Horsepower Stampede ... (where do they Go ?)

[oztrackdays]

Watched a 2002 NB8B on the Dyno today stock as a rock it was.

sounded good and revved cleanly made 67 rwkw

If we take RedBook as gospel.

Power 107kW @ 7000rpm
Torque 168Nm @ 5000rpm
Acceleration 0-100Km/h (secs) 8.4
Cam DOHC with VVT

So If my maths is correct this car is making < 63% of the claimed power, so a 37% drive-train loss ...

Is it more likely to be a softer engine, Mazda using creative accounting in the brochure from day one or a little of each ?

From this Thread another car has 75 rwkw with some basic mods so it seems believable.
http://mx5cartalk.com/forum/viewtopic.php?f=29&t=60983

Can anyone else provide stock as a rock dyno charts for MX5's

[mr bender]

all dynos are difference.

my car has been on two difference Dyno (dynamics Dynos) and there was a 50 hp difference.

a dyno is a tuning tool only, so dont get to caught up in the numbers.

[hks_kansei]

Yep, the Mazda figure depends on what they tested on the day.

Factor in Dyno differences, wear and tear, temperature, modifications, tyre size, tyre pressure, tyre wear, strap tension, hunidity, etc, etc and there's the difference.


Also, I thought the NB8B was rated at 112kw by Mazda? and the NB8A was 107?

Mine dyno'd at 79rwkw at one Dyno, and 85rwkw at another.

[Okibi]

http://www.miataturbo.net/engine-performance-56/parasitic-drivetrain-loss-37110/

Ballpark figures seems about 25 hp.

[Okibi]

Given we can't compare figures accurately between dynos

I've only dyno'd my car once, the 98 NB made 82kw (with intake/catback)

67 rwkw still seems a little low.

Would be good to see the dyno sheet with air/fuel ratios and know it was dyno'd in 5th.

[project.r.racing]

To answer the original question about where the power goes.

The claimed power figures from any manufacturer are on a engine outside of the car running with drivetrain and asseccories attached.

Now add accessories and heavy drivetrain, wheels, rotors, spinning mass etc and what power comes from they tyres to road is lower.

[Dweezle]

Completely stock Malibu Gold NA6 on Mania Dyno made 71rwkw.


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[speed freak]

NB8B has 113 kw and 181 Nm at the flywheel stock

[Lokiel]

To answer the original question about where the power goes.

The claimed power figures from any manufacturer are on a engine outside of the car running with drivetrain and asseccories attached.

Now add accessories and heavy drivetrain, wheels, rotors, spinning mass etc and what power comes from they tyres to road is lower.

Aren't manufacturer figures quoted at the flywheel under optimal conditions? (always a bigger number)

Discount around 12% for drivetrain loss and that's pretty close to what you could optimally expect for rwkw for low-power engines.

[ralt]

Hi.
They say a standard na6 produces 60rwkw which is about right as flywheel kw is 85.5 minus 30% for drivetrain, accesories loss equals 59.5 rwkw.

[rascal]

The last few Dyno days that the Vic MX5 club did seemed to show consistently anout a 30% loss.

Ie na6s showed roughly high 50s
Na8s were high 60s
Nb8a were low 70s
Nb8b were mid 70s


So 30% seems a lot more than the 25hp or 12-15% that most suggest, so I would say that Mazda's factory figures are optimistic.

[oztrackdays]

Ok so nothing particularly wrong with that car just a very modest
Power offering from Mazda.

I have heard the NC struggles to
Make over 90 stock so seems consistently stingy.

[manga_blue]

There are some motors which are just plain soft from the factory. My NA8 dynoed at under 50rwkw the first time we did it. While some of the loss was from tired injectors, most was from really bad inlet to head and head to exhaust port alignments - amounting to over 30% of the port areas. This is something which was there from the start. It's not the only NA8 head that I've seen like that either although I have heard that machining quality in NB heads was much more consistent.

[sailaholic]

So 30% seems a lot more than the 25hp or 12-15% that most suggest, so I would say that Mazda's factory figures are optimistic.

I've always heard 30% across multiple manufactures.

Remember the are losses associated with accessories and drive train.

Differences sure to air pressure and temperate

Losses in the dyno type, and then correction errors in the dyno.

So while since drive train losses might be 15%, dyno "losses" might make up the other 30%

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[Snowmotion]

I think 30% is an accurate number for power train loss. My last car was rated at 206kw at the flywheel and produced 142kw on a 4WD dyno across an number of cars. (31% loss)