AFM Adjustment??

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10-05-2005, 09:50 PM
Z3_GoCar

Alright, so this is something I've been thinking about. The ITAC says everything ahead of the AFM is open as long as the air is taken from the stock location or inside the engine bay. But it says nothing about the AFM itself. I presume this means that touching the AFM is off limits? How about port matching the AFM? Any tubing between the AFM and the throttle body must be factory or factory replacement? I'll be replacing a traction control unit which is between the AFM and the TB, Do I have to get the factory tube for the non traction control car? Does it have to be the right part number even? Is this one of those things you do, but don't :rolleyes: If so you can pm me.

James
10-05-2005, 10:47 PM
Eagle7

Seems like there was a FastTrack allowing relocation of the AFM starting next year, with the implication that the tube from the AFM to the throttle body would be open.
10-06-2005, 05:17 AM
C. Ludwig

That just came out in the latest Fastrack. You're still not going to be able to port or otherwise modify the AFM.
10-09-2005, 01:38 PM
Z3_GoCar

Quote:

Originally posted by C. Ludwig@Oct 6 2005, 02:17 AM
That just came out in the latest Fastrack. You're still not going to be able to port or otherwise modify the AFM.

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Thanks for the reply's. I just saw the new fastrack allows any tube ahead of the throttle body. I'm concerned because SM is allowed to open up the AFM for "adjustments" what ever that means. Or is this something that can be done with a Motec type system by adjusting some tuning parameters, then Nevermind :rolleyes:

James
10-18-2005, 10:01 PM
MMiskoe

I didn't see the SM item in Fast Track, but if they are allowing it to be "adjusted" it might just be an allowance to change the A/F ratio. The 1.6 Miatas have a flap door which can have its pick up moved, fooling the ECU into thinking there's a bit more or less air going through it. Grass Roots had an article about dyno tuning one that explained it. It had to do w/ moving the pick up relative to the flap door pivot shaft. Hard to police so perhaps they just made it legal.
10-19-2005, 07:40 AM
JeffYoung

Key-rect Miskoe. Apparently, everyone was doing it so they just made it legal.

There is a little wheel in the AFM with gear notches that you can adjust left and right to help lean out the mixture at WOT (the cars tend to run rich at stock settings). Not legal for IT, but allowed in SM.
10-19-2005, 12:35 PM
stevel

Ok, now that the intake tube is open ahead of the throttle body does it mean it has to stay in the exact stock location? I wanted to reroute the intake tube down a little lower, and the air would still be either pulled from within the engine bay or from the stock location (have to see what works best). To me it seems so from the fasttrack but I wanted to be sure.

steve
10-19-2005, 08:50 PM
Eagle7

My take on it is that the AFM must not be modified, and all the intake air must flow through it, but you can mount it wherever you want and connect it to the throttle body however you want.
10-19-2005, 10:58 PM
ITANorm

Quote:

Originally posted by JeffYoung@Oct 19 2005, 06:40 AM
Not legal for IT, but allowed in SM.

It's essentially the same on all Bosch K-Jetronic systems. How do you figure that it is not allowable in IT? It is an adjustment, not a modification. Nothing is replaced, you just move the spring to another notch on the wheel - no different than adjusting the timing. And other than the fact that you have to cut the silicone sealer around the top cap of the AFM (which you would also have to do to repair a bad solder joint in the AFM - which is allowable), it's undetectable - because the "stock" setting is unmarked.
10-19-2005, 11:24 PM
Z3_GoCar

Quote:

Originally posted by JeffYoung@Oct 19 2005, 04:40 AM
Key-rect Miskoe. Apparently, everyone was doing it so they just made it legal.

There is a little wheel in the AFM with gear notches that you can adjust left and right to help lean out the mixture at WOT (the cars tend to run rich at stock settings). Not legal for IT, but allowed in SM.

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Isn't this something where a dyno tuned Motec type system really helps out? In that you can adjust the gain/rpm to help set the A/F ratio? I'm really familiar with the old Bosch K-jet system and it's moving flap, but wonder how this affects the air flow verses a hot wire/film system like on the L-jet and modern BMW's like my Z3. Although it's not like there's a choice in the matter, you run what you have. Since the tract ahead of the TB is now open I can definetly trashcan any traction control butterfly between the AFM and the TB. Although one might want to consider the tract length when moving their AFM in that what happens at the AFM always has a flow dependant time lag.

