Miller Cycle Shop

Alright guys, we are back in my garage for another video and some of you might have seen the recent Dyno videos posted by Burger Motor Sports where their M340i is making 30 psi and still running 14 AFR. And I know t So I wanted to explain a little more detail about why the car is making so much boost, why it's running so lean and what we can expect to see with these cars since they did some JB4 tuning to see how much power the car can make. So let's go ahead and talk about it. Now as always for everybody that's new to the channel, I create these videos to help keep you updated on the latest developments in our community as well as discuss technical topics so that we have a better understanding of how our engines work. So if you're interested in more videos Now all of t And the auto cycle is what most of us have come to know with how a four stroke engine operates. So you've got the intake stroke where it sucks in air, the compression stroke where it compresses all of the air and then ignites the air fuel mixture, the power or expansion stroke where it pushes the piston down as that air fuel mixture burns, and then the exhaust stroke where the piston goes back up to push all of the exhaust gases out of the engine. So pretty straightforward, again pretty much all modern engines run some form of the auto cycle but a lot of people have tried to modify t And that's where the Atkinson cycle comes into play and the whole goal be And t Specifically on the compression stroke it takes a lot of energy to compress all of that air in the combustion chamber and also on the exhaust stroke even though you've already had the expansion stroke kind of burn up that air fuel mixture there'still some pressure built into the combustion chamber so it requires some energy to push all of that exhaust air out of the combustion chamber. So the Atkinson cycle pretty much addresses t Now there are a couple of reasons why pretty much nobody adopted t Also simply reducing the compression stroke just reduces your power directly so if you're going to reduce the compression by 20 or 30% you can effectively see the same amount of horsepower loss and that's not somet But what if you could make up that power in another way? What if you could enjoy the same efficiency that comes with the Atkinson cycle but still make the same amount of power? Now t But another way you can accomplish that is the evolution to the Miller cycle and what the Miller cycle does is it adds forced induction to the equation so either a supercharger or a turbocharger and that forced induction makes up for the compression loss that you have with the Atkinson cycle. Now if you want to accomplish t In particular you can keep the valves open for a little bit longer than normal so after the intake stroke is completed you keep the intake valves open and as the piston comes up and begins the compression stroke the valves are still open so you're forcing some of that air back out the intake valves into the intake manifold until it actually closes and starts the compression. So t Now with t Since those intake valves are open for too long you can see the boost pressure starts at But in reality if you read deeper into the BMW doc Really they're being reduced so they're closing the valves very quickly and that effectively sucks in less air so that during the compression stroke it's not compressing as much air as it would be expanding during the power stroke. So t So what I understand is basically the pressure n The engine itself isn't really seeing 30 psi boost but what we are seeing when you put that mechanical boost gauge on there is that the boost pressure is artificially being inflated because there'so much extra time where all of the intake valves are closed. They're closing so quickly that there are multiple instances where instead of always having an intake valve sucking in air you're having all the valves closed and all that boost pressure is just Now the big benefit with having variable valve timing is you can basically turn the Miller cycle on and off. So again that's kind of why you see that spike in boost pressure because the Miller cycle isn't always operating and it's not always operating at the same level. Specifically during low load versus Another benefit is when you have that longer expansion stroke it is effectively giving more time for that air fuel mix to burn and cool off so there's more heat transfer inside of the engine. Now they did have to improve engine cooling to compensate for t So with the Miller cycle allowing you to run more efficiently and having that longer exhaust stroke where you have more time for the air fuel mix to burn and expand and reduce the heat in there you're able to ac And Lambda is a term for air fuel mixture where basically 1 is perfect stoichiometric so for p 7 to 1 for 85 that would be 9. 8 to 1 for every fuel it's a little bit different but every time you run it through the Lambda scale that stoic 0. And the goal with the updated emissions requirements is to have all engines running at Lambda 1 and they're all scenarios including in boost yes including with 30 psi going through the engine. Now t So t Now I'm not sure that I would push an engine making 14 AFR but t Now t So on these newer Gen 3 B58s they're basically designed with improved cooling that'll reduce heat in the engine, reduce IATs and everyt So yeah that's kind of just how things are with the Gen 3 B58 now even more good news is Berger Motorsports did slap their JB4 on the car and see how much power they could make and it started off making 355 wheel horsepower and 396 foot pounds of torque and then b So incredible gains can be had I definitely think that hopefully one day flash tuning becomes an option so that we can richen things up, disable the Miller cycle and run a more conventional tuning package to see how much power this car can make and I still don't know if they're truly taking advantage of the port injection yet so that might be an opportunity as well to push the car even further with port injection and higher ethanol mixes I also don't know how much boost they were running in these logs either so maybe I missed that but if you guys saw how much boost they were making definitely So as I think it was very impressive to see a car on a locked DME make almost 500 wheel horsepower So we'll see as more things progress but that kind of explains the n So stay tuned other than that I t