thunderstick

I know that in extreme cold weather, the bypass should be re-routed correctly to prevent icing conditions on the throttle blades... I have done this bypass on my engine, and so my question is, at what range of temps should it be re-routed to original configuration (no bypass)? In the cold winter months I end up covering half my radiator with cardboard (aluminum rad) so that it will heat up a little quicker, so is it really necessary to go back to no-bypass in that weather, too? I live in so. Md. and the temps get down in the teens at times...

KAM

rondubbs

lets think about this,, for the tb bypass to mess up anything, your throttle body blades have to FREEZE, unless your car is sitting outside in negative degree weather with the hood open , i dont think you have to worry about the tb bypass mod.

88IROCs

Ron,

Unless you live in the desert, there is always some ambient moisture in the air your engine takes in. And some of that moisture will make it's way past the filter. Not enough to have a drastic effect on combustion, but it is there nonetheless. When this air comes into contact with the TB, if the air temp is cooler than the TB, the moisture will condensate on the metal(warmest) portions of the TB. When you shut the engine off, any moisture remaining on the TB will cool off as the TB cools off. When the TB drops to 0C(32 F) the remaining moisture freezes. Initially the amount of moisture is small enough that it would melt soon after engine start. But if you do a number of short trips, the constant engine on/off cycles will build-up more moisture. Eventually, this build-up will inhibit the movement of the throttle-blades.

Ironically, this becomes less of a problem at very cold temperatures(-20C or colder), as there is less ambient moisture. At moderately cold temperatures(0 to -20C), during daylight hours there is significant evaporation, such that there is increased humidity, which will freeze the TB, when the engine is shut-off.

I'm pretty sure the boys at Chevrolet Engineering did thier homework on this, and doubt they would include such a feature if it had no effect or benefits.

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He who hesitates,... is lost!

[This message has been edited by 88IROCs (edited October 23, 2000).]

Grim Reaper

I have not experienced any icing problems with -10 C (about 15F) degree weather and this is in a high humidity area (Lower Mainland of BC). This is with the car left outside.

I have recently moved to Kamloops where -20C (just below 0F)is not uncommon during winter and I am not contemplating reconnecting my TB coolant bypass. I now have a underground parking which is not heated but isn't cold either. If I had to leave my car outside, I would seriously reconsider reconnecting it, but since it is inside I will not bother.

I agree with IROCS88 comments about REALLY cold weather, where moisture becomes less of a problem. That is why it seldom snows when the temperature gets below -25F. I think the real issue is the amount of humidity you experience in the area you live, temperature, and where you leave your car in the evenings. High humidity, temperature between -15F to +10F and car parked overnight outside: reconnect it.

Of course, you can experiment with it to tell others what range of temperature you operated your car with the TB bypassed. That is what I am planning to do here in Kamloops.

rondubbs

i still say leave the tb bypass intact. the engine compartment gets hot during driving,, 180-200 degrees.. i can dump a gallon of water under there and it couldnt possibly freeze. its just too hot. by the time it does get cold under there, i dont think there is any moisture left.,
these are just my thoughts

scooter

iTrader: (11)

Cold air doesnt condensate on warm parts. Warm air condensates on cool parts. Like when you take a shower the water heats the air and there is a lot of moisture and it collects on all the cool things in the bathroom, like the toilet, sink and most prevelant the MIRROR. The reason for the coolant to warm the throttle body is that moving air cools the throttle body to the point that it can begin to collect moisture and freeze while the car is running. Same principal as your air conditioning. Moving gasses transfer of energy in the form of heat. Blah Blah Blah. Granted your TB will probably never freeze but GM had to cover all bases to prevent for getting sued.

James

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If the women don't find you handsome they should at least find you handy

88IROCs

Glenn,

-20C in Kamloops,.... hmmm, how high up in the hills are ya livin'? I've been spending the past 6 Christmas's(and sometimes January) in Kamloops, and have yet to see -15. Mind ya I stay in the valley around Westsyde.

Ya gotta try livin' up here. I don't even bother to plug the car in until it gets to -30. And -40(or worse) is common during January. Man, the silly things I do to do stay employed. Ah well, it's all pensionable time.

Scooter,

You are, of course correct. Thermodynamics always screws me up. I do know on previous vehicles, which didn't have provision to warm the carb or TB, freezing throttle plates were a real problem on warm(-10C or above) winter days. No amount of effort sealing the air cleaber housing would help. But making a heat stove and connecting it to the bottom of the cleaner housing always worked like a charm.

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He who hesitates,... is lost!

[This message has been edited by 88IROCs (edited October 25, 2000).]

Grim Reaper

88IROCs, I just moved here, but around Christmas of 1996 we had a major cold snap where even the Lower Mainland hit -15C. I think Kamloops hit -25C at that time according to the locals here.

Its funny about the downtown area, it seems to be in a bit of a bubble. It is generally 2-5* warmer in the downtown than around the airport where the official weather is taken.