McRat said:
Yes, and comparing ET's has exactly the same problem. We always get a kick when out-of-state guys visit us, run a pass, scratch their heads. "Uh, my truck must be busted!!! It runs a second quicker at home!!!" During the Diesel Power Magazine West Shootout, all the "11 second" Dodges from up North were running 13's and 14's. OPPSS!!
Nope. Certain folk like to convince you that air density has no effect on turbo diesels at all. These are guys who do not race their trucks much. As soon as they start traveling to different states and running, they find out that while DA does not hit us as hard in diesels, it still hits us pretty good. Casper lost 3 mph last night because of the thin air. The Corvette it towed lost 6-8mph.
So all the low-landers will scream UNCORRECTED OR IT'S LIES!!! This is just because they live in a very small world with very dense air.
Will you be happier if I do a dynojet? You won't mind if I wait until I find a sea level dynojet and cold weather right? I figure I might make 680. Negative DA is your friend. We've picked up 18rwhp on the Vette using "uncorrected" numbers in > 30.00" 20% 50 deg weather. I would never think of posting the "uncorrected" values though, because I know better.
I did not say one was better than the other, more accurate than the other, or closer to what the ET/HP calculation would be. I simply said that the Superflow in Cali typically gives a higher number than the uncorrected DynoJet numbers. This is clear by the 16% difference in numbers from the SF to the DJ several guys have experienced from one to the other.
Since the DJ is the overwhelming choice in the country for dyno brand and it would be encountered more likely than others, I thought the information was relevant.
During the intense dyno work we have done over the years since 1999 we have found that some of the CF is valid and even posted to this in the past. Even on TurboDiesels. Depending on the CF used. Be it: SAE J-1349, DIN, EEC, or JIS all used by DynoJet or the STP factor you are using on the superflow. The STP by the way is still a SAE correction factor, but it is more generous as I will show.
The DynoJet used SAE J-1349 corrects HP output to 77 degrees and a baro of 29.92.
The commonly referred to STP ( Standard, Temp and Air ) used often on the Superflow corrects HP to 60 degrees and a baro of 29.23. So any temp over 60 degrees compared to the 77 for SAE J-1349 get something added to that. Not withstanding the baro readings. 5% is roughly the average difference between the two factors on most engines.
Using the 5% and a few numbers shows how potentially different the two numbers can be:
Lets take 500 HP, 600 HP and 700 HP for comparison using the average gain of 5% over the DJ SAE J-1349.
A 500 HP run on SAE DynoJet would be 525 on a STP dyno.
A 600 HP " " 630 on a STP dyno
A 700 HP" " 735 on a STP dyno
Clearly you get an advantage as the temps go up to 80 degrees on the STP dyno. A full 20 degrees over the STP "standard" air temp they compare for VS 3 degrees of factor for the SAE J-1349 Dynojet
From there the politics can take over and I dont care personally what people want to use for a Dyno, a CF or a ET/HP comparison. But for averages and the shear poliferation of the DynoJet, I thought it to be the better standard to delete the CF, run uncorrected numbers on the DynoJet and consider my HP data conservative compared to some of the others.
