[Silver BLT]

Speaking to my son who was looking at the 968 motor and comparing it to his M3. He suggested disableing or bypassing the heating hoses to the throttle body.

We have 3 hoses to the TB, which does what? and is it necessary to run hot radiator fluid through the TB? His thinking is any heat from the liquid would heat soak the TB thereby heating the air passing thru the TB. Heated air works against producing HP and promotes pre-detonation.

Lookin' for performance and cooler temps.

Ron



I know about the lower temp. fan switch. Is there a lower temp. Thermostat? Do we use it?

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[Greimann]

In theory, cool air does make more power, but in actual practice, the heated throttle body can only contribute a very small temperature increase. Maybe a fraction of a degree or single digits. This is just a SWAG , but look at the surface area of the throttle body vs the volume and speed of the air. If it were a heat exchanger, it would be very inefficient.



The two outer hoses are the water and the center hose is a crankcase vent.



I don't think too many people use a low temp thermostat. Not really necessary.



The lower temp fan switch does work well to keep the temperature stable and close to the thermostat temp.



If you are looking for a good power boost, get the RacerX ship from Speed 6

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[Lim Yong]

Just wondering if the crankcase vent's gas would be hotter than the coolant temp?



Is the crankcse vent necessary? I vaguely remember (could be wrong) my 944 had

a vent hose from the the timing/balance belts covers to the throttle body?

thanks <img src="/forum/images/smilies/968/rolleyes.gif" class="smilie" alt="" />

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[Greimann]

There is no benefit to power by fiddling with the crank case vent line. Sometimes the kids put gauze breathers on them and get oil vapor all over the place. Causes a real mess.

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[flash]

i did the bypass - while i haven't reconnected it to verify it, i could swear that my coolant temp went up just a snitch, but i can't be sure (probably just due to the decrease in volume, and the absense of the cold air cooling the coolant in there) - it's still very stable and low though, using the low temp fan switch - i noticed no discernable power gains, as i am sure that the amount of change is minimal - i'm sure that the air is a bit cooler, but the difference is so small, my butt-o-meter can't tell



do not install the low temp thermostat - this is a common mistake - it will cause the system to fluctuate too much - it results in too early a saturation of the coolant - the goal in a system is to create a stable temp, limiting the variance in running temps - you also want to be running 5-15 degrees above your thermostat point, or 100 degrees over ambient, whichever is higher (obviously staying below pressure corrected boinling points) - the low temp switch is just the ticket



something to check - coolant reservoir cap - make sure the pressure seal is good - it has a direct effect on the ability of the system to cool the engine

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[George]

Your really don't want a 'cold' running engine. This is a common misconception. Modern engines are designed to run most effeciently at an operating temperature of about 200-210 degrees F. If they run too hot then the lubricant breaks down and parts are stressed too much. If they run too cold, then too much of the energy of combustion is turned into heat loss because of the difference in temperature gradient between the combusted gases and the surrounding engine parts. Flash is right about the stable temp also. You don't want fluctuations in engine temperature. You want the engine to startup and reach ideal operating temperature quickly and then remain stable during use.



You do want a cold charge of combustion gases going into the cylinders because they will be denser and therefore give you more power.



Warm engine and cold intake gases - that's what you want for maximum power, efficiency and engine life.

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[Greimann]

Good input.



One thing I think we also failed to mention, as part of the original question, is the purpose of the heated throttle body is to prevent icing in weather conditions that could cause it. A throttle stuck open due to ice would be a unpleasent surprise at the end of the offramp. This icing could happen at ambient temps above freezing because of the cooling effect of the pressure drop at the TB.

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