GR Yaris R&T: More Cylinders Don't Always Mean More Power

Michael Knight

Michael Knight

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Article provides some design insight of the Engine used in GR Corolla and GR Yaris.
GR Corolla seems definitely be running in higher boost levels than GRY. Also the pistons are said to be even lighter than with GRY.

www.roadandtrack.com

More Cylinders Don't Always Mean More Power

For a given displacement, you want the most possible cylinders, right? Not quite. The rally origins of the GR Corolla's three-cylinder prove it.
www.roadandtrack.com www.roadandtrack.com
 
its built to meet certain engine regs thats why they went down that route...interesting article but i bet theres some manufacturers out there that will also justify why they went "more" cylinders
 
It also misses that lots of 4-cyl have balance shafts, so not an as big disadvantage as portrayed for our 3-pot
 
Yep misses definitely few benefits of 3cyl such as no need for twin scroll but anyways okeyish writeup.
 
An inline-3 cyl in inherently better balanced than a 4 cyl engine. It’s half of a straight six which is the most perfectly balanced engine of all configurations. The fact that it’s half creates an imbalance due to the torque not being in unison across the crankshaft, hence why they need a balancing shaft. But in terms of the primary and secondary forces being balanced vertically, the inline-3 is superior to the 4.

In terms of refinement and engine response, having a power stroke every 90 deg rotation of the crankshaft (4 cyl) is better than every 120 deg (3 cyl), but this is easily dealt with through engine management and the differences are negligible in practice, especially with forced induction.

The 3 cylinder engine is also smaller, lighter, fewer moving parts so more efficient, cheaper to manufacture and maintain and less prone to failure.

The primary reason for having more cylinders, is to create more power and torque through greater displacement. But when you can achieve the displacement you want, and the power and torque you need for the application with fewer cylinders, it’s a bit of a no-brainer.
 
Don't most 4 cylinder engines fire every 180 degrees as the pistons move in pairs for better balance, i.e. the outer pair move together as do the inner pair? I believe Yamaha make a few engines that don't do this and fire every 90 degrees though.
 
TheManWithTheStick said:
Don't most 4 cylinder engines fire every 180 degrees as the pistons move in pairs for better balance, i.e. the outer pair move together as do the inner pair? I believe Yamaha make a few engines that don't do this and fire every 90 degrees though.
Click to expand...
Crossplane on the R1, 90 - 270 - 90 - 270 or something like that. Sounds like a V4....
 
TheManWithTheStick said:
Don't most 4 cylinder engines fire every 180 degrees as the pistons move in pairs for better balance, i.e. the outer pair move together as do the inner pair? I believe Yamaha make a few engines that don't do this and fire every 90 degrees though.
Click to expand...
They do, a 4 stroke engine will always mean a piston being on the power stroke every two revolutions of the crankshaft or 720 degrees. So an inline-4 cyl will be 180 degrees and an inline-3 cyl 240 degrees between power strokes.

The 120 degrees and 90 degrees refers to the crankshaft angle of the 3 and 4 cylinder engines respectively. Sorry.
 
Steve said:
An inline-3 cyl in inherently better balanced than a 4 cyl engine. It’s half of a straight six which is the most perfectly balanced engine of all configurations. The fact that it’s half creates an imbalance due to the torque not being in unison across the crankshaft, hence why they need a balancing shaft. But in terms of the primary and secondary forces being balanced vertically, the inline-3 is superior to the 4.

In terms of refinement and engine response, having a power stroke every 90 deg rotation of the crankshaft (4 cyl) is better than every 120 deg (3 cyl), but this is easily dealt with through engine management and the differences are negligible in practice, especially with forced induction.

The 3 cylinder engine is also smaller, lighter, fewer moving parts so more efficient, cheaper to manufacture and maintain and less prone to failure.

The primary reason for having more cylinders, is to create more power and torque through greater displacement. But when you can achieve the displacement you want, and the power and torque you need for the application with fewer cylinders, it’s a bit of a no-brainer.
Click to expand...

they still have their limits.. as said less is not always more....a 1.6 single cylinder wouldnt be as great...

you could as well say a 3 cylinder is more stressed than a 4 cylinder and therefore potentially more prone to wear or failure....defiantly the case with vw 1.0 3 cylinder engines

the gr engine brings together lots on current engine thinking and puts it in a 3 cylinder to meet a certain regs and in the process builds a little fire cracker!

be interesting to see how the engine copes with 50/60k miles of use
 
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