My Set-up Might Be Faulty

justinb2488 · Jun 12, 2013

OK so I have a edelbrock 70mm TBI and I also have the ford air flow sensor I guess for a 55mm TBI? Part # f1zf-12b579-aa. Under that its #afh-03b. Should I buy a air flow that is rated 70mm I'm guessing?

jrichker · Jun 12, 2013

The MAF body and sensor are designed to match each other. Therefore you can't swap sensors between different part number MAF bodies and maintain proper calibration. The assembly is designed to match the computer’s internal program, and swapping a different MAF can upset the computer's calibration.

The OEM Ford MAFs are not calibrated to injector size. The injector sizing is done in the computer’s internal programming. Aftermarket MAF’s “lie” to the computer in an attempt to fool the computer into changing the injector pulse on timing to match the increased airflow.

The only other MAF that is a one for one swap for a 93 and earlier 5.0 Mustang is the 94-95 Mustang MAF.

94-95 Mustang GT MAF - $40-$100. It is 70 MM instead of the stock 55 MM on regular stangs built prior to 94. It uses a slip on duct on the side that goes to the throttle body and a 4 bolt flange on the other. You need a flange adapter to fit the stock slip on air ducting that goes to the air box. Wiring plugs right in with no changes. *1 *2

Once your replacement 70MM MAF is in place, disconnect the battery for about 10 minutes. When you reconnect the battery and start the engine, the computer will relearn the settings for the new MAF.

*1.) Metal flange adapter http://www.kustomz.com/cat3.html Buy the TR70 for $44.95. Or spend some time on eBay looking for one that may fit.

*2.) MAF & sensor interchange
The 94-95 Mustang 5.0 MAF & sensor is also found on:
1995-94 Mustang 3.8L F2VF-12B579-A2A,
1994-92 Crown Victoria 4.6L F2VF-12B579-A2A,
1995-94 Mustang, Mustang Cobra 5.0L F2VF-12B579-A2A,
1994-92 Town Car 4.6L F2VF-12B579-A2A,
1994-92 Grand Marquis 4.6L F2VF-12B579-A2A,
Evidently the –A1A, -A2A, AA, etc. on the end of the part number is a minor variant that did not change the operating specs. You should be able to ignore it and have everything work good.

justinb2488 · Jun 12, 2013

OK so basically that I have a 70mm throttle body I need a 70mm maf? Correct?

Mustang5L5 · Jun 12, 2013

That's a stock MAF.

You don't need a larger MAF, but it would be nice. If you have stock heads on the car, it won't make a huge difference in the grand scheme of things. Its like trying to cram an elephant through a window with the stock heads

mikestang63 · Jun 12, 2013

justinb2488 said:
OK so I have a edelbrock 70mm TBI and I also have the ford air flow sensor I guess for a 55mm TBI? Part # f1zf-12b579-aa. Under that its #afh-03b. Should I buy a air flow that is rated 70mm I'm guessing?

What is the rest of the setup on your car?

If you have stock heads, intake, exhaust, etc. then don't bother swapping out your MAF to a high dollar MAF. If you feel the need to swap, find a MAF from a 94-95 Mustang. It is nearly identical to your stock as far as mapping, and is 70MM. You'll need to either fab up a bracket or buy one off Ebay for the mounting flange on the air filter side. Total cost should be under $75. Do NOT swap out the electronics from one MAF housing to another.

IMO, your TB is too big for your application anyway. With the stock heads and intake, it doesn't matter if you threw on a 90MM TB, it is only going to flow so much as the stock pieces are very restrictive.

The first thing I would do is replace the stock air filter with a K&N piece. That is good for a solid 10h for under $50.

justinb2488 · Jun 12, 2013

No I got the cobra intake not sure on heads yet just got it might be gt40 heads because I seen the plugs angled. It also has moroso air piece with filter

7991LXnSHO · Jun 12, 2013

I was shocked how little the stock MAF is. It seems like if you are opening the TB, it is pointless to have the stock MAF restriction up the line, especially if you then try a K&N on the other end. It is a big pinch in your intake track straw.
In other points, didn't folks with dataloggers say a K&N did not make any difference in power or air temp over the 5.0 stock air box? My BBK kit looks cool, but I do not think it helps.

justinb2488 · Jun 12, 2013

Yeah I hear how you might get 5hp gain but it deff improves the airflow I think. Yeah so I see that the 94-95 cobras have a 70mm maf so I'm gonna start junk yarding it hear this weekend there also on eBay for like $50

7991LXnSHO · Jun 12, 2013

One less thing to worry about later too. Other mods will take advantage of that airflow. That makes it a good "only" 5 HP in my book.

justinb2488 · Jun 12, 2013

Yeah that's good for me.

