[jessrayo]

It is interesting to me that so many people have so many different opinions on "concepts" like area under the curve. Since no one has explained it like I have understood it I'll throw out my 2 cents.

If you look at the formula comparing hp and torque you can see that they are mathematically related and the only constant in the equation is 5250. Anytime you look at a dyno graph with torque and HP both plotted, the 2 lines will always cross at 5250rpm. It is a mathematical certainty. Because of this mathematical relationship the torque will always be more significant left of 5250 on the graph and the HP will be more significant to the right of 5250. Because of the mathematical formula, a certain number of torque will always have an exact correlation of HP depending on what the rpms are at. When people talk about "area under the graph" they are generally talking the area under the combined graph (torque left of 5250 and HP right of 5250) because this gives a general representation of how much grunt the engine is going to have at any given point on the rpm band. If the overall line is flat the engine has grunt everywhere. If there is a lot more graph to the right then the engine is going to have a lot more pull at higher rpm.

As others have pointed out, when racing, and at wide open throttle we seldom get the engine much below 5000rpm so if all you want to do is race, you don't need the torque at lower rpms. If you have a manual transmission and want to pick up a little speed quickly without downshifting, you need the torque on the left side of the graph. A car with more torque can climb hills, or mountains in high gear without a downshift. Auto trans usually will downshift based on throttle position even if you don't need to downshift.

If you are road racing a car with a dyno graph like Liberty hill posted you can come off the corners at 3000 rpm and the car will accelerate like a rocket because of the torque, on the first procharger graph you posted, if you come off the corner at 3000 rpm and hit it, you will get a slow progressive surge as it builds rpm until it gets into the power, you will just have to work the gearbox more to go as fast.

But after all of this, if you look at the tachometer while daily driving, you have to really hit it to get over 5000 rpm. For daily driving, the area on the left side of the graph is going to be much more useable because that is where your engine spends most of its time. Depends on how you use your car.

[sub_ETCS_ret]

Originally Posted by jessrayo

It is interesting to me that so many people have so many different opinions on "concepts" like area under the curve. Since no one has explained it like I have understood it I'll throw out my 2 cents.

If you look at the formula comparing hp and torque you can see that they are mathematically related and the only constant in the equation is 5250. Anytime you look at a dyno graph with torque and HP both plotted, the 2 lines will always cross at 5250rpm. It is a mathematical certainty. Because of this mathematical relationship the torque will always be more significant left of 5250 on the graph and the HP will be more significant to the right of 5250. Because of the mathematical formula, a certain number of torque will always have an exact correlation of HP depending on what the rpms are at. When people talk about "area under the graph" they are generally talking the area under the combined graph (torque left of 5250 and HP right of 5250) because this gives a general representation of how much grunt the engine is going to have at any given point on the rpm band. If the overall line is flat the engine has grunt everywhere. If there is a lot more graph to the right then the engine is going to have a lot more pull at higher rpm.

As others have pointed out, when racing, and at wide open throttle we seldom get the engine much below 5000rpm so if all you want to do is race, you don't need the torque at lower rpms. If you have a manual transmission and want to pick up a little speed quickly without downshifting, you need the torque on the left side of the graph. A car with more torque can climb hills, or mountains in high gear without a downshift. Auto trans usually will downshift based on throttle position even if you don't need to downshift.

If you are road racing a car with a dyno graph like Liberty hill posted you can come off the corners at 3000 rpm and the car will accelerate like a rocket because of the torque, on the first procharger graph you posted, if you come off the corner at 3000 rpm and hit it, you will get a slow progressive surge as it builds rpm until it gets into the power, you will just have to work the gearbox more to go as fast.

Thank you! I really appreciate input.

[sub_ETCS_ret]

I really appreciate everyone's input. I ask these questions because I can't seem to get enough info from a Google search. The information that you all provide is invaluable.

Thank you!

[sub_ETCS_ret]

Originally Posted by jessrayo

It is interesting to me that so many people have so many different opinions on "concepts" like area under the curve. Since no one has explained it like I have understood it I'll throw out my 2 cents.

