warmer air equals less dense air, thus less oxygen. less oxygen equals less fuel to burn said oxygen. less power but less fuel burned.
the decrease in power means that you need more gas to achieve the power needed but if the power isn't needed then less gas overall.
air expands when hot so there is less of it per a given volume at higher temps vs lower temps.
given this, your GPM at idle should be less with warmer air. also at a given throttle position, your GPM should be less. you will need more throttle to give you the same power like for climbing hills or acceleration but all other situations, you will use less gas.
the exception is if your vehicle doesn't take into account the air temp. and even then it may compensate by using the oxy sensor.
just my opinion.
Be the change you wish to see in the world
The time taken to pick apart someone else's scientific method could have been used drilling holes and mounting your own HAI, for your own "perfect unbiased trials." I will add that before summer hit my mileage went up with HAI. I ran 4 1/2 tanks with that as the only piece i changed. I never moved my sensor so as soon as these 100 degree days hit i was pinging like crazy. Now that its moved the car behaves normally. To take full advantage of HAI you have to make sure the sensor is as accurate as possible, or your timing curves are wrong and you can have potential engine damage and lack power unless you spend the $$ for premium fuel. The ecu is as much your friend as it is your foe.
Afterthought: I see a HAI not helping much if you do lots of city driving and are constantly trying to accelerate. More tq down low helps your economy and really isnt needed at flat steady rpm's.
You had a passenger on the way to the airport and I assume you dropped them off and drove back alone. 1 passenger plus luggage can easily account for the 7% difference.
For aggressive city driving without hypermiling strategies, maybe. For highway driving or decent city driving (coasting, DFCO, P&G), not at all. Apart from that, weight has little effect. The bigger reason lighter models get better mileage is because they can come with less power and/or taller gears.
Originally Posted by tjts1
No, it just doesn't add up. Hot air intake means lower fuel economy.
That runs counter to the experience of many users here, who have observed long-term increases attributable to their HAI.
Originally Posted by BEEF
the decrease in power means that you need more gas to achieve the power needed
Nope, it means that you need more throttle opening, not more fuel. Wider throttle openings are more efficient, if we assume the same amount of power produced (which is the case in this context).
The power loss can be fuel dumping or knock retard. A Scangauge will show both.
My GM 3800 Series II fuel economy is best at 100*F though anything from 80*F to 130*F is just fine. Optimum temps of 70*F to 100*F have shown up in other posts. Unfortunately the temperature is engine dependent which is why you need the Scangauge.
My WAI only requires me move a single piece of duct tape to vary the temperature.
I drove there w/ girlfriend and luggage. Drove back w/ girlfriend and same luggage
So this means you came back with a different and lighter girlfriend. Clever, but not clever enough to avoid getting caught.
Hot air intake means lower fuel economy.
Too hot or too cold means lower fuel economy. Everyone complains about "winter" mileage. The trick is to get the right amount of heat.
back to the original question, I have heard that 180 is a good place to be and that 200 is too much. mine without any adjustment to the physical unit will fluctuate from 130 to 179 (being my highest ever). this is just with temp changes in the day. if you set it up to run 180 all the time then your hot days may see 200 or better which isn't good (well from what I have heard).
I'd say to give lovemysan an PM and see what he says. the whole purpose of this thread was to get his opinion anyway.
Be the change you wish to see in the world
Consider this, in Phoenix Arizona the record temperature is something like 137 degrees F.
A car must pass emissions under these conditions, and I would think there is some reserve above that temp.
I have no way of confirming that with a scan guage (wish I did, but my car is OBD1).
My VX also has no knock sensor (read that on this forum), but I have never heard my engine ping on the cheapest gas I can buy.
Last winter with my DelSol it took 4 miles for the engine to warm up without a grille block. I never reversed the air intake (my simple WAI) on the Del Sol, but with the grille block it warmed up in 1.5 miles, with outside temps around 32 F.
For those with a scanguage the feedback is virtually instantaneous. In my case its fillup to fillup.
It seems to me that the difference is about 10-15% (fuel economy) and the max temp should not exceed 150F. Of course when it is 100 degrees the difference will be negligible. I tried reversing mine back to its normal position this summer and got the worst mileage in the last couple months, so in my case it seems to make a difference even in the summer.
That doesn't mean I am saying anyone is wrong, it just means that this is what I have observed. I would think the max temp would vary considerably from one car to another.
From 32 degrees to 200 degrees farenheit atmospheric density drops 20%.
There seems to be a lot of concern about WAI causing the engine to run hot. I dont think it will happen, if your cooling system is in good shape. It might happen if you completely block any airflow to the engine compartment. Even then it would be very hard to completely trap all the heat in the engine compartment and an electric cooling fan would run as long as it took to keep the engine cool. Most of your cooling systems heat removal work is due to combustion temps of over 3000 degrees not intake temperatures.
I like my simple intake snorkel reversal route to WAI because it allows the engine to breathe cooler air if you are at higher throttle openings, so when you need emergency power the volume of air entering the engine would also mean the air was cooler than at lower volumes, so you have better power when it is needed, even though I may never use that kind of power.
I have heard it observed that motors run cooler with HAI, for a given RPM, this would be due a smaller amount of charge not making so much heat. I think also less work is done in the compression phase.
Edit: BTW, "Cold Air Intakes" primarily benefit FE when they "get one over" on the ECU by introducing more air than it thinks it's getting. That and reduced pumping loss from a freer flowing intake can help.
I remember The RoadWarrior..To understand who he was, you have to go back to another time..the world was powered by the black fuel & the desert sprouted great cities..Gone now, swept away..two mighty warrior tribes went to war & touched off a blaze which engulfed them all. Without fuel, they were nothing..thundering machines sputtered & stopped..Only those mobile enough to scavenge, brutal enough to pillage would survive. The gangs took over the highways, ready to wage war for a tank of juice