Oil Temps Again

[Kyler]

No, it isn't. Unless ducted properly the incoming air will simply try to go around the cooler because that is the path of least resistance. 15 minutes with some scrap coroplast (the corrugated plastic used for election signs and the like) and some duct tape would probably get you a workable duct to try before you do anything else. I bet you can cut the inlet hole size by 2/3 if you put a sealed duct in to force the air through the cooler.

Ideally the inlet hole area is quite a bit smaller than the cooler area and the ducting smoothly expands from the inlet out to the cooler. This slows the air down and lets it recover pressure before passing through the cooler fins, then the exhaust air should be ducted smoothly out into a low pressure zone. Done really well it results in a low temperature jet engine that actually produces a bit of thrust. I understand that F1 cars have close to zero cooling drag because the thrust offsets the drag of forcing the air through the radiators.

Light aircraft cool a couple hundred horsepower with less inlet area than you have there because they carefully duct the air in and force it through jackets that make it go through the engine cooling fins. You can use the same approach to improve your system as well. I would make your test duct up to go over top of the overflow bottle and would just block off the portion of the inlet hole that is in front of the bottle. From what I see in the pic it looks like that would leave you about 3/4 of the inlet area to feed the cooler, which should be way more than you need.

PM me if you want to discuss details off forum, or we can keep going here if you like.


Mark

tomorrow I'll get some better photos and post here. Just finished unloading the rig and its time for some beers. I don't mind the open discussion but hope we can focus on airflow and oil cooling. If not, we'll take it off-line.

[Kyler]

Here are some bigger pics of the oil cooler

The black tray is a mount for my Nexus. I use it for datalogging with the RaceChrono app.

Looks like I can get a reasonably close fit to the cooler but will have to slot around the oil lines.

[mmattockx]

Looks like I can get a reasonably close fit to the cooler but will have to slot around the oil lines.

Those are good shots, I can see what you have there. My first test attempt would be a simple rectangular duct as I described before, straight from the inlet hole to the face of the cooler just to see what happens to the oil temps. Slotting around the lines is no big issue for the initial testing, just tape off the slots once the duct is in place. I would put the bottom of the duct straight over the oil filter just for convenience. If you can manage it, try to seal the duct to the cooler face as well, to force the incoming air through the cooler instead of around it. Even sealing 2 or 3 sides will help a lot on that. I wouldn't worry about the exhaust side of the cooler for the moment, it looks to have a reasonable amount of area available for the hot air to get out and the space behind the bodywork there should be a fairly low pressure zone to draw the air through the cooler.

Depending on the results you can then go to refining the amount of inlet area to balance how much cooling you get and to work around the other components you have in the same space. What do you do for getting cooling air to the engine itself? It may be running very hot and cooking the oil along the way.

When do you get to the track next?


Mark

[Kyler]

Depending on the results you can then go to refining the amount of inlet area to balance how much cooling you get and to work around the other components you have in the same space. What do you do for getting cooling air to the engine itself? It may be running very hot and cooking the oil along the way.

When do you get to the track next?

I like this plan. Is sorta what I was thinking too. I'll work on that this weekend. Next race is July 11-13 at NJMP - the Thunderbolt track. I race there twice in back-to-back weekends.

standby!

[Kyler]

This is interesting. It appears the thermocouple I used isn't compatible with the thermometer in the Koso gauge. I'll be ordering a new one.

I warmed the motor up to test the air flow through the cooler (see mod below and thanks to all the local politicians for donating their signs) and to get another oil sample.

First, because the oil filter is right in front of the cooler, I couldn't get the bottom of the ducting to the bottom of the oil cooler. It misses about 2" on the right and slopes to the left. If this works I'll move the oil filter and ensure I use all the cooler area. I put a 21" box fan in front of the oil cooler and you could definitely feel air moving through the cooler.

Then I decided to check the temperatures around the motor using my pyrometer. The temp gauge was reading 295 degrees.

Coming out of the motor (temp taken on the fitting) the oil was 195.

On the fins of the cooler on the input side, temp was 170.

On the fins of the cooler on the exit side, temp was 125 (45 deg drop)

Returning into the motor (temp taken on the fitting) the oil was 160 (35 deg drop).

Weird. Does anyone know how much temperature drop I should expect?

