2k3 cobra vert

[2k3cobra]

Hot off the press.

385.4 rwhp
384.3 rwtq
3500 miles
Only mod is a K&N filter.

If we work with 15% drivetrain loss that puts 453.4 HP at the fly. Not bad for a car listed at 390 HP ;)

[gcassidy]

Hi Matt.
Where did you have your's dyno'd? I just got back from Excessive Motorsports in Manassas, where we got 273 rwhp/271 rwtq for my 98 with the C&L MAF (257 rwhp/264 rwtq stock). Is the 15%drivetrain loss pretty much across the board? Would it be accurate for me? I forgot to ask them that when I left.
If you get tired of that much power, I'd be glad to take that blower of your hands. He He.
Greg

[2k3cobra]

I had mine done at Springfield Motorsport.
www.springfieldmotorsport.com

15% drivetrain loss is the accepted standard I have heard from several sources including some people on this forum.

Now, if you think I'm giving up my blower you better not be driving; impaired judgement and all :p

[Ray Ackerman]

Great numbers! Our 03 Cobra's like this cold air.

[meldubose]

i put the upr cai on mine, the web site claims 27 hp. don't know if i got that but it sure made a difference. plus it sounds a lot loader.

[meldubose]

i meant louder.

[BlownVenom]

Originally posted by 2k3cobra
Hot off the press.

385.4 rwhp
384.3 rwtq
3500 miles
Only mod is a K&N filter.

If we work with 15% drivetrain loss that puts 453.4 HP at the fly. Not bad for a car listed at 390 HP ;)

are those numbers SAE corrected?

[2k3cobra]

Yes, that's SAE corrected

[gcassidy]

Okay, since I couldn't belong to the Society of Automotive Engineers unless they needed someone to drive the train, just what does it mean when hp is SAE corrected? And since I didn't ask when my car was dyno'd, is there a way I can find out if mine was? Thanks.
Greg

[BlownVenom]

Originally posted by gcassidy
Okay, since I couldn't belong to the Society of Automotive Engineers unless they needed someone to drive the train, just what does it mean when hp is SAE corrected? And since I didn't ask when my car was dyno'd, is there a way I can find out if mine was? Thanks.
Greg

this is from a website... (http://wahiduddin.net/calc/cf.htm)

The horsepower and torque available from a normally aspirated internal combustion engine are dependent upon the density of the air... higher density means more oxygen molecules and more power... lower density means less oxygen and less power.

The relative horsepower, and the dyno correction factor, allow mathematical calculation of the affects of air density on the wide-open-throttle horsepower and torque. The dyno correction factor is simply the mathematical reciprocal of the relative horsepower value.

One common use of the dyno correction factor is to standardize the horsepower and torque readings, so that the effects of the ambient temperature and pressure are removed from the readings. By using the dyno correction factor, power and torque readings can be directly compared to the readings taken on some other day, or even taken at some other altitude.

That is, the corrected readings are the same as the result that you would get by taking the car (or engine) to a certain temperature controlled, humidity controlled, pressure controlled dyno shop where they measure "standard" power, based on the carefully controlled temperature, humidity and pressure.


If you take your car to the dyno on a cold day at low altitude, it will make a lot of power. And if you take exactly the same car back to the same dyno on a hot day, it will make less power. But if you take the exact same car to the "standard" dyno (where the temperature, humidity and pressure are all carefully controlled) on those different days, it will always make exactly the same power.

Sometimes you may want to know how much power you are really making on that specific day due to the temperature, humidity and pressure on that day; in that case, you should look at the uncorrected power readings.

But when you want to see how much more power you have solely due to the new headers, or the new cam, then you will find that the corrected power is more useful, since it removes the effects of the temperature, humidity and atmospheric pressure and just shows you how much more (or less) power you have than in your previous tests.

There is no "right" answer... it's simply a matter of how you want to use the information.

If you want to know whether you are going to burn up the tranny with too much power on a cool, humid day, then go to the dyno and look at uncorrected power to see how exactly much power you have under these conditions.

But if you want to compare the effects due to modifications, or you want to compare several different cars at different times, then the corrected readings of the "standard" dyno will be more useful.



The Society of Automotive Engineers (SAE) has created a standard method for correcting horsepower and torque readings so that they will seem as if the readings had all been taken at the same "standard" test cell where the air pressure, humidity and air temperature are held constant.

The equation for the dyno correction factor given in SAE J1349 JUN90, converted to pressure in mb, is:



cf = 1.180 * ( (990/Pd) * ( (Tc + 273) / 298)^0.5 ) - 0.18


where: cf = the dyno correction factor
Pd = the pressure of the dry air, mb
Tc = ambient temperature, deg C

The pressure of the dry air Pd, is found by subtracting the vapor pressure Pv from the actual air pressure. For more information about pressures and calculation of the vapor pressure, see Air Density and Density Altitude.

The relative horsepower is simply the mathematical reciprocal of the correction factor.

[BlownVenom]

it usually says if a correction facror was used on the chart... you can call the shop if they always use the same one and ask them or they might still have the dyno on the computer if its a dynojet. there are different correction factors too "STD" is ussually higher than "SAE" correction. below ill post 4 graphs... one is uncorrected (actual horsepower), the 2nd is SAE corrected, the 3rd is STD corrected, last one is STD corrected but the smoothing is turned off. with the smoothing off you will get higher peak readings.

[BlownVenom]

sprry i put the wrong graph first. that one was SAE. this one is uncorrected

[BlownVenom]

this one is STD corrected

[BlownVenom]

last pic is STD with no smoothing (almost 20 more hp than SAE with smoothing (set to 5))

[gcassidy]

Thanks so much. I don't know how, but I kinda understand it. Actually, I had to have my son (in high school) help explaine it to me. I checked my chart, and it's STD. I still don't quite understand why they have 2 correction standards, when it's meant to equal out everyones readings, but that's ok. I know more now than I did before.
Greg

[BlownVenom]

Originally posted by gcassidy
Thanks so much. I don't know how, but I kinda understand it. Actually, I had to have my son (in high school) help explaine it to me. I checked my chart, and it's STD. I still don't quite understand why they have 2 correction standards, when it's meant to equal out everyones readings, but that's ok. I know more now than I did before.
Greg

multiple (i know of SAE,DIN,STD and EEC) correction factors because different groups believe one is more accurate than the others.