say you had 2 cars, same weight, same body....one had 1000HP, but it redlined at 4500 RPM, and the other was a 200 HP engine that redlined at 8000 RPM. Same gearing on both cars, which would have a top speed?

I used to always think that the more power you have the faster it will go, but is it actually the more RPM you can turn? I was always wondering why a honda could go so fast yet it had so little HP.

 

I don't think HP has anything to do with it as long as you have enough road ahead of you.
Because every engine has a redline as to how much RPM it can turn. Now say both cars have 3:73 gears the car that redlines at 4500 RPM I would think would run out of RPM's before the 8000 RPM, thus making the car with the higher RPM be able to obtain a higher top speed, but I could be wrong.

------------------
'86 IROC
T-TOPS, TINTED WINDOWS, BRAKE LIGHT BLACKOUTS
GM GOODWRENCH 350
EDELBROCK TES HEADERS
FLOWMASTER
EDELBROCK 600CFM CARB.
KN AIRFILTER
ACCEL HEI DISTRIBUTOR
2:73 GEARS
Rebuilt 700R4, with manual valve body
Soon to be installed B&M Megashifter
and Exhaust Cut-Out

 

i know you need more power to turn RPM's with a lot of wind resistance

 

DTP,

The thousand-pony engine would propel the car much faster than the 200 HP engine.

If you understand the definition of horsepower, or work, it is torque at a given rate. In this case, it is defined as torque at a given engine RPM. A 200HP engine that peaks at 8,000 RPM would have a fairly high final drive ratio to be able to use the power at RPM effectively, while the 1,000 HP car would be best with a lower final drive ratio. A 4.88 rear axle with 200 HP applied at 1,500 RPM (about 120MPH) would propel an average car with an engine speed of 7,300 RPM. This would consume almost all of the power output of the engine. The 1,000 HP car would have a 1.90 rear axle turning at 2,800 RPM with five times the torque of the 200 HP car, but would also have more RPM and torque reserve to be able to propel the car to about 190 MPH (3,300 RPM axle speed).

It is much like the diesel trucks running over the road. The vehicle is traveling at 70 MPH but the engine is running at about 1,800 RPM. A Hyundai traveling at 70 MPH has the engine operating at about 4,000 RPM but still has a buttload less power than the diesel. On the other hand, a 1,000 HP 4,500 RPM red-line engine with 4.88 gearing isn't going to be very successful unless you are trying to pull down small buildings with the vehicle.

RPM is only a part of the equation, and by itself means very little. Horsepower, (or Kw output) is a more accurate measure since it quantifies the RPM by factoring for torque produced (or real work performed) at that RPM.

------------------
Later,
Vader
------------------
"Fear is how I fall, Confusing what is real..."
Adobe Acrobat Reader