MAF Delete???
TECH Addict
Joined: Jun 2005
Posts: 2,660
Likes: 14
From: England
Well the MAF (Mass Air Flow meter) measure the volume of air intake and tells the PCM so it can add appropriate fuel.
What some people do is swap to a Speed Densisty (SD) tune where pre-defined tables are programmed in to tell the computer what the airflow should be at any given rpm/throttle input.
This can often be an easier form of tuning on a more wild setup but in many ways it's also less accurate. Also it won't reflect changes made to the intake, so if you get and SD tune for Lt's exhaust and later on add a lid or intake manifold you WILL need to saccount for the extra air flow. On a MAF setup you wouldn't as the MAF would be able to cater for such changes.
With a MAF you probably won't need to tune until you mess with the heads or cam.
I'd only go SD if you a specific reason to do so.
What some people do is swap to a Speed Densisty (SD) tune where pre-defined tables are programmed in to tell the computer what the airflow should be at any given rpm/throttle input.
This can often be an easier form of tuning on a more wild setup but in many ways it's also less accurate. Also it won't reflect changes made to the intake, so if you get and SD tune for Lt's exhaust and later on add a lid or intake manifold you WILL need to saccount for the extra air flow. On a MAF setup you wouldn't as the MAF would be able to cater for such changes.
With a MAF you probably won't need to tune until you mess with the heads or cam.
I'd only go SD if you a specific reason to do so.
And once you go SD, do NOT add a dry nitrous kit unless you have it trigger something in the PCM and then tune for it (ground out the CTS and use those coolant tables to tune for spray, etc.)
Honestly, it takes a bit more to tune a SD (Speed Density) setup and you practically have to have 4 tunes. One for each season of driving. I finally said to hell with it and put my MAF back in and flashed the stock tune in EFI Live and re-tuned from there.
Originally Posted by lsx24
The only advantage to an SD tune is it removes the restriction of having a certain diameter MAF sensor. But there are a lot of disadvantages.
Lots of disadvantages
1. ??
2. ??
3. ??
4. ??
Ok maybe not LOTS, but here are the few I know of:
1). More expensive. Regardless of what someone may say, SD tune requires more amount of time to tune. This extra work usually leads to more money, unless you are knowledgable and courageous enough to do it yourself.
2). Harder to find a SD tuner. I haven't tried myself, so it may be easier than I thought, but it seems like it would be harder to find an SD tuner in the area, at least as much as regular tuners. Ymmv. Maybe they are the same.
3). Elevation changes cause poor running. I have heard rumors that weather an elevation changes may have negative effects on an SD tune. Is there any truth to this? I hear it often.
4). Change in parts requires a retune. Although somewhat similar to MAF tunes, a change in a part with an SD tune requires a new tune. Much more sensitive to changes than MAF tunes.
1). More expensive. Regardless of what someone may say, SD tune requires more amount of time to tune. This extra work usually leads to more money, unless you are knowledgable and courageous enough to do it yourself.
2). Harder to find a SD tuner. I haven't tried myself, so it may be easier than I thought, but it seems like it would be harder to find an SD tuner in the area, at least as much as regular tuners. Ymmv. Maybe they are the same.
3). Elevation changes cause poor running. I have heard rumors that weather an elevation changes may have negative effects on an SD tune. Is there any truth to this? I hear it often.
4). Change in parts requires a retune. Although somewhat similar to MAF tunes, a change in a part with an SD tune requires a new tune. Much more sensitive to changes than MAF tunes.
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It isn't as big of a PITA as people would make it out to be...honestly, I think people are scared of the unknown. If you know what you are doing, or are willing to spend time learning and trial and erroring (yeah, not a word, but gets the point across), you can end up with a very stable tune with great driving characteristics. Mine's been a daily driven, SD tuned, and open loop (no O2 sensors) car for nearly two years now...for me, it is just easier to do it this way.
TECH Senior Member
Joined: Apr 2002
Posts: 6,080
Likes: 17
From: So.Cal.
I have been running OLSD, and I have observed the following:
a. it is as easy as driving your car if you have a suitable software tool.
b. elevation/weather seem to have no effect (the VE table units are g.K/kPa), at least for me (40'-4000', 32F-100F).
c. you never have to deal with a failed/dirty/oily MAF sensor.
d. yes, when you change parts, you may have to retune (which you should anyway).
e. car runs from the Low Octane timing table unless you flash in a custom OS.
f. OLSD allows you to dial in VE table, which means your actual AFR will exactly match your commanded AFR; this is good because you now know what you're doing (save your motor from lean destruction).
g. a dialed in VE table can then be used to dial in MAF table, which means you can decide to run with a MAF if you wish.
h. neither SD or MAF is wrong, you just decide which is best for you.
i. SD is better suited for the DIY self-tuner who owns suitable software.
a. it is as easy as driving your car if you have a suitable software tool.
b. elevation/weather seem to have no effect (the VE table units are g.K/kPa), at least for me (40'-4000', 32F-100F).
c. you never have to deal with a failed/dirty/oily MAF sensor.
d. yes, when you change parts, you may have to retune (which you should anyway).
e. car runs from the Low Octane timing table unless you flash in a custom OS.
f. OLSD allows you to dial in VE table, which means your actual AFR will exactly match your commanded AFR; this is good because you now know what you're doing (save your motor from lean destruction).
g. a dialed in VE table can then be used to dial in MAF table, which means you can decide to run with a MAF if you wish.
h. neither SD or MAF is wrong, you just decide which is best for you.
i. SD is better suited for the DIY self-tuner who owns suitable software.
Last edited by joecar; Feb 26, 2007 at 03:25 PM. Reason: Typos...
Originally Posted by joecar
I have been running OLSD, and I have observed the following:
a. it is as easy as driving you car if you have a suitable software tool.
b. elevation/weather seem to have no effect (the VE table units are g.K/kPa), at least from me (40'-4000', 32F-100F).
c. you never have to deal with a failed/dirty/oily MAF sensor.
d. yes, when you change parts, you may have to retune (which you should anyway).
e. car runs from the Low Octane timing table unless you flash in a custom OS.
f. OLSD allows you to dial in VE table, which means your actual AFR will exactly match your commanded AFR; this is good because you now know what you're doing (save your motor from lean destruction).
g. a dialed in VE table can then be used to dial in MAF table, which means you can decide to run with a MAF if you wish.
h. neither SD or MAF is wrong, you just decide which is best for you.
i. SD is better suited for the DIY self-tuner who owns suitable software.
a. it is as easy as driving you car if you have a suitable software tool.
b. elevation/weather seem to have no effect (the VE table units are g.K/kPa), at least from me (40'-4000', 32F-100F).
c. you never have to deal with a failed/dirty/oily MAF sensor.
d. yes, when you change parts, you may have to retune (which you should anyway).
e. car runs from the Low Octane timing table unless you flash in a custom OS.
f. OLSD allows you to dial in VE table, which means your actual AFR will exactly match your commanded AFR; this is good because you now know what you're doing (save your motor from lean destruction).
g. a dialed in VE table can then be used to dial in MAF table, which means you can decide to run with a MAF if you wish.
h. neither SD or MAF is wrong, you just decide which is best for you.
i. SD is better suited for the DIY self-tuner who owns suitable software.
