Hot air helps keep the fuel vaporized. Though the injectors do atomize the fuel well, they do not completely vaporize it. For the best combustion and gas mileage, the fuel must be well vaporized. As the air is being sucked into the engine, it cools what would otherwise be warmed by the engine, so heating the intake manifold helps solve this problem. It is especially important to have heat when the throttle is opened significantly. High intake vacuum normally assists in vaporizing the fuel (low atmospheric pressure helps liquids boil more easily), but when the throttle is opened, the vacuum goes down, and fuel vaporizes less.


It is true that you can get better power to some degree by having a cold manifold, since colder air is denser, but mileage may go down, and the engine was designed arounda warm manifold. Being an engine capable of very acceptable acceleration, you probably already have ample power. If you need more power, you can cool the manifold, but if you''re a manufacturer, and have capabilities of fully designing an engine, you are better off achieving more power by other means.


A heated intake manifold was even more necessary in the days of carburetors. My 1951 Chevrolet performs terribly until the manifold is warm, since the fuel liquifies everytime I open the throttle to accelerate. Once the manifold is warm, throttle response is great. I can enrichen the carburetor and turn off the manifold heat riser. Power will be somewhat better, and acceleration will still be good, but fuel mileage will be awful.

 

It makes sense but seems like warming the manifold would have nominal improvement. But thanks for the info. In my case, I wish they didn''t design the intake manifold to have coolant passages in it.

 

Well I took a good hour to look all around up and down with a very bright light but could not find the source of the leak. It has to be close to the belts because when the car is on, the leak is dripping onto or around the belts because the belts are spraying the water towards the front of the car.

I''m having the system pressure tested tomorrow so I can see where its coming from without having the belts spraying the coolant. I''ll let you know what I find if anyone is interested in knowing for potential future problems.

 

OHO! -


You may actually have a water pump going bad, instead of an intake or head leak. Release the tensioner and take the drive belt off, then grasp the water pump pully with your hand and see if there is wobble (play) in the shaft ....

 

If its the water pump, then its a pretty easy fix. They''re cheap and only take a couple hours to replace for the untrained.

 

What symptoms did you have with your Saturn? Did you have bucking? while driving and shifting up the gears?... I have SW2 1999 and I had a mechanic last year take the connector off the intake and clean out alot of black "junk" with a toothbrush.... and she ran better. I have read that the gasket does crack... and wonder how much and how much time it takes to replace this gasket? I don''t want to get ripped off.... and want to make sure I don''t get ripped off..... Also... need to get an inspection sticker by next Friday and after last night (the car has been sitting still for 1 mos) I drover her today and the check engine light was OFF.... does that mean the car won''t register any codes and I should get a sticker before the light goes back on? Please advise.

 

The gasket is cheap. Doing yourself is free and not that difficult. But if you need to have a machanic do it, then you''re looking at a $400-$500 repair.