anyone experienced knock with HAI/WAI?

[hi tech hillbilly]

Just thought I would ask, I have searched and mulling it over in my head I still cant figure out how/why this works in favor of higher FE aside from getting the engine up to operating temp quicker and going open loop sooner. Is the theory that the air is already pre warmed and "takes a step out of the combustion process"? Not really takes a step out of it, but hastens the process? Please explain!

[GasSavers_maximilian]

The theory as I understand it is that it reduces throttling losses. The engine is sucking combustion air past the throttle plate which causes some resistance (this is especially true at very low powers that hypermilers tend to use as the plate is almost closed). Warm air is less dense, so contains less oxygen, so the engine needs more of it for the same level of power, so it opens the throttle more to admit it (sensors let it know how much oxygen is in there). The idea is that the extra effort moving more air is less than the losses shoving less air past a nearly closed throttle plate. Of course having less dense air means that you have less oxygen available for high end power. In theory your WAI setup could be adjustable or be designed so that the higher flow rates at high power levels overwhelms your heat source and then it becomes less of a WAI, regaining some of that upper end power.

[GasSavers_maximilian]

Something I've been meaning to do for a while: graph the amount more air required with WAI setups. There's a +60 F curve (roughly what I'm getting right now - although not at lower temps I'm sure), a +90 F curve, and one where the inlet temperature is at 180 F all the time. Of course I still have to turn these volume changes into an estimate of change in throttling losses, but that's more difficult. Sorry if the temp ranges aren't good for your area; they're the extremes we get here.



In case you care, the density of air is inversely proportional to its absolute temperature (in this case Rankine which is F + 459.67).

[dkjones96]

I experienced pinging under load with the WAI but I have iron heads unlike most users on here. I think engines with aluminum heads take the extra heat better.

[hi tech hillbilly]

I dont think 105-115*F temps would fare very well with higher intake air temps here. Has anyone ever tested advanced timing? I advanced mine until I got some pinging under load (full throttle with max A/C and headlights) with 107*F temps, then backed it out about 3 degrees and retested. I have driven 223 miles since I did this and havent seen any decreases yet.