Warp Speed wrote: ↑Sun Oct 22, 2017 7:25 pm
How many of those equal power pulses are produced during the same amount of time between the two examples?
If you apply more of the same size "power pulses " within a given time the average power out put has increased which is not the original question as both are said to be the same power capability (op I mean )
That is at the flywheel, with a constrained acceleration rate. We are talking at the tire with the proper gear ratio for each example. You can either up the power, or up the rpm the power is made at to accelerate a vehicle quicker.
Now that I re read it, I think you just answered your own question.
Warp Speed wrote: ↑Sun Oct 22, 2017 7:25 pm
How many of those equal power pulses are produced during the same amount of time between the two examples?
If you apply more of the same size "power pulses " within a given time the average power out put has increased which is not the original question as both are said to be the same power capability (op I mean )
That is at the flywheel, with a constrained acceleration rate. We are talking at the tire with the proper gear ratio for each example. You can either up the power, or up the rpm the power is made at to accelerate a vehicle quicker.
Now that I re read it, I think you just answered your own question.
That isnt correct you either up the rear wheel torque (force st the tire ) at the expense of speed capability using increase in gear or you reduce the rear wheel torque with less gear to hopefully attain Higher speed
This happens because power doesn't change with gearing (apart from losses of course) only torque gets multiplied and thus force does to.
Upping the rpm the power is made doesn't get you anywhere as the benefit from higher rpm is lost due to having less flywheel torque to multiply, so you end up being back where you started
That is at the flywheel, with a constrained acceleration rate.
I think I recall reading something about acceleration engine dynos a while back, where the power was close enough to same (maybe a touch less) but the engine accelerated quicker through the RPM range.
This was on an engine dyno so no gearing involved. Would you take the quicker acceleration rate or take a touch more HP, so something taking 6.5 seconds to go from 7000-10000 or 7 seconds 7000-10000 but 10HP more.
Theres two answers on here I like a lot . Same exact curve except one is 900 RPM higher.
here is one interpretation of the two hp curves based on the 1st post and the 5th post quoted above.
based your own assumptions/interpretation of the statement/question you can come up with different answers.
based on my interpretation the vehicle cant tell the difference once you gear the vehicle appropriately so its the same. The reason being what you gain by being able to run more gearing is cancelled out because there is less torque at the flywheel to multiply through the gearbox and diff.
the same hp peak tells you this because both curves are linear and proportional to each other. if the curves arent linear/or proportional (there are infinite possibilities for curves that are proportionate and curves that arent propertional so you need to define both cuvres) then anything goes as a single value at a single rpm is NOT enough information. the way to work out if two curves are proportionate is to normalize them and then they should overlay each other
the conjecture would be what the "same exact curve except one is 900 RPM higher" means?, not to mention its an oxy moron
The HP lines are obviously wrong because they're never straight lines.
It's a totally bullshit question which has an equally bullshit answer until you can give proper torque / HP curves AND at the same time explain how you're going to build both engines.
You fail to realise it is supposed to be a theoretical question and that doesn't matter how you arrive at said engine for the purpose of the discussion. Also whether you use a real curve or generated one the physics and maths is all the same. People should have realised by now it is supposed to be open ended kind of question, just have to state any assumption made when giving an answer
joe 90 wrote: ↑Mon Oct 23, 2017 5:02 am
I realise that the answer to the question depends on certain inputs which are deliberately missing. Therefore the answer is whatever you want it to be depending on the missing inputs. So it's all bullshit. 15 pages worth of it.
There are good facts in this thread from those that have been there and done it. Many times, the value of a question is in the discussion...provided experienced people join in.
Warp Speed wrote: ↑Sun Oct 22, 2017 9:16 pm
Typo. .11 seconds per shift.
Well that's a bit more like it!
Did the effect of a 0.11 gear shift take into account the addition of hp extracted due to the MOI of the entire engine clutch and flywheel giving up energy due to the reduction of rpm during the shift. If it did then the effect of a shift should be way way less then 0.11 seconds of 'dead' time. During shifts on my highly instrumented Cosworth Sierra showed I did not lift off from 100% throttle during upward shifts. There was a small spike in the acceleration curve during a short period immediately after the shift as the clutch re-engaged. Cannot use this car as an example for the main stream of this debate as my Cozzy made more torque and hp as well as having a far greater over-speed capability than my competitors.
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digger wrote: ↑Mon Oct 23, 2017 2:29 am...
the same hp peak tells you this because both curves are linear and proportional to each other. if the curves arent linear/or proportional (there are infinite possibilities for curves that are proportionate and curves that arent propertional so you need to define both cuvres) then anything goes as a single value at a single rpm is NOT enough information. the way to work out if two curves are proportionate is to normalize them and then they should overlay each other ...
Quite so! Proportionality could be achieved by plotting the power (Y axis) vs. RPM (X axis) of the 6200 RPM version, scaled to say 500 RPM per inch, then adding a second X axis scale that is (7200/6200) x 500 = 580.65 RPM/inch. This single curve would then represent both hypothetical engines.
This is one of the reasons I like ST, posing very simple and straight forward questions that require application of the fundamentals we should not lose sight of.
Of all the posts I've read on here, I think Frankshaft explained it best, but IMO he kind of undermined his explanation by using "footsteps" and extrapolating HP and TQ numbers at different RPMs of the 2 different combos to support a "more work is done" ? answer with the higher RPM engine. Sorry Frank...
More work was NOT done...
Dyno calibration, ME, DA,barometric pressure changes and alterations aside, 600HP is 600HP is 600HP regardless of the torque/RPM output.
The ONLY difference in the 2 engine combos is the RPM at which the power output is achieved
The answer is the higher RPM engine combo is the clear winner, the reason is simple and I haven't yet seen it mentioned.
If we're dealing with the same car (weight, frontal drag, etc.) with both engines and each combo is geared correctly and the proper converter is selected, the higher RPM engine will have have a higher stall speed converter and lower gearing which will place LESS LOAD on the engine. In other words, the car will appear LIGHTER to the engine due to the additional gear and convertor and will therefore accelerate the vehicle faster.
It's really not much different than lightening the car OR taking a given engine out of a heavier car and putting it into a lighter one.
THAT IS THE BENEFIT of making power at higher RPM. That's exactly why we put "bigger" cams, valves, heads and carbs in/on the engine, to shift the TORQUE curve UP IN RPM range (which granted, usually creates more HP) BUT ALSO, to take advantage of the additional RPM to create the potential to utilize more gear for more torque multiplication. I believe most people lose sight of this when they think of high stall converters and shorter gearing as a "necessary evil" because it'd be a huge PITA (or impossible) to drive on the street without those items.
That said, it's worth mentioning how befuddling it is to me to see these "torque vs horsepower" debates as if they're mutually exclusive. Underlying suggestions that "torque" only occurs between idle and 4000RPM and "horsepower" starts at 5000RPM and up. Since we know the 2 are totally dependent of each other, the answer is BOTH.
In absolute terms, if I want to be the "fastest", I want the biggest engine to produce the most torque at the highest RPM (/5252 = HP defined), with the HIGHEST numerical gear and Convertor to put the engine in its highest power range, in the lightest car with the best traction.
. Same exact curve except one is 900 RPM higher.
