Variable Exhaust Geometry - Honda-Tech

Combustion Contraption · 12-04-2006, 11:34 PM

I think we are all familiar with variable intake geometry, most on this board in relation to the OE GSR intake manifold, so i wont have to explain that.

I guess the question im posing to those perhaps more experienced with this subject, is that why havent we seen much (any?) variable exhaust geometry? I read an interesting peice from one of Steve Matchett's books and while he was working as a mechanic for then Benneton-Renault, it was suspected that both Ferrari and McLaren were testing the idea, though they most likely never found any obvious benefit, as it didnt become 'the next big thing'. Though it is tough to quantify what F1 holds as 'the next big thing' because their 1% increase in HP might have been offset by the extra weight the system brought with it, and so on.

Anyway, just thinking out loud here...

JCushing · 12-05-2006, 06:05 AM

the infinity fx45 i belive (the infinity version of the murano) incorporates a variable geometry exhaust. some other pretty nifty stuff to to bump the power a bit compared to the murano.

D-Rob · 12-05-2006, 06:16 AM

Are we talking more about variable length, variable diameter, or a different path by itself for the exhaust?

Maybe the F1 engineers didn't see the benefit of targeting power at a certain RPM lower than what they were racing at, so the variable diameter exhaust idea got the boot?

- Derek

P.S., Combustion Contraption, did you recieve my PM?

Natural Aspirations · 12-05-2006, 07:24 AM

Doesnt the VW R32 do this already?

mgags7 · 12-05-2006, 07:44 AM

Randy Monroe was talking about this some time ago, talking about variable size collectors on headers....

I believe he was saying that the headers for jet ski race engines that he builds already use these "tunable" collectors and it shouldn't be long before they become available to us.....

I found a patent on one, but it sounds pretty simple, probably just one adjustable size "valve" that goes inline

http://www.freepatentsonline.com/6799423.html

b18bEKcoupe · 12-05-2006, 09:41 AM

I recently read about an australian lad who did extensive testing on variable back pressure on an NA engine. He conducted many expiriments and varied the ammount of back pressure. Every time that the back pressure was increased the power suffered.

black_EM1 · 12-05-2006, 09:50 AM

Is this anything like the new 7.0L Z06s? The mufflers have the equivalent of throttle bodies that open up for 0% restriction after a certain RPM(I think 3k), or under full-throttle conditions.

D-Rob · 12-05-2006, 09:56 AM

Quote:

Originally Posted by black_EM1

Is this anything like the new 7.0L Z06s? The mufflers have the equivalent of throttle bodies that open up for 0% restriction after a certain RPM(I think 3k), or under full-throttle conditions.

On the same note, didn't the DC5 ITR have the same kind of idea with the muffler design?

black_EM1 · 12-05-2006, 09:57 AM

Can't say off hand.

*goes to look it up*

JCushing · 12-05-2006, 10:00 AM

i belive the evo has something like that (valve in the muffler)

D-Rob · 12-05-2006, 10:02 AM

http://www.honda-tech.com/zerothread?id=1410979

DC5 ITR has a valve to quiet it down under low loads.

cjames235 · 12-05-2006, 10:12 AM

i wanted to do this type of thing with my car but not for performance reasons but rather for sound reasons.......... take a vacuum operated butterfly valve like alot of companies put in exhaust systems, cut the butterfly in half or 3/4 to allow exhaust to flow when closed and then at wot the valve opens all of the way up to allow it to flow well

revolt_allmotor · 12-05-2006, 10:50 AM

I believe most of the cars mentioned use the exhaust valves to help them pass government-mandated noise tests, rather than to help power or torque. Since the noise tests are conducted below a certain RPM, they can open the valve after that point and achieve the benefits of a more free-flowing exhaust (less backpressure).

In fact, this is something I've wondered about for a while. As a motorcycle journalists, I get these interesting tech briefings on the latest motorcycles, where engineers describe the technical features of the bike complete with illustrated powerpoint presentations. Several of the motorcycle companies use valves in the exhaust system. I think Yamaha started it with the EXUP system, and other companies have followed suit.

Some of the valves are located back at the muffler like the Z06, and others are in what we would probably call the midpipe. Some are even right at the collector, and the really cool ones change the flow configuration of the collector by directing air through it in a different way in different parts of the RPM range.

