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

[hightower99]

On the feeling torque agenda - is an engines responsiveness anything to do with instantaneus torque? In my car i know the engine is struggling when i lose the ability to swiftly increase the engine speed with the throttle, suggesting no more pulling ability left.

Short answer: No... Longer answer: The responsiveness of the engine is basically related to the surplus amount of power the engine can produce compared to the amount of work you are asking it to do. If you are traveling at a high speed and cruising in a high gear at low rpm then suddenly step on the gas without downshifting then you are putting as much power as the engine is making into acceleration. This acceleration requires a great deal of power and therefore the engine will only be able to accelerate slowly. Think about this when you are standing still and you are in neutral and you step on the gas pedal, the engine only has to accelerate the weight of the engine's internals and therefore it can increase revs very quickly. As soon as you put it in gear you are moving the entire drivetrain as well as the weight of the car and any wind resistence. Then more power is used to move everything so you can't accelerate as fast. It all has to do with power... not torque.

Since power comes from 1)displacement 2)torque 3)engine speed more low down power is technically more torque. Also, objectively speaking, a flat torque curve would suggest a linear power curve, hence linear acceleration (at low speeds, before exponential wind resistance effects de-linearise the system) can be observed. Compare this with a peaky NA engine or a HP turbo engine where torque comes in surges the acceleration also hapens in surges. The differences may be very subtle...just a thought mate

Yes more torque is needed at low rpm to create more low rpm power. My point is that you feel the power. The power is what moves you. The torque is just one variable along the way. The problem is that at low rpm it takes alot of torque to make a little power. That is why people like to say they feel the torque at low rpm because otherwise they end up saying "yeah you can really feel that 50hp off the line!" and that just doesn't sound as good as "Man 260lbs-ft. of torque off the line rocks!"

[Matra et Alpine]

theres always a simple solution.........

never such a thing as "simple" solution to complex problems.
Radials have major vibration issues and the combustion vibration being the most difficult to counter

btw TORQUE gets you moving, power keeps it.

[jediali]

never such a thing as "simple" solution to complex problems.
Radials have major vibration issues and the combustion vibration being the most difficult to counter

btw TORQUE gets you moving, power keeps it.

there was a hint of sarcasim in my reply there! Yep torque moves you, power gets you there quickly.

Hey Matra do you know the (main) difference between the 189 and 228 bhp rx-8 engine? i will tell you - the intake port is longer on the lesser power version - which produces more torque (because a steady heavier mass of intake air ensures better cylinder filling and hence better mean effective pressure which is essentially torque). Consider the rotary with a variable intake, that would give you the best of both worlds. awesome

[hightower99]

there was a hint of sarcasim in my reply there! Yep torque moves you, power gets you there quickly.

Hey Matra do you know the (main) difference between the 189 and 228 bhp rx-8 engine? i will tell you - the intake port is longer on the lesser power version - which produces more torque (because a steady heavier mass of intake air ensures better cylinder filling and hence better mean effective pressure which is essentially torque). Consider the rotary with a variable intake, that would give you the best of both worlds. awesome

the high power model has a 3 stage variable length intake system... and of interest is the fact that one of the intake tracts that opens on the highpower version is longer than the others... and this extra intake tract isn't on the lower power version...

Torque doesn't move you and to prove it I ask a simple question...

How much torque does an engine need to make to accelerate to 60km/h in 10 seconds while hauling 3000kg in a trailer...

I can tell you roughly how much power it is gonna take...

Bet you can't tell me how much torque....

[Matra et Alpine]

Hey Matra do you know the (main) difference between the 189 and 228 bhp rx-8 engine? i will tell you - the intake port is longer on the lesser power version - which produces more torque (because a steady heavier mass of intake air ensures better cylinder filling and hence better mean effective pressure which is essentially torque). Consider the rotary with a variable intake, that would give you the best of both worlds. awesome

I've the full technical presentations for Mazda engineers
It's more complex than that. The 231 engine has an extra intake port for each rotor. It also has two adjustements it does make to effective intake length. The 190 only has one.
The Variable Dynamic Effect Intake Valve effectively shortens the intake at highest revs but also cross links the rotors to use the pressure pulses to effectively charge the opposing intake.
If you are interested I could send you the stuff but it's about 80Mb
Having seen the Le Mans engine, fully variable intake would be a challenge to fit under the bonnet

[Matra et Alpine]

Bet you can't tell me how much torque....

and so how much "power" does it take to initally MOVE the vehicle ?
THey are both a necessary "evil" to take the closed-system of a vehicle at rest accelerating

[hightower99]

I forgot to say the the car weighs 1000kg in the example...


