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HKS Exhaust

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rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Wed Nov 21, 2018 5:44 am Post subject: HKS Exhaust

Bill, Something got me thinking last night after I wrote to you about my experience with props on a completely non prop notion. I went digging in my HKS file and found what I was looking for.Measure your exhaust from exhaust port to the join (collector) of the two pipes. This distance should be 500 mm (~19.68"). If it's more or less than that there's your problem. This distance was shared by the HKS importer with a fellow on the HKS forum. Contact Mark Bierle at Earth Aircraft for advice, too. He's done a lot of research into HKS exhaust pipes working correctly. You could also try and find a mechanic with a tailpipe sniffer to see what the compounds in your engine's exhaust pipe are. My guess is that a lot of the engines intake charge is either being blocked by a reflected wave or being over scavenged by that wave. With math calculations that would make my head hurt you could also determine when that wave arrives relative to the crankshaft rotation and valve timing.

Rick



-- 

“Blessed are the cracked, for they shall let in the light.”   Groucho Marx

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rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Wed Nov 21, 2018 8:02 am Post subject: HKS Exhaust

Here's the original post;"We contacted HKS in Japan about exhaust system requirements and received a reply back from an HKS engineer. He said the headers need to merge at 500mm for proper scavenging and the length after the merge was not critical though he noted that installations with excessively long pipes after the merge had experienced rough idling issues. As far as individual headers with no merge, there was an HKS on a Skyraider at OshKosh years ago that had independent headers going to super trapp mufflers. They had a difficult time getting the engine to run well and it was way off on power. Jim routed my exhaust tubes to merge as close to 500mm as room would allow in the cowling and my engine runs fantastic. Right after the merge he rolled a simple muffler can with no baffles and its pretty quiet."

Rick

On Wed, Nov 21, 2018 at 7:46 AM Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:



 	  Quote: 	
		  Bill, Something got me thinking last night after I wrote to you about my experience with props on a completely non prop notion. I went digging in my HKS file and found what I was looking for.Measure your exhaust from exhaust port to the join (collector) of the two pipes. This distance should be 500 mm (~19.68"). If it's more or less than that there's your problem. This distance was shared by the HKS importer with a fellow on the HKS forum. Contact Mark Bierle at Earth Aircraft for advice, too. He's done a lot of research into HKS exhaust pipes working correctly. You could also try and find a mechanic with a tailpipe sniffer to see what the compounds in your engine's exhaust pipe are. My guess is that a lot of the engines intake charge is either being blocked by a reflected wave or being over scavenged by that wave. With math calculations that would make my head hurt you could also determine when that wave arrives relative to the crankshaft rotation and valve timing.

Rick



-- 

“Blessed are the cracked, for they shall let in the light.”   Groucho Marx

 	


-- 

“Blessed are the cracked, for they shall let in the light.”   Groucho Marx

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The smallest miracle right in front of you is enough to make you happy....

victorbravo(at)sbcglobal.
Guest

Posted: Wed Nov 21, 2018 9:56 am Post subject: HKS Exhaust

Well, now Rick we may be on to something. Jerry Olenik sent me an e-mail a coupld of years ago that said he THOUGHT he remembered the distance should be 24 inches, and that is what we built my exhaust to. I will measure it again today to be sure that it is 24 inches. 



The whole "exhaust thing" with me started because I could not install the stock OEM system on my Kolb without it hitting the wings as they fold.Otherwise I would have installed the OEM system and been done with it years ago.



Bill Berle

www.ezflaphandle.com  - safety & performance upgrade for light aircraft

www.grantstar.net           - winning proposals for non-profit and for-profit entities



--------------------------------------------

On Wed, 11/21/18, Richard Girard <aslsa.rng(at)gmail.com> wrote:



 Subject: Re: HKS Exhaust

 To: "kolb-list(at)matronics.com" <kolb-list(at)matronics.com>

 Date: Wednesday, November 21, 2018, 8:00 AM

 

 Here's

 the original post;"We

 contacted HKS in Japan about exhaust system requirements and

 received a reply back from an HKS engineer. He said the

 headers need to merge at 500mm for proper scavenging and the

 length after the merge was not critical though he noted that

 installations with excessively long pipes after the merge

 had experienced rough idling issues. As far as individual

 headers with no merge, there was an HKS on a Skyraider at

 OshKosh years ago that had independent headers going to

 super trapp mufflers. They had a difficult time getting the

 engine to run well and it was way off on power. Jim routed

 my exhaust tubes to merge as close to 500mm as room would

 allow in the cowling and my engine runs fantastic. Right

 after the merge he rolled a simple muffler can with no

 baffles and its pretty quiet."

 Rick

 

 On Wed, Nov

 21, 2018 at 7:46 AM Richard Girard <aslsa.rng(at)gmail.com>

 wrote:

 Bill, Something got me thinking last night after I

 wrote to you about my experience with props on a completely

 non prop notion. I went digging in my HKS file and found

 what I was looking for.Measure your exhaust from

 exhaust port to the join (collector) of the two pipes. This

 distance should be 500 mm (~19.68"). If it's more

 or less than that there's your problem. This distance

 was shared by the HKS importer with a fellow on the HKS

 forum. Contact Mark Bierle at Earth Aircraft for advice,

 too. He's done a lot of research into HKS exhaust pipes

 working correctly. You could also try and find a mechanic

 with a tailpipe sniffer to see what the compounds in your

 engine's exhaust pipe are. My guess is that a lot of the

 engines intake charge is either being blocked by a reflected

 wave or being over scavenged by that wave. With math

 calculations that would make my head hurt you could also

 determine when that wave arrives relative to the crankshaft

 rotation and valve timing.

 Rick

 

 -- 

 “Blessed are

 the cracked, for they shall let in the light.”   Groucho

 Marx

 

 

 

 -- 

 “Blessed are

 the cracked, for they shall let in the light.”   Groucho

 Marx

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Richard Pike

Joined: 09 Jan 2006
Posts: 1671
Location: Blountville, Tennessee

Posted: Wed Nov 21, 2018 7:30 pm Post subject: Re: HKS Exhaust

The exhaust thing is pretty important. When I modified the exhaust on the 277 for the FF, I found a tapered cone from a hot rod shop that allowed me to approximate the distance/taper described in an old LEAF catalog for the 277 exhaust. So I made it to what I thought was the right length.

Makes good power, but it will not settle down at a constant throttle setting between 4700 and 5300 rpm. it will slowly speed up or slow down, but never constant. David redid all the math and the taper was perfect but I had made it 9/8" too long. Duh.

Another project. Be redoing it soon. 

But yeah - I think you may have hit on something.

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_________________
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing.

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