Engine technology thread. - Page 46 - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

bambbrose · 02-07-2012, 09:09 AM

Does anything like this exist?

Variable runner length, using solenoids with a 0-XX VDC output from an ECU source, to tune the runner length?

What about a similar concept for exhaust runners?

Just drew this up this morning and when it was fresh in my head.

The idea is to have infinitely variable runner length so that you can maintain the Helmholtz resonance.

old greg · 02-07-2012, 10:06 AM

Yep, that's usually referred to as a telescoping intake runner. The Mazda 787B had them, but that's the only example that comes to mind. The main issue is getting them to move fast enough to keep up with the engine.

bambbrose · 02-07-2012, 10:19 AM

Quote:

Originally Posted by old greg

Yep, that's usually referred to as a telescoping intake runner. The Mazda 787B had them, but that's the only example that comes to mind. The main issue is getting them to move fast enough to keep up with the engine.

hahah wow that is eerily similar to what I had in my head and drew down

I think with modern linear actuators, the proper response time could be met, but cost is $$$$.

The 787B looks to be hydraulic?

Ryephile · 02-07-2012, 10:35 AM

FYI the current Yamaha R1 motorcycle has variable tuning velocity stacks. It's a great idea!

Homemade WRX · 02-07-2012, 10:57 AM

yup nothing new. Already mentioned two examples I was going to site, as well as dozens of Formula SAE cars.

bambbrose · 02-07-2012, 11:05 AM

What about the exhaust side? Too much heat to deal with?

Homemade WRX · 02-07-2012, 12:32 PM

sealing issues would seem more the thought.

Dimman · 02-07-2012, 01:13 PM

What do the butterfly valves in bike exhaust/collectors do?

serialk11r · 02-07-2012, 03:52 PM

Don't know if this was exactly correct but I think they increase pressure in the exhaust manifold (slightly) to change the speed of the exhaust waves.

Homemade WRX · 02-07-2012, 04:36 PM

^^^my thoughts too. Only reason I could see it being useful. With such a broad powerband, opening and closing an extra tube would change effective diameter of the runner.

madfast · 02-07-2012, 05:24 PM

Quote:

Originally Posted by Dimman

What do the butterfly valves in bike exhaust/collectors do?

http://en.wikipedia.org/wiki/Four-st...r_valve_system

Dimman · 02-07-2012, 05:32 PM

Quote:

Originally Posted by madfast

http://en.wikipedia.org/wiki/Four-st...r_valve_system

Four stroke power valve? Interesting, thanks.

It sounds like it's in the middle of the collector on a 4-1 setup. If it can increase return wave strength for better scavenging at low rpm, it shouldn't matter if it chokes off some of the exhaust, as flow is minimal anyways, right?

Going to look for some with/without dyno charts now...

(EXUP, go Yamaha!)

serialk11r · 02-07-2012, 06:56 PM

Okay yea so I got it wrong, it's not to increase the overall pressure, but to change the way the exhaust wave reflects back.

So I have a question since I'm too lazy to crunch a few numbers, exhaust scavenging effect on a 4 cylinder comes from the cylinder firing 180 degrees after right? So with a twin scroll turbo you essentially eliminate exhaust pulse interference effects?

Dimman · 02-07-2012, 07:28 PM

Quote:

Originally Posted by serialk11r

Okay yea so I got it wrong, it's not to increase the overall pressure, but to change the way the exhaust wave reflects back.

So I have a question since I'm too lazy to crunch a few numbers, exhaust scavenging effect on a 4 cylinder comes from the cylinder firing 180 degrees after right? So with a twin scroll turbo you essentially eliminate exhaust pulse interference effects?

With wave scavenging the primary tube reflection can 'self scavenge', same with steps. Secondary tubes can too depending on their length, and looking at total exhaust length, the atmospheric return looks like it will be closer to the 180 cylinder. Inertial/gas flow scavenging would be for the 180 cylinder.

Edit:
Found Yamaha's explanation on their site:

http://www.yamaha-motor.ca/technolog...oup=M&tech=EUP

02-07-2012, 09:09 AM	#631
bambbrose Wiring Nerd Join Date: Nov 2011 Drives: 1994 Supra Location: Wake County NC Posts: 455 Thanks: 17 Thanked 19 Times in 12 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	Does anything like this exist? Variable runner length, using solenoids with a 0-XX VDC output from an ECU source, to tune the runner length? What about a similar concept for exhaust runners? Just drew this up this morning and when it was fresh in my head. The idea is to have infinitely variable runner length so that you can maintain the Helmholtz resonance. Attached Images Last edited by bambbrose; 02-07-2012 at 09:38 AM.

02-07-2012, 10:35 AM	#634
Ryephile Hot Dog Join Date: Apr 2011 Drives: quicker than arghx7 Location: Metro Detroit Posts: 1,316 Thanks: 103 Thanked 173 Times in 83 Posts Mentioned: 6 Post(s) Tagged: 0 Thread(s)	FYI the current Yamaha R1 motorcycle has variable tuning velocity stacks. It's a great idea! __________________ "Wisdom is a not a function of age, but a function of experience." Just Say No to unqualified aftermarket products.

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02-07-2012, 10:06 AM	#632
old greg Rocket Surgeon Join Date: Apr 2011 Drives: PSM GGA OMG Location: FL Posts: 1,312 Thanks: 10 Thanked 141 Times in 84 Posts Mentioned: 2 Post(s) Tagged: 1 Thread(s)	Yep, that's usually referred to as a telescoping intake runner. The Mazda 787B had them, but that's the only example that comes to mind. The main issue is getting them to move fast enough to keep up with the engine.

02-07-2012, 10:57 AM	#635
Homemade WRX Pro Subie Engine Nerd Join Date: Dec 2011 Drives: BRZ has a reserved space Location: 3MI Racing LLC Posts: 261 Thanks: 0 Thanked 1 Time in 1 Post Mentioned: 1 Post(s) Tagged: 0 Thread(s)	yup nothing new. Already mentioned two examples I was going to site, as well as dozens of Formula SAE cars.

02-07-2012, 11:05 AM	#636
bambbrose Wiring Nerd Join Date: Nov 2011 Drives: 1994 Supra Location: Wake County NC Posts: 455 Thanks: 17 Thanked 19 Times in 12 Posts Mentioned: 0 Post(s) Tagged: 0 Thread(s)	What about the exhaust side? Too much heat to deal with?

02-07-2012, 12:32 PM	#637
Homemade WRX Pro Subie Engine Nerd Join Date: Dec 2011 Drives: BRZ has a reserved space Location: 3MI Racing LLC Posts: 261 Thanks: 0 Thanked 1 Time in 1 Post Mentioned: 1 Post(s) Tagged: 0 Thread(s)	sealing issues would seem more the thought.

02-07-2012, 04:36 PM	#640
Homemade WRX Pro Subie Engine Nerd Join Date: Dec 2011 Drives: BRZ has a reserved space Location: 3MI Racing LLC Posts: 261 Thanks: 0 Thanked 1 Time in 1 Post Mentioned: 1 Post(s) Tagged: 0 Thread(s)	^^^my thoughts too. Only reason I could see it being useful. With such a broad powerband, opening and closing an extra tube would change effective diameter of the runner.

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