BMEP - a better way to describe power

[Pursuvant]

I saw FortNine with the Kaw zx4rr, and he used a chalkboard formula that is another way to describe power irrespective of engine size. BMEP,  it's the average combustion pressure across one engine stroke.

I started to poke at the formula but quickly discovered an online calculator here . And some numbers:

The Yamaha MT's...

MT-07  180 psi

MT-09  188 psi

 

For reference, two Kawasaki's...

1984 GPZ 900R   171 psi

2020 ZX10R.  210 psi

You can see how it's another way to compare, besides shouting hp.

And this is why the BMEP is fun. In 1985 I acquired a Kaw gpz550 after retiring a 1982 kz650. And at that time I was afraid of a GPZ 750 and really afraid of GPZ 900.

[shinyribs]

Everything power related ends up boiling down to compression, or cylinder pressure. 

Four stroke cam profiles, cylinder head port layout, number/size of valves and of course piston crown height to determine compression ratio all work together to determine not only how much power can be produced, but where in the rev range the power gets made.

Driving4answers ( I think that's how it's spelled) is a YouTube channel that has great videos describing why certain engines do certain things. He has a video on 270° twins with offset cylinders, such as the CP2, and how those two features work together to affect how power is made. Way more than just , " it's sounds like a v twin". It's a really interesting concept, especially the offset cylinders, and how they really effect rod angle and compression at certain times. Check it out. I think you'd find it really interesting. 

[Pursuvant]

20 hours ago, shinyribs said:

Everything power related ends up boiling down to compression, or cylinder pressure

Driving4answers ( I think that's how it's spelled) is a YouTube channel... He has a video on 270° twins with offset cylinders, such as the CP2, and how those two features work together to affect how power is made. Way more than just , " it's sounds like a v twin". It's a really interesting concept, especially the offset cylinders, and how they really effect rod angle and compression at certain times. Check it out. I think you'd find it really interesting. 

That is a fantastic video

https://m.youtube.com/watch?v=uM-ycHS9uvw

I learned more from that video about the primal nature of cranks & firing, primary & secondary imbalance, crossplane, and wow the explanatory on power impulses where they occur on the circumference/rotating radial tires is great. And how a less powerful v4 firing 2 pistons similtaneously and not 180 degrees apart made moto gp not faster but quicker, and cut the number of pro rider high sides, just great.

Thank you @shinyribs, everybody is going to like this video

[shinyribs]

He really does a great job on his videos and he has a really good teaching style. I really hope his channel gains lots of subscribers so he can get rewarded for what he does. 

[shinyribs]

Here's the video explaining how cylinder offset affects rod angle and firing intervals.

 

https://youtu.be/gwtZkHoVMso