What are you talking about "how much power does it take to initially move" That is totally irrelevant because I can tell you how much is needed to do the entire task...

End v=16.67m/s
Kinetic energy of a mass of 4000kg moving at 16.67m/s is 555777.8J
That amount of energy was accumulated over 10 seconds which requires a total constant power output of 55.57778kW

That of course is the highly simple version to make it more accurate there should be friction taken into account, the fact that the acceleration in real life isn't linear, differing output from the motor, ect. But again the point was that there is simple math for this and no math for figuring out what torque the engine needs to make because that is highly dependant on engine rpm and gearing...


So have I made my point clear yet?

Power moves things....

Torque doesn't

PS. I hope everybody gets the point of my example... That it doesn't matter how much torque you make as long as you are getting a constant 55.57778kW out you can do it. I mean if the vehicle had a CVT then the torque could (reasonably) be anywhere from 49lbs-ft. at 8000rpm to 391lbs-ft. at 1000rpm.

[Matra et Alpine]

The application of TORQUE moves things. Over a period of time gives you the power.
They are related through formula.

To answer your question .... consider this ..... if YOU provide a TORQUE of 1Nm for an hour it will barely move the car. If now provide a TORQUE of 3600Nm for one second it will launch forward. DO the calculation that is BOTH the same "power"

A gearbox is a TORQUE conversion mechanism NOT "power".
Consider why

[Matra et Alpine]

i will tell you - the intake port is longer on the lesser power version - which produces more torque

Here you go, I extracted the animation from the training material.

The extra intake power and the extra valve are shown operating.....

[jediali]

all that stuff he said

i trusted wrong sources on the rx-8, my apologies. Its even more interesting than i thought though, thanks for telling us Matra and HighT.

[hightower99]

The application of TORQUE moves things. Over a period of time gives you the power.
They are related through formula.

To answer your question .... consider this ..... if YOU provide a TORQUE of 1Nm for an hour it will barely move the car. If now provide a TORQUE of 3600Nm for one second it will launch forward. DO the calculation that is BOTH the same "power"

A gearbox is a TORQUE conversion mechanism NOT "power".
Consider why

Torque in itself doesn't move anything... You need to have the time componant to do anything therefore power is what moves you.

I would point out that your example is missing so pretty vital information. Where am I exerting the torque? in relation to what? If I exerted this torque on the car's CoG nothing would happen in either case.

My question was to figure out how much torque the engine needs to generate to move the vehicle you can't tell me this... therefore engine torque (not Physical Torque in a general sense) is pretty irrelevant.

Consider that gearboxes don't effect power (it doesn't matter what gear you are in the same power is always available).

[Matra et Alpine]

Torque in itself doesn't move anything... You need to have the time componant to do anything therefore power is what moves you.

correct, hence why I explained that with a time component

I would point out that your example is missing so pretty vital information. Where am I exerting the torque? in relation to what? If I exerted this torque on the car's CoG nothing would happen in either case.

That's being deliberatley obtuse.
COmmon sense says it' sapplied in the drive train. You can argue whether it is at the wheel, in the diff, the clutch , the gearbox the crank. Whatever. The principle stands. 1Nm of torque ain't going to do much

My question was to figure out how much torque the engine needs to generate to move the vehicle you can't tell me this... therefore engine torque (not Physical Torque in a general sense) is pretty irrelevant.

