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Placing MAF after the turbo??? #1554986
12/11/2015 22:31
12/11/2015 22:31
Joined: Oct 2010
Posts: 549
Bulgaria
Ferrarist Offline OP
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I know that sound bit heretic, but it's not that uncommon on other turbo application and projects.....
Just started my new trackday car and because have no space related problems, i'm considering the option to fit the MAF just before the throttle body. It's called "blow through" setup. Pull through is MAF before turbo.
Pros and cons.....
I'll be able to use less pipe length from IC to TB....
With blow through there's much less leak potential after the MAF.
With suck/pull through, there's tons of leakage points...
It also allows not to use some intake pipes and less restriction in front of the turbo
Intake tepm sensor is separate from the MAF and ECU will still read correct.
BOV and dump to atmosphere with no issues.....
Maybe slight increase in throttle response.....
Our MAF's are Hot Film type(not Hot wire) and less prone to failure. However MAF will get more dirt in this place.....oil leak from the turbo and chances of damaging the sensor are greater.....
Is there someone tried this setup?

Last edited by Ferrarist; 12/11/2015 22:35.

20VT - Alfa 156 2.0 - Alfa 156 Mid-Engined RWD - Locost 20VT

Re: Placing MAF after the turbo??? [Re: Ferrarist] #1555018
13/11/2015 09:36
13/11/2015 09:36
Joined: Jan 2009
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avtokrator Offline
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It's not bad idea overall, I had some thoughts upon it some time ago...but won't it measure less air than actual, since the air is already compressed, measuring same flow there will be more air actually flowing through, and if then that reading gets correlated to pressure, the ecu would "think" it's even less, well, I suppose it works so, mean the ecu calculations...

Re: Placing MAF after the turbo??? [Re: avtokrator] #1555032
13/11/2015 13:39
13/11/2015 13:39
Joined: Oct 2010
Posts: 549
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Ferrarist Offline OP
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Ferrarist  Offline OP
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Originally Posted By: avtokrator
but won't it measure less air than actual, since the air is already compressed, measuring same flow there will be more air actually flowing through, and if then that reading gets correlated to pressure, the ecu would "think" it's even less, well, I suppose it works so, mean the ecu calculations...

MAF measure air MASS - 1 kg air is 1kg no matter if it's 10bar compressed or 1....Mass is different from volume.....
No problem with that....


20VT - Alfa 156 2.0 - Alfa 156 Mid-Engined RWD - Locost 20VT

Re: Placing MAF after the turbo??? [Re: Ferrarist] #1555038
13/11/2015 15:03
13/11/2015 15:03

G
GrahamL
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GrahamL
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In theory this should work, but you'll have much more chance of oil contamination if the oil breather system is still connected + more chance of heat damage to the AFM due to proximity to the engine block.

The ECU data tables for the AFM will have been calibrated with the AFM in the standard position, so with the AFM being after the turbo the air passing the AFM will potentially be hotter than ever expected which may throw things out of range. In theory this won't be a problem if it was calibrated over such a wide range, but in reality... who knows what might happen, it may cause a slight error in the readings.

Re: Placing MAF after the turbo??? [Re: Ferrarist] #1555049
13/11/2015 17:09
13/11/2015 17:09
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Ferrarist Offline OP
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I will try it anyway, can revert it to original position if needed.....


20VT - Alfa 156 2.0 - Alfa 156 Mid-Engined RWD - Locost 20VT

Re: Placing MAF after the turbo??? [Re: Ferrarist] #1555051
13/11/2015 17:38
13/11/2015 17:38

G
GrahamL
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GrahamL
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It's worth a try, yes, will be interesting to hear the results.

I once tried cutting out the plastic grid in front of the AFM to remove the restriction but it didn't like it at all and the engine would misfire horribly and almost cut out at anything over 3K rpm as it came on boost.

So obviously the AFM is calibrated to expect the air flowing over the sensor in a certain way, which removing the grid changed significantly. It may be that having the air much hotter and under more pressure has a similar effect, or maybe it'll still all be within the expected limits of variation.

Re: Placing MAF after the turbo??? [Re: ] #1555053
13/11/2015 17:58
13/11/2015 17:58
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Ferrarist Offline OP
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Originally Posted By: GrahamL

I once tried cutting out the plastic grid in front of the AFM to remove the restriction but it didn't like it at all and the engine would misfire horribly and almost cut out at anything over 3K rpm as it came on boost.

Tried same on my 156 Twin Spark - almost same result.
Ecu read air temp from different sensor, and with no temp sensor into the MAF i guess there will be no problem......
Many 350Z Nissans run same blow through MAF setup.....


20VT - Alfa 156 2.0 - Alfa 156 Mid-Engined RWD - Locost 20VT

Re: Placing MAF after the turbo??? [Re: Ferrarist] #1555055
13/11/2015 18:44
13/11/2015 18:44
Joined: Apr 2011
Posts: 360
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lost55 Offline
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The "grid" in the afm is meant to be a flow straightner and give a uniform(ish) flow through the meter body.

The ecu may read a different temp sensor to the maf (does the maf give a temp out signal?)

But the flow signal from the maf is derived from the temp element in the maf and the maf will be calibrated to a given air temp range for the instrument.

So as Graham says it depends on the temp calibration range compared to the temp the maf will see after the intercooler

Re: Placing MAF after the turbo??? [Re: Ferrarist] #1555329
16/11/2015 17:00
16/11/2015 17:00

N
Nobby
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Nobby
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What does FC performance do with the big MAFs? Pretty sure they don't have mesh on them.

Chris

Re: Placing MAF after the turbo??? [Re: ] #1555332
16/11/2015 18:17
16/11/2015 18:17
Joined: Apr 2011
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lost55 Offline
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Originally Posted By: Nobby
What does FC performance do with the big MAFs? Pretty sure they don't have mesh on them.

Chris


Good point. Dont know if Leighton has his own calibration curve to use in his map. Hopefully he'll update us.

Re: Placing MAF after the turbo??? [Re: Ferrarist] #1555353
16/11/2015 22:15
16/11/2015 22:15
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Posts: 549
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Ferrarist Offline OP
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Also curious to know.....


20VT - Alfa 156 2.0 - Alfa 156 Mid-Engined RWD - Locost 20VT


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