25thhawk

iTrader: (3)

I have a 98 camaro SS with H/C and Fast 90 NW90. Lately I have been getting a p0103 code for the maf. So I am debating switching to a larger maf and lid vs getting the bigger lid and going SD. I need to get a retune any way, so the cost of the tune is not an issue. What are the pro's and con's of the SD tune? I just don't want to have more headaches from going that route. I don't have the ability to tune the car myself, incase that matters.

Thanks

Rhino79

iTrader: (7)

Speed density is a little more weather tempermental. A pro is the simplicity of tuning SD. I generally stay with the maf, with the exception of boost and when the maf may be a restriction on big na setups.

Chevy406

iTrader: (12)

Unless you see your intake manifold pressure (MAP) start to drop at wide open throttle, there isn't any need for a larger MAF at your level. Just replace the bad MAF and look for power increase somewhere else. Is this car a daily driver? If so, leave the MAF in for better efficiency (fuel mileage).

redtan

iTrader: (5)

What makes a great MAF tune that much more efficient in terms of fuel mileage compared to a great SD tune? Key word there being 'great'...obviously a bad tune compared to a great tune there will be differences...

Hemi2Slo

Well a MAF tune will adapt more precisely to changes in atmospheric conditions. A SD tune works off of MAP pressure and IAT, it doesn't actually meter the amount of air coming into the motor. The MAF does meter the air, which makes it able to adjust more to the atmospheric conditions. SD works fine for the most part if done right, but if you don't need SD due to boost or some other reason, the driveability and fuel mileage with a MAF tune will suit your needs better. Just make sure if you want it done right you get a tuner that knows what he's doing and will tune MAF and your VE table.

25thhawk

iTrader: (3)

Car is not a daily driver, but is street driven maybe 3000 or so a year. I think I will just look into getting a new maf and go that route. Thanks

25thhawk

iTrader: (3)

Do you think it is worth it to pick up a 85mm truck maf and FTP 98mm lid? What do you think the gain would be? Thanks

redtan

iTrader: (5)

I guess that's true if you drive between the coast and top of mount washington every day, but on a daily basis driving around town a speed density tune is not going to be that much different. I've gone thru 90* summers and 10* winters and fueling is right on par the whole time.

But that's what o2 sensors are there for...to get you as close as possible to stoich. So no matter what tune you have, the o2 sensors command the fuel at part throttle. If anything, a speed density tune that can't 'adapt' to changing weather conditions will be more fuel efficient. On a cold winter day, a MAF tune will see more air and throw more fuel at the car. The same SD tune will not, thus lean the car out slightly due to more air but not more fuel.

I and many will argue that a properly done SD tune has much crisper throttle feel and a much smoother transition between cells. Never heard of a MAF tune being superior at driveability...but that's subjective.

Hemi2Slo

Well this arguement is made all the time, and everyone has an opinion. I'm not advocating a purely MAF tune, but from my experiences here in the south with the humidity and temp changes, I have yet to see even a well done SD tune that has the driveability, fuel mileage, and throttle crispness that a MAF+VE tune has.

My friend has a 2 bar SD tune on his blown car. Excellent tune, done by an excellent tuner, but it still feels flat when the temps and humidity rise, even more so than when it had the MAF. My car had an SD tune on it as well, tune was dialed in perfect, but it felt flat with fluctuations in conditions. Put the MAF back on and retuned MAF+VE and the flatness went away.

redtan

iTrader: (5)

I would think the south would be more forgiving in terms of temps at least, it's always hot or warm there. I doubt you see as much as 90-100* swings in temperature there. You're in the 80s-90s in the summer and 60s-70s in the winter. Not much change.

Summer here is 90s and winter is single digits. Talk about a temp change...

I guess do what's easier for you OP, but ever since ditching my MAF (maybe it was malfunctioning and that's why my car drove like crap) I've never felt the car more responsive.

minytrker

iTrader: (13)

If both tunes are done right you can not tell by driving or economy if a tune is a SD tune or not.

edcmat-l1

iTrader: (10)

This is the right answer.......

brianfromhawaii

iTrader: (3)

people that say SD tuning isnt as good as a maf, and that it cant adapt to weather changes and such, dont make sense to me... do you have any ******* clue how many cars DO NOT use a maf and rely on map?

if you tune the car correctly, you wont be able to tell any difference between the two..... however the maf sucks for boost, and for biggg NA cars as it is very limited...

Sid447

+1

Chrysler are still running factory SD on all their hemi V8's.

joecar

+1 on all the above.

And all those HSV cars running around with factory SD.


