I only use dyno numbers to see what kind of effect a modification or tune has had on my car. Most people would probably laugh at my car's current torque curve, but most people also don't account for gearing...

l8r)

 

A few comments:

1. The dyno number is an important before and after number. I do not nor do I intend to drag race. I cannot tell my power that way, so I must use the dyno. Personally, I do not car about peak numbers, I look for area under the curve. Did I gain power in the entire area under the curve or did I lose here and gain there. There are a lot of guys here who install big turbos (GT35r and what not), but they do not do a before and after dyno. when you look at the dyno sheet you see that they have lost power in the low and mid range and gained power from 5K to redline. It is great for drag racing, but lousy for daily driving and on the road course. For me, if a turbo kit make me lose power in the mid range then I do not want it.

2. The purpose of corrected numbers is to allow comparison between dyno sheets. Let us say you dynoed your car in January and you got 300 whp and then you added cams and dynoed in June and got 350 whp, all other variables being equal. Using the same correction on both dyno sheets will allow you to figure out how much power you have gained despite the change in temperature between January and June. Basically, both dyno runs are compared to a base SAE, DIN, STD correction and then compared to each other. That is all what the correction does. A properly done correction keeps environmental factors the SAME between dyno runs on the same dyno.

Using uncorrected numbers only tells you what your car put down on that particulary day, time, temp and altitude. It is just a snapshot; you lose the power of comparison.

Having said that, there are those who cheat with corrected numbers. But if you are honest with yourself and the dyno is properly calibrated, then there is no reason NOT to use corrected numbers.

 

Huh? No, what I'm saying is that MY TRUE POWER is 300whp/337wtq. That is exactly what I put to the ground here in Colorado at 6000' elevation. The ridiculous SAE correction is completely false for turbo'd cars, because it is designed for N/A cars. That's why I don't claim 380whp. Any Evo owner with a clue would know that running 12.30@108 is nowhere near 380whp. My highest trap speed here is 109.5mph, which is _exactly_ right for 300whp. 380whp would yield 116-117mph traps and mid 11s, but I am nowhere near there. So, why would you respond so harshly by asking me if I'm lying? I'm doing quite the opposite - I'm making the proper claim instead of claiming huge, altitude-inflated SAE corrected numbers.

NJ, that's all nice and theoretical with the SAE/DIN/STD conversions, but they're not accurate. It has nothing to do with being properly calibrated, because those corrections are not proper for all cars (N/A, S/C, Turbo, N2O). I always use uncorrected, because I only care what I'm really putting to the ground. Yes, I know that on a 100-degree day, I'll put down less than on a 50-degree day, but so what? The track sure doesn't care what my corrected numbers are - it only cares what my tires are telling it when transferring my power to the ground. Yes, the corrections can sorta help with making comparisons before/after mods in different conditions, but it's just a ballpark - those corrections are not accurate for our cars. My 1.26 correction here in CO is a great example of that...

 

I think what NJ was trying to say is that even though the 1.26 correction factor in CO is useless when comparing your dyno run to a dyno plot obtained at sea level, it _is_ useful when comparing your dyno runs on the same dyno, but on different days.

l8r)

 

The drag strip is your dyno. I DO NOT drag race, so how do I know my power?

They are not accurate because unethical dyno operators misuse them. You can use a different correction than SAE for a turbo. Most dyno sheets I see use STD. Youcan use SAE for NA cars and STD for turbo cars. Furthermore, if you are using the same correction, say STD, on your car all of the time, then there is no reason for it to be inaccurate.

You are making your dyno run worthless if you only use uncorrected. Let me explain. Let us say you dynoed in colorado today and got 300 whp and the temp was 95 degrees. A weak later you added cams, the temp goes down to 75 degrees and you dyno again and you put down 340 hp. The hg and time are the same. The only diff is the temp. How much power came from the cams and how mcuh power came from the temp drop? You cannot tell if you use uncorrected numbers. If you use corrected numbers, however, you will hold temp, hg, constant for both run and you will be able to know how much power the cams put down. Can you compare the two dyno sheets that are separated by one week if you use uncorrected numbers? NO. You simply wasted your money since you insisted on using uncorrected numbers.

 

But it's not really. Even the temperature corrections are off. As I said, they are useful as ballpark comparisons, but they are not factual - just random estimates based of N/A cars.

 

ok i have a question, so so a few weeks ago i dynoed like 356whp and 319wtq uncorrected, and when corrected it was like 370whp and 320wtw. so my question is, what exactly this "correction?" i mean there is no average temperature accross the world that it is using, and is it correcting the numbers to what they would be at sea level? what are the corrected numbers representing?


trying not to confuse anyone here.

 

To me, it's the best when low HP cars run low times.

People don't realise there are more important things like gearing, hp/weight ratio, etc. which has already been stated.

I agree with Warr, everybody can talk all they want about how much power their car makes, but i hardly get beat, and i know i don't have 300 hp.

 

The fact of the matter is that dyno #s are only TRULY relevant when comparing #s from the EXACT same dyno (same location, not same brand). There are just way too many factors. Basically every dyno # should come with an "*" to completely explain all of the conditions It's a good general comparison, but too many people argue online based only on these numbers, and it's ridiculous. People completely forget factors of weight, traction, drivetrain, etc., etc., etc......

