Why did they run coolant around the throttle body?

[tb3]

I hope this isn't a really dumb question. I've went through some of the differant forums on this site to see if I could learn anything about why there is coolant lines plumbed to the intake manifolds around the throttle body but I can't really find anything on it. Is this just a emisions thing? And I've heard my gn would run better if those lines where capped off?

 

[VadersV6]

Well heating it up doesnt serve any purpose but to reduce condensation, which could cause rust, and even freezing up of the throttle blade shaft in freezing weather. Dont know if thats why, but I just made it up and it sounds good.

 

[jhanson1750]

The original intent is to decrease the time it takes to bring the engine up to operating temp by heating the incoming air charge and keeping it preheated to reduce the emmisions output. At least that was how it was explained to me, BUT, I fully reserve the right to be completely WRONG at any time....

 

[Rodney87GN]

and even freezing up of the throttle blade shaft in freezing weather.

I'm willing to say that is most correct because that was the main reason GM did the same thing with the throttle bodies on the TPI 3rd gen F-bodies (as well as the 4th gen LT1s)

I read that GM actually iced the throttle bodies on the TPI during testing to simulate freezing weather.

 

[83ttypecooled]

Hi,
Yes, I think throttle body iceing is what the engineers are worried about. There are other considerations, maybe.Emissions may have played it's part. Ford even heats it's PCV charge on trucks and such.Who knows for sure. Any of you GM engine guys listening?

 

[VinsGN]

Unless you are going to drive in the winter bypass the hard coolant line out puts and cap off the TB fittings. Not really a peformance mod but supports the theory of a cooler air charge.

 

[geiman]

In humid weather with the temps near freezing, without a heated TB or a heat stove on the exhaust manifold, you will ice up the throttle body.

 

[Ormand]

In cold humid weather you can ice up a carburetor- but that's at least partly because of the cooling effect of the venturis and the evaporating fuel. In a dry system, like the port injection Buicks, with no venturi, I think freezing of the throttle body is not very likely. My Buick has a centrifugal charge heater (aka turbo) sitting at the end of the passenger's side of the engine, and it will heat the air going to the throttle body WAY before the coolant gets warm enough to heat the throttle body. The Buick shop manual says that those hoses are there for "quicker warm up", and I agree with the shop manual.

 

[1bd87]

Old school

Being an old man and working mostly on carbs, it to stop ice build up on the butterfly on the inside . I ran a 440 tunnel ram with twin 650 holleys and took it out on a cold spring day and watched as ice formed all over the carbs and then it started affecting the idel and floding out then it would race and not idel down. This coolant is to keep ice from forming

 

[Blazer406]

Icing not a problem in MS......

 

[VadersV6]

The air spends relatively NO time in the throttle body. You need backpressure, turbulence and time (distance) to heat the air up. Warming the TB up will do nothing to increase the incoming air temps. At all. Think the radiator would do much good if it were just a big hole? No. Its there for icing.

 

[UNGN]

Do you mean there is still a GN out there with the TB coolant lines that AREN'T capped?

Someone should test how cold it would have to get for the TB to ice on a TB, but that is what they are there for.

 

[Ormand]

Its there for icing.

Aside from the fact that the shop manual says it's there for quicker warm-up, and fact that we're talking about a car with direct port fuel injection, NOT a carburetor, that might seem reasonable. I've experienced icing with carbs, but they have gasoline actually evaporating inside them, they have venturis, and mostly, they don't have turbochargers. If you look at the routing of the lines, and the coolant flow, you will see that the hot water doesn't really heat the throttle body where the butterfly is- it heats the part with the IAC. So, based on logic, and on "reverse engineering", and on reading the shop manual, I conclude that the lines are there to improve idle, by warming up the IAC more quickly.

