A work of pure genius! - Brilliant "Revetec" Engine

[hightower99]

No one quotes their worst BSFC, only their best.

actualy most info I see is averages, not peak BSFC.

Are you saying that all engine manufacturers have got it so wrong in the areas you have identified?

No I am saying that the single point is not enough to say any one thing is the main reason for the value. everything could be just right for running efficiently at 2000RPM and 450kPa load. Synergy, think synergy.

This is what I thought and conveyed this to Orbital. I was looking for a higher BMEP. They said that at any given output, the lower the figure the better.

Well that is simply not true as there is a certain BMEP that is needed to achieve any given output at any given speed for any given displacement. The calculations are simple either 4*pi*T/V if you want to calculate from torque or 2*P/(f*V) if you want to calculate from power. From this it is easy to see that output has to fall in order to get a lower BMEP. It is possible to decrease the average cylinder pressure while maintaining any given torque (just need to increase mechanical efficiency). But that will not lower the calculated BMEP value.

A lucky set up? hehehehe. You don't think after 100 years of conventional engine development that if it was a lucky set up that it would have been done before?

When I say luckey setup I mean that the synergy of all the variables (including the new bottom-end) is what allows the BSFC. A single point is not enough to confirm that the bottom-end increases efficiency.

So you don't drive on the freeway often?

I spend most of my time on roads with 80km/h speed limits on roads that aren't straight and flat for several km. I would say that the average RPM that my engine sees is somewhere over 3000RPM maybe 3500RPM. I am rarely able to cruise for more than about 1-2 minutes and then I will be cruising at about 2200-2500RPM.

Now that you have a good starting point the goal should be to increase specific power (which will also increase power density) without increasing the BSFC figures.

Edit: I just realised that there is no WOT full rev BSFC figures... I would really like to see that because there is alittle bit of that sort of info on the WWW to compare it to.

[revetec]

Well that is simply not true as there is a certain BMEP that is needed to achieve any given output at any given speed for any given displacement.

Don't get peak performance/output confused with peak efficiency, which you are. A higher BMEP produces more outright performance but the lower the BMEP for a given output provides a greater efficiency. One thing you are not factoring in is the manifold load of the engine at that BMEP figure point.

I spend most of my time on roads with 80km/h speed limits on roads that aren't straight and flat for several km. I would say that the average RPM that my engine sees is somewhere over 3000RPM maybe 3500RPM. I am rarely able to cruise for more than about 1-2 minutes and then I will be cruising at about 2200-2500RPM.

Try changing up a gear or buy a car that is more modern. Most cars I have driven is at around 2,000rpm at 100kph in 5th or 6th gear BTW: My car with a 5.7litre V8 and auto trans sits around 1,500rpm at cruise 100kph.

Edit: I just realised that there is no WOT full rev BSFC figures... I would really like to see that because there is a little bit of that sort of info on the WWW to compare it to.

This is because an engine is most efficient at around 3/4 load and from 3/4 to full throttle the performance gain is not great, but there is a higher fuel consumption. So the figure at full throttle is rarely used or quoted.

Now that you have a good starting point the goal should be to increase specific power (which will also increase power density) without increasing the BSFC figures.

It's the same result as maintaining power and decreasing BSFC figures. Fuel efficiency is all about how much fuel you use to produce each kW per hour. It all comes down to matching an engine to an application. Depending on the vehicle's requirements, you adjust the engine's capacity and characteristic to the vehicle along with final drive and transmission ratios so as the vehicle drives with the best fuel efficiency at the point it will be driven mostly. The standard quoted tests are highway and city cycles.

Take your car for an example. If we were to change your final drive ratio to provide a 100kph cruise whereas you engine is operating at 2,000rpm, the result would be?

Another point I can add is that if we were to use our engine in a power generator type application. The engine will operate at one specific speed. A lower BSFC will provide less fuel consumption per kW-h which makes it more economical to produce electricity from this powerplant regardless of the efficiencies in other RPM ranges. A huge market for us.

[hightower99]

Don't get peak performance/output confused with peak efficiency, which you are. A higher BMEP produces more outright performance but the lower the BMEP for a given output provides a greater efficiency. One thing you are not factoring in is the manifold load of the engine at that BMEP figure point.

