I very slightly bent the tab to get them just a *bit* more open so they open fully now, but the butterfly is not completely flat... Due to the fatness of the shaft, they can be still at a small angle but be functionally fully open... hard to explain... If I eyeball mine, they are as open as they need to be because making them open that last few degrees doesn't increase the area because of the shaft which takes up some room in there...

Brian

 

Well the valves themselves will always create more turbulence if they are at an angle. I believe the shape of the shaft is fairly insignificant on the air flow.

The asymetric opening "issue" I believe is not an issue if the car is tuned for it. Mazda's rationale most likely revolved around low-end torque.

 

I think they had a problem with just the massive influx of air. That much change in air is hard to control. It would demand alot of fuel fast and the engine's rpm to match.

That and not everyone want's a higly sensitive gas pedal.


Throttle response should be alot more sensitve too. I almost never use more than 1/4 of my gas pedal on my FC. If i do i'm boosting.

1/2 of an inch is a big big difference on the pedal.

If you want better throttle response and control it might be worth persuing but your driving habits become more refined and takes a bit.

 

My mechanic said in order to get the sec plates to delay opening and both sets to lay flat open at the same time . The flat rod that connects the two linkages ( the one with a small hole and bushing on each end ) needs to be made a little bit longer on some throttle bodies . He has made them with small brass bushings .

 

Clayne---You didnt want to bore them out at all while you were in there?

 

jt,

I'll probably do it later.. Didn't have the equipment to do it at the time.

 

Okay, so guys, the issue I'm having with funky surging between 1300 and 1500 rpm has nothing to do with this TB mod so I'm going to start a new thread in the PFC forum (if you want to follow the troubleshooting).

 

As I said I was successful in getting a staged system and fully opening secondaries, I did it just changing the leverage layout, not lenghtening the rod, this has the same effect of bending the pin, as others did.
The problem is that the secondaries feed the section of the manifold were fuel is supplied by secondaries injectors, if you don't match air and fuel you'd get that hesitation I have (or at least, I think)

 

The manifold is open so all throttle plates feed all runners so you do not need to match fuel with runner with plate opening .

 

Actually it's not.

The secondary runner path is independent from the primary.




The air *will* enter the same combustion chamber, yes, but it will not be atomized properly with the same air/fuel from the primaries.

 

Ok, sorry im a little slow, what does the removing of the secondary butterflies mod do, whats good, and whats bad about it? I'd like to do this mod...

 

you are thinking of the double throttle removal, not the secondary butterflys. Look here for more info.

Updated link here

 

So if you remove the secondary butterflies that are in the intake manifold,it should run better and no problems or anything without them?

 

Please read the post right above yours...

 

I did but the link leads you to a webpage that you need a username and pass to access,so wasn that helpful

 

http://www.rotormafia.com/dtc/

 

why bother fixing the DT when you can just disable or delete it much easier?

 

The site has moved, here's the new location: http://www.rx7.org/Robinette/double_throttle.htm

 

I know this thread is old but yes your suspicion is right. Mazda intentially engineered the delay to help with the engine's torque and response in light throttle situations. Under cruising conditions, you don't want all the air flowing through both the primary and secondary ports at the same time. Doing so causes you to loose air velocity through the intake runners which in turn doesn't allow the cumbustion chamber to fill as efficiently in the low range. Less air= less bang= less torque. This is why people loose bottom end when going with ITB's.

In the Rx8 Mazda doesn't even open the secondary ports till around 3,700 rpms. The engine feeds entirely on the primary ports till then. Go drive one and see how responsive that engine is in the low range.

 

The link had nthing to do with the reply given to you. The post above yurs was pointing out the fix for taking out the slop in the secondary butterflies on the throttlebody. This has nothing to do with the double throttle plates located in the UIM.

 

Once again - this isn't the issue here. This isn't an initial delay issue - it's a full extension issue.

Examine the linkage: http://www.anodized.com/~clayne/fd3s/tb/tb.01.jpg

It's not a symmetric arc. Anyways, I completely forgot about this thread and was surprised to even see it come up again.

 

I understand that. The point of my explanation was to help educate people in general as to why Mazda engineered the TB the way they did. You claimed "the FD secondary throttle plate linkage will develop excessive play and runout in the dowel-pins and linkage arms present on the throttle body. This obviously steals air volume by increasing the throttle restriction". This wear has nothing to do with the delay of the secondary throttle plates as Mazda purposely designed the TB this way in the 1st place. 2nd gens, 3rd gens, and even the 20b TB's all have this delay and does effect secondary throttle opening. Even brand new TB's are going to have secondaried that wont fully extend. I replied to clarify the engineering intent. There are other ways of modifying that componet without removing the linkage and hurting your bottom end/light throttle response.

 

Check again. Broken link.

Dave

 

Bringing this back from the dead but in case you haven't figured it out already.... The Primary and secondary Throttles ARE supposed to open at the same time but the AUX throttles (the ones in the Upper inlet) are controlled by the EMS and when Cruising stay shut to give the off boost Torque and better MPG etc you get when the engine uses only the Primary inlet with there different Port Timing and smaller runners.

The problem is every one thinks there some sort of Cold start thing and removes them to get another 1hp from there Peak but loosing more Off boost Torque making it more of a PITA to drive around town..... but if they had checked first they would see the AUX throttles are Closed when the engine is hot as well as cold (don't forget the AUX throttles are open when the engine is OFF and the engines Vac shuts them not the other way round and its opened Via a EMS controlled Solenoid)

 

Wow, bumping a thread from the dead to make a point!

Actually, you're incorrect there. I T'd my boost gauge into the vacuum line to the secondary throttle plates many moons ago. It showed full vacuum (plates closed) with the car stone cold, and once I hit around 50 deg. C it showed atmospheric pressure (plates open).

Once they were open, they STAYED OPEN. They never closed under certain circumstances or anything.

The ONLY purpose of those plates is to keep you from going WOT when the car is stone cold. That's it. Took mine, out, have noticed no difference in the driveability of the car.

As to the original topic of the thread, I do remember the FC's had a spec in the shop manual where the primary throttle plate opens first, then the secondary plate opens at a certain throttle position past that. I'm not sure if the FD does the same thing. I'm also not certain that bending that tab will really make that much of a difference - are you going from 98% full open to 100%? Does it make that big of a difference in airflow or power? Does it REALLY stay at 98%, or does the rush of air over the plates push it fully open?

Mucking around with the throttle body can be tricky, you can easily turn it into a non-driveable mess. This is not a magic fix or a magic "unlock 50hp!" measure.

Dale