X-Virus-Scanned: clean according to Sophos on Logan.com Return-Path: Received: from relais.videotron.ca ([24.201.245.36] verified) by logan.com (CommuniGate Pro SMTP 5.1.10) with ESMTP id 2196752 for flyrotary@lancaironline.net; Tue, 24 Jul 2007 14:20:47 -0400 Received-SPF: pass receiver=logan.com; client-ip=24.201.245.36; envelope-from=geryvon@videotron.ca Received: from AMDSEMPRON2400 ([66.130.108.152]) by VL-MO-MR004.ip.videotron.ca (Sun Java System Messaging Server 6.2-2.05 (built Apr 28 2005)) with SMTP id <0JLP00H6U49LM9B0@VL-MO-MR004.ip.videotron.ca> for flyrotary@lancaironline.net; Tue, 24 Jul 2007 14:20:10 -0400 (EDT) Date: Tue, 24 Jul 2007 14:19:51 -0400 From: Yvon Cournoyer Subject: Re: [FlyRotary] Re: FUEL SYSTEM PRESSURE To: Rotary motors in aircraft Reply-to: Yvon Cournoyer Message-id: <000c01c7ce1f$440f9b50$6400a8c0@AMDSEMPRON2400> MIME-version: 1.0 X-MIMEOLE: Produced By Microsoft MimeOLE V6.00.2900.3138 X-Mailer: Microsoft Outlook Express 6.00.2900.3138 Content-type: multipart/alternative; boundary="Boundary_(ID_HS32oxyhSOWooO0Ss6Z+8A)" X-Priority: 3 X-MSMail-priority: Normal References: This is a multi-part message in MIME format. --Boundary_(ID_HS32oxyhSOWooO0Ss6Z+8A) Content-type: text/plain; charset=iso-8859-1 Content-transfer-encoding: 7BIT David, Thank you for the explanations, At first I flew my Rotary Powered Zenith 200 with a old Rochester two barrels carburator and a low pressure fuel pump. Never had any problem except for a very rich fuel mixture at altitude and of course the possibility of carb icing...which never materialized. Whenever I felt the carb was beginning to ice up, I would go to full throttle and adopt a full nose up attitude to maximixe heat in the engine compartiment. After a short time, I would continue flying normaly. After a while, I switched to a low pressure EFI system, which I am still flying AND fiddling with after several years... So, actually, I am thinking about going back to carb and low pressure fuel pump. A carb with a fuel leaning capacity...hum...still thinking... Thanks again. Yvon Cournoyer Yvon, don't tell me you are thinking about switching to EFI? :-) Most EFI systems used for rotary aircraft installations work like this: The pump gets turned on, and just pumps away as hard as it can at a more or less constant flow. Pressure is created in the system by the regulator that is placed after the fuel rail. It works like a thumb over the hose to create back pressure, and lets the excess fuel flow back to the tank. So as long as the pump is able to pump just slightly more than the engine is using, fuel pressure remains constant. As soon as the pump cannot keep up with what the engine is burning, i.e. the engine is using more than the pump is pumping, then the fuel pressure very quickly drops and the engine begins to falter. (ie, once the pressure starts to drop the engine starts to falter - skip, misfire, run lean, loose power, surge, or just plain quit). Normally, the pump puts out several times what the engine needs. As the pump starts to fail, flow is reduce but pressure remains unchanged for a while (depending on how fast the pump is failing - in my experience of 1 pump failure, it failed over the course of a few hours). By the time the flow is reduced enough that the pressure starts to drop and the engine starts to falter, the pump is only putting out a fraction of its rated flow. i.e. it has almost failed completely. Better to catch it early if possible. I found the return flow meter useful for that purpose. -- David Leonard Turbo Rotary RV-6 N4VY http://N4VY.RotaryRoster.net http://RotaryRoster.net --Boundary_(ID_HS32oxyhSOWooO0Ss6Z+8A) Content-type: text/html; charset=iso-8859-1 Content-transfer-encoding: 7BIT

David, Thank you for the explanations,

At first I flew my Rotary Powered Zenith 200 with a old Rochester two barrels carburator and a low pressure fuel pump. Never had any problem except for a very rich fuel mixture at altitude and of course the possibility of carb icing...which never materialized. Whenever I felt the carb was beginning to ice up, I would go to full throttle and adopt a full nose up attitude to maximixe heat in the engine compartiment. After a short time, I would continue flying normaly.

After a while, I switched to a low pressure EFI system, which I am still flying AND fiddling with after several years...

So, actually, I am thinking about going back to carb and low pressure fuel pump. A carb with a fuel leaning capacity...hum...still thinking...

Thanks again. Yvon Cournoyer

Yvon, don't tell me you are thinking about switching to EFI? :-)

Most EFI systems used for rotary aircraft installations work like this:

The pump gets turned on, and just pumps away as hard as it can at a more or less constant flow. Pressure is created in the system by the regulator that is placed after the fuel rail. It works like a thumb over the hose to create back pressure, and lets the excess fuel flow back to the tank. So as long as the pump is able to pump just slightly more than the engine is using, fuel pressure remains constant. As soon as the pump cannot keep up with what the engine is burning, i.e. the engine is using more than the pump is pumping, then the fuel pressure very quickly drops and the engine begins to falter. (ie, once the pressure starts to drop the engine starts to falter - skip, misfire, run lean, loose power, surge, or just plain quit).

Normally, the pump puts out several times what the engine needs. As the pump starts to fail, flow is reduce but pressure remains unchanged for a while (depending on how fast the pump is failing - in my experience of 1 pump failure, it failed over the course of a few hours). By the time the flow is reduced enough that the pressure starts to drop and the engine starts to falter, the pump is only putting out a fraction of its rated flow. i.e. it has almost failed completely.

Better to catch it early if possible. I found the return flow meter useful for that purpose.

--
David Leonard

Turbo Rotary RV-6 N4VY
http://N4VY.RotaryRoster.net
http://RotaryRoster.net

--Boundary_(ID_HS32oxyhSOWooO0Ss6Z+8A)--