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One thing that is quite important to note is that the EGR is a necessary combustion temperature regulator, and removing it isn’t good for anything, including fu

One thing that is quite important to note is that the EGR is a necessary combustion temperature regulator, and removing it isn’t good for anything, including fuel economy. The engine deposits people blame on it is usually from the PCV. Only downside to it is that it occasionally need to get cleaned, and in tiny cars it tends to be in a stupid position. Now, DPF and cats are a bit more black and white, but a bit of horsepower for not giving people lung cancer and worsening the whole environmental situation is an easy trade. It’s ridiculous that it’s not federal as is - stuff that harms everyone around you shouldn’t be your decision. If one doesn’t like these trade-offs, look into technologies that don’t require them like hydrogen or electric. The trade-offs there tends aren’t as controversial, just personal financial ones like range, weight and charge/fuel supply. And they are getting better. As an aside, looking at how Edison Motors channel (US company trying to make electric trucks) drools over Scania engines, it seems like US truck engines are quite underpowered yet thirsty compared to the EU. :/

consp 2y ago
> not giving people lung cancer I've seen far less reports of soot and smog in recent years (though it's still there), and it's the same with vaccines: People don't remember how bad it was and then argue against the thing preventing it. Also: smog and soot deposits don't care about state borders.
pif 2y ago
> EGR is a necessary [...], and removing it isn’t good for anything EGR is what killed responsiveness in internal combustion engines. I'm not advocating breaking the law, but it would be nice if people remembered what we are missing and started pushing for having it back.
- arghwhat 2y ago
  I don't see how the EGR could possibly affect perceived responsiveness. What "killed responsiveness" in my opinion is heavy turbocharging with long spool-up times, with engines so small that they cannot even maintain highway speeds at full throttle without boost pressure. Or, if only naturally aspirated engines are responsive enough for you, boost altogether. The EGR only opens when the cylinders are running too hot and there is is no request for power. It is fully closed during normal driving, and even when it is open it will slam shut the moment you touch the throttle. Heck, you might not even experience it opening at all during some driving sessions. "driving 4 answers" has a pretty good video on EGR (note that the particular format of the video requires sticking around for the "debunk"): https://www.youtube.com/watch?v=Bnpj4eIo6nI&t=1637s https://www.youtube.com/watch?v=Bnpj4eIo6nI&t=1637s > but it would be nice if people remembered what we are missing and started pushing for having it back. We got something far, far more responsive: Electric. Combustion engine don't even make it to the leader board, and with some of the electric options out there, the speed of your throttle foot ends up being a significant bottleneck.
  - MarkMarine 2y ago
    Did you watch that video you recommended? Might need a rewatch. 1. My diesel, like most now is a turbo. Pumping losses are not relevant. 2. 30% lower combustion temp relates to that level of efficiency loss 3. The EGR is open A LOT to keep NOx down from a modern diesel. 3. The COMBO of PCV and all the soot from EGR is the exact problem. The oil from PCV wouldn’t coke in the intake tract without the soot, its oil mist. You pop open an engine with PCV and no EGR and the intake tracts are a little oily. Open a diesel with EGR and you see what it looks like in that video. Regarding electric, what’s the range of the available electric tow vehicle that costs 50k and can tow 18,000 lbs with 10% of that on the rear axle? -inf because it doesn’t exist. I had an electric car, I’m all for it for single vehicle travel. For actual towing, like I use my truck for, it’s going to take a step change in battery capacity. I would welcome a heavy hybrid in the style of modern trains, I’ll spend more than I make up in fuel economy to purchase it.
