Hp displacement ratio

[hightower99]

I was reffering to nota's post about RC engines. Each one of those manufacturers use a different dyno test so their numbers are basically meaningless. The only thing that maters with those tiny engines is their real world performance. Most RC car engines have a true amount of power that is about 60-80% less than the manufacturers claim

Where did you get that information?

I don't race RC cars but I talk to some people who do and they say that the manufacturer's claims are almost always about 10-20% lower than what the engines make.

[derekthetree]

I hope you realise that forces tend to increase linearly with increases in weight and porportionaly with increases in speed...

i think you will find that force tends to increase proportionally with an increase in the rate of change of velocity and with increases in mass, not weight.

[Slicks]

yes. but others and i are saying that a large engine, revving slower will consume more fuel than a smaller engine revving higher.

And Im saying you have no proof of that, there are too many variables.

because their overall power and torque are poor

Good job.
So again, can anyone explain to me how hp/l is relevant in comaparing engines in the real world?

[Slicks]

Slicks you need to relax everyone here KNOWS that HP/L ratings doesn't mean anything and that it doesn't make one engine better than another...

Unfortunetly most of the Europeans here do think it matters.

But some people think that you think that FI sucks because in you POV it increases HP/L (It doesn't FI increase the "true" displacement of an engine without a physically larger block)

Then those people are not intelligent.

I know you aren't against high HP/L engines you are against the dumb guys who think that there S2000 with it's 120HP/L can take anything...

I for one agree with you!

Thank you.
Im glad there is atleast one person on here that knows WTF is going on.

[jediali]

fuel consumption comes down to the engines several efficiencies
1) mechanical efficiency, how much friction does it produce (from revving high or a s/c eg)
2)fuel efficiency, how high is the comp. ratio...
3)indicated(or air cycle) efficiency, how well is the otto cycle implemeted

then there is possible heat loss (how much heat loss through combustion chamber, timing loss, exhaust blowdown loss, pumping loss

sorry to be technical but i think optimising these issues seperaetley creates a fuel efficient engine,

p.s. people should like the s2000 for its character and power delivery, not getting confused because its crappy torque output makes it slower on paper and then thinking power is everything - its just not that simple!

[Slicks]

p.s. people should like the s2000 for its character and power delivery, not getting confused because its crappy torque output makes it slower on paper and then thinking power is everything - its just not that simple!

Whats there to like about its power delivery?
What were talking about is the fanboys who say things like "OMG the s2k's engine is so high tech omg, if honda made a 5.7L engine is would be making over 570hp like no wai omg!"
The most ironic part about the whole ordeal is that Honda increased the displacement of the F20 without bumping up hp, because owners were unsatisfied with the lack of low end and mid range power.

[jediali]

Whats there to like about its power delivery?
What were talking about is the fanboys who say things like "OMG the s2k's engine is so high tech omg, if honda made a 5.7L engine is would be making over 570hp like no wai omg!"
The most ironic part about the whole ordeal is that Honda increased the displacement of the F20 without bumping up hp, because owners were unsatisfied with the lack of low end and mid range power.

if youve got a bone to pick leave me out , im more technically orientated and neutral. start a new thread asking about power delivery characteristics because i only know what ive heard

[The_Canuck]

You do realise that those numbers are the manufacturers claims and that those manufacturers have no set standard across their industry.

Yes they do...
I've only read the first page...

[Slicks]

if youve got a bone to pick leave me out , im more technically orientated and neutral. start a new thread asking about power delivery characteristics because i only know what ive heard

No bone to pick. So you like it when you have to rev past 6000RPMs to pass traffic? Like I said, Honda increased the displacement for that very reason, to get better power delivery(not just up high power), which was the S2Ks biggest flaw.

[nota]

I was reffering to nota's post about RC engines.

I wouldn't claim to know the first thing about RC engines, nor did I in my single post. However you seem intent on parading your obvious expertise on the subject, and to my expense. I can only guess that the subject of RC cars must be very important to your life

Each one of those manufacturers use a different dyno test so their numbers are basically meaningless. The only thing that maters with those tiny engines is their real world performance

I won't pretend to be an expert on dynos or measurable output either, but since you do seem content in your expertise to lecture me from on-high, would you confirm that different dynometer brands (eg Dynojet vs Dyno Dynamics) are also different tests, since they obtain different test figures when measuring the exact same engine? Therefore with "no set standard across their industry" these differing dyno test results according to your logic must (in your own words) also be "meaningless"

Really?

Most RC car engines have a true amount of power that is about 60-80% less than the manufacturers claim

"You do realise" that the kW figure I was citing relates not to "most RC car engines" but instead the absolute apogee of their genre?

Recently IFMAR ran a WC round in Queensland, and our most reputable car-mag ran a six page spread which was my info source. 'Wheels' interviewed and quoted several experts including World Championship-winning drivers, automotive engineers & mechanics (all full-time RC professionals) along with the manufacturer-principal of chassis manufacturer Serpent etc

Whom should I believe to be more of an accurate and reputable authority as regards RC cars? Should I trust you - an internet poster calling himself 'SIMPLETON' - or some of the actual designers, the automotive engineers, the world-champion drivers, and those ISO-accredited engine manufacturers themselves?

[culver]

no, if you put an engine alone on a test bed, a larger capacity engine will consume more fuel per unit time per revolution than a smaller capacity engine.

that generalised enough?

That generalization is true but that larger engine will also produce more power at the same revs as the smaller engine (again a generalization). So if we want the same power from a smaller motor it must turn faster. Unfortunately turning a smaller motor faster hurts it's mechanical efficiency. Mechanical efficiency is how much power is left to do work after we use finish pumping gas in and out of the cylinder and factor in friction, this is not the same as the thermal efficiency of the motor. At WOT the mechanical efficiency of an engine ranges from about 90% at lower RMP (1800-2400) to about 75% at higher rpm. These values decrease as the engine it throttled. They are 0% at idle.* Basically an automobile engine is mechanically more efficient at lower RPM. All else being equal your efficiency is better if you run a larger engine at lower RPM.
There are lots of other generalizations that dictate actual vehicle mileage. Either way, larger displacement (with in reason) does not necessitate lower mileage.

*John B Heywood, Internal Combustion Engine Fundamentals

[770]

Turbine engines/Turbo Prop engines supposedly have the most power for their total size. A job for Myth Busters?

[Rockefella]

Turbine engines/Turbo Prop engines supposedly have the most power for their total size. A job for Myth Busters?

That'd be a weird myth to confirm/bust..

[Quiggs]

<insert Saturn V rocket picture here>

I win.

[hightower99]

i think you will find that force tends to increase proportionally with an increase in the rate of change of velocity and with increases in mass, not weight.

You understood what I meant right...

Sorry for the odd wording but we all know F=Mx(AxA)