Squish angles, turbulence and detonation...

[Blaner]

Hey, one for the pros to answer...
Im researching squish angles and how it directly affects max squish velocity. I am looking to modify my blasters head to get better efficiency from its combustion process.
When cutting the squish areas angle, do we cut it at the same angle as the piston dome angle? surely this would allow the mixture to be squished into the combustion dome at the same rate as the piston compresses the mixture thus preventing detonation? would it benefit me at all to cut the squish area at an greater angle than that of the piston dome or is a waste of time and turbulence?

From what I understand, skimming the head in order to increase compression without compentsating with adjusting squish bands we will end up with detonation?

Also, what is the highest CORRECTED compression ration that could be run on 95octane fuel

Lastly, is it best to polish my piston crown and the entire combustion chamber? will a surface left slightly rough generate greater turbulence or do smooth surfaces do it better?

 

[OConnor Racing]

If you’re trying to make a head with a squish band that works, you’re going to have to cut about .130 off of the sealing surface. Cut the squish angle @ 11 – 12 degrees and then start cutting the combustion chamber until you get the cc’s your looking for. A hemispherical chamber with a 50% band works well. The compressed thickness of the gasket is about .030 and the piston could be in any number of places when it’s @ TDC. Shoot for about .045 from the top of the piston to the top of the cylinder head to be on the safe side. You’re probably going to end up cutting .010 - .020 off of the top of the cylinder. Graham Bell explains this very well in his book. Just search his name and two stroke tuning. Short read but very helpful.

 

[Blaner]

Ok, those are the figures ive been working with according to the Mcdizzy site. it gives me the required squish thicknesses and so on. Id love to use a software package to calculate it myself instead of using someone elses data but as a student, they a bit pricey! Thanks for your input, i seem to be on the right track!

Anyone else have anything to add??

 

[OConnor Racing]

2 Stroke Tuners Handbook by Gordon Jennings

http://www.kreidler.nl/artikelen/performance-tuning-graham-bell/performance-tuning-graham-bell.pdf

I built a Mac Dizzy engine a couple of years ago and still own it. Works pretty good and a bunch better than stock. Chech out the two links I sent you. This should help. The Dizzy porting is kind of mild.

 

[Little-J]

yeah, I know what you mean about the software.. I would love to model my engine on ricardo pulse but it costs about 1000$ to get the licence and then you still have to figure out how to use it.. what are you studying?

 

[Blaner]

Thanks guys, im actually studying a Bsc in geosciences, i did a bit of mechanical engineering a few years ago,but found i prefer keeping that sort of thing as a hobby, the maths seemed to overshadow the actual concept and it was killing my interest in the topic, as a hobby its far more enjoyable! what can i say... I like rocks

 

[brandoz28]

i know what you mean man......i lost a lot of interest in playing guitar when i was teaching 25+ lessons a week. but damn do i miss that money

 

[xjma]

Thanks guys, im actually studying a Bsc in geosciences, i did a bit of mechanical engineering a few years ago,but found i prefer keeping that sort of thing as a hobby, the maths seemed to overshadow the actual concept and it was killing my interest in the topic, as a hobby its far more enjoyable! what can i say... I like rocks

What's up man, I've got an associates in ME and while going for my BS decided I really didn't want to be an actual ME, so now I'm a hydrogeologist....I get to apply math to the real world! Geology is the sh*t, keep it up man! Must be sweet to be studying geo in South Africa!!