Second2none

ok so i was diddle daddling with the idea of mech secondaries, trying to figure out the best way to go about it. tieing a twist tie thing around 2 things seemed a little... unreliable. so i noticed that theres a 2 plates on the secondar shaft one that has a bar that goes to the primarys, well i noticed that that bar doesnt pull anything on the secondars till its about 1/4 opened on the primarys. then it starts to move the plate on the secondary shaft. if you look closly you'll notice that this plate moves freely, but it touches one that moves the secondarys. so i went and drilled 2 holes in both those plates, and bent a finishing nail with a large head to twist and turn and wrap through these holes...

now you got a slick strong connection that doesnt look like you used your garbage bag spare ties to hold it togeather.

btw im very bad at explaining things. but if you look youll know exactly what i mean. will post pics later today.


-Rob

Rx7carl

Yea, that works. I use SS saftey wire to do mine. Lasts forever. Ive also seen people braze the 2 arms together.

Second2none

yeah i was thinking about brazing them, but i made do with what i had. i couldnt remmeber how the how to someone wrote up asid to do it and didnt feel like going back to read it so i just posted how i did it

82transam

iTrader: (18)

I have mechanics wire holding mine. I just reconnected my vaccum assist (on inittabs suggestion) yesterday, and man what a difference, much smoother and still all the advantages of the mechanical. for anyone who has just mechanical on there, put the vaccum back on to help it, it makes it much more usable IMO

Sterling

Huh?

inittab

yup! The transition to opening the secondaries isn't nearly as abrupt with the vacuum still attached. You can still bog it down if your not careful but it does make the car(b) far more streetable. Give it a shot!

Sterling

People think they can stomp on the pedal and the engine will instantly make power that isn't there, defying all of Newton's rudimentary laws of physics, as well as the very well known general understanding of the FACT that the rotary engine has very little torque under 5800 rpms.

If you cannot excercise the restraint necessary not to choke the **** out of your engine by stomping on the pedal and expecting a miracal, then what you need is a full vacuum secondary carb and dare I say an automatic transmission.

Getting the most from your mech. sec.s requires as much attention to how you operate the accelerator pedal as how you shift. In both cases, for optimum performance, you are constantly running the engine on the cusp of "too hard".

If the linkage is wired together, then the vacuum box is certainly not going to have an effect. I think perhaps the theory is supposed to be that the diaphragm has to push air through the circuit and so this causes some resistance...just enough, apparently, to make a difference?
I think either it's all in yer head, or you never bothered to plug the diaphragm circuit hole when you removed the box in the first place.
But as long as the linkage is wired together, that box isn't making a bit of difference. Even if it's filled with heavyweight oil, the motion of the lever is too small to be hanging your foot up.

inittab

sort of. Instead of causing resistance, the vacuum helps "pull" the secondaries open so it doesn't take as much initial foot pressure to get 'em to open. The result is smoother throttle response when engaging the secondaries.

It works I tell ya....

82transam

iTrader: (18)

yea it definatly works. Its not in my head as you seem to think. and whats so confusing about my previous post? All I said was that having both vaccum and mechanical working your secondaries gives you the control of mechanic with the smoothness of teh vaccum.

Rx7carl

Sorry but Its all in your head. If its mechanically linked, it will open with foot pressure, regradless of the vacuum box. Study the linkage and you'll se that what your proposing is physically impossible.

YapaKanichi

my friend used a paper clip

inittab

whateva

Sterling

Bob I gotta Sterling Carb with stripes on it just for you. (-and a sticker, too!)
Gauranteed 5 more HP.

82transam

iTrader: (18)

ok, sterling and carl, you both know more than me and I respect your opinions greatly, but I know what I feel, and this is not in my head. and can I have a carb with racing stripes on it too? that would be sweet

Sterling

Well, you know best.
Can you walk me through just exactly what happens with this great improvement so that I may gain an understanding of how the Nikki linkage really works?

Bob Holton

I am going too take the nikki off the parts car, just so I can see what you guys are talking about. Hope you know what we are doing! screw it up and I will send it to sterling, he is the wize one. Bob

inittab

ah.... I see that you've reached a point in your Nikki career where you can't imagine learning anything new from others. That's too bad .....

Answer me this:

Why is it absolutely necessary to disconnect the vacuum mechanism in order to wire it up for mechanical secondaries. In other words, why is it, in Carl's words, "physically impossible" to have them both?


I can tell you from experience that leaving the vacuum box attached with the mechanical secondaries makes the transition into the secondaries smoother. The throttle pedal resistance is much more consistant throughout it's range without any abrupt mid-point hard spots when you get into the secondaries.

Sterling

Well now, Bob, you're starting to **** me off with statements like this.
That's not very nice.

I pride myself on my ability to continue to learn about the things that interest me. Furthermore, to ever suggest that you've learned all there is to know about something is, at best, a demonstration of having your head up your ***- lodged there, having been too overinflated by your own ego to remove it without the assistance of being humbled.

Firstly, I asked you to walk me through how it works.
You are responding by challenging me to prove it does not.

Secondly, it is not necessary to disconnect the vacuum box if you are wiring the secondaries together, though you do chance perfing the diaphragm...or at the very least, stretching it.

Thirdly, Carl's words were not that it was "physically impossible to have them both"; he said what you were proposing was "physically impossible".

THIS is what I am asking you to explain to me.
Explain to me how you propose that the secondary box "makes the transition into the secondaries smoother", as well as just how the "pedal resistance is much more consistant throughout it's range without any abrupt mid-point hard spots when you get into the secondaries".

inittab

I don't mean to **** you off Sterling, I was just trying to catch your attention on a subject I think is important.

