michaelmount123

Actually, the squirters don't operate at idle. They're equipped with a pressure valve (ball and spring) that only allows them to open with increased oil pressure. Clearly they're not needed at idle, and the closed valve keeps idle OP up. The oil stream from the squirter is directed at the underside of the piston, carefully positioned to cool the piston crown at any position in the bore.

Normal oil splash from the crank/rods is inconsistent and ineffective as a cooling method. Further, an effective crank wiper (Porsche's is part of the pan) minimizes the splash, and a dry sump further reduces splash.

Interesting to note that the 997 Cup engine has gone from one squirter per cylinder to two. Same with the 997 turbo.

michaelmount123

4V I hope!

Voith

Its interesting that 951 came without squirters even though many cars of the era came with them. Porsches included..

blade7

You would expect Porsche to be best placed to make those decisions...

ptuomov

968 has those early box style skirt pistons, a little like the original Evotec. Where does the oil spray hit the piston at BDC in stock 968?

Do you need to change the oil spray angle in 968 when stroking it and using the latest box-strut piston design?

michaelmount123

The 968 piston cooling oil spray travels across the underside of the piston as it travels from TDC to BDC. There's no need to change installation angle with a different stroke or piston design. I use an old 968 block on the mill to set up angles and placement, then swap out to the block being drilled.

MM

ptuomov

thanks.

Julian Allen

Nice to see you posting, Michael!

LUCKY DAVE

As most of you probably know, the champions of HP/displacement are performance motorcycle engines.
They all have piston squirters.

ptuomov

You don't have to convince me. Any engine that has thin piston rings needs piston oil squirters, and most race engines require thing piston rings (or can at least benefit from them).

Some articles of how race engines use piston oil squirters:
http://www.f1-forecast.com/pdf/F1-Fi...F1-SP2_08e.pdf
http://www.engineprofessional.com/EP...437f8f93e3.pdf

Voith

951 engines were designed to very succesfully run without em.

blade7

My last couple of litre bikes have doubled the rev limit of my 944. Hardly relevant.

ptuomov

I think that the stock 951 engine will run very well without squirters, but if anyone is looking to materially increase the rpms or the stroke of the engine, then one may want to change some things. First, one needs thinner rings to prevent ring flutter. Second, one needs a lighter piston to keep the conrod (and what's attached to each end) happy. These two changes together mean that the piston can't handle or shed as much heat as before, while the heat put into the piston increases with more power. By my logic, that heat needs to be pulled from the piston and the easiest way to do that is with a piston oil cooling jet.

By my understanding, F1 with almost 100mm bore and 2mm thinnest spot on the crown needed 19 or so spray jets aimed exactly right per cylinder from two nozzle systems to prevent piston cracking. This is not what I expect our cars to need, I am thinking that an oil spray jet anywhere on the piston will be helpful.

blade7

Porsche did all that on the 968, how much higher did it rev? If MM was close to me I'd have the squirters fitted, but I won't lose any sleep over not having them.

Voith

I had a chance to look in to dissasembled bmw megatron 1.5L 4cyl 1500hp engine and didn't see no squirters. Maybe I missed them if they are really hidden, but I've specifically look for them.

Hows that for hp/displacement championship?