brownmound

I am rebuilding my intake right now, and I noticed that one of the shafts that goes through the intake and links the actuator to the 5th/6th port sleeve has some movement in it.

It can best be descibed as an "out of plan" bending, ie you can push on the shaft with your finger and it will give to one side of the intake hole a bit.

It's torsional strength seems fine and strong...this to me seems of most importance since these shafts only see rotational movement, as they turn the sleeves.

So should I worry about it? The shafts seem to be a two-piece design, linked by some mechanical means and then covered with some sort of hard plastic wrap. Those of you that have taken them apart know what I am talking about.

I am wondering why Mazda designed them this way, in two pieces, and two, if I should get a replacement why it's convenient to do so (I'm sure that part is expensive, though.)

Any thoughts?

Right on.

Nick-7

I just got through rebuilding my intake manifold and the ends of my actuator rods were bent ( were they connect to the actuator) I tried to bend them back, but it didn't help much. Mine work good. Do yours rotate freely? To help lubricate mine I used MMO on them and it seems to work real well.
Did you find carbon in your intake manifold? The one with the four tubes.

j9fd3s

iTrader: (3)

i'm not sure why the need to flex, but the fc ones acutally do have a more flexible thing in the middle. and yes you can buy the shafts seperatly

mike

brownmound

I just called Pineapple and spoke to Joel there. He looked at one he had on hand and said it was flexing too. I figure as long as it's got it's torsional strength and shows no signs of falling into two pieces, it should be fine.

I'm sure the shaft is at least $30 from Mazda. I wonder why they engineered it to be flexible? Maybe so it won't bind in there? Dunno.

Right on.

Suparslinc

Thats what I was thinking. When I rebuilt the intake on my FC I noticed the spring load. Its probably to keep a buffer against sudden changes in vacuum/kinks/etc. I dunno.

FJ

That was, recently, a question for me also.

I have my shafts and port valves removed at the moment. (Easy enough when the engine is being removed.)

The last time I removed the intake to clean the aux port valves and the injectors (about 5 years ago) I saw the same as I had on previous occasions: the shafts were solid and the black plastic in the middle of the shaft, was (somewhat) flexible.

(I've read on the 2nd Gen forum that there is a spring inside, covered with the hard plastic.(And someone mentioned it recently here. But I haven't a clue as to the function of the plastic..))

This time when I cleaned them, however, there are cracks. Small cracks, in the hard plastic which you've mentioned.

I know what you mean, regarding the torsional strength, and mine are fine also. But if the tips of the buggers were to crack and fall off, it gets inhaled into the engine. No need to mention that that's not good news....

I've ordered a couple of them.
Price-wise, it's not bad at all: under $100.00 CDN for both shafts.

John.

brownmound

Cool, you understand exactly what I am talking about then. The torsional strength is rock solid. The flexing is mild enough to where I feel about 97% comfortable reusing the shaft. I suppose if it fell off it MIGHT be able to fit into the intake port. It can fit there, but it would have to pass the pin in the sleeve, and then negotiate the sleeve with the Pineapple inserts...maybe I'll do a mockup with a similar sized piece of pencil or something. It just looks sold enough to where it's not breaking anytime soon.

I think it was more solid until I rested the intake with the shaft poking out and it put a bending stress on the thing. I was trying to be careful of that too!

Well I'll do the mockup and if I don't feel comfortable with it I'll order another, I need to order some new banjo bolts for the little air tube anyways.

right on.

brownmound

I inquired about these from my Mazda dude today. He said not only do they only sell one of the shafts for the SE, but also that they don't come with the plastic piece on them He did mention the spring. He said that the plastic piece might actually be carbon buildup. I said, no, it looks plastic to me....maybe it is actually years of built up carbon smoothed out by the air flow? I don't know.

Right on.

LongDuck

3 months ago when I removed my upper and lower intake system, I noticed the same thing, 165k miles and the black plastic 'wrapper' on the flex shafts was noticably flaked off over about 20-30% of the shaft length. Only place for these scraps to go is into the engine.

Not a good thing, but didn't seem to harm it any. I chipped off as much of what looked like it was going to fall off, and lubed them up, put them back in.

It appears that the Mazda engineers designed the shafts with a rubber outside covering (much like heat-shrink tubing) in order to protect the wound spring from corrosion, likely. This allows the shaft to flex slightly, just enough to allow the head to slide a bit against the port crossbar. This helps to cut down on vibration and smooth turning of the axles during opening of the '6' ports, since any amount of drag during rotation will slow or prevent the opening of the port - we're only working with air pressure of 2-4psi here, so it's important that they move freely. HTH,

FJ

First, sorry for the repetition in my earlier post of what j9fd3s said re the 2nd gen shafts; when I had the time to reply in the evening I obviously had not hit "refresh" after viewing the thread earlier that day, and so I missed the previous replies.

I don't know why your dealer said they only sell one; I gave the part numbers to Mazda (along with many more) from the microfiche at http://www.iluvmyrx7.com/ and he ordered both, with no question. They are due to arrive next week. And the plastic is definitely built in.

I was going to wait until they arrive before playing with my old ones (in case the status changed, and they suddenly became no longer available or some such nonsense), but curiosity got the better of me. Also, it would help you decide whether to order new shafts or not.

So, I've just dissected one.
To start, I cut off the plastic. It's rather hard on the outside (soft and chewy on the inside ) but as LongDuck said, I don't see any flaking bits of plastic hurting the engine: it's not hard enough. About the same as a piece of carbon buildup from the intake that would simply be spit out.

I had expected a spring under the plastic, but wasn't sure what was inside the spring: another, softer. shaft?
I gave it a torture test: put a screwdriver in the gap that would normally engage the aux ports and a pair of pliers at the other end. Twisted back and forth, hard: nothing gave.
I bent the tip 180* backwards, so that it was parallel to the shaft: again and again in different directions. Nothing broke. It stayed a little bent, but could be "encouraged" back to near straight.
I was starting to get a little ticked off that I couldn't break them, given that I had just spent $100.00 for new ones. Seems my earlier fears of a tip breaking off and getting inhaled into the new engine were unfounded.

As I was unable to break the shaft, I was wondering what the "miracle" inner shaft could be made of; which is what provoked the use of the hacksaw. (A rather primitive tool, but all kinds of fun on occasion.)

Turns out there is no "inner shaft", nor a single spring. The outer "spring" is 6 wires wrapped around an inner layer, clockwise. The "inner" layer is another set of 6 wires, wrapped counterclockwise; wrapped around another set clockwise... and so on. Four layers, six strands each, wrapped around a center core of a few twisted wires.

Bottom line: I do not see a danger of the tips breaking off and destroying the engine, which was my initial concern when I ordered the new shafts.

If I were to put my old shafts back in (at least the one that is not now pupshit), I might remove all of the plastic. LongDuck's suggestion regarding corrosion protection makes sense, so maybe a coat of BBQ paint? Good adhesion and stands up to high temps.

I did take a couple of pics, but 35mm. I'll post it in this thread once the film is developed.
I'll be interested to see if the new shafts have a soft or a firm plastic...


As to the function of the "spring": although the ports engage rather slowly, over hundreds of RPM, I suspect the flexibility is related to the damage that would result if a solid shaft was to break from fatigue cracks, trying to open a stuck valve repeatedly. If the valve is not going to rotate, you want the shaft to absorb the torque as the actuators keep on trying to rotate them. The same reason that airplane wings flex as much as they do: if it doesn't bend, it'll break. You're in deep doo-doo in either case. Just a guess.

Right on. (Sorry, that's your line... )

I did say it was a bit long, didn't I?

-John.