Do you need a MAT if using MAF?

jb007 · Post by **jb007** » Wed Jul 27, 2016 10:16 pm

Hope this is the right forum... Do you need a MAT if using a MAF, as I gather the MAF calculates the Mass Airflow based on temp, so is self correcting. My MAF (Bosch HFM5) also provides a seperate temp sensor, if I do require a MAT.

Jim

Matt Cramer · Post by **Matt Cramer** » Thu Jul 28, 2016 5:54 am

While you can run without it, adding a MAT sensor will allow a couple extra features like MAT timing retard. Plus it's handy to data log.

jb007 · Post by **jb007** » Thu Jul 28, 2016 5:59 am

Matt Cramer wrote:While you can run without it, adding a MAT sensor will allow a couple extra features like MAT timing retard. Plus it's handy to data log.

Thanks Matt. I'll connect up the MAT temp sensor then... it will be the most accurate.

jacky4566 · Post by **jacky4566** » Thu Jul 28, 2016 10:08 am

Matt Cramer wrote:While you can run without it, adding a MAT sensor will allow a couple extra features like MAT timing retard. Plus it's handy to data log.

HFM5 brother! I am just installing one of these now.

Matts suggestion would only work in a blow through turbo setup. Most factory setups (At least Subaru) put the maf pre turbo.

But to answer your question. Yes hookup the MAT. Theoretically the MAF should compensate but realistically even OEM use MAT.

Tuning the curve will be different since the MAF will compensate somewhat but usually not enough. You will have to do lots of data logging in cold/hot days to figure out the true curve. I would start with a very mild or no curve and work from there.

subwoofer · Post by **subwoofer** » Thu Jul 28, 2016 12:59 pm

I think I can set up a scatter plot to find that function, will have to think a little bit about it. The curve should hopefully be the same for all HFM5s, so it is just a matter of finding it.

The HFM5 is a very user friendly piece of kit, as long as you stay away from oiled air filters and MAF cleaning concoctions they are accurate and reliable.

jb007 · Post by **jb007** » Thu Jul 28, 2016 5:21 pm

jacky4566 wrote:
Matt Cramer wrote:While you can run without it, adding a MAT sensor will allow a couple extra features like MAT timing retard. Plus it's handy to data log.
HFM5 brother! I am just installing one of these now.

Matts suggestion would only work in a blow through turbo setup. Most factory setups (At least Subaru) put the maf pre turbo.

But to answer your question. Yes hookup the MAT. Theoretically the MAF should compensate but realistically even OEM use MAT.

Tuning the curve will be different since the MAF will compensate somewhat but usually not enough. You will have to do lots of data logging in cold/hot days to figure out the true curve. I would start with a very mild or no curve and work from there.

Thanks... I'm using a new Bosch MAF 0 280 217 123 as fitted to Opel Corsa SB 1.4l SPI engines, also known here in Australia as the Holden Barina. My engine is a Rover Mini A+ 1310cc unit. It's a new unit. So I'll connect up it's temp sensor (Pin 1) instead of the GM MAT sensor I previously used in my SD setup as this would be a lot easier fabrication wise. I'll keep you posted.

jb007 · Post by **jb007** » Thu Jul 28, 2016 5:53 pm

subwoofer wrote:I think I can set up a scatter plot to find that function, will have to think a little bit about it. The curve should hopefully be the same for all HFM5s, so it is just a matter of finding it.

The HFM5 is a very user friendly piece of kit, as long as you stay away from oiled air filters and MAF cleaning concoctions they are accurate and reliable.

Thanks for your reply... couple of Q's

Are you talking about the temp-resistance of the Bosch MAF... if so this is it.

Code: Select all

Temperature-dependence R= f() of the temperature sensor 
C	-40	-30	-20	-10	0	10	20	30	40
k	39.26	22.96	13.85	8.609	5.499	3.604	2.420	1.662	1.166
C	50	60	70	80	90	100	110	120	130
r	835	609	452	340	261	202	159	127	102

I've been looking for my K&N filter I bought for this installation... looks like it's grown legs and runaway from home, maybe when I moved house recently, maybe it new it was no good for the MAF!
I guess the oil may contaminate the hot film sensor? I guess just a plain paper filter pod will do?

whittlebeast · Post by **whittlebeast** » Thu Jul 28, 2016 6:02 pm

I always mount a IAT, even if all I do is mount it very close to the air filter. That bit of info can be huge to figure out if the motor is sucking in extremely hot air.

Andy

jb007 · Post by **jb007** » Thu Jul 28, 2016 6:09 pm

whittlebeast wrote:I always mount a IAT, even if all I do is mount it very close to the air filter. That bit of info can be huge to figure out if the motor is sucking in extremely hot air.

Andy

Thanks Andy.. I wan't to use the seperate temp sensor that is built-in to the MAF, so I don't have to mount more a seperate IAT sensor. The temp sensor inside the MAF is not used by the MAF, it's there for end user use only. It' very convenient as it's measuring at the same physical location where the MAF sensor is also measuring.

Jim

jacky4566 · Post by **jacky4566** » Wed Aug 24, 2016 8:50 pm

Bump.

Was anyone able to find an OEM Correction table? Since this maf seems common in VW/ Opel/ Vauxhaul I'd like to know if they are using it as a scalar. Maybe they only use the internal MAT for emergencies/ overheating.
I am not familiar with VW. Is there any open source tuning software i could dig around with?

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