I believe you are misunderstanding what I said. Say you have a 2L engine and it produces 200HP (149kW) at 8000RPM, this means it is producing 131.3lbs-ft. of torque (178Nm) at 8000RPM. The calculated BMEP is then: 4*π*178Nm/0.002(m^3)= 1118.4kPa BMEP. Now the only ways to change that figure are: change dispacement or change the torque. As long as it is a 2L engine producing 131.3lbs-ft. (178Nm) of torque then the BMEP is always going to be 1118.4kPa. However the output (I am assuming you mean power?) can be pretty much anything depending on RPM. If you want a lower BMEP for any given output then you need to rev higher, which is not good for efficiency. If you are talking about avg. cyl. pressure vs. torque then that is mechanical efficiency.

Try changing up a gear or buy a car that is more modern. Most cars I have driven is at around 2,000rpm at 100kph in 5th or 6th gear BTW: My car with a 5.7litre V8 and auto trans sits around 1,500rpm at cruise 100kph.

I loath how you try to simplify/generalize everything. I told you what the average RPM is for me and why. Accept it.

This is because an engine is most efficient at around 3/4 load and from 3/4 to full throttle the performance gain is not great, but there is a higher fuel consumption. So the figure at full throttle is rarely used or quoted.

I think you misread what I posted again. I said the info I see on the net is usually WOT BSFC figures. Therefore to make a fair comparison I would have to use WOT figures for your engine.

It's the same result as maintaining power and decreasing BSFC figures.

No it isn't and I thought I explained why... didn't I?

Take your car for an example. If we were to change your final drive ratio to provide a 100kph cruise whereas you engine is operating at 2,000rpm, the result would be?

I can already cruise at 100km/h at about 1900-2000RPM but that is a moot point because I rarely cruise at 100km/h. I either cruise at about 80-85km/h or 115-120km/h and even then I cannot maintain a stable cruise for very long (because of how the road system is designed in Denmark). Personally I think my final drive is abit high.

Another point I can add is that if we were to use our engine in a power generator type application. The engine will operate at one specific speed. A lower BSFC will provide less fuel consumption per kW-h which makes it more economical to produce electricity from this powerplant regardless of the efficiencies in other RPM ranges. A huge market for us.

Well think about that for a moment. You have to maintain the engine at 2000RPM and 450kPa load (the only point where you have proved high efficency) which means that the engine can only make about 86Nm of torque which at 2000RPM means you are only making about 18kW of power. Now knowing that the current market for 18kW generators is around the price range of 3700-4700USD and normally use air or watercooled 1L V-twin engines. Do you think you can price your 2.4L revetec generator competetively? Keep in mind that your engine is barely making 18kW at that point when normally 18kW generators need engines that produce 22-24kW

[GTM]

actualy most info I see is averages, not peak BSFC.

Can you post links or details to examples where they say 'average'?
I find this interesting because whenever I have come across a single BSFC figure that has been quoted by an auto/engine manufacturer they never disclose whether they are 'peak' or 'average'.

[hightower99]

Can you post links or details to examples where they say 'average'?
I find this interesting because whenever I have come across a single BSFC figure that has been quoted by an auto/engine manufacturer they never disclose whether they are 'peak' or 'average'.

Look at the link I posted about the UL 260 aviation engine. It states the average range of BSFC.

[revetec]

Yeah but aircraft engines operate at certain loads which stay consistent for a large percentage of its flight. Just talked to Orbital and they said car manufacturers generally quote their best BSFC because the load and RPM vary greatly throughout the operational range.

[revetec]

I believe you are misunderstanding what I said. Say you have a 2L engine and it produces 200HP (149kW) at 8000RPM, this means it is producing 131.3lbs-ft. of torque (178Nm) at 8000RPM. The calculated BMEP is then: 4*p*178Nm/0.002(m^3)= 1118.4kPa BMEP. Now the only ways to change that figure are: change dispacement or change the torque. As long as it is a 2L engine producing 131.3lbs-ft. (178Nm) of torque then the BMEP is always going to be 1118.4kPa. However the output (I am assuming you mean power?) can be pretty much anything depending on RPM. If you want a lower BMEP for any given output then you need to rev higher, which is not good for efficiency. If you are talking about avg. cyl. pressure vs. torque then that is mechanical efficiency.

