Throttle Body De-Icer Thingies

How important are those coolant lines that connect to the throttle bodies in a lot of new cars?

Would the world explode if I didn't provide hot water to my intake system?

Disconnect it.

It shouldn't ice up. There's no fuel running through it.

What are they for?

They are for melting ice that may form on your throttle body causing dangerous sticking.

But I think you already knew that

Now I've never taken any fluids classes, but from my memory, changes in pressure can cause water to form as a condensate on it's surrounding environment. The pressure fluctuations around a throttle body are very real even in naturally aspirated cars.

If it ain't broke don't fix it.

There supposedly there to prevent icing (which probably wouldn't happen ever). I've had mine bypassed for 10 years with no issues.... but also no benefits.

It's true that they can ice up at above-freezing temps due to pressure drop causing water to freeze on them, which is why they're heated.

I've seen lots of posts on the internet about bypassing the throttle coolant loop for more power, but, really, how much of the air going through a throttle is in contact with it, and for how long?

[googles...]

http://forum.mazda6club.com/engine-drivetrain/132355-why-not-do-throttle-body-coolant-bypass.html

procainestart wrote: http://forum.mazda6club.com/engine-drivetrain/132355-why-not-do-throttle-body-coolant-bypass.html

I'd like to see the same thing on throttle body / intake manifold spacers. Those things make me really angry.

As long as you don't drive much in sub-freezing weather, its of no concern.

Up here in the Great White North, whenever the temp drops down into the -20 range, I wish for hot air pickups. Lots of problems on highway driven turbocharged cars, where the humidity from the crankcase breather is routed to the throttle body, or anywhere upstream of the intercooler. The intercooler will frost up internally and block airflow almost completely. Car gets slow, sucks intake hoses flat...

Or, if its a BMW, it freezes the upper half of the crankcase breather, which then applies manifold vacuum to the bottom of the oil pan. They will suck the pan dry in an X5 in less than 10 minutes, with catastrophic results.

Haven't seen a TB ice up but I have seen it happen to motorcycle carbs a couple of times. A combination of a cold damp day (doesn't have to be below freezing) and a lot of WOT operation (is there any other kind??) can do that. It's funny to have the thing run bad, pull the airboot and see frost or ice crystals blocking air jets, vents, etc.

The Celica had coolant lines through the TB. I took it all off. It's cold in Colorado. No problems so far, but I haven't put a ton of miles on it.

I think carburetors have it worse because the venturi causes a larger pressure drop.

But if I recall, some carbureted cars have a warm air intake situated near the exhaust manifold which is supposed to melt the ice. I've heard it been referred to as the 'stove'.

A lot of carbed cars have that. On some it even had a manual lever with a 'winter/summer' setting. I have heard of SU's and Strombergs icing up but have never seen it.

I was thinking of taking it off because I'd like my intake to be cold, but I'm not chasing .3 hp if it means the TB might stick.

N/A 850s (the Swedish ones) have a thermostat controlled flapper valve in the air filter box that selects between 2 different air intake sources. Fresh air from behind the grill, or hot air from a heat shield on the exhaust manifold.

The thermostat fails, and restricts the intake to the smaller "hot" side at all times, most never bother the fixing it, and instead permanently fix the valve to the cold side. I haven't heard of anyone having icing issues.

While it's not exactly the same as having coolant plumbed to the throttle body, I have a highly modified filter box on my 850, with the entire flapper assembly removed, and all intake air from the "cold" side. Has been like that for 4+ years and working on it's 2nd Ohio Winter with no issues. (knock on wood).

• Lee

Curmudgeon wrote: I have heard of SU's and Strombergs icing up but have never seen it.

don't what brand of carbs my '76 Civic had ( non CVCC) but some how the hose from the heat shield ( covering the header ) that routed to the horn of the intake/air cleaner got removed .... in wet weather ... most notably if it also was cool ... after 15 - 20 min the performance would slowly deteriorate to the point where you couldn't drive it... first couple of times this happened I pulled off the side and ( with even less knowledge than I have now) lifted the hood and poked around hoping something would pop up and say "here I am .. fix me" ... eventually I'd drop the hood and get back in the car and try it ... usually no go... I'd wait 5 min or so and try again ... viola ... away we went

finally figured out the carburetor icing thing ( credit wwII airwar books) and would just leave the hood closed and wait 5 min or so and everything was good

finally put the heat shield back on and routed a hose back to the air cleaner and never a problem again

I had a 69 Chev truck many moons ago with an aluminum intake, 600 Holley and an open air filter element. Cold, snowy weather, if I went on the highway I would have to park it with the back to the wind, engine shut off when I slowed down, or no idle. Let the heat from the engine soak up into the carb for 5 minutes, all was well.

The throttle body on my Dakota doesn't have any coolant running in it (5.9L Magnum) and it hasn't had any issues. My Dad's 92 doesn't either and he had no issues when he had it in Minnesota. No hot air inlet on the air cleaner either.

I think it may go back to the old heated manifold. I haven't owned a vehicle that had heat to the intake in years. My EGT, in below zero would sometimes ice up. Only did it twice. That was with the old flapper ( vane air flow sensor). never had a problem with a MAF.

are there fuel economy benefits to be had from this setup in the winter? one of the first things i did to my hyundai was bypass the throttle body coolant loop. Because Racecar. (Who wants their intake heated, bro!?)

Now its cold out and my mpg has been dropping again, but I am assuming mostly because of the "winter blend" of gasolines. scangauge is telling me my intake temp this morning on the way to work was 40 degres farenheit. (it was in the 20's outside)

Curmudgeon wrote: I have heard of SU's and Strombergs icing up but have never seen it.

They do, in fact if you have one of the larger carb spacers on, to keep the fuel from oiling in the carb in the summer, it makes the problems significantly worse.

In reply to Streetwiseguy:

My uncle had this same issue and solution with a similar vintage chevy. I've never had a problem with it on an MPFI car though even with the coolant lines bypassed.

failboat wrote: are there fuel economy benefits to be had from this setup in the winter? one of the first things i did to my hyundai was bypass the throttle body coolant loop. Because Racecar. (Who wants their intake heated, bro!?) Now its cold out and my mpg has been dropping again, but I am assuming mostly because of the "winter blend" of gasolines. scangauge is telling me my intake temp this morning on the way to work was 40 degres farenheit. (it was in the 20's outside)

ecomodders often run warm air intakes

their reasoning is that with warmer air, less oxygen is packed into the same volume. thus you must use a larger throttle opening to produce the same power. a larger throttle opening means less pumping losses.

I don't know if I buy it, but they seem to

In reply to Taiden:

I'm not sure I buy that either. Pumping power is proportional to the volumetric flow rate times the pressure differential. If you assume that you want the same power (warm intake vs cold intake) then you'll need a higher volumetric flow with the warm intake, but you'll get a lower pressure differential by having the TB open further. I think those competing effects cancel out and you end up requiring the same amount of pumping power per bhp in either case.

I'm sure gasoline atomizes better in a warm intake charge though. I don't know. I wish I could see side by side quantitative testing.

If it worked that well, I'm sure car companies would come up with some kind of warm air diverter for light load situations.

Carb ice can occur with the air temperature in the 60's. What about a valve on the line going to the intake? Open it if you get iced up.