Don't understand, help please......
 

Can you guys, help me understand, How is it possible that I took my car to dyno and I put down 256hp this past Monday, then went back on Friday to dyno tuned my Z with new Iridium spark plugs and the best the tuner could do was 250hp.

humidity changes, dyno being a bit off, car not use to those plugs. many factors can affect a dyno run

Wrong heat range plug maybe? Temperature diff, humidity diff. Could be more than 1 thing.

6hp is within the range of error for most dynos. I wouldn't sweat it, since you have error plus all the variables mentioned above.

This are the sparks I used;

NGK Iridium one step colder - LFR6AIX-11

also the humidity the day I put down 256 hp the was 10% and the best run the second time around the humidity was 25%. Definitely a big difference in this department. How can I determine, How much hp I gain as a result of the tuned, if the conditions were differenyts. Any idea guys.

Is all anyone cares about the goddamn horsepower number? What difference does it make? How does the car feel? What are your 1/4 mile times?

Oh and by the way...

:+1:

As metioned a lot of things to take into account, that humidity difference is pretty big, also do we assume it is on the same dyno?

Unfortunately measuring horsepower is not an exact measurment that can be repeated to the same numbers. Also one step colder plugs are not needed for your application they are normally thought of being needed when you get 200HP over your stock power.

+1 to Wired.

Don't be a dyno racer ;)

It was done at the same dyno both times. I just wanted a number figure thats all but I'm happy anyways caused the car feels running much better. Thank you guys for all your opinions.

Exactly. If you make 3 dyno runs throughout the day, it would be normal to see a 1-2% difference between runs. Even things like tire deformation, and how tightly the car is strapped down, can effect measured power.

I wouldnt worry about it. :)

Why are you using one-step-colder plugs?

/\ /\ my question also??? I thought you only use one step colder for FI and Nitrous? That could be hurting you unless you have added something that is not in your sig.

So you guys think that I should it bought this spark plugs, LFR5AIX-11 instead of the ones I got.