    - arghwhat 2y ago
      Yes, I did. But I feel like you missed key points? 1. The video mentions pumping losses because it was an old argument against EGR, which only applied to older diesels relying on a butterfly valve for vacuum. Pumping losses still matter in a turbodiesel though, as it's a resistance you need to overcome with more fuel. 2. At idle, when the EGR is open, you get a lower combustion temperature which accelerates the natural cooling of the combustion chamber that happens at idle. So at that point, when the engine is using the least possible amount of fuel, efficiency will be dropped for a while. But: 3. The EGR is only ever fully open for a bit when idling after the cylinders have been run hot. Once the temperature has dropped a bit, it will be only be slightly open. When you press the gas, it closes entirely. When fully closed, it has no impact on efficiency. 4. No, the EGR is entirely harmless - the small amount of recirculated exhaust gas only contains things that were already present in the cylinder a moment ago. The PCV on the other hand pulls oil into the combustion chamber. If you're concerned about the idle fuel economy impact of the EGR, get a car/truck with start-stop as it removes the concern entirely, netting you an inf% improvement to idle fuel consumption. > Regarding electric, what’s the range of the available electric tow vehicle that costs 50k and can tow 18,000 lbs with 10% of that on the rear axle? -inf because it doesn’t exist. Ignoring that it wouldn't be "minus infinity", no one is claiming that someone actively towing 18000 lbs should buy an electric before they can do what you need them to do. People can get over-excited about technology to the point of pushing it a bit too hard. If you have an actual need (most people citing towing capabilities have never used their trailer hitch), keep using a gasoline truck with the correct factory emission equipment until the better technologies have matured for your use-case.
- blactuary 2y ago
  The health of people and the planet is more important than you wanting to go zoom zoom
pjc50 2y ago
> If one doesn’t like these trade-offs, look into technologies that don’t require them like hydrogen or electric. The trade-offs there tends aren’t as controversial, just personal financial ones like range, weight and charge/fuel supply. And they are getting better. Yeah, I think the attempts to do "clean" diesel are doomed. Volkswagen proved that the standards couldn't be met without cheating. The EU petrol/diesel car phaseout starts in 2035, but perhaps the diesel side of the phaseout needs to be more aggressive such as rationing the number of diesels sold or putting more "low emission zones" in place.
- arghwhat 2y ago
  The push for diesel was also... Weird. It was a way of dealing with a supply chain issues, whereby a demand of heavier oil was needed for production to stay economical. driving 4 answers also has a decently informative video on this particular topic: https://www.youtube.com/watch?v=w8r2xnITnqA https://www.youtube.com/watch?v=w8r2xnITnqA
jasode 2y ago
>If one doesn’t like these trade-offs, look into technologies that don’t require them like hydrogen or electric. [...] just personal financial ones like range, weight and charge/fuel supply. It's not just personal/financial. It's also raw capability of a diesel truck to get the particular type of jobs done. A lot of the shops did the deletes on trucks that can tow 12000+ lbs. Think of trucks like Ford F-250, F-350, and beyond etc, towing landscaping equipment like a 10000 lb skidsteer on a 14000-lbs-rated trailer. Or hotshot truckers carrying random loads. Some non-commercial trucks (smaller than class 4) can tow up to 40000 lbs. The Rivian and Cyber trucks only have max tow capacity up to 11000 to 12000 lbs. There isn't a comparable hydrogen/electric substitute that can do what the diesel pickup trucks can do. In contrast, there are realistic EV substitutes for diesel cars. Those diesel delete shops were typically modifying high-towing-capacity trucks and not the smaller Volkswagon diesel passenger cars. Some truck owners were justifying the deletes because they believe the EGR/DPF/DEF was flawed and would lead to a ticking time bomb of expensive engine repairs down the road. (Cue up a bunch of anecdotes of how the "old diesel engines were reliable and bulletproof" compared to the "new diesel engines with all that EPA emissions crap requiring out-of-warranty repairs" ) I don't know enough about the engineering to know if they're correct or blowing it all out of proportion.