 

DEF:
Corrected True HP is the:
Actual power under Steady State or Sweep with CORRECT inertial mass value at 20 fps/ps
delivered to the drive roller of a chassis dyno
to which is ONLY added the dyne coast down parasitics and then
corrected to existing atmospheric test conditions

http://www.factorypro.com/dyno/true1.html

 

Most people do not use STD. Where did you get that idea? You said most that you see use STD, but no, most use SAE - that is the standard. Also, many times STD reads _higher_ than both SAE _and_ uncorrected. I know this, because of WinPep.

Yes, if it's 20 degrees cooler on my 2nd trip to the dyno, and my dynograph reads 15whp higher, then I gained power. Is that in question? Uncorrected is all that matters when you're racing, and SAE/STD corrections do _not_ accurately show the difference in power. They are just ESTIMATES, and no, STD is not some randomly special correction for turbos. People use STD for all types of cars just like SAE. If you never race (like you don't) and think that the dyno tells you everything you need to know, then you'll just have to remain oblivious. There have been many, MANY people who dyno'd good numbers but then didn't perform well at all at the track. Yes, GENERALLY, the dyno will show measurable differences with mods and such, but it doesn't always translate into real performance, which is why you have to go verify on a track.

It doesn't matter if I choose to look at uncorrected or corrected, because I can see both with a simple pulldown menu. I can choose any of the corrections, no correction, 0 smoothing or 5 smoothing, etc etc. There is no wasting of my dyno time, because I can manipulate WinPep (or the dyno computer itself while I'm there) to show me whatever figures I want to see. I don't know where you get this operator misuse thing when they have nothing to do with the correction factors. These factors are built in to the software, so what were you referring to?

 

Which part of what I said in the above quote is so hard to understand. Let me break it down for you Warr.

1. I dynoed today in CA with temp @ 90 degrees, at sea level, and 15% humidity. I have TBE with panel filter and I got 300 hp.

2. In January I dynoed again, but I added a set of cams. The temp was 55 degrees, at sea level, and 2% humidity. The car puts down 350 hp.

Both numbers are UNCORRECTED, like you like them and like you quote them. Can you say with a level of confidence that you gained 50 hp from the cams. THE ANSWER IS NO. Why? because you are not accounting for the temperature and humidity variance when you use uncorrected numbers.

Now let us say that you use an SAE/STD/DIN or whatever correction you chose on BOTH dyno runs. The key is to use the SAME correction method on BOTH dyno runs. If you use SAE in one, you use SAE in the other. Let us take SAE. What does that number mean? It means that both your runs are multiplied by a correction factor based on 60 degree temp, sea level and zero humidity. You have now rendered humidity and temp and sea level CONSTANT.

Using the SAE number let us say that your first dyno goes up to 315 hp and your second dyno goes down to 340 hp. NOW you can compare the two runs and figure out what power came from the cams. NOW you can confidently say that the cams produced 25 hp.

Do you understand why people use corrected numbers?

If you use an uncorrected number you CANNOT compare dyno runs on the same dyno at different temps, hg, humidity. With an uncorrected number you can say I produced x power on x day under x conditions. then after you add a modification you can say I produced y power on y day under y conditions. you will NOT know whether the conditions had anything to so with the power change or the mod.

 

NJ, you're acting like I don't know this most basic of concepts. Look above - I never said anything to make it sound like I don't understand this concept. I've been explaining this same thing to people for years. What I'm telling YOU is that neither SAE nor STD provides accurate corrections. You may think that it does, but it doesn't. It tries to estimate how much power you'd make at some mean weather value (no, it's not 60* - more like 75*), and it also doesn't correct for barometric pressure below 1000' (0' and 999' are the same correction), and it's all meant for N/A cars to begin with. I said that these corrections can be used for BALLPARK comparisons, but they are just guesses.

What you put to the ground is what you put to the ground. You can see both the uncorrected AND corrected numbers to appease your need for seeing what your cams gave you, but in the end, the only number that matters is the uncorrected one, because THAT'S how much power you're actually making.

 

In other words, the dyno measures (in uncorrected) what you are ACTUALLY putting to the wheels, in those circumstances. And those circumstances are what you are going to be driving in, therefore it's an accurate representation of the power you're making. When you correct it, it's just trying to standardize it so that numbers can be compared to dynos in different conditions, but at the end of the day, you're not running in those different conditions, so the number that matters is what you put down in your weather, in your altitude, in your car... ie. uncorrected. NOT what the software feels you'd put down if all conditions were "ideal"...

 

The number that SAE or STD or DIN come up with is intended to make comparison EASIER. How accurate in the absolute is not that relevant. The factors just correct to a base number. The base temp number can be 60 degree for SAE or 70 degree for STD. That is all they do. Using corrections allow us to compare better than not using them at all. They can tell us how much hp I made from X mod while Temp, humidity, pressure is held constant. THAT IS ALL THEY DO. They render atmospheric conditions constant. No more no less.

Which one will more accurately tell you how much power you gian from your cam install:

1. an uncorrected number where temps, humidity, pressure and CAMS are variables

OR

2. a corrected number where temps, humidity, pressure are CONSTANT and the only variable are the CAMS.

I am not talking about how mcuh power you put to the ground. That is not the purpose of a dyno for me. The purpose of a dyno is to know how much power the X mod made my car gain over a previous dyno run w/o X mod ALL ELSE BEING EQUAL.

That is why when I went to the dyno I told the dyno operator I want a base with the Xede maps ZEROED. I wanted to know what my car put down BEFORE and AFTER the Xede tune. My car stayed on the dyno for TWO hours during which the conditions changed. If I did not use CORRECTED STD numbers then I cannot get a good before and after comparison.