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GreenSquirrel 10-17-2015 01:30 AM

Exhaust valves
 
There is some merit to this although it's effect on mileage has yet to be credibly tested but here it is; exhaust valves create backpressure at low RPM's (when the engine is cycling smaller volumes of exhaust per minute) but open to allow full use of the cavernous exhaust pipe, it allows the engine to get a small bump in hp lower in the rev range, my question is has anybody tried exhaust valves to nurse the engine during acceleration at lower speeds for the purposes of mileage/fuel-conservation? I intend to give this a go on my next vehicle but would like to know what others know/have experienced about this subject.

aerohead 10-17-2015 04:12 PM

exhaust valves
 
Quote:

Originally Posted by GreenSquirrel (Post 496748)
There is some merit to this although it's effect on mileage has yet to be credibly tested but here it is; exhaust valves create backpressure at low RPM's (when the engine is cycling smaller volumes of exhaust per minute) but open to allow full use of the cavernous exhaust pipe, it allows the engine to get a small bump in hp lower in the rev range, my question is has anybody tried exhaust valves to nurse the engine during acceleration at lower speeds for the purposes of mileage/fuel-conservation? I intend to give this a go on my next vehicle but would like to know what others know/have experienced about this subject.

At least one production motorcycle incorporated a 'smart' muffler which had a computer-controlled butterfly valve inside.
The motorcycle engine underwent a full-spectrum dynamometer test to evaluate it's best performance at all rpm's as a function of exhaust back-pressure,then a look-up menu was burned into the ROM chip which allowed the computer to modulate a servo motor linked to the muffler's valve; enabling the engine to always remain in the sweet-spot.
If you've got a loose $100,000 you want to throw at a chassis dyno,you'd be able to do this to your car.:p

RustyLugNut 10-17-2015 04:35 PM

Or you can use in-cylinder pressure sensors.
 
Quote:

Originally Posted by aerohead (Post 496793)
At least one production motorcycle incorporated a 'smart' muffler which had a computer-controlled butterfly valve inside.
The motorcycle engine underwent a full-spectrum dynamometer test to evaluate it's best performance at all rpm's as a function of exhaust back-pressure,then a look-up menu was burned into the ROM chip which allowed the computer to modulate a servo motor linked to the muffler's valve; enabling the engine to always remain in the sweet-spot.
If you've got a loose $100,000 you want to throw at a chassis dyno,you'd be able to do this to your car.:p

For roughly 10,000 USD, you can purchase an array of pressure sensing spark plugs and the attendant data logging. A set of well thought out acceleration runs will get you most of what you desire.

If you are doing a single cylinder engine, you can purchase the sensing spark plug for about $1K and cludge your own data logger using slower commonly available electronics and do multiple cycle overlays.

But, that's just what I would do.

niky 10-18-2015 10:02 PM

You could actually do the same thing with a piggyback chip like the UniChip-Q, to which you can add auxiliary maps to precisely control things like extra injectors, nitrous and even a flapper valve.

Just tune it once on the dyno, you're done.

Daschicken 10-21-2015 04:10 PM

Quote:

Originally Posted by aerohead (Post 496793)
At least one production motorcycle incorporated a 'smart' muffler which had a computer-controlled butterfly valve inside.
The motorcycle engine underwent a full-spectrum dynamometer test to evaluate it's best performance at all rpm's as a function of exhaust back-pressure,then a look-up menu was burned into the ROM chip which allowed the computer to modulate a servo motor linked to the muffler's valve; enabling the engine to always remain in the sweet-spot.
If you've got a loose $100,000 you want to throw at a chassis dyno,you'd be able to do this to your car.:p

My grandpa's 1999 yamaha r1 had an exhaust butterfly valve, but I doubt it was computer controlled as the thing had carbs. Although it did have a MIL system that had codes for the exhaust valve, so it could be.

aerohead 10-21-2015 04:59 PM

in-cylinder sensor
 
Quote:

Originally Posted by RustyLugNut (Post 496795)
For roughly 10,000 USD, you can purchase an array of pressure sensing spark plugs and the attendant data logging. A set of well thought out acceleration runs will get you most of what you desire.

