What we should expect from the next patched Blenheim engine model

[phoenix1963]

I quite enjoy struggling with the current over severe engine model, but here are some pointers for the devs:

Improved cooling: The manual clearly states that takeoff is to be performed with closed radiator flaps (gills), this suggests to me that CHT (cylinder head temperatures) should not exceed 240C for a starting temperature of 180C (not currently achievable with closed gills). Likewise, level flight should be able to be performed at cruise settings with fully closed radiator flaps at all altitudes.

Similarly, I suggest that typical taxiing power (say, -1lb?) should be able to be used indefinitely on the ground (i.e. near zero airspeed) with open radiator flaps. Also, climbing at 5lb boost and 130 mph with open flaps should give stable CHT.

This gives the devs useful boundary conditions for the amount of waste heat that is successfully transferred out of the engine at a variety of engine settings, airspeeds and the two extremes of radiator flap settings. The current model (particularly with closed gills) simply does not reflect the reality of the record.

Improved boost: The manual clearly states that +9lb boost can be used for takeoff until 120 mph is reached. The current engine model is too fragile for this.

Oil temperature: Using the (inauthentic) intermediate pitch settings, it often seems difficult to select throttle settings for level flight that allow both the CHT and oil temperatures to remain within normal limits (even using the radiator flaps to adjust). The problem goes away when coarse pitch is selected (indicating a programming "fix" to the problem). Surely this is not authentic and the oil temperature (or engine sensitivity to it) must have been less of a problem?

Flaps: We must be able to select intermediate settings.

Respectfully submitted,

56RAF_phoenix

[Sutts]

Realistic coolant and oil temp is a subject close to my heart. I'm hoping for big improvements in this area as the sim progresses.

The Spit suffers from similar problems. The real manual states:

"The radiator flap regulates the flow of air through the radiator, but cannot be fully closed"

"The radiator flap can usually be kept in the closed position during cruising flight"

"ACTIONS AFTER TAKE-OFF: Close the radiator shutter (unless a high power climb is done, when the lever should be a little forward)"

Closing the radiator flap like this is a bit of a no-no at the moment as the temps surge. I wonder if the flap in CloD is modelled as fully closed whereas as stated above this was physically impossible in reality? Could be the same problem with the Blenheim cowl flaps?

For the full CEM experience I think we need the following factors to be considered:

altitude (colder air at altitude = cooler)
airspeed (more air through radiator = cooler)
radiator obstructions (like lowered landing gear leg on spit)
mixture (richer mixture = cooler)
boost (lower boost = cooler)
rpm (lower rpm = cooler) WE HAVE THIS ONE

[robtek]

Oil temperature influencing oil pressure

Warming up the engine was related to the oil pressure, i.e. the DB601 should be warmed up not exceeding 6kg/cm oil pressure, no limit on the rpm's

[NZtyphoon]

The cylinder heads of the Bristol Mercury had to be kept within a range of 190-210 degrees centigrade; too cool and the engine would not respond properly to throttle movements, while too hot would promote detonation in the cylinders: oil temp between 70-80 degrees, with a pressure of 80 psi. Take off procedure in real Blenheims:

Carburettor Air intake Control to "Cold" or "Hot" depending on ambient temperature:

Mixture controls to "Normal":

Prop Pitch to "Fine":

Engine cooling gills to fully open during taxying, but wound closed immediately before take-off, otherwise the drag of the gills could make the take-off run excessively long:

Raise undercarriage immediately after the wheels leave the ground to reduce drag.

The Bristol Mercury XVs of Blenheim IVs were cleared to use 100 Octane fuel and the practice was to fill the outer fuel tanks with this grade, using it for take-off with extra boost; the inner wing tanks were filled using 87 octane.
(Graham Warner, The Bristol Blenheim: A Complete History, 2005, pages 96-97, 99-100.)