Pure speculation on my part, but I know that engines with big ports and big cams with lots of overlap (all designed to breathe at high RPM) typically make poor low-end power - I guess because the big ports don't have much velocity at lower RPM, and the overlap allows lots of blow-through, although I'm by no means an expert. Could adding more backpressure at lower RPM help reduce this problem? Exhaust guys, this one is for you!

blinx9900 · 12-05-2006, 12:06 PM

i too wondered about the motorcycle exhaust flap, my uneducated opinion is that it does indeed have more to do with sound than flow, however i believe it can be used for power aswell:

say you have a car with huge pipes... say a sohc civic with 3.5" exhaust, its going to take longer for the exhaust to reach the end of the pipe and exit the system, there may infact be a period (at lower revs) where the engine is strugling to push all this dead exhaust to the end and at that point it maybe loosing power as there is little to no velocity at this point, but put a 2" exhaust on the same car and exhaust travels a shorter path (dosent have to build up as much in smaller pipes), velocity increses sooner but yes at some point (higher revs) it will be restrictive... so i gueses you have to find a happy medium, perhaps the butterfly aids in this...

Jasper_db1 · 12-05-2006, 12:16 PM

Yamaha's EXUP

http://en.wikipedia.org/wiki/EXUP

Master of the Universe · 12-05-2006, 01:58 PM

There is a method of achieving variable tuning with out physically changing the pipe dimensions.

Combustion Contraption · 12-05-2006, 03:14 PM

I am aware that some OE manufacturers do this, but you dont see anything for the aftermarket high perf. aspect. Thats more of what i was getting at.

blinx9900 · 12-05-2006, 06:08 PM

perhaps the amount of R&D is too extensive... it would need some kind of monitering device plus electronic control... just a thought...

mgags7 · 12-05-2006, 06:19 PM

Quote:

Originally Posted by Don Lackey

There is a method of achieving variable tuning with out physically changing the pipe dimensions.

Well out with it then!

Combustion Contraption · 12-05-2006, 07:55 PM

Thats not roberts style.

Revolt, i have an interesting SAE paper regarding variable exhaust geometry written by some members of Honda's R&D staff. PM me if youre interested.

D-Rob, yeah i got your PM, good stuff! Glad everything got worked out for you.

Master of the Universe · 12-06-2006, 11:02 AM

It has to do with "fooling" the pressure waves in thinking that the pipe is longer. Hot gas molecules are dumb and can be readily fooled by some simple physics.

Natural Aspirations · 12-06-2006, 11:18 AM

Audio resonance?

alterdcreations · 12-06-2006, 11:31 AM

Quote:

Originally Posted by Don Lackey

It has to do with "fooling" the pressure waves in thinking that the pipe is longer. Hot gas molecules are dumb and can be readily fooled by some simple physics.

How would you fool gas molecules?
i know that header tape traps them inside of the pipe and increases the exhaust gas velocity it the tail pipe but how do you fool them?

12-04-2006, 11:34 PM	#1
Combustion Contraption Senior Member Join Date: Jan 2003 Location: So Cal Posts: 8,534	Variable Exhaust Geometry I think we are all familiar with variable intake geometry, most on this board in relation to the OE GSR intake manifold, so i wont have to explain that. I guess the question im posing to those perhaps more experienced with this subject, is that why havent we seen much (any?) variable exhaust geometry? I read an interesting peice from one of Steve Matchett's books and while he was working as a mechanic for then Benneton-Renault, it was suspected that both Ferrari and McLaren were testing the idea, though they most likely never found any obvious benefit, as it didnt become 'the next big thing'. Though it is tough to quantify what F1 holds as 'the next big thing' because their 1% increase in HP might have been offset by the extra weight the system brought with it, and so on. Anyway, just thinking out loud here... __________________ EARL LASKEY, YOU WILL BE MISSED CCCylinderheads.com Check out the INDUCTION SPECIAL Matco Doublebay Toolbox FOR SALE Click Here!

12-05-2006, 06:05 AM	#2
JCushing Senior Member Join Date: Nov 2001 Location: Suck it Trebek Posts: 3,115	Re: Variable Exhaust Geometry (Combustion Contraption) the infinity fx45 i belive (the infinity version of the murano) incorporates a variable geometry exhaust. some other pretty nifty stuff to to bump the power a bit compared to the murano. __________________ 84.5mm b20, 11.5:1 cr, non-vtec P8R head with crower 404's going to go bigger FOR MORE POWER! http://images.honda-tech.com/set1/smile/emsmileo.gif http://www.honda-tech.com/zerothread?id=1707713

12-05-2006, 06:16 AM	#3
D-Rob Senior Member Join Date: Aug 2004 Location: Carlisle, PA, USA Posts: 3,547	Re: Variable Exhaust Geometry (JCushing) Are we talking more about variable length, variable diameter, or a different path by itself for the exhaust? Maybe the F1 engineers didn't see the benefit of targeting power at a certain RPM lower than what they were racing at, so the variable diameter exhaust idea got the boot? - Derek P.S., Combustion Contraption, did you recieve my PM? __________________ InnovativeMotorWorks \| SURJE.motorsports \| Sound Innovations \| J-K-Tuning.com w w w . i n n o v a t i v e - m o t o r w o r k s . c o m

12-05-2006, 07:24 AM	#4
Natural Aspirations Senior Member Join Date: Jul 2004 Location: Bustin Balls in Central, Pa, usa Posts: 2,362	Doesnt the VW R32 do this already? __________________ I hear and I forget. I see and I remember. I do and I understand.

