DDK - Die Deutschen Klassiker

Max911 wrote:

Max,

Although the numbers seem to suggest that the engine is behaving much like a standard 2.2 in terms of peak values the shape of the curve is confusing.

It would he helpful to know the scales of the vertical axes as on the plot there isn't any data which is quite irritating but typical of the 'Rolling road' industry- If you 'scale' the torque assuming the peak value of 18.48 kgm (133 lbsft) then at 4000rpm the engine should be making 103 HP not the 85 HP shown (for this argument assume 1 CV = 1 HP)

At peak power of 123.06 CV and 5228rpm the torque indicated is around 10 kgm - 72.3 lbsft so power should only be about 72 hp

If you use HP and ftlbs the number should be the same at 5252 rpm.

The curve you have for your car shows a drop in torque that looks to steep to support the horsepower being reported.

As horsepower can't be directly measured - only calculated from torque and speed- the two curves don't appear to correlate.

@fethuoe if I correctly undestand I fear that I made the mistake to let the operator print both graphics on the same page but with only one vertical scale.

Before printing he showed me on the monitor power and torque on separate graphs and I shot only power (follows)



In the meanwhile I had the possibility to drive a 2,2T with a fully rebuild engine that I found pullig less stronger than mine altough smooth and more silent (no inox SSI fully exhaust).
Moreover a 2,4 S with engine fully rebuild that due to traffic jam I wasn't able to rev up appropriately and up to 4000rpm I found not so vigorous but probably is the feature of the S that Porsche community reports as common.


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Max,

The power of a engine is always a calculated value as there is no way to directly measure horsepower.

The torque and speed values are the only directly measured values and depending on the type of rolling road even torque may be calculated from angular acceleration adding yet further uncertainty.

When you look at the torque curve of your engine it doesn't seem to correlate correctly to the horsepower figures.

The engine may perform quite well but I just don't think the data is correct and I will try to explain.

The peak torque is stated at 18.48kgm at 4176 rpm.

If you measure the height of this peak and then compare this to the torque at 5228 rpm the numbers don't work well.

If the vertical torque axis has been offset from zero it would explain the discrepancy but as presented the data is quite poor and misleading, hence the reason for my question.

I would expect that a 2.2T would have a peak torque of around 18kgm at 4200rpm and a power of 125PS at 5800 rpm'

The steep decline in torque after 4200rpm is not what I would expect to see and at 5000rpm I would the torque to still be around 17kgm and at 2000rpm around 16kgm.

At 5800rpm torque would fall to around 14kgm.

There could also be a discrepancy on the speed axis but this seems less likely but will depend on how it has been measured.

Your engine seems to produce around the torque that I would expect from a 2.2 but I don't understand why it produces a typical peak power at 5-600rpm lower than expected as the torque curve doesn't seem to support this number.

I do realise you are happy with the engine and I am not trying to detract from this fact but if you have lost 8-900 rpm you have also lost some top speed.