ERGO EVO

Ok guys. I found a great thread explaining different dyno correction factors. Here's the meat of it below, but if you want to go there, then visit:

http://www.tampabaysvtoa.com/forums/...read.php?t=947

Note that there's a huge temp correction difference between SAE and STD...17 degrees F! That basically means that STD/STP will always read 4% HIGHER than SAE. Something worth thinking about.

· SAE -- The SAE standard applied is a modified version of the SAE J1349 standard of June 1990. Power is corrected to reference conditions of 29.23 InHg (99 kPa) of dry air and 77 F (25°C). This SAE standard requires a correction for friction torque. Friction torque can be determined by measurements on special motoring dynamometers (which is only practical in research environments) or can be estimated. When estimates must be used, the SAE standard uses a default Mechanical Efficiency (ME) value of 85%. This is approximately correct at peak torque but not at other engine operating speeds. Some dynamometer systems use the SAE correction factor for atmospheric conditions but do not take mechanical efficiency into consideration at all (i.e. they assume a ME of 100%).

· STP -- The STP (also called STD) standard is another power correction standard determined by the SAE. This standard has been stable for a long time and is widely used in the performance industry. Power is corrected to reference conditions of 29.92 InHg (103.3 kPa) of dry air and 60 F (15.5°C). Because the reference conditions include higher pressure and cooler air than the SAE standard, these corrected power numbers will always be about 4 % higher than the SAE power numbers.

· ECE -- The ECE standard is based on the European Directives. Power is corrected to reference conditions of 99 kPa (29.23 InHg) of dry air and 25°C (77 F). Friction torque is not taken into consideration at all.
·
DIN -- The DIN standard is determined by the German automotive industry. Power is corrected to reference conditions of 101.3 kPa (29.33 InHg) of dry air and 20°C (68 F). With the advent of European legislation and standards, national standards such as the DIN (formerly widely used) are now less significant.

NOTE There is a tendency for all those standards to converge. The only worldwide power correction standards at this time are the ones determined by ISO. For internal combustion engines in road vehicles, this is the ISO 1585 standard. The current SAE J 1349 and ECE standards are nearly identical to the ISO 1585 standard.http://www.tampabaysvtoa.com/forums/showthread.php?t=947]
http://www.tampabaysvtoa.com/forums/showthread.php?t=947[/URL]

David Buschur

iTrader: (53)

Once before on here many people decided they wanted the dyno sheets that were going to be posted to all be SAE before they were posted. At that time I didn't know what we had our dyno set at. After looking I found that that is how it was. It is easy to change on a Dynojet, you just click the one you want to use.

On a Dynojet the highest HP readings will be shown if the "Uncorrected" value is chosen. This displays actual HP that the car made to the wheels in the conditions of that day. I imagine that if you were dyno'ing in a 105 degree day and compared "Uncorrected" to SAE that the SAE would then be higher. This long dyno work I have been doing lately I changed back and forth between SAE and Uncorrected once in awhile just to see what the differences are. Up until last week we had no heat in our dyno room, well not a direct heat, it was heated from the parts room/fabricating room next to it. This meant many days it was cold as hell when I was running the dyno. Now the room is heated as I finally put a furnace in the back of the building and there is a duct just for the dyno room. Anyway, with the air being very cold in the room the Uncorrected power has always been higher than when I run the SAE corrected HP.

Now that the room is higher in temperature the difference in the two factors is very close.

Just some input.

David Buschur
www.buschurracing.com

ERGO EVO

David,

Actually, if you're talking STD correction, typically the CORRECTED numbers would be higher. For example: if you're dynoing even on a moderate day where the ambient temp is 70F, STD will correct down to a full 10F lower (60F). You can take a quick peek at the thread for the 2005 bone stock evo dyno numbers on SoCalEvo, and what you'll notice is that Tuning Technologies used STD correction with a resultant CF of 1.03, significantly higher than the actual, and that day the temp was 69F. Hope that helps.

EDIT: Just noticed that your dyno is in Ohio. I actually went to college there. =) That being said, most months OF COURSE your uncorrected numbers would be higher. Cold air=power, especially on turbo cars. Out here in CA though, we'd often be hard-pressed to dyno in a room whose temp would be less than 60F. I find myself wishing more people/shops would show all relevant atmospheric conditions on their dyno charts.

David Buschur

iTrader: (53)

I never use STD. I use SAE and once in awhile look at the uncorrected numbers just to see what weather conditions are effecting the numbers.

DAvid Buschur
www.buschurracing.com

ERGO EVO

Fair enough, but you also stated:

That's simply not true, as I have pointed out. The highest readings are dependent upon which type of correction you employ and the conditions you run under. Plenty of humidity and low pressure will BOOST both your SAE and STD correction numbers.

If you haven't already seen the thread I posted with Dave Coleman's "How to Lie With a Dyno", it's worth reading.

David Buschur

iTrader: (53)

Deleted.

I responded to this and it was so nasty I just deleted it.

Not interested in responding here anymore.

David Buschur
www.buschurracing.com

ERGO EVO

Ok, now I'm confused. Why the need to be nasty??? I wasn't suggesting you were lying by referring you to the article. It was just a good read, really. Not sure where the combativeness is coming from...

David Buschur

iTrader: (53)

I guess since I took the time to come here and post what I actually see with the dyno and not what was written in some book by whoever Dave Coleman was and then you referring the book to me it just pissed me off.

I am also very tired of the entire talk of dyno's that this and every other board produces, it gets very irratating.

David Buschur
www.buschurracing.com

ERGO EVO

David,

Dave Coleman is the former tech editor of Sport Compact Car. I'd say he's spent more time around a dyno than most. I wasn't referring you to a book, just one of his columns.

Sorry that irritated you.

And for the record, I have the same WinPEP program used to manage runs on a Dynojet and have played around with correction on many actual dyno pulls. What you see in Ohio in most months makes sense. Uncorrected numbers would be higher since any correction standard would dump you down given your low ambient temps.

David Buschur

iTrader: (53)

Dave Coleman, I knew I knew that name, and I remember reading that article now that you mention it.

You don't owe me an apology.

David Buschur
www.buschurracing.com