X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from imo-d20.mx.aol.com ([205.188.139.136] verified) by logan.com (CommuniGate Pro SMTP 5.2c1) with ESMTP id 2574002 for flyrotary@lancaironline.net; Sun, 09 Dec 2007 23:51:34 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.188.139.136; envelope-from=Lehanover@aol.com Received: from Lehanover@aol.com by imo-d20.mx.aol.com (mail_out_v38_r9.3.) id q.d0f.1934fc89 (65098) for ; Sun, 9 Dec 2007 23:50:51 -0500 (EST) From: Lehanover@aol.com Message-ID: Date: Sun, 9 Dec 2007 23:50:51 EST Subject: Pport timing To: flyrotary@lancaironline.net MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="part1_d0f.1934fc89.348e1fab_boundary" X-Mailer: 8.0 for Windows sub 6808 X-Spam-Flag: NO --part1_d0f.1934fc89.348e1fab_boundary Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable > Thanks Lynn, >=20 > It goes without saying that I always appreciate your contribution. I may=20 > have to refer back to what you were saying to clarify some points. >=20 > I now understand the closing event has the most effect on the mid range=20 > power we need in Aviation (why is that? and why is your BP closing of 80 d= egrees=20 > flowing very little - there seems to be plenty of suction still going on?)= =20 The intake closing event is shown as ABDC. After Bottom Dead Center, in the=20 case of the intake cycle is in the top of the rotor housing. (a bit confusin= g)=20 and since BDC for both intake and exhaust cycles is the largest volume=20 attainable, that closing point is after the volume is already decreasing. So= some of=20 the mixture is being forced back into the intake manifold. Early closing mea= ns=20 more mixture is trapped in the closing chamber to be used no matter what the state of tune. So at lower and medium speeds where=20 inertial charging is low to nonexistant, the engine still developes some amo= unt of=20 power. The later the closing point, the more accurate the tune must be to=20 support the same performance down low, as only high inertia can overcome the= mixture=20 being pushed out from the closing chamber.=20 So an early closing point captures more mixture, at lower speeds, and low an= d=20 medium power is improved. Same as advancing the cam in a piston engine. Even= =20 though it screws up the other three timing functions, the early closing inta= ke=20 valve makes so much difference it is worth the work to do it. In a minor way= =20 this affects the effective compression ratio as well. More degrees of closed= =20 chamber means higher compression. This becomes painfully obvious when measur= ing=20 compression at cranking speeds. My Fiats had 245 pounds of compression=20 cranking. Run the engine 10 seconds and shut it off because the NOX would fr= y you=20 eyes. I could retard the intake cam 5 degrees and loose 10 pounds. and that closing event should not exceed 70 degrees ABDC. This is probably=20 something=20 > you told me previously and I hadn't remembered ( or understood properly).=20 > However the Mazda Factory PP is 75 degree IC, perhaps allowing for higher=20= HP=20 > at the higher RPM range. Whereas the Leman's engine seems to be about 70=20 > degrees ABDC. All accurate. The Lemans engine you should point out, was only turned up to=20 about 7,600 RPM. So the early closing point was adequate. Most of the fine w= ork=20 they did was to pump up the mid range so the engine could have a broad power= =20 band. The Lemans circuit has a very slow first gear corner, and a 230 MPH=20 straightaway. It is typical when fooling with piston engines to measure degr= ees of=20 open only after a valve is .050" off its seat. So little flow is available=20 below that point that it is not counted. So your cam card will have lobe=20 centers, total lift, lift minus the valve lash, and timing (measured once th= e valve=20 is at .050") (Crane gives you duration at running lash as well). For timing I Use oil in the port. When the oil begins to flow I mark the por= t=20 as being open.=20 There is nothing to record from a dial indicator or similar that I can use t= o=20 determine this as in the piston engines.=20 So, the oil works fine. Without the radius the port would open at a bit less= =20 than 80 degrees. So it is not as exotic as it at first sounds. >=20 > Secondly, the later the opening event the better ( I understood that one)=20 > because of overlap and contamination of the inlet charge at lower RPM. Now= if=20 > we could just close it before we open it, we would be way ahead - but of=20 > course that is not possible, so the squat=A0PP is the next best shape and=20= timing. >=20 >=20 > =A0 > So the opening later is better; but the closing later is not good! As we s= ay=20 > in Australia - BUGGER!! > =A0 > Anyhow there is another reference in your response which I don't quite=20 > understand and that is "So even with red lines at or above 8,000 RPM this=20= modest=20 > port closing is more than adequate (this is understood).=20 If I remember correctly (this becomes less likely with time) " Can you=20 explain the =20 last > sentence about (less likely with time). Do you mean later openings=20 > gave better higher RPM, HP in the racing industry.=20 Nope. It means I am over 65 now and remembering anything is difficult. LE= H > TIA > George (down under) > =A0 >=20 ************************************** Check out AOL's list of 2007's hottest=20 products. (http://money.aol.com/special/hot-products-2007?NCID=3Daoltop00030000000001) --part1_d0f.1934fc89.348e1fab_boundary Content-Type: text/html; charset="ISO-8859-1" Content-Transfer-Encoding: quoted-printable
Thanks Lynn,

It goes without saying that I always appreciate your contribution. I may hav= e to refer back to what you were saying to clarify some points.

