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Blackwell Exhaust

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ChangDriver

Joined: 15 Sep 2007
Posts: 266

Posted: Mon Feb 09, 2009 6:04 am Post subject: Blackwell Exhaust

Is anyone out there flying either a Housai or M-14 with Bill's new tuned exhaust?  I am wondering what performance increase you've seen AND what is the change in exhaust noise (how much louder is it).



Thanks,



Craig

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MarkWDavis

Joined: 03 Jan 2007
Posts: 104
Location: Syracuse, KS

Posted: Mon Feb 09, 2009 7:53 am Post subject: Blackwell Exhaust

My concern, after looking at the pictures of the system, on the typical 

M-14P without gapless rings is the potential of a hydraulic lock on the 

bottom cylinders that can't drain and puke out the occasional glug of oil 

they all do when pulling them through.  If it didn't cause a lock, the top 

of the wings would have a nice slick black walkway after startup.



Mark Davis

N44YK



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nigel(at)yakdisplay.com
Guest

Posted: Mon Feb 09, 2009 9:18 am Post subject: Blackwell Exhaust

That's why the oil drain kit is a must - AND it's also a must to be used

CORRECTLY!

i.e. Open after engine shutdown and LEAVE open. Only close after pulling

through before start.

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MarkWDavis

Joined: 03 Jan 2007
Posts: 104
Location: Syracuse, KS

Posted: Mon Feb 09, 2009 10:34 am Post subject: Blackwell Exhaust

Nigel,

      Even with the oil drain kit in the lower intake tubes opened up on 

shutdown, I still get oil out of the stacks at times.  That's the oil I'm 

worried about backing up into the cylinders or blowing on top of the wing. 

Exhaust side, not intake side.  On the stock exhaust system any oil that 

leaks down into a cylinder with an open exhaust valve can just let gravity 

do its thing and run on out just like the oil does on the intake side with a 

drain kit.



Mark Davis

N44YK



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nigel(at)yakdisplay.com
Guest

Posted: Mon Feb 09, 2009 11:35 am Post subject: Blackwell Exhaust

Yes, so do I. That oil is from the inlets that can't be sucked up from the

inlets just by pulling through - so it gets pulled into the cylinders on

start. Because of the drain kit, (in theory) the amount of oil left in the

inlets is too small to hydraulic a cylinder.



Even if the oil backs up on the exhaust side, surely the pull through is

going to force it out of the cylinder via the exhaust valve exhaust anyway?

And then the exhaust valve closes stopping that oil coming back in. The next

stroke is induction (exhaust valve still closed), and the next compression

(still closed). The hydraulic lock only happens on the compression - so the

only way oil can come in for that is from the INLET side - hence the drains

being on the inlets.



Or am I missing something here?



Nigel.



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tjyak50

Joined: 31 May 2007
Posts: 81
Location: Phoenix, AZ

Posted: Mon Feb 09, 2009 12:03 pm Post subject: Re: Blackwell Exhaust

The Blackwell exhaust system has a drain built into it.

Any headers with a low spot are connected to the exhaust drains.

Different from the intake drain since it is high temp.



It prevents any oil from ever building up in the exhaust system.

T-28 has a similar system if I recall, although they just have holes in the exhaust.  Blackwells system drains to a common point.



Actually makes the airplane very tidy.

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dsavarese0812(at)bellsout
Guest

Posted: Mon Feb 09, 2009 1:56 pm Post subject: Blackwell Exhaust

All true Nigel.  But what happens if the piston is  already on the compression stroke while pulling the prop through and there is  sufficient oil collected in the combustion chamber when the piston gets to close  to TDC?  Then it's too late for an opening exhaust valve to be of any  benefit.

 Dennis

  

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ChangDriver

Joined: 15 Sep 2007
Posts: 266

Posted: Tue Feb 10, 2009 11:10 am Post subject: Re: Blackwell Exhaust

Are there considerations for having exhaust heat a) close to the firewall, b) exiting onto paint, etc.  I can't imagine this is a good thing.



Dennis:  if the engine is on the compression stroke, both valves are closed.  So, on pull through, if oil were pulled in via the exhaust valve, wouldn't it get pushed out on the next phase of the cycle...intake.



Craig

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dsavarese0812(at)bellsout
Guest

Posted: Tue Feb 10, 2009 1:13 pm Post subject: Blackwell Exhaust

Oil will not get pulled in via the exhaust valve.  The  intake stroke is suction.  So oil can not get "pushed" out.  However,  if one feels the prop stop caused by a hydraulic lock, if you move the prop  backwards and allow the intake valve to open on the locked cylinder (remember  intake comes before compression), it can let the oil run out into the lower  intake tubes which hopefully have the intake drain kit installed or just  plugs installed in the intake tubes.  Otherwise you really should pull the  rear spark plugs on the lower cylinders to clear the lock.

 Dennis

  

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