An engine at operating temperature (coolant and oil temps) will create the same MPH regardless of the intake air temps (within reason). Too hot and detonation will happen. That means, the engine coolant and oil are the same temps regardless of weather temps.

HCCI is TOTALLY different than an Otto-Cycle engine. HCCI is basically a gasoline-fueled diesel engine. The last thing you want in an Otto-Cycle engine is pre-ignition, but that's exactly what you what from an HCCI. Apples...oranges

The grille block does 2 things. It maintains the engine coolant and oil temps but it also makes the car more aerodynamic by keeping air from entering the engine compartment. That along will make the car more fuel efficient. Like I said, if the engine temps are the same (20-deg or 100-deg) the engine should get similar fuel economy regardless of intake air temp.

That's because you sacrifice max power to get that advantage. As I pointed out before, a much better approach if starting from scratch is to designate a smaller engine if you have power to spare.

Careful you don't go too far with that (and I'm not implying you are). HCCI gains from increased compression ratios, not just improved combustion (yeah, yeah, and other stuff too like potentially lower throttling losses). Since the gains from increasing the standard compression ratios seen in normal spark ignition engines is pretty significant (the curve is still pretty steep at that point), this is probably most of it.

I'm saying that in that particular vehicle it works. 10 MPG is well beyond any conceivable margin of error for this test. I would agree that more testing needs to be done, but I don't buy the "Every car would have it already" argument. I can tell you that 2 of my 3 vehicles that I own have it setup from the factory. Manufacturers aren't solely concerned about mileage. They have to make sure the car passes emissions, and has good power. High HP numbers sell cars. WAI/HAI lowers these numbers. Yea, an affordable car can be made that gets great mileage, but if that was the only reason people bought cars was for high mileage numbers then everybody would either have a Geo Metro or Civic VX in their driveway. Do a search on the site. There are many others that claim to have positive results with WAI. For some reason Saturns do extremely well with WAI/HAI.

I'm just saying I wouldn't dismiss it so quickly.

I can't disagree that a really well controlled series of tests would be great. That said, however, we can say something in the absence of them. Copied from the HAI experiment thread:

When there's uncertainty, I just use the following:

(chance of success)*(estimate of benefit) + (fun of trying)
vs
(cost & effort to try) + (chance of damage)*(estimated cost of damage)

In this case everything on the right hand side is very low. Since the chance of success is mixed, and some people are claiming a good sized benefit I think it's worth giving a shot. You may assign different values to these parameters than I do, and rightly so.

More good reading:
https://www.nextautos.com/auto-shows/...inject-engine/
https://www.passagemaker-digital.com/.../200903/?pg=81

An A-B-A-B test would be sufficiently demonstrative - under condition "A" (i.e. cold air) you get a certain result, then you modify it to condition "B" (warm air) and you get a different result, then return the car to its unmodified condition "A" and ensure that the result returns to its previous value.

-BC

I 100% agree.

And I love the thread you have in you signature about doing a SCIENTIFIC experiment: https://www.gassavers.org/showthread.php?t=2

Warm air allows larger throttle openings and higher effective compression.

Warm air also allows less fuel to be injected for the same mass of air consumed.

Fuel delivery systems add fuel based on temperature as well as mass.

The power delivered by any engine is a direct function of the EFFECTIVE compression. Put a vacuum guage on your engine, keep the revs low, in the 1500 to 2500 range in the highest gear the vehicle can handle. Accelerate with the highest load, lowest revs, and lowest vacuum, without applying enough throttle to get into full load enrichment.

Voila, the secret to the pulse portion of hypermiling.

The concept that making a vehicle more powerful is basically flawed, when you are talking about an economy strategy. This is clearly demonstrated by the difference in mileage between a Civic SI and a Civic VX.

Understand "effective compression". All engines create power utilizing the difference between compression pressure and combustion pressure. The highest effective compression (lowest vacuum reading) is the highest effective combustion pressure for any given mass of fuel delivered.

Take a 2.5 liter 4 cylinder engine on a dyno. Put a 20 HP load of the engine. Measure the fuel consumption at 1700 RPM. Then place a 50 HP load at the same speed and you get 30 more hp, for half the fuel it takes to get the first 20 HP. That is due to effective compression being maximized.

If you have any manifold vacuum you are proportionately reducing the effective compression, as well as efficiency.

Diesels solve the problem by elimination of the throttle butterfly.


regards
gary

There's more than throttling losses at partial load. Frictional losses don' t decline quickly with load, so they become a greater proportion as it decreases. This diminishes economy. Diesels suffer from this too. Variable compression can help get around this, but is a much more complicated mechanism.