Useful Cylinder Info

[bugguy1967]

I was lucky enough to have Anders Roman from Sweden visit me here in LA while he is vacationing in California. He has learned a wealth of knowledge from Johannes Persson of JPM fame, and he shared some of his knowledge with me. For anyone that doesn't know of Anders, he was #2 and #3 on Cal-Look.com's fastest cars for two years. He is currently shooting for the Pro Stock record.

I learned that when you torque down cylinders into the block, the cylinders deform into a shape resembling a four-leafed clover (exaggerated of course). The thinner areas nearest the studs move inward at full torque. JPM rehones all barrels in a torque plate to get them as round as possible. Of course, a torque plate cannot completely mimick a cylinder in its' spigot, but it's the best solution. I knew that torqued cylinders deformed under torque, but not to the extent that was explained to me.

Johannes states that this is the reason why fresh engines run hotter for the first few thousand miles. Furthermore, if you have a perfectly, or almost perfectly round bore, you can run lower tension rings on the street without ill effects (free horsepower). Higher tension rings, like the standard rings that come with pistons form better to untrue bores, at the expense of more friction. Low tension rings can't conform as easily.

I asked Anders at the conclusion of our meeting, "What are your tips for making horsepower"? His reply was, "Reduce Friction, wherever possible".

Something to think about. We all just basically bolt our cylinders on, without an afterthought. Regardless of our application, all builders can benefit from this.

[raygreenwood]

Totally agree. While I thank you for this.... I actually thought this was fairly widely known.

Many hours of conversations about this years ago on the STF and a few other places
Bear in mind I work almost strictly in type 4.....but in the last 20 years I cannot remember the last time I just "bolted on" a set of cylinders. Type 4 is a little less disposible than type 1 and parts do not grow on trees. Every new set of cylinders spends time with the dial bore gauge.....torqued down with a torque plate.

At least half need a very quick and short hone just to clean up ....if nothing else just to clean off the minor rust that collects on NOS cylinders sets. Other times to get just right piston drag and skirt to bore clearance. A torque plate is always used and the work is done on the actual case.

In the few times I have actually had cylinders bored oversize at a machine shop....a torque plate is always used....and I usually have to provide it.

But great information! Ray

[Type 5 Joe]

What torque is the question?

[modok]

When there is significant torque distortion i commonly visually see uneven wear near the top of the ring travel, but I do not see any of that on VW cylinders.
I do see some distortion from the piston thrust especially on longer strokes.

It's not impossible to test yourself. Bolt the cylinders and head on one side of the case and stick the bore gauge in through the case end.

[Type 5 Joe]

You would have to do torque readings on a hot engine that is up to normal operating temp....

Then attempt to reproduce that. When I did this it was quite a difference between short / long studs.

Even that wouldn't reproduce the effect heat had on the cylinder in use.

[modok]

Right, to get a real good measurement you have to measure on a hot engine while running WOT. which means.....look at the wear marks! how else would you?


DON'T overlook..... MOST of the reduced friction is from using special rings, which require much better and more particular honing.

There will be minimal benefit in fancy honing using old fashioned iron D-wall rings. You can make them seat faster and last longer but that's about it.

[modok]

Oh, and i;m sot saying that isn't a real thing, your right it IS, but I'm taking the other side to give some idea of when it matters more and less.

Friction goes up at the square of speed and VE may tend to drop, so the higher rpms you are running the far more critical the rings become.

[raygreenwood]

The biggest problem that started a lot of this among type 4 people....is the problem of getting cylinders that are straight in the first place.

Yes....a hot versus cold cylinder is night and day....but in the type 4 world we have been seeing the problem of distortion and taper to some extent even on cold cylinders. Its not that you can even correct it if its there.....but we check for it...or at least some of us do. It answers the question of should I even be using this set of cylinders or should ai look for a better aet.

When a better than factory ...even stock configuration engine....can suck up $5k in parts and machine work....you check everything to the best of your ability.

That's a great suggestikn Modok.....reverse measuring with the head on and I have done that numerous times.

In reality....a single cylinder torque plate....which is not as good as a two cylinder torque plate....but I can have made much cheaper.....only lasts for about 3-4 engine uses if its aluminum because the passage of the hone tends to wear the plate back from the cylinder sealing area. It gets bigger.
Ray

[Type 5 Joe]

Nearly impossible to reproduce actual running shape of the cylinder...

Everything would have to be equal. Of course that is the goal anyway.

Tune, mixture, fin placement... The effect of cooling air ramming the top vs the bottom of the cylinder.

Its like bores in a saimese cylinder cylinder V-8 (chev 400).... They seem to work.

Like you stated... They evidence is in the wear, marks, flat areas seen after wear has been put on it.

[Bad bug]

[UK Luke 72]

I read that 40% of the friction in an engine is caused by the ring tension. And 50% of that comes from the oil control.
Thus the use of <1mm compression rings... At the expense of durability.
_________________
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[Q-Dog]

All of this suggests to me we should stay away from those really thin wall cylinders. Anyone measure the deformation of thin wall versus standard wall versus thick wall cylinders when torqued?
_________________
Brian

'69 Dune Buggy
'69 Beetle Convertible
'70 Beetle

[bugguy1967]

[raygreenwood]

[mark tucker]

thats the reason we spent hundrads of$$ for each torqueplate for each diferent type .engine & sometimes diferent bore of the same engine took diferent plates too diferent engines deform the cylinders diferently as does different head bolts or studs. and the applied torque. even the main studs on many engines affect the cylinders. as does the type of head gasket.hone using the type of head gasket that will be used.and the head bolts/studs that will be used. one issue with vw cylinders is honing pressure, too much pressure on thin walls will also distort the bore. yes thinner rings will seal better as they will conform to the bore better. and less tension on them and use the proper gass porting too. it would be neet to know just how much the pressure from the studs is on a cool motor and a hot motor. the head grows, the cylinder grows,the studs grow...all at different rates so the applied pressure changes. thus some vw's without head gaskets leek when cold but they seal up quickley whit heat....well they might seal up.