Okay, can someone explain to me why you can't just add up the total of the hp of each mod and estimate the whp from there.

For ex.

intake ~5hp compare to stock
Kinetix plentium/CF cat ~10hp compare to stock
rear axle exhaust ~5hp
y pipe ~5hp
pulleys ~10hp
headers ~10hp

total 45 extra hp. so if your car is auto (225whp) so shouldnt it be making close to 270hp?

 

thats ricer math...it never works that way sadly. only way is by dyno #'s. those #'s are only if those parts are just added by themselves im assuming. but when parts start mixing w/ each other it does not mean that they will always work perfectly together and give you the 10hp or w/e that it states. when working together, it wont work that way

 

i wish it worked like that

 

i know it doesn't but i'm trying to figure out why not. If I'm freeing up flow then shouldnt it add up or close to it?

 

the reason it doesnt work like that is b/c mechanics isnt simple math. you might add a Z tube and dyno will show +5 HP. Then you add a spacer/plenum and expect 10-15HP, but you only get 7 when you dyno. Thats b/c some mods work together, and others offset one another. As mentioned, only way is Dyno before/after. Sure I can add up my intake/spacer/pulley/y pipe and expect 25 extra HP. But realistically with those mods...I might have like 15 extra HP???(just to toss out #'s, no i havent dyno'd but I think 15HP for Ztube/PC/3/8 spacer/Crank pulley and Y pipe is a safe assumption based on others data with similar mods). Now again every car is different and every car pulls a different # stock so even my 'assumption' isnt an accurate one.

 

Because there isn't an unlimited supply of gains available.
Add ons don't make HP... they can only improve efficiency

The more you push the limits, there are 2 certainties.
1. gains get smaller
2. they cost more per HP gained

 

I hear that!

 

In regards to your statment about "add on don't make HP, they can only imporove efficiency." How so? I think you need to clarify the "efficiency" part. Volumetric efficiency? SMOG effieciency? etc? Add on's do make HP, increase of VE= more HP.

 

The reason you can't add up the HP gains is because each manufacturer's claims of max HP gains likely come at DIFFERENT RPMS and depend upon the set up of other components (i.e. what other mods) exist on the vehicle.

So, if a cold air intake adds 7HP, it may do that 5800rpm. Racing pulleys made add 10HP at 6100 rpm, headers may add 12HP at 6000 rpm, etc. etc.

Well, there will likely be a reasonable HP drop for those add-ons somewhere on the RPM range. Perhaps when headers are making their maximum of 12 HP at 6000 rpm, the cold air intake (when tested on it's own vehicle for mfr claims, was making an additional 5HP (instead of 7HP). Get it?

The other variable is the existence of other modifications. The is especially true with air flow. If you're a manufacturer testing a plenum on a vehicle with a stock intake and stock exhaust, that potential air intake for that plenum at various RPMs may exceed the air that can be expelled by that stock exhaust. So the difference between a stock plenum and an aftermarket plenum may only show about 3-4hp. But it's not the plenum's fault. With the stock exhaust, the plenum can only take in so much air because the bottleneck is the exhaust. Now, take that same plenum and put it on a car with headers, hi-flow cats, and a more free-flowing exhaust, and now you may have the opposite scenario. Now, the exhaust may actually have the ability to expell the same or more air than what the plenum can take in, allowing you to see the maximum gains available from the plenum.

This is why you may see a manufacturer advertise its large gains with a product when used in conjunction with another product that removes the bottleneck.

These are the two main reasons why you can't just add up manufacturer claims of HP gains as you add these modifications to your vehicle.