12v or 5v MAF?
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12v or 5v MAF?
Hi guys,
Quick question: What is the upper voltage limit on the factroy MAF sensor on a 996tt. Is it 5v? Or is it 12v? IIRC, the modded 993tt i've tested went over 5v under heavy load. I have not been able to see anything over 5v with our car, suggesting that max value is indeed 5v. But our car is running stock turbos so I can't be sure. Further confusing matters is that there is both a 5v and a 12v wire going into the MAF sensor. Perhaps the 12v is for the MAF and the 5v for the IAT? Just guessing here....
Thanks,
shiv
Quick question: What is the upper voltage limit on the factroy MAF sensor on a 996tt. Is it 5v? Or is it 12v? IIRC, the modded 993tt i've tested went over 5v under heavy load. I have not been able to see anything over 5v with our car, suggesting that max value is indeed 5v. But our car is running stock turbos so I can't be sure. Further confusing matters is that there is both a 5v and a 12v wire going into the MAF sensor. Perhaps the 12v is for the MAF and the 5v for the IAT? Just guessing here....
Thanks,
shiv
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I can't believe Shiv from vishnu tuning is actually posting here! You made a real nice turbo kit for the GC8 RS. You definately turn out a quality product! Nice to see ya here. Sorry I don't know the answer to that question I am sure Kevin from UMW will chime in
BTW are you tuning 996TT now?
BTW are you tuning 996TT now?
#3
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Originally Posted by shiv@vishnu
I have not been able to see anything over 5v with our car, suggesting that max value is indeed 5v.
Originally Posted by shiv@vishnu
Further confusing matters is that there is both a 5v and a 12v wire going into the MAF sensor. Perhaps the 12v is for the MAF and the 5v for the IAT?
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Hi,
In addition to what JasonAndreas says, if you set a custom EFI (and if you ask for voltage, I guess you do) you should think about having another temp sensor (like the basic Bosch in copper one - don't have the ref here) that has a more linear response than the factory NCT. I'v had issues with that.
Cheers
In addition to what JasonAndreas says, if you set a custom EFI (and if you ask for voltage, I guess you do) you should think about having another temp sensor (like the basic Bosch in copper one - don't have the ref here) that has a more linear response than the factory NCT. I'v had issues with that.
Cheers
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Jason- Thanks for the info. That make a lot more sense. So those 500+hp setups basically max the MAF at 5v? Or do they swap out a larger diameter MAF housing or install a new MAF?
IrocMan- You hit it right on the head We're currently implementing our PROcede computer on our car. Been using it in the new twin turbo BMW 335 for some time now. And so far, things are looking equally nice with the 996tt. The MAF limitation took us by surprise though.
cpu77- Thanks for the kind words. And yes, we will have a tuning option soon for the 996tt/997tt
Cheers.,
shiv
www.vishnutuning.com
IrocMan- You hit it right on the head We're currently implementing our PROcede computer on our car. Been using it in the new twin turbo BMW 335 for some time now. And so far, things are looking equally nice with the 996tt. The MAF limitation took us by surprise though.
cpu77- Thanks for the kind words. And yes, we will have a tuning option soon for the 996tt/997tt
Cheers.,
shiv
www.vishnutuning.com
#6
Most just max out the stock MAF (which is weak and commonly blows). Some are using a larger diameter MAF housing, and there are two different setups using a different MAF sourced from another vehicle. I know that one in use is made by Hitachi, but on at least one car it creates a lot of CELs. A new MAF solution is ideal.
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Originally Posted by roadsterdoc
Most just max out the stock MAF (which is weak and commonly blows). Some are using a larger diameter MAF housing, and there are two different setups using a different MAF sourced from another vehicle. I know that one in use is made by Hitachi, but on at least one car it creates a lot of CELs. A new MAF solution is ideal.
-shiv
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#8
Originally Posted by shiv@vishnu
Thanks for the info. Very helpful. What about a T-MAP sensor conversion? Seems like it would be a good fit in a car that constantly runs closed loop wideband control.
