REFLECTOR: Best Speed for MPG

[Brian Michalk]

My engine came with engine stand test data, as well as charts applicable 
to the model.  They graphed out BSFC for wide open throttle with RPM and 
manifold pressure on the two axes.  You need to look up that sweet spot 
for the lowest BSFC and choose that as your target.

Next, find the airspeed for your airframe that is the most efficient.  
However, this is probably a really low speed.  Maybe 110 knots or so?  I 
think it's the best glide speed?  The problem is that going WOT at that 
low airspeed probably won't give you max miles per gallon.  Gallons per 
hour isn't correct either.

I haven't Googled, but there is probably a documented procedure to 
determine the parameters for most efficient.


On 8/14/2013 8:52 AM, Ron N VelocityXLFG wrote:
> I have read  that some where also and the argument makes sense that 
> the engine is nothing more than a air
> pump. So you do not want to restrict it. Though it seems there should 
> also be a sweet spot where the
> aerodynamic is more important that the throttle position.
>
> On 8/14/2013 7:59 AM, Brian Michalk wrote:
>> The engine runs most efficiently at wide open throttle and low RPM.
>>
>> If you can regulate power with altitude, fly high at WOT.
>>
>> On 08/14/2013 07:51 AM, Ron N VelocityXLFG wrote:
>>> I was wondering what the best speed per gallon of gas  has been in 
>>> the velocity.
>>> I have been doing some  work on this lately . Now my plane having a 
>>> alternative
>>> motor and a fixed pitch prop will likely not be the same as other 
>>> installations but
>>> with that said I still would like to know what Speed other velocity 
>>> pilots are
>>> finding for the best fuel mileage  has been.  I feel most 
>>> comfortable at 145 knots
>>> seems to be the sweet spot for me so far but that is also my comfort 
>>> zone for the engine
>>> rpm on my fixed pitch propeller. Now this is only about Half 
>>> throttle for me wide
>>> open I get 175 knots Or should I say 201 MPH  but I am sure my 
>>> mileage will go way down at the speed.
>>>
>>>
>>> So far for me with only a few cross country's under my belt
>>> Velocity XLFG LT1
>>> Prop RPM 2500 Prop tip speed 535 mph
>>> Prop Dia 72"
>>> At 4500 alt
>>> 2600 gross Weight
>>> Speed of 143 knots
>>> 280 mile round  trip
>>>
>>> I got 12 gallons an hour
>>> fuel burn
>>>
>>> Ron
>>> _______________________________________________
>>> To change your email address, visit 
>>> http://www.tvbf.org/mailman/listinfo/reflector
>>>
>>> Visit the gallery!  www.tvbf.org/gallery
>>> user:pw = tvbf:jamaicangoose
>>> Check new archives: www.tvbf.org/pipermail
>>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>>
>> _______________________________________________
>> To change your email address, visit 
>> http://www.tvbf.org/mailman/listinfo/reflector
>>
>> Visit the gallery!  www.tvbf.org/gallery
>> user:pw = tvbf:jamaicangoose
>> Check new archives: www.tvbf.org/pipermail
>> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
>
> _______________________________________________
> To change your email address, visit 
> http://www.tvbf.org/mailman/listinfo/reflector
>
> Visit the gallery!  www.tvbf.org/gallery
> user:pw = tvbf:jamaicangoose
> Check new archives: www.tvbf.org/pipermail
> Check old archives: http://www.tvbf.org/archives/velocity/maillist.html