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I think we all know that this car make more power when it's cold out than when it's hot out. That's true of all internal combustion engines. I've noticed that my best lap times have always been with it's cool out so I wanted to try to quantify what my butt dyno had been feeling.
I've been using the Aim Solo DL to capture data from my track events and wanted to use the built in math channel for calculating wheel power to quantify the power loss. I did change the calculation slightly to output in HP instead of kW. The formula is:
What you see are 3 laps of VIR and I've zoomed in specifically on the back straight since it's a nice full throttle run from 2nd gear up in to 5th. It's also up hill. The blue and red laps are from last weekend and are on MPSC2 take off tires. The green lap is the 1:59.2 lap from earlier in the year on A7s. The tire choice certainly affects the overall lap times (as did conditions and traffic) but shouldn't affect the data shown.
Blue: 2:06.228 - run 19/ lap 8 (afternoon)
Red: 2:07.565 - 11/3 (first run of the morning)
Green: 1:59.229 - first run of the morning back in April
I've included the Power calculation, GPS Speed, ECT, and IAT. The IATs generally tracked pretty closely to ambient temps so use that as a guideline for the ambients that day. I know that green lap ambients were in the low to mid 30's, the red was probably upper 70s and humid, the blue upper 80's and humid.
As you can see, the ECTs seem to be well in check and are relatively consistent. The IATs also seem to be in check for the ambient temps but the car clearly makes a lot more power with cool dense air. While I didn't show an example here, the data also shows that the car doesn't seem to drop off much from first to last lap in a session in terms of power.
You can also see the effect of drag as the car gets further down the straight and acceleration slows substantially.
what the data is quoting is obviously PRE-blower IATs which is not as relevant as post-blower IATs also known as IAT2 on factory supercharged cars. You can see the IAT is very low and never changes which is sign of it being pre blower readings.
Also the power values dont make any sense at all. your formula cannot account for the myriad of variables involved in calculating HP solely from how fast a car accelerates.
Over in a Cold Air Intake thread I talk about the "multiplying" effect of a supercharger on inlet restrictions. I think it makes sense for the reasons I outline there that any deficit in intake air in front of the throttle blades will be amplified by the time it's through the compressor.
It's not a 10% drop in ambient air mass, but let's say it is for simpler math, and let's say the supercharger has a multiple ratio of 1.8x.
Instead of 37.6cc of air (10% of 377 cubes) you lose 37.6 x 1.8 == 68cc of air. Big difference between 37 and 68cc, and that's why supercharged engines feel like they take a bigger hit... they do!
what the data is quoting is obviously PRE-blower IATs which is not as relevant as post-blower IATs also known as IAT2 on factory supercharged cars. You can see the IAT is very low and never changes which is sign of it being pre blower readings.
Also the power values dont make any sense at all. your formula cannot account for the myriad of variables involved in calculating HP solely from how fast a car accelerates.
It's actually directly correlated. We see 80-100* delta between ambient, and IAT 2.
While it's not the actual IAT 2 reading, there's is data to show the relationship between the two.
what the data is quoting is obviously PRE-blower IATs which is not as relevant as post-blower IATs also known as IAT2 on factory supercharged cars. You can see the IAT is very low and never changes which is sign of it being pre blower readings.
Also the power values dont make any sense at all. your formula cannot account for the myriad of variables involved in calculating HP solely from how fast a car accelerates.
I didn't come up with the formula. The folks at Aim did. True that it's not going to show true HP but it is useful for comparing relative power under the right circumstances. Here I have isolated it to a long section of the same track that is just WOT.
It's actually directly correlated. We see 80-100* delta between ambient, and IAT 2.
While it's not the actual IAT 2 reading, there's is data to show the relationship between the two.
NO, IAT1 will always be higher or in certain driving conditions equal to ambient temps. IAT2 is measured post blower, post compression and post intercooler which means temps can be either be slightly hotter than IAT1 or MUCH much hotter depending on what you're doing.
Take the following example and consider ambient temps to be the constant at 18 degrees Celcius.
What this tells you is that while Ambient temps does effect IAT both pre and post blower, you cannot simply add an arbitrary value to it to "estimate" true inlet air temps, which is why you need sensors for that. Ignition timing adder tables references IAT2 on cars equipped with this sensor, and references MAT (Manifold Air Temp) - which is a calculated figure based on a few sensor outputs - on cars not equipped with a physical sensor (think N/A cars).
I didn't come up with the formula. The folks at Aim did. True that it's not going to show true HP but it is useful for comparing relative power under the right circumstances. Here I have isolated it to a long section of the same track that is just WOT.
I fully understand but if you think of all the variables required to even come close to correctly estimating HP, such as the weight of the car, gearing, aerodynamics, engine coolant temps, ambient air temps, density altitude, tarmac slope, and so on so forth.
NO, IAT1 will always be higher or in certain driving conditions equal to ambient temps. IAT2 is measured post blower, post compression and post intercooler which means temps can be either be slightly hotter than IAT1 or MUCH much hotter depending on what you're doing.
Take the following example and consider ambient temps to be the constant at 18 degrees Celcius.
What this tells you is that while Ambient temps does effect IAT both pre and post blower, you cannot simply add an arbitrary value to it to "estimate" true inlet air temps, which is why you need sensors for that. Ignition timing adder tables references IAT2 on cars equipped with this sensor, and references MAT (Manifold Air Temp) - which is a calculated figure based on a few sensor outputs - on cars not equipped with a physical sensor (think N/A cars).
Very true. We meant in terms of a "steady-state" environment on track, where we're gathering our data. Lower load scenarios will absolutely have a lower temperature climb. Thanks for the correction.
what the data is quoting is obviously PRE-blower IATs which is not as relevant as post-blower IATs also known as IAT2 on factory supercharged cars. You can see the IAT is very low and never changes which is sign of it being pre blower readings.
Also the power values dont make any sense at all. your formula cannot account for the myriad of variables involved in calculating HP solely from how fast a car accelerates.
Also I think you need more variation in coolant temps to see what the car can do otherwise we're extrapolating what 30* increase would do based on that showing 1* increase in temps.
07-04-2016, 11:16 AM
[Data] Power Loss with Ambient Temps
