TII secondary THB mod (pros and cons).

[FRED]

A fellow from Aus who goes under the name BUMPSTART, added these words about the configuration of JDM turboII throttle bodies:

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later JDM still has the wax cam,, just lacks the vacuum thermoswitch and double throttle dash pot that holds off secondary operation when cold

warm,, the throttle delays work all the time ,, following behind the main throttle plate movement
and is set via the dashpot which adds drag to a black plastic bob weight

these are found on N318 updates and also on s5 n370 ,, though there is trivial differences in the two TBs and they are not exactly the same
( mainly TPS differences,, but s5 TB also requires a shorter mounting stud on the bottom of the pattern to the UIM )




early s4 t2 ( jap and aus ) have a wax cam ,, and a thermoswitch ,, and a double throttle diaphragm which allows vacuum to hold out secondary delay operation when cold

- but as above,, the secondary delay throttles always follow behind the movement of the primary throttle
they are never locked in the open position
and,, in mazda words,, is provided to prevent a lean condition during rapid acceleration

these TB's are less common,, but are obvious to ID from the added vacuum can that is working on the delay mechs

i seek these TB's out,,, clever use of the vacuum delay , hooking it to primary runner vacuum ,, amounts to boost / load demand secondaries ,, something akin to the way the secondaries work on the old nikki carb