1 Bar Maf tuning a 2 bar situation

[Bill@HPTuners]

It comes up alot that people insist on tuning a blown or turbo'd application while still using the maf and although you can tune this way there are some drawbacks when doing so & there are some advantages to going SD instead.

Advantages of HPTuners 2/3 bar Custom Operating systems

• Low cost (2) credits & the price of a 2 or 3 bar Map sensor to be up and running
• Full use of both the High & Low Octane tables even with no maf sensor in place
• Real Time Tuning Available(Most Calibrations)
• Extends VE table from 105 kpa all the way to either 210kpa or 315kpa for LS1 applications
• Adds a boost enrichment table for different boost levels-this is great when you want to run 6psi on the street but 10psi at the track as you can set your boost enrichment table to add a bit more fuel for that 10psi setting without the need to reflash again for the changes.

Disadvantages of using MAF in boosted applications

• Your fueling will be completely wrong under many conditions because once you max the maf table the computer looks to the other fueling tables & pretty much is just guessing at that point. Fueling isnt always just rpm dependant so when you've only got 1 wot fueling table(power enrichement) which is done by rpm only your basically guessing at what # to put in. This also limits you in the fact that you can't have variable boost levels...once the maf maxes it maxes but you've only got one pe table thats only rpm dependant rather then boost dependant so if your commanding 11.5:1 at 5500 rpms on 5psi its still going to command 11.5:1 at 5500 on 10psi yet your flowing a ton more air at that point meaning your going to go leaner at 10psi more than likely.
• Unless you opt for the MAF RTT custom 1 bar OS you probably don't have access to Real Time Tuning and if you did consider the 1 bar maf OS your only now 1 credit from the 2 bar custom SD OS and doing it the right way.
• No way to change boost levels without reflashing in a different tune

Here's a Small summation done by RedHardSupra on this matter http://tuning.wikispaces.com/tuning+Forced+Induction

Bottom line is you've probably just spent $4000-$7000 on that new blower or turbo it would be wise to use 2 credits & $50 for a 2 bar map sensor & 2 bar SD custom Operating system.

[Russ K]

A maf tune will work fine on a low boost application 4-6 psi, IF your maf is not maxed out. It is alot easier to tune the maf than even a 1 bar, never mind a 2 or 3 bar sd ve table, and I have done many sd tunes.

I totally agree that on a higher boost application, a 2 or 3 bar sd os is required. Also when in sd, there will be a P0102 code if the maf is unplugged, or a P0103 if the maf fail is set to 0 hz. This may be a problem for passing an emission test in some locations.

Russ Kemp

[Bill@HPTuners]

There is a difference between doing it "fine" and doing it right. Thats my only point to this thread...like I said you CAN tune boosted apps using a maf its been done for years, but there are so many disadvantages and very few advantages no matter your boost level and now soooo many options for you to do it the right way that theres almost no reason not to go and do it the right way.

[chrisj6]

Do either one of you have the part # for a 2bar sensor for a v6..the dealership gave me the one for a v8, but its way to big. The 03 v6 sensor is acutally tiny, do they make one for this app? I am tuning a supercharged sonoma with 6 lbs of boost and his ported maf just isnt cuttin it. It will NOT richen up on the top end and is wayyy too rich down low when not in boost, just cant get a good balance so I need to go 2bar.

Chris

[Mr.Big]

Foff,
My biggest hurdle is finding a 2bar map sensor that's plug n play with my LS2... The sensors I've found, look to be, for a totally different set up and nothing like mine... I've got an LS1 style FAST 90mm intake manifold with the map relocated up front, and my fuel rail tabs cut and welded to retrofit correctly. I'm just going by the pictures I've seen in the FAQ section in reference to the 2 bar map sensors... It may just be my eyes, and the fact that I don't see the red grommet on those sensors, but any advice on this would be MUCH appreciated. My search for a dedicated LS2 2bar map sensor has been fruitless thus far...
Thanks for puttin' up with a noob as always...
Jeremy

[HoP]

Mr. Big,

The 2 bar map sensor you need for your LS2 is #12580698. Just ordered on today and works perfect. Plug and Play

[chrisj6]

The logs really dont do any justice. When he is accelerating the error % is lean, then when he hits some of those cells on the way down it richens up and scews those values. I couldnt get consistant data to change anything.

[Russ K]

The logs really dont do any justice. When he is accelerating the error % is lean, then when he hits some of those cells on the way down it richens up and scews those values. I couldnt get consistant data to change anything.

