Effective NA Power Mods

[Nah]

Originally Posted by tyler_win_photo

With the tune, try to go with something like Ecutek and get your car dyno tuned rather than just flashing it with something off the shelf. You'll net more gains. I've seen a peak increase of 7 whp and 6 ft-lbs of torque between a custom tune and an ots flash.

Ehh all in the tuner... but you can never go wrong with a dyno tune. OFT or ecutek

[TRAKRAVN]

Originally Posted by gramicci101

Ok, you're an engineer, so hopefully you can explain this to me. Why is drivetrain loss expressed as a percentage instead of a static number?

Say your car makes 200 bhp, and for ease of math it loses 20 hp (10%) through drivetrain loss. You do some mods to it and now it's making 300 bhp. You're still spinning the same gears at the same speed in the same fluid, so it should still only lose 20 hp, not 30 hp (10%), right? If expressing it as a percentage is correct, why would drivetrain loss go up just because power went up, when the workload to spin all the gears and whatnot hasn't changed?

The simplest explanation is more torque = more friction = more heat = more loss. The percentage comes from the individual friction sources which is a dynamic loss combined with the loss of the energy from all mass of the moving components. Accelerating a mass takes energy, accelerating it faster takes more energy, While the percentage expressed as drivetrain loss is not always 100% accurate it's a good way to oberserve its effects.

I hope that helps, I'm sure more knowledgeable people then me will chime in.

[justatroll]

Originally Posted by TRAKRAVN

The simplest explanation is more torque = more friction = more heat = more loss. The percentage comes from the individual friction sources which is a dynamic loss combined with the loss of the energy from all mass of the moving components. Accelerating a mass takes energy, accelerating it faster takes more energy, While the percentage expressed as drivetrain loss is not always 100% accurate it's a good way to oberserve its effects.

I hope that helps, I'm sure more knowledgeable people then me will chime in.

TRAKRAVN pretty much nailed it.

(note - for the other engineers out there, this is a simplified explanation)

The (static) frictional force is Force = u * N (where u = static frictional coefficient, N = Normal Force).

So the Frictional force (loss) is proportional to the force applied between the two surfaces by the frictional coefficient.

For steel, the static frictional force (lubricated and/or 'greasy') is ~0.16.
So the frictional force (loss) will always be approximately 0.16 times the force applied.
More power from the engine means more force within the trans (gears) but the frictional loss will always be 'in proportion' to the force applied to the mechanism by the frictional coefficient (or about 0.16 = 16%).

Since 'rolling' gears are somewhere between static and rolling friction, it is somewhat less than 0.16 or 16%.


It is more complicated than that as there are pure roller bearings, sliding bearings, and viscous liquids involved, but that is the basics.

[Lantana frs]

In short, baseline and tune on same dyno. Otherwise the delta is questionable.

[strat61caster]

Originally Posted by gramicci101

Ok, you're an engineer, so hopefully you can explain this to me. Why is drivetrain loss expressed as a percentage instead of a static number?

Say your car makes 200 bhp, and for ease of math it loses 20 hp (10%) through drivetrain loss. You do some mods to it and now it's making 300 bhp. You're still spinning the same gears at the same speed in the same fluid, so it should still only lose 20 hp, not 30 hp (10%), right? If expressing it as a percentage is correct, why would drivetrain loss go up just because power went up, when the workload to spin all the gears and whatnot hasn't changed?

The other piece of the puzzle not mentioned is power is work performed/time, so yes, 200 hp at 50 mph shouldn't have any more frictional losses than 300 hp at 50mph, everything *should* be moving at the same speed in that instant, but power is not an instantaneous measurement, but rather a time averaged measurement, and so that 300hp is revving up the system at a quicker rate resulting in a higher absolute power loss.

[Ultramaroon]

Originally Posted by strat61caster

The other piece of the puzzle not mentioned is power is work performed/time, so yes, 200 hp at 50 mph shouldn't have any more frictional losses than 300 hp at 50mph, everything *should* be moving at the same speed in that instant, but power is not an instantaneous measurement, but rather a time averaged measurement, and so that 300hp is revving up the system at a quicker rate resulting in a higher absolute power loss.

Don't forget that to maintain a constant speed at your assumed 50 mph very little of that available power is being used. An 80 hp engine and a 500 hp engine both are producing, what, 7-10ish hp.

[Lantana frs]

Imo and from my experience, an otc tune coupled with a good el header will add about 20 horsepower and produce gobs of torque where there was originally none. Makes the car as fast and enjoyable as I could ever want. E85 even better but I wont risk it without a ff setup.

