[sub_ETCS_ret]

Originally Posted by JoeAyalaM

It is the same thing, torque gives a direct HP at a fixed rpm.

Torque in LB FT x rpm / 5250 = HP

HP and LB FT are allways correlated, and cross at 5250 rpm. That means that let's say, from a mod you get 20% more torque at 3500 rpm, you will also get 20% more HP at 3500 rpm.

If you could run an engine at the same torque output all across the rpm range, HP would increase directly as per rpms.

That is the difference between a PD SC that puts out so much more torque (and HP) at lower rpms, and a Centri that can deliver higher final HP at higher rpms.

Please let me know if I did not make myself clear.

I get the formula and what you are describing but can the 2 charts be compared for which one has more power under the curve? If so, which one has more power under the curve? This would help me understand better.

Sent from my SM-G920V using Tapatalk

[JoeAyalaM]

Yes they can be compared, enter all data in excel and compare them on top of each other, usually a higher average output across the rpm range will produce a faster acceleration, but a higher top HP will produce a higher top speed. Power is needed for top speed, higher curve for faster acceleration.

So if you see a curve in the shape of the top one, faster acceleration, in the shape of the bottom one, higher top speed only if final HP is higher.

Of course it will all depend on transmission gear ratio and used rpm range.

[1LE801]

Originally Posted by sub_ETCS_ret

But you didn't learn how to spell in elementary school.

I can read the graph. Thanks for you useful input.

Sent from my SM-G920V using Tapatalk

Hahaha!! If you're gonna insult someone, spell check! Nicely done, OP!!

[JoeAyalaM]

I love this new laptop I have, BTW.

[toohighpsi]

Originally Posted by sub_ETCS_ret

I get the formula and what you are describing but can the 2 charts be compared for which one has more power under the curve? If so, which one has more power under the curve? This would help me understand better.

You actually found a couple pretty good dyno plots to compare, had a couple minutes and I'm OK with Excel so I made a couple plots that might be useful. First let's have a look at Torque.



When plotted on the same axis you can see the differences in these two boosting systems. The PD makes significantly more torque at the low RPM and then the two systems nearly match at high RPM which we would expect as the peak power of both cars were nearly the same. Now, torque by itself is nearly useless as it is a measure of force, not a measure of work - so in that case we need to reference Power which relates torque to a unit of time - in this case RPM - I have plotted the comparison below.



Now the differences become slightly less significant, but we have a useful comparison that can describe the difference in performance between two engines, since you drive in the areas under these curves, that area under the HP curve gives you the operating envelope, the more area, the more performance.



So what would make the higher curve faster? For an example, let's take a look at the 1/4 mile data from a Camaro, in this case the car ran a 10.81 and the HP Tuners data log is below.



From this data we can learn a lot. First of all you can clearly see that the Stall Speed of our A8 Torque converted at this power level is between 2900 and 3000 RPM. For that period of time the PD SC will be exerting about 285RWHP and the Centri SC will be delivering about 220RWHP (which do you think will 60' better?). Next we find that even though we have an 8 speed close ratio transmission we see drops from 6500 to about 4800 RPM during shifts. Even if we round it up to 5000 RPM the PD is going to have a 50RWHP advantage at 5000 RPM which tapers to equivalent RWHP at 6500 RPM. The power delivered to the rear wheels under the RPM curve will determine how fast we are accelerating. Hopefully by this point you can see why response (which we really didn't cover here) and power under the curve are important.

I quite often hear people say that they prefer the lower HP at lower speeds for traction, but that loss in lower speed power hurts you through the entire acceleration run.

Do you want a fast car? Always take as much power under the curve that you can get and either; learn how to drive it, use the torque management system to control it, or invest in a set of tires that can handle it.

[AndyUK]

^ assumes 1/4 mile and that ignoring cost factors are your primary aims, as well as what other simple low cost mods can improve that torque curve

Just sayin'

[sub_ETCS_ret]

Originally Posted by toohighpsi

You actually found a couple pretty good dyno plots to compare, had a couple minutes and I'm OK with Excel so I made a couple plots that might be useful. First let's have a look at Torque.

Attachment 839765

When plotted on the same axis you can see the differences in these two boosting systems. The PD makes significantly more torque at the low RPM and then the two systems nearly match at high RPM which we would expect as the peak power of both cars were nearly the same. Now, torque by itself is nearly useless as it is a measure of force, not a measure of work - so in that case we need to reference Power which relates torque to a unit of time - in this case RPM - I have plotted the comparison below.

Attachment 839766

Now the differences become slightly less significant, but we have a useful comparison that can describe the difference in performance between two engines, since you drive in the areas under these curves, that area under the HP curve gives you the operating envelope, the more area, the more performance.

Attachment 839767

So what would make the higher curve faster? For an example, let's take a look at the 1/4 mile data from a Camaro, in this case the car ran a 10.81 and the HP Tuners data log is below.

