Hp and E.T. 'S

[273]

There's been tons of arguments about the true hp of certain combos especially magazine builds all the race guys always say the only true way to know is run it.

I agree that running it show what your car is capable of and probably best to prove it's perfomance but I don't believe it's any better way to accurately calculate your hp.
There so many variables between weather location and track conditions and drivers abilities that you can't accurately compare et's and where did these equation come from obviously we know nothing about how these engines were dyno or how these cars were run to find out the calculations.

I think we all get caught up in the details sometimes and throw the baby out with the bathwater.

 

[Johnny Mac]

I tend to live by the age old adage of "its a 16 second car until I see otherwise"

You are correct...tons of variables in quarter mile times vs engine hp. A 1000hp engine in a car with a mismatched converter and 323 gears runs 12's. Where a 500 hp engine in a properly setup car can click 9's.

I further agree with you that hp is just that days configuration, and that days weather, and that specific dyno. Not uncommon for a dyno to vary hp from machine to machine, just like weather can vary a cars et by large numbers.

Idk if I added anything to the post, as its a statement, not a question. But I agree that sometimes chasing numbers gets people caught up in things well outside the realm of necessity, and sometimes even reality.

 

[replicaracer43]

Well its simple pysics, really. Even the old mopar chassis/engine bibles have the info in them if you bother to read them. It requires a certain amount of horsepower to move a certain weight of car down the 1/4, at a particular MPH. The confusion that i notice, is guys get hung up on trying to compare ET to horsepower, and you cannot do that. HOWEVER, weight and MPH CAN be used to figure horsepower though. As for weather changes, yes, it will effect the MPH, because it will effect the HP your engine is producing at that time of your run.

 

[rmchrgr]

Not sure exactly what you are asking about here but I will answer to see if it might help to clear things up. Obviously a 1/4 mile run will be the most accurate for a given car on a given day and a given state of tune. However, the sliding rule horsepower calculators are pretty accurate as long as you input the right info.

The calculators use wheel horsepower instead of flywheel horsepower and don't assume a percentage for parasitic driveline loss. So if you have a known 500 hp motor, figure 15-20% for power loss to likely be around 400-425 hp AT THE WHEELS.

The other factor in regards to accuracy is weight. Gotta weigh the car 'race ready' i.e.; car weight with driver, how much gas in the tank, etc.

The original muscle car motors were usually what, anywhere between 235-425 horsepower? Based on realistic driveline loss number and weight, the old drag tests from back in the day were probably pretty accurate.

The weather and track conditions will factor in to make it more finite but if you input realistic numbers into a sliding calculator, they're generally in the ballpark.

Wallace Racing 1/4mi. stats calculator.