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Originally Posted by longassname
Joe,
The numbers we are talking about are at the wheels. The factory quoted number is for the engine at the crank. The factory measures their numbers with an engine dyno which bolts directly to the the crankshaft. Chasis dynometers measure output at the wheels. Output measured at the wheels is lower because of the drivetrain loss. An SVX with an auto box in good condition seems to have about 30% drivetrain loss. Imprezas with manual transmissions seem to have about 25% drivetrain loss. As the condition of an auto box deteriorates the % of drivetrain loss increases and measured output decreases. The results you are giving for the UK svx are actually quite high, higher than I have ever seen for a stock SVX. I suspect the readings from that particular dyno are a bit optimistic.
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Thanks Michael.
You are more or less confirming what I said above, and confirming that the gearbox fudge factor for the auto is 30% for a good auto, or maybe more for a worn auto.
That all sounds reasonable.
However, did you perhaps miss the point that I was making, that all the cars compared in the dyno run were given flywheel output figures? In this sense I am assuming the dyno people took the wheel hp, and extrapolated to give the flywheel hp figure. Probably because most owners like bragging rights with bigger numbers.
This being so, then Mal's car will only have produced 133 at the wheels, and then had the estimated 30% added to that to give the 173 quoted. If this is the case, then Mal is down 67 hp from the 240 he was expecting.
{a note in relation to this; I think Mal's car is UK spec. The factory quote something like 225 hp for UK spec cars. I think the state of tune of all engines is pretty similar, but the ECU for each market takes account of the available octane for the petrol in the region. In that respect, I think the only engines with a high expected output of 235 or so will be the JDM market, where they have 100 octane petrol available}
If, as you seem to suggest, Mal's car is doing 173 at the wheels, indicating 224.9 at the flywheel, then this is making exactly what I would expect for factory tune on the car, and Mal will be pleased.
Mal's car is a '96 Yellow SVX, and he keeps it immaculate. I would not be surprised if gearbox, engine, everything is in tip-top condition on that car.
I must ask him which hp was quoted.
Joe