Car show and dyno of 11/75 - 1976 - 280Z

[mgood]

This past Saturday I went to a local car show at a Pep Boys parts store, they were holding a grand opening for their speed shop and had a dyno available to rent, it was $45 to have your car dynoed.

I had my stock 37 year old engine done. I was after a diesel truck that pulled over 1900 in torque. There was lots of interest in my car after the truck.

My numbers were for 4th gear - 111.30 power and 127.85 torque. First run

For 3 gear - 118.27 power and 130.47 torque. Second run

My car is stock and is listed at 170 HP - 5600 rpm (SAE)

The guy driving said he took the engine up to 6k on the tack, the first run there was a puff of black smoke, he said that was probably carbon.

In the last picture you can see white smoke, not sure what that is, the car does not burn oil.

I don't know if this is bad or good for the age.

The car show was also judged with trophies and there was a foreign car category, so I entered.

I received second place out of about 25 foreign cars. I was not happy with the winner because it was a 6 week old Nissan 2013 - GTR.

Really tough to compete with a new car when you have a 37 year old car.

Any info on the dyno numbers would be appreciated.

[LeonV]

First off, you can't really compare numbers across different dynos. Also, I don't see whether the numbers were corrected to STP.

With that said, on the surface, the numbers look low. If they're not pressure or temperature corrected, that can at least partially explain why. It would've been helpful if there was an AFR trace-line. To really find out what's going on, go to an actual shop and have them dyno your car with an O2 sensor in the exhaust stream.

There are many factors that affect dyno readings. The less controlled the "experiment" the less accurate it will be.

[Wade Nelson]

The greatest benefit from an uncorrected dyno LIKE THIS is in doing before-and-after comparisons, to see if you changed the shape of the curve, moved the peak horsepower or torque, etc.

So for instance, if I were to get my hands on one of those big-bore throttle bodies, I might make a before-and-after run to see if it actually boosted horsepower, and by how much.

Why is correction needed? The engine is generally WARMER for the second run. It won't make as much power as when it is colder, and the charge is cooler. A lot of times a big electric fan will be placed in front of the radiator when making dyno runs to ATTEMPT to keep the coolant temperature more constant. Cooler fuel (first thing in the morning) will also create a cooler charge; a hot afternoon dyno session won't produce as much power...

Altitude correction (part of standard temperature and pressure) is obvious; an engine will make about 20% less power at 6000' than it will at sea level. So depending on the barometric pressure the day you test, you could get different results tomorrow, unless you correct for temp & pressure.

There are no labels on the x-axis of the chart so you don' tknow if your torque peak was at 3000 rpms or 4000 rpms, another "issue."

[LeonV]

The greatest benefit from an uncorrected dyno LIKE THIS is in doing before-and-after comparisons, to see if you changed the shape of the curve, moved the peak horsepower or torque, etc.

So for instance, if I were to get my hands on one of those big-bore throttle bodies, I might make a before-and-after run to see if it actually boosted horsepower, and by how much.

Why is correction needed? The engine is generally WARMER for the second run. It won't make as much power as when it is colder, and the charge is cooler. A lot of times a big electric fan will be placed in front of the radiator when making dyno runs to ATTEMPT to keep the coolant temperature more constant. Cooler fuel (first thing in the morning) will also create a cooler charge; a hot afternoon dyno session won't produce as much power...

That's not really what the correction factor is for. This is an example of one of those variables that can give screwy results. Coolant (and oil) temps should be stable and consistent in order to have any kind of valuable data.

Altitude correction (part of standard temperature and pressure) is obvious; an engine will make about 20% less power at 6000' than it will at sea level. So depending on the barometric pressure the day you test, you could get different results tomorrow, unless you correct for temp & pressure.

The reason for correction factors is to compensate for temperature and pressure (hence air density) differences at the time of the test. Ideally, this normalizes all tests as if they were all done under the same conditions. In reality, cross-dyno comparisons are invalid unless the dyno adheres to certain strict calibration and procedural standards (ASTM, SAE, etc.).

There are no labels on the x-axis of the chart so you don' tknow if your torque peak was at 3000 rpms or 4000 rpms, another "issue."

The graphs in general suck and don't make much sense (overlapping power and torque curves). If you want real results, go to a real shop.