Your thoughts please

wammers · Jul 18, 2014

martynv8 said:
Surprised myself how quickly I can lose a huge amount of respect for someone in so little time.

Then concentrate on your subject and leave others to theirs. People like you who know little and say much are dangerous on this site.

StuckAgainSteve · Jul 19, 2014

Datatek said:
The amount of air inducted is governed by the throttle opening, not the cylinder size. Mixture ratio for a given amount of air is govened by the ECU.
A long stroke engine of a given capacity will produce more torque for a fixed amount of fuel than the same capacity short stroke engine.

It's not just about torque a tiny tweak of an engine design changing the crank (and conrod) angle (the implications of the modified stroke) can make or destroy the engine's efficiency - according to Wammer's simplistic "bigger engine = more fuel" theory the 4.6 SHOULD be 13% more thirsty as it's 13% bigger on the same gearing - the fact it's only a percent or two behind on (useless) rolling road tests tells you all you need to know - almost identical engine designs can differ greatly on how efficient they are at turning fuel into energy at the crank and having driven thousands of miles in both a 4 litre and 4.6 p38 I can say with my driving style fuel economy was practically indistinguishable. The 4.6 is clearly a much more efficient engine in the real world. It's the same in the A-series world, the 1275 engine was by far the most thermodynamically efficient engine in the range - cruise economy usually bettered the smaller engines. Rolling road tests would undoubtedly paint a different picture.

Now if we could get rid of stupid catalytic converters and run engines as lean as they'll run without any need to keep a cat happy (just a particulate filter to soak up the increased NOx) - we'd see some remarkable results with today's ultra precise, multi stage fuel injection systems. Ultra lean burn NA petrols effectively running as compression-ignition petrols on light loads. These would have to be fairly large capacity to make enough power to cruise in the "controlled detonation" stage where you'd be extracting maximum cylinder pressure from minimum amounts of fuel. I wouldn't be surprised if 100+mpg from a 2 litre four cylinder would be possible.

Saint.V8 · Jul 19, 2014

StuckAgainSteve said:
It's not just about torque a tiny tweak of an engine design changing the crank (and conrod) angle (the implications of the modified stroke) can make or destroy the engine's efficiency - according to Wammer's simplistic "bigger engine = more fuel" theory the 4.6 SHOULD be 13% more thirsty as it's 13% bigger on the same gearing - the fact it's only a percent or two behind on (useless) rolling road tests tells you all you need to know - almost identical engine designs can differ greatly on how efficient they are at turning fuel into energy at the crank and having driven thousands of miles in both a 4 litre and 4.6 p38 I can say with my driving style fuel economy was practically indistinguishable. The 4.6 is clearly a much more efficient engine in the real world. It's the same in the A-series world, the 1275 engine was by far the most thermodynamically efficient engine in the range - cruise economy usually bettered the smaller engines. Rolling road tests would undoubtedly paint a different picture.

Now if we could get rid of stupid catalytic converters and run engines as lean as they'll run without any need to keep a cat happy (just a particulate filter to soak up the increased NOx) - we'd see some remarkable results with today's ultra precise, multi stage fuel injection systems. Ultra lean burn NA petrols effectively running as compression-ignition petrols on light loads. These would have to be fairly large capacity to make enough power to cruise in the "controlled detonation" stage where you'd be extracting maximum cylinder pressure from minimum amounts of fuel. I wouldn't be surprised if 100+mpg from a 2 litre four cylinder would be possible.

Thats what I said - the 4.6 closes the theoretical gap by being more work efficent!

wammers · Jul 19, 2014

StuckAgainSteve said:
It's not just about torque a tiny tweak of an engine design changing the crank (and conrod) angle (the implications of the modified stroke) can make or destroy the engine's efficiency - according to Wammer's simplistic "bigger engine = more fuel" theory the 4.6 SHOULD be 13% more thirsty as it's 13% bigger on the same gearing - the fact it's only a percent or two behind on (useless) rolling road tests tells you all you need to know - almost identical engine designs can differ greatly on how efficient they are at turning fuel into energy at the crank and having driven thousands of miles in both a 4 litre and 4.6 p38 I can say with my driving style fuel economy was practically indistinguishable. The 4.6 is clearly a much more efficient engine in the real world. It's the same in the A-series world, the 1275 engine was by far the most thermodynamically efficient engine in the range - cruise economy usually bettered the smaller engines. Rolling road tests would undoubtedly paint a different picture.

