Which Is Faster - 600hp@6200 or 600hp@7100

[stealth]

The examples of more RPM are due to CID constraints...

Different scenarios....

500 ci pro stock can potentially make MORE HP at higher RPM makes sense...more power pulses with rpm...but hp is KNOWN to be higher in this case.... only cid is locked in.

[BILL-C]

Circle tracks, both dirt and pavememt, impose gear and tire dia rules to slow down the cars and level the playing field for the slower guys. RPM wins , but takes more skill and resources.

[tt 383]

Its pretty simple really, and the answer is staring you in the face if you just look. An Engine that makes the same peak power at 7200 vs 6200. RPM=Revolutions per minute. That means the 7200 rpm engine rotates 1000 more times in the same time, in this case, 1 minute. This will allow a higher gear ratio. Say 4.30:1 vs 3.73:1. Say the 6200 rpm engine makes 540 ft/lbs at 4400, the 7200 engine makes 490 ft/lbs at 5400. Simple math says the lower tq engine, with higher gear ratio, is EFFECTIVELY making over 100 more ft/lbs. So, the higher rpm engine is doing more work in the same time, and will be faster.

Another way for you doubters to look at it. If I drew a white line on a road, and took 6200 equal steps, say 2 feet/step. I would end up 12,400 feet down the road. If I start from the same spot, and take 7200 equal steps, the same 2ft/step I would end up 14,400 feet down the same road. No real magic in that, I simply did more work. The higher rpm engine has 1000 more revolutions in the same amount of time, doing more work. It has more stress on it, and likely won't last as long, requiring more maintenance, but, it is doing more work in the same time.

How many truck pullers reading this? What's the universally excepted way to pull farther? Is it building big, low rpm tq? No, you spin the piss out of em, the higher the better. Why? Because then you can put more gear in it!! Which means, you get more tire speed, or tire revolutions in a given distance, which again is doing more work, and results in a farther pull. The lower tq that the higher rpm combo makes, is simply made up from gear multiplication.

Tq is for tow trucks. If you want to win races, higher rpm wins every time. Before the efi and rpm rule in prostock, the fastest teams, had basically the this exact scenario. 500 inch engines. The team that made them rev higher, won. It was that simple.

Look at all the cubic inch to weight rules heads up type racing classes, or classes that are factored by weight to cubic inch. What do those guys do? They build smaller engines, and turn them more rpm, and go faster. Its pretty simple really. And its all over racing. I wonder how much slower a formula 1 car would be if they built bigger, lower rpm engines, that made more tq? Why are diesel trucks that make 1000hp and 1700 ft/lbs of tq, but peak tq at 3800 and hp at 4800 run so slow for how much power they have?

One of my projects this winter, a heads up drag race deal. Taking stroke out of it. Why? Because I/we want or, I should say need it to go higher in rpm. Not just physically rev it higher, but make peak power at higher rpm, and reduce tq. If it looses 30 ft/lbs at the rpm it makes peak tq now, and goes another 400 rpm higher, the car will ABSOLUTELY be quicker and faster, without even gaining hp. But, that's obviously part of th plan too.

One more. Top speed runs. Like Texas mile, Bonneville etc. Bonneville is a better example because it gives more distance. If you had 2 cars, with the example engines. The 6200rpm engine will just say uses a 2.20 rear gear, has a 28 inch tall tire. The cars are identical, only diff being the power bands, or peak hp rpm. The 6200 rpm engine goes 234.85 mph, pretty good!!. The 7200 rpm engine goes 272.73 mph, even better. Has it sunk in yet?

Another way to look at it, as quoted from a friend of mine, tq is the lack of horsepower. lol. Kinda true.

This is what makes sense to me and actually when broken down shows that 900 rpm isn't a huge difference over a 10 sec 1/4 Mile pass. Engine A gets a max possible 1033 revs for the 1/4 Engine B gets in 1183... factoring in gear reduction for those engine revs the tire sees a marginal gain in total rotation over that 1/4. Also those numbers are max rpm from start to finish so not realistic assuming 2 gear changes but just to get an idea of what it all translate too for a nice even 10.00 pass. It also helps you to see how a 2 speed with proper converter has the potential to be faster If you can avg higher revs over the 1/4 run... I assume you could break it down to the distance those tire revolutions would equal, then take the avg 1/4 Mile speed and get an estimate of time to cover that tire rotation distance then you could subtract that from the 6200 rpm engine?

