what do you believe to be accurate?

percentage or set number

  • percentage

    Votes: 12 66.7%
  • set amount

    Votes: 6 33.3%

  • Total voters
    18
When I had my car dyno'ed my buddy (who runs the dyno) said something similar to the fact that changing wheels might free up Hp...but he told me that Numerically higher gears will yield more Hp. So me switching from 3.73 to 4.30 probably gave me a little extra. Maybe that is just thier dyno though...
 
lxfiveo said:
I'll take this one step further, who cares what it does on the dyno...you don't race dynos!:Track:


:owned: Ouch!!!!

J/k I agree whole heartedly with you on that one...The only reason I had my car dyno'ed was to get the a/f ratio right...which I accomplished...also picked up a few more ponies too! But Once again, I agree...:Track:
 
SQUEEZE&STROKE said:
:owned: Ouch!!!!

J/k I agree whole heartedly with you on that one...The only reason I had my car dyno'ed was to get the a/f ratio right...which I accomplished...also picked up a few more ponies too! But Once again, I agree...:Track:

Don't get me wrong, the dyno has very useful tuning purposes, but just building a car to get a big number on a dyno is ridiculous. For me, I would need to get a much tighter converter to put down big numbers on the dyno, yet then that same converter would be less than ideal at the track, resulting in lower ET's. For me, I'll take the mid 9 second pass over the 850-900 rwhp # any day!
 
It has been said that power put to the wheels is better to know than to the flywheel and I agree.

Others have said they don't care about rwhp cause you don't race a dyno and if your focus is on track performance ...... I gotta go with that thought as well.

however

For a street car combo ...... I find dyno results to be very informative :D

You can see how that street combo is gonna perform very quickly with just a quick glance at its curves :nice:

If you keep things constant like trans type, dyno type, sae standards, and the like between combos ......a dyno can be used to compare those combos and allow the data to speak for itself.

Dyno info is not the be all, end all, of everything :shrug:

Its just that for me .................

I've found that evaluation method much more reliable than things like .....

My best friends friend said
4.6 .................. I mean 5.0 mag said

or even :shock:

That Grady guy on StangNet said :rlaugh:

Factual, hard, data just seems to be more trust worthy :D

I'm done now :banana:

Grady
 
In my opinion, I would have to agree with the SET number or loss. I say this because, although i understand your points about how a more powerful engine acellarates-sp faster, and causes more drag, but i dont think that the extra power is really causing the drivetrain to lose more power, i mean its the same weight components, its just putting more torque through them......i say the set number
 
i've read all these resistance posts and i have this to ask.

if you put a lightweight flywheel--without any other mods--on a 5.0 would your rwhp decrease?
you are accelerating the engine faster, which you say would increase resistance.

after spending 12 weeks of school dynoing cars on a chassis dyno i saw many a stock vehicle climb on the dyno and put out--you guessed it about 30hp lower than the factory number. examples are as follows:

91 mustang--factory rating of 225hp--dyno 195hp
95 cobra--factory rating of 240hp--dyno 208hp
99 M3--factory rating of 240hp--dyno 215hp
95 t/a--factory rating of 275hp--dyno 240hp
88 325is--factory rating of 189hp--dyno 162hp

big deal you say--those are all around 15%. lets examine some factory hot rods.

06 Z06--factory rating of 505hp--dyno at vette doctors 474hp--approx 7% loss
03/04 cobras--factory rating of 390hp--typically dyno 360hp
03/04 mach 1--factory rating of 305hp--dyno at shm 278hp
02 camaro ss--factory rating of 320hp--dyno 305hp:shrug:

i do agree it is very hard to say 100% without back to back testing, but if you look at factory hp numbers vs. stock rwhp numbers, it is pretty convincing.

another important note is torque on all the vehicles above does not drop as much as the hp--very interesting.

i find this interesting due to the fact that the vehicles equipped with shorter or two piece driveshafts lose less torque.
 
Interesting numbers and data, BT.

I have to say that I have a hard time seeing raw data comparisons myself. As we know, tire pressure, how the car is ratcheted down, etc etc all can change the numbers. I still think the dyno is most useful for tuning and relative numbers (making changes while never unstrapping the car). Comparisons otherwise can have many additional variables.

None of that is neither here nor there. Just more BS.
 
Here is the thing. To turn the drivetrain, each component take a certain about of torque to start to spin it. That is the static friction. Now once it's going, you will have kinetic friction, which means the friction is going to change as the RPM's increase.

If you could calculate the kinetic friction for each component at various RPM's, you could make an equation for the total kinetic friction.

So basically the torque loss is going to be different at each RPM, my guess is less loss as the RPM's increase. But that torque loss will not be a flat percentage, more like an ever decreasing number.

For instance, when you measure the drag on the pinion when you are installing gears, you are literally measuring the static torque loss; the amount of torque that needs to be applied to just the pinion to make it turn. What was it, 12 in.lbs or something.

That's my take on it.
Scott
 
mo_dingo said:
Here is the thing. To turn the drivetrain, each component take a certain about of torque to start to spin it. That is the static friction. Now once it's going, you will have kinetic friction, which means the friction is going to change as the RPM's increase.

If you could calculate the kinetic friction for each component at various RPM's, you could make an equation for the total kinetic friction.

So basically the torque loss is going to be different at each RPM, my guess is less loss as the RPM's increase. But that torque loss will not be a flat percentage, more like an ever decreasing number.

For instance, when you measure the drag on the pinion when you are installing gears, you are literally measuring the static torque loss; the amount of torque that needs to be applied to just the pinion to make it turn. What was it, 12 in.lbs or something.

That's my take on it.
Scott


That makes sense...but it would be a different rpm than what the engine sees correct? Since the gears obviously change it.

I wonder how the the graphs look instead of just the peak numbers. I wonder if there is a bigger difference down low and a lower one up top...or maybe the other way around.