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Toshi

butthole powerwashing evangelist
Oct 23, 2001
39,638
8,684
They may be, but in reality you don't need all that room to move 300hp of exhaust, I remember this from research into the exhaust sizes and piping for my WRX. In general, it's all for show.
300 hp from 1.6 liters is impressive, though. Perhaps it's needed given that it's pushed so hard.
 

Jm_

sled dog's bollocks
Jan 14, 2002
20,065
10,630
AK
300 hp from 1.6 liters is impressive, though. Perhaps it's needed given that it's pushed so hard.
Doesn't matter how big the engine is IMO, the exhaust is relative to the power and a direct result of how much fuel and air is being crammed in there. Never seen a correlation with the size of the engine, only the power it produces.
 

Toshi

butthole powerwashing evangelist
Oct 23, 2001
39,638
8,684
Doesn't matter how big the engine is IMO, the exhaust is relative to the power and a direct result of how much fuel and air is being crammed in there. Never seen a correlation with the size of the engine, only the power it produces.
I think it could matter. At peak power then, yes, the fuel and air from ye olde 8 liter truck V-10 and the 1.6 liter three banger will be the same. So one wants equally low backpressure.

But off boost that 1.6 liter mill will benefit from having that third exhaust closed via its valve and thus a more normal backpressure exhaust. Per The Drive article that's exactly what's done here.
 

SkaredShtles

Michael Bolton
Sep 21, 2003
67,677
14,080
In a van.... down by the river
I think it could matter. At peak power then, yes, the fuel and air from ye olde 8 liter truck V-10 and the 1.6 liter three banger will be the same. So one wants equally low backpressure.

But off boost that 1.6 liter mill will benefit from having that third exhaust closed via its valve and thus a more normal backpressure exhaust. Per The Drive article that's exactly what's done here.
Wait. So the third exhaust is turned on and off? JHFC.
 

Toshi

butthole powerwashing evangelist
Oct 23, 2001
39,638
8,684
Wait. So the third exhaust is turned on and off? JHFC.
from da article

"The center one is for the high-power," said Toyota Chief Engineer Naoyuki Sakamoto in an interview with The Drive. "Above a certain engine rpm, there is a valve. So they open that and it goes straight to the outside of the car, which reduces the backpressure and achieves the 300 horsepower."
 

StiHacka

Compensating for something
Jan 4, 2013
21,560
12,508
In hell. Welcome!
The AWD on that GRC looks good, too. If could be a fun little commuter and bike hauler, if a bike rack solution exists. I doubt a modern FS bike fits inside even with the wheels removed.
 

jimmydean

The Official Meat of Ridemonkey
Sep 10, 2001
42,971
15,048
Portland, OR
Its how a lot of cars are done now - next time you're behind a BMW look at the left and right exhaust tips. One will be closed unless they are on the gas a significant amount.
It's a great idea. It's like side out exhausts but instead of a switch, it's rev actuated. Kind of genius, really.
 

Westy

the teste
Nov 22, 2002
55,944
21,975
Sleazattle
I think it could matter. At peak power then, yes, the fuel and air from ye olde 8 liter truck V-10 and the 1.6 liter three banger will be the same. So one wants equally low backpressure.

But off boost that 1.6 liter mill will benefit from having that third exhaust closed via its valve and thus a more normal backpressure exhaust. Per The Drive article that's exactly what's done here.

People need to stop taking about back-pressure for exhausts. Exhaust does not flow constantly like a garden hose so there is no constant back pressure. Exhaust flows in pulses and the inertia from those pulses can create a vacuum. The exhaust system is more like a wind instrument where in the ideal situation the resonant frequency of the exhaust matches engine RPM and the minimum pressure of the wave times up with the opening of the exhaust valve. Actually closer to the opening of the intake valve. The benefit of that vacuum has less to do with allowing exhaust to more easily leave the engine but actually sucking in a more dense intake charge during valve opening overlap.

