In a message dated 9/6/2007 8:17:23 A.M. Pacific Daylight Time,
rolindsay@yahoo.com writes:
My Italian car idles at 60psi and operates anything
off idle at 90psi! It also has a fire pump for an oil
pump using a dry sump design with twin scavenger pumps
running in the sump. The actual lines to/from the
high pressure pump and oil cooler are steel jacketed
lines about 1-3/8" OD. Lubrication and bearing
cooling are serious concerns as these 3.0 liter V8
engines can run at 7700rpm red-line all day long - and
do!
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Only 7700? :-) Mine redlines at 7900....(I don't normally run my MGA above
7700 though!)
There are two issues here. One is 'washing' the bearings. That is old hat
thought and bearings should have no problem with high pressure given adequate
clearance. Some reason the Italian cars use high pressure - my Lambo is
supposed to run to 7 Bar - and do not have problems with that.
The other is mechanical wear. If you put the sort of drag through the MG oil
pump that this sort of pressure entails, especially on race cars where you
are running high RPM, you WILL wear the gears out in no time. Stronger gears
are one solution, but the best thing to do is abandon the old 'rule' of 10 psi
per 1000 RPM developed with American V8s and concentrate on volume, not
pressure.
60-70 psi will serve for just about anything.
It is too bad we can't go to dry sump with external pumps just as it is too
bad we have to screw around with distributors and can't use crank fired
ignition and coil packs and toss the old distributor in the trash can, but for
racing at least, they are a no-no.
BTW, the reason the Italian engines don't have mechanical problems with oil
pump drive is that usually they are crank driven through hefty gears....
Bill
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