DOHC Oil Cooler?

[bcware]

With stock internals and no forced induction I have to imagine that most failures will be due to oil breaking down and failing, not necessarily inherently high internal temperatures occurring while oil is still functioning properly. Unless you're racing of course and always running at very high rpms

 

[Scorpio1963]

Exactly BC the way the oil pump is inside the engine being mechanical and gear driven.Dont know haven't read every paragraph of this thread but there would have to be a tank with internal pump that could circulate the oil through a cooler.Im sure something like a transmission cooler for autos could be modified to work.You could mount it on the frame kinda like a radiator.Maybe there is a pump from another type of bike that would work.My problem I see even if this idea could come to life is the size,it would be large and bulky.As our oil expurt would say(said to be a compliment) just use a premium motor oil like synthetic and you wont have to worry about a cooler.I`ll add this extra 2 cents I guess its fine if you have the $ to build such a system and your perogitive to do so.I realy don't see any point but a waste of time in opinion.If keep your oil cooler is something you want yes buy another bike that has one on it already.Im sure Yamahas engineers thought of this when they built the engine.

 

[Scorpio1963]

This dam thread has got me thinking to hard today,instead of trying come up with a way to keep your engine cooler why not design a system with an electric fan as an accessory to the frame.This way while you are driving in stop and go traffic you always have a continues airflow on your engine.Makes more sense to me.:

 

[16VGTIDave]

BC, I'm not disagreeing with you. I doubt that an oil cooler will be needed, especially since the engine has lasted this long without it. That said, there is enough plastic (timing chain sliders) and rubber (seals) in the engine that high oil temps could degrade over time, that I thought it a valid point of discussion. Especially considering how scarce parts are becoming. I plan to be running my carb jetting as lean as I safely can for best economy to achieve my goal of 400+ km/tank from my 21L tank. Up until now I've been running slightly rich for peace of mind and averaging 5.24L/100km. Having the mixture on the lean side will obviously push the engine and oil temps up some. How high will be determined once I get back on the road. With my new gearing that will have the engine revving higher, more highway mileage, and I will have more weight carried on a daily basis.

Aaron, those are the kind of replies I was expecting from you! As I've been pondering this topic and getting input, I've been trying to mentally design a simple solution. The engine design doesn't lend itself to an easy, bolt on, solution. One thought I had this afternoon was to tap into the main oil galley via the right side engine cover, and have a minimum-pressure check valve to block oil flow below ~1.5Bar (~20 PSI). This would prevent oil from flowing through the cooler at idle and a corresponding pressure drop when the oil pressure is at its lowest. I'm intrigued by your cooling fan idea and will keep that in mind for the cylinder head.

This is still all just a mental exercise until I get some oil temp readings. But even if my riding doesn't justify an oil cooler, this info may help someone else in the future who does need one.

 

[bcware]

Another simple solution is also a water sprayer. A common mod for cars is an inter-cooler sprayer. The water evaporates and carries away the heat.

 

[16VGTIDave]

Yes, I know about water spray cooling. It can cause problems if not done correctly. Too hot an engine with too much water, and the cooling fins on the engine can shatter from the sudden temp change. Seen it on an aircraft engine that was flown in rain. Never mind having to carry water, a pump and spray system, and a control system. Might be ok on a drag bike, a 1/4 mile at a time. But less practical on a 12 or 16 hour long distance ride.

 

[willem]

how about an external water cooling system? If you could install a small 12V water pump and a radiator up in front of your headers, and route some thin cooling hoses in between your fins and around the engine wherever you have the space.. There are plenty of modern water-cooled bikes of which you can rip off a radiator with temp sensor and a fan (for long idling in hot weather). If it works on other bikes, why not on the xs400?

 

[Scorpio1963]

I was also thinking about this before I came up with the electric fan idea.How would you do it since most blocks have passage ways to circulate the water through the engine.Im almost certain the electric fan would be the best idea,You can rig a switch to turn it off while riding on the hiways and then turn it on while riding in stop and go traffic.I believe if done correctly it could even cool the oil down while your stopped at a light.
I also like the idea of adding more fins which could be added to the bottom of the engine if possible.I say if possible because I haven't see the bottom of dohc engine and don't know if theres room.It could be done rather easily on the sohc if you know how to weld and make the fins.This was something I was brain storming about.Since I mentioned the electric fan idea is it or would take extra voltage that are engines need to run because Im now thinking about doing the same thing on my bike.