Technical Horsepower, what happens if...?

Unless the gearing is changed the speed at 7500 remains the same.

A bigger engine with longer stroke might also make peak HP at a lower RPM and actually go slower and not pull to 7500 also so you have to consider what RPM you get peak HP at for a engine change.

My race bike has a rev limiter I cant change . Even though I added 30% more HP my top speed is the same with rhe same gearing.
I just get there quicker.

 

Are we ***uming terminal velocity is being limited by the maximum attainable engine rpm or limited by drag?

If 7500 is the rpm ceiling, no amount of extra power will increase the car's top speed. It will just allow it to accelerate at a greater rate until we hit the limit of 7500rpm.

Different altogether if it is drag that is the limiting factor. Adding power would acheive a higher speed before the power and drag balanced out, yeilding a higher terminal velocity.

@theHIGHLANDER needs to streamline his question to get the corrct answer.... (pun intended).

 

Exactly! RPM was defined as PEAK.
If taken as limited top engine RPM, the answer is what I said.
If it is Peak HP, the answer is ???.

Also, I don't mess with BBCs, but my limited understanding is that all OHV V8s tend to have a higher HP at higher RPM over and above 7500 RPM when they can safely rev that high and are tuned for big numbers like 900 HP out of less than 500 Cu. In.
The original question was suggesting a 509 Cu. In.
More 'stock' style engines will not even rev to 7500. They will all have a drop at some point, but big numbers will peak later.
I went looking for "900 HP Big Block Chevy".
Note the size of these! Both seem to be making the 900 number at or below 7500, so that may fit the PEAK info, but it seems they are very big in size and the BBC is RPM limited.

https://www.chevy********.com/tech-stories/prestige-motorsports-900-horsepower-632ci-big-block/
https://www.shafiroff.com/chevy-drag-race-engine-sportsman/555-big-block-drag-race.php


So it goes back to the more HP but same RPM which is same speed, all other things being the same.

 

If the drive line is spinning the same RPM then speed is the same disent matter what the HP is.

More HP can pull a higher gear and make the car faster. IF it pulls the same 7500 RPM.

I ***ume a properly geared land speed car is pulling maximum RPM the engine can obtain as it crosses the finish line .

Id ***ume guys gear a bit higher than perfect so engine improvements can allow the car to go faster . ???..

 

I’ve got one for you that happened in 1963 at El Mirage. A compe***or I knew ran his near new 1963 Impala SS 327 300 hp at the May meet. It had 308 gears and went 111 mph. He came back in June with 4.11 gears and no other changes. Atmospheric conditions were very similar. He went 111. I believe aero has everything to do with it.

 

Well this didn't disappoint. Someone got it, "...everything else remains the same...". Thanks @twenty8 .

Lots of discussion as to whether a 509 (a displacement I just pulled outta my ***) can make 900 HP. AND sustain 7500 RPM as well. Really? My 477 went thru the traps at 7400 (7600 in really good air) but that's drag racing. FWIW I had GM dimple rods and a GM non-twisted forged crank. Did it over 450 times too. Parts be damned for this theoretical discussion.

Where was I coming from? While we don't perceive it cleanly an engine makes power "cycles" which I have no answer or value to add to that. It's not a steady hum like an electric motor, but even those cycle albeit much faster. I can handle being wrong and perhaps I am. Getting there quicker is a given, at least I thought so. The speed numbers came outta the same *** I picked the CID numbers from, seemed realistic given the idea. And for the record it can be a stock bodied car, streamliner, roadster, dragster, whatever. Maybe those power cycles don't add what I thought.

Working alone with no radio or media playing does this **** to me sometimes. I go down a rabbit hole of thought, tangible or otherwise

 

If you want to explore top speed vs hp in the way that you're interested in, don't do it at Bonneville.

 

"Salt Conditions" include dryness and/or roughness of the course, temperature, wind direction, air density, and visibility. All effect your maximum speed.

That's why some of us kept track of what we could and squeezed into 7 Street Roadster records with 2 engines with minimal changes at El Mirage and Bonneville.

 

Maybe I said Bonneville to stake the idea it was all top speed related. I actually wanted to explore speed vs HP or HP as it relates to speed.

Lets eat some frosting off the knife. If the final speed was attained over 'X' time in the 1st example, and if that time was reduced because of an added measure of work, is that extra work simply consumed in the process?

 

The "extra work" (or extra available horsepower) is not "consumed" by the increase in acceleration. While the engine is running it is continuously making the extra power available. The extra power will increase acceleration up until terminal velocity is reached, and the speed reached at terminal velocity will be higher due to the engine's extra ability to 'push' against the combined factors contributing to drag (which, as you stated, have remained constant).

This is ***uming that there are no other mechanical (engine related) limitations in play.

 

Well, seems we both stepped in the same mud.

To me the result of the work is the speed, and if what you say is true (true enough?), could it measure as a modest increase in speed? Nothing huge, but maybe as I think it thru 5 MPH would be. Maybe as this rabbit hole caves in the real question is how it makes it possible. If it does...

 

All that will change is the acceleration rate.
Now if you can introduce a variable besides HP and run a higher RPM, taller tire or numerically lower gear the speed will increase.