Which dyno numbers do I go by?

[RRS197]

I spent a while on Google trying to figure out Normal vs. SAE dyno numbers. I think I understand how this works.

Normal is real time, right then and there, current conditions. Right?

SAE is a calculated number for "excellent" conditions. Example: temperature, altitude, humidity, etc.

Well, I got my 2013 GT dynoed this morning in Houston. The car has a 93R Bama tune with a JLT CAI. Conditions were 75 degrees and 83% humidity.

Apparently the tech who ran my car didn't realize the computer was set to normal, and my WHP went in this order during my 3 pulls.

389 WHP, 386 WHP and finally 391 WHP.

But when he set it to SAE it said I have 409 WHP and 390 TQ. He said all shops go by SAE. Is that true? I asked him, so when people ask me how much HP my car has, do I say 391 or 409? He said 409.

Right after me a 2015 GT with a Bama 93R and airaid CAI dynoed in twice. First was a 408 and the second was 411 HP via SAE. So I'm not sure how we were so similar.

What numbers should I go by?

 

[07TGGT]

Wtf is this shit.

 

[RRS197]

Thanks for the help.

 

[Grabber Blue 5.0]

Nope, no tekk here folks.

 

[fdjizm]

The one the time slips tells you.

 

[ford20]

1) not fucking tech. You have a problem that you need help diagnosing, or you need help while turning a wrench that goes in tech. This shit is chit chat. Please learn and understand the rules on this board. When in doubt chit chat.

2) SAE because

3) how don't you understand why you are so similar?

 

[mpm_1]

open season...

 

[RRS197]

How is a dyno and computer not tech?

Also, I was unaware you get a timeslip running a dyno. LOL

 

[fdjizm]

How is a dyno and computer not tech?

Also, I was unaware you get a timeslip running a dyno. LOL

You don't that's why it doesn't matter

 

[ford20]

How is a dyno and computer not tech?

Also, I was unaware you get a timeslip running a dyno. LOL

Because this isn't some fluff bullshit forum that has their tech topics outnumbered by the monotony of routine questions constantly being asked such as what CAI is better, do these wheels looks super fly, how do I change the color of the interior lights, how much power am I making? The tech area is reserved for people who are actually doing work, not the keyboard mechanics wondering what the hell they should get to make their car the same as everyone else at the car show.

It's S197, we have higher standards here than most places when it comes to tech.

 

[Johnf78]

You don't that's why it doesn't matter

Bwuhahahaha! QFT!

 

[RRS197]

I'm not at all surprised by the unwelcomed comments. It's a shame, though. All I did was ask a question. And just because some of you have 5000+ posts, doesn't mean you are correct or give you a right to be an asshole. I thought we were all on here to learn. Maybe not.

I was under the impression SAE power results were what counted, not standard dyno results with conflicting weather in all parts of the world. All I wanted to know was how there was a 18 HP gap in between the two and which one really counts as a solid number.

 

[RRS197]

Because this isn't some fluff bullshit forum that has their tech topics outnumbered by the monotony of routine questions constantly being asked such as what CAI is better, do these wheels looks super fly, how do I change the color of the interior lights, how much power am I making? The tech area is reserved for people who are actually doing work, not the keyboard mechanics wondering what the hell they should get to make their car the same as everyone else at the car show.

It's S197, we have higher standards here than most places when it comes to tech.

Then please, answer my question instead of avoiding it. Or do you actually not even know?

And for the record, I did a search before I even posted this and came up with nothing. That's why I made a thread.

 

[weather man]

Then please, answer my question instead of avoiding it. Or do you actually not even know?

And for the record, I did a search before I even posted this and came up with nothing. That's why I made a thread.

It is a meaningless question. Dyno HP means you are hopefully well tuned and gives an indication of where you might run assuming you do your part.

 

[Grabber Blue 5.0]

If you want to race dyno numbers allfordmustangs.com is always looking for new recruits.

 

[ford20]

I did answer your original question and the one previous to that ... SAE ... Your tuner told you why and if you can't believe him then maybe you should go to a different tuner? I'm not trying to be a dick but the answer is there if you know how a dyno operates and why it can be wildly inconsistent and why you try and use SAE to limit the variables so that a dyno number is as consistent as possible from dyno to dyno and from day to day.

Look at the which oil question for a typical S197 response to a stupid question.

Edit: you answered your own question . That is why we use SAE results, for uniformity.

1) not fucking tech. You have a problem that you need help diagnosing, or you need help while turning a wrench that goes in tech. This shit is chit chat. Please learn and understand the rules on this board. When in doubt chit chat.

2) SAE because

3) how don't you understand why you are so similar?

If you want to race dyno numbers allfordmustangs.com is always looking for new recruits.

That's the thing though, what do you tell a road racer or someone who auto crosses their car when they are trying to figure out how much power they make?

 

[NickD87]

You explained what SAE is in your post and others have said sae is used. For more information on it and how lookup dyno correction factor.
Whats more important that you didnt ask or state is crank horsepower which is what is listed when new cars are sold.
Take your sae corrected number and multiply by 15, 20 or whatever percentage you feel like using and that will give you engine HP. That way you can say your car makes 500hp and compare it to a lambo

 

[weather man]

If you really need the down and dirty.

