91camarosRS

iTrader: (5)

this is an equation i have came up with. Its kinda for fun a way to see how efficient the car is. It goes like this lets say you make 650 crank? Hp and you run a 11.5 you take 650 divide it by 11.5 you get 56.52 but that same power in a car running 9 flat you get 72.22 soi higher number the better. What do you think? Not super accurate but fun? Wish weight could be put into it somehow

DIGGLER

iTrader: (1)

77.17
heh... this is flawed. punch in a 1,000hp car running 9 flat. it SHOULD be LESS efficient than the 650hp car running 9 flat.

AlkyIROC

9 flat would be close to 1000 HP. At least that's what I'm pushing for. Efficiency would also favor a vehicle with a low percentage of converter slip.

I have no idea what my crankshaft HP is. I don't even know what my rear wheel HP is. I do have an estimated actual and simulated dyno correction based on current weather conditions HP based on the vehicle race weight and 1/4 mile MPH. I also know torque converter is very efficient at less than 3% which is very good.

Too many other factors can change how efficient the car can be. A poorly aerodynamic car will be less efficient at high speeds because it has a harder time pushing through the air. That means it will need more HP to run the same speeds as a more aerodynamic car while at slower speeds, it would be more equal.

There's also a power to weight ratio. Take an engine that pushes a third gen to 12.0 in the 1/4 mile. Drop it into a basic dragster and the dragster would probably run low 10's if not a high 9. Same HP, different amount of weight it needs to move. To get the third gen to run the same speeds needs a lot more HP. Which then would be more efficient? Keeping the race weight the same and no 2 cars are exactly the same weight, the faster you go, the HP required to go faster goes up exponentially.

A 15 second car with a 150 shot of NOS could run low 13's. A 9.5 second car with 150 shot of NOS probably won't get into the 8 second range. Was the slower car more efficient?

sethteef

The increase of horsepower and speed is graphed its not going to be a slope of 1 or be at a 45 degree angle. As it was pointed out that same boost in hp between the 15s and 9s car were not the same. As the cars speed up they get "heavier" because of the g forces acting on the car, kinda like how when you go up on the elevator you feel heavier. They take more power to increase at the same rate they did at lower speeds. So this should be taken into consideration as well as the weight and aero qualities of the car. I am not expert on this by any means but I do believe I am correct. Anyways I would have to say its really complicated to figure out the effeincy just from the whole physics apect. Now if all of the cars you were comparing all had the same parts and weight (minus the engine) it should be pretty easy to come up with a formula as long as they all fall in those parameters.

Zepher

iTrader: (1)

Divide the number by the weight of the car and see what comes up.

Weight
______
HP/Time

91camarosRS

iTrader: (5)

well yes i agree with both of you. The title of this is not really the best title. There ARE many things to consider but i thought it would be kinda fun. I came with it when thinking about f bodys with like 400 horse that run low12 just trying to think of a way to express how good the setup is. This is not true way of figuring out effecincy

91camarosRS

iTrader: (5)

well yes i agree with both of you. The title of this is not really the best title. There ARE many things to consider but i thought it would be kinda fun. I came with it when thinking about f bodys with like 400 horse that run low12 just trying to think of a way to express how good the setup is. This is not true way of figuring out effecincy

AlkyIROC

Efficient isn't really the best way to describe it then or maybe it is but the description isn't.

Many years ago when I ran a 383, I managed 12.0 passes but at 118 mph. A car that normally runs 12.0 would be around 108-112 MPH. I was still using 3.27 gears and 26" tall tires. The car was slow on the launch but would really start to pull as it got into it's powerband just before the 1000' mark. This wasn't efficient as the car needed a lot more gear to use all the available rpm before running out of track. Shifting at 6800, the car was crossing the finish line closer to the 5000 range.

Fast forward to my car today. I launch at 4500 rpm which is near the peak of the torque to get the car off the line quicker. The 6000 stall converter quickly allows the rpm to jump into the powerband. I shift at 7400, the rpms drop to 6400 and I cross the finish at 7400. The setup is almost perfect. By the time I cross the finish line, the engine/driveline has peaked out and can't give any more performance. I said almost perfect as I could do some changes to be at 7400 rpm a few hundred feet before the finish line. This could make me run slightly quicker plus more consistent.

By those standards, my car is very efficient as it's set up perfectly to use all the available rpm that the engine can supply to get to the 1/4 mile mark with no extra power left over. Having a 400 HP car but crossing the finish line while still in second gear means you have a bad gearing problem. Efficient on the highway, bad at the dragstrip.

RED_DRAGON_85

first, your equation is upside down.
what you should do is have:
(Time/Power)*100,000
Weight

this way, a fast time and low power in a light car gives a high number.
a slow time with a powerful heavy car gives a low number.
the highest number wins

edit:
for reference, a stock F-body gives 1.8

91camarosRS

iTrader: (5)

see this is what talking about. Its like those top speed calculators online never taken effect of drag. All for fun



and that might work

DIGGLER

iTrader: (1)

I am getting a .485 for my car with this formula. dont think this one works either.

RED_DRAGON_85

but the units check out!
jk.

really, i think weight is the problem. if weight is ignored, it becomes a lot better of a direct comparison...

Orr89RocZ

iTrader: (20)

Heres 3 comparisons on my car with 3 different motors

(Time/Power)*100,000
Weight


estimated 3425lb weight, 254whp, 12.95 at 103.8 on a 1.71 60 foot i think it was. 1.488

Estimated 3450, 400whp, 11.47 at 118.x on a 1.55 60 foot i believe. 0.831
With a 150 shot, 10.63 at 127 on a 1.45 60 foot. 0.592

3550 lb estimated now, 650whp, 9.86 at 141 on a 1.56 60 foot. 0.427

If higher number is more efficient, I can somewhat agree to that. 12.9's at 104 is very very good in my opinion. 9.86 at 141 is not at all. That 60 foot is no where near where it should be. 10.6 at 127 doesnt seem bad either tho, but the number isnt as high. I estimated 520whp for that run but it may have been closer to 500.