[GregT]

Those temps look pretty safe for a good quality race oil. The installation looks very similar to several rigs i see local to me but the late stuff - LCR's etc which are appearing here - have a better integrated air intake and duct sealing setup.
All you can do at this point is tracktest and see how the temps go.

[Kyler]

Those temps look pretty safe for a good quality race oil. The installation looks very similar to several rigs i see local to me but the late stuff - LCR's etc which are appearing here - have a better integrated air intake and duct sealing setup.
All you can do at this point is tracktest and see how the temps go.

Thanks! we'll know in two weeks. I'll post results here.

[Grimly]

I'm just wondering how much cooling burden is being shifted to the oil if the direct engine cooling is compromised. Drag is always a consideration, but as has been mentioned, low drag cooling can be attained.

[posplayr]

I'm just wondering how much cooling burden is being shifted to the oil if the direct engine cooling is compromised. Drag is always a consideration, but as has been mentioned, low drag cooling can be attained.

Obviously a lot; why else would a 750 run even full out overheat in 15 min.

And I would think you are quite right in bringing up cooling burden. This is an air cooled engine and there is going to be a limit to how much heat you can disapates through the oil no matter how much air you run brought the cooler. Carried to excess he might even see very cool oil temps but run high head temps.

[Grimly]

Yep, I would guess it needs more airflow to barrel and head, even if the rider is a bit toasted. Even at that, a solution can be reached - perhaps the Manx TT sidecar outfits of the 70s and 80s could be robbed for design pointers - they did more than 15 minute stints and (usually) didn't expire too much.

[GregT]

Aerodynamically, a classic or post classic sidecar outfit is roughly equivalent to doing a top speed run in your van with all the doors and windows open - and a passenger hanging out the side door...

Historically, the solution to engine cooling problems was to use Methanol fuel which sidestepped most of the cooling issues. Unfortunately, a lot (not all ) of the sanctioning bodies will not allow it's use now which can lead to the problems seen here.

Compounding the problem is the overriding requirement that the outfit appear correct for the period. This limits aerodynamics to subtle improvements at best.

I'd hope that the oil cooler installation will mitigate the overheating problems enough to get a decent season out of the rig.

[Kyler]

the good news so far is the oil analysis reports haven't shown any signs of oil degradation due to heat. At worst I'll have to change oil after every race weekend. That is a small price to pay.

[Kyler]

I'm just wondering how much cooling burden is being shifted to the oil if the direct engine cooling is compromised. Drag is always a consideration, but as has been mentioned, low drag cooling can be attained.

The NACA ducts (although not period but tolerated) point at the jugs. That is the best I can do on that right now. I'll puzzle through cooling more after the next race and have more data. More to come!

[Kyler]

I'd hope that the oil cooler installation will mitigate the overheating problems enough to get a decent season out of the rig.

Same here; one race down and 6 to go. My plan is to drop a GS1100 motor in it over the winter. I've saw a lot of GS1168 motors on the Phillips Island entry sheet. What is the URL of the NZ sidecar club? I might be able to get more ideas from them.

[posplayr]

Aerodynamically, a classic or post classic sidecar outfit is roughly equivalent to doing a top speed run in your van with all the doors and windows open - and a passenger hanging out the side door...

Uhhhhhh not sure that I can accept that even on face value.

At a given speed and altitude, aerodynamic drag is principally a function of shape factor. A flat plate Cd is approx 1.2. A square van with doors open might have a Cd somewhat above 1, I suspect the Cd of that faired trike is quite a bit lower than 1.0. A reasonably aerodynamic car these days is like .35, so I would guess that bike is probably no worse than 0.75.

Horsepower required to achieve a specific velocity is proportional to the Cd times the cube of velocity. So by a natural process the design probably evolved to one of much higher efficiency that the van, part of the reason for the closed off engine venting.

Frontal inlet drag is going to be largely a function of area alone (ignoring flow out of the cooler.) , but I suspect overall engine cooling efficiency is very much dependent of whether that are is allocated to engine air flow v.s. cooler air flow. That optimization is something that I doubt has been fully explored.

In fact if it was that bad, you couldn't make it any worse by letting some of the frontal area catch some wind to cool the engine instead of the oil cooler.