I understood the higher pressure caps being used was to compensate for atmospheric pressure dropping with altitude.

If the atmospheric pressure drop at 10K is approx 11psi over sea level then a traditional low pressure cap is not going to provide much margin.

Is there another reason for the higher cap rating?

Steve Izett

On 23/10/2012, at 4:23 AM, Tracy wrote:

I think One of the most restrictive points in the system is the passage to the outlet of the water pump housing.  Remember this is NOT the outlet of the water pump itself.  In the pump housing  is an oval passage that is too small to get two fingers through.  It has been my assumption that this was to make the pressure high in the block at high rpm in order to avoid local boiling in the combustion chamber area.  Hi pressure in the block is a good thing.   I run a 29 PSI cap.

Tracy

Sent from my iPad

On Oct 22, 2012, at 1:05 PM, "Bill Schertz" <wschertz@comcast.net> wrote:

Charlie, I am using two evap cores in parallel, with system pressure limited to 10 psi on the expansion bottle. When the engine is running, the pressure measured at the inlet to the cores (exit of the pump) is a function of RPM and can rise to as much as 20 psi (10 psi over system pressure in the expansion bottle).

 

Having the flow enter the bottom of the radiator and out the top, then going to the inlet of the pump sounds like a good way to avoid problems.

 

Bill Schertz
KIS Cruiser #4045
N343BS
Phase one testing Completed

 

From: Ben Haas

Sent: Monday, October 22, 2012 1:06 PM

To: Rotary motors in aircraft

Subject: [FlyRotary] Re: flow path in conventional radiator

 

Unless there is a serious restriction through the radiator  I can't imagine there would be anything greater then 1 psi over system pressure caused by pump output.  As for the reverse flow, ie, bottom to top,,, It's called counter flow, and yes it can work. My set up has worked flawlessly for 500 hours and I use the Moroso swirl / pressure tank and a air bleed line from the output of the radiator...  About 3 minutes into this video shows my set up.....
 
http://www.youtube.com/watch?v=rCNnEgRkdXc&context=C3e091d3ADOEgsToPDskKmHo69I6bUDuoBHd5YSUfu

Ben Haas
www.haaspowerair.com

 

---

To: flyrotary@lancaironline.net
Date: Mon, 22 Oct 2012 12:40:11 -0500
From: ceengland7@gmail.com
Subject: [FlyRotary] flow path in conventional radiator

I've been doing research on radiators, & my 1st 'experiment' will be a conventionally configured radiator (downflow design) with inlet & pressure cap on top. In reading about issues with conventional radiators, a common complaint is pressure venting due to the water pump + system pressure exceeding the cap's rating. Crossflow types like the Sirocco are supposed to avoid this because the cap is at the mid-point in the flow through the rad, which drops some of the pressure seen by the cap.

Here's my question: Is there any reason a conventional rad can't be fed from the bottom, instead of the top? This would achieve similar effect as the crossflow cap location (all the way to the end of the flow path) & any air could be vented using the existing fittings. I'm also considering the removal of the spring loaded seal, & moving the pressure cap function to a separate swirl can. By doing this, the existing over-pressure port could function as the air removal port in the top tank of the radiator.


What am I missing?

Thanks,

Charlie