Credit to zeeohsix on z06vette.com


SAE CF = 1.18[Ps/(Pm-Pv)][sqrt(Tm/Ts)]-0.18
(sqrt = square root)

This formula is right out of SAE Paper #J1349 (revision June 1990), and is the latest form of the air correction formula. SAE assumes 15% frictional loss within the engine, which is probably close for a piston engine. NOTE: this is NOT the losses from the crankshaft to the rear wheels, that is a different loss.

Ps = standard pressure
Pm = measured pressure (barometric pressure)
Pv = vapor pressure of water (relates to RH%)
Ts = standard temperature
Tm = measured temperature

The SAE baseline values are:
------------------------------------
Ps = 29.235 inHg
Ts = 77.0 deg F (534 deg R)
Pv = 0 inHg (dry air, no humidity)

Pv will not be 0 inHg during a dyno run, but will equate to the vapor pressure of water vapor in the air, which is a function of humidity.

P units = inHg
T units = deg R (deg F + 460). If not in deg R, you will get a wrong answer!

So, the CF will depend on where the actual air temperature, pressure and humidity is with respect the standard values listed above.

The CF can be less than, or more than 1.00. If you tested your Z06 on a dyno on a day when T = 77 deg F, P = 29.325 and the RH = 0% in the shop where the dyno was, then the CF would be exactly 1.00. As you can see, there are MANY combinations of T, P and RH that will give you the same CF.

Note, the Pv (vapor pressure of water) defines the RH% and is subtracted from the atmospheric pressure because the water vapor "displaces" that much pressure, and essentially makes it equivalent dry air (RH = 0%) at the resulting pressure of Pm - Pv.

BTW, the pressure values in the formula has more effect on HP than the temperature values (square root of a ratio).

Quote:
Originally posted by WA 2 FST
That's an excellent write-up!!

However, what are the STD (Standard) correction #s, if you know them? I believe it is 59^F, 29.92^ baro press., 0% hum.

Thanks! ... been researching this a lot in the past, and I believe the STD values are as you say. They are probably referred to as STD (standard) because the temp and pressure are for standard sea-level air conditions.

59 deg F (STD sea-level air temperature)
29.92 inHg barometric pressure (STD sea-level pressure)

I guess in 1990, SAE dropped the STD values and went with the ones I listed in my first post. Don't know the reason why.

If you plug in the STD temp and baro pressure values into the SAE formula as the measured values (like if a car was dyoed at those Atm conditions), then the CF comes out as:

SAE CF = 1.18[Ps/(Pm-Pv)][sqrt(Tm/Ts)]-0.18

CF = 1.18[29.235/(29.92-0)][sqrt(519/534)]-0.18

CF = 1.18[0.9771][0.9859] - 0.18

CF = 0.9567

Note that:
59 deg F = 519 deg R (deg F + 460 = deg R)
77 deg F = 534 deg R
Pv = 0 inHg = 0% humidity

So, this means that if a car was dynoed at STD conditions (59 F, 29.92 inHg, 0% RH) it would be making 1.0000 - 0.9567 = 4.33% more HP than if it was dynoed at the current SAE baseline Atm values of 77 deg F, 29.235 inHg and 0% RH (which would give a CF of 1.000).

4.33% more RWHP would equate to about 15 RWHP on a [ame][URL="http://www.amazon.com/dp...r the current SAE values. __________________

 

[RRS197]

If you want to race dyno numbers allfordmustangs.com is always looking for new recruits.

You've gotta be a kid. Because no grown man would act so immature.

I did answer your original question and the one previous to that ... SAE ... Your tuner told you why and if you can't believe him then maybe you should go to a different tuner? I'm not trying to be a dick but the answer is there if you know how a dyno operates and why it can be wildly inconsistent and why you try and use SAE to limit the variables so that a dyno number is as consistent as possible from dyno to dyno and from day to day.



I'll accept that answer. Thank you.

I did answer your original question and the one previous to that ... SAE ... Your tuner told you why and if you can't believe him then maybe you should go to a different tuner? I'm not trying to be a dick but the answer is there if you know how a dyno operates and why it can be wildly inconsistent and why you try and use SAE to limit the variables so that a dyno number is as consistent as possible from dyno to dyno and from day to day.

Look at the which oil question for a typical S197 response to a stupid question.

Edit: you answered your own question . That is why we use SAE results, for uniformity.





That's the thing though, what do you tell a road racer or someone who auto crosses their car when they are trying to figure out how much power they make?

I guess the reason I'm asking is because 409 seemed like a high number and I wasn't expecting that. And a 2015 right behind me made the same. I'm really pleased with the results. I guess I just needed some feedback and convincing these numbers were legit. Thanks.

 

[Wes06]

learn to multi quote.

still not tech, learn the difference.

hp numbers can be tweaked to be whatever the dyno operator wants