If you are doing a single cylinder engine, you can purchase the sensing spark plug for about $1K and cludge your own data logger using slower commonly available electronics and do multiple cycle overlays.

But, that's just what I would do.

The thing about the dyno though,is that you can get BSFC data as you go,which is of great importance,and a dyno's the only place to scientifically acquire the data directly that I'm aware of.

RustyLugNut 10-21-2015 06:28 PM

On-road data collection.
 
Quote:

Originally Posted by aerohead (Post 497222)
The thing about the dyno though,is that you can get BSFC data as you go,which is of great importance,and a dyno's the only place to scientifically acquire the data directly that I'm aware of.

It is used daily in industry. Lay people see it as "unscientific and variable". Granted, the lab dyno does allow control of certain variables, however, in the case of exhaust back pressure versus load and fuel use, all one needs is a set of accurately mapped fuel injectors/pump for fuel flow and an in-cylinder pressure sensor to see power potential as well as an exhaust pressure sensor and position sensor on your exhaust backpressure valve.

A baseline run followed by a set exhaust valve run yields a pair of pressure traces that allow you to determine a gain or loss. No need to calculate BSFC as combustion pressure is all the feedback you need. A pair of runs takes 5 minutes or less. A well thought out set of runs can yield a reasonably extrapolated pressure map with which to program an engine map.

Again, there is no need to carry the burden of a dyno cell instrument set. In-cylinder pressure will tell you if the exhaust back pressure is beneficial or detrimental. I would probably add a stepper actuator to the exhaust back pressure valve to make "fanning" the back pressure during runs possible. This reduces the number of runs during your data gathering.

gone-ot 10-21-2015 09:09 PM

...or, you can buy software programs that simulate just about 100%-functions of an engine in operation...at any load...under any weather conditions.

RustyLugNut 10-21-2015 09:20 PM

This.
 
Quote:

Originally Posted by Old Tele man (Post 497241)
...or, you can buy software programs that simulate just about 100%-functions of an engine in operation...at any load...under any weather conditions.

None of the software programs found at your corner bookstore will be able to do the job, but there are several commercially available programs that would allow you to do most of your ballpark work. Of course, there is the issue of computational power. Some titles need a Cray class computer to run on, while others can run on lesser mainframes or desktops though with very slow results. And in the end, you must vet your model with actual data.

Xist 10-22-2015 03:20 AM

Aerohead, do you remember approximately what kind of a difference that setup made for that motorcycle?

markweatherill 10-22-2015 06:09 AM

I seem to recall a JDM aftermarket device which had a vacuum controlled butterfly valve. Or it might have been electronically controlled. It was made by HKS or some such. I could imagine the severe environment of an exhaust pipe causing problems for such a device.

darcane 10-22-2015 03:01 PM

Quote:

Originally Posted by Daschicken (Post 497214)
My grandpa's 1999 yamaha r1 had an exhaust butterfly valve, but I doubt it was computer controlled as the thing had carbs. Although it did have a MIL system that had codes for the exhaust valve, so it could be.

This is Yamaha's EXUP system, and the computer module controls when the valve opens and closes. I have the same engine on my bike-engined-car project, and have to defeat the system in order to allow the engine to run properly even though it is carbureted.

It's not entirely accurate to say this system increases backpressure. The header should be tuned for optimal scavenging at whatever RPM peak torque is made at. Restricting the exhaust adjusts the exhaust pulses to better scavenge at low RPMs. This actually reduces backpressure at the exhaust valve when the exhaust valve opens.

For a dedicated economy car, rather than try to replicate this complex exhaust valve system, you'd be better off designing a header that is tuned for running at low RPMs. That would be cheaper and far easier to accomplish, and likely more effective. Although, I doubt you will see measureable gains over the stock exhaust.