Even more obtuse.
It's "easy" answer. You just have to let us know the coefficent of fricton on the tyres, drivetrain and the gear ratios a clutch "slip" at start and rate of change. For accuracy then we need rolling friction, Cd and frontal area. Then it's dead easy

Consider that gearboxes don't effect power (it doesn't matter what gear you are in the same power is always available).

and so the point is MADE.
BTW, you need an engine with a compeltely flat power curve from 0 to max revs for your premise to be even remotely accurate

[pneumatic]

I think the Torque vs Power discussion should be taken to a different thread. It is subjective and will go on forever.

Brad,

Just fill in the blanks below so we know what your saying with regards to economy.

At 2000rpm the engine uses ____L/min of fuel to make _____HP.

At 4000rpm the engine uses ____L/min of fuel to make _____HP.

From what your saying, the L/min will be the same for each, and the HP is double at 4000rpm.

[jediali]

I think the Torque vs Power discussion should be taken to a different thread. It is subjective and will go on forever.

i agree, and the thread already exists

[revetec]

I have so many questions it hurts...

How can somebody "feel" a "constant torque curve" ???

You don't feel torque you feel the power of the engine accelerating the vehicle right?`

Also I am sure that when people say they want more torque they actually mean to say that they want more low rpm power... so far I haven't been proved wrong in this assumption.... yet...

Next how can the revetec engine produce more torque when running on a lean mixture?

In order for your claims to be true you would have to maintain the same torque at 2000 and 4000rpm but you are saying that you are running on a leaner mixture during 4000rpm operation... How is this possible? I know you are getting "almost" complete combustion (you should be able to get practically complete combustion on lean mix) But if there is less fuel in the chamber then less torque is produced... Max torque is produced with a slightly rich mixture.... Please explain yourself.

I don't understand what you are saying about your lambda readings.... I believe the oxygen sensors measure the amount of oxygen in the exhaust right? well then if the air/fuel ratio is lean for the whole cylinder then the lambda reading would show that. Just because you burn all of the fuel that you do inject doesn't mean that you would get a reading showing 14.7:1... Lambda readings tell you the air/fuel ratio of the whole cylinder (and engine) so running lean and igniting it by concentrating the fuel around the spark plug shouldn't fool the system should it?

I would also like to point out that a slightly more accurate rule of thumb is 3/10 of the burned fuel's energy is produced as output power as motive force to the wheels. 2/10 is lost through the cooling system. This includes the power needed to pump coolant around the system as well as the actual heat energy dissipated by the system. Keep in mind that on an engine producing 150kW motive power, 100kW of energy is lost throught the cooling system. 4/10 is lost as heat and kinetic energy in the exhaust. Exhaust can be as much as 1000 degrees C and is normally over 800 degrees C for normal cars. 1/10 of the burned fuel's energy is lost through heat that doesn't go through the cooling system.

OK, Dynos measure Torque only. Power is a calculation of torque and RPM. High torque at a very low RPM provides good acceleration off the mark. I have posted a dyno graph previously showing a very flat torque curve (Off the output shaft which is two strokes of each piston per rev, same as a conventional engine) without the need for variable cam timing or variable length inlet runners etc.

Normally a lean mixture wont fire correctly losing power. I have explained how we do it and I was even suprised at how effective it does it by controling the volume size when the cylinder is fired...but it does just that. If we richen it up to a standard mixture, the performance drops.

Given a Lambda reading of 14.7:1 and a good emissions reading we then dyno the engine, starting off with this setting. Even though the amount of fuel we have put in is very lean the performance under load is almost optimum at this point. Leaning and richening the mixture drops our performance. What more can I say. This is what we have experienced and this is what our injection is set up to. We have performed fuel consumption tests with an independant auto manufacturer and have confirmed the fuel usage over the total RPM range and until 2,000rpm the fuel usage increases. From 2,000-4,000rpm its about the same. Our fuel map leans off with no effect on performance. Our ignition map is strange too. It likes very high advance at 1,200rpm (40 degrees) thend drops over 2,000rpm to around 25 degrees. Very strange but this is used for optimum output.

As far as heat loss. Our cooling system only needs to be 60% of a conventional engine due to my previous statement about less heat loss through the cylinder walls. Our max exhaust temp on the dyno has been about 380 degrees but in normal oeration it is closer to 280 degrees. So I would say that heat loss is kept to a minimum.