Tracking with Forced Induction

[AllDayJonRay]

Originally Posted by King Tut

I am 100% correct. Torque and RPM are the two things that determine the horsepower curve. Here is the formula:

(TQ * RPM) / 5250 = HP

Example of 300 ft-lbs @ 4000 RPM and 7000 RPM:

(300 * 4000) / 5250 = 229 hp
(300 * 7000) / 5250 = 400 hp

The slope for those points on a typical RPM/horsepower curve would be:

4000/229 = 17.5
7000/400 = 17.5

In order to have a "linear power" or horsepower curve, the torque has to remain a constant so that the slope of the line remains constant and linear as RPM increases. If the torque increases as RPM increases then the horsepower curve is no longer linear. I think you are confusing a power curve and a torque curve. The SCs do produce a more linear torque/boost curve, but NOT a power curve as I stated in my OP.

I understand the math, but you are still absolutely incorrect.

What you overlooked in providing me with the formula for calculating HP using TQ numbers is the fact that, because there is a constant algorithm, linear TQ curves produce linear HP curves. The relation between the two is that the shape of the TQ curve determines the same for the HP curve. So, if the TQ is linear, the HP curve is linear..

Here is an example. Notice that the TQ curve, while not flat, IS linear, and the HP curve follows suit. This is linear power, not to be confused with constant, or "flat" power, which a flat TQ curve creates.

[King Tut]

Originally Posted by King Tut

Why is it that the SC owners don't seem to understand what the word linear means? In order to have "power is linear" you have to have a flat torque curve. I have yet to see a single SC kit that has a flat torque curve. They always build boost/torque as RPM increases producing a non linear power curve. What you have is a more linear boost/torque curve. It isn't like a bigger engine because you still don't have any low end torque as your torque peak isn't till when close to max boost is hit in the upper RPM range.

Originally Posted by CSG Mike

The SC car has a linear torque curve that is not flat.

The Turbo car is only flat within the boost threshold. If you look at the *entire* powerband, it is not flat.

See my above quote yet again. The debate here is over the claim of a linear HORSEPOWER curve for a centri SC. This is a tracking thread. I guarantee when I am on track I will always be above the RPM threshold of making my full desired boost. It is just a small press of the throttle pedal away instead of knowing I have to be at 8000 RPM to make my full desired boost.

[King Tut]

Originally Posted by AllDayJonRay

I appreciate the math, but you are still absolutely incorrect.

What you overlooked in providing me with the formula for calculating HP using TQ numbers is the fact that, because there is a constant algorithm, linear TQ curves produce linear HP curves. The relation between the two is that the angle/trajectory of the TQ curve determines the same for the HP curve. But regardless, if the TQ is linear, the HP curve is linear..

Here is an example. Notice that the TQ curve, while not flat, IS linear, and the HP curve follows suit. This is linear power, not to be confused with constant, or "flat" power, which a flat TQ curve creates.

I will use your example values with the same math I just used:

135/4000= .034
315/7000 = .045

You can see that the slope is increasing as RPM increases meaning that the horsepower curve IS NOT LINEAR.

[CSG Mike]

Originally Posted by King Tut

See my above quote yet again. The debate here is over the claim of a linear HORSEPOWER curve for a centri SC. This is a tracking thread. I guarantee when I am on track I will always be above the RPM threshold of making my full desired boost. It is just a small press of the throttle pedal away instead of knowing I have to be at 8000 RPM to make my full desired boost.

HP = RPM x Torque / 5252.

RPM is a constant. 5252 is a constant. Torque is the variable. If torque is linear, then HP is linear. If torque is non-linear, than hp is non-linear.

This is a STI dyno. Is it linear?

[AllDayJonRay]

Originally Posted by King Tut

I will use your example values with the same math I just used:

135/4000= .034
315/7000 = .045

You can see that the slope is increasing as RPM increases meaning that the horsepower curve IS NOT LINEAR.

Both HP & TQ are increasing in a linear fashion... Therefore, linear power. It's really not a complicated concept.

You're manipulating the definition of the term linear to suit the type of power delivery that you wish it to describe.

[King Tut]

Originally Posted by CSG Mike

Not flat at all torque curve. Well, actually it's flat-ish if you look from 4000 to redline, but in a bad way; the torque keeps dropping from 4000 to redline.:

The AVO kit is probably the worst example as that kit more than any other struggles to maintain boost levels in the upper RPM range. I struggled with this myself on my GT2871R, but a larger GTX30 should be able to maintain the flat torque curve and boost level in the upper RPM range.

