100mm MAF Housings

[Sam_]

I bought a B6/B7 S4 MAF (same as B5 RS4) for my build which turned up today. On arrival I saw the previous owner had removed the metal mesh which helps remove turbulence from the air passing over the sensor:

Not ideal but would still suffice. Anyhow, instead of looking for another 90mm housing which I'll have to make some adapters for anyway, I thought about just getting a 100mm housing with the flow straightener built in like this:

Since I don't need the sensor, just the housing, this might be better option that trying to find another one, making up the adapters etc?

 

[Sam_]

Well we'll find out when I fit it... Due to the overwhelming feedback, I had no option but to buy the 4" MAF housing with the straightener and see how it goes!

 

[14nce]

If nothing else it looks sick!

 

[Andrew@A.L.D]

what bhp are you wanting out of your build?

 

[Sam_]

450-500 would be good but for most parts I've planned ahead in case I want more.

It was more the thought of sourcing another MAF housing by paying through the nose locally or getting it from overseas, then have to make up the adapters for the 90mm or just getting this one and being done with it. Hopefully it'll be ok with idle/low speed.

 

[Sam_]

If nothing else it looks sick!

Heh, I'll probably just paint it black to look a bit more OEM.

 

[superkarl]

If you have idle or low speed troubles, and using a part ali tip, put some flow straighteners inside the tip.

Its what my mate had to do on his sr20, with a 90mm maf about 10inch from the turbo it was all over the show.

 

[Sam_]

Yeah that 100mm housing has a flow straightener built into it which should help. I might have another RS4 housing lined up though just in case.

 

[superkarl]

Il be using an 90mm rs4 one off scullies. To be honest 90mm should easily suffice and dont think youd be maxxing that out. But if using a 100mm tip you may aswell keep everything 100mm.
My whole intake is 90mm, plus i dont wana be maxxing the maf

 

[Andrew@A.L.D]

You'll find the RS4 maf can flow about 600 bhp. I know mine still has loads more to go.

Im sure bill or any mapper will tell you the RS maf will be easier to scale in

 

[Sam_]

It's not a case of worry about maxxing out the RS4 housing. I know that I won't do that. It's a case of what's easily available. Sourcing an RS4 housing locally is easier said than done and finding just the housing for sale elsewhere is a bit scarce too unless you want to pay mega money. I got an alright deal on the one above but as it turned out, it'd had the mesh removed. I'm not convinced the mesh makes much difference compared to the honeycomb proper flow straighteners though.

There's that issue, plus the fact I don't really have access to any means of making up the adapters for 90mm to 100mm for the hoses.

I'm interested as to why it would be harder to scale in though? Is it not a maths issue? Working out the area and using that to calculate flow? I'm probably miles off though...

 

[superkarl]

Scaling isnt the issue with massive mafs. It purely the nature of the air being ever so lightly sucked in such a big void, turbulence screws the low load readings and gives lumpy idle/running.
Flat out it would be fine.

I dont think its all that much of an issue the longer the TIP you have as the maf is further away from the compressor.

If youre wanting a 100mm tip, use the 100mm maf. Worry about the rest whem its mapping time and add straighteners if need be.

 

[Sam_]

Yeah, that was my worry as I posted earlier, the control of idle and low throttle openings and how that can be dealt with when mapping. It's much like fitting too larger venturis in carbs, low air speed makes it hard to meter fuel. In this case, hard to meter the air.

I've bought the 100mm one anyway so I'll just use it and keep the mesh-less RS4 housing if it doesn't sell locally.

 

[badger5]

you are going to try and measure a very low sensor signal when its a small engine with metered air being attempted to be measured within a supersize pipe. It ill be VERY sensitive, overly so, to disturbance as the measurement resolution of light loads, idle, cruise etc will likely cause erratic apparent mass airflow, which in turn will upset the fuel trims and lambda compensations badly.

Screen is essential as a minimum

you say its just maths... Not in my experience in terms of RS4 it has'nt been

 

[mattyboy199]

i removed the honeycomb mesh from the standard maf housing & left just the metal mesh in, is that an issue ? doesnt seem to cause one. only a stage 2 jabba map on a K04.

 

[beachbuggy]

i removed the honeycomb mesh from the standard maf housing & left just the metal mesh in, is that an issue ? doesnt seem to cause one. only a stage 2 jabba map on a K04.

as long as you don't remove the sticker you'll be ok!!!!

 

[Sam_]

you are going to try and measure a very low sensor signal when its a small engine with metered air being attempted to be measured within a supersize pipe. It ill be VERY sensitive, overly so, to disturbance as the measurement resolution of light loads, idle, cruise etc will likely cause erratic apparent mass airflow, which in turn will upset the fuel trims and lambda compensations badly.

Screen is essential as a minimum

you say its just maths... Not in my experience in terms of RS4 it has'nt been

That was my worry. So even with a stroker, at light loads and idle, the air speed is going to be too low to get a decent reading?

I meant just the scaling being purely maths based, not how it performs. I'm probably miles off?

When looking at the area size it becomes apparent that the jump RS4 to 100mm is actually similar to S3 to RS4:

7853.98mm (100mm) 23.457 % increase
6361.72mm (RS4 ~90mm) 26.563 % increase
5026.54mm (S3 ~80mm)

******. Better look for another RS4 housing then.

 

[superkarl]

The sizes you have quoted are external diameters btw, its internal that matters and that area that needs to be scaled.

 

[Sam_]

Yeah I know that but I don't have internals to hand. It was more an indication of relative sizes rather than exact numbers but yes you're right, they're external numbers. Do you know the internal figures? Probably -4/5mm or so less, I'd imagine.

 

[badger5]

the mesh frotn end should aid laminar flow across the sensor, so who knows.. Which is the problem. No one knows how well it will react or be stablity wise. What I can tell you is if its seeing erratic airflow it WILL cause issues and fueling trims to struggle big time.
huge pipe.... sensor sensitivity for the low level airflows just makes the thing so much more sensitive to anything other than perfectly stable airflow.

Screened ftw..

Sensor resolution for 3-4g/s of idle airflows for example in such a small tube will be very low voltage output...

It could work ok.. but I dont know.

 

[Sam_]

Cheers Bill. I'll give it a go and if it's naff, I'll have an RS4 housing on hand. I've bought it now so might as well give it a go I guess.

 

[S3 Paul]

What is "Screened "?
Sorry ive not seen it before this thread

 

[badger5]

the entry and sometimes exit of the oe maf tubes have screens to present laminar airflow to the measurement sensor

 

[mattyboy199]

as long as you don't remove the sticker you'll be ok!!!!

sticker ?

 

[badger5]

sticker ?

hmm
a certain tuner I wont name here used to stick a sticker over a measurment hole on the maf element to "scale" its airflow..... *cough*

hmmmm

 

[Sam_]

Sounds like when I got my S3. I told the garage I got it from that it had an idle problem that needed to be fixed before I bought it. When I went to pick it up they said "We adjusted the MAF". Suffice to say I took it home and checked it myself. Their "adjustment to the MAF" was to remove the breather hose from the TIP. F'ing cowboys.