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Wanted to post some visual references to show how heat effects power in these cars since there have been some discussions about that and a lack of comprehension and/or understanding in the community on this subject.

These are screenshots of a 0-100 mph datalog from a car I tuned the other day which is a 16 DCT VT and typical of a tuned car. Mods are SRI, second cat delete, muffler delete, HKS M45XL plugs, on 93E10 pump gas. Last two are showing difference in power made(essentially engine load absolute %) and parameters from one gear to the next at the same rpm caused solely from heat. You can easily see the boost drop as well from the heat and maps related to that.

Things to note in general and within reason:

Air Fuel Ratio Measured : Lower means less power but more cylinder cooling which will allow more ignition timing. Higher means more power but less cylinder cooling which allows less ignition timing.

Engine Coolant Temperature: Higher will pull ignition timing and lower will add ignition timing.

Engine Load Absolute: Higher means more power made, lower means less power made. Essentially this is the air density % going through the engine.

Intake Air Temperature: Lower means higher density and more power from that and added ignition timing. Higher means lower density and less power from that and less ignition timing.

Timing Advance: This is final ignition timing being made. Lower means less power. Higher means more power.

Feel free to discuss anything in general regarding this whether you understand this or just want to learn more about it.

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2015 RB Accent-not so stock 馃か
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So all of this is before meth injection yes?
Stock IC as well?
So the first picture is first gear, second picture 2nd gear, and so on?
I'm trying to understand the charts and they're relation to the numbers.
Thanks
 

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So all of this is before meth injection yes?
Stock IC as well?
So the first picture is first gear, second picture 2nd gear, and so on?
I'm trying to understand the charts and they're relation to the numbers.
Thanks
Mods were listed that were not OEM and so was the scenario which was a 0-100 mph pull. All 3 pics are the same pull. One without anything blocking all the lines, another at top of 3rd gear, another top of 4th gear. Point of this is showing power loss from top of 3rd to top of 4th from heat alone on a car with nothing done to help keep temperatures in check.
 

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1. Is Engine Load Absolute a rough approximation of horsepower? I feel silly asking that but it seems like those numbers correlate pretty closely.

2. So ambient temps dropped 2 degrees, IAT's rose about 30 degrees, and coolant temps rose about 10 degrees And this resulted in minus 0.5 degrees of timing advance and minus ~2.5 psi which resulted in ~15% less output (35 or so less horsepower-ish)?
 

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Discussion Starter #6
1. Is Engine Load Absolute a rough approximation of horsepower? I feel silly asking that but it seems like those numbers correlate pretty closely.

2. So ambient temps dropped 2 degrees, IAT's rose about 30 degrees, and coolant temps rose about 10 degrees And this resulted in minus 0.5 degrees of timing advance and minus ~2.5 psi which resulted in ~15% less output (35 or so less horsepower-ish)?
Yes it will correlate somewhat to power made +/- based on mods, transmission, and the other parameters with afr and timing being the more important ones.

Ambient will vary some as you drive as seen in the log. But yes iat rise a lot same as ECT making boost with the OEM components. The load lower due to heat gains/boost drop, richer afr, and lower timing results in much less power/absolute load as shown just in a single 0-100 mph pull. Now imagine power loss with repeated heavy throttle..... This is why I recommend to people the cooling mods that I do.....
 
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Oops. I didn't even notice the a/f ratio. My rough math had the decrease in output from the timing and boost drops at about 20-25. I knew there had to be another factor there that I was missing.

So, that decrease is completely due to temperature increase? It has nothing to do with the tune?
 

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Discussion Starter #8
Temperature increase itself and causing the tune to pull additional power. Once better fuel and cooling are in place it will not do this and you can setup tune to not pull as much or any power. :)
 
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A little mind exercise to show that pressure/boost can be misleading. Take two identical tire rim combinations, add air to one at 35 psi. Add air to the second at 40 psi. Now we know that the 40 psi tire took longer to fill and has more molecules of air in it. If we had a very accurate scale it would even weigh more. Now leave the 40 psi tire in the shaded garage and take the 35 psi tire out on the hot track and run the crap out of it for 10 laps. Pull in an check pressure, could very well be 40 psi, same pressure as the tire in the garage. So we increased pressure but we did not add a single molecule of air.
 

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A little mind exercise to show that pressure/boost can be misleading. Take two identical tire rim combinations, add air to one at 35 psi. Add air to the second at 40 psi. Now we know that the 40 psi tire took longer to fill and has more molecules of air in it. If we had a very accurate scale it would even weigh more. Now leave the 40 psi tire in the shaded garage and take the 35 psi tire out on the hot track and run the crap out of it for 10 laps. Pull in an check pressure, could very well be 40 psi, same pressure as the tire in the garage. So we increased pressure but we did not add a single molecule of air.
But the density of the hot tire would be less than the cooler 40 psi tire no?
 

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Yes, the density was greater in the 40 psi tire to begin with and therefore the greater weight. We raised pressure in the 35 psi tire but never added any molecules, we only added heat energy raising pressure.
 

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Yes, the density was greater in the 40 psi tire to begin with and therefore the greater weight. We raised pressure in the 35 psi tire but never added any molecules, we only added heat energy raising pressure.
Good analogy.

I always explain to people that to make power that air flow, density, cooling capacity, and fuel capacity are the most important things to have in place other than mechanical to hold the power.
 
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