Yaris sedan grill block testing

[tweakmenow]

Fellow Gassavers, I believe this is the best of both worlds. A Coroplast plate sliding in a rain gutter shield (rail), operated by a choke cable.
Via Scanguage water temp, I keep the vent fully closed untill the water is up to temp. Then dependind upon OAT and vehicle speed, I know just how much to open the grill. Cheers...

[JanGeo]

Yeah I was thinking of that but then thought that one time you forget and get too hot is going to be a pain. I already had some coolent leak out the water pump on a new car probably from getting a little warm bearing in mind that the cooling fans still work should they kick in at 203 degrees even with the grill blocked air gets through the radiator from between the grill and radiator when the fans run. I may go with a big cable controlled flap anyway. Blocking the bottom of the grill may get your tranny and engine oil warmer on those cold days and can help more but I usually unblock from the bottom since that block is smaller and partially open already.

Looks like you have a A/F gauge - how is that working for you?

[GasSavers_RoadWarrior]

Spring load the flap open... tape a birthday cake candle between two ends of the linkage in the engine bay somewhere... = failsafe ... when the engine bay gets hot enough to melt the candle... the flap springs open

[tweakmenow]

JanGeo, I use the AFR gauge for a manual "lean-burn" system. Using an EFIE, I turn it off when the car needs to develop power, such as hills or accelerating onto the highway. I love it, and have the same system in my Winter Ride.

[Nate R]

Originally Posted by tweakmenow

Using an EFIE,

What's that?

[tweakmenow]

Nate, Here is a good link:

http://www.fuelsaver-mpg.com/store/i...c0f0eb94fc35f6

[Slothman86]

In theory, You would get better fuel effiency if you had cooler air to your engine, if your coolant was cooler would that help as well?

The problem with the open grille is that it creates drag. There is still drag id you have the block as well just not as much but... What if you channeled the air? instead of having it go around the front, almost like the air would go through you...

[JanGeo]

Lubrication is designed for hot conditions so unless you can run very well controlled engine temps and lighter oil the only other solution is to keep everything warmed up ala the grill block. It does a couple of things - prevents some air from getting under the vehicle causing turbulance there and it keeps the engine and tranny warmer in colder weather. The idea is to get the air to flow around the vehicle to the sides or top also think of it as air flowing over the least amount of surface and that surface is smooth compared to the radiator and engine and underside that is very bumpy. You don't want to run cooler coolent at least not too cool or else the engine absorbs more of the combustion heat and runs less efficiently.

[Slothman86]

Deal, I see what you're talking about but a more fuel efficent engine gives better MPGs as well. Engine temp is one of the variables you should worry about.

[tasdrouille]

I did a bit of research before going with a WAI. Here's what I came up with.

WAI arguments

In favor:
- Pre-heated intake mixture at low rotational speed improves combustion. (Chiu and Horng, 1992)
- Specific fuel consumption varies inversely proportional to the square root of the suction air temperature (Nakajima et al. 1969).
- Higher ambient temperature is found to increase the flame speed, the combustion reaction rate, the uniformity of the fuel-air mixture and reduce the heat transfer rate though the cylinder walls (Pulkrabek, 1997).
- For lower temperatures, only a small part of the injected fuel is vaporized, causing nonhomogeneity. As a result, lower flame speeds, higher unburned mixture, higher hydrocarbons and carbon monoxide emissions, and loss of power are observed (Pulkrabek, 1997; Heywood, 1988).


Against:
- Engine brake torque varies inversely proportional to the square root of the suction air temperature (Nakajima et al. 1969).
- Higher intake air temperature increase the occurence of engine knock (heywood 1988).
- At high engine rotational speeds, higher intake mixture temperatures decrease the volumetric efficiency of the engine (Chiu and Horng, 1992).

References:
Chiu, C.P., and Horng, R.F., 1992, ?Effects of Intake Air Temperature and
Residual Gas Concentration on Cycle-to-Cycle Combustion Variation in a
Two-Stroke Cycle S.I. Engine Equipped with an Air ? Assisted Fuel Injection
System?, JSME International Journal, Vol. 37, N.4, pp. 957-965.

Nakajima, K., Shinoda, K., and Onoda, K., 1969, ?Experiments on Effects
of Atmospheric Conditions on the Performance of an Automotive Gasoline
Engine?, SAE Transactions, SAE 690166, pp. 745-766.

Pulkrabek, W.W., 1997, ?Engineering Fundamentals of the Internal
Combustion Engine?, Prentice Hall, Inc.

Heywood, J.B., 1989, ?Internal Combustion Engine Fundamentals?,
McGraw-Hill Book Co.