GreenSquirrel 11-13-2015 11:21 PM

Some of the latest gen Corvette's (C7) have butterfly valves in the exhaust, the Ferrari 458 has an additional exhaust chamber that is opened at full chat. I also thought of a dilating cone type valve like on the exhaust of a fighter jet, very exotic and would need to be designed properly so as not to jam up from road crud, but I have been tooling with metal from soda cans to create a prototype, seems feasible using a simple cable linkage and return spring.

cRiPpLe_rOoStEr 11-14-2015 03:32 AM

In motorcycles those "power valves" were meant to improve the low-end torque, but nowadays with dual-VVT becoming widespread they would become likely redundant.

aerohead 11-25-2015 05:13 PM

dilating cone
 
Quote:

Originally Posted by GreenSquirrel (Post 499360)
Some of the latest gen Corvette's (C7) have butterfly valves in the exhaust, the Ferrari 458 has an additional exhaust chamber that is opened at full chat. I also thought of a dilating cone type valve like on the exhaust of a fighter jet, very exotic and would need to be designed properly so as not to jam up from road crud, but I have been tooling with metal from soda cans to create a prototype, seems feasible using a simple cable linkage and return spring.

Check out this link.It's for the Me 262,Junkers JUMO 004 turbojet tailpipe bullet valve.These are also used in Pelton Wheel turbine water jets.
They're the most fluid dynamically efficient restriction valving I've ever seen and basis for the grille block on my truck.
http://greyfalcon.us/jumo.jpg

ConnClark 11-27-2015 10:09 PM

Quote:

Originally Posted by Old Tele man (Post 497241)
...or, you can buy software programs that simulate just about 100%-functions of an engine in operation...at any load...under any weather conditions.


You can get software like that for free. You just need a PHD to figure how to use it.

Its called OpenFOAM

aerohead 11-28-2015 02:53 PM

pressure
 
Quote:

Originally Posted by RustyLugNut (Post 497230)
It is used daily in industry. Lay people see it as "unscientific and variable". Granted, the lab dyno does allow control of certain variables, however, in the case of exhaust back pressure versus load and fuel use, all one needs is a set of accurately mapped fuel injectors/pump for fuel flow and an in-cylinder pressure sensor to see power potential as well as an exhaust pressure sensor and position sensor on your exhaust backpressure valve.

A baseline run followed by a set exhaust valve run yields a pair of pressure traces that allow you to determine a gain or loss. No need to calculate BSFC as combustion pressure is all the feedback you need. A pair of runs takes 5 minutes or less. A well thought out set of runs can yield a reasonably extrapolated pressure map with which to program an engine map.

Again, there is no need to carry the burden of a dyno cell instrument set. In-cylinder pressure will tell you if the exhaust back pressure is beneficial or detrimental. I would probably add a stepper actuator to the exhaust back pressure valve to make "fanning" the back pressure during runs possible. This reduces the number of runs during your data gathering.

Yes,it looks like BSFC mirrors torque,which mirrors Mean Effective Pressure,which mirrors the Unit Air Charge.
As long as the before and after runs were done at a constant 'atmosphere',or corrected to a standard atmosphere,it would be really useful data.Thanks!:)

aerohead 11-28-2015 03:03 PM

difference
 
Quote:

Originally Posted by Xist (Post 497271)
Aerohead, do you remember approximately what kind of a difference that setup made for that motorcycle?

Here is the engine map for the YAMAHA EXUP system.You can see how the torque profile is flattened
http://i1271.photobucket.com/albums/...itled-13_1.jpg
*I have a HONDA MC exhaust with valving,but just a butterfly valve,nothing as exotic as YAMAHA.
*Walker has been offering a passive/active,Dyno Max VT,valved exhaust since around 2011.
* The new Corvette Sting ray comes standard with a butterfly-valved,DUAL MODE exhaust that's good for 5-bhp.
*Camaro SS has a $895 Dual Mode option.
*I think Ferrari is doing it too,they talk of 'opening baffles'.
*Dinan High Performance Exhaust offers a butterfly-valved exhaust system for the BMW M5.
*Ford offers manually-removable exhaust inserts for their MUSTANG Boss 302,to make the exhaust louder.
PS,the Yamaha EXUP Patent would have expired in 2008?

cRiPpLe_rOoStEr 12-14-2015 02:35 AM

Quote:

Originally Posted by aerohead (Post 500748)
the Yamaha EXUP Patent would have expired in 2008?

Since exhaust-brakes have been around in Diesel trucks for a long time, and their position inside the exhaust system is similar, even though their functions are different, I wouldn't really care about Yamaha and its patents :thumbup:


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