Hi, I am interested in your hot air intake mod for my 05 Prius. What kind of improvement in fuel economy do you get?
bernzx

 

Hi Wayne,

You might want to discuss this with "Hobbit," you met at Tour de Sol:

Back in February, he performed hot-air intake testing and posted these result, " Having failed to discover any difference in steady-state travel mileage between warm air and cold air intakes, I've since done a couple of attempts at a cold-soak-and-them-warmup tests. . . ." He attempted to see if it would help warm-up the ICE systems sooner and concluded,". . . . Again, I can detect no major difference in ICE warm-up time, between the warm-air intake pipe and no pipe at all. . . ." (Posted in "Prius Tech Stuff", Feb 23, 2006, 2:01 pm)

http://autos.groups.yahoo.com/group/...sage/15652?l=1

The consensus was the warm-air intake was most effective on vehicles with "lean burn" engines that are air intake temperature sensitive. For example, the Honda Insight needs warm air at the intake to go into "lean burn" mode. But Hobbit's testing pretty well demonstrated it is ineffective on his NHW20 Prius but we're always interested in hearing about other experimental results.

There is solid evidence that the ICE block heater is effective and Ken from Japan reports warming the transaxle was also effective. I'm planning some testing this winter using:

• 1500 cc electric block heater - known to be effective on all models<
• transaxle pan heater - Ken reports one successful experiment in Japan and the Dept. of Energy transaxle study and my on going transaxle oil studies indicate this should be effective<
• automatic air inlet block - reduces the amount of cold air for both drag and heat management in cold weather<

Back in the old days of carborator equipped engines, manifold and warm air were needed to improve fuel vaporization and deal with carborator ice. In aviation, all carborator equipped piston engines have a carborator ice control because in humid air conditions, the fuel vaporization can deposit ice and lead to a loss of power and engine failure. Fuel injection, like we have with our Prius 1500 cc engine, all but eliminates this requirement.

By all means, I would never stand in the way of someone who wants to supply warm air to their Prius engine. But I have plans in another direction, first, and Hobbit's testing last winter was pretty through showing no measurable improvment.

Bob Wilson

 

A better modification to allow the prius to warm up quicker would be A larger heat reservoir for the engine coolant system. I think it was BMW that offers this as an option on their higher end cars. they heat up about 10 pounds of phase change material using engine coolant. The phase change material is stored in a small insulated thermos-like container, even after sitting out in the cold for 2 days, the instant the engine starts you get 170 degree F coolant flowing out of the thermos. BMW uses this to supply instant cabin heat on startup. The prius could use this exact same technology to provide complete engine warmup in about 30 seconds, dramatically increasing FE for short trips.

 

First,

WELCOME to GreenHybrid.com. By all means take a look at the database and see if you want to start recording your data. Also, we've got a FAQ on Prius techniques. BTW, where are you from?

I've got an NHW11, 03 Prius, which never had the thermos. Instead, I just got my JC Whitney coolant heater and pan heater for the transaxle.

This weekend, I'll be installing them with a timer operated, 120 VAC extension cord in the garage. Around 4:00-6:00 AM, the timer will come on and if the extension cord is plugged into the Prius, both the engine and transaxle will warm up to operating temperatures by the time I'm ready to head into work. This should all but end the morning 'warm-up' and associated higher fuel consumption. <GRINS>

Bob Wilson

 

I've thought about using a J.C. Whitney pump/heater just like you are talking about, but my least efficient trips are the little one or two mile jaunts that i end up taking without any notice. Thats why I 've been looking into parrafin wax as a phase change material stored inside of a $4 steel, vacuum insulated thermos. The unit charges (heats) itself off of the wasted engine heat, and it's heat is available without any notice. Between 150 and 180 degrees F, the parrafin wax holds about 100 times as much heat as an equal volume of engine coolant. The problem I ran into was that there doesn't seem to be anywhere in the engine compartment where i can mount even a small thermos. My prius is an '06 so i probably have the insulated coolant reservoir (thermos) do you know if there is a way that i could access the inside of the thermos to drop a sealed packet of parrafin in there?

I've been reading the techniques areas of GH for awhile and every tank sofar i've gotten at least 50mpg (my girlfriend likes to drive 80mph on the freeway when she uses the car, otherwise i would probably average about 55mpg). I live near detroit michigan, very cold on winter mornings, so i really hope someone comes up with a good system to warm the car up quickly both for the benefit of the engine, and the passengers.


