Scavenger Exhaust
05-12-2017, 12:28 PM
#11
I am running the Gernzhaust with a supercharger (375 WHP at 8k on AP1). I think in theory supercharger can benefit from exhaust scavenging, although on my tune we we'ren't able to bring vtec below 5.4k because of a resonance spike, so the results suggest that perhaps it wasn't the best idea.
But, as for as turbo theory goes, you don't want any backpressure whatsoever behind the turbo. SO, it doesn't make a lot of sense to have an exhaust behind the turbo which improves scavenging (it does so at the cost of some backpressure)
Anyone with some more knowledge want to chime in?
But, as for as turbo theory goes, you don't want any backpressure whatsoever behind the turbo. SO, it doesn't make a lot of sense to have an exhaust behind the turbo which improves scavenging (it does so at the cost of some backpressure)
Anyone with some more knowledge want to chime in?
Introducing scavenging though I would still look for it by finding the best straight through diameter piping, and a tapered collector/test pipe. Not a 2k exhaust with a catylitic converter.
I'm not saying your wrong by any means here, more agreeing with you and chiming in on addition to your SC setup.
Last edited by MorngWoodStewie; 05-12-2017 at 12:30 PM.
05-12-2017, 01:05 PM
#12
I think SC are just safer with converters because there are no real threats to it because of back pressure creating higher egts like on a TC.
Introducing scavenging though I would still look for it by finding the best straight through diameter piping, and a tapered collector/test pipe. Not a 2k exhaust with a catylitic converter.
I'm not saying your wrong by any means here, more agreeing with you and chiming in on addition to your SC setup.
Introducing scavenging though I would still look for it by finding the best straight through diameter piping, and a tapered collector/test pipe. Not a 2k exhaust with a catylitic converter.
I'm not saying your wrong by any means here, more agreeing with you and chiming in on addition to your SC setup.
05-21-2017, 08:50 AM
#13
This is Gernby's comment on exactly this topic:
https://www.s2ki.com/forums/sponsor-...991992/page14/
"The issue with SC applications really doesn't have anything to do with the exhaust, per se'. The issue has to do with the stock cams and cam timing. Once VTEC engages, there is so much valve overlap that the SC will push fresh air and fuel straight through the chamber during that short time that the intake valves and exhaust valves are both open simultaneously.
The correct fix for that would be different cams and / or adjustable cam gears, in order to reduce overlap. If you solve that problem, then my exhaust would be great for it. Without that solution, the exhaust needs to be somewhat restrictive, so that you waste less boost and fuel.
That said, I do think my mid-pipe would work better on an SC application than a 3" exhaust with a test pipe. I think a 3" exhaust with test pipe is the absolute worst setup for an SC, since it provides very little scavenging at low RPMs (when boost is low), and provides TONS of over-scavenging at high RPMs (when boost is high). This is the worst scenario possible for an SC."
https://www.s2ki.com/forums/sponsor-...991992/page14/
"The issue with SC applications really doesn't have anything to do with the exhaust, per se'. The issue has to do with the stock cams and cam timing. Once VTEC engages, there is so much valve overlap that the SC will push fresh air and fuel straight through the chamber during that short time that the intake valves and exhaust valves are both open simultaneously.
The correct fix for that would be different cams and / or adjustable cam gears, in order to reduce overlap. If you solve that problem, then my exhaust would be great for it. Without that solution, the exhaust needs to be somewhat restrictive, so that you waste less boost and fuel.
That said, I do think my mid-pipe would work better on an SC application than a 3" exhaust with a test pipe. I think a 3" exhaust with test pipe is the absolute worst setup for an SC, since it provides very little scavenging at low RPMs (when boost is low), and provides TONS of over-scavenging at high RPMs (when boost is high). This is the worst scenario possible for an SC."
Last edited by Sophotrope; 05-21-2017 at 08:56 AM.
05-21-2017, 09:59 PM
#14
A complete exhaustion of last cycle, and a complete new 100% air n fuel in the chamber sounds good to me. Saying the overlap ends up pushing actual clean clear intake is what it's suppose to do. Just because some new cycle pushes past does not mean it doesn't get a complete fill of it's chamber. Thats what scavenging is suppose to do.
A SC usually highlights the low to mid range, so if u can get air to pass freely "easier" by the compressor it will in essence act like an open down pipe.
In addition having spent gasses in the combustion cycle is not efficient. I have not read the link but I'm sure he is not arguing this fact, it's just the bottom line. Scavenging helps top end performance by getting a head start to reduce spent gasses in cylinder and getting a ram effect of new clean air n fuel.
Most Importantly it's all about what u want. Reducing the over lap will move the area under the curve to the left. If that's what u want or need, reduce it. But don't think your gonna reduce the overlap and make consistent higher peak #'s or outshine the entire graph completely. It's all about application and what you want. Don't go against the grain and expect it to make higher whp.
Read up on valve and cam timing if you don't know what I'm talking about, it's all here.
A SC usually highlights the low to mid range, so if u can get air to pass freely "easier" by the compressor it will in essence act like an open down pipe.
In addition having spent gasses in the combustion cycle is not efficient. I have not read the link but I'm sure he is not arguing this fact, it's just the bottom line. Scavenging helps top end performance by getting a head start to reduce spent gasses in cylinder and getting a ram effect of new clean air n fuel.
Most Importantly it's all about what u want. Reducing the over lap will move the area under the curve to the left. If that's what u want or need, reduce it. But don't think your gonna reduce the overlap and make consistent higher peak #'s or outshine the entire graph completely. It's all about application and what you want. Don't go against the grain and expect it to make higher whp.
Read up on valve and cam timing if you don't know what I'm talking about, it's all here.
Last edited by MorngWoodStewie; 05-21-2017 at 11:22 PM.
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