That's when you change the gearing to take advantage of the power produced by the stronger engine. The lower power engine won't be able to hit the rpm afterwards. Thus, the higher power engine is the faster way to go.

But it is true that if I stick a blown alcohol motor in a go cart without changing the gearing, the little 5 hp Briggs & Stratton will have the same speed at the same RPM.

 

What kind of nonsense is this? Of course power has everything to do with top speed. As the car goes faster the aerodynamic load increases to where the horsepower limit is reached and balanced by the load. What speed that occurs has nothing to do with RPM, unless the RPM is limited before the peak power occurs.

Jerry

 

you can have all the horse power in the world and it is shaped like a brick it will not beable to reach top speed like that of a smooth wedge shape one with 1/2 the power. also if you ever watch some cars that drag race that have 500-700 hp that only reach speeds of of like 130 or so, if they had that power in a more aero dynamic car with taller gearing it could go nearly twice as fast. i was mearly over stating that power namely is not as important and gearing and aero dymanics. just look at the c5 corvette and the c5 z06, z06 had more power with only a slightly higher top speed, 5-10 mph.

 

^ you must mean shorter gearing...

 

There are two kinds of top speed. Aerodynamic induced and RPM induced. If your car doesn't have the wheaties to push the air out of the way at a 6,000 rpm redline in top gear, you're simply not going to hit that rpm. Therefore, your speed is limited by aerodynamic drag. If you add power and are able to hit the target RPM, you're going to have a higher top speed that will become RPM limited. In this scenario you run out of gear, not motor.

The non-SRT cars would probably be aerodynamically limited if the artificial limiter wasn't there.
There's not much RPM left after the speed limiter kicks in so it'd probably be rpm limited.

 

that is not true at all. this isn't the 60's when cars speedos and driven by gear off the trans. there has been countless times when i have passed those cop things that show your speed and it was dead on every time at 25 mph or 75 mph didn't make a difference said the same thing in the xfire. ill try and take a pic next time i do it to show your guys (just hope i don't crashing trying to lol).

 

here is an interesting article for ya:

http://www.caranddriver.com/article....&page_number=1

 

Thanks for the info. I know it was exaggerated, but that ain't the point.
I see the 150 mph number you have above, but it just seems too long.
I haven't yet gone that fast, but I'm sure I was at 145 a lot quicker than
that. Tell you what... I'll break out my stop watch and see if I can't find a
nice empty back country road with a long enough straight away, without
any infrastructure around, or cops, and see what I can do. Not sure when
I'll get around to it, but will try tomorrow evening.

Coyote

 

The above statement is true, however the car with 900 hp will get to redline quicker in top gear, everything else being the same.

 

True, but I think the original topic was top speed, not who gets there faster.

 

Then you change the gears to use the extra 200 hp. The bigger power combo will go faster because the other setup doesn't have the power to use the taller gear.