Now if we could get rid of stupid catalytic converters and run engines as lean as they'll run without any need to keep a cat happy (just a particulate filter to soak up the increased NOx) - we'd see some remarkable results with today's ultra precise, multi stage fuel injection systems. Ultra lean burn NA petrols effectively running as compression-ignition petrols on light loads. These would have to be fairly large capacity to make enough power to cruise in the "controlled detonation" stage where you'd be extracting maximum cylinder pressure from minimum amounts of fuel. I wouldn't be surprised if 100+mpg from a 2 litre four cylinder would be possible.

How many petrol cars do you know of fitted with particle filters? Particle filters don't trap NOx. They trap soot on diesel engines created by use of EGR to reduce combustion temperatures to prevent NOx production. NOx is a gas not a solid.

StuckAgainSteve · Jul 19, 2014

wammers said:
How many petrol cars do you know of fitted with particle filters? Particle filters don't trap NOx. They trap soot on diesel engines created by use of EGR to reduce combustion temperatures to prevent NOx production. NOx is a gas not a solid.

You'd better tell this company they're wasting their time dry-filtering NOx emissions. NOx Filter, NOx Reduction, Ceramic Filters, Catalyst Filters

TCubed · Jul 20, 2014

StuckAgainSteve said:
You'd better tell this company they're wasting their time dry-filtering NOx emissions. NOx Filter, NOx Reduction, Ceramic Filters, Catalyst Filters

It does specify that the nitrous oxides are removed via catalysts. Wammers is right; gases cannot be filtered out, at least certainly not without almost stopping the flow; they're reacted out. Check out Top Gear 13x05 for an interesting albeit impractical chemical method to completely remove CO2 from a supercharged Jag (they run the exhaust over calcium oxide).

200tdi ayre · Jul 20, 2014

The moment you realise a RV8 uses more fuel than this ....

http://www.brabus.com/cars4sale/car_6x6_white.html

StuckAgainSteve · Jul 20, 2014

TCubed said:
It does specify that the nitrous oxides are removed via catalysts. Wammers is right; gases cannot be filtered out, at least certainly not without almost stopping the flow; they're reacted out. Check out Top Gear 13x05 for an interesting albeit impractical chemical method to completely remove CO2 from a supercharged Jag (they run the exhaust over calcium oxide).

Yeah I probably used a crap link but there are dry not catalyst filtration systems for NOx like this https://web.anl.gov/PCS/acsfuel/preprint archive/Files/41_1_NEW ORLEANS_03-96_0298.pdf

Rover were cocking about with them over 25 years ago trying to make their ultra lean burn project clean - the engine that became the k-series after the forced adoption of catalytic converters ruined their project.

TCubed · Jul 20, 2014

StuckAgainSteve said:
Yeah I probably used a crap link but there are dry not catalyst filtration systems for NOx like this https://web.anl.gov/PCS/acsfuel/preprint archive/Files/41_1_NEW ORLEANS_03-96_0298.pdf

Rover were cocking about with them over 25 years ago trying to make their ultra lean burn project clean - the engine that became the k-series after the forced adoption of catalytic converters ruined their project.

It's still a chemical reaction though. Forgive me if I misinterpreted but I took your "filtering" as a method to stop and extract the NOx before it reached the atmosphere but not actually chemically modify it. This wouldn't work for the simple reason that there's only so much you can back up before you have to change the filter paper

That paper describes some interesting chemistry of using carbon as the catalyst but it is still a chemical reaction. They do describe dissolving the NO and NO2 in alkali water, which technically is a filter, but that's not especially helpful from an environmental view point as it just delays the emissions rather than reduces them.
I'm unsure of the efficiency of C as a catalyst for this process but I would expect the transition metal complexes currently used would be more efficient albeit much more expensive.

Your thoughts please

wammers

No longer with us, RIP

StuckAgainSteve

Well-Known Member

Saint.V8

Dyed-in-the-wool 100% RR Junkie

wammers

No longer with us, RIP

StuckAgainSteve

Well-Known Member

TCubed

Active Member

200tdi ayre

Well-Known Member

StuckAgainSteve

Well-Known Member

TCubed

Active Member

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