grille wind deflector

[readytogo!]

I currently have the K&N intake on my 1.8l sonic, with no ram air duct pushing cold air to it.

 

[readytogo!]

Any air that gets into the grill will go through the radiator. You would have to remove an underpanel, or cut a hole in it for your idea to deflect air down to have an effect. In which case, blocking the lower grill and putting an opening in that underpanel so the radiator is sucking air from underneath the bumper will likely have an larger effect.

I had forgotten about the panel under it. In that case i will probably settle for making a partial dam on the grill.

 

[RaceThisLTZ]

Heh, that's silly. The heat in the intake charge after the compressor is a direct result of compressing the air. And NOT cooling that intake charge will result in pre-ignition (detonation) and the retarding of ignition timing. Which would be the most "not good" thing for MPGs.

In a warmer condition I would agree with you. But on a highway in the winter when ambient air temp is around 30 degrees or less, the air charge is freezing cold. I use a large block off for the lower grille with 3 1 inch holes in it and have had no negative side effect (car keeps temp with more then enough airflow from the top grill).

Colder air is more dense and there fore requires more fuel to burn at the same rate as it does when warmer. By restricting the air flow to the intercooler you are effectively allowing a warmer charge to make it to the motor, allowing the car to use less fuel for the less dense air. The holes I placed where to optimize the target tempt I was trying to achieve(20-30 degrees + ambient) with out it was roughly 40-50. Which is fine but I like a margin for error.

Compared to last winter I have noticed that the car warms up much quicker (40 degrees warmer by the time I get on the highway) and a much less noticed drop in mpg for the winter months(still able to get 40+ no problems).

I do not beat on my car in the winter...AT ALL and would not recommend it if you do this. Prolonged boost will heat soak the core over time with no airflow. THAT would in turn lead to your pre ignition

 

[trollbait]

Heh, that's silly. The heat in the intake charge after the compressor is a direct result of compressing the air. And NOT cooling that intake charge will result in pre-ignition (detonation) and the retarding of ignition timing. Which would be the most "not good" thing for MPGs.

I never claimed that compressing the air wasn't a source of heat. Just that conduction of heat from the exhaust side can add to the overall heat load.

 

[Swordsmith]

Looking in another forum recently, I saw someone discussing grill blocking. They said that when they got really aggressive, they actually lost a significant amount of mpg (30% or so), but after they backed off, they eventually ended up with around a 2% gain, blocking off about 50% of their grill (note, it wasn't a Sonic, so that's not necessarily the "right" % to block)

An idea I've thought about earlier would be to install a switchable gate for the intake, drawing either cold air out of the fender (through the snorkle hole, but with the saxaphone removed) or warm air by running a tube over the engine block, Injen style.

Coming up with something similar to pull air as needed over the radiator and the intercooler, but normally restrict airflow to just what's needed, might be interesting, and let us increase aero at the grill without paying a price for it.

 

[trollbait]

Some of that 2% gain could be from the aerodynamic improvements.

I have played around with warm air intakes in the past by pulling air from above the exhaust manifold. Even packed insulation around the air box. There was fuel economy improvement, but I suspect it was mostly due to speeding up the warm up time. Each engine is different in its reaction to warmer air, and it is possible it wasn't getting hot enough.

I've only checked it out a couple times, but ecomodders is a forum for efficiency car modding.

 

[Swordsmith]

Some of that 2% gain could be from the aerodynamic improvements.

Yeah I think that's the principal reason folks do grill blocking. There's plenty of warm air in the engine bay if you want to feed it to your intake.

The thought about warmup time is interesting though, that's certainly an issue with the 1.4T, its efficiency is fairly poor until it gets warm. Doesn't take all that long to get warm, mind you, but for people who do lots of short hop commuting, that still becomes an proportionally big factor.

 

[KGB Pilot125]

I block off my entire upper grill. I even ran some on the lower grill too when it is really cold. We had a few days here where the high was around -18 for 3 days and I had to drive 200 miles a day for work. even with all the openings closed off other than a 1 inch section on the lower grill I saw IAT's in the -5 to -10 range! Never would have noticed but the UG alarm went off.

You can run the upper grill completely blocked off and the lower one almost completely blocked off in temps of up to 60 degrees before the water temp gets over 230. Thats highway speeds of 75. It will cycle between 222 and 230