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I have just checked myself on my car (ok fitted with PFC) but when fully warm the AUX throttles are Closed on Idle and stay closed until it starts to get to 0 pressure. With the Rad fan's on if i wot it and then pull over to check the AUX throttles they have shut again.
This is the reason i raised this thread from the dead, i don't get why my Aux throttles are opening and closing as i drive it off boost low revs (hot) when every one else says they should be open all the time? surly that's so you take advantage of the Primary's smaller runners and tamer Port timing?
Even when my FD was new (June 1992), the secondary throttle never opened 100%.
It is due to a poor design in the linkage by Mazda. Some racers and I actually made a new linkage or modified the stock one. It was great for racing but caused the secondaries to open too soon for best street driving if the vacuum secondaries were removed.
Instead of bending the tab to engage sooner, I made a new piece out of aluminum that did the same but because the piece was thicker.
Warning: Do not perform this modification without confirming that that your secondary butterfly is opening up AFTER the primary butterfly. I bent the tab like described in this article and the linkage had no slack in it anymore, which seemed good. But, my secondary butterfly was opening at the exact same time as the primary butterfly. This was creating all sorts of issues with throttle response, back fires, and just poor revving issues.
I lost so much time, money, and energy thinking my throttle/revving issues were due to tuning. After bending the tab back to place, the engine runs amazing. Also, what compounded the problem was the vacuum nipple I had my MAP sensor connected to, which made the issue of the secondary butterfly opening up at the same time as the primary (from this original post), much worse.
Mazda has a defined spec as seen below:
If you bend the tab, make sure the the secondary opens up after the primary and that the primary is open 1.1 to 1.7mm the moment the secondaries start to move.
I seriously don't think this mod is worth it. You do have to be careful with playing with any of the adjustments on the TB, it's easy to screw it up bad. I don't believe this will gain any major power or enough to be worth goofing with.
