Build me a Small block

Tom - I’m sorry to sound like a know it all - but your post proves my point about folks not understanding that Moroso is an approximate FLY wheel HP reference tool – There are three basic parts to the proof of what Im saying.

To be specific:

First part –

Knowing how it works and what data it uses –

The main thing to be aware of is – the essential information for the slide rule are derived from experiential analysis - NOT physics.

History - the FLY wheel HP from factory engine dynos, MPH, weight and ET coefficients were all gathered by a guy named Huntington - from data collection on thousands of qtr mile runs – where the only known hp output was fly wheel., sourced from factory stats and engine dynos.

Go here if you want the full history -

http://www.stealth316.com/2-calc-hp-et-mph.htm

He accumulated all this data and created a ‘constant”, and arrived at a general formula to align ETs and Fly wheel HP from MPH and Weight etc.

So in summary - The Moroso uses a constant derived from averaging data – it simply draws a average from the inputs – weight/MPH and known Fly wheel HP in each case…depending on what you want to know.


Part 2

You said - .

“Not sure how they can figure Engine HP since all combos are different(drivetrain losses) it would seem that REAR WHP is an easier calculation.”

Click to expand...

I’m afraid this thinking is backwards – Here’s why:

1 - The fact is that drivetrain losses occur mainly through the transmission and the differential – agreed?

2 – You also agree and are correct in saying the Moroso can’t calculate drivetrain (Trans/diff) losses from car to car,

Conclusion - Therefore, this makes it logical that the Moroso calculates FWHP, using known weight, FLY WHP and MPH coefficients as I explained above.

I think that’s pretty logical.

Part 2B :D

Now here’s another IMPORTANT (and complicated) point –

Why are the Moroso readings "low" for FW HP?

OK, so we now know - that the Moroso calls upon a data bank of verified factory or dynoed FLY wheel HP and uses a constant to cross reference against best case ETs, weights and MPH etc.. But here’s the kicker –

1 - Factory / engine dyno HP ratings that were used to create the Math constant were without alternator, air con, fuel pump etc –

BUT –

2 – The MPH/Weight coefficients were taken from cars running drivetrain- so losses had an effect on the formula -

So what’s the result?

Conclusion – Using the two different sources of experiential data corrupts the formula, and the end product is that the Moroso provides very conservative FW HP estimates.

This is why the “lowish” Moroso readings make people THINK its RWHP –

BUT, it is not – it is still a cross referenced FLY wheel read out, as that was what was used to genrate the formula to begin with!

Read on for the proof –


Part 3

– For example –your car ran 109mph

1 - Moroso says appx 385 Fly wheel for a 3900lb car (including driver) at 109 mph

2 - Truth is, that’s pretty close to what your average factory Hemi was probably putting out if you consider air-con, mechanical pumps etc.

.......so the “claimed” 425 was more than a bit unrealistic by the time the engine is in the car and driving the generator, fuel pump etc..

Now on to your second point –

“I'm not a rocket scientist though. I think most factory E-body Hemi cars ran under 110mph in the 1/4 and they were hopefully more than 400 Engine hp.”

Click to expand...

OK, I’ll play along, and prove how we know that the Moroso IS FWHP – just so you can tell others LOL! –

How? - We simply do the math in reverse:

Lets assume Moroso says its Rear wheel HP –

1/ It says for 385 "RWHP" – you should be running 109 mph

2/ Using 20% losses through trans and stall - 385 RWHP = appx 480 FWHP. (and probably more as 20% is very conservative for a 727 trans and stall – rule of thumb for most racers is add 120 HP)

Conclusion - If we assume the Moroso is REAR wheel, we have to agree that factory Hemis produce 480 – 500HP HP at the fly……I hope we both know that just isn’t the case? - Because we both know that 480 FWHP engines are good for low 11 ETs.

Soooooooo,

The only way the calculator can work correctly is if its understood that it is a very CONSERVATIVE FWHP calculator.

I agree - there are plenty of situations where the Moroso doesn’t check out perfectly on FWHP – Ive explained why in part 2B-

BUT - you only have to reverse the equation to realise there is no way on earth it can be REAR WHP.

Here’s another example –

Fact - My car is 3600 with me in it (had it on a weigh bridge),
Fact - Runs a flat 13 at 103 mph.
Fact - Rear Wheel dynoed at appx 265 RWHP.

Using the Moroso, it says at weight/MPH I’m making around 310-325 FLY HP.

20% losses from 320 = 270 REAR WHEEL almost exactly what the RW Dyno said. – so I’ve now verified that the Moroso deals in FWHP.

Lastly – and just a note - Don’t confuse Gross HP (without alternator, fuel pump etc) and Net SAE (with alternator etc) with RW and FLY HP. These terms mean different things to RW and FLYwheel HP.

FWIW, Gross and Net are BOTH taken at the flywheel

(Apologies if you already know this - but I thought I betetr clear it up)