Dyno Results - SAE or STD?

[final5-0]

Been doing some research lately to find some answers that I've been
wondering about for some time now

What prompted me to search out the info is I see more and more
dyno results these days rated in STD as opposed to SAE when the
bench mark of 300 rwhp for an OEM blocked NA combo was kinda
put in place by the various Stang communities you find on the net.

In my research of STD charts ......
I've seen correction values from 1.03 to 1.08

While I've found no article or info that explains the differences to my
satisfaction ... I have seen info in several hits from Google that
eludes to this line of reasoning.

Say you got a pull rated in STD with a correction value of 1.03

The articles say the values have been multiplied by 1.03

If you wanted to see SAE values you would multiply by .97

I wanted to share with everybody what I've been able to find

Anybody that can share info to help confirm this is correct
or
Not Correct

Please ... Lets figure out this stuff ... once and for all

Grady

 

[94v6GT]

huh

 

[5spd GT]

So Grady are you saying the STD is showing higher than the older SAE dyno

 

[final5-0]

So Grady are you saying the STD is showing higher than the older SAE dyno

Yes David

I've seen it said on here and the Corral STD usually shows higher
values than SAE

I'm hoping to find hard data ... or ... valid data
rather than a hear say kinda thing

Grady

 

[5spd GT]

Just to keep the topic going, I found a user over on ls1tech that talked about an article in a f-body magazine which seems to coincide with your findings

"This is from a magazine article on "dynojet" dynos.

SAE j1349 correction:
29.23 in/hg.
77 degree temp
0 percent humidity

Standard correction:
29.92 in/hg.
68 degree temp
0 percent humidity

What this all means is that "Standard" will give you 2.6 percent better numbers (very popular for the import crowd). The example the magazine gave was a Vette making 412 (SAE corrected hp). With the Standard correction it made 423. All that you will have to do is multiply your "Standard rwhp" by .974 This should equal SAE (the one everyone uses). Up here in the great white North (Washington) the temps are in the 40-50 degree area, along with 29.9-30 in/hg. So, our numbers are actually corrected down from what it made at the rear. Usually, 96-97 percent of actual posted numbers. If you dyno when it's a hotter temp or higher altitudes the numbers will usually correct up to equal the desired temp, humidity and pressure of the correction factor. "

 

[Adam95GT]

I thought my car had an std once... Its a little ...

 

[Dino Dino Bambino]

Just to keep the topic going, I found a user over on ls1tech that talked about an article in a f-body magazine which seems to coincide with your findings

"This is from a magazine article on "dynojet" dynos.

SAE j1349 correction:
29.23 in/hg.
77 degree temp
0 percent humidity

Standard correction:
29.92 in/hg.
68 degree temp
0 percent humidity

What this all means is that "Standard" will give you 2.6 percent better numbers (very popular for the import crowd). The example the magazine gave was a Vette making 412 (SAE corrected hp). With the Standard correction it made 423. All that you will have to do is multiply your "Standard rwhp" by .974 This should equal SAE (the one everyone uses). Up here in the great white North (Washington) the temps are in the 40-50 degree area, along with 29.9-30 in/hg. So, our numbers are actually corrected down from what it made at the rear. Usually, 96-97 percent of actual posted numbers. If you dyno when it's a hotter temp or higher altitudes the numbers will usually correct up to equal the desired temp, humidity and pressure of the correction factor. "

You're close but not quite there. The old standard correction that's still popular with hotrodders was actually to 60*F so the HP/TQ numbers came out 4.0% higher than with the SAEJ1349 correction. The correction that you quoted to 68*F is the DIN correction that's used in Europe, which produces HP/TQ numbers that are 3.2% higher than SAEJ1349.
The bottom line is all dynos are not equal and when you take your vehicle to the dyno, ask the operator which correction factor was used. It can make quite a difference, and an unscrupulous dyno operator could potentially "doctor" the HP/TQ numbers higher to satisfy a customer by entering "pessimistic" atmospheric conditions (or a higher elevation than reality) to increase the degree of correction. This is the one situation where the dyno really can lie.

 

[94-302-vert]

I thought my car had an std once... Its a little ...

I hope you got that taken care of before it got passed around...

 

[Don 95Vert]

The 'standard' that most numbers are derived from are SAE numbers - that's what we use. They are lower, but tend to be a more accurate reflection of the real world numbers corrected for atmospheric conditions. Some dyno operators like to use STD because the numbers are higher. You can also get slightly higher numbers by maxing out 'smoothing'.
Don

 

[final5-0]

The 'standard' that most numbers are derived from are SAE numbers - that's what we use. They are lower, but tend to be a more accurate reflection of the real world numbers corrected for atmospheric conditions. Some dyno operators like to use STD because the numbers are higher. You can also get slightly higher numbers by maxing out 'smoothing'.
Don

Hello Don

I was hoping you would see this thread

Of course ... The big Q is ..........
How inflated are the STD values over SAE values

If you see a dyno chart with the STD values, is there a way or formula
to convert over to SAE?

When you say maxing out smoothing

I've seen a lot of charts say ... Smoothing 5
Is there a rating of something like 1 to 10
or
How does the value of 5 rate as far as minimum and maximum is concerned?

