Jean

Jussi

I knew you spent a lot of time using the search button on Rennlist but I had underestimated the amount of posts you have read here and the info you took with you!

The version 7 from thesoftware is not a commercial version, it is still under testing apprently and should not be used.

I will give this a quick shot, I will take the example for your car.

Before starting, you need to keep in mind that in order to do HP and torque calculations, you need to smoothen the long G data to reduce parasitic information.

Th edevil is in the details! In your case, the 0.4G at 209 kph is clearly an aberration. Look at the trend in the long Gs before those spikes at around 209kph, you will see that you are trending at 0.36 at around 207 kph and dropping from there obviously.

I have attached two close up charts to make it clearer. In the first one you see how there are some spikes at the 209kph level,



and in the second one which is a close up, you clearly see that the data cannot be used from that datapoint in particular (good choice of datapoint though ) at 129mph, you would be in reality below 0.36Gs. At that point you are at around 5612 RPMs.



With the above in mind, let us calculate your HP and torque at that point excluding drag.

Long G: 0.36
Speed: 129 Mph
Stock 993TT gearbox: 5th gear
Total weight: 3260 lbs
Tires: 295 x 30 x18 => Tyre OD in (In)= 25.0

Kph /1000 RPM: 60000*(PI*25.0/10^6)/3.227028))= 37.0
=>RPM at 207.66kph (129mph): 207.66/37*1000= 5,612 RPMs


FWTQ= 0.36*3260*25.0/2/12/3.227028/0.17 = 462 lbs = 626.4NM of torque.
FWHP= 626.4 x 5612/5252= 484.4 FWHP =361.2 KW

So at this datapoint in particular, you had about 626 NM of torque and 484 FWHP, excluding drag. You can imagine that we are very far away from your calculated 867NM! If you had 867NM, I would be betting that you ran beyond 1.3 Bar of boost, that BMEP does not lie.

I hope we don’t have to debate the calculations, they are very straightforward

The other items (negative acceleration items) are not included here.

As to the other uses of these formulas such as max speed etc.., what you posted is just the beginning basic stuff , once you get to simulate quartermile times and speeds for every RPM point, acceleration within gears from xxmph to yyy mph, up to what speed you have wheel spin with different tires and gears, impact of gearing, traction and gear changes across a 0-320kph etc.. this is when all this becomes interesting, been doing this for a few years now with real life data to validate.

Jean

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Phelix is 100% right, It is HP not torque.

Stummel

thx, exactly what I should have had calculated before having the taller 6th gear installed :-)

What is the "typical" max hp of a 993 tt engine that is capable of delivering 550NM@6900rpm?

600+hp?

Jean

Stummel, with a 0.7 6th gear, you will get to around 330 kph, at stock redline.

TB993tt

Whoops I had better answer that one having just slated Jussi for stating the "blleeeding obvious"

550NM @6900rpm = 404.4lb/ft

to work out the hp at 6900rpm: 404.4*6900/5252 = 531hp - so that is probably the maximum hp for that tt motor. The torque will typically be higher since that is made further down the rev range.

Stummel

Jean, the problem would not be the redline but the power needed to get to redline :-(

(~550hp?)

Stummel

Toby, I know that formula.

My question was what maximum (peak) hp a typical 993tt engine would have to still have 530hp at redline because most air cooled tt engines drop power dramatically at higher rpms.

Jean

I realize that, with 550 BHP you will get there Stummel.

Edit: Sorry I misread your initial question

Jussi

look TB, I wasn't joking

TB993tt

Phew.... I thought you did

I see what you mean now......

I don't think there is really a "typical" 530hp and above 993tt engine is there ? I know the ~520-550 ones Schmirler has been doing lately with the big exhausts and cats seem to keep 90% of their power to 6900......

Stummel

It seems that it would be a simple task for you guys to create a Excel spreadsheet that gives the perfect gear ratio for top speed for a given torque curve or that calculates the needed hp for a given gear ratio...

In theory all you 3 guys had enough horses to go 330+ kph with the right gear ratio.

Jean

Stummel , a 520 BHP 993TT with stock bodywork and tires should get to 330kph with a 0.7 Gear. At that speed, the car will have an acceleration of 0.24-0.25G approximately, enough to offset drag and resistence etc.. Depends on the day!

Jean

My answer was meant for you Jussi

It is not torque,it is HP, of course they are related, but since torque is irrelevant of RPM , while what makes your car go faster is HP at high RPMs ( => torque).... An F1 car has a lot of HP or torque??

Jussi

See my suggestion for that 330 with 0.7 question

I used "real porsche style hp"

Jussi

Jean, really.. This is not good enough reason to debate