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# All Gpl Mods Specs Spreadsheet

### #31

Posted Oct 11 2017 - 09:02 AM

### #32

Posted Oct 11 2017 - 10:35 AM

Lee200, on Oct 11 2017 - 08:36 AM, said:

I don't know if you ever saw this. It describes a method of testing the horsepower at the rear wheels for the '67 F1 cars. In each case, the difference between the engine and rear wheel horsepower is about a 20% loss.

What is the 3.6 constant in your equation for? I understand the basics where Power=Mass*Acceleration*Velocity and 9.81 is the KGs to Newtons factor and 745 is the Watts to Horsepower factor, but the 3.6 constant is a mystery.

Thanks Lee, that was a really interesting read!

ed76, on Oct 11 2017 - 07:55 AM, said:

ex Copper T79 , my test 284 HP , friend's test 274 HP ; GPL 260 HP

From reading the article Lee posted, I think that part of the problem here could be as highlighted in the article that it is m* and not m which matters. IIRC the original 67 cars do not model the body lift of the car and so m* = m for all speeds, whereas I am pretty sure that 66 mod does include body lift at high speed and so m* in this case will be less than m, the static mass of the car which will skew the equation in the opposite direction. Presumably this would also get messed up even worse though if you tried to do it for a 69 car with wings as then the drag and lift (well, downforce and so effective mass) become a stronger function of speed and so here m* is definitely not equal to m as was being assumed.

EDIT: Same deal for 65 mod too IIRC. I think that 65 mod and 67 original do not model lift and so m* = m is a good assumption. This might also be true for F2 as well, I can't remember. For other mods I am pretty sure that aero lift and/or body downforce are coming into play and so in those cases you cannot simply use m* = m in the equations. I would assume that 65 and 67 mods will give a fairly consistent loss factor comparing measured versus stated value from GPL, although the variation seen in this was presumably then used to "balance" performance between slots to make everything come out about right in terms of relative performance on track. For all of the other mods though I am pretty sure that m* does not equal m to a good approximation at all and especially when testing at Vmax, so this must skew your results.

Rob

**Edited by Border Reiver, Oct 11 2017 - 10:45 AM.**

### #33

Posted Oct 11 2017 - 12:29 PM

### #34

Posted Oct 11 2017 - 01:06 PM

### #35

Posted Oct 11 2017 - 01:11 PM

JonnyA, on Oct 11 2017 - 01:06 PM, said:

don't merge , make a new install

### #36

Posted Oct 11 2017 - 01:43 PM

### #37

Posted Oct 11 2017 - 01:51 PM

**Capture1 (1).JPG**

**60.95K**14 downloads

there is an other problem

I read gamma = 0,42 , but a friend tells me that the value is between 0.35 and 0.42, after him 0.37

*Parce que le creux "pire" n'est pas réaliste.*

*Donc je prends dans la continuité de la courbe qui suit . On serait donc plutot à 0.37G je pense*

Because the "worse" hollow is not realistic.

So I take in the continuity of the curve that follows. So we would be at 0.37G I think

**Edited by ed76, Oct 11 2017 - 02:19 PM.**

### #38

Posted Oct 11 2017 - 02:20 PM

### #39

Posted Oct 11 2017 - 02:24 PM

Total fuel: 42 UK Gal. (16 on each sides, 10 between the driver's spine and the engine)

Camber front: from -0,25° to -0,5°

>> rear: same

Castor front: 3° fixed.

>> rear: (none)

Toe in front: 1/8 in. in total

>> rear: 1/4 in. total

Ground clearance front: 3,27 in.

>> rear: 4,13 in.

Weight: 1102 lb (495,9 kg) dry

1562 lb (702,9 kg) laden.

---------Cosworth DFV------------

Compression ratio: 11:1

Maximum power: 408 BHP @ 9000 RPM (1967)

415 BHP @ 9500 RPM (1968)

430 BHP @10000 RPM (1969-1970)

Maximum torque: 245 lb-ft (332,17 Nm) @ 8500 RPM

Weight: 165 kg.

### #40

Posted Oct 11 2017 - 03:01 PM

(you have a MP)

### #41

Posted Oct 11 2017 - 04:38 PM

the cars had engines 1500cc S4 ford or Alfa 140 to 150HP at 7000rpm

I think the closest is 67F2BT

the laptime taken at Kyalami seems to correspond, + 4s compared to those of a BT11 2.7L

### #42

Posted Oct 11 2017 - 07:23 PM

Border Reiver, on Oct 11 2017 - 10:35 AM, said:

From reading the article Lee posted, I think that part of the problem here could be as highlighted in the article that it is m* and not m which matters. IIRC the original 67 cars do not model the body lift of the car and so m* = m for all speeds, whereas I am pretty sure that 66 mod does include body lift at high speed and so m* in this case will be less than m, the static mass of the car which will skew the equation in the opposite direction. Presumably this would also get messed up even worse though if you tried to do it for a 69 car with wings as then the drag and lift (well, downforce and so effective mass) become a stronger function of speed and so here m* is definitely not equal to m as was being assumed.

That seems wrong, mass should be invariant in these calculations (neglecting fuel burn). Are you confusing weight and mass here? Weight changes as it's a force, with lift acting the opposite way you get an effective weight at speed than standing still. Mass does not as its an intrinsic property of the object in question. The only way I see how weight comes into this is if you wanted to account for tyre grip.

### #43

Posted Oct 12 2017 - 05:23 AM

My point is that the analysis here is based on assumption of balanced forces when there is no net acceleration, which when the motive force is then removed will reveal how much motive force was previously being required to maintain that equilibrium state. However, I do not think that the free body diagram of all of the forces on the vehicle for this assumption is correct and I think that weight does matter as it will affect the rolling resistance since the car will be lighter at high speed which will change the friction of the car with the road as the vehicle slows down. This means that the form of the equation used to fit the deceleration curve isn't going to be the same for mods where there is body lift modelled versus mods that do not have this and so the meaning of k1 and k2 from the fitted equations will not be the same in those two cases, which will also then make the interpretation and comparison of extracted data between different mods more difficult.

Rob

### #44

Posted Oct 12 2017 - 05:55 AM

The other causes of errors are very numerous:

is it really Vmax?

To do this one must have perfectly done its setup, especially the gearbox and tire pressure

heating the tires and the engine

have a straight line sufficiently long (chroma key is a bit short)

is there any certain GPLRA graphics (or GPL setup manager data)

uncertainty about gamma reading ... etc

**Edited by ed76, Oct 12 2017 - 06:39 AM.**

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