JDSPorsche rebuilt MAFs
08-16-2005, 02:19 PM
#1
Rennlist Member
Thread Starter
JDSPorsche rebuilt MAFs
Hi,
I'm delighted to announce that 928 International are now stocking my rebuilt exchange MAFs for the 928. They will hold a good stock of rebuilt units for fast delivery in the US.
These MAFs fit the 85-86 US early 32v, the Euro S2 84-86 and all S4, GT and GTS models.
Any car with more than around 80k miles is likely to have its performance degraded by the erosion of the platinum hot wire. For further details see the FAQ section of my website for MAFs.
The exchange price is dependant on receiving cores from you that are repairable. So the MAF should be mechanically complete, with no damaged castings, or damage to the hot wire venturi assembly inside the casting (broken hot wire is NOT a problem). Please do not remove the black cover as it is possible to cause damage in there. Damaged screens are not a problem.
I will continue to supply from my agent in NY, although his stock level is lower than that held by 928 Intl. The price is the same from either source - 350USD.
Thanks to all Rennlisters for their support in the past, and hopefully in the future !
Regards
I'm delighted to announce that 928 International are now stocking my rebuilt exchange MAFs for the 928. They will hold a good stock of rebuilt units for fast delivery in the US.
These MAFs fit the 85-86 US early 32v, the Euro S2 84-86 and all S4, GT and GTS models.
Any car with more than around 80k miles is likely to have its performance degraded by the erosion of the platinum hot wire. For further details see the FAQ section of my website for MAFs.
The exchange price is dependant on receiving cores from you that are repairable. So the MAF should be mechanically complete, with no damaged castings, or damage to the hot wire venturi assembly inside the casting (broken hot wire is NOT a problem). Please do not remove the black cover as it is possible to cause damage in there. Damaged screens are not a problem.
I will continue to supply from my agent in NY, although his stock level is lower than that held by 928 Intl. The price is the same from either source - 350USD.
Thanks to all Rennlisters for their support in the past, and hopefully in the future !
Regards
08-16-2005, 04:50 PM
#4
Rennlist Member
Good for you John..........California is probably the largest 928 market in the world. 
Now when are you going to expand to the 'Great White North'?
Testimonial..........my car now runs with a JDS rebuilt MAF and GT mapped eproms...........excellent results
Now when are you going to expand to the 'Great White North'?
Testimonial..........my car now runs with a JDS rebuilt MAF and GT mapped eproms...........excellent results
08-16-2005, 05:12 PM
#6
The Parts Whisperer
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Originally Posted by the flyin' scotsman
Good for you John..........California is probably the largest 928 market in the world.
:
:
California 4461
Florida 1526
Texas 1402
New York 1278
Canada 786
08-17-2005, 02:16 AM
#7
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Listen- its rare when you get this sort of attention from someone when it comes to automotive parts- If you deal with Speake/ or 928 Intl. you won't be unhappy.
-I had all sorts of trouble getting my car to run right [see my various "rough running" threads]. Well, I've pretty much worked it out, and now have a car that runs great. One of the things I did was replace the MAF, since it was obvious from the black marks on the wall of my garage [Borla exhaust = pointed at the wall] that the car was running rich. I emailed John about all my problems...and not only did he take the time to help me work out my problem...
He went into his garage in England and pulled the part from his own car and sent it to me!
That MAF change and a few other various changes later I'm in good shape. My tires are getting worn out quickly-
This guy really knows what he's doing: MAF's are pretty standard- owners of other Porsche types should know about this service.
N!
-I had all sorts of trouble getting my car to run right [see my various "rough running" threads]. Well, I've pretty much worked it out, and now have a car that runs great. One of the things I did was replace the MAF, since it was obvious from the black marks on the wall of my garage [Borla exhaust = pointed at the wall] that the car was running rich. I emailed John about all my problems...and not only did he take the time to help me work out my problem...
He went into his garage in England and pulled the part from his own car and sent it to me!
