With highly tuned 2 valve motorcycle engines ,reversion is generally a problem and will cause actual rich misfire at midrange RPM...The short stub pipe that protrudes into the primary pipe woks pretty well...cjperformance wrote: ↑Tue Nov 14, 2017 7:00 pm A couple of ideas if room is very tight,,,
Very short stub pipes from each cylinder that protrude into a tapering log manifold
How to fight exhaust reversion when the primaries are way too short
Moderator: Team
Re: How to fight exhaust reversion when the primaries are way too short
Motorcycle land speed racing... wearing animal hides and clinging to vibrating oily machines propelled by fire
Re: How to fight exhaust reversion when the primaries are way too short
I played with two-stroke engines when younger. (Was wrong about most things back then, and the things that I was right about I don't remember any more.) Doesn't that hurt the torque at the tuned rpms?Truckedup wrote: ↑Wed Nov 15, 2017 6:24 amWith highly tuned 2 valve motorcycle engines ,reversion is generally a problem and will cause actual rich misfire at midrange RPM...The short stub pipe that protrudes into the primary pipe woks pretty well...cjperformance wrote: ↑Tue Nov 14, 2017 7:00 pm A couple of ideas if room is very tight,,,
Very short stub pipes from each cylinder that protrude into a tapering log manifold
In this case of four-stroke cross-plane log exhaust manifold, would you put such protruding pipe in the offending cylinder #3 or the victim cylinder #1 or both?
The problem with this manifold as far as I can tell is that the pressure pulse moves so much faster than the flow starts going. It's very difficult to control the pressure pulse with flow because the flow just gradually gets going when the pressure pulse has already done its thing. If there's no stopping of that pressure pulse from #3, the second best thing is to get it done and over with as early in the exhaust stroke of #1 as possible. Now how to do that?
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
https://www.instagram.com/ptuomov/
Put Search Keywords Here
Re: How to fight exhaust reversion when the primaries are way too short
I really don't know because I don't use it on my race bikes...My bike holds the class speed record (land speed racing), the competition uses all sorts of tuned exhaust and intakes. My bike has the carbs close to the head as possible and two 34 inch straight exhaust pipes...So I have to figure all the tuned lengths don't matter on a 360 degree twin cylinder engine where maximum speed is importantptuomov wrote: ↑Wed Nov 15, 2017 8:15 amI played with two-stroke engines when younger. (Was wrong about most things back then, and the things that I was right about I don't remember any more.) Doesn't that hurt the torque at the tuned rpms?Truckedup wrote: ↑Wed Nov 15, 2017 6:24 amWith highly tuned 2 valve motorcycle engines ,reversion is generally a problem and will cause actual rich misfire at midrange RPM...The short stub pipe that protrudes into the primary pipe woks pretty well...cjperformance wrote: ↑Tue Nov 14, 2017 7:00 pm A couple of ideas if room is very tight,,,
Very short stub pipes from each cylinder that protrude into a tapering log manifold
Motorcycle land speed racing... wearing animal hides and clinging to vibrating oily machines propelled by fire
Re: How to fight exhaust reversion when the primaries are way too short
Sorry I misread two valve as two stroke...
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
https://www.instagram.com/ptuomov/
Put Search Keywords Here
Re: How to fight exhaust reversion when the primaries are way too short
Just brainstorming atypical ideas... Quarter wavelength resonator for the #3 at the frequency it begins to impact #1. Might be in the ballpark of manifold length at high rpm.
Re: How to fight exhaust reversion when the primaries are way too short
A resonator tube is going to reflect a positive pressure wave back to #1 and #3. How do you reflect a negative wave to #1 in that manifold? (I've got a turbine corking the manifold outlet.)
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
https://www.instagram.com/ptuomov/
Put Search Keywords Here
Re: How to fight exhaust reversion when the primaries are way too short
Run the turbo on 3cyls?
Pipe the odd one past the turbo, or to the other side?
Strategic wastegate placement?
Pipe the odd one past the turbo, or to the other side?
Strategic wastegate placement?
