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Old 11-30-2012, 09:59 AM   #17 (permalink)
Joeggernaut
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Join Date: Nov 2012
Location: NC
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Quote:
Originally Posted by ChazInMT View Post
Uh, ya lost me here.

I was under the impression that we had a throttle body which limited the amount air which would be let into the intake manifold, thus, a manifold vacuum, the amount of energy required to pull the air past the throttle plate is where the loss occurred. It takes power to draw in the air, the power comes from the engines, thus a loss. You can't tell me it is an effortless process to draw air across the throttle plate.

Your love affair with valve management systems is misplaced in my estimation, you have seriously confused 2 different processes going on in the engine.

Also, you claim hydrogen is present in the air due to the humidity that is "Always there". Here in the north, when temps drop low to freezing, there is very little to no water vapor in the air, at its most it's 4% with 2% being common on warm summer days most places. Understand however, this vapor does NOT contribute elemental hydrogen to the combustion equation since it is already attached to oxygen thus being water. It will be a factor on a small scale in its ability to remove heat & such, but the effect is tiny, and unless you're running a top fuel dragster, really isn't worth discussing.

Anyone else wanna talk these points through?
Older cars do have a throttle plate but these cars with these new infinite variable valve technologies are able to omit the throttle plate completely. Now when a driver pushes the accelerator the ECU tells the valves what to do and controls air flow this way. The air flow is control actually by the engine valves and not a throttle plate (talk about no control over engine input, the ECU is doing everything these days for the driver). There is no longer the restriction of a throttle plate which accounts for almost all of the throttle losses in a typical engine due to back pressure.

So maybe you are thinking there is still some throttle loss due to valves being closed when air is trying to enter the engine, but the ECU can time the valves precisely to open at the exact moment to minimize this effect. There might be a 1-2% of blockage which is why I say it is 99% efficient in eliminating throttle losses. Toyota seems to have the best design in terms of simplicity and weight of the system.

Here is a direct quote from an article someone posted, you can find this same information on other sites also:
"Moreover, car makers can make use of CVVL to regulate engine output, thus eliminate the need of throttle butterfly and reduce so called “pumping loss”"


You are correct about humidity but there is a small factor involved but not worth really mentioning on passenger cars but he asked so I provided.

Last edited by Joeggernaut; 11-30-2012 at 10:09 AM..
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