If you look at the formula comparing hp and torque you can see that they are mathematically related and the only constant in the equation is 5250. Anytime you look at a dyno graph with torque and HP both plotted, the 2 lines will always cross at 5250rpm. It is a mathematical certainty. Because of this mathematical relationship the torque will always be more significant left of 5250 on the graph and the HP will be more significant to the right of 5250. Because of the mathematical formula, a certain number of torque will always have an exact correlation of HP depending on what the rpms are at. When people talk about "area under the graph" they are generally talking the area under the combined graph (torque left of 5250 and HP right of 5250) because this gives a general representation of how much grunt the engine is going to have at any given point on the rpm band. If the overall line is flat the engine has grunt everywhere. If there is a lot more graph to the right then the engine is going to have a lot more pull at higher rpm.

As others have pointed out, when racing, and at wide open throttle we seldom get the engine much below 5000rpm so if all you want to do is race, you don't need the torque at lower rpms. If you have a manual transmission and want to pick up a little speed quickly without downshifting, you need the torque on the left side of the graph. A car with more torque can climb hills, or mountains in high gear without a downshift. Auto trans usually will downshift based on throttle position even if you don't need to downshift.

If you are road racing a car with a dyno graph like Liberty hill posted you can come off the corners at 3000 rpm and the car will accelerate like a rocket because of the torque, on the first procharger graph you posted, if you come off the corner at 3000 rpm and hit it, you will get a slow progressive surge as it builds rpm until it gets into the power, you will just have to work the gearbox more to go as fast.

But after all of this, if you look at the tachometer while daily driving, you have to really hit it to get over 5000 rpm. For daily driving, the area on the left side of the graph is going to be much more useable because that is where your engine spends most of its time. Depends on how you use your car.

If I understand you correctly, if you have 550TQ and 550HP then that would be the ideal setup. 550TQ up to 5250 and the 550HP from 5250. Correct?

[Atomic Ed]

There is an old saying that I go by:

You drive the torque and you race the horsepower.

Seems to have held true for me over the years. I'm not much of a racer these days, so a PD was a great decision.

And it's a little bit of your background that influences you on your choice. Even though these cars a great with FI added, they still fall a little short of what level of performance I was getting out of my motorcycles. I'm use to the eyeball-flattening acceleration of a modern motorcycle. Even with my supercharged 2SS, my porky Gold Wing would give it a run for the money. (low 12's, high 11's with a good rider, that not being me). Two of my Kawasaki's were mid 9's.

So, yeah, a PD is the right choice for me as a daily driver. If I were to go back to the track with a somewhat serious intent, turbo all the way.

[sub_ETCS_ret]

Originally Posted by Atomic Ed

There is an old saying that I go by:

You drive the torque and you race the horsepower.

Seems to have held true for me over the years. I'm not much of a racer these days, so a PD was a great decision.

And it's a little bit of your background that influences you on your choice. Even though these cars a great with FI added, they still fall a little short of what level of performance I was getting out of my motorcycles. I'm use to the eyeball-flattening acceleration of a modern motorcycle. Even with my supercharged 2SS, my porky Gold Wing would give it a run for the money. (low 12's, high 11's with a good rider, that not being me). Two of my Kawasaki's were mid 9's.

So, yeah, a PD is the right choice for me as a daily driver. If I were to go back to the track with a somewhat serious intent, turbo all the way.

Interesting insight Ed. Thanks!

How's the weather on the East side of the state?

[jessrayo]

Originally Posted by sub_ETCS_ret

If I understand you correctly, if you have 550TQ and 550HP then that would be the ideal setup. 550TQ up to 5250 and the 550HP from 5250. Correct?

Correct, an overall dyno graph that is flat as a pancake will provide an engine that has consistent pull everywhere. It makes it much easier to drive fast because it won't have any surges across the rpm band. Honestly if you are over 500 hp/tq you are going to have to modulate power out of corners if you are trying to go as fast as possible. You can road race a car with a very peaky power band and go fast but it takes a lot more skill to keep it near the limits without making a mistake.

Actually 734 HP and 759 TQ is the ideal set-up.

[sub_ETCS_ret]

Originally Posted by jessrayo

Correct, an overall dyno graph that is flat as a pancake will provide an engine that has consistent pull everywhere. It makes it much easier to drive fast because it won't have any surges across the rpm band. Honestly if you are over 500 hp/tq you are going to have to modulate power out of corners if you are trying to go as fast as possible. You can road race a car with a very peaky power band and go fast but it takes a lot more skill to keep it near the limits without making a mistake.