The magnitude of those vacuum pulses is proportional to exhaust velocity, which a smaller diameter exhaust will provide, but a smaller pipe provides increased resistance which will inhibit that velocity. So there is an optimization point based on the engines torque characteristics and intended use. A very small turbo engine will naturally make good power but with lower torque so for a street car you probably want a smaller exhaust to improve lower RPM performance. A giant V-8 has plenty of low end grunt so a larger exhaust will improve overall performance.

Years ago I bought a license for "pipes" software which will calculate the ideal exhaust configuration for a given engine under specific conditions. I think I get 10 installs with it if anyone wants to play around with it.
 

StiHacka

Compensating for something
Jan 4, 2013
21,560
12,508
In hell. Welcome!
The exhaust system is more like a wind instrument where in the ideal situation the resonant frequency of the exhaust matches engine RPM and the minimum pressure of the wave times up with the opening of the exhaust valve.
My exhaust is definitely a wind instrument with a narrow range of resonant frequencies. :busted:
 

stoney

Part of the unwashed, middle-American horde
Jul 26, 2006
21,993
7,868
Colorado

I just... That's so ungodly fast. The ///M was holy shit fast. That's just... Wow. @Nick can attest, as he drove it. That's just fucking gonzo.
 

Adventurous

Starshine Bro
Mar 19, 2014
10,823
9,853
Crawlorado

I just... That's so ungodly fast. The ///M was holy shit fast. That's just... Wow. @Nick can attest, as he drove it. That's just fucking gonzo.
Better put some solid tow points on those things, I predict many of these deceiving high powered vehicles will be piloted into ditches by unskilled operators.
 
People need to stop taking about back-pressure for exhausts. Exhaust does not flow constantly like a garden hose so there is no constant back pressure. Exhaust flows in pulses and the inertia from those pulses can create a vacuum. The exhaust system is more like a wind instrument where in the ideal situation the resonant frequency of the exhaust matches engine RPM and the minimum pressure of the wave times up with the opening of the exhaust valve. Actually closer to the opening of the intake valve. The benefit of that vacuum has less to do with allowing exhaust to more easily leave the engine but actually sucking in a more dense intake charge during valve opening overlap.

The magnitude of those vacuum pulses is proportional to exhaust velocity, which a smaller diameter exhaust will provide, but a smaller pipe provides increased resistance which will inhibit that velocity. So there is an optimization point based on the engines torque characteristics and intended use. A very small turbo engine will naturally make good power but with lower torque so for a street car you probably want a smaller exhaust to improve lower RPM performance. A giant V-8 has plenty of low end grunt so a larger exhaust will improve overall performance.

Years ago I bought a license for "pipes" software which will calculate the ideal exhaust configuration for a given engine under specific conditions. I think I get 10 installs with it if anyone wants to play around with it.
Argues for an exhaust system with dynamically adjustable resonance.
 

jimmydean

The Official Meat of Ridemonkey
Sep 10, 2001
42,971
15,048
Portland, OR
I dunno, not having engine noise to drown out the screams of your passengers while silently hooning it into a ditch at 90 sounds pretty visceral to me.
My buddy Jeff just got his plaid a few months back and even put proper wheels and tires on it. He has a plethora of insane cars. 1300bhp R35 GTR, 600bhp R32 Skyline, 500ish bhp WRX STi, and a 600ish twin turbo GTO. He claims the manuals (R32, GTO, STi) are still the funnest even though the plaid smokes them all and has cost him the least.

FB_IMG_1649362916309.jpg
 

Westy

the teste
Nov 22, 2002
55,944
21,975
Sleazattle
Argues for an exhaust system with dynamically adjustable resonance.
They exist, just usually requires expensive components that can hand the high temperatures. The same thing works with intake plenum geometry and there were a lot of companies doing that in the '90s. VW VR6 and GM Vortech engines come to mind. Several motorcycles models use a valve in the exhaust to do the same thing.

Most of those gains have been overshadowed by variable valve timing which essentially allows for a variable tune that follows peak output across the RPM range.