I think people get into problems because of these things:
- non-steady-state (and otherwise poor) data is allowed into the tuning corrections;
- injector charactistics tables are incorrect;
- dynamic wall wetting tables are incorrect;

(the last two are hard[er] to obtain)

25thhawk

iTrader: (3)

I am not for or against either one. My problem is that I am setting a p0103 code everytime I spin the motor over 6400. The flow rate is at 58.1 when it sets the code. So either something is up with my maf, or I need to have a bigger maf or change the tuning so the maf will handle the airflow or run SD. Either way I am planning on a retune from Jeremy F, so I feel confident he will get it right. I'm just looking for my best route before I put money into parts.

The car is a stock cube HCI making 430 rwhp. I didn't expect to have problems with the maf at that power level. It has been running on this tune at that power level for 2 years and I never had a problem, so not really sure why it is setting the code now.

Hemi2Slo

Explain to me how something that is not metering the amount of incoming air charge is as accurate/more accurate than something that meters the incoming air charge. If you are not metering the incoming air charge then you, or the computer is making an educated guess. MAP and IAT do not tell you that, and that is all you have without MAF. Sure, you can get it close, but its still a guess. Sure many vehicles run SD, it can be done and you can get it close. But you will never convince me that a tune that is not metering the air is as good as a tune that is metering the air.

I may not be an expert tuner, but I do know how systems work. Our engines are systems, doesn't matter which way you slice it. All systems can be broken down to simple terms as having a measured variable, a controlled variable, and an output variable. The measured variable is air charge, the controlled variable is fuel, and the output variable is AFR. The preciseness of the system's ability to adjust and adapt the controlled variable is limited to two things: the ability of the tuner, and the preciseness of the metering of the measured variable. Note the AND between the two limiting factors. Both come into play here, not one or the other. If the system cannot properly meter the measured variable, then the output variable will only be so precise regardless of how good the tune is. So without all the sensors of the system working in conjunction with each other, the output will only be so close. If you have no MAF, then you aren't metering the controlled variable, you are only guessing as to its value.

MeentSS02

iTrader: (11)

There are things like reversion and turbulence that can cause problems with MAF readings - not as much of an issue if the car is stock, but if you have a snotty cam and/or a modified intake tract, it can be an issue. F-bodies have a very short shot from the air filter to the throttle body, and the MAF has to be stuffed in that small area. The air has to take a very sharp turn just prior to that, and that is a recipe for disaster when you are hoping for a steady flow of air over the heated wires. That's why you see the screen in front - it is a very necessary air flow straightener. The 85mm MAF sensor on a C5 ZO6 doesn't have a screen, but the intake tract has a longer, straighter shot from beginning to end. Try that with an f-body, and your results may not be that great.

In the end, the MAF is only as good as its calibration, and that calibration assumes that the air only flows one direction and in a relatively smooth manner with the types of MAF sensors found in these cars. Even the guys responsible for the original PCM programming knew this would be an issue, hence the hybrid SD/MAF that is used under 4000 RPMs to deal with throttle transients.

SD was only meant as a backup, but it is fairly robust, and with enough tinkering, is actually pretty stable. I know this because I daily drove my car in SD for the better part of 3 years, including one year where temps ranged from the 90s down to the teens here in Ohio. Did the tune have to be touched up in the winter? You bet it did, but it just became part of my routine maintenance. Probably not great for a guy that doesn't like to tinker with a car much, but I was okay with it.

joecar

The MAF is actually measuring the current required to keep a resistive wire hot, and converts this current to frequency... the PCM reads this frequency and looks up a table to convert it to airflow, and then it combines this with RPM to calculate cylinder airmass;

i.e. there is no direct measurement of airflow or airmass...

how is this any different than the PCM reading MAP, IAT, RPM, looking up the VE table and computing cylinder airmass...?

[ i.e. sensors read, tables looked up, calulations performed ]

How can one method be said to be more accurate than the other method (they both involve many steps)...?

When engine is modded, both VE and MAF require to be corrected (using a wideband)

[ i.e. the MAF is not absolutely correct... if anything is changed upstream and/or downstream of it, it must be corrected, see what Steve said ]

joecar

The system's ability to adapt depends solely on closed loop oxygen sensor fuel trimming...

this trims the commanded fuel to stoichiometric regardless of the correctness of MAF or VE...

[ but you can't safely make the engine pull any significant load with commanded fuel at stroichiometric ]

when commanded fueling has to change, then closed loop trimming fails (due to the narrowband method of trimming) and the MAF and VE are now required to be correct if the engine is to pull any significant load safely/properly.