Horsepower Calculator

[Forrest Gump]

This is an interesting website that will calculate your engine's theoretical horsepower:

GoFastMath.com, the free horsepower calculator

GoFastMath.com has a free and uncannily accurate horsepower calculator.

www.gofastmath.com

You'll need to know some of your engine's "numbers" though such as the head's intake max flow rate and camshaft spec.

My results were 385 hp @ 4854 rpm. I've not had it dyno'd but I reckon that is in the right ball park. I'd really like to know the peak torque figures.

It would be interesting for anyone who knows their actual dyno hp figures to compare the calculator's result.

 

[Roscobbc]

An interesting calculator Andy. I DO know the actual dyno figures for my engine and the calculation is very close - but you do need a lot of quite accurate information which one would be unlikely to get unless you know specifics.
My engine is a 489 cu in with flat tappet hydraulic cam - spec's are as follows ~ inlet .544" lift with 236 degree duration @ .050" lift ~ exhaust .536" lift with 240 degree duration @ .050" lift
Heads ~ Brodix Race Rite Oval port street head - approximate inlet flow @ .544" lift is 318 CFM.
Fact - Engine came off dyno at 571 hp @ 5850 rpm. (606 ft/lb torque @ 3875 rpm)
Inputing engine spec's in to Andy's calculator showed 546 hp @ 5397 using a typical Edelbrock hi-rise dual plane intake (so 25 hp down) however If I change the inlet manifold to a single plane Edelbrock Victor the figure goes to 569 hp @ 5616 rpm - so very close to the 'real' hp figures.
What was even more interesting was to input the Edlelbrock Victor single plane hi-rise inlet, swap-out the flat tappet cam for a roller equivalent but with an intake lift of .700" (rather than current .544") allowing maximum inlet port flow rate of 340 CFM (vs 318 CFM) the calculator shows a predicted 621 hp @ 6133 rpm.

 

[Forrest Gump]

Fact - Engine came off dyno at 571 hp @ 5850 rpm. (606 ft/lb torque @ 3875 rpm)
Inputing engine spec's in to Andy's calculator showed 546 hp @ 5397 using a typical Edelbrock hi-rise dual plane...

That’s good to compare Ross. I wonder if the calculator isn’t computing enough revs and giving a lower HP figure as a result. If you’ve got your Dyno plot it would be interesting to see if you do actually have 546 hp @ 5397rpm.

I know my motor is aimed predominantly at mid range torque but I still would have expected the peak hp to come at somewhat higher revs that it calculated, somewhere mid 5k.

One thing it shows is that you can easily get more hp by using a more wacky intake, although might make it less pleasant for normal road driving.

 

[Roscobbc]

This is where it all gets quite interesting (and possibly rather confusing) - I haven't got the latest dyno figures to hand - only original one where HP was shown as 528 where HP @ 5400 rpm was reading 513 - significantly and the torque and HP curves crossed at at this point. Guessing current HP @ 5400 rpm would be approx 540 hp.