Return-Path: Sender: (Marvin Kaye) To: flyrotary Date: Thu, 27 Mar 2003 10:57:43 -0500 Message-ID: X-Original-Return-Path: <13brv3@mchsi.com> X-SpamCatcher-Score: 0 [] Received: from sccmmhc02.mchsi.com ([204.127.203.184] verified) by logan.com (CommuniGate Pro SMTP 4.1b1) with ESMTP id 2088338 for marv@lancaironline.net; Thu, 27 Mar 2003 10:55:20 -0500 Received: from rad ([12.218.74.116]) by sccmmhc02.mchsi.com (InterMail vM.4.01.03.27 201-229-121-127-20010626) with ESMTP id <20030327155519.DGON8681.sccmmhc02.mchsi.com@rad>; Thu, 27 Mar 2003 15:55:19 +0000 Reply-To: <13brv3@mchsi.com> From: <13brv3@mchsi.com> X-Original-To: "'John Slade'" X-Original-Cc: "'Marvin Kaye'" Subject: RE: [FlyRotary] Re: boost control? X-Original-Date: Thu, 27 Mar 2003 09:55:12 -0600 X-Original-Message-ID: <000001c2f479$4378b700$0201a8c0@rad> MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0001_01C2F446.F8DE4700" X-Priority: 3 (Normal) X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook, Build 10.0.4510 Importance: Normal In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 This is a multi-part message in MIME format. ------=_NextPart_000_0001_01C2F446.F8DE4700 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable For some reason my server (bellsouth.net) is suddenly blacklisted on by = the flyrotary server. Make sure you get that fixed in the next couple months :-) DSL is = finally becoming available here in May, and I've already signed up. =20 Rusty / Marv Interesting reading you're discussion and agreement on turbo control. = This pretty much describes the route I'm planning. I have a three lever = throttle quadrant installed - throttle, boost and cowl flaps. (mixture is on the = EC2 computer panel). You're description of probable usage makes sense to me. Just one question.... I've just decided to use the dual lever quadrant that the previous = builder had set up for a Lycoming. In my case, it will be throttle and = wastegate. =20 What's the difference between pop-off and blow-off? A pop-off valve is just a spring loaded device, that dumps pressure when it's over a certain set point. There's no vacuum line, or control to it = at all. On a car, this is purely a safety valve, and would be set for a = couple psi over the max boost you expect to run. =20 A blow-off valve, is not set for any pressure, but uses a vacuum line to open and close it. These are used in cars to dump the intake pressure during shifts. Say your running through the gears, and the engine is at high rpm, and full boost. When you shift, you close the throttle, = shift, then open the throttle again. Before you shift, the intake is = pressurized at whatever your boost is set for, say 10 psi in the case of a stock 3rd = gen RX-7. The turbo is spinning like mad, and can't stop instantaneously, = so when you close the throttle, you effectively plug up the outlet of the = turbo compressor, which creates a big spike in pressure on the turbo side of = the throttle plates. This pressure is bad for the turbo. Of course at the = same time you create this big pressure on the turbo side, there is also a big vacuum created on the engine side of the throttle plates. This vacuum = is used, via vacuum line, to open the blow-off valve. =20 For our purposes of turbo normalizing, where we'll have the pop-off = valve set to 1 or 2 psi, we really shouldn't have to worry about excess = pressure from rapid closing of the throttle. The only thing I'm still concerned about, is how quickly the valve will recover. You would hope that it = will basically maintain the set pressure, but it might not do that very well. = I do like the idea of having a light to warn of overpressure, and I = imagine that I'll be able to set that with Tracy's EM-2.=20 I'm serious - this is not a 'straight line'. LOL! You're taking all the fun out of answering this :-) Are you guys going to Sun & Fun? John Slade I'm not planning to go this year, but next year, I hope to be there with = the RV-3. =20 Cheers, Rusty =20 PS- Marvin, feel free to post this to the list if you wish. =20 ------=_NextPart_000_0001_01C2F446.F8DE4700 Content-Type: text/html; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Message

For some reason my server (bellsouth.net) is suddenly=20 blacklisted on by the flyrotary server.

Make = sure you get that=20 fixed in the next couple months  :-)   DSL is = finally=20 becoming available here in May, and I've already signed=20 up.  

Rusty / Marv
Interesting reading you're discussion and agreement = on turbo=20 control. This pretty much describes the route I'm planning. I have a = three lever=20 throttle quadrant installed - throttle, boost and cowl flaps. (mixture = is on the=20 EC2 computer panel). You're description of probable usage makes sense to = me.=20 Just one question....

I've just decided to use = the dual lever=20 quadrant that the previous builder had set up for a Lycoming.  In = my case,=20 it will be throttle and wastegate. 

What's the = difference=20 between pop-off and blow-off?

A pop-off valve is just a = spring loaded=20 device, that dumps pressure when it's over a certain set = point. =20 There's no vacuum line, or control to it at all.  On a car, = this is=20 purely a safety valve, and would be set for a couple psi over the max = boost you=20 expect to run. 

A blow-off valve, is not = set for any=20 pressure, but uses a vacuum line to open and close it.  These are = used in=20 cars to dump the intake pressure during shifts.  Say your running = through=20 the gears, and the engine is at high rpm, and full = boost.  When you=20 shift, you close the throttle, shift, then open the throttle=20 again.  Before you shift, the intake is pressurized at = whatever=20 your boost is set for, say 10 psi in the case of a stock 3rd gen=20 RX-7.  The turbo is spinning like mad, and can't stop = instantaneously, so=20 when you close the throttle, you effectively plug up the outlet of the = turbo=20 compressor, which creates a big spike in pressure on the turbo side of = the=20 throttle plates.  This pressure is bad for the = turbo.  Of=20 course at the same time you create this big pressure on the turbo side, = there is=20 also a big vacuum created on the engine side of the throttle = plates.  This=20 vacuum is used, via vacuum line, to open the blow-off valve.  =

For our purposes of turbo = normalizing,=20 where we'll have the pop-off valve set to 1 or 2 psi, we really = shouldn't have=20 to worry about excess pressure from rapid closing of the = throttle.  =20 The only thing I'm still concerned about, is how quickly the valve will=20 recover.  You would hope that it will basically maintain the set = pressure,=20 but it might not do that very well.  I do like the idea of having a = light=20 to warn of overpressure, and I imagine that I'll be able to set that = with=20 Tracy's EM-2. 

I'm serious - this is not a 'straight line'.

LOL!  You're taking = all the fun=20 out of answering this :-)

Are you guys going to Sun &=20 Fun?
John Slade

I'm=20 not planning to go this year, but next year, I hope to be there with the = RV-3.
 
Cheers,
Rusty
 
PS-=20 Marvin, feel free to post this to the list if you = wish.
 



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