Burkey
Well-Known Member
“I believe there is a reason these dyno numbers are all over the map. The correction factors account for air density changes but they can not account for things the PCM calibration changes at different conditions or the way the engine reacts to those changes”.I believe there is a reason these dyno numbers are all over the map. The correction factors account for air density changes but they can not account for things the PCM calibration changes at different conditions or the way the engine reacts to those changes.
At 12/1 compression and 10+ psi boost, the ignition timing is running at half of MBT. Someone smarter than me has reported that every 8 deg F inlet temp increase requires retarding the timing by 1 deg if you’re at the threshold of knock. When you are already 15 deg below MBT, that 1 deg really hurts power and torque, while the corrrction factors can not know and account for what’s going on in the PCM and how it affects torque output. For instance, if you dyno at 100 deg F and sea level, the correction factor will be something like 1.03 which will add about 20 hp to the readout. However, your ambient air is 23 deg over the SAE and 40 deg over STD conditions. That means you will be running 3-5 deg less ignition timing than the correction factor assumes, which could mean an error of 60-100 hp.
Some time back, one of the Whipple f-150 guys dynod summer vs winter. The difference was 50 hp IIRC and both we’re corrected to the same standard.
Normally, I am a proponent of dyno numbers but in the case that a) we are controlling timing to the threshold of knock and b) we are far away from MBT, you have to be extra cautious when corrections are involved. I see where one of the sheets has a correction of 1.25. The SAE standard even states that anything over 1.03 shall be disregarded and that’s not even considering the special case of the 12/1 supercharged coyote.
I agree 100%. I don’t even think that’s debatable.
“At 12/1 compression and 10+ psi boost, the ignition timing is running at half of MBT. Someone smarter than me has reported that every 8 deg F inlet temp increase requires retarding the timing by 1 deg if you’re at the threshold of knock. When you are already 15 deg below MBT, that 1 deg really hurts power and torque, while the corrrction factors can not know and account for what’s going on in the PCM and how it affects torque output. For instance, if you dyno at 100 deg F and sea level, the correction factor will be something like 1.03 which will add about 20 hp to the readout. However, your ambient air is 23 deg over the SAE and 40 deg over STD conditions. That means you will be running 3-5 deg less ignition timing than the correction factor assumes, which could mean an error of 60-100 hp”.
I’ll be the first to admit that I don’t understand the PCM’s determinations well enough to predict its reactions to variables. However...
Are you suggesting that Whipple didn’t select or at least attempt to optimise the conditions for the data they’re producing? Could they have picked up 50-100hp if they’d played the game differently? Or are you suggesting that each and every one of those Edelbrock cars are making 50-100hp more than they would’ve on the same day, same dyno as the Whipple?
I think the solution here is to try and find Dynojet sheets from other Gen 5 18-19 cars on stage 2 setup and see where it goes.
As you said previously, numbers matter.
You weren’t willing to accept my seat of the pants experience, or my datalogs, so I presented dyno sheets. Then they come into dispute...
We know that we can’t use the drag strip to demonstrate the difference in torque at anything under roughly 6000rrpm, so the dyno is literally the only tool we have left at our disposal.
I’m off to try and find Dynojet sheets for Gen 5 cars
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