Re: How to fight exhaust reversion when the primaries are way too short
Brabus had at least a prototype of a turbo exhaust manifold that bypassed one cylinder to remove 90-degree exhaust blowdown interference.
There's no room for me to get a pipe past the turbos. Even the wastegate pipe must be integrated to the turbine housing to fit. So that's a "no go" for a number of reasons.
You do not have the required permissions to view the files attached to this post.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
https://www.instagram.com/ptuomov/
Put Search Keywords Here
-
- Guru
- Posts: 3661
- Joined: Tue Aug 19, 2008 7:20 am
- Location: South Australia
Re: How to fight exhaust reversion when the primaries are way too short
Just pop a flat plane crank in it!
Craig.
Re: How to fight exhaust reversion when the primaries are way too short
Do the heads have a crossover to heat the intake?
Re: How to fight exhaust reversion when the primaries are way too short
No. Fuel injected, four valve heads, nothing like that.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
https://www.instagram.com/ptuomov/
Put Search Keywords Here
Re: How to fight exhaust reversion when the primaries are way too short
ptuomov wrote: ↑Wed Nov 15, 2017 8:24 pmBrabus had at least a prototype of a turbo exhaust manifold that bypassed one cylinder to remove 90-degree exhaust blowdown interference.
brabus_biturbo_v8_exhaustthumb717x537998-1.jpg
There's no room for me to get a pipe past the turbos. Even the wastegate pipe must be integrated to the turbine housing to fit. So that's a "no go" for a number of reasons.
Well that's never going to get past the prototype stage.....dumbest idea ever with different VE for one cylinder of the bank..
Re: How to fight exhaust reversion when the primaries are way too short
It may not get past it, but I'd say that almost all if not all cross-plane V8's that come from the factory assembly line have significant variation between the VE of different cylinders. Unless you have long-tube headers from factory (basically only BMW of the big guys does something like that), that's just what you're going to have.joe 90 wrote: ↑Wed Nov 15, 2017 11:56 pmptuomov wrote: ↑Wed Nov 15, 2017 8:24 pmBrabus had at least a prototype of a turbo exhaust manifold that bypassed one cylinder to remove 90-degree exhaust blowdown interference.
brabus_biturbo_v8_exhaustthumb717x537998-1.jpg
There's no room for me to get a pipe past the turbos. Even the wastegate pipe must be integrated to the turbine housing to fit. So that's a "no go" for a number of reasons.
Well that's never going to get past the prototype stage.....dumbest idea ever with different VE for one cylinder of the bank..
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
https://www.instagram.com/ptuomov/
Put Search Keywords Here
Re: How to fight exhaust reversion when the primaries are way too short
Maybe I’m way off, but wouldn’t 1/4 wavelength resonator connected to #3 be phase shifted to cancel out the wave action at the designed frequency. Of course, if the pressure in the manifold is higher than in #1, flow will still follow, but less in tune with that rpm. Thinking a dead end channel in the manifold.
Re: How to fight exhaust reversion when the primaries are way too short
It's my impression that in a logish manifold like this, each exhaust blowdown event is so violent that it effectively resets the whole system. Blowdown events happen as frequently as 400 times per second at 6000 rpm, since 90 degrees of crankshaft movement takes 1/(4*6000/60) = 0.0025 seconds. The speed of sound is of the order of 2000 ft/s in that temperature, so you have time to move about 5 feet (more in the direction of flow, much less against the flow) before the new "reset" pulse comes in 0.0025 seconds. I don't see how I could get a quarter-wave resonator to do anything beneficial in that sort of setting, can you sketch out your idea in more detail? Or have I misunderstood how it works?Calypso wrote: ↑Thu Nov 16, 2017 10:04 amMaybe I’m way off, but wouldn’t 1/4 wavelength resonator connected to #3 be phase shifted to cancel out the wave action at the designed frequency. Of course, if the pressure in the manifold is higher than in #1, flow will still follow, but less in tune with that rpm. Thinking a dead end channel in the manifold.
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
https://www.instagram.com/ptuomov/
Put Search Keywords Here
https://www.instagram.com/ptuomov/
Put Search Keywords Here