[AllDayJonRay]

NVM

[s2d4]

Originally Posted by CSG Mike

HP = RPM x Torque / 5252.

RPM is a constant. 5252 is a constant. Torque is the variable. If torque is linear, then HP is linear. If torque is non-linear, than hp is non-linear.

Are you sure? The math equations actually doesn't show what you are saying.

Torque is linear meaning it is a straight line. The only way you would get linear HP is if Torque is flat/constant?

[King Tut]

Originally Posted by CSG Mike

HP = RPM x Torque / 5252.

RPM is a constant. 5252 is a constant. Torque is the variable. If torque is linear, then HP is linear. If torque is non-linear, than hp is non-linear.

This is a STI dyno. Is it linear?

Let's focus here guys. Here is a random definition of a linear function:

A linear function is an algebraic equation in which each term is either a constant or the product of a constant and (the first power of) a single variable. The typical linear function in slope-intercept form is y = mx+b where m and b are constants.

The 5250 is in fact constant, the RPM is the single variable meaning that the torque has to be constant or flat in order to have a linear function.

y = mx + b

y = horsepower
x = RPM
m = slope that I calulated in my previous math example
b = y intercept which in this case you make 0 horsepower at 0 RPM so it is 0 and not used

If you have a non flat torque curve or a curve where torque increases as RPM increases than the slope or m increases creating a non linear function.

[King Tut]

Originally Posted by s2d4

Are you sure? The math equations actually doesn't show what you are saying.

Torque is linear meaning it is a straight line. The only way you would get linear HP is if Torque is flat/constant?

Torque has to be constant which also happens to be linear (slope of 0) to produce a linear horsepower curve.

[s2d4]

Originally Posted by King Tut

Let's focus here guys. Here is a random definition of a linear function:

A linear function is an algebraic equation in which each term is either a constant or the product of a constant and (the first power of) a single variable. The typical linear function in slope-intercept form is y = mx+b where m and b are constants.

The 5250 is in fact constant, the RPM is the single variable meaning that the torque has to be constant or flat in order to have a linear function.

y = mx + b

y = horsepower
x = RPM
m = slope that I calulated in my previous math example
b = y intercept which in this case you make 0 horsepower at 0 RPM so it is 0 and not used

If you have a non flat torque curve or a curve where torque increases as RPM increases than the slope or m increases creating a non linear function.

Lol, isn't this like year 5 maths? It is where I am from anyways.

[AllDayJonRay]

Originally Posted by s2d4

Are you sure? The math equations actually doesn't show what you are saying.

Torque is linear meaning it is a straight line. The only way you would get linear HP is if Torque is flat/constant?

He is correct. The math does provide exactly what we are trying to explain. You gotta be ok with the concept that a linear TQ curve can be linear at more angles than horizontal. A flat TQ curve creates a HP curve that is linear at a specific slope. A TQ curve that is linear at an upward angle (like those created by rotrex systems) also creates a linear HP curve, just with a steeper slope.

[s2d4]

Originally Posted by AllDayJonRay

He is correct. The math does provide exactly what we are trying to explain. You gotta be ok with the concept that a linear power curve can be linear at more angles than horizontal. A flat TQ curve creates a HP curve that is linear at a specific slope. A TQ curve that is linear at an upward angle (like those created by rotrex systems) also creates a linear HP curve, just with a steeper slope.

Hmm ok, I better throw away my Electrical Engineering Degree since V=IR.

[King Tut]

Originally Posted by AllDayJonRay

He is correct. The math does provide exactly what we are trying to explain. You gotta be ok with the concept that a linear power curve can be linear at more angles than horizontal. A flat TQ curve creates a HP curve that is linear at a specific slope. A TQ curve that is linear at an upward angle (like those created by rotrex systems) also creates a linear HP curve, just with a steeper slope.

I will correct the end of your statement. A Rotrex system produces a horespower curve with an increasing slope as RPM increases. It will have a steeper slope at higher RPM than in does at lower RPM. It is often hard to tell the linearity of a horsepower curve because the scaling is in thousands of RPM along the bottom on the X axis and only hundreds of horsepower on the Y axis. The flatness of the torque curve is often the easier indicator to look for.