[GenRuleAThumb]

Originally Posted by justatroll

Sorry but our cars have ~12-13% drivetrain loss (MT).
Your peak wheel HP shows up as 174.6

174.6 * 1.13 = 197.3 HP
So your engine is outputting right about 200 hp

What am I missing?
(Hint: 'drag power' is way too high @ 41 hp).
41 hp of drivetrain loss on a engine hp of 216 is 19% loss

See what I mean about "tweaking dyno settings" to show power where it isnt?
And thats without being able to see any of the Rotating mass numbers.

This was at an 86 dyno day with 12 86 dynoing the same day, full results in northern California forum. Stock was 136 on same dyno for wheel power.

http://www.ft86club.com/forums/showthread.php?t=109320

[Spartarus]

Originally Posted by justatroll

Sorry but our cars have ~12-13% drivetrain loss (MT).
Your peak wheel HP shows up as 174.6

174.6 * 1.13 = 197.3 HP
So your engine is outputting right about 200 hp

What am I missing?

...Ah, don't be mad, but you're using the wrong equation there.

you can't multiply the dependent variable by a percentage to get the starting number. Do the proof, that equation isn't reversible. We aren't calculating a 13 percent increase from 174, we're reversing a 13 percent loss to solve for x.

to reverse a 13 percent loss, you would divide the 174.6 by .87, and end up with 200.69 HP, and a reversible, provable equation.

Anyway, you're still right about the 200HP thing. More so, in fact.

Anyway, I'm not here to argue about dyno settings. The only correct answer to any of that is bring a slip. Show the ET. That'll prove a few things, including whether or not a person has the skill to use any of the power their dyno queen makes.

[justatroll]

Originally Posted by Spartarus

...Ah, don't be mad, but you're using the wrong equation there.

you can't multiply the dependent variable by a percentage to get the starting number. Do the proof, that equation isn't reversible. We aren't calculating a 13 percent increase from 174, we're reversing a 13 percent loss to solve for x.

You are of course correct. But I was able to do the calc I provided in my head to see that the numbers did not make sense.
Doing it my way was close (enough for sanity check) but not correct. Thanks for the correction.

[justatroll]

Originally Posted by GenRuleAThumb

This was at an 86 dyno day with 12 86 dynoing the same day, full results in northern California forum. Stock was 136 on same dyno for wheel power.

http://www.ft86club.com/forums/showthread.php?t=109320

So, since the dyno guy fucked up measuring even a stock vehicle, that gives MORE credibility to your measurement?
I guess since they tested ALL of the cars with the wrong dyno settings so that makes it OK?

The 41 hp drivetrain loss is incorrect, there is no arguing that.
(unless you are dragging a dead horse behind the car of course)
This is not something the dyno can measure, it is a value the dyno operator has to enter (a priori knowledge)

Again, in a stock car we see 174 hp at the wheels (well documented)
The hp rating at the crank is 200 hp

200 -174 = 26hp
26/200 = .13 or 13%

WHY would that change just by adding a few hp at the crank?
Answer - it doesn't.

So IF you measured 174.6 at the wheels, you engine has almost exactly the stock hp rating.
There is just no way to argue that is not the case (other than 'the dyno guy said so')

[churchx]

justatroll: "in a stock car we see 174 hp at the wheels (well documented)" it's well documented about THIS, very specific dyno? Don't compare results of different dynos. Just don't.

[GenRuleAThumb]

Originally Posted by justatroll

So, since the dyno guy fucked up measuring even a stock vehicle, that gives MORE credibility to your measurement?
I guess since they tested ALL of the cars with the wrong dyno settings so that makes it OK?

The 41 hp drivetrain loss is incorrect, there is no arguing that.
(unless you are dragging a dead horse behind the car of course)
This is not something the dyno can measure, it is a value the dyno operator has to enter (a priori knowledge)

Again, in a stock car we see 174 hp at the wheels (well documented)
The hp rating at the crank is 200 hp

200 -174 = 26hp
26/200 = .13 or 13%

WHY would that change just by adding a few hp at the crank?
Answer - it doesn't.

So IF you measured 174.6 at the wheels, you engine has almost exactly the stock hp rating.
There is just no way to argue that is not the case (other than 'the dyno guy said so')

Im not trying to argue anything was simply adding my results to the thread and sharing more results to the op. Take it with a grain of salt, i am in no way a engineer nor an expert at dyno results. My car feels great and the jump to E85 was a noticeable difference in my experience with my car. I honeslty could care less what a dyno says about my car, i love driving it.

[justatroll]

Originally Posted by churchx

justatroll: "in a stock car we see 174 hp at the wheels (well documented)" it's well documented about THIS, very specific dyno? Don't compare results of different dynos. Just don't.

I am fully aware of the variation between dynos.
I was only using those numbers to calculate drivetrain loss.

BUT the drivetrain loss will NOT vary between dynos.


41 hp of drivetrain loss on a engine hp of 216 is 19% loss - this is wrong.