REFLECTOR: Fuel Consumption Performance
Brian Michalk
michalk at awpi.com
Wed Aug 5 10:52:06 CDT 2009
Thanks for mentioning this, Scott. The OP raised that concern, and I
had not yet time enough to counter with the danger.
Scott Derrick wrote:
> Terry,
>
> running the first cylinder LOP can put some of the richer cylinders
> right in the BAD zone. Thats well... bad! Thats why you always lean to
> the last cylinder when running LOP. Thats also why you lean to the
> first cylinder when running ROP, so all the other cylinders are rich of
> that point.
>
> you said
>
> "I was afraid my coolest cyl could be 150 LOP before the last cly peaked and that I could burn that exhaust valve."
>
>
> Thats exactly backwards. Once a cylinder reaches peak EGT and goes on
> the LOP side it will run cooler and cooler the leaner you run it. The
> absoluter worst mixture is about 25-50 degrees ROP in terms of
> detonation and the timing of peak power pulses. If your coolest
> cylinder was running at 150 degrees leaner than the last cylinder to
> reach 75 LOP it would probably not be firing due to the too lean mixture.
>
> How to operate your engine is a complex topic. Here is a great set of
> articles by John Deacon, I consider a must for any recip operator,
> whether you run LOP or ROP.
>
> part 1
> http://www.avweb.com/news/pelican/182179-1.html
> part 2
> http://www.avweb.com/news/pelican/182176-1.html
> part 3
> http://www.avweb.com/news/pelican/182583-1.html
> part 4
> http://www.avweb.com/news/pelican/183094-1.html
>
>
> Here's GAMI's lean test, a great thing for anybody to do, to see how
> balanced their injectors are.
>
> http://www.gami.com/gamijectors/leantest.php
>
> Scott
>
>
>
> Terry Miles wrote:
>
>> Scott,
>> No I didn't know that. Thanks. Remember I am the rookie with no recip
>> time. I was afraid my coolest cyl could be 150 LOP before the last cly
>> peaked and that I could burn that exhaust valve. As it is, some cyl never
>> get to peak. That's why the fast TAS probably, and I could get the FF below
>> 11 when I was up over 10,000 and only loose a few knots.
>> Thanks
>> Terry
>>
>> -----Original Message-----
>> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org] On
>> Behalf Of Scott Derrick
>> Sent: Tuesday, August 04, 2009 08:05
>> To: Velocity Aircraft Owners and Builders list
>> Subject: Re: REFLECTOR: Fuel Consumption Performance
>>
>> Terry,
>>
>> You probably already know this.
>>
>> at that altitude you could run any mixture without fear of detonation,
>> however that is not how LOP operation is usually done.
>>
>> For LOP you always lean to the last cylinder, not the first as you do for
>> ROP.
>>
>> GAMI, recommends 75 LOP as the richest mixture now. Especially in a full
>> power climb.
>>
>> nice numbers...
>>
>> Scott
>>
>> Terry Miles wrote:
>>
>>
>>> Tom,
>>> I've got an XLRG-5 IO-540K 300 HP with a 3-blade constant speed ACI prop.
>>> These numbers are about 2 weeks old. Same day taken only an hour or so
>>> apart on the xc from PA to IN.
>>>
>>> Altitude 10000 12000
>>> OAT C +16 +12
>>> TAS 193 195
>>> IAS 160 157
>>> FF 11.5 11.5
>>> RPM 2330 2390
>>> % pwr 64 62 wide open throttle
>>> Oil T 192
>>> Oil P 66
>>> Cyl ave 300 25 hotter
>>> EGT 1230 same
>>>
>>> I lean until my first cyl is 50 lop and quit there. I can likely go
>>> to 11 gal.
>>> I was about 2600 gross wgt at the time.
>>>
>>> Terry Miles
>>>
>>> -----Original Message-----
>>> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]
>>> On Behalf Of Tom Tolton
>>> Sent: Monday, August 03, 2009 19:39
>>> To: 'Velocity Aircraft Owners and Builders list'
>>> Subject: Re: REFLECTOR: Fuel Consumption Performance
>>>
>>> Thanks Brian. I'll start looking for BSFC numbers. After posting my
>>> last message I found an article where a LANCAIR with a 550N was tested
>>> to determine the Vbc or velocity for best CAFÉ or best Comparative
>>> Aircraft Flight Efficiency. At 12.5 K density altitude 2300 rpm and
>>> 248.3 smph they were able to reduce fuel consumption to 10.4 gph LOP.
>>> Do you know if Velocity has entered the CAFÉ competition?
>>>
>>> -----Original Message-----
>>> From: reflector-bounces at tvbf.org [mailto:reflector-bounces at tvbf.org]
>>> On Behalf Of Brian Michalk
>>> Sent: Monday, August 03, 2009 8:16 PM
>>> To: Velocity Aircraft Owners and Builders list
>>> Subject: Re: REFLECTOR: Fuel Consumption Performance
>>>
>>> You want the BSFC number. Brake Specific Fuel Consumption. The
>>> smaller the number, the better.
>>>
>>> Typically, the following lower the BSFC:
>>> large displacement
>>> high compression ratio
>>> low RPM
>>>
>>> Tom Tolton wrote:
>>>
>>>
>>>
>>>> I recently traveled to Oshkosh with a friend who owns a Velocity 173
>>>> with fixed gear and a 200 HP fuel injected Lycoming. He was able to
>>>> reduce gas consumption to 6.2 gallons per hour at 10500 feet and
>>>> maintain a speed of about 125 nm/hr using LOP techniques.
>>>>
>>>>
>>>>
>>>> I am building a XLFG -5 with constant speed propeller. I am looking
>>>> for what one might expect in minimum gas consumption using LOP
>>>> techniques at a density altitude of 10000 feet. I am considering
>>>> the Lycoming IO540 260 and 300 HP, as well as, the 310 HP Continental
>>>> 550N. It has been suggested that if I buy one of the more powerful
>>>> 300 HP engines I will just be able to run with less throttle and
>>>> bring the fuel consumption to a reasonable level.
>>>>
>>>>
>>>>
>>>> I would appreciate any comments / experience of the builders and owners
>>>> with a similar XLFG configuration.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> Tom Tolton
>>>>
>>>> 989-835-5828 (Home)
>>>>
>>>> 989-750-8567 (Cell)
>>>>
>>>>
>>>>
>>>>
>>>> ---------------------------------------------------------------------
>>>> -
>>>> --
>>>>
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>>>>
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>>
>
>
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