HAILERS

It being a slow day, can anyone elaborate on the throttle body mod and the remarks I have read about how *the secondary throttles open fully the instant you push the pedal, instead of the the first set of throttles opening slowly*????? If you have a warmed up engine, don't the two sets of secondary plates open at the same time? Did the last time I looked. Where did I go wrong?

SureShot

My lower and upper throttle plates all open together. The secondaries were just to keep newbees from WOT on a cold motor. (But you already knew that.)

NZConvertible

That was my comment!
The downstream throttles (the ones directly below the single primary throttle) are mechanically actuated. They start to open a little later than the primary one, but all three reach WOT together no matter how fast you push the accelerator pedal. This is a common arrangement on lots of old carbs. The upstream secondary throttles (the ones on their own) are operated by a linkage and a damper that slows their response. So if you slam the pedal down, they don’t snap open like the others, but open slowly. It takes a bit less than a second I think.
The reason for this is to stop unmetered changes in airflow due to the sudden pressure drop in the plenum that the ECU would not be able to keep up with. You’d get a very brief lean condition before the AFM starts measuring the correct airflow. That’s the theory, but in practice its not that bad. Manufacturers just like to build very smooth cars. Removing these extra secondary throttles improves throttle response because you get full throttle when you ask for it, not a second later.
BTW, Mazda have used this three-barrel, five-blade TB arrangement on every single EFI rotary they’ve made, starting with the 1982 12A Turbo and continuing to this day.

HAILERS

Well NZ, you almost turned the light bulb on in my head, but before it lit up, the little voice in my head said *WAIT A DARN MINUTE HERE!* What damper is NZ talking about????? There's a diaphram there, and I think its called a double throttle valve(could be wrong), and the way I look at it, is that it only comes into play when the car is cold and a vacuum goes to that diaphram, to keep those front two closed. But when the car heats up that diaphram should be out of the picture. Right???

And then I, and others have looked at the check valve b/t the diaphram and the water thermo valve and said *HEY, WON'T THAT CHECK VALVE KEEP THE DOUBLE THROTTLE DIAPHRAM ENGAGED ALL THE TIME????????

Is that diaphram the *damper* you refer to???? Or is it something else. I usually think about this outfit for a while and come to the same conclusion SURESHOT comes to. Its only for cold weather. But sure enough someone comes along once in a while and repeats the slow to open secondary throttle(I realize wer'e talking about the upstream set).

So pretend your talking to a seven year old, and try to explain where I'm going wrong. Please. Thank you.

HAILERS

Oh darn and shucks! I'm dumb as a rock. I've held this throttle body in my hand numerous times, but never really looked at it. The damper you speak of is just similar to the dashpot. Right. Well this ones tit is broken or won't extend. Thats why I didn't understand the Slow to open remarks. This sucker might as well not exist. No titty. If this is the damper, you've opened my eyes. Its located just inboard of the diaphram. Right???? So I reckon I've got the throttle body mod Southern style!

NZConvertible

Yeah, I shoulda said dashpot instead of damper. But you figured it out anyway!
And yes, those throttles won’t work until the engine’s warmed up. Good idiot-proofing my Mazda. I must admit I’m not 100% on how it all works; I just know what happens. I had this set-up on my 12AT, so I know how that one works, but the FC one is a lot more complicated because of the anti-idiot feature. One day I’ll pull the TB off and stare at it for a few hours to get it all straight in my head!

HAILERS

Frankly speaking, DASHPOT, when I hear or see the word, is meaningless to me. Might as well say dunkeltree as dashpot. Now damper, that word has meaning. You hear the word, see the word, and it conjures up visions of something being dampened. Dashpot??? A petunia in a pot on the dash????? Later. I've got to find me a working damper to put on my throttle body. Neither the engine in the car or the spare engine has a working one. Wonder what the car drives like with one in place. Oh. The vacuum line has been disconnected from the water thermo for a while now. Its functional though.

NZConvertible

Why not put your dunkeltree in the pot on your dash?

HAILERS

Is there anybody out there who has done the throttle body mod that wants to make big bucks selling me their damper or dashpot the controls the rate that the secondary throttle plates close????? Must be in good condition. No broken nipples or pushrods, please.

rexman13b

iTrader: (7)

I just did the TB mod on my T11, and I still have all the extra parts, if you want them PM me with an offer. Everything looks to be intact.

SureShot

Formula for bigger tailpipe flames: Set the throttle damper out an extra 3mm, so when you lift, the throttle is held off idle for a second and the TPS tells the ECU to keep firing the injectors.. (fooom) woo woo!
Bill

Scott 89t2

but then the throttle is open for another sec too... the best is to get rid of the dashpot and make them close instantly. there is already a bit of extra fuel coming out. what you what to do is stop the air flow as soon as possible.