Hawkeye_306 · Jun 12, 2013

As a general rule, you want the air passage to either be the same size or get smaller all the way from the air filter to the intake valve - going small to large at any point actually makes flow worse. But most of us can only afford to upgrade one part at a time, so short term compromise is part of the deal. Good luck!

justinb2488 · Jun 12, 2013

yeah that's what I thought. OK so I just need to find a cobra with a 70mm Maf. Yeah imthe same way part at a time. Getting that then under drive pulleys

7991LXnSHO · Jun 12, 2013

I went with a BBK before I read about the OEM swap. I am not upset with that decision, it is a good looking and good working piece. Now if the TB did not whistle!

justinb2488 · Jun 12, 2013

Yeah that's what I was looking at then I seen the cobras have them. Your tb whistles? I don't think mine does

mikestang63 · Jun 13, 2013

All the BBK 70 mm TB I have seen whistle, including the one on my car. MAF's are calibrated to the injector size so you don't use a cobra MAF unless you have 24lbers. You can get a tune to have Cobra MAF work with other size injectors if you want but it is much easier if you have the stock 19lbers, you want a stock 94-95 GT70MM MAF for about $40 from any junkyard

7991LXnSHO · Jun 13, 2013

justinb248ost: 8735116 said:
Yeah that's what I was looking at then I seen the cobras have them. Your tb whistles? I don't think mine does

Yes, my BBK TB whistling lets me know when the IAC is working. It just does it at idle, and I read I can cure it by rounding the sharp edges in the TB passages. I wish someone would post A pic showing exactly what to polish/ grind.

jrichker · Jun 14, 2013

mikestang63 said:
All the BBK 70 mm TB I have seen whistle, including the one on my car. MAF's are calibrated to the injector size so you don't use a cobra MAF unless you have 24lbers. You can get a tune to have Cobra MAF work with other size injectors if you want but it is much easier if you have the stock 19lbers, you want a stock 94-95 GT70MM MAF for about $40 from any junkyard

Wrong answer...
Ford OEM MAFs are calibrated to match the computer's internal program. The program uses the MAF data to set injector on time, which sets the air/fuel ratio.

Aftermarket MAFs have no way of modifying the computer's internal program, so they "lie" to the computer by changing the amount of output voltage for the amount of air they are passing. It's a sloppy method for determining a precise problem. That's why a custom dyno tune and a chip burned using the dyno data is the ultimate answer to large MAFs and/or large injectors.

Mustang5L5 · Jun 14, 2013

jrichker said:
Wrong answer...
Ford OEM MAFs are calibrated to match the computer's internal program. The program uses the MAF data to set injector on time, which sets the air/fuel ratio.

Aftermarket MAFs have no way of modifying the computer's internal program, so they "lie" to the computer by changing the amount of output voltage for the amount of air they are passing. It's a sloppy method for determining a precise problem. That's why a custom dyno tune and a chip burned using the dyno data is the ultimate answer to large MAFs and/or large injectors.

That myth, along with the TPS .9999V myth needs to die.

7991LXnSHO · Jun 14, 2013

Hawkeye_306 said:
As a general rule, you want the air passage to either be the same size or get smaller all the way from the air filter to the intake valve - going small to large at any point actually makes flow worse.

I has not thought of it that way, but a general funnel shape leading to a venturi right at the intake point of the head would be the best way to increase velocity. Forced induction would even benefit from the venturi effect to increase intake stream velocity. OOOHH, Science at work!

Hawkeye_306 · Jun 17, 2013

Ha, that was the one thing I retained from fluid dynamics class 10 years ago . In addition to the velocity increase purely from change in cross section, when going large to small the "dead air" at the circumference of the passage acts like a funnel to smooth flow. In contrast, small to large passages cause "mini-whirlpools" at the interface which spin opposite of flow direction & resist flow.

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