SAE correction vs DIN correction?
12-21-2009, 10:01 AM
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SAE correction vs DIN correction?
I thought the correction factors correct to a given standard based on temp and pressure, and that the variance is just in what the standard is. Shouldn't this mean power changes from mods are the same (or at least the same in terms of percentage)? I'm trying to understand why work I did to my car yielded ~0.5hp with SAE standard but ~4.3hp using DIN. Either way, I'm calling it no gain, but I'm curious why the correct powers show different percentages of hp increase.
Last edited by marlinspike; 12-21-2009 at 10:11 AM.
12-21-2009, 05:06 PM
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Re: SAE correction vs DIN correction?
But shouldn't the gains be similar? I'm not saying there was a 4hp difference between DIN and SAE, but that there was a 4hp difference in the gains, or put another way 800% different.
Last edited by marlinspike; 12-21-2009 at 05:23 PM.
12-21-2009, 05:58 PM
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Re: SAE correction vs DIN correction?
Oh, I see what you're saying now. Yes, if you're comparing before and after, the gains should be the same unless there is something wrong with the parameters used for the corrections. The formulas for the corrections are different, but you can convert from one to the other because they're just two different calculation formulas based on the same raw data. So the DIN-corrected before/after will be larger, but their difference should be almost identical to the SAE-corrected before/after difference.
I can't really think of what would cause a calculated difference that big, but I'm sure there's a reason somewhere. I'd just stick to SAE, it's the most widely used in this country.
I can't really think of what would cause a calculated difference that big, but I'm sure there's a reason somewhere. I'd just stick to SAE, it's the most widely used in this country.
Last edited by Fabrik8; 12-21-2009 at 06:00 PM.
12-21-2009, 06:12 PM
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Re: SAE correction vs DIN correction?
Oh, I see what you're saying now. Yes, if you're comparing before and after, the gains should be the same unless there is something wrong with the parameters used for the corrections. The formulas for the corrections are different, but you can convert from one to the other because they're just two different calculation formulas based on the same raw data. So the DIN-corrected before/after will be larger, but their difference should be almost identical to the SAE-corrected before/after difference.
I can't really think of what would cause a calculated difference that big, but I'm sure there's a reason somewhere. I'd just stick to SAE, it's the most widely used in this country.
I can't really think of what would cause a calculated difference that big, but I'm sure there's a reason somewhere. I'd just stick to SAE, it's the most widely used in this country.
My only thought is the SAE Aug2004 accounting for frictional losses somehow impacts this? Or maybe I compared new corrected numbers to old uncorrected numbers when looking at SAE...I'm going to have to check next time I'm there.
Last edited by marlinspike; 12-21-2009 at 06:20 PM.
12-21-2009, 06:19 PM
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Re: SAE correction vs DIN correction?
Yeah, I bet you do. That's actually caused a lot of controversy in the past; different countries use different correction standards and so their cars have different rated HP unless they rate according to the standard of the country they're in. It's not a case of "when is a HP not a HP", it's a case of making sure that you're comparing apples to apples.
It doesn't really matter though, you're more likely to get much bigger HP differences from going to a different dyno than you are by just using different correction factors at the same dyno. You're doing the right thing by only caring about before/after and by using the same dyno.
It doesn't really matter though, you're more likely to get much bigger HP differences from going to a different dyno than you are by just using different correction factors at the same dyno. You're doing the right thing by only caring about before/after and by using the same dyno.
12-21-2009, 06:20 PM
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Re: SAE correction vs DIN correction?
Yeah, I bet you do. That's actually caused a lot of controversy in the past; different countries use different correction standards and so their cars have different rated HP unless they rate according to the standard of the country they're in. It's not a case of "when is a HP not a HP", it's a case of making sure that you're comparing apples to apples.
It doesn't really matter though, you're more likely to get much bigger HP differences from going to a different dyno than you are by just using different correction factors at the same dyno.
It doesn't really matter though, you're more likely to get much bigger HP differences from going to a different dyno than you are by just using different correction factors at the same dyno.
What I REALLY like are the uncorrected numbers. 281lb-ft makes the tires go OM NOM NOM NOM on the pavement. I love cold air.
Last edited by marlinspike; 12-21-2009 at 06:24 PM.
12-21-2009, 06:31 PM
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Re: SAE correction vs DIN correction?
Negative 13 degF the other week made good power even here at almost a mile high.
But the question still remains: Why are your before/after corrections that much different? I can't remember enough about the two corrections to figure out what else might be involved, like one correction might include humidity or intake air temp (air going into the intake, not air going into the engine) that the other correction might not include. That would only matter day to day obviously, if it actually comes down to something like that. If it's the same day, and the ambient conditions don't really change at all, then I'm completely dumbstruck to try and explain it.
But the question still remains: Why are your before/after corrections that much different? I can't remember enough about the two corrections to figure out what else might be involved, like one correction might include humidity or intake air temp (air going into the intake, not air going into the engine) that the other correction might not include. That would only matter day to day obviously, if it actually comes down to something like that. If it's the same day, and the ambient conditions don't really change at all, then I'm completely dumbstruck to try and explain it.
Last edited by Fabrik8; 12-21-2009 at 06:34 PM.
12-21-2009, 07:00 PM
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Re: SAE correction vs DIN correction?
Negative 13 degF the other week made good power even here at almost a mile high.
But the question still remains: Why are your before/after corrections that much different? I can't remember enough about the two corrections to figure out what else might be involved, like one correction might include humidity or intake air temp (air going into the intake, not air going into the engine) that the other correction might not include. That would only matter day to day obviously, if it actually comes down to something like that. If it's the same day, and the ambient conditions don't really change at all, then I'm completely dumbstruck to try and explain it.
But the question still remains: Why are your before/after corrections that much different? I can't remember enough about the two corrections to figure out what else might be involved, like one correction might include humidity or intake air temp (air going into the intake, not air going into the engine) that the other correction might not include. That would only matter day to day obviously, if it actually comes down to something like that. If it's the same day, and the ambient conditions don't really change at all, then I'm completely dumbstruck to try and explain it.
Last edited by marlinspike; 12-21-2009 at 07:12 PM.
12-21-2009, 07:23 PM
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Re: SAE correction vs DIN correction?
That's the kind of stuff I'm talking about. Without knowing what both correction equations are, it's hard to get to the bottom of it. DIN and SAE might have different drivetrain corrections, etc. Both are actually supposed to be HP at the crank if I remember, so it's very possible that the corrections for loss are different.