Glow Engines Discuss RC glow engines

Valve overlap on 4 strokes

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Old 09-15-2012, 06:11 AM
  #26  
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Default RE: Valve overlap on 4 strokes

I think the original project engine was a Saito 72.
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Old 09-15-2012, 06:27 AM
  #27  
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Default RE: Valve overlap on 4 strokes

ORIGINAL: earlwb

ORIGINAL: Old Fart
Hey earl that looks interesting and do you fly it??? i'm over bent eights and horsepower tricky things to do with that,does the engine sound different and how does it throttle up?would like to hear it if you post a vid somewhere for us.
I wish. The miniature roots blower was made by a machining firm in California (if I remember right), to promote their business. They didn't make any more, other than a few for their own purposes. No one outside of OS with their 1.20 supercharged roots blower pattern engine has made any that I know of. I think there were some videos made, I will post them if I find them.

There is a small company that makes superchargers for RC cars, but I honestly don't know how well they work. I have thought about getting one to see how it performs, but I haven't yet. That same business also offers various nitrous oxide injection systems for RC cars too. http://www.rbinnovations.com/default.asp

Here is the original thread about it here : http://www.rcuniverse.com/forum/m_15.../anchor/tm.htm

Their problem is that the 4 stroke engine needs to be modified for the supercharger, plus the supercharger has to be made for a specific engine displacement too. Glow engines tend to be more finicky in this way. So they never went into production with it.
The RB Innovations supercharger is a hoax. I got one in a box of spare parts from a friend for free. I'm trying to get a picture of the insides uploaded to Photobucket, but having issues with photobucket. Its not a sealed unit, uses rubber bands to drive the pulleys, and just looks cheap. I dont believe it has ball bearings in it either.

I doubt it will work at all, though I have entertained the idea of experiementing with it some....
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Old 09-15-2012, 09:45 AM
  #28  
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Default RE: Valve overlap on 4 strokes

Yeah it is one of those famous debatable quandaries we see from time to time.
I think it works better in the car or trucks than in an airplane. The people who have reported using them, state that it helps improve the power or torque at the lower end of the RPMs.But not any performance boost at WOT. Thus they get a little better acceleration coming out of a turn at low speed. Truck guys like it for that same reason more power at the bottom end of the RPM range. Some guys reported it was easier to tune or adjust the engine with one on too. I suspect the o-ring belt drive slips too much at WOT so it loses efficiency at higher RPMs.

Anyway if someone is winning at the track using one of the superchargers, then everyone else will get one too. It doesn't matter if the winner is a really good driver or not.


It always reminded me of the guys who hooked up leaf blowers to their engines to get a poor man's supercharger. Then there were the scooter guys hooking up 12v blower fans also.

Turbo chargers do have a big scale effect problem. The smallest turbo charger I know of was the one that Puegeot sold on some of their high end 125cc scooters in Europe. Even then it didn't give as much of a boost as people might have hoped for. I think that 250cc was the smallest anyone could go with a turbo charger and get it to work reasonably well.

So I think the supercharger has the same problem with model glow engines, in that the scale effect causes them to lose a lot of efficiency. Making the performance increase questionable.



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Old 09-15-2012, 10:51 AM
  #29  
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Default RE: Valve overlap on 4 strokes

ORIGINAL: earlwb

Yeah it is one of those famous debatable quandaries we see from time to time.
I think it works better in the car or trucks than in an airplane. The people who have reported using them, state that it helps improve the power or torque at the lower end of the RPMs.But not any performance boost at WOT. Thus they get a little better acceleration coming out of a turn at low speed. Truck guys like it for that same reason more power at the bottom end of the RPM range. Some guys reported it was easier to tune or adjust the engine with one on too. I suspect the o-ring belt drive slips too much at WOT so it loses efficiency at higher RPMs.

Anyway if someone is winning at the track using one of the superchargers, then everyone else will get one too. It doesn't matter if the winner is a really good driver or not.


It always reminded me of the guys who hooked up leaf blowers to their engines to get a poor man's supercharger. Then there were the scooter guys hooking up 12v blower fans also.

Turbo chargers do have a big scale effect problem. The smallest turbo charger I know of was the one that Puegeot sold on some of their high end 125cc scooters in Europe. Even then it didn't give as much of a boost as people might have hoped for. I think that 250cc was the smallest anyone could go with a turbo charger and get it to work reasonably well.

So I think the supercharger has the same problem with model glow engines, in that the scale effect causes them to lose a lot of efficiency. Making the performance increase questionable.

The main issue I see with a supercharger actually working (provided the unit itself actually works, which I doubt it does) is the parasitic losses may negate the positive effects, as well as both intake and exhaust ports being open at the same time. In this instance, under boost, some of the fuel mixture would blow out the exhaust. Without a tuned exhaust to cram it back into the combustion chamber, I think you would lose efficiency that way (as well as a leaner fuel mixture in the chamber)....

There was recently a discussion in the car forums about a turbocharger working on a 2-stroke model engine, namely a car engine. There are a lot of guys that feel the same way towards turbos as they do superchargers but turbochargers have been used on snowmobiles for many many years. The theory goes that the backpressure the turbine creates on the exhaust is enough of a restriction to keep the air/fuel mix from blowing out the exhaust port. Now whether or not it would work with an engine as small as .15ci or .20ci is another story. I had seen a picture online somewhere of a very small turbocharger mounted to a 2.5cc rc car engine but no video of it operating. I'll see if I can find that picture again, it was quite.... "cute".

edit: It appears to work... The guy's tuning is pretty cruddy so the engine quits a few times.. Maybe it works?
http://www.youtube.com/watch?v=lgBuI...eature=related
Another one: http://www.youtube.com/watch?v=tuJ703Kb-RA Engine not running though.

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Old 09-15-2012, 12:27 PM
  #30  
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Default RE: Valve overlap on 4 strokes

that crank driven turbo really needs to spin 80-100,000 to work good enough to make worth while. would be better if belt drive with cogs in it than a oring. the carb needs to be a pull thru set up also if it isnt.

i dont thinks its worth the 250 dollars they are asking for it. just learn to drive better
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