piston to bore clearance

[garry inglis]

What new kit tell us more and is it true there only open 3 days a week

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[mick1]

What new kit tell us more and is it true there only open 3 days a week

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WHAT !!! .............they're opening an extra day

[holty]

What new kit tell us more and is it true there only open 3 days a week

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ive had it in my hand, piston port going to be available for smallblock and big block, barrel has a boost port and a split inlet with matching inlet manifold ,double transfers on each side, ive maybe said too much already but its going to be a big seller, nikasil lined and at a price that will amaze you, 200 cc for the smallblock, 200 and 225 for the big block, has big tuning potential.

[johnny650]

too big a gap on the rings will cause a massive loss in sealing pressure

could you give me a link to where you found this information muppet .
Not being funny but common sense tells me that a ring gap slightly larger than the recommended tolerance couldn't suddenly cause a 'Massive' loss in compression as you suggest but I'm happy to be proven wrong by facts figures and testing data
What sort of Psi loss are we talking here ?

[johnny650]

I think we far too readily believe stuff we hear from friends ,read on the net and in magazines that have no source or proof and just keep getting repeated until we accept that it must be true .

I did a little exploring on the net and found this very interesting article about ring gaps and effects on performance .
Written by an Automotive Engineer it relates some extensive testing done by AE on a Ford Kent engine on the effects of oversize ring gaps and effect on performance . It bores out what I suspected .

Short answer it has a negligible effect .......even at extreme oversized gaps.!

The truth is .....that it is the reduced tangental pressure of worn rings, (pressure that the rings exert on the walls of the cylinder), that cause blowby and heavy oil consumption not ring gaps.

http://www.diagnosticengineers.org/jour ... 20Gaps.php

[Muppet]

http://www.diagnosticengineers.org/jour ... 20Gaps.php
this only refers to fourstroke engines

[johnny650]

http://www.diagnosticengineers.org/jour ... 20Gaps.php
this only refers to fourstroke engines

All piston rings work in exactly the same way regardless of how many cylinders there are or what use the engine is put to.

Piston rings seal against the cylinder walls . Where is the difference on a 2 stroke cylinder ?

[Muppet]

from the very limited knowledge that I have of two strokes and four stroke I believe four strokes have valves that control and SEAL OFF the inlet and exhaust gasses keeping the apart; a two stroke doesn’t have valves it has a primary chamber and secondary chamber; the primary chamber is what holds the unburnt gasses below the piston and piston rings; if the rings can not effectively seal off both chambers from each other then this effect would be similar to leaking inlet and exhaust valves on a four stroke.
I’m most likely mistaken in my thinking of how the two stroke pump works im hoping someone with a knowledge and understanding of two strokes might come along and correct me without quoting from the internet about four strokes

[johnny650]

its clearly a complex subject ,I don't think any of us is likely to have any real personal evidence one way or another. You'd need a sophisticated testing facility to measure minute compression losses.

The point I was making was that I cannot see any evidence for 'massive' compression and performance losses through ring gaps no matter how over-sized they might be .

If you find an authenticated reference one way or the other perhaps you'd post it as it is a hotly debated subject with little or no actual evidence or proof .

[firekdp]

That testing was done with new rings, of the same size, with altered ring gaps. So only measuring the affect of the ring gap itself. The sealing pressure of the ring itself would be identical.
However, we are only measuring the ring gap to determine wear, if the ring gap has got significantly bigger since a rebuild, that is only down to ring or bore wear, so sealing pressure/compression will be diminished.