Cold air VS Warm Air Intakes - what's the difference?

[hondaworkshop]

Originally Posted by hondaworkshop

My '00 Civic (with knock sensor) is showing ~10% mileage improvement with a WAI pulling hot air from right next to the exhaust manifold. Aside from driving style, it has been the best single thing I've done for FE.

Just to update, my anticipated gains were off due to gauge mis-calibration. I'm retracting the ~10% until I can tweak my WAI more.

[reformed]

To compensate for knock, you could use higher octane. That may or may not defeat the purpose of the WAI from a $ point of view, depends on how effective it is.

[jim-frank]

Water injection is also a common approach to reduce knocking.

[mrevo]

Originally Posted by oldschool

LMAO, now we can completely confuse the folks here Coyote, when I was doin my vapor carb building in the 80's we had an exhaust heated exchanger mounted directly on top of the stock carb so we could use both the carb and the vapor unit. This was a 74 Chrysler Newport with a 400 cu in engine. In stock form it got 12 mpg, runing hot air(265 degree air) in the stock carb it went to 22 mpg.

It could be that high compression effects the intake air temps viability to increase mileage.My truck is running a 10.75 :1 compression ratio and like you avoiding knock has been an issue. In the winter however I run a stock air cleaner with the heat stove off the exahust manifold and disabled the temp sensor inside the aircleaner, running the snout butterfly directly off manifold vacumn so when I am cruising I have hot air and when I am accelerating cold air; while I don't drive the truck enough to get any accurate mileage figures , I do know the hotair stove helps the trucks drivceability.

Hi,

I agree with this.
I had a 1979 Pontiac Trans AM with a 301 cc engine.
I changed the manifold vacuum hose from the aircleaner directly to the intake manifold and I saw dramatically increased fuel mileage, similar to yours. How ever this created a problem with detonation so it had to be driven carefully.
On newer cars seems to be different with the ECU compensating but there must be guide lines on what to change.

Thanks,

[BoNe-MD]

So after much reading, both here and from links, it seems that a Cold-Air Intake run to the Exhaust Manifold for heating then dumped into the Throttle Body would theoretically be beneficial.

Larger volume subsequently heated before mixture. Any thoughts?
I'll test it once I can get some gear.

[RH77]

Originally Posted by BoNe-MD

So after much reading, both here and from links, it seems that a Cold-Air Intake run to the Exhaust Manifold for heating then dumped into the Throttle Body would theoretically be beneficial.

Larger volume subsequently heated before mixture. Any thoughts?
I'll test it once I can get some gear.

First, welcome to EM...

The theory depends on the make/model of the vehicle. I've actually done this with a '98 Acura Integra with mixed results (highest reading was 180F). The ECU tends to retard the timing to prevent detonation, and can hamper FE efforts. I found 100F to be ideal in my case. Many Saturns, for example, increase efficiency at higher temps or if the ECU is fooled to think the intake air is hot (resistor mod).

Best FE to you...

RH77

[Rower4VT]

The idea of using a resistor on Acura/Honda engines to trick the ecu into thinking the intake air temp is "normal", when using a WAI, would probably work. I'm pretty sure Acura/Honda ecu's retard timing automatically when the IAT is high...beyond the point that would be needed to avoid knock. I have no way of measuring my ignition timing while driving as my car is pre-OBD-II, however I plan on running my WAI for a few tanks, then will add a resistor to reduce "measured" IAT by 80-100 degrees. Then run a few more tanks and see if there is a difference. The bonus with my set up is that I'm running E85 which is 105 octane, so knock is not really a concern.

Question: For the same given power output of an engine, would the vacuum be higher or lower when the intake air temp is significantly higher?

[slurp812]

Originally Posted by Beaver

I understand that cold air is denser and contains more oxygen by volume than warm air, but the reason for depowering the motor I don't quite get. Maybe if you can explain what you mean by "pumping losses" I'll begin to get it.

Small engines burn less gas. Its actually tricking the engine in to burning less gas by giving it less oxygen. Pumping losses are the work the engine has to do to force air past the throttle. That takes some HP.

[thinlines68]

Hi! new to ecomodders and i have been reading the CAI Vs WAI struggle. has any one tried preheating Fuel line with heater hose? I have seen pics & vids on it. I believe its to make the fuel easier to burn?

[steffen707]

Originally Posted by DifferentPointofView

at wide open throttle, you have (basically) no pumping loss at the throttle plate. so warm air intakes won't do anything here. but unless 55mph makes you have to floor it to keep going 55, a warm intake will do something. that something depends on the vehicle.

Diesels don't have a throttle plate, so you don't have a pumping loss problem from the T-plate.

UGH, i was thinking about this today because I have a d15z1 (VX) engine in a 96 civic hatch and have problems holding 65mph in lean burn, so i'm having to give it more throttle to (i'm assuming make more power) to maintain that speed. So if I make a Warm air intake, that is going to give me even less power, and then I won't be able to maintain say 60mph?

I was thinking that it wouldn't be incredibly difficult to make a "Y" valve that cuts off the cold air intake or hot air intake for whatever situation you desire. like using a choke on an old car to get it up to temp, then closing the choke. i could get the warm up the engine faster benefits of the WAI and then if i was in a highway situation where I needed more power to maintain higher speeds, I would just close that and open up my CAI.