Higher intake charge temperature has been found to increase the flame speed, the combustion reaction rate, the uniformity of the fuel-air mixture and reduce the heat transfer rate though the cylinder walls. This all adds up to the engine using more heat for physical movement and less being wasted.
The downside to this is that hotter air also tends to retard ignition timing and cause engine pinging. Different engines will react differently to warm air intakes and testing will need to be done to see if it will work for your specific vehicle. Saturns are known to react well to warm air intakes.
Its a 4.5mpg increase over my previous best, not EPA... its a 6.5mpg increase over EPA's 31 highway rating.
Unfortunately, you didn't test one factor. You changed at least three variables, and it's impossible to sort out how much of your gains came from the WAI/HAI, how much came from the increased 50 psi tire pressure, and how much came from drafting trucks.
You could drop your tire pressures back to what they were before the WAI/HAI, and don't draft on your coming trip. But since you'll be doing this trip in February instead of the Summer, I wouldn't be surprised if your mileage fails to reach your pre-HAI mileage. The current Winter weather introduces another variable. That's why ABA testing is so much better.
What I don't understand is with all these people and their scan gauges, why hasn't anybody just looked at the GPH of the engine with varying intake air temperatures while at Idle? I mean I have and I can tell you, if my Air Intake temperature is at 50F, my GPH will be at least .25 but if it's around 70 or even 90F, like if I parked a hot car for 5 minutes and then started it up again, then I can get a GPH reading of around .2. That alone should be enough to prove that a hotter intake charge means better fuel economy.
1. ScanGauge cannot measure GPH. It calculates GPH from other data, guessing what the fuel rate actually is but it is nowhere near accurate enough for that test.
2. Its GPH reading wouldn't change anyway; at idle you're already past its precision to calculate or display. That is, you might be looking at a .004 difference but it can only display two decimal places.
3. The difference at idle is fine when you're idling, but what's really important is what happens when you're not idling. Hypermilers don't idle much. Conditions, behaviors, and efficiency can be very different when idling than when not idling.
Its a matter of trying to emulate summer conditions in the winter. If anyone here is getting better mileage in the winter, then chime in with your proof.
Many factors of cold weather driving are not practically eliminated, but you can increase your cold weather starting temperature with a block heater.
You can increase the temperature of the coolant exiting the radiator by restricting the air flow over the radiator to increase the coolant exit temperature to resemble the same temperature in summer.
You can increase the temperature of intake air to match that of summer operation.
Now, you can argue the statistical proof of the improvement to try to (for whatever purpose) denigrate the improvements. You can refuse to accept the physics of the effects, but you can not show me a single instance where anyone on the board has EVER got better mileage at 0 degrees than at 80+ degrees.
I don't have any way to precisely measure the differences in temperatures (no Scangauge). If that is your threshold of acceptable proof, then continue to deny what any person with a decent understanding of physics would consider obvious.
Measure the temp of the coolant entering your engine at 0 degrees and at 100 degrees, after it has passed through the radiator. Blocking the radiator (done by almost every trucker on the planet in cold weather) improves mileage.
Increasing the engine temperature before every cold start increases mileage. In some cases it is impossible to start many cars without a block heater in extreme cold.
Increasing the intake air temperature decreases the density of the air and the heat promotes better atomization of the fuel and air. In effect it reduces the effective displacement of the engine and increases the partial load BSFC.
I am through with the endless debate, the physics are sound and the results go a long way towards dramatically reducing the cold weather mileage losses that are obvious on any gas log you look at from areas of the country that suffer from cold weather in the winter.
I am finished with this thread, so if your only objective is to get in the last irrelevant word then go ahead and waste the time.
Go to Alaska and try to deny the obvious when it's 40 below.