Ed Wright

iTrader: (1)

Normally aspirated? That certainly has not been my experience. My 383" made over 500 rwhp, through an non-lockup 4400 converter, without maxxing a stock 85mm 6.0L truck MAF. So have some customers. I only gained 6 rwhp gained going speed density. A lot of re-tuning for 6 rwhp.

Properly tuned MAF cars also don't require re-tuning as often when changes are made to the car, just like the MAF equipped Fords.

Guess the GM engineers don't know what they are doing, building a race car with a MAF. They would probably be even faster in speed density mode, right? I'm sure they never thought to try that. Probably too inexperienced to tune it anyway.

foff667

iTrader: (2)

I think you'll like the route they went with the 08' LS3 code...no more maf limits to an extent and with hptuners the spark g/cyl & rpm table axis can be manipulated to any extent meaning you'll almost have custom operating system capabilities with the stock operating system. The only thing that sux about the 08's is they still cap the IFR table to 63.5lb/hr.

PowerShift408

iTrader: (44)

So the C5R was limited by the MAF after 500 rwhp...

RedHardSupra

iTrader: (1)

1. ever seen pics of the real C5R? how many separate air ducts are there? two.
2. do you really think someone would run a C5R car on a daily driver computer? c'mon, look at the dash, what does that look like? MoTeC. they dont have silly daily driver friendly/warranty lengthening/lawsuit limiting limits

cmon guys, MAF vs SD is one of the oldest arguments on this board, these exchanges should be getting smarter not dumber with time, and this is just getting plain silly...

2002_Z28_Six_Speed

iTrader: (19)

From what it seems to me, GM always puts MAFs are cars that tend to be modified. Cars that don't get modified never seem to have them. Like Cavalier.

I have always heard that the MAF was to help pass emissions and to help keep the car safer if it was modified. MAF can determine grams/sec regardless of if it is in OPEN LOOP or not on the stock vehicle [unmodified]. The MAF can help the car pass emissions before the O2s are warm. In SD you have to take a guess from a table, apply a modifier, and wait for the O2s. Repeat.

To me, it is just extra weight on the front end. If you have to tune the car anyways. Why put it back on?

ringram

Its ok if you guys dont want to think about things properly, others will help.
Its not the MAF per se, thats the problem, its the fact that the stock ECM WILL NOT TELL YOU WHEN ITS OVER 512g/sec its simply impossible. In addition the stock MAF is designed to read 12KHz MAX! Look at an 00 tune the max g/sec is actually under 440g/sec.

Hell C5R wont be running a stock ECM will it! Also Im sure its not a stock MAF otherwise they will be having problems.

Once the MAF runs out of resolution you are into using the PE table to fuel, doesn't mean the MAF still has control, its maxed out, its passed control to MR PE table, which is about as rudimentary as you can get. All the MAF is doing to say the same thing "I can only see 512g/sec" or if stock like the 00 Camaro mentioned above "439g/sec"

Af Foff says, a newer OS is a different story, in fact the 08 in SD mode is also cool, same thing, no limits to airflow measurements. You just need a MAF that reads higher or an OS that allows it to be told about more air. Yes you can now get MAF's that read to 15KHz, but does your OS allow this!?

RedHardSupra is right, its been covered before by people with larger brains.

Frost

iTrader: (45)

Nice sarcasm, you get a silver star.... I didn't realize that a C5R factory racer had a stock GenIII f-body/Vette PCM and MAF..

As far as your N/A argument, I just looked back through a setup I tuned very recently with a set of MTI stg2R heads and g5X3 and the frequency is reaching 10.8Khz by the shift point, that's only a few cells from the end of the scale(12Khz). Again, this is with an OEM PCM and MAF.

Ed Wright

iTrader: (1)

With a stock 85mm meter that is like 130 gm/sec from the limit. A larger MAF like Lingenfelter's would extend that range greatly. They put the tables for it on their website. You may think Graham and the guys up there don't know anything either.

I give up.

Frost

iTrader: (45)

Enough condescention already, especially since all you have done here is build a straw man. The OP doesn't have a Ling MAF, 85mm MAF, an intermedite MAF handler, or anything other than a stock PCM. I'm not talking about race cars, aftermarket MAFss or EMS's. It's true that the stock PCM can read up to 512g/s but the stock MAFs curve ends before that, and so does it's accuracy at the upper threshold. That's why the table plateaus. Can we at least talk about the same things here?

gametech

iTrader: (1)

Frost, let it go. You are arguing with someone who locks their tunes so noone really knows if they are any good or not. Try not to let too much snake oil splash on you.

My90Iroc

iTrader: (26)

Here's the difference.

SD is a tune done on a given day in given weather conditions. If you tune your car on a 60 degree dry day to perfect a/f's then go drive on an 85 degree humid day you'll be rich. SD uses the VE table and tps but depending what the conditions were when that table was tuned it may not be accurate. There are iat and ect adders but they're not enough to make an accurate tune, plus the location and accuracy of the iat have been questioned many times. Aside from this there are no adders for humidity, barometric pressure, or elevation.

MAF measures the actual air mass (that's where the name comes from) moving into the motor. As the surrounding elements change the computer can compensate. So now as it gets humid or you change elevation or whatever, the computer has and idea of what's going on.

