In a message dated 10/23/2002 7:49:34 PM Eastern Daylight Time,
marv@lancaironline.net writes:

> >I just cannot keep my mouth shut about this. All of the coolant going
> through
>  my race engines, (about 245 HP at 9,400 RPM) must pass through a 5/8"
>  restrictor.<<<
>  
>  Interesting Lynn.  Do you know what the average sustained HP at speed is;
> and
>  what the flow rate around the loop is?
>  I assume the restriction is to increase the pressure in the block.  With
the
>
>  restriction at the pump outlet, the full flow is circulating within the
>  engine; right? - or is the bypass blocked off?
>  
>  Al


> The driver is supposed to keep the revs between 8,000 and 9,400 all of the
time. The dyno sheet says that should be 230HP to 245 HP. I have a VHS-C
camera watching the gages in every session, and some times I catch him
dropping below 8,000 RPM and sometimes the rev limiter (9,500RPM) is telling
him to shift it.
    The bypass is blocked, and an American style thermostat with two 1/4"
holes in the rim was used (when it is cold enough). The thermostat
restriction is less than that caused by the out let 5/8" hole. It turns out
that the two 1/4" holes in the thermostat is too much area. When the temp is
low outside, the thermostat will not open, and all of the coolant is going
through the two 1/4" holes. We did this the first time, and the race coolant
temp would not go above 150 degrees. Since then just one 3/16" hole is used
and that seems to make the thermostat cycle a bit and the 180 degree
thermostat holds 160 degrees. Cooling on a cold day with a big aluminum
radiator is not much of a challenge. Most of the summer we race at 80 to 95
degrees OAT. A bit more of a test. We do not have cooling problems on the
water side. For good power, 160 to 180 is just fine. The oil has been more
like 190 to 200. That is not at all a problem as far as reliability is
concerned. In fact, years ago when we didn't know any better, we ran up to
240 degrees. We were not making much power back then so the rotor bearings
didn't notice our folly. It is a problem from the power point of view. any
oil temp above 160 is costing a little bit of power. The cooler the chamber,
the more fuel/air will fit in it. The engine builder told me that, and it
sounds right to me. We run 40wt synthetic Redline racing oil. We have lost
only two rotor bearings in the last 5 years. The engine builder said that it
was a run of "bad" bearings after Mazda changed suppliers (for a while).
Everything is back to normal now and no more problems since then. This while
by any measure, abusing the engines in the extreme. The shifts are at 9,300
RPM and the races are 45 minutes or 45 miles depending on the weather. The
problem with oil temps is that the oil is cooling the bearings, and if they
get too hot they loose some strength. The oil is also being used to cool the
rotor, and the bearing spill and the coolant oil mix and cover the actual oil
temp from the bearings. The only answer would be to make a short dyno pass
with the squirt holes plugged to see the bearing oil temp alone. Until then,
we just keep after that oil temp, and should have no problems. In the
airplane engine at around 6,000RPM or so the rotor bearings are at their
lightest stress levels. So all of this verbiage is far less important.

Lynn E. Hanover