James
10-19-2005, 11:32 PM
Z3_GoCar

Quote:

Originally posted by ITANorm@Oct 19 2005, 07:58 PM
It's essentially the same on all Bosch K-Jetronic systems. How do you figure that it is not allowable in IT? It is an adjustment, not a modification. Nothing is replaced, you just move the spring to another notch on the wheel - no different than adjusting the timing. And other than the fact that you have to cut the silicone sealer around the top cap of the AFM (which you would also have to do to repair a bad solder joint in the AFM - which is allowable), it's undetectable - because the "stock" setting is unmarked.

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IT and SM don't quite match up. SM allows any clutch combo, go ahead and put a multiplate clutch in an SM as it's legle. In IT doesn't the clutch have to be the same type as stock, unless the Miata came stock with multi plate clutches. How about SM flywheels? I do believe that SM allows lightened flywheels on the 1.6 but not the 1.8'er. I'm sure there's more but these are just a few I can think of at the moment.

James
10-20-2005, 08:44 PM
ITANorm

^^^

Agreed - I was asking Jeff what was illegal about it in IT - as in the quote.
10-21-2005, 07:57 AM
Doc Bro

So what about those things in the Summit catalog called Tornados or something on that theme. They change the flow pattern of the incoming air and make it swirl so that it blah...blah....blah... Are these things legal and do they work? I was thinking about putting one on my f350 for next tow season along with maybe the Bully Dog computer upgrade (1000 ft-lbs of torque!!!) But if they are legal and work I'll buy two. :D
Rob
10-21-2005, 10:23 AM
JIgou

Quote:

Originally posted by Z3_GoCar@Oct 19 2005, 10:32 PM
IT and SM don't quite match up. SM allows any clutch combo, go ahead and put a multiplate clutch in an SM as it's legle. In IT doesn't the clutch have to be the same type as stock, unless the Miata came stock with multi plate clutches. How about SM flywheels? I do believe that SM allows lightened flywheels on the 1.6 but not the 1.8'er. I'm sure there's more but these are just a few I can think of at the moment.

James

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Any clutch is allowed as long as it bolts to the stock, unmodified flywheel.

Lightened flywheels are not permitted in any model SM.

In my experience, adjusting the AFM on a Miata gains around 2 HP, depending on where the wheels was when you started. (Obviously some gain more, some less.)

Jarrod
02-25-2006, 10:00 PM
footewerks

What about this one. What if you locked the AFM wide open and used a linear resistence throttle position switch and installed a mega squirt or motec cpu in the stock cpu housing. Would this be considered legal.
02-26-2006, 09:17 AM
Ron Earp

The adjustments on the Miatas is just that and is described in the factory manual. So, I would think it legal (and it is in SM based on rules) in IT based on the fact it is an adjustment, just like adjusting your alternator belt tension.

Adjusting the AFM on the Miatas does help a good bit. I've done four on them on the dyno with the largest gain from just the AFM being 6 rwhp, the average about 3 rwhp. The Miatas run fat from the factory, typically 11:1 or worse according to the wideband, and getting them into the high 12s, leaning them out, helps power. Combined with some timing advancement we've seen total gains around 8-10 rwhp as a best, with the average being about 5-6 rwhp total.
02-26-2006, 10:12 AM
Eagle7
Quote:

What about this one. What if you locked the AFM wide open and used a linear resistence throttle position switch and installed a mega squirt or motec cpu in the stock cpu housing. Would this be considered legal.
[/b]
- What if you locked the AFM wide open - Nope
- and used a linear resistence throttle position switch - Must be stock
- and installed a mega squirt or motec cpu in the stock cpu housing - Yes
02-27-2006, 08:54 PM
MMiskoe

I'm curious how you would actually measure air flow w/ just a throttle position sensor. Unless you go back to an old manifold vacuume set up, I don't think the ECU will know what you've got for incoming air. That's the beauty of an AFM set up.