Hi all

I am building a custom efi unit for my 4cyl petrol Toyota 4Runner, 89 model. My question is, is there any real difference between MAF Sensors, some are rather large and some are small eg; BMW's Bosch units. I thought that they all messured mass air flow and send a signal to the ecu. I have asked some BMW techies and they could not tell me if it was possible to install them in to a custom unit. Can some one in here help and advise me.

Secondly my ecu requires a air temp sender signal, which I have, but I also have water injection. The water injection has multiple independent triggers, a) rpm, b) vacume, c) air temp. Now if I was to place the air temp sender (ecu)in the pre throttle body intake tube it will give me a air temp reading of "A degrees" where as I believe to get a more accurate air temp reading it should be in the plenum chamber where the air temp is "B degrees" am I correct or not??

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Originally Posted by Cruza_1

Hi all

I am building a custom efi unit for my 4cyl petrol Toyota 4Runner, 89 model. My question is, is there any real difference between MAF Sensors, some are rather large and some are small eg; BMW's Bosch units. I thought that they all messured mass air flow and send a signal to the ecu. I have asked some BMW techies and they could not tell me if it was possible to install them in to a custom unit. Can some one in here help and advise me.

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If you don't need to consider the housing size, you still need to consider sensor performance while maintaining air intake volume.
They also use various methods of actually calculating volume. You have to have what is compatible with your Engine Control Module (ECM).
For that, you need to inspect the various sensors.

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Secondly my ecu requires a air temp sender signal, which I have, but I also have water injection. The water injection has multiple independent triggers, a) rpm, b) vacume, c) air temp. Now if I was to place the air temp sender (ecu)in the pre throttle body intake tube it will give me a air temp reading of "A degrees" where as I believe to get a more accurate air temp reading it should be in the plenum chamber where the air temp is "B degrees" am I correct or not??

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Air temperature is used to calculate air density (usually at ambient temp) and in turn contributes to fuel needs for controlled operation at what is known as the "stoicheiometric point".

You are trying to re-invent the wheel, so to speak. With that level of experimentation, you may find out some things are already tweaked quite nicely. Then again, you may stumble onto a better methodology.
Let us know...

Thank's CaptainRich.
As a custom set up I flexible when consider the housing size. I have calculated the required air volume required for my engine. My 60mm throttle body and air intake, intake tubes and air box are going to have to be enlarged to supple sufficient air.
My ECM is aftermarket, being as my vehicle was originally a carburetted version. I will get in contact with the supplier and get their opinions on sensor recommendations, if any. I am looking at simplicity and efficiency (minimal sensors and extra's) as I am finding out getting a correctly matched sensor may be an issue. I have been informed by the powers to be that MAF sensors are matched and designed for specific vehicles and ECM's (re BMW and Bosch units)
It has been mentioned that maybe I would be better of looking at installing a MAP sensor. The younger generation seem to know a lot, although at times I must question their accuracy.