I now understand the closing event has the most effect on the mid range powe= r we need in Aviation (why is that? and why is your BP closing of 80 degr= ees flowing very little - there seems to be plenty of suction still going on= ?)


The intake closing event is shown as ABDC. After Bottom Dead Center, in the= case of the intake cycle is in the top of the rotor housing. (a bit confusi= ng) and since BDC for both intake and exhaust cycles is the largest volume a= ttainable, that closing point is after the volume is already decreasing. So=20= some of the mixture is being forced back into the intake manifold. Early clo= sing means more mixture is trapped in the closing chamber to be used
no matter what the state of tune. So at lower and medium speeds where inerti= al charging is low to nonexistant, the engine still developes some amount of= power. The later the closing point, the more accurate the tune must be to s= upport the same performance down low, as only high inertia can overcome the=20= mixture being pushed out from the closing chamber.

So an early closing point captures more mixture, at lower speeds, and low an= d medium power is improved. Same as advancing the cam in a piston engine. Ev= en though it screws up the other three timing functions, the early closing i= ntake valve makes so much difference it is worth the work to do it. In a min= or way this affects the effective compression ratio as well. More degrees of= closed chamber means higher compression. This becomes painfully obvious whe= n measuring compression at cranking speeds. My Fiats had 245 pounds of compr= ession cranking. Run the engine 10 seconds and shut it off because the NOX w= ould fry you eyes. I could retard the intake cam 5 degrees and loose 10 poun= ds.


and that closing event should not exceed 70 degrees ABDC. This is probably s= omething
you told me previously and I h= adn't remembered ( or understood properly). However the Mazda Factory PP is=20= 75 degree IC, perhaps allowing for higher HP at the higher RPM range. Wherea= s the Leman's engine seems to be about 70 degrees ABDC.
<= FONT COLOR=3D"#000000" BACK=3D"#ffffff" style=3D"BACKGROUND-COLOR: #ffffff"= SIZE=3D2 PTSIZE=3D10 FAMILY=3D"SANSSERIF" FACE=3D"arial" LANG=3D"0">


All accurate. The Lemans engine you should point out, was only turned up to= about 7,600 RPM. So the early closing point was adequate. Most of the fine=20= work they did was to pump up the mid range so the engine could have a broad=20= power band. The Lemans circuit has a very slow first gear corner, and a 230=20= MPH straightaway. It is typical when fooling with piston engines to measure=20= degrees of open only after a valve is .050" off its seat. So little flow is=20= available below that point that it is not counted. So your cam card will hav= e lobe centers, total lift, lift minus the valve lash, and timing (measured=20= once the valve is at .050")
(Crane gives you duration at running lash as well).

For timing I Use oil in the port. When the oil begins to flow I mark the por= t as being open.
There is nothing to record from a dial indicator or similar that I can use t= o determine this as in the piston engines.
So, the oil works fine. Without the radius the port would open at a bit less= than 80 degrees.
So it is not as exotic as it at first sounds.


Secondly, the later the opening event the better ( I understood that one) be= cause of overlap and contamination of the inlet charge at lower RPM. Now if=20= we could just close it before we open it, we would be way ahead - but of cou= rse that is not possible, so the squat=A0PP is the next best shape and timin= g.



=A0
So the opening later is better; but the closing later is not good! As we sa= y in Australia - BUGGER!!
=A0
Anyhow there is another reference in your response which I don't quite under= stand and that is "So even with red lines at or above 8,000 RPM this modest=20= port closing is more than adequate (this is understood).

  If I remember correctly (this becomes less likely with time)=20= " Can you explain the  
  last
sentence about (les= s likely with time). Do you mean later openings gave better higher RPM, HP i= n the racing industry.


   Nope. It means I am over 65 now and remembering anything is di= fficult. LEH

TIA
George (down under)
=A0




**************************************
Check out AOL's= list of 2007's hottest products.
(http://money.aol.com/special/hot-produ= cts-2007?NCID=3Daoltop00030000000001) --part1_d0f.1934fc89.348e1fab_boundary--