- arghwhat 2y ago
  > It's not just personal/financial. It's also raw capability of a diesel truck to get the particular type of jobs done. What I was saying is not that electric solved all problems yet, but that messing with electric and trade-offs in decisions there only really affect you. Messing with a diesel, the trade-offs affect everyone around you - a bit a power paid by everyone else's cancer risk and deteriorating environment. That's not a decision you should be allowed to make for moral reasons. With DPF/cat, you do have a risk for expensive service: If you completely neglect it, intentionally run a very sooty tune and never do the (usually automatic) cleaning cycle. At that point, it'll clog up, break, and need to be replaced. But that's easy to avoid, and not something that ups your service interval either. You would also get extremely expensive repairs if you don't change and monitor engine oil, but no trucker would consider it a big deal. That Rivian only tows 5.5 tons is probably just a matter of demand. Even if it has its uses, I imagine the actual demand for towing 20 tons on personal vehicle is quite low. It could also be that they deemed that the battery range would be too silly at these loads, which is luckily an area of with quite rapid improvement these days - battery range has come a long way. Also note that you definitely don't need to mess with emissions to tow 20 tons. Messing with EGR grants you zero additional power. Removing DPF and catalytic converter can give you a little bit, but not enough to go from being unable to tow 20 tons to being able, and if you need to tow 20 tons you should start out by buying a truck rated to tow 20 tons as more engine power is not enough to do that safely. > A lot of the shops did the deletes on trucks that can tow Don't trust the sales pitch from the tuning shops that sell the mods. > Cue up a bunch of anecdotes of how the "old diesel engines were reliable and bulletproof" Heh, those statements are not entirely false, but they forget important details. Some of the engines old-timers might be fondly remembering as indestructible have dual digit HP ratings, at the size and fuel consumption of something rated in the hundreds of HP today. It's not hard to build an indestructible engine if you don't have to care about size, weight, fuel efficiency, power or responsiveness.
MarkMarine 2y ago
EGR is not required to control combustion temp. I’ve been building motors and competing in Motorsport all my life, never used EGR and my temps are great. It’s for emissions and on a diesel, injects soot into the intake
- arghwhat 2y ago
  It injects a small amount of gas that came from the cylinder back into the cylinder - nothing that doesn't belong in a cylinder. The only source of extra gunk and buildup is the oil droplets or outright drooling pulled in by the PCV. The reason you never used an EGR is because you're building for motorsport - you don't care that your cylinders are too hot for too long when you release the throttle. You care about what happens at or near peak power, and even if you had an EGR it would be fully closed, so why bother. Note that it's for any combustion engine, not just diesel.
  - MarkMarine 2y ago
    It injects exhaust. Burned fuel air with NOx, CO, CO2, and very little oxygen. It does this to lower in cylinder combustion temp and reduce the formation of NOx. Less oxygen in the cylinder means less temp which means less power. That is just a fact, it’s thermodynamic law, you literally can’t dispute it. The only Motorsport engines built for full throttle only are drag and pull engines, but where I race throttle response and the whole torque curve from 8,000 to 16,500 RPM is incredibly important. Find me an EGR system on any purpose built engine that didn’t have to comply with emissions. Industrial engines, race engines, tractors, generators… anything. That should illuminate what EGR is actually for.

