darock hat geschrieben:So, I read the article and still don't know more than the fact that the rolling road used in this article produced wrong numbers. Why are the measurements wrong?
Absolute figures are something you can tell the guys who only know that a higher HP number is better but have no clue that there is also something called torque
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They are wrong because you must know, axle ratio, tyre pressure, atmospheric pressure, intake temperature, axle POWER ON loss, axle power off loss (tyres deform under power and ride up the rollers) and much more.
Just a change of axle ratio will completely change the "nominal" power output of an engine at the wheels.
Why?
Because the maximum power will be say at 130km/h instead of 150km/h (where it is a lot higher).
The axle ratio on a TR4 is 3.7:1 with a live axle.
On a TR5 it is 3.45:1 with an axle with loads more bearings and UJs in.
Eg 2. my old race engine produced peak power at 7900rpm.
I had my own BOSCH rolling road and this indicated 7700rpm.
The reason for the difference?
The power train loss was HIGHER at 7900, so the rolling road, "misread" the difference.
The car was also running a very low axle ratio of 4.55:1, which also strongly and more easily affected the readings.
TBH, the best way to know the power output of the TR cars, is to bring a genuine blueprinted engine to the rolling road, then test every car and record the figures for each one.
I did this with my LPS, and I can assure it was correct.
I had AT LEAST 10, CP model TR5 and TR6 come in to this facility.
The lowest read 94-95kw, and this was the "normal cars"....this equates to about 126bhp at the wheels. With a power loss of 17bhp this meant 143Bhp DIN.
However, NO WAY were those cars producing "book" figures, so my LPS was overreading by about 10%, which meant those cars were making about 130bhp. That certainly all adds up.
Next was just ONE car that made 98kw, so let's be nice and say this one was managing 135bhp?
That one went really well.
Finally there was a blueprinted engine in a TR6 which gave me 105kw, really steady, & very good emissions.
Let's say that meant 158bhp - of course on my "high reading" LPS.
Well guess what, when you take off the 10%, that car was producing an absolutely GENUINE 143P DIN, which is what the book says it should.
Now let's forget the rest.
The car did a "track day" but everyone at the circuit swore that car was NO WAY standard, because it simply left all the other TRs behind on every lap.
That put a smile on my face and the customer, because it was me that built the engine.
STD, absolutely standard but properly built......