Confused about dyno..

[AutobahnRacer]

im a little confussed here . i had my prelude on the dyno and it came back as 151whp. i read that for preludes the majority says for crank (for prelude at least) its 15% while smaller portion says 25%. If its 15% that comes out to be 173.65 hp. Specs say prelude should be around 198hp from factory. Even at 25% its shy of 198hp. What gives?

[foss]

Could be a dud from the factory + high mileage= less hp

[AutobahnRacer]

im thinking maybe the factory is BSing because alot of people have come across the same problem similar ranges as me. so maybe they are just BSing. wouldnt supprise me considering i called to verify that i have the high beam on the high and low on the low, and they told me there is only one bulb for both together but whats the correct percentage i should be using so i know

[SovXietday]

Ok... dyno is JUST a tuning tool. The numbers will vary depending on the type of dyno and the calibration of the dyno.

If you want to know what kind of power the car is making, take it to the track. Track times don't lie.

[dragonfly2k3]

If the car is rated at 198hp new then you are right on par. You have to take into account drivetrain loss, and mileage. Your motor is not going to perform now like it did at 8k miles.

[NJGOAT]

Listen to what Sov said. A dyno is just a tool and every dyno can read differently depending on how it is setup and who makes it. My guess would be that you were dynoed on a "Mustang" dyno. They tend to read lower than the more common "Dynojet". At the end of the day, your dyno sheet is just a piece of paper with some numbers on it. The true story is how the car performs....eg 1,000hp; 12 second Supra's.

[ozthunder]

Edit: sorry, off topic lol.

[NJGOAT]

Originally Posted by Carministrator

im thinking maybe the factory is BSing because alot of people have come across the same problem similar ranges as me. so maybe they are just BSing. wouldnt supprise me considering i called to verify that i have the high beam on the high and low on the low, and they told me there is only one bulb for both together but whats the correct percentage i should be using so i know

The factory BSing may actually be true. When the US switched the SAE rating system, many of the Japanese maunfacturers had to make some major changes to their quoted hp numbers. If I remember the new RSX-S went from 200 to 197 and the V6 Camry went from 225 to 200. This was a couple years ago but the Japanese were definitely "cheating" on the hp numbers side.

Generally accepted percentage corrections are 15% for FWD or RWD and 20% for AWD.

[ozthunder]

Not all cheat, as we see with the new GTR.

[NJGOAT]

Originally Posted by ozthunder

Not all cheat, as we see with the new GTR.

Oh for christ sake...that all took place a couple years ago as I said. It affected EVERY car manufacturer in the US, but the Japanese manufacturers had to make the biggest adjustments. If you haven't noticed, all quoted hp numbers used to be rounded off to the nearest 5 and they aren't anymore, that was also part of the change. They also weren't really cheating...hence the quotes...they were just exploiting loopholes by running the engines with minimum oil, minus accessories and in ideal conditions. The law was changed so that engine hp had to be measured based on real world application and no more rounding was allowed.

I wasn't trying to bust anyone's balls, just trying to point out that the op may not be too far off in assuming that the factory stated hp number for his car may be higher than what is true in real life conditions.

The GT-R has nothing to do with it as it was built after the rule change and under quoting hp (while perhaps new to the Japanese) isn't really a new thing in the automotive world.

[ozthunder]

I know, I was just prodding

Reference the RX-8 for a solid example, btw, of what you are talking about.

[Nick 95 6sp]

As already stated, besides the effects from dyno setup and loading which are important and can have significant effect on the results, you also shorted yourself a little bit:

if whp was 151, then 15% driveline losses would make it 151/0.85 = 177.6bhp; with 25% driveline loss you have 151/0.75 = 201bhp ...at 24% loss your crank power would be that 198hp rating you mentioned.