This is one of the better explanations of blowdown.
@MichaelForrestChnl
5 ай бұрын
What I brought new to the topic is the realization that the more you raise the exhaust port the more you decrease the trapped cylinder volume which is the true engine size.
@monster2269
5 ай бұрын
You are a smart Man Michael F. Thanks for the info. Well done.
@MichaelForrestChnl
5 ай бұрын
Thank you kindly. It's nice to be appreciated.
@Iggy900ss
5 ай бұрын
@@MichaelForrestChnl You really are appreciated, Michael! Your analyses, your explanations and your software taught me way more than all of the books I read and the experiments I made
@copisetic1104
5 ай бұрын
I believe that’s why exhaust ports were widened with bridge ports and chamfering to allow exhaust pressure to reduce enough to open the transfer ports.
@MichaelForrestChnl
5 ай бұрын
yes, the wider exhaust ports make it more effective so they don't have to be as tall so the trapped engine volume is greater
@MotorcyclesandArt
5 ай бұрын
Great video
@MichaelForrestChnl
5 ай бұрын
I just updated the Porting Calculator to also show a rough calculation of horsepower as well as transfer capacity (delivery ratio).
@nathansmith3608
5 ай бұрын
I'm pretty sure I remember learning a lot from your site like 8 years ago when I built a gas bike - it's cool to see you're making videos!
@mikeeiben3430
5 ай бұрын
I have an oil question. I have an older twin cylinder 4 stroke model airplane engine. It is a glow fuel engine that has been converted to gasoline with spark ignition. Glow fuel is methanol with 18 to 20 % oil and 5 to 15% nitromthane to improve power and ease tuning. Crankcase lubrication is from blow by. Connecting rods are made of bronze and that is the bearing. 20:1 mix ratio was recommended but people had had failures, so now 15:1 is recommended. I was advised by someone with much experience to run 10:1. After reading your paper on 2T oils and watching videos I decided to try Honda HP2 at 10:1. It seemed to be too much and or too thick. There was a nice amount of oil coming out of the crankcase breather tube and I felt that lubrication was superior. More recently I tried Amsoil Dominator at 15:1. It ran much better but I felt like there should be more oil coming from the breather tube. Do you think I am better off with an oil like Dominator at 10:1 that seems to burn off, or a higher quality oil like HP2 or Belray H1R that is ester, but at 15:1?
@MichaelForrestChnl
5 ай бұрын
I'm sorry but for head splitting questions I need some payment. That's work man. Actually you shouldn't ask me because I have no experience with engines like yours. All I can say is to look up the composition of Dominator on my oil page and then you'll probably scratch it off your list. www.dragonfly75.com/moto/oil.html
@matthewfredrickmfkrz1934
5 ай бұрын
Do piston rings next
@MichaelForrestChnl
5 ай бұрын
I doubt I know enough about the subject. All I could say that is informative is that rings are made soft or hard to match the type of cylinder lining. The hard surface of a "chrome" liner needs soft rings to conform to it, and a "soft" iron liner needs hard rings. When you ruin a chromed cylinder and insert an iron liner you also need to find rings that were made to be used on such a liner. I didn't do that when I changed to an iron liner on my KDX200 and had to have it resleeved about every 6 months because it wore down so fast with the stock rings.
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