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Wingless by choice.
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Discussion Starter · #1 ·
Hey guys, just wondering, is the vtv valve required? if so, where can I buy one? I'm guessing it helps gas mileage or something to do with vacuum, I'm stumped on this one, even after searching. If required, where can I get one, and by Vtv valve I mean the round valve coming off of the dashpot. Thanks ahead guys, I'll get a pic in the morning if you don't know what im talking about. Later guys.
 

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I am pretty sure the only place you can buy it is Toyota. It couldn't be that expensive, it is just a check valve.

That part is integral to the operation of the dashpot. When you open the throttle, the dashpot plunger rises up. Since the VTV is a check valve, it lets the dashpot go up freely. When you release the throttle, the dashpot goes down very slowly because the VTV will not let the air out. That is what keeps the throttle from slamming closed, stalling the car out. Without the VTV, the dashpot is useless.
 
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why wouldnt you want the throttle to close fast?? do you think that would cause carbon build-up from unburnt fuels or something?
 

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Okay, what the dashpot definitely does is to allow the throttle plate to close slowly, rather than slamming shut. The stated reason in the manual is for emissions. I guess the jist is that you are pumping all this fuel in, then you close the throttle quickly. There is probably a brief time when you still have lots of fuel coming in, but suddenly no air. So, slowly closing the throttle will give it a little more air to make sure that fuel gets burnt.

That being said, not too many of us are concerned about little puffs of HC's in the air when we shift. People do a lot worse to their emissions systems than that. But, as many people have seen, their car will stall out when they let off the gas quickly, but not when they do it gradually. Would this happen on a brand new, healthy 7MGTE without a dashpot? I don't know. But, I do know that it will happen on many 100K+ mile 7MGTE's. And, I am sure people care about that a lot more than the emissions.

The ISC regulates RPM's, no doubt. What I don't know is what it does when you are on the gas. Does is hold its position, go closed, or go open? From my experience, I think it must go closed. With the ISC all the way closed, the engine will not be at a healthy RPM. It will fall to something like 4-500 depending on lots of factors. So, closing the throttle more slowly will allow the ISC time to react and get to the right position. Anyway, that is my theory of why the dashpot is good for preventing stalling.
 
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