That MAF change and a few other various changes later I'm in good shape. My tires are getting worn out quickly-
This guy really knows what he's doing: MAF's are pretty standard- owners of other Porsche types should know about this service.
N!
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08-17-2005, 06:30 AM
#8
Rennlist Member
Thread Starter
Hi Borland,
From experience, I would say that any car with over 80k miles has a significantly aged MAF. But it depends on the type of use the car has had during those miles. If many short jounreys - say less than 25 miles, then this will age the MAF relatively quickly.
On the other hand , I've seen a car here with 220k miles used mostly for long motorway jounreys, the MAF was bad, but more like a typical 100k mile car.
Many owners have never driven another 928 that is running properly, so they have no point of reference. They usually are pretty amazed when they have a rebuilt MAF fitted !
I charge a core fee of 100USD on your old MAF. I don't know what the policy of 928Intl. is on this point. If you deal direct to me, then I can make a calibration check and report back for a nominal charge, without you buying a rebuilt one.
Any cores returned to me by 928Intl are unlikely to be marked with the customer's name.
Regards
From experience, I would say that any car with over 80k miles has a significantly aged MAF. But it depends on the type of use the car has had during those miles. If many short jounreys - say less than 25 miles, then this will age the MAF relatively quickly.
On the other hand , I've seen a car here with 220k miles used mostly for long motorway jounreys, the MAF was bad, but more like a typical 100k mile car.
Many owners have never driven another 928 that is running properly, so they have no point of reference. They usually are pretty amazed when they have a rebuilt MAF fitted !
I charge a core fee of 100USD on your old MAF. I don't know what the policy of 928Intl. is on this point. If you deal direct to me, then I can make a calibration check and report back for a nominal charge, without you buying a rebuilt one.
Any cores returned to me by 928Intl are unlikely to be marked with the customer's name.
Regards
08-17-2005, 06:31 AM
#9
Rennlist Member
Thread Starter
Hi Normy,
Glad to hear your car's running strong ! You were an early customer....must be over 2 years ago !
I've rebuilt about 300 MAFs since then...
Glad to hear your car's running strong ! You were an early customer....must be over 2 years ago !
I've rebuilt about 300 MAFs since then...
08-18-2005, 06:05 AM
#11
Rennlist Member
Thread Starter
Hi Borland,
I can assure you that in my experience the majority of MAFs I receive that are well out of acceptable limits on car performance are in the 80-100k miles range.
I stated that the 220k miles was the exception.
Burn off occurrs at operating temperature and if the rpm have been above 2000rpm at any point previously in the drive, not just at switch off.
The resistance of 4 ohms isn't the resistance of the hot wire itself. The measurements in the WSM are just for checking for gross MAF failure. The absolute resistance isn't important. Each MAF is individually calibrated to take account of all the tolerances in the various component parts.
The O2 loop will compensate for moderate MAF ageing, and this works well at cruise. But as soon as you snap open the throttle, or get to WOT at 2/3 open throttle, then the system goes off loop to allow the necessary enrichment. At that point the fuelling is totally dependant on the accuracy of the MAF voltage versus airflow. MAFs age "weak" so throttle response and max power suffer.
Anyway you seem happy with your MAF....
Regards
I can assure you that in my experience the majority of MAFs I receive that are well out of acceptable limits on car performance are in the 80-100k miles range.
I stated that the 220k miles was the exception.
Burn off occurrs at operating temperature and if the rpm have been above 2000rpm at any point previously in the drive, not just at switch off.
The resistance of 4 ohms isn't the resistance of the hot wire itself. The measurements in the WSM are just for checking for gross MAF failure. The absolute resistance isn't important. Each MAF is individually calibrated to take account of all the tolerances in the various component parts.
The O2 loop will compensate for moderate MAF ageing, and this works well at cruise. But as soon as you snap open the throttle, or get to WOT at 2/3 open throttle, then the system goes off loop to allow the necessary enrichment. At that point the fuelling is totally dependant on the accuracy of the MAF voltage versus airflow. MAFs age "weak" so throttle response and max power suffer.
