Modifying MAF sensors into larger body

[leeroy_25]

I was thinking about modding some RB25 MAF's to mount the sensor part directly into my turbo elbow piping either as it branches off or both MAF units together in the 4" bit that mates with the turbo (big single turbo set-up).
What I want to know is two things. Firstly will it mess up the readings from the sensors if I move them into a pipe with different cross section. If I move both into a single pipe with twice the cross section of area as the standard MAF body with that work? and lastly if I mount them closer to the turbo will I start getting problems with reversion or what ever it is called where I don't run a dump valve?
Main reason for the mod is to try and save some space and replace two filters with one larger one!

Thank you
Lee

[r32hams]

Originally Posted by leeroy_25

I was thinking about modding some RB25 MAF's to mount the sensor part directly into my turbo elbow piping either as it branches off or both MAF units together in the 4" bit that mates with the turbo (big single turbo set-up).
What I want to know is two things. Firstly will it mess up the readings from the sensors if I move them into a pipe with different cross section. If I move both into a single pipe with twice the cross section of area as the standard MAF body with that work? and lastly if I mount them closer to the turbo will I start getting problems with reversion or what ever it is called where I don't run a dump valve?
Main reason for the mod is to try and save some space and replace two filters with one larger one!

Thank you
Lee

If you put an afm sensor in a larger pipe it will mess up the readings and lose you resolution.But you can reprogramme the maf translation table or vq map to adjust for this,however its not a simple matter of multiplying the values by the increase in area,as laminar flow means the air in the center of the tube travels at a different speed to the air at the pipe wall,and the sensor will no longer be in the center of the pipe.It's not to bad if you increase the diameter by a small amount,I have increased mine to Z32 size,but 100mm is quite an increase!
Also you do not need two sensors in the same pipe as you can wire one sensor to both ecu inputs if you only have one large filter.
Lastly you are correct about moving the sensor closer to the turbo,It will not work properly due to reversion.

[leeroy_25]

Thanks for the feedback there. Surely If I wire 1 sensor to the two plugs I am going to halve the flow capacity and power rating?? i.e if one MAF is rated to 400bhp for instance then with two I can run 800bhp? So if I wire to only one MAF I am limited to 400bhp? I am on Q45 MAF's at present so know about programming the MAF table!

Cheers
Lee

[r32hams]

Originally Posted by leeroy_25

If I move both into a single pipe with twice the cross section of area as the standard MAF body with that work?
Main reason for the mod is to try and save some space and replace two filters with one larger one!

Sorry Leeroy,I meant if you swap from 2 afms to 1 pipe with twice the cross sectional area then you only need to put 1 sensor in that pipe and split the signal to retain the same flow capacity,there would be no need for 2 sensors in the same pipe if you see what I mean.I thought that was what you where trying to achive.

[leeroy_25]

I see.. If that actually works out fine then great? Presumably though at idle and low down the resolution will be terrible and a pain to map?
Mainly I just wanted to save a bit of space by ridding of the MAF bodies and 1filter.
Anyone actually tried the above successfully going from 2 MAF's to one to give some feedback?

What about having them inline after the turbo? How does this effect them? I sure I read this was possible? Downsides? Also is reversion even more of a problem them without a dump valve?

Cheers
Lee