Return-Path: Sender: (Marvin Kaye) To: lml Date: Wed, 11 Jun 2003 11:22:18 -0400 Message-ID: X-Original-Return-Path: Received: from [65.66.11.38] (HELO qbert.gami.com) by logan.com (CommuniGate Pro SMTP 4.1b7) with ESMTP id 2410927 for lml@lancaironline.net; Tue, 10 Jun 2003 23:29:40 -0400 Received: by QBERT with Internet Mail Service (5.5.2650.21) id ; Tue, 10 Jun 2003 22:40:19 -0500 X-Original-Message-ID: <52548863F8A5D411B530005004759A933920E2@QBERT> From: =?utf-8?B?R2VvcmdlIEJyYWx5?= X-Original-To: =?utf-8?B?J0xhbmNhaXIgTWFpbGluZyBMaXN0Jw==?= Subject: =?utf-8?B?UkU6IFtMTUxdIExPUCBGTE9QLCBST1AgRk9QIFF1ZXJ5IGZvciBH?= =?utf-8?B?dXJ1KHMpICA=?= X-Original-Date: Tue, 10 Jun 2003 22:40:16 -0500 MIME-Version: 1.0 X-Mailer: Internet Mail Service (5.5.2650.21) Content-Type: multipart/alternative; boundary="----_=_NextPart_001_01C32FCB.2D3095F2" This message is in MIME format. Since your mail reader does not understand this format, some or all of this message may not be legible. ------_=_NextPart_001_01C32FCB.2D3095F2 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable =20 >> =E2=80=9CProp efficiency goes down after 2500 rpm.=E2=80=9D Even = though Klaus runs rings around larger engined planes when he is operating in excess of 3000 = rpm? Does the efficiency go down, but thrust HP is increased? Am I losing = power by operating at 2660 rpm (a felt sweet spot)? << =20 Prop efficiency is a very complicated issue. Depends on a whole lot = of factors - - including RPM, HP, diameter, Mach number, air density.... advance ratio, and more. =20 You can get more thrust at the higher RPM because you make more = horsepower at the higher RPM. One can do this in spite of the lower prop = efficiency at the higher RPM. =20 =20 1. What is 75% power for my Lycoming I/O 320 engine equipped with a 70 inch Hartzell constant speed prop? I have made the following = adjustments: By definition, 75% power in the airplane world is any power = setting at which the engine produces torque at an RPM to generate a horsepower = that is 0.75 x the max rated horsepower. It has nothing to do wit your = prop - - whatever size it is. By the way, "percent power" numbers are largely over = emphasized in the minds of pilots.=20 >> Different pistons were used to raise the compression = ratio from 8.5 to 9:1. How was that done? Did it reduce my cubic inches or somehow increase the stroke? << No. The change in piston height to go from 8.5:1 to 9:1 is = very small. In fact, the "swept volume" remains the same. We are talking = about changes in piston height on the order of 20 or 30 thousandths of an = inch. >> A non-filtered induction ram air system is used which = raises the manifold pressure 1.5=E2=80=9D Hg at 180 KIAS (195 KTAS). What affect = is this on power charts or do I just artificially add1500 feet to the chart scale? = << We teach you how to calculate power for your engine without reference to a power chart of any kind - - (you can, ultimately, do it = in your head) during the APS course. Here is the theory. ROP - - power = is almost entirely determined by mass airflow through the engine - - - = which in turn is almost entirely proportional to RPM and MP. A 10% drop in MP = will get you a 10% drop in horsepower to a surprisingly close degree. = Thus, if you open the alt air ram door and get a 5% increase in MP - - then = you will get a 5% increase in HP - - - when ROP, and all else the same. >> a. The added LASAR ignition system has 2 effects: i. A hotter spark, burning more fuel in the cylinder. The consequences are a 15-20 degree rise in cylinder head temps and a = 90-degree reduction in EGTs. This seems to lead to increased torque, thus = increased thrust HP because the prop pitch is increased to retain the RPM. This = is seen as a sprightlier take-off run, a higher climb rate and better = general performance. What is the affect on determining % power? << Huge misconception here. "hotter sparks" - - means a higher = voltage longer duration spark. DOES NOT BURN MORE FUEL. That is marketing = hype. The 15-20 degree rise in CHT and the 90 degree reduction EGTs is due to = ONE AND ONLY ONE THING - - a bad thing - - at that. =20 =20 If I take any stock IO-320/360/540 and if I advance the timing a few degrees it will raise the CHT 15 to 30 degrees and it will drop the = EGTs by 50 to 100F. That is the ONLY effect you are seeing. Repeat - - the = ONLY effect - - - has nothing to do with "hotter sparks".=20 =20 MOST of these engines are already OVER TIMED on takeoff with stock = factory timing. Advancing the timing further - - at least at sea level on a standard day - - is probably counter productive with respect to HP... = and it is guaranteed to substantially increase the peak internal cylinder = pressures in an undesirable manner.=20 =20 >> ii. At some RPM/MAP point, the =E2=80=9Cspark=E2=80=9D is = advanced, resulting in higher power and more efficiency. How does this affect % power at full power and best power? What is the affect when running LOP? d. The addition of a harmonic dampener, which for fixed pitch props generally, increases the full power rpm by 100. Does this improve my = power also by increasing the flywheel affect (allowing an increase in = prop pitch to retain rpm)? << At this point, your curiosity is getting beyond what I can = do without a charts and graphs. When operating LOP at altitude, = properly advancing the spark timing (PROPERLY) will improve the Hp by as much as = 3 to 5% - - essentially for free in that it does not require more = gasoline. =20 =20 >> Another words, what are the gross parameters I can use to operate = LOP? What are the steps I can use when operating ROP and how many degrees = (EGT) rich at certain power levels. << We spend about 6 hours on this subject and about 40 power point = slides and throw in a test stand run from the engine test stand - - to = properly answer that question. >> With the above listed modifications that appear to affect power, = should I increase the takeoff fuel flow to something greater than its current = 15.1 gph? << Probably. Almost certainly. But without more and better data, = one can't say for certain. You need a takeoff BSFC of up around 0.6 on = the Lycoming NA engines. Maybe higher with the high compression piston and = the spark advance. >> Someone help us little guys with answers to our questions! How = else can we achieve harmony with the universe? Huh? Huh? << Darn... harmony with the universe ? That is above my pay = grade! Regards, George =20 ------_=_NextPart_001_01C32FCB.2D3095F2 Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable

>> =E2=80=9CProp = efficiency goes=20 down after 2500 rpm.=E2=80=9D = Even though=20 Klaus runs rings around larger engined planes when he is operating in = excess of=20 3000 rpm? Does the = efficiency go=20 down, but thrust HP is increased? =20 Am I losing power by operating at 2660 rpm (a felt sweet=20 spot)? <<

Prop efficiency is a very = complicated=20 issue. Depends on a whole lot of factors - - including RPM, = HP,=20 diameter, Mach number, air density.... advance ratio, and=20 more.

You can get more thrust at the = higher RPM=20 because you make more horsepower at the higher RPM. One can = do this=20 in spite of the lower prop efficiency at the higher RPM. =20

What is = 75% power for=20 my Lycoming I/O 320 engine equipped with a 70 inch Hartzell = constant speed=20 prop? I have made = the following=20 adjustments:

        = By=20 definition, 75% power in the airplane world is any power = setting at=20 which the engine produces torque at an RPM to generate a horsepower = that=20 is 0.75 x the max rated horsepower. It has nothing to do = wit your=20 prop - - whatever size it is.

        = By the=20 way, "percent power" numbers are largely over emphasized in the = minds of=20 pilots.

       &nb= sp;   >>=20 Different pistons were used to raise the compression ratio = from 8.5 to=20 9:1. How was that = done? Did it reduce my cubic = inches or=20 somehow increase the stroke?  <<

       &nb= sp;   =20 No. The change in piston height to go from 8.5:1 to 9:1 is very = small.   In fact, the "swept volume" remains the = same. We are=20 talking about changes in piston height on the order of 20 or 30 = thousandths of=20 an inch.