So what happens to the BMEP at partial throttle?
Torque decreases and the BMEP decreases.
Look, you are still talking about BMEP at wide open throttle.

The BMEP shows how efficient combustion and the mechanical efficiency of the engine but what it doesn't show is the amount of fuel you are using to achieve it.

This is why BSFC is the real figure to measure efficiency. It actually shows how much fuel per kW-h you are making. This is Efficiency! You can have an engine that produces high BMEP but at what fuel cost.

I loath how you try to simplify/generalize everything. I told you what the average RPM is for me and why. Accept it.

So the way you drive and the conditions you drive under are in line with an average driver worldwide? Guess what hightower99, not one car company is going to tailor make an engine to drive under your specific driving conditions, rather than an average consumer's driving conditions and requirements and the characteristics of the vehicle the engine is planned to be fitted to.

Generalization is a way of making a product suit the majority of consumers and I'm not going to accept the way you drive as a point of testing or development. You will have to accept the above.

I think you misread what I posted again. I said the info I see on the net is usually WOT BSFC figures. Therefore to make a fair comparison I would have to use WOT figures for your engine.

I talked to Orbital and the best BSFC figure is created around 75% manifold load. Go do your homework and quote from a reputable source and let us know where it came from. If you can't do this then stop posting your opinions and start posting some facts you can back up.

I have the luxury of going through independent testing, and you have not. The usual tests are at several RPM and manifold load points determined by the European Drive cycle (NEDC99). The main tested spots are 2 and 3 bar manifold loadings as this is the most common figure driven through in the NEDC99. Most efficiency occurs around the 4.5 bar manifold loading and around 2,000rpm.

I can already cruise at 100km/h at about 1900-2000RPM but that is a moot point because I rarely cruise at 100km/h. I either cruise at about 80-85km/h or 115-120km/h and even then I cannot maintain a stable cruise for very long (because of how the road system is designed in Denmark). Personally I think my final drive is abit high.

I'm sorry your road system doesn't allow you to cruise at 100kph for extended periods of time. Denmark doesn't seem to be a good region to quote as an average of the world does it?

Well think about that for a moment. You have to maintain the engine at 2000RPM and 450kPa load (the only point where you have proved high efficency) which means that the engine can only make about 86Nm of torque which at 2000RPM means you are only making about 18kW of power. Now knowing that the current market for 18kW generators is around the price range of 3700-4700USD and normally use air or watercooled 1L V-twin engines. Do you think you can price your 2.4L revetec generator competetively? Keep in mind that your engine is barely making 18kW at that point when normally 18kW generators need engines that produce 22-24kW

How about we get a 18kW generator engine and stick it in your car for you to drive. What do we achieve from even contemplating this?

If we were to build a generator for a landfill emission project the engine is far more cost than what you have quoted. Anyways I can expect us to be competitive in price on an engine and the savings on generating more power with the same amount of fuel would pay for any increase in initial cost if there was, not to mention the carbon credits gained from such a application.

[GTM]

Look at the link I posted about the UL 260 aviation engine. It states the average range of BSFC.

You said 'averages', I didn't think you were referring to just one engine?

I asked this question because if you had a few examples that quoted auto engines with 'average' BSFC and not peak then we could reasonable assume that the average 'BSFC' figure is also used to quote engines performance characteristics.

[clutch-monkey]

a question for the future:
how would this engine react to forced induction? how hard would it be to set it up?
or have i completely missed the point somewhere?

[Matra et Alpine]

I loath how you try to simplify/generalize everything. I told you what the average RPM is for me and why. Accept it.

SOMe of uas share that loathing.

But what we loathE is that you won't just sit back, take the facts from the engine runs Revetec have doen and fine inquire about other stuff, but beyond that stop the interrogation !!

Still waiting for your own engine design thread !!

[hightower99]

Yeah but aircraft engines operate at certain loads which stay consistent for a large percentage of its flight. Just talked to Orbital and they said car manufacturers generally quote their best BSFC because the load and RPM vary greatly throughout the operational range.