When wot tunung the maf, I don't lift the throttle untill redline.

Russ Kemp

[5_Liter_Eater]

Or use a filter to omit the decel cells so they don't show up in the histograms.

TPS > 90%
EQ Ratio > 1
etc.

Lets not hijack this thread though.

[EC_Tune]

Here is the P/N:
AC Delco Part # 213-1631
GM Part #: 12580698

And the pigtail connector (if necessary):
AC Delco Part # PT1799

[SSUte01]

So what exactly do i enter in to omit the decel values?

I am not sure if you are familiar with how flexible and convenient the plot filtering can be, so forgive me if I am telling you to suck eggs.

If you didn't want any decel data in whatever histogram you are using as stated above probably the easiest way is to filter by TPS%. So in your configure histograms (the cog looking thing that is next to histo no 8) under plot filtering it should default to filter string simply replace with:

[sens.90]>10

That would mean only show data when TPS is greater that 10%. You can do combination filtering eg

[sens.90]>10 & [pid.6010]=1

Which means, this is only for illustrational purposes btw, only show me data when TPS % is greater than 10 and when the EQ Ratio equals 1.

As I said if you are all over it disregard, otherwise hope it of some use to you. FWIW I find it particularly handy to filter IAT when VE tuning as a quick stop like tfc lights etc or park to reflash causes heatsoak which throws your fuelling a little lean causing you to chase your tail with fuel tuning.

Anyways not hijack the thread back to MAFs

[5_Liter_Eater]

Actually to filter out decel the best filter would be manifold pressure. Filter out maifold pressure less than whatever your idle/cruise manifold pressure is.

[SSUte01]

Actually to filter out decel the best filter would be manifold pressure. Filter out maifold pressure less than whatever your idle/cruise manifold pressure is.

Good point I didn't actually think of that. Nice one.

[5_Liter_Eater]

Think I got that one from Marcin.

[shimp]

So using a larger range MAP sensor for tuning FI applications is better than using a bigger MAF like this one: ???

http://www.musclemotors.com/index.as...OD&ProdID=1093

[EC_Tune]

Problem is a hard limit (512 g/sec), and tables that stop at ~12Khz. When you run out of table, you're done.
MAF can run up to it's sonic limit which you can't get to in an NA motor but you can get to it with a LOT of boost.

BTW: A Ford meter outputs 0-5 volts IIRC. Not to friendly with a GM meter that goes from 0-16,000 Hz. (Not 160 Khz -- Typo)

[shimp]

So the problem is in the computer. How does the Ford handle 1000+ hp on a MAF system?

[EC_Tune]

0-5 volt input. Not a frequency input.

[shimp]

So with the GM sensors, the higher the airflow the higher the ouput frequency? So could they make a MAF that ouput higher than 160 kHz?

I am just wondering how so many people get cars running good with Turbos and MAF and get close to and in some cases exceed 1000hp.

[redhardsupra]

the good part about voltage based MAF's that it's easy to multiply/divide voltage. frequency based MAFs are more precise, but the whole idea of multiplying/dividing the range goes out of the window, unless you figure out a circuit that can multiply frequencies.

the reason why some cars deal with a lot of power on MAF is the voltage trick. for example, if your MAF describes 500g/sec at 5volts, and at that moment you'll be doing 20ms pulse width on your Xg/sec flowing injectors, you can cut the MAF voltage in two, while sizing your injectors to flow 2*X.
so at 2.5v computer thinks you're flowing 250g/sec of air, which needs X/2g/sec of fuel. but in reality you are flowing 500g/sec at 2.5v, and your injectors are dumping twice what X/2 would be, which is X. so you're back to the same air/fuel amounts (500g/sec and X fuel, just like in the starting case) but at 2.5 volts, not 5.

this way at 5v computer thinks that it's flowing 500g/sec and needs X fuel. in reality it's flowing 1000g/sec of airflow, and injectors will dump 2*X fuel, keeping AFR the same. so you end up with twice the range on the same voltage range.

this theory goes out the window when things go nonlinear, and since very few things in reality are linear, this method is plagued with assumptions and fudge factors. in the end to have a proper tune you'd have to make up for the imprecision somewhere else, and that's why i'd rather do things right from the getgo--if both methods will ultimately take the same amount of work, but one of them is going to be working off wrong numbers, might as well do it proper.