06 Vette MAF tuning with a SuperCharger

[VetteNut]

Probably a dumb question but do Forced Induction applicaitons change the way one would go about tuning the MAF for AFR?

If it works the same, want to make sure I have this right.

• Set the PE table to a divisor that will command a specific AFR
• Log for MAF Hi and Lo and MAF hi and lo AFR Error
• For each fo the hi/lo tables, copy and paste the AFR Error using Multiply by %
• Continue until MAF HI and Lo are 0'd out. ??

Am I close?

Thanks

[5_Liter_Eater]

You left out putting it in open loop but the rest is spot on. The only other thing to think about is if you have enough boost to over-run the MAF table (>512 g/s) then you can either go with a 2 or 3 bar SD tune (actually I don't even know if that is available for our vettes) or determine the RPM that the MAF runs out at and use the PE to add additional fuel beyond that.

[RWTD]

Or get yourself a new slot-style sensor from a LS7/LS3, and get an aftermarket housing to stick it in (at least 4"). This should yield you more headroom, without any loss of drivability.

[5_Liter_Eater]

Sorry but thats wrong. Use any MAF you like, a blown LS2 will run out of MAF, and when I say run out of MAF I mean it will flow more than 512 g/s. So you can stick the slot style sensor in a coffee can with the bottom cut off and it may only read 6000 Hz at redline but it will still run past 512 g/s which is where the MAF table ends flow-wise. The flow is the hard limit, not the Hz.

[EC_Tune]

^^ Yuppers. Don't know why GM limited themselves so harshly... LOL:>

[Blades]

The ZR1 developers were (are) probably asking that same question. Same deal with the 60lb inj limit. Whats the next limit of the MAF? 768, 1024? Why impose a limit that could be realistically reached anyways? What do you lose by upping the limit, resolution? How are the MAF readings translated into fueling anyways?

[ScottBeer]

Sorry but thats wrong. Use any MAF you like, a blown LS2 will run out of MAF, and when I say run out of MAF I mean it will flow more than 512 g/s. So you can stick the slot style sensor in a coffee can with the bottom cut off and it may only read 6000 Hz at redline but it will still run past 512 g/s which is where the MAF table ends flow-wise. The flow is the hard limit, not the Hz.

I am relatively new to GM products, but as I understand it, there are three potential problems with GM MAF based engine management systems. The actual maf hardware, the ability to use flow numbers exceding 512 g/s and the Hz limit useable by the VCM. It gets better, some applications have all of these problems and some do not.

I would like to know if you can scale everything down and still maintain an engineered calibration on late model GM applications.

In the Ford tuning world, we simply followed Ford's own calibration technique using the Ford GT (GT 40) as our example (many of us had been using same technique years before the GT 40)

I have seen high power GM applications using the Lingenfelter MAF and briefly thought about how they dealt with the actual air flow values in their calibration. I assumed that you could , as RWTD suggested, increase the ID of the MAF housing itself, thus extending the dynamic range of the MAF sensor. You would then scale the injector flow rates, the MAF transfer function as well as some other calculations affecting VE calculations. Everything should line up to create proper load, VE and torque calculations if done properly.

I have heard about many GM "tuners", reverting to speed density tuning on these MAF equipped vehicles and I can't help but think it would be a "hack" approach. But I am going to have to learn more about these cars before I make any harsh judgements on other people's tuning approaches on GM vehicles.

[5_Liter_Eater]

Here's a current thread about fudging the numbers to get under the 512 g/s limit. http://www.hptuners.com/forum/showthread.php?t=14506

More often than not when people talk about maxing out the MAF they mean they are flowing more than 512 g/s, not that they have run out of MAF frequency. So larger diameter bores may cause the frequency to go down but if you use the correct fuel injector numbers then you'll just hit 512 g/s at say 6000 Hz rather than 12000 Hz.

The above thread talks about doing what you're suggesting. Fudging the injector numbers to be less so you need to lower the airflow tables to maintain the right AFR. By doing this you can expand the range but you lose resolution (squeezing say 600 g/s into 512) which isn't a huge deal. It just gets hard to think about things when the numbers you're looking at are 'fake' but it is definitely a workaround.

Another workaround, particularly for centrifugal blowers is to find the RPM at which you run out of MAF and use the PE table to add additional fuel past this RPM. This is not a very good solution because you're flying blind. You may get it spot on on the dyno but if the temp drops significantly then you're now seeing more boost and have no way of accounting for it.

When people talk about SD getting past this barrier they are usually referring to the OS enhancements that HPT has. For certain PCM's you can license HPT's custom 2 or 3 bar SD OS. These enhancements expand the VE tables past 105 kPa and add things like boost enrichment. Basically expanding the PCM's tables to understand boost. All you need to do is install a 2 or 3 BAR MAP sensor. This is ideal but not available for some PCM's.

HTH

[Mobile Chassis Dyno]

Bill,

I would like to chat with you more on this sometime if you are interested.

[5_Liter_Eater]

Sure, PM me your info and I'll give you a shout this afternoon.