Okay, I 've done some searching, and have read up about the dieing of the 13b after a cone filter install.... I've done the cone thing, and I've noticed that if the Air Flow Meter is positioned wrong, then it doesn't read air properly... is this akin to the nissan 300zx's? with those the didn't work right unless they were almost perfectly level.... And if this is the case, what is the proper position for the AFM to work at it's peak? I get mild hesitation at approx 5800 and then it won't climb past approx 7850.... but i can kinda play w/ it and make it break 8..... kinda odd... any idears?

 

It is to be level. If its an S4 it should also be in the right(up/down) position.

Santiago

 

You can rotate it 180 degrees, but that's it. Also, as level as possible front to back. The S4 AFM flapper door is easily effected by gravity.

 

santiago are you sure? like aaron said, the door is easily affected by gravity, so shouldnt the door sit on its side?

 

The AFM must be mount in stock location, or upside down. Any other orientation will effect it.

 

What are you talking about he said essentially the same thing I did. The afm has to be level front to back and if its an S4 there are only two positions for it UP and up side down no in betweens. The S5 can be twisted without ill effects as its not affected by grav. as long as its level.


Santiago

 

I gotta disagree here, guys...I've been running with mine 90* from OEM position ever since the Bonez cone was installed (the instructions showed it in this position, so I figured "what the hell"), with absolutely zero problems. Plug is on top, door hinge at bottom, in this position...

 

I had this experience with my old Sport. It never really had any problems. But it will affect the sweep of the flap. This translates into a slightly different fuel to air mix than if it was in the oe position. This variance may not be enough to cause problems but it might if your highly modded.


Santiago

 

I say as long as your door hinge axis is perpindicular or parallell to the force of gravity, it shouldn't make a difference. When the axis is not at an increment of 90* that's when the binding occurs (I actually played with mine a while to verify this). I don't buy the "A/F ratio" theory either, I'm getting the same, if not better mileage with it in this position, and running stoich during cruise. Gotta remember, the spring force more than compensates for the weight of the door no matter which plane the hinge is on. If it didn't bind due to mechanical play in the hinge assy itself, we could mount them any way we wished without detrimental effects to normal airflow...

 

This has nothing to do with the hinge binding. With the flap moving in a vertical plane, every single bump and jolt that moves the car up and down on its suspension will be having an effect on the plate's movement, and hence make many small changes to mixtures. This is just common sense. It's also the reason flap AFM's are never mounted that way by the factory.

I don't understand why people do this...

 

Alot of people here make statements that while theorectically seem correct, they don't hold up in the real world. Take the AFM off, hold it vertically, jump up and down as hard as you can, and see if that door moves. I can tell you mine doesn't. If it was that sensitive, the force of acceleration would have a HUGE effect on the AFM and thus the AFRs. It doesn't though...the spring has enough resistance to prevent that.

-Joe

 

Stick a volt-meter on it and do that. Tell me the reading doesn't change at all...
No it wouldn't. The instantaneous, short-duration acceleration in the vertical direction caused by a sharp bump is a lot higher than the horizontal acceleration caused by the engine.

If this makes no difference at all, then explain to me why not one manufacturer has ever taken advantage of this alternative orientation.

 

I haven't opened the box but I can't believe that any engineer would design a flapper door that wasn't counterweighted. A counterweighted door is balanced and will not respond to gravity or acceleration in any orientation.

Now binding on the pivot is another story.

I roadrace mine with the flapper door pointed straight down. No problems.

ed

 

Come on, NZ, you know I've been around the block more than a few times, and performed my own "testing" before I settled on this unorthodox install position. I DID put a meter on it during a drive, I DID put rubber bushings under all the mounting hardware to help dampen vibrations (a little vibration is probably better than none on this critter), and the door DOES hang up due to mechanical interference when not 90 or 180.

I'm not trying to state here that this position is advantageous over the factory install orientation, only that a 90* position seems to work just as well. By extension of this logic, manufacturers see no advantage to install it at a 90, therefore they don't. I have never had a problem with any "bumps" causing fuel surges (or starvation).

The instant I have a problem with this setup, NZ, I'll let you (and everyone else) know about it. Until then, it's staying as is...

 

NZ is correct (as well as Aaron and Santiago).

I have personally seen with a scope while driving surges because of mis-leveled AFMs. These were imperceivable to the driver, but clearly shown in operation on both S4 RX-7s and NA miatas.

If it shows up in a scope, it will show up in our simple 8 bit ECUs.

Bad idea to have it any way but the correct orientation.

 

Ahh, actual field experience, that's what I'm talking about...

Exactly what orientation was this "test subject" of yours in, Mark?

 

Also, my car ran rich enough at idle with the flapper door facing down to make the downpipe glow deep red. During highway cruise, I could clearly smell the "rotten egg" odor of a cat running too rich. It was also impossible to pass emissions.

Putting the AFM back in it's stock orientation (as per the intake install instructions on my site...that's why I wrote them) fixed all those problems.

 

I the miata it was 90 degrees out, on both the FCs I have tested that way, both were at a kiddy corner angle between straight up and 90 degrees around 40 degrees off or so.

 

Hmmm, I don't seem to have those problems (running rich) with the hinge at the bottom, though, Aaron. In fact, I can discern absolutely zero difference whatsoever in performance, and as I've stated earlier, the gas mileage, if anything, has gotten better (maybe because mine's 180 from your "rich running" orientation, I'm leaning her out a little, lol)...And I saw no weird "bumps" in the meter readings toting down the road.

In any case, this topic is interesting and informative. I'm going to put a meter on her again on the way to work today and keep a close eye on her, and post anything weird later...

 

I have bonez on my S4 thus AFM mounted hinge at the bottom. I havn't noticed something wrong since then though...

 

OK, here we go- 50 mile "test drive" to work results on the AFM at 90* (hinge down)...

Voltage key on- 4.0v
At idle- 3.0v
At 55 mph cruise- 1.4v
At 75 cruise- 1.1v
At 90 cruise- .95v
***** to the wall accel- .6v (as low as I could get it to fall)
Interesting observation- when shifting, door closes very rapidly (back to 3.0v), no matter how "spirited" you are or not...When lifting the peddle during cruise, however, the needle movement is much slower to the 3v mark (makes sense, I guess, just never noticed it before). Also any peddle transitions were instantaneous, in other words, the voltage showed up before any fuel input accelerated the car...

Saw absolutely no fluctuations or "meter sticking" during the entire drive, all movement was nice & smooth. So, in short, I'm not binding, not fluctuating, etc...I'm happy with it at 90*

 

You won't see sticking, you will see the wrong readings.

If youa re leaving it that way, please do not ever post about a blown motor, or idle problems, or accell problems until it is fixed.. well on second thought, not even then, because I am sure you would not want to hear," I TOLD YOU SO" by anyone that knows anything about these cars.

 

Wow, I had no idead I'd kick up this kind of response.... lol, I have an S5, and I suppose I'm most stumped by the fact that how is the little bastard supposed to stay level if under acceleration it tilts up anyway? it would sound like it should be couple degrees down for optimal flow under hard acceleration.... wierd stuff...

 

Ah! If you have an S5, then all this doesn't matter! The AFM just has to be roughly level. The ECU filters out the jerky readings and spikes during accell/decel and bumps.

 

sweet i was starting to get in a panic about mine while i was reading this thread. i had never thought about it being off level before. my s5 n/a has been driving fine with the afm pointed just slightly downward (because of my cold air setup) but im gona go out and get it set level now.