Well I don't have access to that info. This is some of the info I have found:



That would be 2 WOT BSFC and a proper BSFC map.

[hightower99]

So what happens to the BMEP at partial throttle?
Torque decreases and the BMEP decreases.

Of course it does... Did I say it didn't?

The BMEP shows how efficient combustion and the mechanical efficiency of the engine but what it doesn't show is the amount of fuel you are using to achieve it.

Yeah I know...

This is why BSFC is the real figure to measure efficiency. It actually shows how much fuel per kW-h you are making.

Yeah knew that too. In fact I was the one who said that you should show BSFC figures because BMEP is not directly in relation with thermal efficiency.

So the way you drive and the conditions you drive under are in line with an average driver worldwide?

No. But I drive like most danes do. I think you are reading too much into this, I just stated that the average RPM you stated didn't relate properly to me or most driving danes.

Generalization is a way of making a product suit the majority of consumers and I'm not going to accept the way you drive as a point of testing or development.

Did I ask you to accept the way I drive as a point of testing or developement? No I simply said that you should except that I do not sit on the average (instead of suggesting ways that I should change so that I do sit at average).

I talked to Orbital and the best BSFC figure is created around 75% manifold load.

Thats all good and well but the info I have is based on WOT. Besides if your bottom-end technology is actually helping to achieve the efficiency then it should also show under WOT testing.

I'm sorry your road system doesn't allow you to cruise at 100kph for extended periods of time. Denmark doesn't seem to be a good region to quote as an average of the world does it?

I'm not sorry. I would much rather have an eventfull dynamic journey then droning on at 100km/h. Besides if I have to go far I can cruise at 130km/h (legally)

SOMe of uas share that loathing.

But what we loathE is that you won't just sit back, take the facts from the engine runs Revetec have doen and fine inquire about other stuff, but beyond that stop the interrogation !!

Still waiting for your own engine design thread !!

I wasn't aware I was interrogating anyone

I do except the actual data that the tests showed, I do not question that at all. I question the statement made that a single point proves the revetec engine to be extremely efficient (beyond a doubt...?).

I disapprove of Simpsons Tiger-repellant-stone logic.

[Matra et Alpine]

Do you understand what an "interrogation" is ?
You say you don't and then quiz on almost every sentence that had been written - ROLFMAO

hmmm, I like the comaprison of your engine building skills and activities to Tiger Repellent........Yep, your engine ideas DO work

[hightower99]

Do you understand what an "interrogation" is ?
You say you don't and then quiz on almost every sentence that had been written - ROLFMAO

It's funny how a single question is construed as "quiz on almost every sentence that had been writen"... LOLZORZ!

hmmm, I like the comaprison of your engine building skills and activities to Tiger Repellent........Yep, your engine ideas DO work

You must be drunk or something

I said nothing of my ability to design anything... I didn't even mention my engine idea yet you somehow connect that to a reference that you don't understand?

The simpsons tiger-repellent-stone logic is as follows:

Lisa: Dad, by that logic I could say that this stone is keeping the tigers away
Homer: How does it work?
Lisa:It doesn't it's just a rock
Homer:Oh?
Lisa:But do you see any tigers around?
Homer:Lisa I would like to buy your rock...

*Simpsons is a popular american animated series...

[revetec]

Well I don't have access to that info. This is some of the info I have found:




That would be 2 WOT BSFC and a proper BSFC map.

Come on.....The engine data images you posted were forced induction. (I assume the 1st one was even though I can't find data on it, the BMEP was 150?)

The first image you posted above - The R26B engine is a turbocharged quad rotor, rotary race engine. Post something that is normally aspirated and in production for consumer use for comparison.

A quote from Wikipedia.... "The engine design originates as a single 13B with: an additional rotor and housing added at each end, continually variable geometry intakes, and an additional (third) spark plug. The R26B's rotor housing can be purchased at retail from Mazdaspeed, but no internal parts are available to the general public."

The second MEP graph was a supercharged Mercedes engine. Post something that is normally aspirated for comparison.

Note: The supercharged Mercedes engine's best BSFC was around 250g/kW-h. Our best was 17% better or 6.8% better in total efficiency at our peak and normally aspirated. Forced induction decreases the total percentage lost in pumping losses as apposed to power gains.