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do YOU have rubber?
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Discussion Starter #1
Ok let’s talk about MAFs.

Let me begin by saying “MAF” is smaller in length than the minimum FF character length search requirement so forgive me if this has been covered before. I’ve been thinking about larger MAFs as just looking through the outward port of my airbox, it is clear that there is a very narrow bottleneck there. Now I know that you can get MAFs larger than my stock 55mm(?) item from Ford but this is expensive and I had a few thoughts floating around in my head.

Firstly allow me to ask for clarification on what a larger MAF does with regards to voltage output. My standard MAF provides the ECU with a voltage range that it uses to quantify the amount of fuel to inject. Do the larger MAFs supply a greater voltage range? If not, it seems to me that more air will be passing through the larger MAF aperture on the bigger MAF than the computer thinks. If you’ve got more air flowing through the MAF for the same given MAF voltage output you’re going to lean out your AFR aren’t you?

Secondly, I’ve heard that the availability of LS1 MAFs is reasonable and that they represent a somewhat compatible Windsor upgrade option. For this to be considered, they’d have to be reasonably cheaper than the Ford option and from what I’ve heard from Ford parts, this may be the case. Now is there any truth to this? Do the LS1 MAFs talk to the ECU in the same manner as the Windsor unit (ie a single sided or differential voltage signal – one/two or two cables respectively)? The voltage ranges may be different but this is not a problem. I can design and manufacture interface circuitry to convert and calibrate an alien MAF voltage range into a range suitable for EEC-V. The LS1 MAFs seem to measure air parameters differently. Attached is a pic that I found – it is an SS inductions unit but presumably similar to the original unit.. No mesh. Has this been done? Any potential problems?

Thirdly, I got to thinking about the cost of upsizing MAFs and then wondered how expensive it would be to have a simple cylindrical plate (like the herrod air injection pipe thingy) manufactured and fit the standard MAF wire in between the plates. The MAF mesh just needs to cover the entire aperture doesn’t it? Is the mesh wider than 55mm on the stock item so that this could be accommodated? Is there anything I’m missing?
 

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345kw of V8 Windsor Power
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2,784 Posts
Firstly, the mesh has nothing to do with it, it is there to stop rocks and other large pieces that may go through the airfilter being sucked up into the engine. If you look through the MAF closely you will see a small port to the side of the main 55mm opening. This is where the sensor is. After market MAF's for the Ford V8 engine are around although for best prices you should order fron the US. A 75mm C&L MAF should set you back about $300, this uses your own MAF electronics and you can buy different sample tubes to suit different injectors. A better but more expensive option is a Pro-M or GMS MAF. They are more expensive at around $5-600 and come with calibrated electronics to suit your injectors.

Here is some pics of my GMS MAF. It's about 95mm at the opening and goes down to about 78mm at the narrowest point.

http://www.fordgallery.com/showphoto.php/photo/4599/password/a801c142e3c46ea846e68b4b5f6d76ad/sort/1/cat/500/page/1

http://www.fordgallery.com/showphoto.php/photo/4600/password/a801c142e3c46ea846e68b4b5f6d76ad/sort/1/size/medium/cat/500/page/1
 

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a vile merchant
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714 Posts
Just bolt your maf wire into a 70mm AU maf body. That's what I've done and I felt it made a noticable increase power/response, mainly in the lower revs. All you have to do is go and test drive any AU V8 and bring a socket and torx screwdriver in your pocket! :p
 

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Two SC 61's = trouble
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Just remember the AU ll's on had larger injectors so they have to be combatable..So AU l's are o/k or Cobra type maf for 19's...I think you need to splice the wires also as connector is different...
 

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a vile merchant
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If you use your own electronics/maf wire in the AU maf body it wouldn't know the difference. It just screws in.
 

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do YOU have rubber?
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Discussion Starter #7
...but this is my question... how do the outputs of these bigger MAFs differ from the baby ones? Above a certain size are larger injectors needed such that the injectors are open for the same amount of time but more fuel is injected due to the higher pressure? Cheers for the clarification of the mesh EDXR8, I'll have a closer look tomorrow. It seems then that the housing has no functional role but to hold the whole thing together. Is there any reason for arguments sake why the system would not work if you just mounted the MAF electronics inside a piece of tubing... made of rubber even? Surely a large MAF housing style body can be made cheaply compared to some of these after market options?
 

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OFR #7
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!Gn|T|0n said:
...but this is my question... how do the outputs of these bigger MAFs differ from the baby ones? Above a certain size are larger injectors needed such that the injectors are open for the same amount of time but more fuel is injected due to the higher pressure? Cheers for the clarification of the mesh EDXR8, I'll have a closer look tomorrow. It seems then that the housing has no functional role but to hold the whole thing together. Is there any reason for arguments sake why the system would not work if you just mounted the MAF electronics inside a piece of tubing... made of rubber even? Surely a large MAF housing style body can be made cheaply compared to some of these after market options?

How the outputs vary will depend not just on the internal diameter of the MAF, but the ratio and flow characteristics of the sample tube in comparison to the ID.

Yes you are correct when you say that with a larger injector more fuel is added when compared to a smaller injector operating on the same duty cycle and fuel pressure.

When the ECU is operating in closed loop mode (light to medium throttle positions), it will try and optimise the AFR (to a pre-programmed value(s)) using the O2 sensors as feedback. In this mode if more air enters the engine (than the voltage returned from the MAF is indicating) the ECU will pick up the increase in the AFR and add more fuel to compensate. The ECU will remember this increase in fuel requirement as it continually learns in closed loop mode. Be aware that the ECU will only be able to compensate so far in closed loop mode.

