Wouldn't the same be realized if they reduce throttle pressure, for example to 50kW and then the rest can harvested?
Seems like it would be more intuitive but maybe harder to get correct every lap.
There is rule C5.2.5, which limits fuel energy flow at partial load:
At partial load, the fuel energy flow must not exceed the limit curve defined below:
EF (MJ/h) = 380 when the engine power is equal to or below −50kW
EF (MJ/h) = 9.78 x engine power (kW) + 869 when the engine power is above −50kW
Basically, at 50kW you ony get 1358MJ/h, so ~45% of the maximal fuel energy flow. Assuming a 400kW ICE and that you can achieve same efficiency at reduced fuel flow (which is probably not possible), you get around 180kW out of the ICE. This allows you to recover 'only' 130kW from the MGU-K. (This all assumes that the engine power in the rule refers to the PU power, which I think most people here assume.)
Wouldn't the same be realized if they reduce throttle pressure, for example to 50kW and then the rest can harvested?
Seems like it would be more intuitive but maybe harder to get correct every lap.
There is rule C5.2.5, which limits fuel energy flow at partial load:
At partial load, the fuel energy flow must not exceed the limit curve defined below:
EF (MJ/h) = 380 when the engine power is equal to or below −50kW
EF (MJ/h) = 9.78 x engine power (kW) + 869 when the engine power is above −50kW
Basically, at 50kW you ony get 1358MJ/h, so ~45% of the maximal fuel energy flow. Assuming a 400kW ICE and that you can achieve same efficiency at reduced fuel flow (which is probably not possible), you get around 180kW out of the ICE. This allows you to recover 'only' 130kW from the MGU-K. (This all assumes that the engine power in the rule refers to the PU power, which I think most people here assume.)
V8 drag race and circle track builders set P-H around .040in (1mm) with steel rods which in practice is near zero Piston to Head clearance at redline (the goal is to run around 0.1mm running clearance). This isn’t out of the realm at all.
For a typical racing US domestic V8 with a 4.25in bore, 64cc chambers, and a 10cc dome, that’s a change from to 12:1 to 13.9:1.
This has been a “thing” for decades in race engine building. No fancy degrees or materials needed and certaintly not an industry secret.
All engines are limited by piston to head clearance. You can’t modify this, at some point, they meet, and it’s expensive. Now depending on the rods being used, it may matter. For example, on an American V8 drag race engine, aluminum rods may require 1.50mm p-h clearance ambient vs the 1mm for steel rods. Both will end up around .1mm near redline if you’re doing it right. Both will measure slightly different geometric compression ratios (aluminum being lower) but the same running compression ratio.
Binotto as an engine guy should know this. People building engines in their garages who struggled through high school even know this. This sounds more like sour grapes than anything.
It largely said what I have said over a few posts, just with a lot more words.
Interesting he brings up “dynamic compression” which basically calculates compression ratio starting at the crank angle at intake valve closing (IVC). This thought comes from the 2 stroke world where they don’t have valves and the engine can’t begin compressing the mixture until the piston closes off the ports. On a 4 stroke it’s a little bit misleading as once the engine is “on song”, cylinder pressure is above 1 atmosphere before intake valve closing (IVC) as the inertia of air against a rapidly closing intake valve raises port pressure, so compression is occuring to a small amount prior to IVC.
A certain and controversial performance authorhas coined “effective compression ratio” as “dynamic” and has tried to correlate to octane needs for a given combination. This is wrong as octane needs are driven by lots of things like peak firing cylinder pressure, turbulent kinetic energy (TKE), plug position, atomization (and its effect on the mixture temp in the cylinder), etc.
There is nothing dynamic about “dynamic compression ratio”.
