[6ixer]

As random as this may be anyone have a relative formula for hp calculation my text books is retarted is says horse power is equal to the diameter off the bore (inches). Squared mulltiplied by the number of cylandars then divide tht by 2.5...I think its supposed to be allthat but multiplied by 2.5 or the equation is wrong all together cuz I've seen one with pie (the math symbol pie) and diamiter is also involved ...

Anyone lol

[SlowSix]

horsepower is a derivative of torque and rpm I believe...

[6ixer]

Yeahh I found out tht there's somthing like ..

Torque plus rpm
Divide by
5225 or 5525 idk the last part

[Rich J]

I don't know it exactly, it involves your torque, and 5250 (the max torque rpm before hp takes over the powerband)

[6ixer]

But isn't there a "base hp" for an engine at rest...as in dle cuz if you take the above formula the end hp is like 43.9 but tht ddoesnt state any rpms

[6ixer]

but what I'm looking for is the formula based on stroke bored pie and number of cly..

[6ixer]

5250 just how happens to be where the redline is on OUR car buut is tht number based on every car or just the red line of anycar and I'm looking at it based on numbers on paper no rpms or anything

[ESG-642T]

Horsepower=torque*rpm/5252

[Tang Stang]

6ixer, there is no set formula deriving horsepower from displacement.

[6ixer]

Well I know how to find displacment/ci
Pie times radius squared times the stroke times the number of cyl
But wat I'm saying is if you taqke the vary first post I have if you take our 3.8 engine (bore and stroke) and u use the very first thing I posted and u multiply 2.5 not divide the end hp is 227.3 now according to what I read tht might be true if you take off ALL the drive belt items....alt/ac/steering pump ect ect...but again u need all them and tht 227would be at the crank of corse.just like the 190 is

[6ixer]

@ tang I'm not looking to get hp from displacemnt I'm just trying to see if there's away to take the bore and stroke and number of cyl and find relative hp

[ReverendDexter]

Originally Posted by 6ixer @ tang I'm not looking to get hp from displacemnt I'm just trying to see if there's away to take the bore and stroke and number of cyl and find relative hp

Same thing, lol


But to answer your question...

You could do something like: (Displacement/2 * rpm) * efficiency factor = power.

Efficiency factor being the percentage of energy you get from each gallon of gas that's actually turned into kinetic energy (instead of wasted as heat), and will be different for each engine.

But really, the formula is just

Horsepower = (torque * rpm)/5252

where torque is measured in foot-pounds.

And yes, it's *always* 5252. To answer the next question, "why don't dyno charts always cross at 5200 rpm, then?", the answer is because of correction factors. Dyno charts are almost never the raw data, they're adjusted to a "standard" temperature/altitude. That moves the curves around and changes where they cross.


If you have a known engine and want to see what the power would be like for a similar but different displacing engine, you can just do the math. I.e. if you stroke out a 3.8L that currently makes 190hp out to a 4.1L, assuming that the two engines are of equal efficiency (190/3.8) = (x/4.1), so x = 205 (not a huge gain, all things considered)

[Tang Stang]

A formula that uses bore, stroke, and number of cylinders to derive horsepower doesn't exist. Your "formula" doesn't account for efficiency, which is effected by things like cylinder head design, forced induction, camshaft profile, etc. You can have identical shortblocks (same bore, stroke, and number of cylinders) and have two wildly different levels of horsepower.

[JTs03v6]

What are you trying to accomplish with a formula?

[6ixer]

Thank you guys I. Thought there was one out there but again thanks again now to shift gears instead of creating another post ill ask her and I'm pretty sure its subjective but I'm disreguarding my cam build....I've finally come to a conclusion although I kinda alrdy did..tht..6ers r nice for dd and only good for modding if you have the $ and forced induction...so my question is
It temrs of the gts
94/95 5.0
99-04 gt....
"which is better"

To my understanding the 5.0 and 4.6 put out pretty close numbers in tq but the 4.6 I think makes more hp...but I also hear the 5.0 is under rated in factory specs for insurance rasons..

Go...
*ps I'm starting my saving acct mod and I'm about 25% done all gts go for 4.5-6k imat 1k now*
Proolly get a gt or a 4.6 dohc na cobra if % is right

[ESG-642T]

I would say the 5.0 due to the fact that you can buy parts dirt cheap and its simpler to work on a push rod motor than the sohc.

[ReverendDexter]

5.0 vs 2v 4.6 doesn't really have a best. 5.0 makes a little more torque, 4.6 revs a little higher and makes a little more horsepower (well, at least the PI motors do).

Do an H/C/I swap and they make near identical levels of power. Both like boost. Both have a "big brother" motor that swaps in relatively easy (351W/5.4L)

Only real advantage comes into play when you start chasing cubes; the pushrod motors take to it a lot better than mod motors do.

[6ixer]

So your saying in respect the 5.0 and the pi or 4.6 found in the 99-04 gts are pretty much the same power

well
5.0 <tq
4.6< hp
But there not much difference in power and you saidboth handle f/I well and h/c/I have the same out put

Advantage the 5.0 is a push rod so its easier to work on even tho the cam in the 5.0 is in the block but the cam in the 4.6 is over head in the heads...seems the other way

But like u said and after looking at the number the engines are relativly with in 15hp/tq of each other...so its just the preference is what the engine is in what car as in body style

[ESG-642T]

Originally Posted by 6ixer So your saying in respect the 5.0 and the pi or 4.6 found in the 99-04 gts are pretty much the same power well 5.0 <tq 4.6< hp But there not much difference in power and you saidboth handle f/I well and h/c/I have the same out put Advantage the 5.0 is a push rod so its easier to work on even tho the cam in the 5.0 is in the block but the cam in the 4.6 is over head in the heads...seems the other way But like u said and after looking at the number the engines are relativly with in 15hp/tq of each other...so its just the preference is what the engine is in what car as in body style

Yep take a 'noob' give him cams for a 5.0 and a 4.6 every possible tool and the internet I would be 70% chance he fucks it up for the 4.6 :p

[6ixer]

Well if all goes well ill have a gt by spring...most 94/95 gts are going for (approx and meadian value) of 3k and I got just under 1k and if *knock on wood* nothing big brakes on my car between now and then and I can afford the insurance...gt..in the rping....btw what's the stock gears in those bad boys cuz all I'm gunna do is keep stock mid pype swap mufflers andgear it