# Thread: Working out horsepower from the data?

1. ## Working out horsepower from the data?

Hi guys,

Maybe a stupid question.

Is there a formula to use to work out a rough idea on how much horsepower the engine is producing?

Using data like inj size and duty cycle, lambda, RPM, Boost, etc.

2. I sure there are somesort of rough estimates with all things been equal ( within 20 ponies) based on Motec's dyno tuning graphs. I'd be keen to see as well. Apparantly I am at aound 300ish with 12 to 13 psi ET low boost wheel and 8400rpm when I had my prop pitched down alittle running a base 95 motec tune.

You guys pushing 18+ Psi and 8700+ rpm'smust be closer to 400 ponies or more I recon.

Good question.

3. Yes,

Theoratically you need 5cc of fuel to produce 1HP at 50psi fuel pressure. so looking at your injector duty cycle and knowing your injector size you can calculate your estimated horsepower. How?

for example:
your Injector duty cycle 70%, Injector size 1000cc at 50 psi fuel pressure

70% of 1000 = 700cc (thats what you are using from the capacity of the injector at 50psi)

so,

1hp = 5cc
xhp= 700cc, x= 140hp per cylinder so if you are taking of a FZR engine its 140 x 4 = 560HP (estimate)

Hope my calculation is correct.

4. I dont think that is right some how.

At the moment im running 1000cc injectors at 80%+ duty cycle and getting a 0.83 Lambda.

I dont know what the standard fuel pressure is though.

There is no way this thing is 800hp.

There must be a calculation where....

Injector size and duty cycle
Lambda
RPM
Boost

= so many hp.

5. Here is my recolection on this stuff.
Its not that easy unfortunately
the 5cc per hp figure assume near perfect of la 1.00 or there abouts
So we use 5.5cc per hp at la .9
Fuel pressure doesnt matter as that simply alters the flow of the injector which you have to know to bring into the calculation.
So 1000 cc injectors are 1000cc injectors at a certain pressure, if that pressure is 50 psi then yes use 1000cc as your base rate
Next problem is 80% duty is not 80% of injector flow. Why? You have whats called injector dead time, this is the time that the injector takes to open.
The lower the voltage the more time it takes to open and therefore the less fuel flowed for a given duty cycle.
Next problem, IGN timing greatly effects power, the 5.5cc / HP rule assumes perfect ign timing, a lot of you are well back from that.
Next problem, air density, good vs bad intercooler, 30HP between 2 diferent aftermarket intercoolers, admitadly less fuel on the bad cooler but not proportionaly.

What I can tell you is this

From doing it

On our Dyno, (usually reads lower than most)

Stock yamaha engine 200
MoTeC ECU 245 at 9K
MoTeC 200 kpa boost stock Intercooler 300 at 9k
MoTeC 200 kpa GOOD Intercooler 350 at 9k
MoTeC 225 kpa Good Int Better Cams etc 400 at 9k
MoTeC 225 kpa Good Int Turbo 440 at 9k

Those are the figures with correct ignition and fuelling on 98 octane fuel
That will give you as much idea as any other calculation

6. Thats great pete.

Thanks for clearing that up.

7. Cool stuff.

8. So what did you have Rick in kph at your 91.1mph run? cant remember....?

9. Was running 245 Kpa at 8800 RPM!

Def making some power thats for sure!

10. Originally Posted by rick xp
Was running 245 Kpa at 8800 RPM!

Def making some power thats for sure!