twin MAF's..is it possible?
05-07-2004, 12:52 PM
#21
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Originally Posted by rons 00z
there is no for sure of how much air is going through the bypass because it's not being measured so your going to have inaccurate readings. hell if you ask me hook them up in series find out how much of an ohm increse you get then use what ever ohm resistor(s) to normal it out. now from what i understand the maf is a heated resistor so if there is any frequency involved it's just a carrier and most likely wont be affected. i dont think there is a frequency though because it's a dc circuit but i could be wrong.
This i do not agree with
1. if the air bypass is constructed correctly the bypass should carry a very close to constant percentage of the air under all conditions.
2. it would not be any harded to recal in the pcm than running 2 MAF's
3. The problem (as I understand it) is that the siginal from the MAF max's out so no matter what you do you still have to recall the pcm ie 100% sig => 140% (or what ever) of air flow.
4. this tech is used in industrial processes (not often because I would normaly just reprogram the PLC and use a larger available sensor of the proper size) when you are in a tight spot.
the key to this approach is that the bypass would carry a nearly fixed % of the air flow causing the original MAF to read like one that was that fixed % larger across its intire signial swing (reguardless of the type of encoding used by the sensor ie resistance or freq.).
this is all IMO
M_T_0
05-07-2004, 01:02 PM
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Originally Posted by lcvette
i tried a search on several similar topics, and got nothing... any suggestions on what to use as search criteria?
on the bypass tube, this would be difficult because unlike measuring metered air at a set vacuum/pressure the characteristics of the bypass tube would vary greatly. and knowing at what exact point to get the 40% airflow difference and have the MAF read accurately still would be a trial and error method that would take a very long time to pin down..this is all speculation though.. perhaps 40%@28 inches of water as measured on a flow bench could be correct, just don't know!
possibly enlarging the actual size of the MAF housing allowing a high volume of air through and simply rescaling the other tables to interperet the input from the MAF would work.. much like using a resistor, except that by enlarging the housing, you would essentially be slowing the airflow rate across the MAF wires with the same volume still being ingested by the engine. this would require numerous dyno runs to get the AFR correct with the other tables in the PCM and make sure that everything was playing well together..lol oh well, any word from Harlan yet? dying to find out what he did and any advise he might be willing to share on it! keep posting guys.. this is great stuff!
Chris
on the bypass tube, this would be difficult because unlike measuring metered air at a set vacuum/pressure the characteristics of the bypass tube would vary greatly. and knowing at what exact point to get the 40% airflow difference and have the MAF read accurately still would be a trial and error method that would take a very long time to pin down..this is all speculation though.. perhaps 40%@28 inches of water as measured on a flow bench could be correct, just don't know!
possibly enlarging the actual size of the MAF housing allowing a high volume of air through and simply rescaling the other tables to interperet the input from the MAF would work.. much like using a resistor, except that by enlarging the housing, you would essentially be slowing the airflow rate across the MAF wires with the same volume still being ingested by the engine. this would require numerous dyno runs to get the AFR correct with the other tables in the PCM and make sure that everything was playing well together..lol oh well, any word from Harlan yet? dying to find out what he did and any advise he might be willing to share on it! keep posting guys.. this is great stuff!
Chris
just IMO
M_T_0
05-07-2004, 03:23 PM
#23
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Originally Posted by M_T_0
40% of what the MAF is flowing should be 40% at 10 cfm or 900 cfm, its 40% and should be consistant and would reqire no more reprograming or testing than any of the rest of the things discussed. whats more the % is not important you do the mod put on dyno and correct for AFR, Testing done!
just IMO
M_T_0
just IMO
M_T_0
I'd try to keep the section with the bypass and MAF as close to symmetrical as possible. You could basically cut the signal in half with that setup.
I'd still rather try to get two MAFs to work so that all the air was actually being read though.
05-07-2004, 04:06 PM
#24
There is one unit, an Apexi Super Air/Fuel Controller (SAFC) that has the capability to read 2 maf sensors. When setting it up, you choose whether you want to add the readings or average them.
