X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from fed1rmmtao02.cox.net ([68.230.241.37] verified) by logan.com (CommuniGate Pro SMTP 4.3c5) with ESMTP id 931977 for flyrotary@lancaironline.net; Wed, 04 May 2005 00:45:40 -0400 Received-SPF: none receiver=logan.com; client-ip=68.230.241.37; envelope-from=ALVentures@cox.net Received: from BigAl ([68.7.14.39]) by fed1rmmtao02.cox.net (InterMail vM.6.01.04.00 201-2131-118-20041027) with ESMTP id <20050504044452.MAOC22430.fed1rmmtao02.cox.net@BigAl> for ; Wed, 4 May 2005 00:44:52 -0400 From: "Al Gietzen" To: "'Rotary motors in aircraft'" Subject: RE: [FlyRotary] Static MAP readings? Date: Tue, 3 May 2005 21:45:05 -0700 Message-ID: <000001c55064$0af139e0$6400a8c0@BigAl> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C55029.5E9261E0" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.6626 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C55029.5E9261E0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Greetings, =20 I'm still a bit concerned about the static MAP readings that I'm = getting. This isn't something that just happened, but rather has been going on = for at least the life of this particular intake setup. At on point, I was = almost convinced that the TWM TB ports were just not providing an accurate = reading, but now I'm almost convinced that they are. Has anyone measured MAP at = WOT static? =20 =20 Yes. As you may recall, I also run with the TWM TB, and I also see = lower MAP than the local atmospheric pressure. That is quite likely as it = should be, or if not; it doesn't matter. The MAP reading depends on where you measure it. If you measure MAP behind a big TB BEFORE the runners, as = Tracy (and I guess most others) do; you'd expect to see atmospheric pressure = at WOT. We are measuring it near the ports, and at the very least about; = what 4" down the relatively small TB barrel - a place where the velocity is = high; as it should be. =20 =20 There may be some error introduced by the port being just downstream = from the throttle plate shaft, but the guys at TWM say "no", FWIW. On the = dyno at WOT at 5300 rpm with a local barometric pressure of 29.5", the MAP reading was 27.5". At 6000 rpm, WOT, MAP had dropped to about 26.5", = and it was putting out close to 85 hp/rotor (SAE corrected, which means actual measured of just over 80) with 9.0 rotors. At 7000 rpm the MAP reading = was 23.5" and the power was still climbing at 95 hp/rotor. Not bad for = engine with about 2 hours of running since rebuild. Whatever that MAP reading = is, I don't think that there is a significant power penalty that goes with = it. =20 Hoping this makes you feel better, =20 Al =20 I got the following results in a few tests the other day: =20 1- 27.6" This was with my normal configuration, which is an inlet = inside the radiator duct, feeding a 3" SCEET hose, to a fiberglass duct that = covers the two barrels of a TWM TB. =20 =20 2- 26.3"-27.0" (erratic probably due to prop blast across the inlet) = This was with the SCEET hose removed from the TB fiberglass duct. =20 =20 3- 27.4" This is with a fairly small K&N cone filter on the inlet to = the TB duct where the SCEET hose normally goes.=20 =20 From this, I see that the K&N filter seem to have no significant effect = on the MAP, which is good, though I still don't know if I can fit it in = there. =20 I've got some numbers from Ed, and also have an idea what Tracy runs, = but those have always been in-flight, WOT, low level runs. I'm going to try that at about 1000 ft at some point, but would also like to know what = folks run static. Anyone got any readings? =20 Thanks, Rusty (not willing to give away free power) ------=_NextPart_000_0001_01C55029.5E9261E0 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message

Greetings,

=

 

I'm still a bit concerned = about the static MAP readings that I'm getting.   This isn't something = that just happened, but rather has been going on for at least the life of = this particular intake setup.  At on point, I was almost convinced that = the TWM TB ports were just not providing an accurate reading, but now I'm almost convinced that they are.  Has anyone measured MAP at WOT = static? 

 

Yes.  As you may recall, I = also run with the TWM TB, and I also see lower MAP than the local atmospheric = pressure.  That is quite likely as it should be, or if not; it doesn’t = matter.  The MAP reading depends on where you measure it.  If you measure MAP behind = a big TB BEFORE the runners, as Tracy (and I guess most others) do; you’d expect to see = atmospheric pressure at WOT.  We are measuring it near the ports, and at the = very least about; what 4” down the relatively small TB barrel – a place = where the velocity is high; as it should be. 

 

There may be some error = introduced by the port being just downstream from the throttle plate shaft, but the = guys at TWM say “no”, FWIW.  On the dyno at WOT at 5300 rpm = with a local barometric pressure of 29.5”, the MAP reading was = 27.5”.  At 6000 rpm, WOT, MAP had dropped to about 26.5”, and it was putting out close = to 85 hp/rotor (SAE corrected, which means actual measured of just over 80) = with 9.0 rotors.  At 7000 rpm the MAP reading was 23.5” and the power = was still climbing at 95 hp/rotor.  Not bad for engine with about 2 hours of = running since rebuild.  Whatever that MAP reading is, I don’t think that = there is a significant power penalty that goes with it.

 

Hoping this makes you feel = better,

 

Al

 

I got the following results = in a few tests the other day:

 

1- 27.6" &nbs= p; This was with my normal configuration, which is an inlet inside the radiator = duct, feeding a 3" SCEET hose, to a fiberglass duct that covers the two = barrels of a TWM TB. 

 

2- 26.3"-27.0" = (erratic probably due to prop blast across the inlet)   This was with = the SCEET hose removed from the TB fiberglass duct. 

 

3- = 27.4"    This is with a fairly small K&N cone filter on the inlet to the TB duct = where the SCEET hose normally goes.

 

From this, I see that the = K&N filter seem to have no significant effect on the MAP, which is good, = though I still don't know if I can fit it in there. 

 

I've got some numbers from = Ed, and also have an idea what Tracy runs, but those have always been in-flight, WOT, low level runs.  = I'm going to try that at about 1000 ft at some point, but would also like to = know what folks run static.  Anyone got any readings?

 

Thanks,

Rusty (not willing to give = away free power)

------=_NextPart_000_0001_01C55029.5E9261E0--