Thanks Don
Grady

 

[5spd GT]

You're close but not quite there. The old standard correction that's still popular with hotrodders was actually to 60*F so the HP/TQ numbers came out 4.0% higher than with the SAEJ1349 correction. The correction that you quoted to 68*F is the DIN correction that's used in Europe, which produces HP/TQ numbers that are 3.2% higher than SAEJ1349.
The bottom line is all dynos are not equal and when you take your vehicle to the dyno, ask the operator which correction factor was used. It can make quite a difference, and an unscrupulous dyno operator could potentially "doctor" the HP/TQ numbers higher to satisfy a customer by entering "pessimistic" atmospheric conditions (or a higher elevation than reality) to increase the degree of correction. This is the one situation where the dyno really can lie.

That was a copy and paste, not my own words. Thanks for the correction either way

 

[Don 95Vert]

Rob, who runs the shop and set up the dyno would know better, but I don't think there is a 1:1 ratio between std and sae. I think it's all weather dependent. This summer when it was hot out, really hot, he was telling me the correction was like 60 RWHP on some cars. Each Dynojet has its own weather station.

Smoothing takes all the 'jiggles' out of the graph - depends on the software, but usually smoothing goes to 5 on a Dynojet. Setting it up to 5 from say 2 or 3 will gain power. Magically. What it does is interpolates the curve and sometimes that gets better numbers.

FYI: underinflating tires on a dyno will result in lower numbers. Pump them up to road levels - 32-38 psi. I've seen cars 'gain' 30-50 RWHP by pumping the tires. So be wary if you have low tire pressure and the tuner pumps the tires on the last pull and you gain a ton of power.

On FWD cars something like holding the steering wheel off center so the tires are at an angle can show much lower numbers too. On those, since they tend to steer themselves off center, you have to hold the wheel dead straight to get good numbers. Some opertors know this and on initial pulls, hold the wheel a bit off, then straighten it for the last pull.

We always re-dyno cars if they have been tuned elsewhere, with the original tune in them first, then retune them. 9 times out of 10, they have some inflated numbers that we show to be bogus with the first pull. You'd be surprised if I told you the original tuners involved.

It's amazing what you see being done, but a little info goes a long way to protecting yourself!

Don

 

[final5-0]

Thanks Don

You have always been so kind
to share with us info based on your experience

For your efforts I wanna say ... It is most appreciated

I know the entire forum feels the same as well :Word:

I don't know if anybody feels the same about this SAE/STD issue
as I do ... or ... even sees a reason to bring it up

But as for me ..............

Its all about a reference point

You can't just take any old Dynojet dyno chart and lump em all together

Several years ago ...
Stang owners started to use 300 SAE rwhp as a bench mark for ...
A fairly stout OEM block based NA Street combo

I see the recently more used inflated STD rating as a way to
fudge on that benchmark

Kinda like making a pull with no serp belt
but
Forgetting to tell about that little detail

It just ain't an apples to apples comparison

At least ... as I see it

Grady

 

[Don 95Vert]

Thanks Grady.

Here's a god one. We were training an SCT dealer in another state a few years back. The dyno owner told me he had a guy there one time with a Mustang trying to tune it himself. After a while, this guy was getting desperate for better numbers. A little while later he notices the guy had taken his spare tire out and was in the provcess of removing the passenger's seat. He asked what he was doing. The guy said he was lightening the car so he could make better numbers. Apparently he never made the correction that less weight helps at the track, but does nothing on the dyno....

Don

 

[final5-0]

Thanks Grady.

Here's a god one. We were training an SCT dealer in another state a few years back. The dyno owner told me he had a guy there one time with a Mustang trying to tune it himself. After a while, this guy was getting desperate for better numbers. A little while later he notices the guy had taken his spare tire out and was in the provcess of removing the passenger's seat. He asked what he was doing. The guy said he was lightening the car so he could make better numbers. Apparently he never made the correction that less weight helps at the track, but does nothing on the dyno....

Don

Hey ... This is one of those ... Classic Stories

One of the mods ought to put this in a sticky of funny posts
or
Some how or the other save it for all time :Word:

Don ... I bet you got a bunch more like this one

Grady

 

[badstang123]

Rob, who runs the shop and set up the dyno would know better, but I don't think there is a 1:1 ratio between std and sae. I think it's all weather dependent. This summer when it was hot out, really hot, he was telling me the correction was like 60 RWHP on some cars. Each Dynojet has its own weather station.

Smoothing takes all the 'jiggles' out of the graph - depends on the software, but usually smoothing goes to 5 on a Dynojet. Setting it up to 5 from say 2 or 3 will gain power. Magically. What it does is interpolates the curve and sometimes that gets better numbers.

FYI: underinflating tires on a dyno will result in lower numbers. Pump them up to road levels - 32-38 psi. I've seen cars 'gain' 30-50 RWHP by pumping the tires. So be wary if you have low tire pressure and the tuner pumps the tires on the last pull and you gain a ton of power.

On FWD cars something like holding the steering wheel off center so the tires are at an angle can show much lower numbers too. On those, since they tend to steer themselves off center, you have to hold the wheel dead straight to get good numbers. Some opertors know this and on initial pulls, hold the wheel a bit off, then straighten it for the last pull.

We always re-dyno cars if they have been tuned elsewhere, with the original tune in them first, then retune them. 9 times out of 10, they have some inflated numbers that we show to be bogus with the first pull. You'd be surprised if I told you the original tuners involved.

It's amazing what you see being done, but a little info goes a long way to protecting yourself!

Don

These are some great things to know for any one of us who has to rely on someone to tune our cars It's seems like there are more and more people scamming and twisting the truth these days (Regardless of which industry). A little knowledge can go a long way in protecting yourself. Thank you very much for the information.
- Justin