Some of the other stuff it can do is alter the signal by a percentage based on combination of rpm and throttle position.
I never could get it to work on my setup though. One of the setup options was type of maf sensor (hot wire, frequency, etc.) Another setup was to choose a number between 0 and 40+, which mapped to specific car models in the instructions... And the f-bodies are not listed in the instructions. I tried various choices, and it never would forward a signal that the pcm would recognize. (might have been a bad unit - I sent it back for warranty in January, and still don't have a replacement)
Some of the other stuff it can do is alter the signal by a percentage based on combination of rpm and throttle position.
I never could get it to work on my setup though. One of the setup options was type of maf sensor (hot wire, frequency, etc.) Another setup was to choose a number between 0 and 40+, which mapped to specific car models in the instructions... And the f-bodies are not listed in the instructions. I tried various choices, and it never would forward a signal that the pcm would recognize. (might have been a bad unit - I sent it back for warranty in January, and still don't have a replacement)
05-07-2004, 08:28 PM
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interesting, anyone know about how much this SAFC costs? would be very interested in researching it some more and maybe talking to the people who manufacture it to see if there is some way for it to jive with the GM model PCMs. i think using twin MAF's is gonna be the way to go in the near future once a fairly simple and inexpensive averager is produced and it is more broadly publicized on the forums how to recaibrate the PCM accordingly. should be a basic recalibration once its cracked and dialed in. any word from Harlan yet..?
Chris
Chris
05-09-2004, 08:10 AM
#27
I bought mine on ebay for right at $300 from a seller that moves a lot of them.
When I had some issues with it, I discovered that Apexi doesn't recognize this guy as an authorized retailer. (and they knew exactly who he was too...)
The going retail is closer to $500 I believe.
You can trick it to be boost referenced, if you supply a signal to it on the tps input wire...
When I had some issues with it, I discovered that Apexi doesn't recognize this guy as an authorized retailer. (and they knew exactly who he was too...)
The going retail is closer to $500 I believe.
You can trick it to be boost referenced, if you supply a signal to it on the tps input wire...
05-09-2004, 11:48 PM
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Originally Posted by John_D.
I bought mine on ebay for right at $300 from a seller that moves a lot of them.
When I had some issues with it, I discovered that Apexi doesn't recognize this guy as an authorized retailer. (and they knew exactly who he was too...)
The going retail is closer to $500 I believe.
You can trick it to be boost referenced, if you supply a signal to it on the tps input wire...
When I had some issues with it, I discovered that Apexi doesn't recognize this guy as an authorized retailer. (and they knew exactly who he was too...)
The going retail is closer to $500 I believe.
You can trick it to be boost referenced, if you supply a signal to it on the tps input wire...
I guess that I missed something, if you used this device you would have to mount a second MAF right? how is that easier than just putting in a bypass?
and no i dont think that the bypass plumbing would be critical, if it is not perfect that is where calabration comes in (no sensors have perfect responce curves anyway that is why they have to be calabrated).
M_T_0
05-11-2004, 09:29 AM
#29
Originally Posted by M_T_0
I guess that I missed something, if you used this device you would have to mount a second MAF right?
I only posted about the Apexi because the thread was about twin mafs, and somebody asked if there was a way to use them. I knew the Apexi supports that, so thought folks might be interested. I hadn't even really thought about the bypass comments yet when I posted that...
05-11-2004, 11:07 AM
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Originally Posted by MIGHTYMOUSE
guys should try the search this topic comes up in a big way about every 6 months.
i run 0 maf's and it works good too
i run 0 maf's and it works good too
Ding ding ding.
05-24-2004, 08:09 PM
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was wondering if Harlen had been back yet.. was hoping to get some input from him on this topic.. if your out there.. if ya have a second, i would really appreciate getting some info from ya!
thanks inadvance,
Chris
thanks inadvance,
Chris