 

[1bd87]

Lets get high tech. As air flow speeds up as in the IAC or set clearance on the throttle plate it cools down the steel even more which is already cold on a cold morning. The moisture in the air then freezes onto the IAC opening or throttle plate opening there by reducing clearance and chocking off air supply there by stalling the motor or killing it. This action is not instant and by the time it takes to cause a problem warm coolant is warming said parts. this is true from about +40 to -10 at which point very little moisture is in the air

 

[Drewster]

Hey if it it will heat air charge, it should cool also

thats right you heard it hear.... Use an Ice container and small pump to circulate cold water thru the throttle body.
Andrew

 

[1bd87]

Kids

Kids come up with the darndest things Maybe spray your intercooler with Co2
or did someone already come up with that?

 

[Ormand]

The air flow speeds up in a venturi, as in a carburetor. In the throttle body, or in the IAC, it flows around an obstruction, but the venturi effect is not nearly as strong as in the throat of a carburetor. The cooling is NOT simply from the air speed, it is from the lowering in pressure. As air flows through a venturi, the pressure lowers, and from the gas laws, the temperature must also decrease. In a carburetor, the gas is pulled into the air stream in the venturi, and the evaporation of the gasoline provides additional cooling, which can lead to icing. The choke on a carburetor is above the venturis, and further lowers the pressure, helping the fuel evaporate, and possibly increasing the cooling effect. I have had icing on a car with a carburetor. But I've never had icing at idle, only at cruise. At idle, with a carburetor, the butterflys block the venturis, and reduce the cooling effect. Since the throttle body on a car with EFI has no venturi, the cooling effect would be less. Since the fuel evaporates in the intake ports, not in the throttle body, that additional cooling has no effect on the throttle body. And when you start the engine, the coolant in the throttle body is at the same temp as the metal of the throttle body, so if you were going to get icing, you would get it right then, before the coolant starts to warm up. So, again, high tech, low tech, any kind of tech, LOGIC leads me to the conclusion that the coolant lines are there for the purpose stated in the shop manual. They help to get a quicker warm-up.

 

[Scott Atk]

pressure drop across a partially open throttle blade + humidity = throttle icing. Manual is wrong.

 

[1bd87]

Old Timer

iN ALL FAIRNESS ONCE THE TURBO SQUEESES THE AIR TO 18#S ITS ALREADY HOT AND BOY YOU GUYS HAVE A OBSTINATE STREAK IN YOU

 

[VadersV6]

If the throttle body was about 2 feet in length, and was filled with fins, which have hot fluid flowing through them, and then you make the air turbulent and shoot it through these fins, at a relatively high pressure, and at low velocity, and the temperature of these fins is hot as hell, then it would warm the air up....a little bit. But thats not what it is. Its a hole. A hole about 3 inches long. The air would have to see a restriction, and then spend time in the area before that restriction, (because a restriction would do this) before the air could be warmed up. Heat transfer on this kind of scale doesnt happen in a couple milliseconds, which is probably the amount of time it spends in the throttle body. Especially when you're dealing with a relatively small temperature differential, and the fact the coolant is usually just as cold as the engine on startup.
When you start up the motor after its been sitting in freezing weather, the coolant is cold, the throttle body is cold, and everything else. Given that the coolant isnt even flowing through the throttle body before the thermostat opens, and all the metal is heating up just as fast as the stagnant coolant, there would be NO purpose for running the hoses there. Those hoses are there so that the throttle body cools SLOWER than the rest of the engine, after you shut the motor off.
It improves startup performance and cold driving performance because THE THROTTLE BLADES AND IAC STEPPER MOTOR HAVENT SEIZED UP FROM ICE. If you allow something to cool at a very slow rate, its tendency to dew and freeze will slow way down.
Say you're driving in freezing weather. You get to work. The engine cools off very fast. At lunchtime you decide to go fire the car up and go get some food. Lucky for you, the engine idles fine because the throttle body and IAC motor have remained warm and didnt freeze. Why? because the TB is filled with coolant, and remember, coolant doesnt freeze in the temperatures we deal with.
The air does not warm up going through the throttle body. You actually believe that a turbocharger wont heat the air up right away? The PCV system will play a part in warming up the intake and throttle body, even though thats not its intended purpose.
This is so basic....