IAT theory discussion

[porshuh]

So in my past experience with performance cars - the lower the intake temperature, the better. I realize that this is not the case with the Insight. I understand that low intake temps inhibit lean burn...but why exactly is that?

I am also curious what IATs people see in the summer with stock intake (presumably "ideal"), and what they can drop to with sub 32*F ambient temps (under stock setup). Finally, what can one expect (and what should one attain for) after doing a warm air mod and driving around in freezing temps?

I'm not looking for air intake mod instructions, as that has been detailed in great....detail (/austin powers).

[Eli]

I'm not entirely sure why cold air inhibits lean burn, I guess just due to the density? It's not impossible to get lean burn with very cold IAT, it just closes the window for it. So if the air is X density at X load, it commands the car out of lean burn. Something like that.

With a stock intake in the summer, I see IATs in the 110 - 125 degree range, with ambient at 75 - 95F. From what I've read, this seems to be the sweet spot - hotter temperatures don't seem to hinder, but they don't seem to help either.

My IAT was about 70 degrees last winter driving through the mountains with ambient at -2 degrees. I'll have to pay more attention this winter.

I'm wanting to do the mod too.

[AbCaRed00]

Originally Posted by porshuh

I am also curious what IATs people see in the summer with stock intake

I've had 42C, 107F with normal intake in the Alberta Badlands, not unlike some parts of SW USA in part.
Have seen 50c, 122F with my hot air mod that loosened up and was sitting directly on the heat shield in 25C, 77F ambient temps, ... crawling in city traffic on hot asphalt. [pulled over and moved it]

No gains over 110F [43C] so is said in the old reports in the forum.

fwiw: VW aims for 86F, 30C for their vehicles' 2.0L engines for efficiency if I recall what was written on their warm air box if that matters for winter.

EDIT: I have run my own rudimentary version of the the warm air mod in -20C conditions for a few days now and observe that at speeds below 70kph and lower, the intake air temp has been as high as 9C, closer to 70kph it's nearer to 6C. At highway speeds of 100kph and more, the IAT in the -20C ambient conditions with considerable windchill is around 2C ±2 Celsius degrees.
I have the radiator blocked completely, however the upper and lower air entrances below the hood and at the grill are not covered as yet.
I have today adapted an aluminum roast pan by wrapping it around the catalytic converter heat shield to duct more warm air to the intake.

Radiator temperatures can be seen at 92-93C ±3 Cecilius degrees in cruising with the rad blocked after some effort getting heat into the engine. The highest temp, 95C is seen for a very brief time.
Without the rad covered, in ambient –20C, the coolant temperature was only around 67C on the highway.
The coolant temperature indicated was -2C, after sitting all night and half the day without starting, which calls into question the accuracy of the Insights coolant sensor as read by the Scangauge at lower temperatures.
None the less, plugging in the vehicle's block heater for about two hours in a sheltered location in -20 conditions, which can fairly safely be assumed to be the real temperature of the antifreeze, resulted in a measured value of 23C. Upon starting the vehicle with mixing of the fluid in the coolant system the temperature rapidly declined to 18C. The warmup period was markedly quicker, getting to above 60 degrees in approximately 4 or 5 miles in weekend light city traffic. Heater was on maximum 32C, fan was maximum defrost setting which involves the A/C.
Fuel consumption was in the order of 5L/100km, the IMA is compromised by internal resistance lessening assist and regen bars, but the SOC was reading full charge, yet force charging at 4 bars while the vehicle warmed.
Eventually with warmth the IMA was almost normal... and that's about it

[edit: later addition of aluminum roast pan as shroud around heat shield for warmer air intake and more lean burn.] [link to pic of ambient sensor relocation for more autostop]