estradajae

Hi Everyone

I just recently bought a Su-31 from Black Horse (seems to be the same from Phoenix). The quality is awesome and seems to be according to the pictures of the early versions, that lot of improvements are done.... However I had maidened the plane with a new TT f-75s, the engine was not fully broken in yet, but was working o.k... the thing is that I made initial runn in without the cowl, and then cowled and fly (big mistake not checking the temperature etc...) I had also problem with fuel bubbles and all together may have caused the engine failure...but the thing is that the engine was severe overheated (whatever reason)... I want to know if you guys who are using the same plane with a 4 stroke have ever had cooling problems? and what kind of mods have you done to improve it, I would appreciate pictures and ideas.

Saludos

Jorge

ChuckW

Make sure you aren't running too lean. In a cowled engine it is important to be slightly rich to help with cooling. Try adjusting it for maximum RPM then richening slightly until it drops 200-500 RPM.

It could also be poor airflow around the engine. Sometimes people make a plywood baffle that blocks most of the cowl inlet area and focuses all of the incoming air right onto the engine.

Hope this helps.

estradajae

Hi

Thanks for answering..
I know about lean...the thing is I want to know if others have a cowl induced overheating...and what solutions were implemented =)

The engine went out probably because a lean run, sure, it is new and not completed the breaking in.

Jorge

psuguru

The outlet holes need to be a lot bigger than the inlet and positioned so that the air doesn't just whistle straight through without going past the engine.
The killers are high rpm with a high throttle setting using high nitro content with low oil content in a cowl. Perm any 2 from 5 and you can be in trouble.

For initial flights on a new engine, you need to see smoke or vapour from the exhaust.

estradajae

Thank you for answering,
Yes, I know about the ratios of the inlet area.... but my question is if anyone have had troubles and how thay have worked it out.

By the way... you are wrong about the nitro content and engine temperature.... The stoichiometric ratio of nitromethane is lower than methanol (with air), which means that methanol needs more air than nitro to burn, it means, you have to open the needles to compensate, which means, more fuel through the engine..which means more cooling.... you can do a search in glow engines forum...

Anyone with a Black Horse/ Phoenix Su-31?

Saludos,

psuguru

So your contention is that engines running high nitromethane content run cooler?

Katman1

I would suspect the fact that you flew it before it was fully broke in and maybe it ran too lean too soon much sooner than it just over heating because of not enough air flow.

Korps

My .61 2 stroke was running at a high temperature inside my cowl - we just cut in an extra hole horizontaly across the cowl at the bottom. We did make it in a shape of a smile The other two vents at the top of the cowl gives it two eyes, the newly cut in vent a mouth/smile and the spinner it's nose - So whenever you fly towards yourself it smiles at you Then it crashed...the cowl was smashed...and it wasn't smiling no more []