Using a 1.488 factor, with my 650whp I should have run 34 seconds....so this formula dont work either. 141 traps should give 1.3's 60 foots and 9.4's I would guess.

AlkyIROC

That formula assumes you know the exact HP and since time is involved, that would be a 1/4 mile time so the HP should be the actual rear wheel HP at the time of the run, not dyno HP.

My car has never been on a dyno and my calculated HP from a 1/4 mile run varies as the weather changes. Standard HP formulas can calculate the HP based on time and speed in relation to the race weight. I have dyno correction formulas to calculate what a corrected dyno HP would be when adjusted to the weather and track altitude. Since the ET will reflect the loss of HP due to weather conditions and track location, a dyno HP number will never be obtained at the track.

((9.348/750) x 100000)/3080 = 0.404 This is what the car actually does
((9.348/840) x 100000)/3080 = 0.361 Using dyno calculated HP. I'm down 90 HP just because I race at altitude.

Now if you want to use flywheel HP which is also what factory engines are rated at, the formula really gets thrown out the window because you'll never see that number at the wheels. If I want to guess at a flywheel HP, I may be close to 1000.

((9.348/1000) x 100000)/3080 = 0.303 Estimated flywheel HP

The higher the HP number, the lower the calculated number gets. The lowest HP number I will get is calculated from what the car will actually do on the track on any given day based on weather conditions and altitude.

91camarosRS

iTrader: (5)

maybe just maybe. With all this info we can come up with something. Lol


but on a side note i really need to learn or get explained to me exactly about 60 foot time and mph importance. I knowi know as a big car guy i should know but i always looked at et. and put my energy into auto x and road race so never learned. If someone lol would be willing to send a pm and explain it in depth that would be greatly apretiated

and sorry for my ignorance lol

Orr89RocZ

iTrader: (20)

What if the dyno is at the same altitude and same weather conditions? Wouldnt the number represent true hp? Assuming no corrections on the dyno, because cars will dyno more/less depending on air quality as well. Hotter the air gets the worse hp/trq gets.

But your right the formula gets skewed based on air conditions. I went 10.17 spinning first gear at 140.3 mph my last pass this year. With headwind and hot air temps, i needed alittle over 2 psi more boost to run similar MPH as my best in November cold air.

I would have assumed based on the air conditions that day, the car would have dyno'd the same hp at 16.5 psi or so as it did with 14psi. That same tune in november air would have gone 142+ mph easily and probably laid down another 25hp+

Orr89RocZ

iTrader: (20)

I've always looked at a car's efficiency based on 60 foot and ET per the MPH it produces. In my eyes a car that runs 11.0's at 116 is much more efficient than a car that runs 11.0's at 124. MPH is usually an indication of how much power you are making. If no other changes to the car, more power will usually net more mph trap speeds. ET is just the function of how well you use that power by how well you accelerate from the stopped position. This is where 60 foots come into play which is also depending on gearing/suspension/etc. Quicker 60's will really have impact on ET.

I can go lazy 1.70 60 foots in my car and run 10.0's all day long at 140 mph. If I got down to 1.60, i'd go 9.80's or so at 140 mph. MPH didnt change since power remains the same, but ET changed alot since i left the line harder/quicker.

RED_DRAGON_85

i agree.
the best car accelerates uniformly throughout the 1/4 mile.
in reality, the initial acceleration is much smaller, then the car hooks, and acceleration goes up. once aerodynamics come into play at around 50 mph, the acceleration tapers off somewhat.

then you have gear changes.
each gear change up decreases the acceleration.

generally speaking, if two cars have equal or similar power and weight, the one with the faster 60ft will win the 1/4.
now of course there are exceptions, but thats to be expected.

you guys are putting way too much thought into this lol... it was just a simple formula to compare two cars.... and a poorly thought out one at that.

AlkyIROC

Theoretically, no. Although dyno results from dyno to dyno are not always the same, a dyno result is adjusted to sea level conditions. They take into account the temperature, humidity and station pressure using the same formulas that I use in my laptop at the track. That way a car dynoed in Denver will give the same results as a car dynoed in Florida. If they had the same HP, the car in Florida will be faster just because of the lower elevation.

Not all dynos are the same. Some dynos give different results than others. You can have 3 different brands of dynos all beside each other and all 3 will give a different result. A dyno is only good for doing a tune. Do adjustments to achieve the highest results. What those highest results are don't really matter much once you're off the dyno.

Traction is ET, MPH is HP. When tuning at the track, watch the MPH to indicate if you're making more or less power. As mentioned above, you can spin off the line and still run the same MPH although the ET will be slower.

RED_DRAGON_85

i agree with Alky but with one minor point.
make sure you do each run at least 4 times before you make changes

car_fixer

this is an interesting topic, and can be many layers of efficiency, like individual parts (but does that matter, I drive the whole car down the track) or the sum of all of them. the reality is about 5 gallons of race gas to go about 2 miles and some giggle gas on top of that ....not an economy car at all. So I look at it this way, when the fun goes away its no longer worth gong to the track lol

Orr89RocZ

iTrader: (20)

Yeah when one motor gets boring its time to build a faster one... thats what I ended up doing...

car_fixer

Then it starts the game of getting said power to the track not to Mickey,Hoosier etc cuse you wasted the tires lol so, I guess that is related, tires spining is wasting lol