The problem you may run into is in open loop mode (medium to full throttle positions). This is where the ECU is no longer trying to optimise the AFR, it just adds fuel based on the TPS, revs, MAF etc. Thus if more air is entering the engine then the ECU thinks (based on the voltage returned from the MAF), you will run leaner. How much leaner will depend on how much extra air is entering the engine. This problem can be fixed with a piggy back computer such as a Unichip, an adjustable fuel pressure regulator or yes you could add larger injectors, but you would need to be careful you don't start adding too much fuel.


Try and think of it this way. The ECU has been calibrated such that the range of voltages returned from the MAF equate to a range of air masses entering the engine. The ECU has also been programmed to output a certain injector duty cycle based on the voltage returned from the MAF (amongst other parameters). Therefore, if you change your MAF, you are changing this MAF calibration in the ECU and thus affecting the duty cycle the ECU outputs to the injectors. In closed loop mode the ECU may be able to compensate for this, however in open loop mode it can't.

When you purchase a Pro-M (or GMS) MAF you are also getting new electronics (thus the increased cost over a C&L). These MAFs are "calibrated" to a certain injector size. What this means is the MAF will produce a voltage output to the ECU proportional to the mass air fow AND the injector size. This voltage signal is modified to take into account the greater mass of air entering the engine and the injector size.

The C&L type MAFs use your electronics and compensates for the larger flow and different injector sizes by using different sample tubes. What they try to achieve is a modification of the voltage to the ECU using the sample tube design.

You could use your standard electronics in an AUII (or for that matter a BA XR8 MAF housing which I have seen successfully done before using a piggy back computer to correct the open loop AFRs), however as with any MAF change I would recommend that the AFRs should be checked on dyno.


Oh and yes you could use a MAF housing made of rubber, however the smarts in the design of the housing is the calibration of the sample tube as I have mentioned above. I have a C&L MAF and it is very agricultural in construction!
 

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do YOU have rubber?
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Discussion Starter #9
Thanks Big Mick - a very comprehensive post! OK so the MAF accommodates the fact that the ECU is calibrated to equate a certain MAF voltage with a certain mass of air and its output is such that the standard fuel rail pressure and injector duty cycle will result in the expected air/fuel mix. This makes sense. Allowing more air through the MAF in its standard form will result in some action being required to increase fuel also. I've recently learned that the LS1 MAF operates on a frequency varying voltage (PWM?) output rather than a continuous output range. It seems that if a chip / injectors are required, there is little chance that a home MAF job would be a cost effective option. Thanks.
 

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do YOU have rubber?
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2,357 Posts
Discussion Starter #10
Ah Ha! I think I've thought of a way to accommodate any size MAF aperture with the standard electronics, ECU and injectors whilst maintaining a nice AFR. If I get time I'll play with it.

I wonder if anyone else would be interested in such an upgrade.
 

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i pity tha fool
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Big Mick said:
The problem you may run into is in open loop mode (medium to full throttle positions). This is where the ECU is no longer trying to optimise the AFR, it just adds fuel based on the TPS, revs, MAF etc. Thus if more air is entering the engine then the ECU thinks (based on the voltage returned from the MAF), you will run leaner. How much leaner will depend on how much extra air is entering the engine. This problem can be fixed with a piggy back computer such as a Unichip, an adjustable fuel pressure regulator or yes you could add larger injectors, but you would need to be careful you don't start adding too much fuel.
thats it. that's also why i'm gonna do MAF/Injectors later on, and the easy stuff now.
 

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a vile merchant
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Problem is the easy stuff doesn't help all that much when you have a golf ball sized maf choking up the inlet!
 

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345kw of V8 Windsor Power
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!Gn|T|0n said:
Ah Ha! I think I've thought of a way to accommodate any size MAF aperture with the standard electronics, ECU and injectors whilst maintaining a nice AFR. If I get time I'll play with it.

I wonder if anyone else would be interested in such an upgrade.
I don't think you will find an easy fix. Plenty of people and companies have tried to find an easy way around it but they are never successfull. Even small errors can cost you an engine. How are you thinking of doing it?
 

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i pity tha fool
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best way i assume is using something like tweecer, slapping on a big maf, and the injectors you want, then calibrating the open loop AFR values manually on a dyno.
 

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Two SC 61's = trouble
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Another... Aftermarket ecu and no maf....
 

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do YOU have rubber?
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Discussion Starter #17
Well how about this... now this just a concept, not a well thought out idea.

If you inserted logic into the injector pulse train such that they remained open for an additional amount of time proportional to the percentage increase in MAF area then essentially the error introduced in the AFR by allowing more (unmeasured) air into the engine is countered by the fact that you are allowing a proportional amount of extra fuel in. No MAF recalibration, no ECU changes, standard injectors. The failing of this is the fact that the MAF voltage is not exclusively used to quantify fuel requirements.
 

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345kw of V8 Windsor Power
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I think it will be way too much work, you would have to flow test each MAF, work out the flow difference at regualr intervals and then program for it. And if you get it even slightly wrong you may have big problems. With the current australian dollar you should be able to get a C&L MAF from the US for around $250 including freight.
 

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Modifying the MAF and injectors without reprogramming the ECM will result in load calculation being wrong. There is a scalar in the ECM called "mass air flow transfer function". With this we can modify to suit the calculated amount of air coming into the engine and correct the load calcs. Injector sizes and slopes can also be altered to make the required changes to suit.
 

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Black 200kw wheel barrow
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GT-P said:
Modifying the MAF and injectors without reprogramming the ECM will result in load calculation being wrong. There is a scalar in the ECM called "mass air flow transfer function". With this we can modify to suit the calculated amount of air coming into the engine and correct the load calcs. Injector sizes and slopes can also be altered to make the required changes to suit.
you can modify this without a piggyback computer?
 
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