Nashua_Night_Hawk

Physics sucks for some but loved by others (ehmm, me included )

Here is the proposal.

Since the CLS has effectively 3 gear 1-2-3... Let us do this. Let us integrate the HP/Torque curve twice:

First, Dyno your Car:
1) Ia = Integral of HP/Tq from lowest dyno rpm to the redline
2) Ib = Integral of HP/Tq from 1-2 shift rpm to the redline
3) Add I= 1a+Ib
4) Divide I by (Redline rpm - lowest dyno rpm ) = Avg HP/TQ
5) Divide Avg HP/Tb Wet published stock weight = Avg HP/TQ per lb.

The above Avg HP/TQ per lb is your indicative acceleration index

JRock

:whocares:

2001CL

CLUofI

go home geek.

and by that calculation i am actually driving the batmobile

Nashua_Night_Hawk

Are the American People so naive... and ignorant... Do you think those who designed your lovely CL is so stupid ? :angry:

You are freaks...

allmotor_2000

How can you add the integral of the lowest dyno-rpm to redline with the integral of the 1-2 shiftpoint to redline? You then find the ratio of this 'area under the curve' to reduce the rpm factor there.... but you have already overcompensated here!

Your math doesn't work, my friend!

F=ma, try that! It you are trying to find an 'accelerative index', then try F=m(ka). a = dv/dt, m = mass of car, k = accelerative index and F = (some factor)*(torque).

You can't solve that... because you have too many variables!

Nashua_Night_Hawk

Well, the 2 integrals is to include only the Effective HP used during 0 MPH to the Redline HP at the top of the third.

It is the dynamic rpms used while going from 0MPH to 107-110 MPH.... got it? no overcompensation. Those intgral are directly % to the F in F=ma...

Does this make sense?

EricL

It would be nice to have a solid metric, but there is the issue of "optimization" -- some curves might be skewed relative to others.

Let me put this in other terms:

If you assume redline, you are assuming that the best power is available for that given engine by shifting at redline. It is quite possible that "some" of the people who end up with the S/C and/or other setups might have a "optimal" shift point that may or may not be at redline depending on the gear set (manual vs. auto).

At one point, I used the NHRA calculator and it basically said to shift out at redline...

The goal is to find max average acceleration (yes/no?) (maybe no). However, the minute you want to integrate and average, you need to make sure that it's "fair"...



The shift points are going to be impacted by the shape of the TQ curve and the gear ratios.

So, it is certainly possible to "extract" the "average value" from an integral, with well-selected start and end points:

Average_TQ_valueN = 1/ (end_point - start_point) * area_under_the_curve.[between start and end points]

area_under_the_curve == use whatever method you like

And

If you just assume a "set"/"fixed" shift point, you might consider the following:

Average_TQ_1: start_point1 = torque_converter_stall (for auto)
and end_point = red_line

(Note: the start_point would be more interesting for a manual in first)

Average_TQ_2: start_point2 = RPMs_going_into_2nd (with 1st at max rpm) and end_point = red_line

Average_TQ_3: start_point3 = RPMs_going_into_3rd (with 2nd at max rpm) and end_point = red_line

(Note: start_point2 <> start_point3)

You are going to have to multiply EACH Average_TQ_N by the respective gear ratio to get the "effective TQ" == acceleration in that gear.

OR

At least “weigh” the values or adjust the start points so you don’t “over emphasize” (or exclude) a particular low/mid rpm TQ area due to the assumption that the second and third gear start points are identical…


It may sound like "small potatoes"… However, the "areas" are not identical as defined by the varying start_points(1..3) as defined by the torque converter, gear shift points, etc…

If you want to automate this -- figure out how to just grab the Dynojet's "raw" data from various members and toss it in to Excel, etc...

Nashua_Night_Hawk

That what I meant EricL, I missed that I need 3 integral not just two since as you mentioned. (Gear ratio 2/ Gear ratio 1).. is not the same as the (gear ratio 3 / gear ratio 2 ) which is the shift point 2 and and shift point 3.

thanks for the clarification.

Nashua_Night_Hawk

The problem is that I do not have the raw data for my dyno... I guess it could the right time to digitize my dynp graphs and extract (TQ/Hp values at 250th rpms)

gavriil

So why do we need to get into gears when we are trying to find the area under a curve, etc.? Cant we take a chart like this one and figure out what the total area under that HP curve is?

Nashua_Night_Hawk

to account the fact that we have gears.

2001CL

just because you dont understand something and feel stupid, insulting people isn't the way to go. Yes i have no clue what he means but if he comes up with something useful i'm sure he'll explain.

EricL

IMO, it would be interesting.

Do you think you could get the data (if so inclined)?

JRock

We're just joking around a little because he's putting way too much thought into the performance of a non-sports car.

Nashua_Night_Hawk

Today,.. I am heading to Montreal, once back I will work on it

CLUofI

thank you.

and 2001: i did understand what he was saying. but i just do not see how it would be usefull.

Juker008

Lets just hope that Amir doesn't read this post of else we are all gonna have to go back to HS and hunt down our Physics teacher.


But I must give u props on a valuable Math/Physics lesson. Knowledge is worth more that all the hores, booze, and bolt-ons that anyone could by.....ok well maybe thats streaching it a bit.


Juker008

gavriil

OK fine. So can we forget about the gears and easily find the total area under the HP curve?

TRIFFSABRAT

TRIFFSABRAT

The combination of horsepower curve, torque curve, aerodynamic drag, rolling resistance, drivetrain losses, etc. make a complex picture, difficult to analyze and evaluate on paper alone. I think the simplest way to select shiftpoints for max acceleration is the following:

(1)On a level road, no wind, use an accelerometer to map acceleration vs. speed for EACH GEAR over its entire rpm range.

(2)Using graph paper, or Excel, plot the overlapping acceleration vs speed curves in each gear on a single plot of speed (horizontal axis) vs. acceleration (vertical axis).

(3)Shift points are determined by the SPEED at which the diminishing acceleration (at high rpm) in a lower gear just matches the increasing acceleration in the next higher gear. This procedure effectively maximizes the integrated acceleration over the speed range for the vehicle, all factors included.

Not all tranmissions are created equal, and few have gear ratios chosen for maximum acceleration across the entire speed range. Depending upon the gear ratios in your transmission, you may find that the crossing (ideal shift) point is beyond redline in some lower gear. Conversely, the optimum shift point between two gears may occur well below the redline in the lower gear. If you find, for example, that the acceleration crossing point between second and third gear requires shifting at about 8,000rpm, and the redline is only 7,000 rpm, you probably could benefit from a higher second gear ratio. On the other hand, if the crossing point occurs at, say, 5,000 rpm in the lower gear, you could probably have more acceleration in the lower gear if the ratio were numerically higher. In such a case, the crossing point into the next higher gear would occur at a higher rpm in that gear, probably beneficial. For maximum acceleration to top speed, the top gear should just permit the engine to reach maximum horsepower (not necessarily redline).

Nashua_Night_Hawk

I am planning on:
1) digitizing my Dyno (before and after at 250 rpms)
2) Doing a spreadsheet, implementing what Eric Descrbed
3) Sharing with you the spreadsheet so you can plug your dyno numbers