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Text and photos graciously contributed by Jeff Jenkins, with research by Mike Roznovsky. Edited (with additional comments) by Gustave Stroes: |
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Gustave: What are oil squirters? What do they do? Oil squirters can be found on many newer production cars, as well as on most purpose built racecars. They are located on the block, near the crank, and they squirt a jet of oil onto the underside of each piston. The oil can be supplied to the squirters in several ways. On the Evolution III (Sport Evo) 2.5L S14 engine the squirters were supplied oil right from the main galley running alongside the block, just above the crank. The purpose of the oil squirters is to cool the aluminum pistons. There are two reasons for this. First of all, the strength of aluminum decreases rather quickly as the temperature is elevated. With the emphasis on decreasing the mass of pistons (a reciprocating part) the amount of material is reduced to the absolute minimum, so the margin on strength is not large. Any further decrease in strength due to heating should be avoided to maintain the mechanical integrity of the piston. There is also evidence that cooling the pistons can reduce the likelihood of pre-ignition (and possibly detonation). This can be caused by hot spots (on sharp edges of the piston-top) lighting-off the mixture before the spark plug fires. Rounding off any sharp edges on the machined piston-top can also help prevent this. |
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Jeff: All of the squirters except for the 618 part are intended to be mounted on the block next to each cylinder bore. This means that they are tapped directly off of the main oil galley. The 907 and 217 parts point the squirter nozzle directly upward. The Evo3 and Wiseco squirters have an angled nozzle. I suspect the angle is due to the offset placement required to clear the rods on 87mm cranks. The Wiseco squirter (used on DTM motors) has a different bend than the Evo3 (You can see it in the pics). This might be due to more clearance of the shorter DTM piston skirts, or possibly a different spray angle better suited for the race pistons. I don't have the part number for the Wiseco squirters but I know there is at least 1 other similar Motorsport squirter. What is interesting is the Motorsport squirters are cheaper than the Evo3 ones.. |
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Jeff: Those that I have talked to tell me that the clearance between the rod big ends and the Evo3 oil squirter are VERY tight. In fact, if the low-profile bolts are not used the rods will make contact. This clearance issue is the primary concern I have with implementing these other squirters in the same fashion as the Evo3 squirters. In one of my pictures you can see a profile view of each squirter. They are all similar in thickness, but the Evo and Wiseco squirters have a depressed area where the rods pass over for more clearance. You can always shift the squirter closer towards the main bearing webbing, but then you can have issues clearing the crank counterweights. One potentially beneficial feature of the 907 and 217 parts are their longer squirter arms. This might make placement further away from the bore possible, which might allow for enough clearance. Its all really speculation though until you can actually test this stuff out first hand… |