And it worked


Well, do you at least agree that when you wire up the secondaries that there is a noticable if not significant resistance with your right foot when you start to engage them? I've done this with a few different 1st gens and that's been my experience with each of 'em. In all cases I removed the linkage that came from the v-box. Then one day, for some unknown reason, I decided to hook my v-box linkage back up and to my surprise that "hump of resistance" almost went away. It seems that the v-box provided just enough resistance or assistance to make the transition into the secondaries smoother. As a result I find that the carb is easier to control with mechanical secondaries. I can't explain it any other way. I suggest that you try it to see for yourself.

82transam

iTrader: (18)

ok, I'm no expert, but I'll give my theory on why it smooths it out. In totally stock form the vaccum will open the secondaries at like 3/4 throttle (there abouts)all the way up to WOT, right? With the mechanical it opens when you want it too, and while you can make it pretty smooth with practice, if you don't get it just right it will want to buck and jerk a little. Now seeing as you (me at least) don't hit the throttle hard enough for the secondaries to open (mechanically) until around the spot on the throttle that the vaccum would open them your effectively getting both the vaccum box and the wire tie opening the secondaries. So the secondaries open the amount you want via the mechanical and smoothly because the vaccum acts in a such a manner.
Ok, having just read that over it seems confusing. I'm gonna post it anyway and see if that helps. And really, to everyone (me too) theres no need to get upity about this. Hopefully I explained it good enough.

Sterling

Uhmmm, I think that you guys are smoking crack when you get together.
Or maybe it's that NJ water...I dunno.

The linkage hardwired operates as is regardless of the box.
The primaries open to about 45*+/-, and then the tab on a piece of linkage on the secondary shaft catches the spring release tab on the secondary shaft.
-But since the rest of the linkage on that shaft is wired up, the shaft opens.

The primaries and the secondaries are timed in this manor, so that they are finished opening at WOT (straight up and down) at exactly the same point, same time, whatever.
This never changes.

Now. The RATE at which the throttle plates are opened is determined solely by how fast you put your foot down.

The RESISTANCE offered to your foot is found in TWO PLACES, without the vac. box; The main throttle return spring, AND the secondary throttle shaft return spring.

When we build a Sterling Carb, we are often told that the purchaser has already decided he'll never put the Vac. sec.s back in. But we choose to LEAVE that secondary throttle shaft return spring on there not only incase fuel prices spike to 3 bucks, but MOSTLY because the driver can tell when the secondaries are being opened!
This is VERY IMPORTANT when trying to dial the damn thing in!

You guys seem to have difficulty with that additional spring tension. I find it very reassuring to know just exactly the position of the throttle just by feel.
That's simply a matter of choice.

You are adding TWO MORE elements to the resistance of the secondary throttle shaft, and they are;
The vac. box spring, and the diaphragm inside the box.

The resistance that the vac. box spring offers is NILL, but even if it were more than negligible, it would only serve to strengthen the resistance found in the secondary shaft.

The diaphragm in the vac. box, in the extremes of theory, could offer either resistance, or lessen resistance, depending on the vacuum present in the primary venturi.
But the vacuum present in the primary venturi changes immediately when the secondaries are opened. In fact, it drops substantially, which is why vacuum secondaries are rarely ever open fully, unless you have a super light spring pushing against the diaphragm.

So, I THINK that you are basically suggesting that the vacuum that is present in the primary front venturi is SO STRONG, that not only is it overcoming the spring tension of the vac. box spring, but ALSO overcoming the tension of the very strong wrap-around secondary throttle shaft spring, making the "transition" from partially opened primaries, to partially opened primaries and secondaries, easier...seamless, or as if you had removed the wrap-around secondary throttle shaft return spring.

And I say, that the vacuum present in the vac. sec.s circuit pulling on that diaphragm is NOWHERE NEAR strong enough to help pull that wrap around secondary throttle shaft spring. AT ALL!
Even if it was strong enough to do so, as soon as the secondaries began to open, the vacuum present in that circuit would begin to drop, and the whole thing would NEGATE ITSELF.

That is how I think 82transam thinks it works.

Now on to how I think Inittab thinks it works;

The diaphragm has to push air out of the circuit, thus offering a resistance to the portion of the throttle opening that it would affect...the secondary throttle shaft.

And I say that if you can tell THAT difference with your FOOT, then I want to hire your ***...as my personal dynamometer!

Furthermore, you would have to ROMP SO HARD AND FAST on the pedal for a resistance to be created, that I would simply HAVE to say to you that you have no clue how to drive a carb with mechanical secondaries.

Now, of course, I know that's not the case.
But I do have to suggest that you rethink the mechanical aspect fully of what you are suggesting to us, and contemplate the very real possibility that you may actually be mistaken in the result you experienced after having done this.

If you are that SUPER-CERTAIN that you absolutely feel a difference, then I must suggest that your vac. box linkage is binding, and you're not opening to WOT, and you are perceiving this incorrectly as a noticeable change in the transition between primary circuit and full main circuit operation.
Another possibility, which I mentioned early on, but was never addressed, is that you neglected to plug the vacuum hole when you removed the box, and a vacuum leak was created.
Having never done this, and therefore not experienced this first hand, I can barely speculate how that would affect operation.

82transam

iTrader: (18)

I drink nothing but Coke, so it can't be the water, and the crack around here is too expensive for me
As for the matter at hand, like I said I'm far from an expert, especially on carbs (the final frontier on my project car you could say) so why it does what it does is mere theory for me. but it definatly makes the transition smoother, much smoother. Although you may be right in saying that they aren't opening all the way, as I have no way of confirming that. All I know is that it makes the transition notably smoother.
oh, and as for the vaccum leak thing, I never removed the box when I first went mechanical, just removed the linkage and let it sit there.
I guess the only way to prove it to you is to let you try it at rotorfest, you are going aren't you