12-05-2006, 07:44 AM	#5
mgags7 Senior Member Join Date: Mar 2004 Location: Between headphones, NC Posts: 14,382	Randy Monroe was talking about this some time ago, talking about variable size collectors on headers.... I believe he was saying that the headers for jet ski race engines that he builds already use these "tunable" collectors and it shouldn't be long before they become available to us..... I found a patent on one, but it sounds pretty simple, probably just one adjustable size "valve" that goes inline http://www.freepatentsonline.com/6799423.html __________________ Matt ███

12-05-2006, 09:41 AM	#6
b18bEKcoupe Join Date: Jan 2004 Location: Madison, WI Posts: 429	I recently read about an australian lad who did extensive testing on variable back pressure on an NA engine. He conducted many expiriments and varied the ammount of back pressure. Every time that the back pressure was increased the power suffered.

12-05-2006, 09:50 AM	#7
black_EM1 Senior Member Join Date: Dec 2004 Location: www.Kills.com, ShutUpYouRetard Posts: 2,441	Re: (b18bEKcoupe) Is this anything like the new 7.0L Z06s? The mufflers have the equivalent of throttle bodies that open up for 0% restriction after a certain RPM(I think 3k), or under full-throttle conditions. __________________ -Charles- [ B00STED EM1 CREW #27] Kills Pirate. For Life. PeakBoost powered. 418hp/259tq@17psi PoorMan's R 336hp/223tq@15psi Bone Stock B18C

12-05-2006, 09:57 AM	#9
black_EM1 Senior Member Join Date: Dec 2004 Location: www.Kills.com, ShutUpYouRetard Posts: 2,441	Re: (D-Rob) Can't say off hand. goes to look it up __________________ -Charles- [ B00STED EM1 CREW #27] Kills Pirate. For Life. PeakBoost powered. 418hp/259tq@17psi PoorMan's R 336hp/223tq@15psi Bone Stock B18C

12-05-2006, 10:00 AM	#10
JCushing Senior Member Join Date: Nov 2001 Location: Suck it Trebek Posts: 3,115	Re: (black_EM1) i belive the evo has something like that (valve in the muffler) __________________ 84.5mm b20, 11.5:1 cr, non-vtec P8R head with crower 404's going to go bigger FOR MORE POWER! http://images.honda-tech.com/set1/smile/emsmileo.gif http://www.honda-tech.com/zerothread?id=1707713

12-05-2006, 10:02 AM	#11
D-Rob Senior Member Join Date: Aug 2004 Location: Carlisle, PA, USA Posts: 3,547	Re: (JCushing) http://www.honda-tech.com/zerothread?id=1410979 DC5 ITR has a valve to quiet it down under low loads. __________________ InnovativeMotorWorks \| SURJE.motorsports \| Sound Innovations \| J-K-Tuning.com w w w . i n n o v a t i v e - m o t o r w o r k s . c o m

12-05-2006, 10:12 AM	#12
cjames235 Senior Member Join Date: Oct 2001 Location: M Town, TN Posts: 1,661	Re: (b18bEKcoupe) i wanted to do this type of thing with my car but not for performance reasons but rather for sound reasons.......... take a vacuum operated butterfly valve like alot of companies put in exhaust systems, cut the butterfly in half or 3/4 to allow exhaust to flow when closed and then at wot the valve opens all of the way up to allow it to flow well __________________ ITR 98-0570 '07 919

12-05-2006, 10:50 AM	#13
revolt_allmotor Join Date: Apr 2004 Location: 909 all motor mafia,, CA, USA Posts: 4,521	Re: (JCushing) I believe most of the cars mentioned use the exhaust valves to help them pass government-mandated noise tests, rather than to help power or torque. Since the noise tests are conducted below a certain RPM, they can open the valve after that point and achieve the benefits of a more free-flowing exhaust (less backpressure). In fact, this is something I've wondered about for a while. As a motorcycle journalists, I get these interesting tech briefings on the latest motorcycles, where engineers describe the technical features of the bike complete with illustrated powerpoint presentations. Several of the motorcycle companies use valves in the exhaust system. I think Yamaha started it with the EXUP system, and other companies have followed suit. Some of the valves are located back at the muffler like the Z06, and others are in what we would probably call the midpipe. Some are even right at the collector, and the really cool ones change the flow configuration of the collector by directing air through it in a different way in different parts of the RPM range. Pure speculation on my part, but I know that engines with big ports and big cams with lots of overlap (all designed to breathe at high RPM) typically make poor low-end power - I guess because the big ports don't have much velocity at lower RPM, and the overlap allows lots of blow-through, although I'm by no means an expert. Could adding more backpressure at lower RPM help reduce this problem? Exhaust guys, this one is for you! __________________ FS!!! Koyo aluminum radiator with front-mounted fan (EG/DC)

