Intake modification

[hobbit]

When the WAI isn't in place, I've just been running around with the
airbox inlet open and no tube on it. Took the stock intake snorkel
out, and it opens up a whole lot more working room on the right
front corner.
.
I *think* the WAI helps with warmups, but has relatively little
effect in steady-state. However, I'm going to try to do some more
controlled A/B testing this winter including warmup timing in as
similar ambient conditions as I can manage. Everything to date with
it has been sort of seat-of-the-pants observation, but then again I
think I only had one sub-50mpg tank last winter.
.
_H*

[hobbit]

When the WAI isn't in place, I've just been running around with the
airbox inlet open and no tube on it. Took the stock intake snorkel
out, and it opens up a whole lot more working room on the right
front corner.
.
I *think* the WAI helps with warmups, but has relatively little
effect in steady-state. However, I'm going to try to do some more
controlled A/B testing this winter including warmup timing in as
similar ambient conditions as I can manage. Everything to date with
it has been sort of seat-of-the-pants observation, but then again I
think I only had one sub-50mpg tank last winter.
.
_H*

[donee]

<div class='quotetop'>QUOTE(gazz @ Sep 13 2007, 04:38 PM) [snapback]512060[/snapback]</div>

I read about re-routing the air intake to pickup hot air off the exhaust. This is a bit extreme for me, has anybody made a more simple mod such as just removing the pipe from the air filter box so it picks up air from the engine bay which should be a bit warmer rather then a cold pickup from the front of the car.

Gary
[/b]

Hi Gary,

The Prius already pulls intake air from a rearward directed airhorn, inside the engine compartment. There is no warm air or ram air plumbing. Its off on the passenger side up above the engine. At least that is how the US version Prius are.

[ilusnforc]

<div class='quotetop'>QUOTE(subarutoo @ Sep 13 2007, 02:43 PM) [snapback]512067[/snapback]</div>

Most people want to bring in cold air. There are all kind of kits for that for increasing vehicle performance (never seen a Prius kit). Why would you want to go against traditional wisdom, and bring in hot air?
[/b]

If this makes sense...
Most cars use COLD air intake for performance, to gain more power. The way they gain more power is because colder air is more dense, more dense air means more fuel, more air and fuel means bigger boom, bigger boom means more power (more fuel = less economy).

However, striving to get better fuel economy in a Hybrid, some actually route a tube from their intake down near the exhaust manifold or catalytic converter to draw heat into the intake. The reason for this is the opposite of above... Warmer air is less dense, less fuel is mixed with less dense air and there you have it, less fuel means better fuel economy (in theory at least). Whether it actually works or not, I do not know... I've never tried it personally, but it is well famed on the Honda Insight which I used to have before the Prius, and many Insight owners claimed improvements from such a modification. The only real drawback I can see is drawing warm air from the catalytic converter means it takes longer for the it to warm up (catalytic converters only work at a specific temperater range) so it my have a negative effect on your emissions, however slight your benefits may be.

[subarutoo]

It doesn't make sense to make a change that only benefits during warm-up. You spend, what 1% in warmup, and 99% of the time at operating temperature? I'd rather forget about the warm-up and have the car perform optimally 99% of the driving time. just my .02.

[statultra]

i ran both my 05and 01 without that tube going to the box, and the exhaust note is much louder, power seems to reduced though

[ilusnforc]

<div class='quotetop'>QUOTE(subarutoo @ Sep 14 2007, 02:14 PM) [snapback]512635[/snapback]</div>

It doesn't make sense to make a change that only benefits during warm-up. You spend, what 1% in warmup, and 99% of the time at operating temperature? I'd rather forget about the warm-up and have the car perform optimally 99% of the driving time. just my .02.
[/b]

I wouldn't think the benefit is only during warm-up, if it benefits warm-up at all. I think most of the benefit would be while driving. Basically, this mod would have the same effect as putting something over the front grille or in front of the radiator to block airflow in the winter. The engine is more efficient at certain temperatures and theoretically you would consume less fuel by taking in warmer less dense air (because less fuel is mixed with less air). I would probably conclude that in colder climates or during colder months (depending on the region) there would be some benefit with this modification especially if combined with a blocked front grille or radiator and as some have done in the really cold regions like Canada you could wrap the engine with insulation and add a block heater. Down here in Texas we shouldn't have to worry too much about these because the car is already taking in air at 100+ degrees right off the hot pavement. I'm consistently averaging 60 - 62 MPG with half of my driving in the afternoon and the other half at night when it's cooler.

[msirach]

I haven't tried it on the Prius, but it really works on the Insight. I had removed it about a month ago since the air temps were around 100 here. It was still disconnected this week when early a.m. temps were down around 50. I ran 2 days like that and it was very hard to hit lean-burn and end up with even low 70's mpg on my 49 mile each way commute. I put it back on and it was instantly back up to upper 70's to mid 80's. The 1 mile to the highway in the morning without hot air was no more than 54mpg. It was 49 this morning when I left at 5a.m. and I was at 72 at the highway. Intake air temp in 1 mile was up to 94 instead of the 49 of the air temp.

The warmer air sends a signal that tells the module that it can lean the fuel. I have ran it up to 135 degees intake air temp. I monitor it with the scangauge and/or laptop OBDII program that records all the trip system info.

[gazz]

Thanks for all your comments, I know we are dabbling but it is interesting.

I have a thermometer with a remote sensor so for curiosity I will try it under the bonnet in a few different locations, also have SGII so I can see the reported intake temperature.

Thanks

[jayman]

I've never tried to reroute the intake air for the desired effect. That said, back when cars and trucks had carbs, they were factory equipped with a "heat stove" kit. The system had a sheet metal "hood" over part of the exhaust manifold, and a flexible duct like a clothes dryer vent duct leading up to the air cleaner.

A fairly simple bi-metal thermostat in the air cleaner snorkle would close below a certain temperature, which would move a flap and close off exterior air to the air cleaner. All engine intake air would be pulled from around the exhaust manifold.

I'm not sure about any potential fuel economy benefit, but if the flexible pipe fell off or the flap jammed - or the metal hood simply rusted away to nothing - then the carb would ice up in very cold weather.

I've had very good luck with blocking the exterior grille, there is absolutely a fuel economy benefit and much more heat for the cabin. I use flexible 1/2 inch foam pipe insulation to block the two upper slits, and some rubbery felt stuff I had on hand and cut to fit to cover the lower grille.

At -40 with the grille unblocked, I was using 9.8 l/100km in stop-and-inch city driving. That's around 29 MPG Imperial gallon, and I was also freezing my butt off. With the grille blocked, the same city driving at -40 I was using 7.5 l/100km, or 37 MPG Imperial gallon.

Even 9.8 l/100km isn't too bad compared to the vehicle it replaced, a 2000 GMC Sierra pickup with a 5.3 litre V8. With the grille blocked, the same city driving it used 38.4 l/100km.

That's around 7 MPG, Imperial gallon