Throttle plate issue/question.
07-20-12, 07:11 PM
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Throttle plate issue/question.
So I decided to begin taking measurements to fab a custom intake elbow. Upon removing the stock NA elbow I noticed that the first set of throttle plates were wide open. I noticed a vacuum line going to a pot like device attached by an arm and spring assembly. I figured that perhaps the device would close when the engine was creating a vacuum and under a certain amount of load. I reassembled the intake and started my car and had a friend rev the engine to 2000, 3500, 4000, 5500, and finally 7500. Not once during any of the rev cycle did the pot device engage. I then checked and replaced all the vacuum lines leading to and from the throttle body itself and repeated the process with the same results. Could anyone inform me as to how this devices works and a possible solution to fix it?
07-21-12, 01:30 PM
#2
Are you talking about the outer set of secondary plates (ie tertiary plates)? The diaphragms always fail after 20-25 years.
The MAZDA RX-7 86-88 technical page
The MAZDA RX-7 86-88 technical page
The number 2 secondary plates are open unless enough vacuum (200mm Hg or 7.87in Hg) is applied to the double throttle diaphragm, in which case, they are closed. Vacuum to the diaphragm comes from the intake manifold via a heat activated water thermo valve. Opening of the number 2 secondary plates is dampened by the double throttle diaphragm, in other words, if vacuum becomes low enough to make the plates open, they will open slowly.
07-22-12, 10:41 PM
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This is my daily driver and I'm not looking to do the TB mod mainly because I rarely get a change to keep my revs up high enough for the mod to be effective unless I'm hauling *** on the highway or driving in the hills and mountains. I'm more concerned with getting my low rev acceleration back.
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07-22-12, 10:43 PM
#8
You can get another working tb relatively cheap in.the classified on here or at a junkyard.
By cheap probably like 20 bucks, swapping them will be quick.and easy.
Or you can fix yours Im sure theres a thread somewhere for how to.do.it.
Are you sure they aren't just stuck? If you free them.up.they should work.
By cheap probably like 20 bucks, swapping them will be quick.and easy.
Or you can fix yours Im sure theres a thread somewhere for how to.do.it.
Are you sure they aren't just stuck? If you free them.up.they should work.
07-23-12, 12:29 PM
#9
The tertiary plates are just there to help smooth out harsh throttle input. The black/green valve before the diaphragm is a delay valve that will slowly open them if you mash the throttle. They have nothing to do with low-end torque (an NA rotary has almost none anyway). There is little torque under 3k RPM.
I don't think you can repair the diaphragm. It's sealed. The entire throttle plate assembly can be removed in about 5 minutes. Just unscrew each plate, slide the shaft out, and then find something to seal the hole. A bolt with some RTV will work.
I don't think you can repair the diaphragm. It's sealed. The entire throttle plate assembly can be removed in about 5 minutes. Just unscrew each plate, slide the shaft out, and then find something to seal the hole. A bolt with some RTV will work.
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