Double throttle, why?
 

What good does the double throttle do? Does it increase gas milage, lower emmissions, or give better midrange power? With so many people doing the TB mod (including me) I have to ask, why is it there?

For better driveability...
After the throttle body mod, drive at 2kRPM on the tach then suddenly go WOT - what happens?



-Ted

What does happen?

it kinda cuts off more a millasecond. i think it's from the engine being overcomed by so much air so fast. i think the other two plates we all took out gradually increased the amount of air that enterd the engine. (we all were playing with them b4 we took them out and saw they opened slowly ryte)

The double throttle (if your talking just about the front double plates) is for cold starting. You have a water thermovalve that ports vacuum to the double throttle diaphram when the engine water temp is below 60 degrees centigrade. That closes them. When the water temp is above 60 degress the vacuum from the water thermo valve is lost to the double throttle diaphram which in turn means the two plates are spring loaded to the open position. They are spring loaded open all the time from that point. I suppose the *throttle body modification* is done to remove the obstruction of the plates and shaft for better air flow. Got me.

Their only function is to keep the uneducated newbe from WOT on a cold motor.

There are two functions of the double-throttle.
The cold start thermo-wax prevents these plates from opening when it's cold.&nbsp Thus the car makes very little power when cold.

When fully warm, these plates are "damped" so the open very progressively when you slam open the throttle.&nbsp This prevents unwanted hesitations from 1) losing intake velocity due to the throttle plates opening up suddenly, and 2) abrupt changes in AFR which the stock ECU cannot compensate for...



-Ted

Ted, or anybody that knows, just how does this dampening happen?? I've a 87 n/a that has a broken double throttle diaphram (burnt during the previous owners pd fire), so I've never seen one in action. The thing is spring loaded open. Its got a diaphram that is vacuum operated. The vacuum passes thru a delay valve. The vacuum originates at the water thermo valve. If you look at the attached jpg, you see that when cold, the vacuum does go to the double throttle diaphram. When the car is warm, the vacuum it would appear, vent to atmosphere(well mabe vent is the wrong word). So if thats the case, how does this double throttle modulate????? If the vacuum is venting, why would it do anything but open wide open??????? Talking N/A.