Magyver

I'd like to know the pros and cons of the MAF vs SD.

horist

SD Pro: Limited sensors, less room for error due to skewed sensor readings
SD Pro: No Restriction, especially if running a larger TB than 78mm
SD Neg: As conditions change , requires some tweaking to stay 100% dead on

MAF Pro: at higher RPMs accurately measures air entering
MAF Pro: No need to adjust once locked in as weather changes
MAF Pro: Lets you runa dry nitrous kit
MAF Neg: Any changes prior to MAF can cause the reported values to be skewed high or low
MAF Neg: Restriction to air from airbox to TB

Another_User

SD, easier to tune for drivability
MAF, harder to tune for drivability

Magyver

Can you give some examples on MAF Neg: Any changes prior to MAF can cause the reported values to be skewed high or low.

slow

iTrader: (7)

MAF

SD

But i do have plans for FI, so that plays a big part.

Ryan

P Mack

iTrader: (6)

MAF con: can't handle reversion at low rpm.
SD pro: histograms make VE table easy to tune, MAF table is harder
SD con: if you have an auto, you need a maf for the transmission to work right
SD con: 1998-2000 run on the secondary VE table

Slow, SD won't keep you from going FI. HP tuners can change your operating system so it can read a 3 bar map.

slow

iTrader: (7)

your right, it won't stop you from going FI and i will probaly try the 2 bar whenever it comes available.

But, tuning by boost can be bad if air density changes.


Ryan.

Magyver

I have a 98 so I am wasting my time using the SD method to tune?

P Mack

iTrader: (6)

You're not wasting your time, you just have less resolution. Unless of course you're only making changes to the primary and not the secondary, then you're wasting your time.

Another_User

Definitely not a waste of time. I have been doing it for a long time.

Bink

MAF, closed loop, increases your resolution.

P Mack

iTrader: (6)

Right, I realize he would see the changes to the primary table when/if he plugs the maf back in. But while tuning in SD you have to make changes to the secondary ve if you want to see results while you're still in SD. I made that mistake once, and was getting pissed off when I was tuning in sd, i would make changes to the primary table, but the fuel trims wouldn't change. If he leaves it in SD like a lot of people do, he'll always be running of the secondary table.

jimmyblue

iTrader: (11)

You will never have a MAF-only tune. The PCM uses
SD for a lot of things. You can get by without the
MAF at the cost of some adaptability. But getting
the SD tune right, or right enough, pays off even
if you keep the MAF, in areas like transient throttle
response and low RPM operation in particular.

SScam68

iTrader: (20)

so, what I would like to know is what gains did you see at the track on back to back passes?

tranny and diff are preventing me from finding out myself

P Mack

iTrader: (6)

Which is why I will never pay for a shop to tune my car. I'm not sure if any shops will take the time to get your ve table right, and I don't blame them cause it's time consuming.

12secSS

iTrader: (30)

That is actually how it should be done to keep the Primary resolution, then just copy the required (every other MAP row) cells over to the secondary. I am using this method and I don't need to guees at the empty Primary cells, because I based my Secondary on it. Plus it is easier to make the copy/paste correction to the Primary.

gojo

iTrader: (12)

Originally Posted by jimmyblue
But getting
the SD tune right, or right enough, pays off even
if you keep the MAF, in areas like transient throttle
response and low RPM operation in particular.

Really good points. Also, you need days with different intake temps to get the IAPark right. I some areas of the country you could wait months for warm weather and in some it never get cold. A tuner would need a lot of time to do it right.

SD Pro- You can get a smoother idle by running it richer.
MAF Pro- Not that much harder to get it running and transitioning well and will hold the tune.

P Mack

iTrader: (6)

Yeah that's actually the method i settled on too. The copy and paste process is easier that way. When I was just starting out I just forgot i had to copy every other row to the secondary.

Another_User

It might be worth tossing that MAF back in after an extreme porting job to match the TB flow. As long as you can scale your MAF table properly.

Magyver

Ok now whats up with this every other row thing? When I start to think I got a hang on this some new info comes up.
Ok today I will be going to the dyno. Yeah I should wait but I want to know what my numbers are before the tune and to see if I am running lean. Sunday I have a nice Autox on a 1.5 mile course and I want to make sure I'm not lean.
Should I go in there and get about 3 runs with the MAF on and 3 with the MAF off? And maybe get 2 runs at WOT as if I was at the track? All this recorded info can help figure out a lot things.
One thing I want to know is the SD or the MAF working the LTFT correctly when I match up against the A/F against the wide band.