[BrigadoonB]

I went to the same dyno before and after upgrades. 04 sti - mustang dyno

243whp and 231tq - bone stock
288whp and 286tq - after upgrades

1. Do you simple add the difference from the upgrade numbers to stock numbers and then add then to stock hp and tq specs?

example:
288-243=45 increase; 345hp
286-231=55 increase; 355tq

OR

2. Do you do a ratio calculation for the increases?

example:
243/300=81% ; 288/(new hp)=81% ; new hp = 356
231/300=77%; 286/(new tq)=77%; new tq = 371

My 2 cents:
we should be using ratio calculations to get a more accurate hp/tq numbers because its not a 1:1 ratio.

Your thoughts....

[normansti]

thats a good question that I cannot answer but I would like to know what mods you have if you dont mind

[BrigadoonB]

I very curious to see what people answer here. I hope a lot of people cime in because I want to see how people state their numbers.

Just FYI: dyno days were within 5 degrees of temp. 91 degrees average

My car:
APS CAI
Ecutek - 17lbs boost
Rear Turbo XS with Magnaflow muffler - sounds great

[Tortfeasor STi]

Drivetrain inefficiency or losses are a percentage of total power. So to approximate new hp #s you should use the percentage of drive train loss to calculate the new hp numbers.

[BrigadoonB]

then how would you do that exactly?

[Tortfeasor STi]

Just as you did in the original post. 300/243=x/288. That should cover your correction assuming subaru's facotry rating is accurate.

All a dyno is really is an aproximation of power production based on your acceleration of a given mass. It varies from dyno to dyno and day to day. Like 1/4 mile times and speed they are all usefull tuning tools but hardly dispositive.

Because you have before and after readings on the same day for your modifications you can be sure you are making a bunch more power. And really, that is what it is all about. Now take it to the track and see how much faster you run. between these two measures you will have a pretty good idea of your car's relative power production.

[arsonall]

many times you hear that a certain part adds "X" amount of HP. typically, they state that because that is the typical percentage gain over stock. with other parts, that number would be more or less, depending on tuning. i would go with the percentage...

[Nachos Libres]

Originally Posted by Tortfeasor STi

Just as you did in the original post. 300/243=x/288. That should cover your correction assuming subaru's facotry rating is accurate.

All a dyno is really is an aproximation of power production based on your acceleration of a given mass. It varies from dyno to dyno and day to day. Like 1/4 mile times and speed they are all usefull tuning tools but hardly dispositive.

Because you have before and after readings on the same day for your modifications you can be sure you are making a bunch more power. And really, that is what it is all about. Now take it to the track and see how much faster you run. between these two measures you will have a pretty good idea of your car's relative power production.

Yeah, this is what I do. Like he said, a dyno is really just an estimate anyway, so there's no need to be specific and pull out of the laws of dynamics and all that other stuff.