[tt 383]

Its pretty simple really, and the answer is staring you in the face if you just look. An Engine that makes the same peak power at 7200 vs 6200. RPM=Revolutions per minute. That means the 7200 rpm engine rotates 1000 more times in the same time, in this case, 1 minute. This will allow a higher gear ratio. Say 4.30:1 vs 3.73:1. Say the 6200 rpm engine makes 540 ft/lbs at 4400, the 7200 engine makes 490 ft/lbs at 5400. Simple math says the lower tq engine, with higher gear ratio, is EFFECTIVELY making over 100 more ft/lbs. So, the higher rpm engine is doing more work in the same time, and will be faster.

Another way for you doubters to look at it. If I drew a white line on a road, and took 6200 equal steps, say 2 feet/step. I would end up 12,400 feet down the road. If I start from the same spot, and take 7200 equal steps, the same 2ft/step I would end up 14,400 feet down the same road. No real magic in that, I simply did more work. The higher rpm engine has 1000 more revolutions in the same amount of time, doing more work. It has more stress on it, and likely won't last as long, requiring more maintenance, but, it is doing more work in the same time.

How many truck pullers reading this? What's the universally excepted way to pull farther? Is it building big, low rpm tq? No, you spin the piss out of em, the higher the better. Why? Because then you can put more gear in it!! Which means, you get more tire speed, or tire revolutions in a given distance, which again is doing more work, and results in a farther pull. The lower tq that the higher rpm combo makes, is simply made up from gear multiplication.

Tq is for tow trucks. If you want to win races, higher rpm wins every time. Before the efi and rpm rule in prostock, the fastest teams, had basically the this exact scenario. 500 inch engines. The team that made them rev higher, won. It was that simple.

Look at all the cubic inch to weight rules heads up type racing classes, or classes that are factored by weight to cubic inch. What do those guys do? They build smaller engines, and turn them more rpm, and go faster. Its pretty simple really. And its all over racing. I wonder how much slower a formula 1 car would be if they built bigger, lower rpm engines, that made more tq? Why are diesel trucks that make 1000hp and 1700 ft/lbs of tq, but peak tq at 3800 and hp at 4800 run so slow for how much power they have?

One of my projects this winter, a heads up drag race deal. Taking stroke out of it. Why? Because I/we want or, I should say need it to go higher in rpm. Not just physically rev it higher, but make peak power at higher rpm, and reduce tq. If it looses 30 ft/lbs at the rpm it makes peak tq now, and goes another 400 rpm higher, the car will ABSOLUTELY be quicker and faster, without even gaining hp. But, that's obviously part of th plan too.

One more. Top speed runs. Like Texas mile, Bonneville etc. Bonneville is a better example because it gives more distance. If you had 2 cars, with the example engines. The 6200rpm engine will just say uses a 2.20 rear gear, has a 28 inch tall tire. The cars are identical, only diff being the power bands, or peak hp rpm. The 6200 rpm engine goes 234.85 mph, pretty good!!. The 7200 rpm engine goes 272.73 mph, even better. Has it sunk in yet?

Another way to look at it, as quoted from a friend of mine, tq is the lack of horsepower. lol. Kinda true.

I know exactly what you’re saying but your first constraint is the HP (measurement of work) is locked in to being equal...
Physically impossible if the Hp is the same.....

Think of it as 2 guys able to bend and lift the same exact amount of weight but guy B can do it 10 more times in an hour..

[digger]

If you have two engines with same hp you need to compare the actual useable hp curves, it is obvious that a single hp number and the rpm this occurs at is not enough information.

[digger]

Think of it as 2 guys able to bend and lift the same exact amount of weight but guy B can do it 10 more times in an hour..

Yeah that's different power.

It takes a certain amount of energy/work to lift a weight due to change in gravitational potential energy. If I do more lifts in an hr I'm doing more work per hr and therefore outputting more power

[tt 383]

Digger I believe you are misapplying power as work...

[MadBill]

Its pretty simple really, and the answer is staring you in the face if you just look. An Engine that makes the same peak power at 7200 vs 6200. RPM=Revolutions per minute. That means the 7200 rpm engine rotates 1000 more times in the same time, in this case, 1 minute. This will allow a higher gear ratio. Say 4.30:1 vs 3.73:1. Say the 6200 rpm engine makes 540 ft/lbs at 4400, the 7200 engine makes 490 ft/lbs at 5400. Simple math says the lower tq engine, with higher gear ratio, is EFFECTIVELY making over 100 more ft/lbs. So, the higher rpm engine is doing more work in the same time, and will be faster...

