl outlet down 3/4" as I've seen in a newsletter to increase the outlet area about 25%. I've heard a couple talk about the cowl ramp curve but not seen any or heard of definitive results. I was also thinking about moving the cooler to the firewall and use the ducted cooling method, not on the baffle. What do you think of these and what's your feeling on likelihood of success? I think my approach would be to first try the curved ramp, since it is on the interior and would not affect anything else, then try enlarging the cowl outlet, then go to the firewall, in that order.

Any advice would be appreciated.

Tim
 
Tim,
I also tried the oil cooler upgrade with similar results. But using the exit air firewall ramp that Sonny described in earlier posts has had a significant effect. Here are some data form my AFS EFIS for two fairly similar flights at near full power on a hot day. I saw decreased oil temperature, increased TAS and decreased CHT. The beneficial effects have been consitent over every operating range.

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Bob Cowan
RV-7A 200+ hrs
 
Thanks Bob, Dave and Trina. I'll head in that direction. The picture makes everything clear for the exit curve. I'll put that in and report back on the results, then see if I go the next step and modify the fiberglass. Not looking forward to messing up my paint, so I'll do that only if I don't get any/enough benefit from the curve.
 
trib said:
then see if I go the next step and modify the fiberglass. Not looking forward to messing up my paint
Click to expand...
We have the bottom of the cowl secured with screws. So, before I cut I removed the screws and replaced them with 1/2' spacers and longer screws to see if the cut would be worth the effort.
 
erich weaver said:
Hmmm, an increase in cooling airflow resulting in a speed increase? Not what I would expect. Erich
Click to expand...

Exactly what we measured too (in nearly identical conditions). :eek:
Also noticeable was an audible increase in cooling exit air.

Study all of the many NACA cooling studies and it may change expectations.
 
MauiLvrs said:
Exactly what we measured too (in nearly identical conditions). Also noticeable was an audible increase in cooling exit air.
Study all of the many NACA cooling studies and it may change expectations.
Click to expand...

Dave, you're claiming a measured speed increase with the enlarged exit area, or just a drop in CHT?

erich weaver said:
Hmmm, an increase in cooling airflow resulting in a speed increase? Not what I would expect.
Click to expand...

From Raymer, Dc = M (Vi - Vo). An increase in mass flow can be offset by an increase in exit velocity (i.e. a decrease in velocity loss, freestream (Vi) less outlet velocity (Vo)). Does the radiused firewall lip increase exit velocity? Probably......we just don't know how much.

Note that as you develop the system to be closer to freestream velocity at the exit, the mass quantity matters less and less. Even an unlimited mass x zero momentum loss is zero cooling drag. We'll never get there with this system configuration, but it's the right direction.
 
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Sorry for the late response, Tim, but Bob's picture is identical to mine. So much so, that I thought he actually reposted the picture of my exit ramp! I have those pictures posted on here somewhere, Tim but I can't remember the title of the thread. Not that you need it anymore, I suppose.

Either way, Bob's results are very similar to mine. I had a 8 degree (F) drop after adding the ramp. My CHT's also appeared to be lower, too...but I still haven't gotten around to doing a top speed run to see if it's any faster. Well, not the "triangular course" speed run, anyway. I did manage to find smooth enough air a few weekends ago and saw that my TAS was a couple mph higher. Not sure I can trust it without doing a real test, though.
 
My largest speed gain was from lower cowl baffling

All but the final configuration caused decreases in speed compared to the stock arrangement. The final configuration is a curved baffle sealed to the back of the engine stock baffle and extending in a smooth curve to the bottom of the fuselage, two vertical baffles angled in from the side of the cowl to the curved baffle to the width of the outlet opening and two horizontal baffles just below the cowl split line blocking air flow back up past the valve covers and into the area behind the curved baffle in front of the firewall. The two horizontal baffles were the last added and until they were added the curved and wedge baffles had decreased the speed two knots below my baseline stock speed. After they were added the speed jumped 6 kts for a net gain of 4 kts. I have a stack of aluminum, rubber, rivets and platenuts from many other baffle experiments that only reduced the speed. My latest mod continues the curved baffle down below the fuselage and then back up to it with a cowl zone 3 vent at the trailing edge and a vented cover adds another 1.7+ kts. So, there is speed to be gained with altering the stock lower cowl configuration in an RV-6A at least.

I personally have never had a cooling problem but last Friday evening when I was at Coeur D'Alene, ID for the Pappy Boyington Memorial Cup race we were sitting around a table waiting for the BBQ talking airplane stuff. One fellow said that he had an oil temperature problem and the way he finally solved it was by adding a second smaller oil cooler plumbed in series with the original cooler. I was glad to read in this thread finally that the poster went to a larger oil cooler and solved the problem since to two solutions are the same with a different implementation.

Off topic - I stayed overnight in Boise on my way back to Arkansas Saturday night after flying out from COE after the race for a brief visit to the Van's Homecoming in Independence, OR. That was some of the most extensive smoke I have ever seen. Around the Malad City VOR it was effectively IMC and it didn't clear up until well into Wyoming near Rock Springs on Sunday.

Bob Axsom
 
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