[oldman]

CF useful on NA cars under limited conditions, since they are so abused, I would rather not use them. Near worthless on FI cars BTW.

What is wrong with tuning the car for the current conditions? As really even with a small CF applied it really does not help with tuning. I must be missing something here...

Here is the most common example a base supercharger Procharger (I most familiar with) should get you 600 HP. Lets say SAE conditions outside, drivetrain loss with a M6 is really about 10% so I'd expect 540 RWHP as measured and since the conditions are SAE standard the CF=1.0. I drive the exact same car to Denver on a 105 degree summer day. The SAE CF is probably 15%, but wait the Denver shop likes to race dynos as it brings in customers, they use STD which is 19% and they use a rule of thumb of 15% drivetrain loss (even though it ain't). Then they quote and sell their much higher HP kit on the exact same car.

For ballpark let's say 7 PSI is 150 HP or 22 HP per PSI, say Colorado is down 1.2 PSI or 26 HP, temp well it has a big intercooler so temp might only be 10 degrees over what it was at SAE J1439 at 77 degrees, 10 degrees F based on the gas law of negative 460 degrees back of envelope that is about 6 HP less. So the actual engine in the car in Denver is making about 600 HP - 26 HP for pressure drop, -6 HP for temp = 568 HP. Lets just say 5% for grins and we get 570 engine HP, dyno is about 10% loss or 513 RWHP as measured no magic.

But the shop wants to corrected for the reasons you stated (actually to sell parts). 513 RWHP as measure corrected to STD = 610 RWHP, but WAIIIIIT a minute the shop is selling engine HP (higher number) so they crank in their rule of thumb (I've seen anything from 15% to 18% to 20%) 610 RWHP x 20% loss = 730 engine HP.... FOR THE EXACT SAME KIT.

SAE correction factor was meant for engines on a dyno NA to be compared under very limited conditions. There is no FI correction factor as an FI engine is less sensitive to altitude and temp. One can argue that these DI engines are octane limited not boost limited hench they can put out the SAME to the wheels in Denver vs LA, so why would one "correct it"?

Same thing happens in magazine dyno test, mostly these are hub dynos with a drivetrain loss of say 5 to 8 % They are using STD correction factors and then some ridiculous drivetrain loss factor to conclude the engine is make xyz HP over stock.. We both know that an SAE certified engine makes within a very small percentage the HP advertised. So who is correct the magazine, with their STD Unicorn HP and fictional drivetrain loss or the SAE certified number?

As stated the potential for cheating or whatever you call it is rampant, can't cheat on as measure HP on a dynojet. But you say my shop is in Denver during the summer and this is a NA car. Well does the customer live in Denver are you tuning in Dever, then why do you care what the corrected HP is? You are tuning the car for Denver and it makes what it makes.

Here says the max CF is 7%. So sorry for Colorado it can't be used. https://www.dynomitedynamometer.com/...horsepower.htm

You can do a search on this forum, I've published dynojet's statement on correction factors use on boost engines, nutshell it can't be done. I also posted dynojet's statement on why STP, STD CF were removed as they are HP readings true enough, but a Unicorn is a horse.


I just checked and Denver is like 2.3 PSI down and 23% correction factor. Note that SAE can't be used above 7% and STD / STP would be 3% LOL...

So why do dyno racers not put the CF applied? If you can answer that you will understand the nature of dyno racing. It a correction factor really being used to compare an engine and parts to some standard or is it used to produce fictional HP gains? As I always say ask for the uncorrected HP number is you want to know how much HP the car is actually making.