Dyno results (Engle Cams shoutout)

[daytonalo]

I have a 70 440 that I'm about to get done , it has stock 906 heads . Could I use this cam , my stock heads and rods along with my steel crank and have a comp ratio of 10.75 and make almost the same HP & TQ ? Yes I know a little loss for the stock heads and I'm going with a six pac and this is a 4 speed application . Never used anyone else besides comp cams , why should I use Engle ?

Larry

[Rolling_Thunder]

Well - with this combo the heads add a great deal of horsepower - with stock 906 heads you'll be looking at about 450hp and 490tq...       

Why go with Engle cams ?  Because they can be tailored for best performance - they are not mass produced cams that are made to work with a generic set up....

Plus I've never had an Engle camshaft go flat - wish I could say the same thing for Comp

[daytonalo]

What would you say the absolute max comp can be with iron heads and above combo ? 11-1 ?

[dwbiggs]

That dyno sheet ever get posted?

[68pplcharger]

Quote from: Rubberduck on October 26, 2007, 02:07:39 AM
Quote from: firefighter3931 on October 24, 2007, 06:49:58 PM
Quote from: Rolling_Thunder on October 24, 2007, 12:19:54 AM
Ron - how would you calculate from a chassi dyno number to flywheel hp on a 4-speed car ?  take 75% of the number you believe to be actual ?     ie...    (guess) 556 x 75% = 417rwhp  ?   That is how I arrived at the numbers...        I remember it was 416.8hp and 442tq...     at the wheels...             



That's probably pretty close....a 25% drop from the crank to the rear wheels is reasonable. The problem being is that Chassis dyno numbers can be all over the map. Some read high while others are very conservative. An engine dyno can also be inaccurate as well....depends on the calibration/operator and correction factors. 

Regardless of what the readings are/were....that is a pretty stout combo and i'm sure your customer is happy. Again, very good job ! 



Ron


Why do most people say you loose about 25% between engine and rear wheels?
Certainly the transmission, driveshaft and rearaxle rob power.
Just an example:

You run a car on a dyno with a 100hp engine you might get 75hp at the rear wheels. That´s a loss of 25%.
All the parts between engine and rear wheels take 25hp.
Take the same car and only change the engine with 500hp.
Now take away the 25%. You should have 350hp at the rear wheels. The same transmission, drive shaft and rearaxle now robs 150hp
compared to the 25hp on the 100hp engine?

This is why I don´t believe in that % stuff.

If it takes 25hp to move all the parts, it always takes 25hp no matter what engine.

Correct me if I´m wrong.



Mario



Efficiency is a ratio of ouput over input and will always be a percentage. Consider the input that is put into the car coming from the flywheel and the output is what you get at the rear wheels. A percentage is lost throughout the drivetrain, not a fixed amount. If the drivetrain is 75% efficient, then a 25% loss occurs. I do know that efficiencies do change at different loads, rated efficiencies are usually full loads. 75% is just a good estimate.



I wanted to add to the efficiency I/O = E equation. That is very true, the percent efficiency is the same no matter what the horsepower of the engine. Yes, it does take a certain horsepower to move a particular drive train at a constant speed or rpm. The horsepower of the motor, in this case, would have nothing to do with the horsepower loss. i.e. The 100 hp motor would only loose 25 hp, in this case, as a 500 hp motor would also loose only 25 hp. They would only be outputting the same hp in each case to maintain that constant speed.
The horsepower loss would definitely be different between the two motors because of the acceleration difference. The inertial mass, of all the drive train parts, play a role and viscosity of the rear end and transmission fluid. Newtons 2nd law of motion f=ma "Force = mass times acceleration" drives the horsepower loss. This is the basis for Input/ Output = E. There are many external influences that can change the % loss, if all physical characteristics are the same i.e. speaking of the same car . the temperature of the parts and fluids to mention one variable. 16-18% is a general loss for most manual transmission and 20-22% (i've heard up to 25% for large stalls)for auto trans. These are very general because there is no real way to capture the other parts involved without empirically testing the car in question. I hope I've done  descent job of explaining the percentage loss theory.

[68pplcharger]

Sorry my Quote paste didn't work. My reply is the last paragraph

[SeattleCharger]

Sorry my Quote paste didn't work. My reply is the last paragraph

question.  you say this:
"The 100 hp motor would only loose 25 hp, in this case, as a 500 hp motor would also loose only 25 hp. They would only be outputting the same hp in each case to maintain that constant speed.
The horsepower loss would definitely be different between the two motors because
of the acceleration difference. "

  ok, so it isn't a percentage at a constant speed, its 25 hp., for your example.     so the percentage loss is only under acceleration?  the 100 hp and the 500 hp engine all of a sudden go from losing 25 percent at cruising speed to the 500 hp engine losing 125 hp?(25%) under acceleration?, and the 100 hp. engine losing 25 hp(25%)?  this seems a little confusing that spinning all the rotating assemblies, rear, trans, etc. drains the 500 hp engine that much differently from crusiing to acceleration, while the 100 hp. engine has no change in power drain between cruising speed and acceleration speed.    see what I mean?
Nate

[68pplcharger]

Nate,
don't take the example to literally, it's just an example. Think of it this way... The drive train has a given rotational mass. The faster you accelerate that mass the more horsepower it absorbs. Power = W/T where W is work and T is time or (force * disance)/ time . ex 1 horsepower = 550 ftlbs/second. So the faster you move the rotational mass three revolutions, for example, the the more horsepower it takes. I think you would agree that the 500 hp motor would accelerate the same drivetrain quicker therefore take more horsepower looking at the equations.

[SeattleCharger]

thank you, ok, that makes sense

[68pplcharger]

No problem... Physics is not so easy to explain or understand for that matter.  Thats why I like Cars so much, they are a constant problem solving hobby.

[SeattleCharger]

heh, yes, true. 
   I was good at math and physics in highschool, but I wasn't understanding this with the equations.  They are interesting to look at, in applying them to this scenario, but this sentence you wrote, below, which seems so simple and kind of obviouse now, heh,  is what finally turned on the light:

  " I think you would agree that the 500 hp motor would accelerate the same drivetrain quicker therefore take more horsepower looking at the equations."

[elacruze]

The largest variable on chassis dynos is tires. As you make more power, you need larger, stickier tires and have to tie the car down much harder to the base, increasing rolling resistance. While dynoing our racing sportster, we would see as much as 2hp difference between track use air pressure (28-36psi) and max inflation pressure (52psi iirc). We made about 63hp, so 2hp is over 3% change. Consider the effect on something making 10 times more horsepower with 10 times more tire footprint. Made worse is tire construction and rubber compounds demanding different pressures to maintain traction.

When I get mine to the dyno, I'll try to remember to run a test; after it's all dialed in, we'll reduce tie-down pressure and increase tire pressure until it spins to see how much difference it makes.