I suspect that you temp sensor location may be the problem rather than calibration.  If its outside the main flow channel, then its hard to tell just how close or far off of the main flow temps it may be registering.  

 

On the other hand if your coolant engine outlet temp is measuring only 161F (and assuming that is somewhere near the actual temp) then you radiator is clearly doing its job by cooling down the coolant before it enters the engine.  When I am cruising at 5400 rpm my coolant temps range from 155F-175F depending on OAT.  This is temp out of the engine.  Since your temp is in the same ball park, it appears your radiator is doing a good job especially given the 90F OAT. 

 

 

 

Ed

----- Original Message -----

From: Mark Steitle

To: Rotary motors in aircraft

Sent: Saturday, September 29, 2007 10:13 PM

Subject: [FlyRotary] Re: Oil Delta - T

 

Ed,

OK, I'll recallibrate the sensors ONE MORE TIME!  They were reading within a degree of each other before I relocated one of them.  I did take the time to verify the EC-2 sensor was reading correctly at 212* during the switch.  But I didn't check it lower than that.  I'll use ambient temp for a low reference. 

 

I suspect the problem may be where one of the sensors is located.  The first sensor is located on the WP housing at the outlet from the engine.  Since that is one of the factory locations, I don't see any problem there.  The second sensor is on the WP housing inlet, but not on the main line, it is on the one returing from the swirl tank, but is very close to where the main WP inlet is located.  It is fed by a line that runs through the swirl tank from the outlet side of the radiator, but at the top instead of the bottom (to draw any air out of the radiator).  Directly across from this fitting is the "hot" inlet to the radiator.  I'm sure that some of the coolant goes straight across the core to the swirl tank fitting. (Yes, this is confusing me too)  I questioned the wisdom of putting the sensor where I did, but did it anyway due to the ease of installation (No draining the cooling system, no drilling, no tapping).  Anyway, this was supposed to be a "temporary" test setup. 

 

So, it looks like I probably need to find a better place to locate the second sensor.  I'll check the accuracy of this sensor at around 150* and see what it shows.  If there is a significant error, I'll dive into the EC-2 calibration system one more time (heaven help me).   

 

Mark 

 

On 9/29/07, Ed Anderson <eanderson@carolina.rr.com > wrote:

  Mark, if you really had excess air flowing through your radiators the coolant would drop more than 4 Deg F.  In fact, the more air flow the more coolant Delta T you would drop through the radiator.  So if you had something like 180F in and 120F out then I might suspect too much air flow through the cores, but not with a drop of only 4 deg F.   In fact if that delta T is correct (which I suspect it is not), then you would need tremendous coolant flow rates for it to carry away the engine heat it needs to at 5200 rpm.

 

 I did some back of envelope calculations. 

 

 IF your coolant flow was 30 GPM at 8.25 lb/gal coolant with a 0.65 (50/50 mix) Cp, then a 4 degreeF drop in coolant temp would only be getting rid of 644 BTU/Min. 

 

 At 5200 rpm and a 19:1 A/F ratio you would need to get rid of approx 3100 BTU/Min through your radiator.  I suspect that the 4 degree  drop you are measuring may be in error.  I assume you are measuring temp at radiator inlet (engine outlet) and radiator outlet (or engine inlet)   It would take something like a 20 deg coolant temp  drop at 30 GPM flow or a flow rate of 150 GPM at 4 deg drop to get rid of that much heat.  

 

On the other hand if you were flowing 60 gpm of pure water and had a 6.5F drop that would get rid of the required BTUs.  I have no clue as to the flow rate of a 20B water pump, but suspect my guess of 60 gpm might be on the high side.

 

Since you are apparently cooling just fine with the radiators, then :

 

1.  My calculations are incorrect

2.  Your coolant temp drop is more than 4 Fdeg

3.  your flow rate is >50 gpm

4.  You oil system is dumping the excess heat that your radiators are not getting rid of.

 

FWIW

 

Ed

 

 

----- Original Message -----

From: Mark Steitle

To: Rotary motors in aircraft

Sent: Saturday, September 29, 2007 7:51 PM

Subject: [FlyRotary] Re: Oil Delta - T

 

Tracy,

 

I flew again today.  I'm still staying very close to the airport and was forced to limit my altitude to 2500' due to clouds.  OAT was about 90* and oil got to 215, but came right down after leveling off and settled in at 190*.  The strange thing is the water temps in economy cruise (5200 engine rpm, 1800 prop rpm) were in the 157* range.  I'm measuring water temp in and out.  Water out was about 161*, so I'm getting very little temp drop through the radiator.  We're figuring that this is probably due to too much air to the water radiator or too rapid coolant flow through the radiator (I'm running the 20B pump).  My main pulley has been downsized, but I may also need to enlarge the wp pulley a little to slow the flow.  I'm considering doing a quick mod to check this theory.  If that's true, then my oil temps should drop because I suspect airflow through the two radiators are fighting for the exit space and the water radiator is winning. 

 

Mark

 

On 9/29/07, Tracy Crook <tracy@rotaryaviation.com > wrote:

Haven't had any 100+ days since installing the Renesis but cooling is similar to the 2nd gen I had a few years ago when we had 10 consecutive days of 100+ temps.  Didn't have to wait it out but simply limited power after initial climbout.  Still had more ROC than most certified planes at the reduced power setting.  I start with around 2500 FPM on a standard day and never had to settle for less than ~1000 fpm due to heat issues.

 

Hope my 20B RV-8 does as well or better but I will install spray bar for initial tests.

 

Tracy (delayed 20B test schedule due to motorcycle distraction)

 

On 9/27/07, Mark Steitle <msteitle@gmail.com > wrote:

Tracy,

 

So, what do you call a "hot" day?  In Austin, it is normal during the summer for temps to be in the upper 90's and even above 100 on occasion.  I don't want to be grounded waiting for the Texas heat to subside.  I guess I could install a spray bar for summer flying.  Right now I can keep temps in the green up into the low 90's.  Living in Texas, I would like a little more margin than that.  Not everyone can swing a summer home in Colorado.   ;-)

 

Mark S.

(Just happy to be flying again.)

 

 

On 9/26/07, Tracy Crook <tracy@rotaryaviation.com > wrote:

Engine will cool at any throttle setting that enables the plane to fly.  The coolant & oil temp curve looks about like the power required curve of the airframe, minumum at around 95 mph and rises on either side of that speed.  Only exception is WOT at Vx on hot day.  Engine will exceed redline temps if this is maintained more than a minute or so.   Fortunately there is never any real need to do that. 

 

Tracy

 

On 9/26/07, Mark Steitle <msteitle@gmail.com > wrote:

Tracy,

 

Is there a particular speed that you must reach before your system cools? 

 

Mark

 

On 9/26/07, Tracy Crook <tracy@rotaryaviation.com > wrote:

For another data point, the delta T on oil cooler depends on power setting on my installation (no big surprise).  It is around 40 degrees F at higher power settings.

 

Tracy

 

On 9/18/07, Mark Steitle <msteitle@gmail.com > wrote:

For those that are flying (rotaries), I'm curious as to what delta-T you're seeing across the oil cooler.  And at what speed you attain adequate cooling.

 

Mark S.