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Old 08-02-2011, 10:56 PM   #1
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Default Stock maf max boost?

Hi,
Does anyone know how many psi of boost a stock 1.6L flap type maf can handle before being maxed out?
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Old 08-02-2011, 11:03 PM   #2
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There have been reports of it handling up to 30 psi but 32 psi is the breaking point.
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Old 08-02-2011, 11:07 PM   #3
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that can't be real, i thought it would be more like 7-8 psi for the flap to be fully opened

Last edited by Green Machine; 08-02-2011 at 11:49 PM.
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Old 08-02-2011, 11:13 PM   #4
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The real question is why are you running an AFM with a turbo setup?
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Old 08-02-2011, 11:48 PM   #5
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because i'm poor and that's all i can afford for now
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Old 08-03-2011, 01:44 AM   #6
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Do us all a favor and don't turbo a DD with band aids.
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Old 08-03-2011, 02:04 AM   #7
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It's not really a hard cutoff, the VAF sensor just becomes less and less linear as airflow increases beyond stock.

Here is what it looks like with a TD04H-15G turbo on an otherwise stock 1.6 engine (mine, to be precise). Each line is a different manifold pressure (expressed in relative PSI, where negative numbers are vacuum), the X axis is RPM, and the Y axis is sensor output voltage (remember that voltage decreases as airflow increases; 5v is fully closed, 0v is fully open):



As you can see, it's already damned close to flatlining at atmo, and loses resolution almost exponentially from there. Friends don't let friends boost on a stock ECU.
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Old 08-03-2011, 02:09 AM   #8
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Ok that's fine, bandaids are not bad, I ran them and they worked, and I had a fun car that was pretty reliable. Not everyone can throw down $600 for an MS.

What the OP needs to do is research more. First off, you should not be "boosting" the AFM, it will be plumbed into the intake for the turbo, seeing vaccum, no boost there. Second, posting a question like this on this forum shows that he has not looked at 1% of the threads on this forum. All the information is here, people have turboing miatas for years, you aren't the first. Start with the stickies, the FAQ, the MT wiki, READ.
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Old 08-03-2011, 07:53 PM   #9
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thanks for the info joe that was very helpful
i'm currently running at 5 psi using an Emanage blue on this setup (i know i know). i want to increase boost to 8 psi,
would changing the stock afm for an rx7 afm be better than adding the EMB map sensor?
i could make it run with the stock afm but it would be rich at low boost
i need a cheap solution just to make the car run well until i get better engine management

Last edited by Green Machine; 08-03-2011 at 08:14 PM.
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Old 08-03-2011, 11:41 PM   #10
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Quote:
Originally Posted by Green Machine View Post
would changing the stock afm for an rx7 afm be better than adding the EMB map sensor?
You're not already running a MAP sensor?

Quote:
i could make it run with the stock afm but it would be rich at low boost
I ran an EMU for about a year, but I'm not very familiar with the EMB. What controls are available to you? I realize that you can't directly downscale injector duration, but I assume that you can trim VAF (both positive and negative) as a function of MAP, correct?


Quote:
i need a cheap solution just to make the car run well until i get better engine management
Cheap solution: don't **** with anything until you can afford better engine management. Total cost: $0.00
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Old 08-12-2011, 10:53 PM   #11
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MAF can handle boost, in fact I have posted pictures of one that is at 25 psi.

My setup handles 15 psi on a T3/T4 .50 trim, FYI: RX7 Turbo II MAF, no problems at all after a year or so. I have had all kinds of other problems like blown head gasket, oil pump etc, but none whatsoever with the MAF.
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Old 08-13-2011, 03:25 AM   #12
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All his other problems are good reasons not to try to make power with a AFM. Shitty tune = detonation which can lead to head gasket or oil pump failure along with many other failures. Run the car on wastegate spring, drive it easy and save your money for a MS.

But if you insist on running an AFM for now, an rx7 unit will flow significantly better and the car will run slightly richer then with a stock AFM (at least it did with my junkyard AFM on my stock 1.6)
Also if your having trouble finding an rx7 AFM you can use the AFM off a toyota camary v6 its the same dimensions as an rx7 unit but my car did seem to idle much better and accelerate quicker with the camary AFM compared to the rx7 one. I never dynoed the car with the camary unit but the rx7 unit ran a little richer then stock and picked up 6whp over my stock 1.6 maf, on a practically stock 1.6 car.
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Old 08-13-2011, 08:44 AM   #13
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Just go to RX7club.com, open an account, make a few postings and open a thread for a FM in the wanted sub-forum.

Not to hijack the thread, the reason the oil pump failed was because I had a aluminum damper which is a known fact that excessive vibrations at 15 psi of boost is not good at all, something I learned the hard way. The engine has not suffered detonation, I use sound amplifier which all this stuff I have already covered on this forum.

The device is ten times better than any knock sensor system in the market, best of all it costs less than 40 dollars to make one.

http://autospeed.com/cms/article.html?&A=0348

Check out on the article where he matches it against the best devices in the market.

Detonation detection tool

Such tool is amazing, you can check for bad wires, hear the transmission shifting, valvetrain, turbo spooling and best of all of course, for knock detection. I hook the alligator clip to the electric oil sensor.

Here is actually the one I built, compared to his, mine I just leave the clamp connected and route it through the firewall to the glove compartment with a headphone jack. When I want to use it is just plug and play.



Before I went with forged internals, I opened the engine running at 15 psi with the ghetto piggy back SAFC tuning and pressurized MAF, it had 3 bent rods, the pistons were in perfect condition. Only thing was a little scuffing but it was due to the slightly bent rods, which the only reason I opened the engine was for a failed oil pump. Before I went forged it had [email protected] Miata pistons (210 compression), I even removed 2 plys from the stock 4 ply metal headgasket and it never gave me any leaking or overheating problems. The rods failed because of the torque and amount of hp, the piston rings were fine, had a little bit of blow by, but c'mmon was boosting with three slightly bent rods.

The car at idle reads, 14 - 16 AFR, at cruising highway speed around 13 to 14, at 1 bar 11 to 12. You control the amount of fuel by adjusting the flap when removing the black plastic cap on the top. Grab a drill and remove the little metal cap so one can adjust idle. Follow adjustments with the throttle idle screw and with the AFPR, some tweaking with sparkplug gap, and then some with the ignition timing and you are done. My idle stays true at 700-800 rpms, and rides like a NA car while not spooling.

Forged internals, 84mm pistons, lightened sotck flywheel, clutchnet clutch with 4 pad disc, Ki cylinder head, custom turbo manifold, 550cc and afm from RX7 turbo II, walbro 255, adjustable cam gears, fmic, 2.5 exhaust piping with magnaflow muffler, NGK6 .040 gap with 93 octane gas, ARP head studs, fyi - ebay chinacharger w/ restrictor.

Like it is right now I have matched it against a STi with fmic, exhaust etc and won by 2 cars, EVos are cake, a few Mustangs, G35 and 2011 BMW 335i.

In fact it is even better to have the MAF after boost because it taking real readings of the air coming into the engine, not like when having it before the turbo it reads the air or whatever, but the air coming in is totally different from the one registered by the MAF.


Did not mean to hijack, but trust me it can be done without any MS, and by the way I have read a fair share of blown engines who claim a good tune with MS, and that is from clubprotege, mx3 and here at miata which everyone knows the BP is the shared platform across all three vehicles.
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Last edited by mazpr; 08-13-2011 at 09:39 AM.
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