Attachment 839768

From this data we can learn a lot. First of all you can clearly see that the Stall Speed of our A8 Torque converted at this power level is between 2900 and 3000 RPM. For that period of time the PD SC will be exerting about 285RWHP and the Centri SC will be delivering about 220RWHP (which do you think will 60' better?). Next we find that even though we have an 8 speed close ratio transmission we see drops from 6500 to about 4800 RPM during shifts. Even if we round it up to 5000 RPM the PD is going to have a 50RWHP advantage at 5000 RPM which tapers to equivalent RWHP at 6500 RPM. The power delivered to the rear wheels under the RPM curve will determine how fast we are accelerating. Hopefully by this point you can see why response (which we really didn't cover here) and power under the curve are important.

I quite often hear people say that they prefer the lower HP at lower speeds for traction, but that loss in lower speed power hurts you through the entire acceleration run.

Do you want a fast car? Always take as much power under the curve that you can get and either; learn how to drive it, use the torque management system to control it, or invest in a set of tires that can handle it.

Thank you! That was the example I needed. Very clear and concise.

I think I was trying to make it harder than it really was.

Sent from my SM-G920V using Tapatalk

[LibertyHill]

The ADM LT4 dyno once again:

[parish8]

To me the power under the curve argument should be left to trucks that want to tow something. I can see why they care about power at 3000rpm.

For the rest of us that want to race we are only briefly under 5000rpm. Hell even that zl1 Nurburgring video is only seldom and briefly under 5000 rpm.

For the sensation of feeling fast it is nice to be able to roll into it at a low rpm and get a rush of power without a downshift and a bunch of noise so for this more power under the curve is fun but if your actually racing someone you are going to want to pin it and get those rpms up.

Hp is what does the work and moves the car.

[sub_ETCS_ret]

Originally Posted by parish8

To me the power under the curve argument should be left to trucks that want to tow something. I can see why they care about power at 3000rpm.

For the rest of us that want to race we are only briefly under 5000rpm. Hell even that zl1 Nurburgring video is only seldom and briefly under 5000 rpm.

For the sensation of feeling fast it is nice to be able to roll into it at a low rpm and get a rush of power without a downshift and a bunch of noise so for this more power under the curve is fun but if your actually racing someone you are going to want to pin it and get those rpms up.

Hp is what does the work and moves the car.

It's funny that you mention all of this. I read a ton of articles arguing which is better HP or TQ. I would say 7 out of 10 articles argued that HP was more important.

[parish8]

Originally Posted by sub_ETCS_ret

It's funny that you mention all of this. I read a ton of articles arguing which is better HP or TQ. I would say 7 out of 10 articles argued that HP was more important.

Tq is a static measurement. There is no way to predict how much work you are going to be able to perform if you only know tq. Add rpm to tq and now you have hp. With that you can now calculate how much work(how fast) you can do.

I have a number of examples.

2 trucks both the same weight. One has 2000tq/1000hp. The other has 1000tq/1000hp. Both are geared optimally. Who wins? It is a tie.

Now turn it around. One truck has 1000tq/2000hp. The other has 1000tq/1000hp. The truck with more hp will be much faster.

There is a reason all of the calculators ask hp and not tq.

Another example is a turbine. They only make a few ftlb of tq but something like 400hp and they push tanks. Tq doesn't matter. It can be manipulated with gearing. Hp can not.

You will be faster if you can push your tq to a higher rpm even if you do not increase your tq.

[LibertyHill]

Originally Posted by parish8

To me the power under the curve argument should be left to trucks that want to tow something. I can see why they care about power at 3000rpm.

For the rest of us that want to race we are only briefly under 5000rpm. Hell even that zl1 Nurburgring video is only seldom and briefly under 5000 rpm.

For the sensation of feeling fast it is nice to be able to roll into it at a low rpm and get a rush of power without a downshift and a bunch of noise so for this more power under the curve is fun but if your actually racing someone you are going to want to pin it and get those rpms up.

Hp is what does the work and moves the car.

Agreed. And even better with a higher stall converter if you are auto.

But my car will never see the quarter mile or a 10-speed auto. It will see the Three Sisters quite a bit along with similar roads near home and hopefully some local road courses. I'd rather not have to spin it up to 5K+ to have fun with it. I did that for years in a 69 Dart 340 and it got old quick. Trying to save others from making the same mistake.

[sub_ETCS_ret]

Originally Posted by parish8

Tq is a static measurement. There is no way to predict how much work you are going to be able to perform if you only know tq. Add rpm to tq and now you have hp. With that you can now calculate how much work(how fast) you can do.

I have a number of examples.

2 trucks both the same weight. One has 2000tq/1000hp. The other has 1000tq/1000hp. Both are geared optimally. Who wins? It is a tie.

Now turn it around. One truck has 1000tq/2000hp. The other has 1000tq/1000hp. The truck with more hp will be much faster.

There is a reason all of the calculators ask hp and not tq.

Another example is a turbine. They only make a few ftlb of tq but something like 400hp and they push tanks. Tq doesn't matter. It can be manipulated with gearing. Hp can not.

You will be faster if you can push your tq to a higher rpm even if you do not increase your tq.

Thanks! Great examples.

I'm pretty smart but sometimes you gotta break it down to me in the form of Dick, Jane, and Spot scenarios.

[sub_ETCS_ret]

Originally Posted by LibertyHill

The ADM LT4 dyno once again:

That's a lot of wheel burning tq upfront.

How are you liking the conversion so far?