When you put these two systems together you get a very adaptive, reliable setup. SD is the base of the system and will be referenced for throttle transitions, especially tip in. MAF typically doesn't react quick enough for some of these transistion points. The maf is referenced when throttle position is steady and can then accurately account for changing conditions.

MAF being a restriction is silly for most cars. If it was truly a restriction you'd see vacuum when you log wot runs. If you're really scared of it being a restriction have the maf ported and a tuner recalibrate the table. 5 metal wires will not create a restriction or at least no more than your throttle blade and shaft.

Also beware of tuning trying to convince you a getting an SD tune when it's not necessary. Proper SD tuning takes a long time and carries a much higher bill.

To the original poster: What is your engine setup?

SSpdDmon

iTrader: (10)

My90Iroc

iTrader: (26)

I see the point you're making but I don't totally buy it being that simple. I should've been more careful with my wording as well, barometric pressure is usually corrected so baro is the same for long island as denver. We all know DA on long island would be much different than denver.

Without getting off topic into a weather class I still stand behind the maf's ability to adapt to changing conditions over SD, especially with the humidity we experience on long island. Besides the original question was if SD would be appropriate because the maf would create a restriction. Without knowing the setup or power output it's hard to say.

RedHardSupra

iTrader: (1)

if SD cannot make up for different conditions, then why does it use MAP and temp sensors? what you're describing here sounds more like a very barebone alpha-n model.

you gotta remember that any model is only as good as the sensor data you feed it. then there usually are some sort of constants describing certain relationships. the fact WE dont know how the full model works, or how to calibrate certain tables, doesn't mean the model is junk.

Temps are a very good example, i'm glad you brought it up. Since it'd be difficult to cram a temp probe in a cylinder, we can only estimate the aircharge temp, from two other temps. The final aircharge temp is a result of a relationship between IAT, ECT, and airflow, bound together through the temp blend bias table. this means we will not have the right number for the final temperature if IAT, ECT, airflow, or the calibration dont have the exact representation of reality.

as for adjustments for humidty, the difference between 0 and 100% humidity will cause 0.9% change in air density, so while it is a factor, it's a small one.

the altitude barometric pressure will show up in MAP readings so that's taken care of too.

I found some SAE paper that discusses the reaction speeds of MAF's hot element and it's VERY fast, so it should not be a factor. having said that, I personally like SD better because it does give me an increased throttle response.
which restriction are you talking about? the physical one (as in wires sticking out into the airpath) or the computer one (only that many bits assigned to the MAF tables enforcing the precision and the range of the expressed airflow values) ?
MAF can be a physical restriction, I've seen a 6kPa drop before and after a MAF element past 4000rpm in an old turbo audi. our MAF's however dont seem to have that problem, at least on the more common (<500hp) setups. It is however impossible for MAF to be better than a straight pipe replacement, as in the end, you do have some physical pieces sticking out, obstructing the airflow.

the only way to figure out if it's a problem or not, you'd need to get a differential pressure meter, and stick its probes right before and right after the MAF and see the pressure drop at different RPMs.

I dont see how you would NOT need a VE adjustement, even if you're planning to run with an active MAF. Due to the hybrid nature of the GM airflow model, all transitions are still calculated using the SD calculations. so if your MAF is dialed in perfectly, but VE is stock, you might end up with a car driving smooth in steady condition, but being absolutely rubbish under any transitions.

you are right though, PROPER SD tune takes a lot longer, mostly because only now we're finally to arrive just how complicated it is, and how our current methods are crude and fall short of both what is required and what is available when using the SD model properly and to full extent.

My90Iroc

iTrader: (26)

Good info on the weather and sensors

That's good to hear. I still wish we knew how much the computer looked at SD and at the MAF during throttle transitions. Looking at the rules for steady state throttle response should be based on SD calculations. With so many people claiming better throttle response in SD I'd really like to know what the computer is doing, unless of course the maf creates some sort of physical restriction.

I was referring to a physical restriction. I assume that's everyones big concern.

I agree and I wouldn't tune without VE adjustment. I just know I've spoken to a couple people who've been sold SD tunes for n/a cars. Both were under 500rwhp but told SD was better for one reason or another. Both had hefty bills and truth be told I don't think they would've lost any driveability or power running a maf system.

FWIW I believe the gm hybrid system is a great way (except high boost FI cars)to tune. It covers all bases one way or another. I think we all agree there's no one best way to tune but I personally feel with the hybrid system it's more "set and forget" once the initial tune is done. Drive anywhere in any weather and maintain all around performance. I like SD but I need to see more evidence of it's adaptability (at least on GM's platform) before I totally buy into it.

joecar

That's a case of being taken advantage of, sad to say, it happens a lot.

Omega Doom

iTrader: (2)

my combo is basic and simple? stock 02' LS1 from a WS6 with FLP stepped headers to 3" true duals, with a Yank 4200 stall and free mods and thats it! the Tuner who is well known isn't going to charge me anymore and even has said we will do both tunes MAF and SD go with whichever works best!

My90Iroc

iTrader: (26)

Can't beat that then. Let us know how it works out.

Omega Doom

iTrader: (2)

oh I will for sure my Tuner is a well known LS1 tuner so I trust him to do his magic! he is Cmarshz on here!

RedHardSupra

iTrader: (1)

yes, popularity is by far the best metric of assessing quality, just look at top40 charts, or the presidential elections :/