-shiv
-shiv
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The ME7.8 has the ability to do pressure sensing over throttle position, but only uses it when the MAF is broken. And when that occurs, everything else is in limp home mode, the ABS/PSM lights are on.
The stock MAF makes it's peak voltage at about 51lbs/min, with these engines having an efficiency of about 9.5hp/lb/min of air, you will be seeing around 490HP or so. You need to put a bigger MAF housing.
The problem with stretching the MAF capability is that the calibration will need to be boost specific or only tuned at the particular range where ou want to run the car.
Some tuners do use the O2 sensors as their primary feedback sensor because they are beyond the limits of the MAF however it also has its complications on high HP engines since the tubing will be wider than stock and the sensor will not read very accurately.
All the Info comes from a very knowledgeable tuner who has been doing this succesfully for a while now.
The stock MAF makes it's peak voltage at about 51lbs/min, with these engines having an efficiency of about 9.5hp/lb/min of air, you will be seeing around 490HP or so. You need to put a bigger MAF housing.
The problem with stretching the MAF capability is that the calibration will need to be boost specific or only tuned at the particular range where ou want to run the car.
Some tuners do use the O2 sensors as their primary feedback sensor because they are beyond the limits of the MAF however it also has its complications on high HP engines since the tubing will be wider than stock and the sensor will not read very accurately.
All the Info comes from a very knowledgeable tuner who has been doing this succesfully for a while now.
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Originally Posted by ebaker
I believe the 996 TT switches to open loop under most full load situations.
shiv
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Originally Posted by Jean
The ME7.8 has the ability to do pressure sensing over throttle position, but only uses it when the MAF is broken. And when that occurs, everything else is in limp home mode, the ABS/PSM lights are on.
The stock MAF makes it's peak voltage at about 51lbs/min, with these engines having an efficiency of about 9.5hp/lb/min of air, you will be seeing around 490HP or so. You need to put a bigger MAF housing.
The problem with stretching the MAF capability is that the calibration will need to be boost specific or only tuned at the particular range where ou want to run the car.
Some tuners do use the O2 sensors as their primary feedback sensor because they are beyond the limits of the MAF however it also has its complications on high HP engines since the tubing will be wider than stock and the sensor will not read very accurately.
All the Info comes from a very knowledgeable tuner who has been doing this succesfully for a while now.
The stock MAF makes it's peak voltage at about 51lbs/min, with these engines having an efficiency of about 9.5hp/lb/min of air, you will be seeing around 490HP or so. You need to put a bigger MAF housing.
The problem with stretching the MAF capability is that the calibration will need to be boost specific or only tuned at the particular range where ou want to run the car.
Some tuners do use the O2 sensors as their primary feedback sensor because they are beyond the limits of the MAF however it also has its complications on high HP engines since the tubing will be wider than stock and the sensor will not read very accurately.
All the Info comes from a very knowledgeable tuner who has been doing this succesfully for a while now.
-shiv
#12
Very interesting info. There must be another factor than just the MAP as adding a resistor to the MAF signal line appears to work. If the suggested MAP based overboost protection is functioning, it would need to only work when the MAF is at max voltage, otherwise reducing the MAF signal would have no effect.
Of course I could be wrong.
Steve
Of course I could be wrong.
Steve
#13
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Originally Posted by Jean
...
Some tuners do use the O2 sensors as their primary feedback sensor because they are beyond the limits of the MAF however it also has its complications on high HP engines since the tubing will be wider than stock and the sensor will not read very accurately.
...
Some tuners do use the O2 sensors as their primary feedback sensor because they are beyond the limits of the MAF however it also has its complications on high HP engines since the tubing will be wider than stock and the sensor will not read very accurately.
...
I definitely agree. This was used a lot in Formula 1 and Supertourism in France when I still was an intern, a long time ago.
A while ago also -but mostly because of money- my first turbo engine only had a WB O2 sensor signal mapped to a [0-5V] as a compensation of the basic TPS/RPM map. It was cheap and worked pretty well, later we added exhaust temperature.