flyrotary@lancaironline.net Mailing List Archive

Andrew,

If an oil pressure gauge is installed at the inlet to the oil cooler, a pressure rise with increasing RPM will be observed. If the pressure keeps rising as RPM is increased to maximum, all the oil is passing through the oil cooler. If the pressure levels off at about 156 psi before max RPM is reached, then some oil is being returned to the sump by the front cover oil pressure relief valve and not passing through the oil cooler.

If an appropriate oil cooler is used, there would be no need for a second oil heat exchanger with associated plumbing, ducts, or controls.

On my test stand, at 6000 RPM, 143 HP, and 30" MAP, a total of 7700 BTU of heat was dissipated by coolant and oil. 16% of that was dissipated through the oil. This is for 15 gal/min oil flow and 53 gal/min coolant flow. I have more confidence in the oil flow rate value than the coolant flow rate value.

Steve Boese

From: Rotary motors in aircraft <flyrotary@lancaironline.net> on behalf of Andrew Martin <flyrotary@lancaironline.net>
Sent: Thursday, August 17, 2017 8:15:19 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: oil flow

Thanks Steve

My oil cooler is stock 20b, never seen a 13b oil cooler so can't really compare. but I'd guess mazda would use same brand.

To verify if the cooler is restrictive, wouldn't a oil pressure drop be noticeable once the thermostat closed? with the sensor after cooler on filter pad. I cant say I've noticed it, but will look closer next run.

I've been reluctant to change the oil cooler up to now, as none of the suppliers seem to be able to offer flow curves so finding it a bit hard to compare.

I'll see if I can borrow a hydraulic test set from a shop here. If I place it at the oil out port and get pressure and flow there I'll have a much better picture of what's happening now that I got your pump flows.

Lynn, from your explanation, seems to confirm my gut feel that I need to have that external OCV, to cool all the oil being pumped. but maybe I could use a oil to coolant exchanger to even up the system capacities.

Cheers Andrew