Subaru's NEW Boxer Engine - The Science EXPLAINED
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Date: 2020-06-30
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Comments and reviews: 10
Jake
There's one downside to Direct Injection. Intake valve coking. In a lot of modern engines, the intake valve starts opening slightly before TDC on the exhaust stroke to help with scavenging, this allows tiny amounts of carbon to deposit on the stem and backside of the valve. Over time, without any fuel from Port Injection to wash this carbon buildup off, your intake ports and valve will experience enough buildup to hamper performance and eventually cause misfires. A lot of modern oils come with additives to help prevent this, and fuel additive packages have altered slightly to help, but it unfortunately doesn't stop it from happening, it only slows it down. So, a lot of manufacturers have taken to utilizing both Port and Direct Injection simultaneously to prevent that carbon build up. I'm speaking from personal experience with this, and from dealing with customers that wonder why their new car needs an intake and valve cleaning every 80 000 - 100 000km due to misfires. It's not something you can easily fix on turbocharged cars either, you have to pull the intake and walnut blast the carbon out of your ports and valves. It really doesn't help if you make short trips from A-B, never drive the car hard, or continuously put low quality fuel into it. All makes and models are different of course, and my experience comes primarily from VW/Audi 2. 0 TSI engines, which are absolutely notorious for carboning up, among other things.
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There's one downside to Direct Injection. Intake valve coking. In a lot of modern engines, the intake valve starts opening slightly before TDC on the exhaust stroke to help with scavenging, this allows tiny amounts of carbon to deposit on the stem and backside of the valve. Over time, without any fuel from Port Injection to wash this carbon buildup off, your intake ports and valve will experience enough buildup to hamper performance and eventually cause misfires. A lot of modern oils come with additives to help prevent this, and fuel additive packages have altered slightly to help, but it unfortunately doesn't stop it from happening, it only slows it down. So, a lot of manufacturers have taken to utilizing both Port and Direct Injection simultaneously to prevent that carbon build up. I'm speaking from personal experience with this, and from dealing with customers that wonder why their new car needs an intake and valve cleaning every 80 000 - 100 000km due to misfires. It's not something you can easily fix on turbocharged cars either, you have to pull the intake and walnut blast the carbon out of your ports and valves. It really doesn't help if you make short trips from A-B, never drive the car hard, or continuously put low quality fuel into it. All makes and models are different of course, and my experience comes primarily from VW/Audi 2. 0 TSI engines, which are absolutely notorious for carboning up, among other things.
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mtktm
The combo port and direct injection, is the reason why the 86s have the massive torque dip, that everybody complains about. Its the main reason in stock form that it doesn't make that much power in the 86. Direct injection by it self has an inherent issue of not having any solvent (gasoline) flowing over the intake valves, causing the oil thats getting past the valve seals to burn and cake onto the intake valves. Part of the reason is, the intake valve doesn't get hot enough to burn it to the point that it comes of. the leaves a cakey mess that you have clean every 20k 40k miles.
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The combo port and direct injection, is the reason why the 86s have the massive torque dip, that everybody complains about. Its the main reason in stock form that it doesn't make that much power in the 86. Direct injection by it self has an inherent issue of not having any solvent (gasoline) flowing over the intake valves, causing the oil thats getting past the valve seals to burn and cake onto the intake valves. Part of the reason is, the intake valve doesn't get hot enough to burn it to the point that it comes of. the leaves a cakey mess that you have clean every 20k 40k miles.
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SHARP1991
This new engine is horrible with direct injection! Look forward to cleaning your valves and really the entire top of your engine out every few oil changes! How do you guys promote this trash. Maybe you are just ignorant to the extreme negative long term affects of direct injection technology in gas motors. The heads start getting gunked up and leads to tons of different issues including compression and cold start symptoms. A port inject motor can run reliably for decades. This show could at least try to be real with the facts.
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This new engine is horrible with direct injection! Look forward to cleaning your valves and really the entire top of your engine out every few oil changes! How do you guys promote this trash. Maybe you are just ignorant to the extreme negative long term affects of direct injection technology in gas motors. The heads start getting gunked up and leads to tons of different issues including compression and cold start symptoms. A port inject motor can run reliably for decades. This show could at least try to be real with the facts.
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mtktm
The FA24 engine block is basically the EZ30/EZ36 with 2 less cylinders( same displacement per cylinder as the EZ36)
By going off of that, the EZ36 has terribly narrow conrods mainly because of clearances of piston diameter to stock (To keep piston size to stroke, square.
