Mailing List flyrotary@lancaironline.net Message #48788
From: Mike Wills <rv-4mike@cox.net>
Subject: Re: [FlyRotary] Stoich A/F Ratio?? : [FlyRotary] Re: where's the missing power?
Date: Mon, 19 Oct 2009 21:35:20 -0700
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sorry for the delayed reply again. My bad for creating confusion with my comment re stoich at full throttle. To clarify, stoich (as displayed on my narrow band O2) at full throttle with the mixture knob centered, but I can drive it off scale rich by turning the knob. Not sure if I can richen it enough to bog the engine.
 
Havent had an opportunity to go fly again and look any further into it.
 
Mike
----- Original Message -----
Sent: Friday, October 16, 2009 5:35 AM
Subject: [FlyRotary] Stoich A/F Ratio?? : [FlyRotary] Re: where's the missing power?

Hi Mike,

 

I guess I’m missing something - If your mixture monitor shows stoich at full throttle, then it’s not solely an airflow problem – it appears to me that it’s the lack of sufficient fuel. IF you are at stoich 14.7:1 A/F ratio then that means you have more oxygen available in your system to support burning more fuel = more power.   You should be able to enrich the mixture particularly at full throttle (assuming you are wanting full power at full throttle) to around 12.65:1 air/fuel ratio for best power.  I know you know all of this - that is why I am puzzled by your statement that you feel it’s an airflow problem when on the surface with the Stoich ratio it would appear it’s a lack of sufficient fuel. 

 

 

 

Ed. 

 


From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Mike Wills
Sent: Thursday, October 15, 2009 11:22 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: where's the missing power?

 

Sorry for my absence on a topic I started. My nephew had a skateboarding accident last weekend and is in the hospital in a chemically induced coma until his brain swelling is under control. And I thought car powered airplanes were dangerous. Stay away from skateboards.

 

Tracy - My mixture monitor shows stoich at full throttle. I suspect an airflow issue rather than fuel.

 

Al - my vacuum gauge is located in the plenum directly behind the throttle plates.

 

Lynn - I agree that the TB inlet is horrible and needs a bell mouth. The inlet is also pretty obstructed by the cowl which isnt visible in the pics I sent. I think I'll make an attempt to clean this up some and see if it gets me anywhere. If not I'll live with it for a while.

 

Kelly - always tough to determine if the problem is an engine issue or if the load is simply too much for the engine to overcome. I'm going to experiment with the shallow dive several have suggested and see what happens.

 

Mike

----- Original Message -----

Sent: Tuesday, October 13, 2009 4:21 PM

Subject: [FlyRotary] Re: where's the missing power?

 

Since you have the vacuum gauge, this article will help you use it for troubleshooting.

 

 http://autospeed.com/cms/A_2393/article.html

 

Bill B

 


From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Al Gietzen
Sent: Tuesday, October 13, 2009 7:22 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: where's the missing power?

I dont have a regular manifold pressure gauge, just an industrial type vacuum gauge ( I really gotta get an MP gauge). Anyway, the vacuum gauge was indicating 4" of vacuum.

 

Where are you measuring the 4” vacuum?  If it is near the ports it is no unusual; if it is out before the runners; something is wrong.

 

Al



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