       &nb= sp; >> A=20 non-filtered induction ram air system is used which raises the = manifold=20 pressure 1.5=E2=80=9D Hg at 180 KIAS (195 KTAS). =20 What affect is this on power charts or do I just artificially = add1500=20 feet to the chart scale?  <<

       &nb= sp;   =20 We teach you how to calculate power for your engine without reference = to a=20 power chart of any kind - - (you can, ultimately, do it in your head) = during=20 the APS course.   Here is the theory. ROP - - power = is almost=20 entirely determined by mass airflow through the engine - - - which in = turn is=20 almost entirely proportional to RPM and MP.   A 10% drop in = MP will=20 get you a 10% drop in horsepower to a surprisingly close=20 degree.      Thus, if you open the alt air = ram door=20 and get a 5% increase in MP - - then you will get a 5% increase in HP = - - -=20 when ROP, and all else the same.

>>   =20 a.   The added LASAR ignition system has 2 = effects:

A hotter spark, burning = more fuel in=20 the cylinder. The = consequences=20 are a 15-20 degree rise in cylinder head temps and a 90-degree = reduction in=20 EGTs. This seems to = lead to=20 increased torque, thus increased thrust HP because the prop pitch = is=20 increased to retain the RPM. =20 This is seen as a sprightlier take-off run, a higher climb = rate and=20 better general performance. = What is the affect on determining % power?   <<

    Huge misconception = here. =20 "hotter sparks" - - means a higher voltage longer duration = spark. DOES=20 NOT BURN MORE FUEL. That is marketing hype. The 15-20 = degree rise=20 in CHT and the 90 degree reduction EGTs is due to ONE AND ONLY ONE = THING =20 - - a bad thing - - at that.

If I take any stock IO-320/360/540 = and if I=20 advance the timing a few degrees it will raise the CHT 15 to 30 = degrees and it=20 will drop the EGTs by 50 to 100F.   That is the ONLY effect = you are=20 seeing.   Repeat - - the ONLY effect - - - has nothing to = do with=20 "hotter sparks".

MOST of these engines are already = OVER TIMED on=20 takeoff with stock factory timing.   Advancing the timing = further -=20 - at least at sea level on a standard day - - is probably counter = productive=20 with respect to HP... and it is guaranteed to substantially increase = the peak=20 internal cylinder pressures in an undesirable manner.

>> ii.      =20 At some RPM/MAP point, the =E2=80=9Cspark=E2=80=9D is = advanced, resulting in higher=20 power and more efficiency. = How=20 does this affect % power at full power and best power? What is the affect when = running=20 LOP?

The = addition of a=20 harmonic dampener, which for fixed pitch props generally, = increases the=20 full power rpm by 100. = Does=20 this improve my power also by increasing the flywheel affect = (allowing=20 an     increase= in=20 prop pitch to retain rpm)?  =20 <<

       &nb= sp;   =20 At this point, your curiosity is getting beyond what I can do = without a=20 charts and graphs.    When operating LOP at altitude, = properly=20 advancing the spark timing (PROPERLY) will improve the Hp by as much = as 3 to=20 5% - - essentially for free in that it does not require = more=20 gasoline.

>>  Another words, = what are=20 the gross parameters I can use to operate LOP? What are the steps I can = use when=20 operating ROP and how many degrees (EGT) rich at certain power = levels. <<

    We spend=20 about 6 hours on this subject and about 40 power point slides = and throw=20 in a test stand run from the engine test stand - - to properly answer = that=20 question.

>>  With the = above=20 listed modifications that appear to affect power, should I increase = the=20 takeoff fuel flow to something greater than its current 15.1 = gph? <<

       = Probably. =20 Almost certainly. But without more and better data, one can't = say for=20 certain.   You need a takeoff BSFC of up around 0.6 = on the=20 Lycoming NA engines. Maybe higher with the high compression piston = and the=20 spark advance.

>>  Someone = help us=20 little guys with answers to our questions! How else can we achieve = harmony with=20 the universe? Huh? Huh?  <<

        Darn... harmony with = the universe=20 ?   That is above my pay grade!

Regards, =20 George

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