Further complicating things is on a Miller Cycle engine, which F1 engines and some of the diesel LeMans engines before 2014 were, closes the intake valve before BDC on the intake stroke. This means the engine has a higher expansion ratio than compression ratio, which in turn lowers cylinder temperatures. This was used by Mazda and Subaru in the early 90s, still used in locomotive engines. It requires big boost / high air flow from the turbo or supercharger to make up for lack of open time of the intake valve. Pat does a great job describing it here starting at 13:00 . As he points out, by closing the intake valve so early you do lose some of the effect of a longer intake period adding in cylinder motion in the cylinder (typically tumble on a 4 valve head), or when you factor in a few more things, TKE. So that’s why thints like turbulent jet ignition (TJI) are sought out. Honda has a good white paper published this past September about developing TJI systems for large bore sport bike engines, why you want it (the jets increase TKE and create a larger flame surface area, thus reducing knock, and allowing for a higher geometric compression ratio for a given octane), but they also point out it struggles at part throttle operation and is part why you haven’t seen it widely adopted on the street, but I digress…
The Wikipedia and subsequently the AI searches that have trained on the wiki part are wrong about the Miller Cycle. Overall, as he brings it up in the video, the dynamic compression ratio isn’t entirely well explained and it just felt like he was dropping it in there to sound smarter, and also has no idea what it means.
Yep - dynamic compression ratio is a big nothing in the context of this conversation. Miller cycle (early IVC) is simply a means of controlling DCR - it reduces DCR in fact.
The geometric CR limit of 16:1 has nothing to do with limiting how much the engines are permitted to compress the charge - the Miller timing is already being used by the teams to deliberately limit this.
The GCR limit is actually about limiting the "Expansion Ratio" which limits thermal efficiency. We all know the Otto cycle efficiency is limited by compression ratio but this is misleading because the Otto cycle assumes compression ratio = expansion ratio and it is the expansion ratio that is critical.
It largely said what I have said over a few posts, just with a lot more words.
Interesting he brings up “dynamic compression” which basically calculates compression ratio starting at the crank angle at intake valve closing (IVC). This thought comes from the 2 stroke world where they don’t have valves and the engine can’t begin compressing the mixture until the piston closes off the ports. On a 4 stroke it’s a little bit misleading as once the engine is “on song”, cylinder pressure is above 1 atmosphere before intake valve closing (IVC) as the inertia of air against a rapidly closing intake valve raises port pressure, so compression is occuring to a small amount prior to IVC.
A certain and controversial performance authorhas coined “effective compression ratio” as “dynamic” and has tried to correlate to octane needs for a given combination. This is wrong as octane needs are driven by lots of things like peak firing cylinder pressure, turbulent kinetic energy (TKE), plug position, atomization (and its effect on the mixture temp in the cylinder), etc.
There is nothing dynamic about “dynamic compression ratio”.
Further complicating things is on a Miller Cycle engine, which F1 engines and some of the diesel LeMans engines before 2014 were, closes the intake valve before BDC on the intake stroke. This means the engine has a higher expansion ratio than compression ratio, which in turn lowers cylinder temperatures. This was used by Mazda and Subaru in the early 90s, still used in locomotive engines. It requires big boost / high air flow from the turbo or supercharger to make up for lack of open time of the intake valve. Pat does a great job describing it here starting at 13:00 . As he points out, by closing the intake valve so early you do lose some of the effect of a longer intake period adding in cylinder motion in the cylinder (typically tumble on a 4 valve head), or when you factor in a few more things, TKE. So that’s why thints like turbulent jet ignition (TJI) are sought out. Honda has a good white paper published this past September about developing TJI systems for large bore sport bike engines, why you want it (the jets increase TKE and create a larger flame surface area, thus reducing knock, and allowing for a higher geometric compression ratio for a given octane), but they also point out it struggles at part throttle operation and is part why you haven’t seen it widely adopted on the street, but I digress…
The Wikipedia and subsequently the AI searches that have trained on the wiki part are wrong about the Miller Cycle. Overall, as he brings it up in the video, the dynamic compression ratio isn’t entirely well explained and it just felt like he was dropping it in there to sound smarter, and also has no idea what it means.
Yep - dynamic compression ratio is a big nothing in the context of this conversation. Miller cycle (early IVC) is simply a means of controlling DCR - it reduces DCR in fact.
The geometric CR limit of 16:1 has nothing to do with limiting how much the engines are permitted to compress the charge - the Miller timing is already being used by the teams to deliberately limit this.
The GCR limit is actually about limiting the "Expansion Ratio" which limits thermal efficiency. We all know the Otto cycle efficiency is limited by compression ratio but this is misleading because the Otto cycle assumes compression ratio = expansion ratio and it is the expansion ratio that is critical.
Good post, Grunt. Don’t worry, no one will read ourn posts anyway and keep arguing things that don’t matter