12-05-2006, 12:06 PM	#14
blinx9900 Senior Member Join Date: Sep 2006 Location: poopfacepartytime, ca, usa Posts: 5,072	Re: (revolt_allmotor) i too wondered about the motorcycle exhaust flap, my uneducated opinion is that it does indeed have more to do with sound than flow, however i believe it can be used for power aswell: say you have a car with huge pipes... say a sohc civic with 3.5" exhaust, its going to take longer for the exhaust to reach the end of the pipe and exit the system, there may infact be a period (at lower revs) where the engine is strugling to push all this dead exhaust to the end and at that point it maybe loosing power as there is little to no velocity at this point, but put a 2" exhaust on the same car and exhaust travels a shorter path (dosent have to build up as much in smaller pipes), velocity increses sooner but yes at some point (higher revs) it will be restrictive... so i gueses you have to find a happy medium, perhaps the butterfly aids in this... __________________ ek9.org <--- a place for the ek/ej lovers [b]FS: Racing Hart C2's 17x7 4x100 otaku squad member #004 http://images.honda-tech.com/set1/smile/emsmile.gif

12-05-2006, 12:16 PM	#15
Jasper_db1 Senior Member Join Date: Dec 2003 Location: Aliso Viejo, Ca, USA Posts: 2,555	Re: Variable Exhaust Geometry (Combustion Contraption) Yamaha's EXUP http://en.wikipedia.org/wiki/EXUP __________________ Girls have unique magic tricks, they get wet without water, bleed without injury, and make boneless things hard. Jesus loves you. Allah wants you dead.

12-05-2006, 01:58 PM	#16
Master of the Universe Join Date: Mar 2002 Posts: 6,493	Re: Variable Exhaust Geometry (Jasper_db1) There is a method of achieving variable tuning with out physically changing the pipe dimensions. __________________ Semi-Retired as of April 25, 2007. Don't bother to PM me. I am tired of internet fools. Contact via RM Dealer or e-mail.

12-05-2006, 03:14 PM	#17
Combustion Contraption Senior Member Join Date: Jan 2003 Location: So Cal Posts: 8,534	I am aware that some OE manufacturers do this, but you dont see anything for the aftermarket high perf. aspect. Thats more of what i was getting at. __________________ EARL LASKEY, YOU WILL BE MISSED CCCylinderheads.com Check out the INDUCTION SPECIAL Matco Doublebay Toolbox FOR SALE Click Here!

12-05-2006, 06:08 PM	#18
blinx9900 Senior Member Join Date: Sep 2006 Location: poopfacepartytime, ca, usa Posts: 5,072	Re: (Combustion Contraption) perhaps the amount of R&D is too extensive... it would need some kind of monitering device plus electronic control... just a thought... __________________ ek9.org <--- a place for the ek/ej lovers [b]FS: Racing Hart C2's 17x7 4x100 otaku squad member #004 http://images.honda-tech.com/set1/smile/emsmile.gif

12-05-2006, 07:55 PM	#20
Combustion Contraption Senior Member Join Date: Jan 2003 Location: So Cal Posts: 8,534	Thats not roberts style. Revolt, i have an interesting SAE paper regarding variable exhaust geometry written by some members of Honda's R&D staff. PM me if youre interested. D-Rob, yeah i got your PM, good stuff! Glad everything got worked out for you. __________________ EARL LASKEY, YOU WILL BE MISSED CCCylinderheads.com Check out the INDUCTION SPECIAL Matco Doublebay Toolbox FOR SALE Click Here!

12-06-2006, 11:02 AM	#21
Master of the Universe Join Date: Mar 2002 Posts: 6,493	Re: (Combustion Contraption) It has to do with "fooling" the pressure waves in thinking that the pipe is longer. Hot gas molecules are dumb and can be readily fooled by some simple physics. __________________ Semi-Retired as of April 25, 2007. Don't bother to PM me. I am tired of internet fools. Contact via RM Dealer or e-mail.

12-06-2006, 11:18 AM	#22
Natural Aspirations Senior Member Join Date: Jul 2004 Location: Bustin Balls in Central, Pa, usa Posts: 2,362	Re: (Don Lackey) AKA THE MAN Audio resonance? __________________ I hear and I forget. I see and I remember. I do and I understand.