Anyway you seem happy with your MAF....
Regards
08-18-2005, 02:16 PM
#12
Rennlist Member
Thread Starter
Hi Borland,
Because of the high accuracy required of the MAF output voltage versus airmass (about 1% or better) even a diagnsotic tester such as the Spanner can't help much.
Fault conditions in the fuel injection system and its sensors are logged by the LH and EZK ECUs. The diagnostic tester recovers the stored fault codes. There is one code for MAf failure - this is when the output voltage at idle is so low (very badly aged or no voltage at all) that the voltage output from the MAF at idle is "off the fuel map".
Normally at idle, a 928 MAf should give of the order of 2.7v output. When this voltage drops below about 2.3v a fault code is stored, and also the car goes into the same limp home mode as is triggered by a MAF disconnection.
On the other hand, the LH ECU is incapable of detecting if the volatge is too high for any reason. Many early 928 MAFs had a Bosch design error, which results in thermal runaway. The output voltage goes high, and the hot wire can often be seen to be glowing orange whenever the engine runs. Lots of black smoke ! But no fault code is recorded.
Although the Achilles Heal of the Hot wire MAF is the errosion of the wire due to the necessary burn off cycle, they have proven to be much longer lived than their successor, the platinum film air mass sensor, as fitted to Boxsters, 993, 996 etc and most modern cars. These are faliing at low miilages, (around 60k or less), and are not rebuildable.
Regards
Because of the high accuracy required of the MAF output voltage versus airmass (about 1% or better) even a diagnsotic tester such as the Spanner can't help much.
Fault conditions in the fuel injection system and its sensors are logged by the LH and EZK ECUs. The diagnostic tester recovers the stored fault codes. There is one code for MAf failure - this is when the output voltage at idle is so low (very badly aged or no voltage at all) that the voltage output from the MAF at idle is "off the fuel map".
Normally at idle, a 928 MAf should give of the order of 2.7v output. When this voltage drops below about 2.3v a fault code is stored, and also the car goes into the same limp home mode as is triggered by a MAF disconnection.
On the other hand, the LH ECU is incapable of detecting if the volatge is too high for any reason. Many early 928 MAFs had a Bosch design error, which results in thermal runaway. The output voltage goes high, and the hot wire can often be seen to be glowing orange whenever the engine runs. Lots of black smoke ! But no fault code is recorded.
Although the Achilles Heal of the Hot wire MAF is the errosion of the wire due to the necessary burn off cycle, they have proven to be much longer lived than their successor, the platinum film air mass sensor, as fitted to Boxsters, 993, 996 etc and most modern cars. These are faliing at low miilages, (around 60k or less), and are not rebuildable.
Regards
08-18-2005, 03:14 PM
#13
Originally Posted by John Speake
Although the Achilles Heal of the Hot wire MAF is the errosion of the wire due to the necessary burn off cycle, they have proven to be much longer lived than their successor, the platinum film air mass sensor, as fitted to Boxsters, 993, 996 etc and most modern cars. These are faliing at low miilages, (around 60k or less), and are not rebuildable.
I was told the platin film of the HFM5 can be cleaned in an "ultrasounds bath", true or false ?
08-18-2005, 04:57 PM
#14
Rennlist Member
Thread Starter
Hi Thom,
I don't know the answer to that, but I have a suspicion you do ? Bear in mind the HFM5 is made in much larger quantities than the 928 MAF ever was.
I've heard that cleaning the platinum film in these sensors can sometimes give a short term improvement. But it doesn't always last.
Regards
I don't know the answer to that, but I have a suspicion you do ? Bear in mind the HFM5 is made in much larger quantities than the 928 MAF ever was.
I've heard that cleaning the platinum film in these sensors can sometimes give a short term improvement. But it doesn't always last.
Regards
