<VV> What is squish?

jvhroberts at aol.com jvhroberts at aol.com
Tue Aug 11 15:20:11 EDT 2015

Two strokes have very different issues. for one thing, the lube oil reduces octane. Also, they depend heavily on a stratified charge to get the least mixing of the intake charge with the exhaust. Increasing squish on a two stroke invariably means more compression ratio. 
On a 4 stroke, you can modify the chamber shape and volume (rarely done on a two stroke) and get more squish ad maintain comp ratio. 



John Roberts


-----Original Message-----
From: Joel McGregor via VirtualVairs <virtualvairs at corvair.org>
To: virtualvairs <virtualvairs at corvair.org>
Sent: Tue, Aug 11, 2015 11:00 am
Subject: Re: <VV> What is squish?

Does anyone know why squish decreased detonation in 4 strokes and increases it
in 2 strokes?  Is it because the symmetrical way a 2 stroke head is generally
made causes everything to collide in the middle?
I know from experience that
it's very easy to get too much squish velocity in a 2 stroke and have serious
detonation problems.
Joel McGregor

-----Original Message-----
VirtualVairs [mailto:virtualvairs-bounces at corvair.org] On Behalf Of Matt Nall
via VirtualVairs
Subject: Re: <VV> What is squish?

To add to what mark
wrote.....which by the way is "Compression ratio".......

"Squish"  in a
Corvair head with the STEP  in it...as do most  engines  versus an "open
Chamber" [ in our case  Smog heads with domed pistons  and some early low hp
engines ]

Is the distance between the "step"  and the top of the
piston....... factory is usually approx. 0.080"

By  decreasing this to
approx 0.040"   you  get less pinging......yet have higher compression!  win

Matt Nall
Charleston, Oregon

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