The biggest reason i didn't go with the plug in coolant heater was because of the amount of electrical power it consumes 1000 wat heater running for 2 hours a day is 2kwh per day. my winter time electrical consumption is only about 8kwh a day. (i'm planning on building an off grid home next year and i'm trying to adapt to electrical consumption that a PV system that i can actually afford is able to supply.

 

Hi,

Owch. I can't help you. My NHW11 is so different from your NHW20 that I wouldn't have a clue about where the 'empty spaces' are. One thought is to use the crush space behind the bumpers but that eliminates the 5 mph safety factor. I wouldn't put it in the cabin either.

Let me suggest getting the maintenance manuals. They are a little pricy, mine were nearly $300 for all three. But you might be able to get by with a smaller set. Others have reported success using the Toyota online service and downloading like mad to get all of the PDFs on media.

We're not so cold in Alabama but I can see both the cold temperature impact and also the initial warm-up that happens even in the summer. I'm out to minimize the initial warm-up, year round.

Sounds like a good plan. In my case, a 750 W. thermostaticly controlled ICE coolant heater and thermostat controlled transaxle oil pan heater will handle my needs. Having them on a timer allows them to pre-warm the car early in the morning strarting at 4 AM. By the time to go to work, everything should be ready to go.

There is another source I'd been thinking about . . . exhaust pipe ducting. That heat is 'free' and comes on quickly. My thinking was to bring the ducting forward and have a 'jacket' for the transaxle warm-up. I wouldn't try to route it to the ICE since that is 'shipping coal to Newcastle.' But the transaxle does not have a direct, combustion source of heat.

The transaxle warms up from waste heat from MG1/MG2 and mechanical gear losses . . . all of which come after the ICE generates the power with 66% loss of heat energy. That is why my transaxle oil pan will get the 250 W. contact heater that will operate at least under my transaxle thermister managed control (no need to burn-up the oil early.) Eventually, I may go with a PID controller.

BTW, you might take a look at the "Prius Technical Stuff", Yahoogroup. We've got quite an archive of engineering papers and studies. Those are the folks who have figured out 'the details'.

Bob Wilson

 

Who ever said an old thread can't learn new tricks?

Living in an apartment in New England (cold winters, no accessible AC power) the paraffin wax thermos really intrigues me. I wonder if it would be possible as a retrofit? The biggest question I have is how to keep the bottle fully insulated while the car is parked, yet get the engine coolant through it when you start? My feeble mind sees this as a bit more complicated than throwing the bottle in-line with the radiator, with a need for some kind of control system. Still, I'd be willing to look into look into it for my own use.

 

My feeling is Hobbit's test was questionable.
http://autos.groups.yahoo.com/group/.../message/15686

One of Estima Hybrid enthusiasts found 35C intake air temp is the best for mileage three years ago.
We believe the 35C is adequate for Prius too.

Ken@Japan

 

Hi Ken,

One of the great things about science and engineering is we can discuss different experimental results and seek new ways to resolve unexplained data. It means we are humble enough to let our understanding be improved by new experimental data and Ken has given me a 'heads up.'

Heating the air to 35C would increase the density altitude, making the engine perform as if it were two thousand feet higher. This could result in the throttle plate being opened further and reduce some pumping losses:



It would be interesting to find out a density altitude change improves ICE efficiency. The 35C intake air would also improve vaporization although I find it hard to believe the Prius has a problem in this area.

I will consider looking at hot-air intake in the future, after I get the transaxle and ICE pre-heaters working. My transaxle temperature measurements show it takes about 18 minutes to reach a steady-state condition with 88F ambient air.

This delay could lead to misleading test results if not accounted for in the test senario. For example, the Canadian fleet data suggests that with colder ambient air, without preheating, our Prius takes significantly longer to reach an efficient operating temperature.



Cold air testing this winter may reveal the need for auxillary heating, in addition to pre-heating, to keep the transaxle in an efficient temperature range. If so, I'll need to rig up an exhaust pipe shroud for a heated air source and can use some of that air for the hot-air intake experiment.

One other possibility is we live near the Piedmont plateau and the road to Old Fabius is about 950 ft. above the river side road. This density altitude change is about half of what the 35C accomplishes but it would also reduce aerodynamic drag. I could repeat my steady state, MPG vs MPH tests at say 35 mph, a speed slow enough that the aerodynamic drag would be nearly insignificant. This should leave just the ICE efficiency change:


I will consider running this experiment but with better instrumentation. Thanks for the 'heads up.'

Bob Wilson