Dyno power vs weather

[GTS_365]

Generally speaking, will the same car on the same dyno make more power on a cold day compared to a hot day, or will the SAE correction factor adjust accordingly?
If so, can the correction factor correct too much and even show higher figures than normal? I understand when driving on the road the difference in performance is chalk and cheese, but just wanted your thoughts/experience on the dyno. Cheers.

[sportwagon]

Im far from an expert but my car made 25rwhp less on the same dyno week apart,the first run was at night and the temperature was 19 second run a week later it was 38 and id lost 25rwhp.

[C4B]

The correction factor is designed to adjust for the atmospheric condition changes so theoretically the same car should produce the same "on paper" result every time, but it also brings in the ability to fudge the figures.

I seem to recall some ex-sponsors of the forum were prone to strategically placing the air sensor probe to make it appear hotter than it really was to provide happier results.

The only way to truly compare 2 cars is run them on the same dyno one after the other. My GTS will produce anything from 310 - 340rwkw's depending on the dyno and the day.

[whitels1ss]

The correction factor is designed to adjust for the atmospheric condition changes so theoretically the same car should produce the same "on paper" result every time, but it also brings in the ability to fudge the figures.

I seem to recall some were prone to strategically placing the air sensor probe to make it appear hotter than it really was to provide happier results.



Yeah, seen that done before & some "tuners" are still doing it! .:lmao:

[IJ.]

1st thing I look at when someone posts a sheet... too many Disney Dyno's out there.

[whitels1ss]

1st thing I look at when someone posts a sheet... too many Disney Dyno's out there.

I also know of one tuner in Adelaide who prints out extra high dyno sheets to make the customers think he has done a fantastic tune yielding excellent power
& gives the customer a free Christmas light display with every tune!.:xmas::xmas::xmas:
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It lights up on the instrument cluster nearly every time the car is driven.:lmao:

[IJ.]

I remember making 399rwkw at one point with my 7M Supra, my operator asked if I wanted the chart to show 400?

He seemed surprised when I said it didn't make 400 so no thanks..

[GTS_365]

The correction factor is designed to adjust for the atmospheric condition changes so theoretically the same car should produce the same "on paper" result every time, but it also brings in the ability to fudge the figures.

I seem to recall some ex-sponsors of the forum were prone to strategically placing the air sensor probe to make it appear hotter than it really was to provide happier results.

The only way to truly compare 2 cars is run them on the same dyno one after the other. My GTS will produce anything from 310 - 340rwkw's depending on the dyno and the day.

Thanks. So what would be the reason sportwagon lost 25rwhp?

[white lie]

Accurately placing the sensors so it didn't over compensate for the higher temp.

You can "make or lose" power very easily on a dyno. Simply strapping it differently can produce hugely different results.

[amckiwi]

also different wheels or tyre pressures as well

[C4B]

Thanks. So what would be the reason sportwagon lost 25rwhp?

Dozens of things could make that much difference.

The temperature of the car makes a huge difference. If you drive in and throw it on the rollers straight away you'll lose a heap of power compared to if you have the car parked for an hour to let everything cool down.

There was a stage in the early 2000's where there were dyno days ever other weekend in Brisbane. We used to go to a few after I got the stroker build for my GTS (this is back in the days when a tuned LS1 would make 220rwkw's). If you arrived and drew first run you were screwed because the car would still be heat soaked from the drive there.

[Micks]

Thanks. So what would be the reason sportwagon lost 25rwhp?

Everything else being equal I'd say an increase in ambient temp & engine heat soak would be the culprit there.

[amckiwi]

Could even be the age of the fuel in the tank

[feistl]

Not strictly relevant, but ive been amazed how much difference the heat makes to a NA car.

Ive been driving my VY Wagon around this week on LPG with the Aircon on and 41 degree outside temp the car feels bloody sluggish (Especially with heat soak). Compared to a few hours later when airtemp was ~18 degrees and less heat soak it was an amazing difference.

[GTS_365]

Yeah no doubt the hot weather kills performance, I have plenty of timeslips to prove it. My question was more related to the correction factor on the dyno, i.e. does it correct 100% accurate or does it correct too much/too little on hot days everything being equal. Everything being equal as in same car, same wheels, same heat soak, same dyno strapping, same tune etc. Only difference is 35 degrees vs 10 degrees ambient temp.

[IJ.]

Yeah no doubt the hot weather kills performance, I have plenty of timeslips to prove it. My question was more related to the correction factor on the dyno, i.e. does it correct 100% accurate or does it correct too much/too little on hot days everything being equal. Everything being equal as in same car, same wheels, same heat soak, same dyno strapping, same tune etc. Only difference is 35 degrees vs 10 degrees ambient temp.

Corrections are a bit of a guesstimate but should be within the Dyno's +- error range.

[C4B]

Yeah no doubt the hot weather kills performance, I have plenty of timeslips to prove it. My question was more related to the correction factor on the dyno, i.e. does it correct 100% accurate or does it correct too much/too little on hot days everything being equal. Everything being equal as in same car, same wheels, same heat soak, same dyno strapping, same tune etc. Only difference is 35 degrees vs 10 degrees ambient temp.

Not in my experience. Stinking hot days will yield lower corrected results. On the other hand, freezing cold days seem to correct pretty accurately.

My GTS will spin up the same corrected numbers in temps from 10c to 30c, but once you go beyond that all bets are off.

[GTS_365]

Thanks for that good answer.

[LuisS]

Very dependent on how the tuner has set up the intake air temp table.

Some will typically pull out 2-3 deg from the spark map at 40c , this will have the corresponding effect on the power figure.
A well calibrated dyno has pretty accurate compensations built in