REFLECTOR: Exhaust systems

[Scott Derrick]

Mark,

 From my limited experience, I burnt a 3 blade Performance prop on 
Velocity.  Actual charring.

The more cylinders you have going into a collector the hotter the exit 
stream.

The closer the exit stream is the the prop the hotter your prop.  My 
4-into-1 was pointed straight back and about 6-8 inches from the prop.

The more perpendicular the exhaust exit to the air stream the more 
mixing of exhaust to ambient you get, thus a cooler exhaust.  This is a 
drag(sic!) because the more perpendicular your exhaust is to the air 
stream the more drag you get.

If you have more than one exhaust exit(ie. 2-into-1 or 4-into-4 oe 
3-into-1) the wider they are apart the cooler the prop.

Running LOP greatly reduces your exhaust exit temps.

Diffusers on the ends of the exhaust tubes can reduce the temps.

We need to put them all together to get a consistent result.

Scott


Mark Means wrote:
> Mike,
> 
> So does this mean 11" is okay or do you have the burnt prop problem?
> 
> Did you start closer to the prop and cut it back to where 11" is the
> minimum?
> 
> I'm trying to design a custom exhaust and since this is a "hot" topic wanted
> to find out what the general experience is with "minimum acceptable"
> distance to avoid the problem. Thanks for anyone's input.
> 
> Mark
> 
> 
> ----- Original Message -----
> From: "Mike Pollock" <m.pollock@verizon.net>
> To: <reflector@tvbf.org>
> Sent: Thursday, July 10, 2003 8:24 AM
> Subject: RE: REFLECTOR: Exhaust systems
> 
> 
> 
>>Ours is about 11 inches from the prop.
>>
>>Mike
>>
>>-----Original Message-----
>>From: reflector-admin@tvbf.org [mailto:reflector-admin@tvbf.org]On
>>Behalf Of Mark Means
>>Sent: Thursday, July 10, 2003 6:57 AM
>>To: reflector@tvbf.org
>>Subject: Re: REFLECTOR: Exhaust systems
>>
>>
>>Some are talking about longer prop extensions solving the problem but if
> 
> one
> 
>>is using a different exhaust scheme this doesn't help define what we
> 
> really
> 
>>need to know.......  is there any consensus on how far the prop needs to
> 
> be
> 
>>from the pipe to avoid burning? Thanks.
>>
>>Mark Means
>>
>>
>>----- Original Message -----
>>From: "steve korney" <s_korney@hotmail.com>
>>To: <Reflector@tvbf.org>
>>Sent: Thursday, July 10, 2003 12:21 AM
>>Subject: Re: REFLECTOR: Exhaust systems
>>
>>
>>
>>>Ronnie wrote:
>>>                  ( both incur the wrath of the 1400 degree exhaust.)
>>>
>>>
>>>
>>>
>>>Ronnie...
>>>
>>>The exhaust is only 1400 (f) at the probe...It cools rapidly as it gets
>>>further from the exhaust valve...
>>>
>>>
>>>Best... Steve
>>>
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