Quote:
Originally Posted by verbeekb
The thing is, if these notches were deemed necessary by both Porsche and VW in wet sump conditions, then, what kind of piston cooling/wrist pin lubrication do we end up with in a dry sumped type 4? I think that captures it better.
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Hi Brian,
No, it was clear to me before you weren't referring to the placement of the notches
I think we're getting somewhere here tho: I think that you think that the wet sump is partly responsable for lubrication of the cylinders right?
Sorry, but that is really not the case imho (think for instance windage tray in 914 2,0 application). Its the escaping oil between the rods and crank flanges that takes care of it. That's also why the rod sideplay is so important. Too much sideplay there costs oil pressure to paint the picture of what happens there.
To capture the jist of it: your wet sump does NOT lubricate the internal engine parts! Don't worry about it one second.
The rod notching was also only advised late in the seventies when there were only those really heavy brick-type T3 Vanagon busses on the market. Before there obviously never was a problem...
Those T3 transporters were so heavily abused combined with high weight and poor Cw that the engine/oil and thus also the pistons got so hot, they expanded too much and caused seizing (cheap cast pistons) in more than one occasion. Extra oil cooling was to prevent this. So, its not about lubrication, but only about cooling!! The final solution of VW was better cooling by introducing watercooling (wbx) soon after...
That is my reasoning behind the factory-advised notching thing.
I have actually never notched 2,0 liter rods in any 2 liter engine I build and I have done many many miles with them and all had way more than the factory 70 hp. Last one had twice the hp...and no ill effects of the alleged 'neccessary' notching. Most of them, I have done many miles and again, never any oiling issues of seizing of pistons... but I have always had good cooling not driving a T3 at 100 mph on the freeway also helps
Like I wrote before: I think its a 'non-issue' all together in anything else than a stock T3, but you had to let me write it all down again huh
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Now, if I would ever build a turbo type 4 on a 2 liter basis, the extra piston cooling might be very welcome since turbo's make pistons very, very hot and lean conditions are possible very easy and very fast. So I want to try this piston notching someday to see what it does or not do, but I don't worry one bit that I don't have it for now
Greets,
Walter