Doug a dyno doesn't vary 20hp on back to back runs, please don't spin this. According to you, we'll stop the proven method of dyno/track testing and just compare sigs on f150online all day. So who's got the most mods?

 

So Im a liar ....
Thanks
Unfortunately I'm not at home so I cant post the dyno sheets.
Even if the difference is 10 hp we have seen $500 mods advertised that are purported to gain less than that.

You are missing the point. As a vendor you know that vendors that are trying to sell something will make lets say 2 dyno runs without the part and 2 with the part. They are likely to pick the lowest stock dyno to compare with the highest modded dyno. Or another method would be to do the stick run hot and the modded run after a 2 hour ice down. Or they adjusted the air pressure in the tires or they flipped the chip or added race gas or opened the dyno bay door to let more cool air in....

The issues is that you never see all the variables accounted for. If an et decrease is claimed you rarely see side by side Slips with detailed weather info. All you have to do is hangout at the track with some GOOD bracket racers and yo learn all kinds of tricks to massage ET/MPH and traction.

So back to my earlier post. I don't believe sales people. I believe customers. If a large number of unconnected customers all have good things to say about a product that means a heck of a lot more to me than an undocumented claim by a vendor on the internet. ( a large number of independant similar reports becomes close to statictically meaning something, a heck of a lot closer than one guy who is looking for a certain outcome testing one truck at one dyno ) Which going back to the prior post, is to me one of the big advantages of a forum like this. The chance to compare information with lots of people.

Doug

 

Given up to a 5% variance on a 400hp motor (aka 390-410) and a mod that actually gives you 5hp, you need to to roughly 10 (before and after) runs to prove a statistical significance.

Even with only 5 runs before and after and your 5% variance, you've got a 65% chance that it is not a random wierdness.

I've never seen the dyno vary by 5% (unless you use it wrong).

Lowering your dyno error will significantly help these results. If your dyno is "only" off by 2.5% (aka 10hp variance) and you do 5 runs before and 5 after, you have a 93% probability that the mod added the power and not luck.

With a 2.5% dyno error and 3 runs before and after, you've got a 76% chance that the mod caused the hp increase.

In other words, I want to see some dyno runs

Coldie

 

 

I'm pretty confident that I could do three dyno pulls on the same day with the same mods and have them all within 2hp of one another. It's all in the technique...