consp 2y ago

> not giving people lung cancer I've seen far less reports of soot and smog in recent years (though it's still there), and it's the same with vaccines: People don't remember how bad it was and then argue against the thing preventing it. Also: smog and soot deposits don't care about state borders.

pif 2y ago

> EGR is a necessary [...], and removing it isn’t good for anything EGR is what killed responsiveness in internal combustion engines. I'm not advocating breaking the law, but it would be nice if people remembered what we are missing and started pushing for having it back.

arghwhat 2y ago
I don't see how the EGR could possibly affect perceived responsiveness. What "killed responsiveness" in my opinion is heavy turbocharging with long spool-up times, with engines so small that they cannot even maintain highway speeds at full throttle without boost pressure. Or, if only naturally aspirated engines are responsive enough for you, boost altogether. The EGR only opens when the cylinders are running too hot and there is is no request for power. It is fully closed during normal driving, and even when it is open it will slam shut the moment you touch the throttle. Heck, you might not even experience it opening at all during some driving sessions. "driving 4 answers" has a pretty good video on EGR (note that the particular format of the video requires sticking around for the "debunk"): https://www.youtube.com/watch?v=Bnpj4eIo6nI&t=1637s https://www.youtube.com/watch?v=Bnpj4eIo6nI&t=1637s > but it would be nice if people remembered what we are missing and started pushing for having it back. We got something far, far more responsive: Electric. Combustion engine don't even make it to the leader board, and with some of the electric options out there, the speed of your throttle foot ends up being a significant bottleneck.
- MarkMarine 2y ago
  Did you watch that video you recommended? Might need a rewatch. 1. My diesel, like most now is a turbo. Pumping losses are not relevant. 2. 30% lower combustion temp relates to that level of efficiency loss 3. The EGR is open A LOT to keep NOx down from a modern diesel. 3. The COMBO of PCV and all the soot from EGR is the exact problem. The oil from PCV wouldn’t coke in the intake tract without the soot, its oil mist. You pop open an engine with PCV and no EGR and the intake tracts are a little oily. Open a diesel with EGR and you see what it looks like in that video. Regarding electric, what’s the range of the available electric tow vehicle that costs 50k and can tow 18,000 lbs with 10% of that on the rear axle? -inf because it doesn’t exist. I had an electric car, I’m all for it for single vehicle travel. For actual towing, like I use my truck for, it’s going to take a step change in battery capacity. I would welcome a heavy hybrid in the style of modern trains, I’ll spend more than I make up in fuel economy to purchase it.
  - arghwhat 2y ago
    Yes, I did. But I feel like you missed key points? 1. The video mentions pumping losses because it was an old argument against EGR, which only applied to older diesels relying on a butterfly valve for vacuum. Pumping losses still matter in a turbodiesel though, as it's a resistance you need to overcome with more fuel. 2. At idle, when the EGR is open, you get a lower combustion temperature which accelerates the natural cooling of the combustion chamber that happens at idle. So at that point, when the engine is using the least possible amount of fuel, efficiency will be dropped for a while. But: 3. The EGR is only ever fully open for a bit when idling after the cylinders have been run hot. Once the temperature has dropped a bit, it will be only be slightly open. When you press the gas, it closes entirely. When fully closed, it has no impact on efficiency. 4. No, the EGR is entirely harmless - the small amount of recirculated exhaust gas only contains things that were already present in the cylinder a moment ago. The PCV on the other hand pulls oil into the combustion chamber. If you're concerned about the idle fuel economy impact of the EGR, get a car/truck with start-stop as it removes the concern entirely, netting you an inf% improvement to idle fuel consumption. > Regarding electric, what’s the range of the available electric tow vehicle that costs 50k and can tow 18,000 lbs with 10% of that on the rear axle? -inf because it doesn’t exist. Ignoring that it wouldn't be "minus infinity", no one is claiming that someone actively towing 18000 lbs should buy an electric before they can do what you need them to do. People can get over-excited about technology to the point of pushing it a bit too hard. If you have an actual need (most people citing towing capabilities have never used their trailer hitch), keep using a gasoline truck with the correct factory emission equipment until the better technologies have matured for your use-case.
blactuary 2y ago
The health of people and the planet is more important than you wanting to go zoom zoom

pjc50 2y ago

> If one doesn’t like these trade-offs, look into technologies that don’t require them like hydrogen or electric. The trade-offs there tends aren’t as controversial, just personal financial ones like range, weight and charge/fuel supply. And they are getting better. Yeah, I think the attempts to do "clean" diesel are doomed. Volkswagen proved that the standards couldn't be met without cheating. The EU petrol/diesel car phaseout starts in 2035, but perhaps the diesel side of the phaseout needs to be more aggressive such as rationing the number of diesels sold or putting more "low emission zones" in place.

arghwhat 2y ago
The push for diesel was also... Weird. It was a way of dealing with a supply chain issues, whereby a demand of heavier oil was needed for production to stay economical. driving 4 answers also has a decently informative video on this particular topic: https://www.youtube.com/watch?v=w8r2xnITnqA https://www.youtube.com/watch?v=w8r2xnITnqA