So they're have to make a lot more clearance for the conrods.
EDIT: got to the part of the video stating thicker conrods. Wider conrods isn't add as much strength as ones that are bigger in the axis of load.
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The FA24 engine block is basically the EZ30/EZ36 with 2 less cylinders( same displacement per cylinder as the EZ36)
By going off of that, the EZ36 has terribly narrow conrods mainly because of clearances of piston diameter to stock (To keep piston size to stroke, square.
So they're have to make a lot more clearance for the conrods.
EDIT: got to the part of the video stating thicker conrods. Wider conrods isn't add as much strength as ones that are bigger in the axis of load.
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isaac
Under high load and boost what causes failed engines is detonation which causes an destructive explosive that yes surges into the piston and if you have multiple det occunences that s what kills rods. If you smooth of the afr and have the energy evenly displace onto the piston you won t have problems. That s why modified cars are more likely than stock to blow up. Please hire me so I can do this right cause I won t beable to watch these anymore if you keep going this direction
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Under high load and boost what causes failed engines is detonation which causes an destructive explosive that yes surges into the piston and if you have multiple det occunences that s what kills rods. If you smooth of the afr and have the energy evenly displace onto the piston you won t have problems. That s why modified cars are more likely than stock to blow up. Please hire me so I can do this right cause I won t beable to watch these anymore if you keep going this direction
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autos
If the statement about port injection was correct, fuel would build upon the inlet valve. It doesn't. All the fuel still ends up in the engine.
But also we know about the problem of DI - oil buildup on the inlet valve stem due to leaks past the valve guide seals as they age. Boxers already have a bit of an oil usage problem due to the difficulty of draining the heads which are on a level with the crankcase.
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If the statement about port injection was correct, fuel would build upon the inlet valve. It doesn't. All the fuel still ends up in the engine.
But also we know about the problem of DI - oil buildup on the inlet valve stem due to leaks past the valve guide seals as they age. Boxers already have a bit of an oil usage problem due to the difficulty of draining the heads which are on a level with the crankcase.
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Crysmatic
kudos that you got auto-ignition right. poor explanation for GDI. dynamic compression ratio will be around 8: 1, so pressure at tdc will be 120psi, and peak cylinder pressure will be in the 1100-1400psi range. beehive springs work because the parts that move weigh less. and the new ports are high tumble which is good for fuel economy and emissions, and because they had to package the GDI injectors.
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kudos that you got auto-ignition right. poor explanation for GDI. dynamic compression ratio will be around 8: 1, so pressure at tdc will be 120psi, and peak cylinder pressure will be in the 1100-1400psi range. beehive springs work because the parts that move weigh less. and the new ports are high tumble which is good for fuel economy and emissions, and because they had to package the GDI injectors.
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Christian
Subbie tech here, I love the FA24. I know the tune will be different bit it gets into boost immediately and goes and goes and goes. It's funny being in an Ascent and catching up to people on the service road and then past them. It's a wonderful motor and I cant wait to see how it performs in the STI. We also haven't had to take out any FA24s yet but it is still fairly new.
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Subbie tech here, I love the FA24. I know the tune will be different bit it gets into boost immediately and goes and goes and goes. It's funny being in an Ascent and catching up to people on the service road and then past them. It's a wonderful motor and I cant wait to see how it performs in the STI. We also haven't had to take out any FA24s yet but it is still fairly new.
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SHARP1991
I cannot believe you idiots would have an entire segment on direct injection vs port injection and not mention about dirty valves and needing to clean out your heads with direct injection! These engines start building up carbon and harming the engine very quickly because the gas is not cleaning the valves and where the valves seal to.
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I cannot believe you idiots would have an entire segment on direct injection vs port injection and not mention about dirty valves and needing to clean out your heads with direct injection! These engines start building up carbon and harming the engine very quickly because the gas is not cleaning the valves and where the valves seal to.
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Luis
Yeahhhh. no let the timing belt snap on it. Don't get me wrong I love subaru specially the impreza line but I would never buy one cause if something major happens like the timing belt snaping or rarely hapends but one of valve spring snaping in one of heads. There is no way you can work on it with dropping the engine first. Sadly it's true
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Yeahhhh. no let the timing belt snap on it. Don't get me wrong I love subaru specially the impreza line but I would never buy one cause if something major happens like the timing belt snaping or rarely hapends but one of valve spring snaping in one of heads. There is no way you can work on it with dropping the engine first. Sadly it's true
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