There are some fallacies in this statement, leading to the wrong conclusion, mostly from the assumed torque and RPM numbers.

o Since both engines are 600 HP, we can calculate the resulting torque at peak power for each. For the 7200 RPM engine it will be 600 x (5252/7200) = 437.7 lb-ft. For the 6000 RPM one it will be 600 x (5252/6200) = 508.3 lb-ft.

o If the 6200 RPM engine needs a 3.73:1 gear to go through the lights at the optimum percentage of peak power (say 10% past peak) then the 7200 will need a (7200/6200) x 3.73 = 4.332:1 gear.

o The resulting axle torque at peak power for the 6200 RPM engine will then be 508.3 x 3.73 = 1896.0 lb-ft. For the 7200 engine it will be 437.7 x 4.332 = 1896.0 lb-ft.

How can the car tell the difference?

[digger]

Digger I believe you are misapplying power as work...

No each lift is work. the calculation of work is

Mass x gravity x lift distance (appropriate units)

Total work divided by time is power

So more lifts in an hr is more work per hr which is more power output (specifically average power over that time )

[Warp Speed]

How many of those equal power pulses are produced during the same amount of time between the two examples?

[David Vizard]

Its pretty simple really, and the answer is staring you in the face if you just look. An Engine that makes the same peak power at 7200 vs 6200. RPM=Revolutions per minute. That means the 7200 rpm engine rotates 1000 more times in the same time, in this case, 1 minute. This will allow a higher gear ratio. Say 4.30:1 vs 3.73:1. Say the 6200 rpm engine makes 540 ft/lbs at 4400, the 7200 engine makes 490 ft/lbs at 5400. Simple math says the lower tq engine, with higher gear ratio, is EFFECTIVELY making over 100 more ft/lbs. So, the higher rpm engine is doing more work in the same time, and will be faster...

There are some fallacies in this statement, leading to the wrong conclusion, mostly from the assumed torque and RPM numbers.

o Since both engines are 600 HP, we can calculate the resulting torque at peak power for each. For the 7200 RPM engine it will be 600 x (5252/7200) = 437.7 lb-ft. For the 6000 RPM one it will be 600 x (5252/6200) = 508.3 lb-ft.

o If the 6200 RPM engine needs a 3.73:1 gear to go through the lights at the optimum percentage of peak power (say 10% past peak) then the 7200 will need a (7200/6200) x 3.73 = 4.332:1 gear.

o The resulting axle torque at peak power for the 6200 RPM engine will then be 508.3 x 3.73 = 1896.0 lb-ft. For the 7200 engine it will be 437.7 x 4.332 = 1896.0 lb-ft.

How can the car tell the difference?

Bill,
Exactly right if the MOI is not factored in. That gets difficult as figuring out all the contributions from each relevant component takes a lot of time.

I noticed that Warps experience was contradictory to mine. Where a narrow power band is concerned we would have to look at how the power decays after peak power as this can have a significant effect.

All my motors have good to excellent staying power past the peak power point (good low lift flow!)so I am not exactly testing a poor revving engine vs a good one.

DV

BTW Warp I got to drive one of Jeff's cars at Charlotte set up as it was raced by Jeff three years previously. Got a whole new respect for the lads driving skills after that. It went from respectful to very respectful.

[digger]

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 )

[David Vizard]

Back to which is faster, unless you are severely limited by gearing options, as in DV's example, rpm wins EVERY TIME!
Before the gear rule, we would sometimes sacrifice power to be able to turn more rpm.

WARP
Where did I say my gearing options were limited??

DV

You didn't, I just assumed that was the case in an effort to justify your statement.

Feel free to take lack of gearing choice out of your thought process here. I had every gear ratio available to the mini race community for this.

DV

[David Vizard]

Warp said (a few pages back) Fast forward 3 years later, and we are at Pocono racing a 4.33 gear with a .91od turning 10,400rpm, and shifting twice each straight away. The old way to run Pocono was to down shift going onto turn one, and stay in that gear, only to shift to od on the front stretch. Even though it takes approximately 1.1 seconds for someone good to complete the shift sequence and return power to the wheels, the higher rpm multiple shifts killed the old style.

How many four on the floor championship winning drag racers take 1.1 seconds to go through a shift cycle????

DV

[Warp Speed]

Typo. .11 seconds per shift.