jasode 2y ago

>If one doesn’t like these trade-offs, look into technologies that don’t require them like hydrogen or electric. [...] just personal financial ones like range, weight and charge/fuel supply. It's not just personal/financial. It's also raw capability of a diesel truck to get the particular type of jobs done. A lot of the shops did the deletes on trucks that can tow 12000+ lbs. Think of trucks like Ford F-250, F-350, and beyond etc, towing landscaping equipment like a 10000 lb skidsteer on a 14000-lbs-rated trailer. Or hotshot truckers carrying random loads. Some non-commercial trucks (smaller than class 4) can tow up to 40000 lbs. The Rivian and Cyber trucks only have max tow capacity up to 11000 to 12000 lbs. There isn't a comparable hydrogen/electric substitute that can do what the diesel pickup trucks can do. In contrast, there are realistic EV substitutes for diesel cars. Those diesel delete shops were typically modifying high-towing-capacity trucks and not the smaller Volkswagon diesel passenger cars. Some truck owners were justifying the deletes because they believe the EGR/DPF/DEF was flawed and would lead to a ticking time bomb of expensive engine repairs down the road. (Cue up a bunch of anecdotes of how the "old diesel engines were reliable and bulletproof" compared to the "new diesel engines with all that EPA emissions crap requiring out-of-warranty repairs" ) I don't know enough about the engineering to know if they're correct or blowing it all out of proportion.

arghwhat 2y ago
> It's not just personal/financial. It's also raw capability of a diesel truck to get the particular type of jobs done. What I was saying is not that electric solved all problems yet, but that messing with electric and trade-offs in decisions there only really affect you. Messing with a diesel, the trade-offs affect everyone around you - a bit a power paid by everyone else's cancer risk and deteriorating environment. That's not a decision you should be allowed to make for moral reasons. With DPF/cat, you do have a risk for expensive service: If you completely neglect it, intentionally run a very sooty tune and never do the (usually automatic) cleaning cycle. At that point, it'll clog up, break, and need to be replaced. But that's easy to avoid, and not something that ups your service interval either. You would also get extremely expensive repairs if you don't change and monitor engine oil, but no trucker would consider it a big deal. That Rivian only tows 5.5 tons is probably just a matter of demand. Even if it has its uses, I imagine the actual demand for towing 20 tons on personal vehicle is quite low. It could also be that they deemed that the battery range would be too silly at these loads, which is luckily an area of with quite rapid improvement these days - battery range has come a long way. Also note that you definitely don't need to mess with emissions to tow 20 tons. Messing with EGR grants you zero additional power. Removing DPF and catalytic converter can give you a little bit, but not enough to go from being unable to tow 20 tons to being able, and if you need to tow 20 tons you should start out by buying a truck rated to tow 20 tons as more engine power is not enough to do that safely. > A lot of the shops did the deletes on trucks that can tow Don't trust the sales pitch from the tuning shops that sell the mods. > Cue up a bunch of anecdotes of how the "old diesel engines were reliable and bulletproof" Heh, those statements are not entirely false, but they forget important details. Some of the engines old-timers might be fondly remembering as indestructible have dual digit HP ratings, at the size and fuel consumption of something rated in the hundreds of HP today. It's not hard to build an indestructible engine if you don't have to care about size, weight, fuel efficiency, power or responsiveness.

MarkMarine 2y ago

EGR is not required to control combustion temp. I’ve been building motors and competing in Motorsport all my life, never used EGR and my temps are great. It’s for emissions and on a diesel, injects soot into the intake

arghwhat 2y ago
It injects a small amount of gas that came from the cylinder back into the cylinder - nothing that doesn't belong in a cylinder. The only source of extra gunk and buildup is the oil droplets or outright drooling pulled in by the PCV. The reason you never used an EGR is because you're building for motorsport - you don't care that your cylinders are too hot for too long when you release the throttle. You care about what happens at or near peak power, and even if you had an EGR it would be fully closed, so why bother. Note that it's for any combustion engine, not just diesel.
- MarkMarine 2y ago
  It injects exhaust. Burned fuel air with NOx, CO, CO2, and very little oxygen. It does this to lower in cylinder combustion temp and reduce the formation of NOx. Less oxygen in the cylinder means less temp which means less power. That is just a fact, it’s thermodynamic law, you literally can’t dispute it. The only Motorsport engines built for full throttle only are drag and pull engines, but where I race throttle response and the whole torque curve from 8,000 to 16,500 RPM is incredibly important. Find me an EGR system on any purpose built engine that didn’t have to comply with emissions. Industrial engines, race engines, tractors, generators… anything. That should illuminate what EGR is actually for.