Actually 734 HP and 759 TQ is the ideal set-up.

Haha. Those numbers look really familiar.

Sent from my SM-G920V using Tapatalk

[LibertyHill]

Originally Posted by sub_ETCS_ret

That's a lot of wheel burning tq upfront.

How are you liking the conversion so far?

So far my only experience with it besides drooling over the dyno has been a ride in Grammy's car. Mine is way overdue for completion, shooting for the end of the month now.

[DFW1LE]

Originally Posted by Atomic Ed

There is an old saying that I go by:

You drive the torque and you race the horsepower.

The old saying I remember is torque makes your car feel fast, but HP wins races.

[parish8]

Originally Posted by DFW1LE

The old saying I remember is torque makes your car feel fast, but HP wins races.

I won't argue with this. When I have had a non car person in a quiet latemodel turbo car I always loved rolling into it but holding a gear or two too high. Keeping it quiet and acting like I am just driving normal but having a huge rush of power.

[Blk16SS]

Originally Posted by sub_ETCS_ret

If I understand you correctly, if you have 550TQ and 550HP then that would be the ideal setup. 550TQ up to 5250 and the 550HP from 5250. Correct?

Hey Sub,
I will add abit to it from my perspective. Let's take our car for example. Say it makes 400hp/400tq to the wheels. Now say you're on the fence about that full exhaust system you've been winking at for a month. Only problem is that it hasn't winked back because it's $2500+ install. And all you keep hearing is it makes ONLY 15-30 hp.Yet all of the fastest cars have Long Tubes. And so you finally breakdown and get them thrown on. Now remember your established baseline is 400/400. Now you're strapped back on the dyno. Say you made your pull and the conditions from your baseline pull are 100% the same as they are today. Now after this pull your "peak" number is 420hp/430tq. Nice gains but let's take a closer look at where your money was really spent.... If you take both dyno graphs and do a lay over, you get a better understanding of what is going on. An example would be let's say it made 300hp @4000 rpms on this pull. Now let's say your baseline pull had you at 275hp at the same rpms. From that one example you can gather from this is, while you ultimately gained 20 "peak" hp, you gained as much as 25hp "under the curve" also referred to as "delta gains", in this case it's 4000 rpms. The gains could be higher but that's what you're looking for. Peak numbers say one thing, but how much hp and tq you gained over the entire pull with the peak is by far the most important thing to consider... hopefully I was helpful.....

[sub_ETCS_ret]

Originally Posted by Blk16SS

Hey Sub,
I will add abit to it from my perspective. Let's take our car for example. Say it makes 400hp/400tq to the wheels. Now say you're on the fence about that full exhaust system you've been winking at for a month. Only problem is that it hasn't winked back because it's $2500+ install. And all you keep hearing is it makes ONLY 15-30 hp.Yet all of the fastest cars have Long Tubes. And so you finally breakdown and get them thrown on. Now remember your established baseline is 400/400. Now you're strapped back on the dyno. Say you made your pull and the conditions from your baseline pull are 100% the same as they are today. Now after this pull your "peak" number is 420hp/430tq. Nice gains but let's take a closer look at where your money was really spent.... If you take both dyno graphs and do a lay over, you get a better understanding of what is going on. An example would be let's say it made 300hp @4000 rpms on this pull. Now let's say your baseline pull had you at 275hp at the same rpms. From that one example you can gather from this is, while you ultimately gained 20 "peak" hp, you gained as much as 25hp "under the curve" also referred to as "delta gains", in this case it's 4000 rpms. The gains could be higher but that's what you're looking for. Peak numbers say one thing, but how much hp and tq you gained over the entire pull with the peak is by far the most important thing to consider... hopefully I was helpful.....

Very helpful. Just another nugget to the knowledge bucket. Thanks!

Sent from my SM-G920V using Tapatalk

[toohighpsi]

Originally Posted by parish8

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.

That is correct, but even in the example that was requested, there was a 50 RWHP benefit at 5K RPM. At the first shift, the car with more "power under the curve" will no longer be catchable, in a drag race or on a road course.