Restricted exhaust

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RCJ
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Restricted exhaust

Post by RCJ » Sun Dec 10, 2017 8:47 pm

If rules dictated a small primary pipe diameter and a restrictive muffler.Would you make the exhaust system as short as feasible.

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Re: Restricted exhaust

Post by ptuomov » Sun Dec 10, 2017 8:53 pm

RCJ wrote:
Sun Dec 10, 2017 8:47 pm
If rules dictated a small primary pipe diameter and a restrictive muffler.Would you make the exhaust system as short as feasible.
I wouldn’t, assuming it’s a V8.

I would make the small diameter primaries very short but then pair 4-2-1 and Y pipe go much bigger for secondaries and all the other exhaust pipes. 4-2-1 allows you to avoid both 90 degree and 180 degree exhaust blowdown interference with very short primaries. What restrictions do you have on the length and style of the headers?

Then I’d run the muffler all the way at the rear bumper after exhaust gas has cooled and all the pulses have been combined. The key is to cool the exhaust with minimum restriction before the muffler, how about running aluminum exhaust pipes to maximize cooling?
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Restricted exhaust

Post by Curtis Mc » Sun Dec 10, 2017 9:55 pm

Is this a theoretical question or are there specific rules you can point to? You may get all sorts of ideas if people can see the rules as written.

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Re: Restricted exhaust

Post by RCJ » Mon Dec 11, 2017 8:11 am

This is for my grandson's racing kart.4 stroke single ,79cc.Exhaust port is .900 dia., pipe inside dia. .625.I've raised the pipe to the top of the port and made a thick flange that I can blend.Pipe is 8'' long with a 90 degree bend off the head, can get to 20'' with no more bends.Any longer and I would have to add bends.

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Re: Restricted exhaust

Post by englertracing » Mon Dec 11, 2017 9:35 am

What's the muffler?

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Re: Restricted exhaust

Post by ptuomov » Mon Dec 11, 2017 9:41 am

RCJ wrote:
Mon Dec 11, 2017 8:11 am
This is for my grandson's racing kart.4 stroke single ,79cc.Exhaust port is .900 dia., pipe inside dia. .625.I've raised the pipe to the top of the port and made a thick flange that I can blend.Pipe is 8'' long with a 90 degree bend off the head, can get to 20'' with no more bends.Any longer and I would have to add bends.
Does the entire pipe between the port and the muffler have to be .625" inside diameter? Or does only the first 8" have to be .625" ID?

Is there a restriction on how thick the flange can be?

How much CFM does the muffler flow and at what test pressure?
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Restricted exhaust

Post by RCJ » Mon Dec 11, 2017 10:35 am

The pipe has to be .625 all the way to the muffler.Here is a link to the muffler.I can remove the internals from the muffler.

https://www.bmikarts.com/RLV-Mini-91-Mu ... _p_36.html

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Re: Restricted exhaust

Post by ptuomov » Mon Dec 11, 2017 10:46 am

RCJ wrote:
Mon Dec 11, 2017 10:35 am
The pipe has to be .625 all the way to the muffler.Here is a link to the muffler.I can remove the internals from the muffler.

https://www.bmikarts.com/RLV-Mini-91-Mu ... _p_36.html
Are you allowed to extend the pipe after the muffler?

What I'm thinking is gutting that silencer and making it effectively "a step" in the exhaust primary. Then extending at the appropriate size pipe from the silencer. One idea could be to set the length of the .625" primary such that when the blowdown wave hits the step, it reflects a low pressure wave back to the cylinder that is timed such that the exhaust valve seat is no longer close to sonic velocity. Then the longer bigger pipe downstream of the "silencer step" is timed to send back a low pressure wave around the overlap. If this would be legal, that is, putting a gutted silencer between the small primary and large "secondary", it might make some sense to model and/or test it.

Just throwing out ideas here, I've obviously never done anything like this.
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Restricted exhaust

Post by Curtis Mc » Mon Dec 11, 2017 12:40 pm

Do the rules state you can't have two mufflers? Something like a "Y" at the end of the appropriate blow-down length?

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Re: Restricted exhaust

Post by Ron E » Mon Dec 11, 2017 3:20 pm

Is this a OHV engine, or a flathead?

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Re: Restricted exhaust

Post by RCJ » Mon Dec 11, 2017 4:43 pm

OHV.

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Re: Restricted exhaust

Post by pamotorman » Mon Dec 11, 2017 5:24 pm

RCJ wrote:
Mon Dec 11, 2017 8:11 am
This is for my grandson's racing kart.4 stroke single ,79cc.Exhaust port is .900 dia., pipe inside dia. .625.I've raised the pipe to the top of the port and made a thick flange that I can blend.Pipe is 8'' long with a 90 degree bend off the head, can get to 20'' with no more bends.Any longer and I would have to add bends.
the 90 degree bend would hurt the flow. if you want length form the pipe in a big radius

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Re: Restricted exhaust

Post by cjperformance » Mon Dec 11, 2017 6:05 pm

ptuomov wrote:
Mon Dec 11, 2017 10:46 am
RCJ wrote:
Mon Dec 11, 2017 10:35 am
The pipe has to be .625 all the way to the muffler.Here is a link to the muffler.I can remove the internals from the muffler.

https://www.bmikarts.com/RLV-Mini-91-Mu ... _p_36.html
Are you allowed to extend the pipe after the muffler?

What I'm thinking is gutting that silencer and making it effectively "a step" in the exhaust primary. Then extending at the appropriate size pipe from the silencer. One idea could be to set the length of the .625" primary such that when the blowdown wave hits the step, it reflects a low pressure wave back to the cylinder that is timed such that the exhaust valve seat is no longer close to sonic velocity. Then the longer bigger pipe downstream of the "silencer step" is timed to send back a low pressure wave around the overlap. If this would be legal, that is, putting a gutted silencer between the small primary and large "secondary", it might make some sense to model and/or test it.

Just throwing out ideas here, I've obviously never done anything like this.
I like that idea, whether its legal or not is another thing :D
Craig.

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Re: Restricted exhaust

Post by ptuomov » Mon Dec 11, 2017 6:07 pm

cjperformance wrote:
Mon Dec 11, 2017 6:05 pm
ptuomov wrote:
Mon Dec 11, 2017 10:46 am
RCJ wrote:
Mon Dec 11, 2017 10:35 am
The pipe has to be .625 all the way to the muffler.Here is a link to the muffler.I can remove the internals from the muffler.

https://www.bmikarts.com/RLV-Mini-91-Mu ... _p_36.html
Are you allowed to extend the pipe after the muffler?

What I'm thinking is gutting that silencer and making it effectively "a step" in the exhaust primary. Then extending at the appropriate size pipe from the silencer. One idea could be to set the length of the .625" primary such that when the blowdown wave hits the step, it reflects a low pressure wave back to the cylinder that is timed such that the exhaust valve seat is no longer close to sonic velocity. Then the longer bigger pipe downstream of the "silencer step" is timed to send back a low pressure wave around the overlap. If this would be legal, that is, putting a gutted silencer between the small primary and large "secondary", it might make some sense to model and/or test it.

Just throwing out ideas here, I've obviously never done anything like this.
I like that idea, whether its legal or not is another thing :D
Everyone likes a barely legal idea, right? Me too! ;-)
[b]Paradigms often shift without the clutch[/b] -- [url]https://www.youtube.com/watch?v=cxn-LxwsrnU[/url]

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Re: Restricted exhaust

Post by cjperformance » Mon Dec 11, 2017 6:18 pm

:lol: yep they are always the best ideas
Craig.

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