As I said below I agree Tq @ rpm is what counts. And yes TQ at RPM is equal to HP. Pretty much the same info. PPrently I like to make use of the TQ@ rpm and you like to look strictly at HP.

Again...the reason why I do this is to keep things straight in my head over all. If I am setting up a nitrous setup on a stock bottom end LS1...I am looking for the braodest TQ curve I can get...I look to try to maximize the Tq in the upper rpms where is usually suffers on a nitrous setup. And all at the same time Im looking at the Tq as an indicator of the max I should push that motor since the Tq is a direct measure of cylinder pressure. For instance...I dont like to go above 600 rwtq or so on stock bottoms. So keeping that max target in mind...I will try to achieve that Tq # as soon as I can in the rpm range to as far out in the rpm range as possible....and alwasy keeping an eye out to not exceed that 600 tq.
Do that and you have made an effective combo that will spit out some good HP #

 

The 9,000 RPM car would accelerate faster because it could take advantage of a bigger gear.

 

Benji...you obviously have a point your trying to make Just share what your thinking..lol. I would love to hear it.

My answer to the above would be tha same as the previous example. I dont have enough info to make the call. I would need to see the full graph and not just the peaks if these are real motors.

 

Well...what if that 9000 rpm car was a 1.8 liter honda with a giant turbo that doesnt spool until 8500 rpm , made 800 hp at 9000 rpm and dies off at 9500 rpm? Or a peaky 347 with a badly made sheetmetal intake manifold doing the same thing.


And what if the 6000 rpm motor was a masterpiece and made 800 hp right at 6000 rpm but carried that HP (tq at rpm) out and it still made 750 hp all the way out to 8000 rpm?

There isno way to tell with these examples IMO just talking in terms of peak HP

 

I think you need to take into consideration TIME TO POWER, I say the 347 makes quicker ttp. As far as the 6000 vs 9000 rpm question, the 6000 will obviously make more torque, but the 9000 should mph higher!! In A short race I say TQ wins longer race MPH win's. assuming everything else is equal.

 

they would both have the same pressure... the theory about larger ci more cylinder pressure is wrong imho, for the same amount of nitrous it is acting in a larger volume thus less psi... smaller engine same nitrous higher pressure...

 

What you say is true except the "same amount of nitrous it is acting in a larger volume thus less psi". Seems to me the bigger cly volume would in fact inhale more n2o, not less. Small cube vs big cube and same jetted shot, wouldn't the bigger cly empty the bottle sooner because of volume use? If everything else is eqaul between the two, pressures should be the same if air/n2o ratios are the same, no?
Robert

 

This is a common mis-conception. Here is why I think so.

800HP @ 6,000 RPM = 700 FT. LBS.
800HP @ 9,000 RPM = 467 FT. LBS.

Let's say that for any give estimated MPH and tire size, the 6,000 RPM engine needs a 4.56 gear. Because the 9,000 RPM engine turns 50% more RPM, it needs 50% more gear, or, a 6.84 gear.

700 x 4.56 = 3,192 FT. LBS.
467 x 6.84 = 3,192 FT. LBS.

This is why, in my opinion, HP is HP is HP, no matter the RPM you make it at.

 

Oh it matters!!!!

 

Prove it.

 

Think of it in terms of the ideal gas law (even though this isn't what it is meant for) PV = nRT

Pressure * Volume = number of molecules * ideal gas constant * temperature

assuming that everything on the right side of the equation is the same, as volume increases, pressure has to decrease, and as pressure increases, volume decreases. If Pressure stayed the same, and volume increased, then the right side of the equation would have an increase.

basically, larger cylinders will require less pressure to make the same power.

Adam

 

OK, that makes sense to me. I understand now.

 

If the horsepower curve was perfectly linear for both motors, then your statement would be true. It really has to do with area under the curve.
If a 9000 rpm motor had exactly 1.5 times the area under the curve as the 6000 rpm motor and the gearing was perfectly matched as described earlier, then both motors would accelerate the 2 cars evenly.

 

I agree. As I said earlier, column average HP determines how quickly a car will accelerate. The ability for an engine to make and keep HP is all dependent on the heads, intake, carburetor, and camshaft. That's where a good engine builder comes into play.

 

As I said earlier, column average HP determines how quickly a car will accelerate. The ability for an engine to make and keep HP is all dependent on the heads, intake, carburetor, and camshaft. That's where a good engine builder comes into play.

 

I think everyone is basically saying the same thing...just in different ways.