bayer-z28

iTrader: (14)

I've got a street car (Sees occasional track) I'm doing a PP 96mm intake soon and I REALLY don't feel like getting whacked for a new 100mm (or similar) MAF. Wondering what are the pros and cons of having my MAF tuned out. I'll have to leave my stock MAF on for the ride to the tuner and have him dial it out.

How will this effect driveability on the street and track? Based on what I have learned, the MAF is used mostly for WOT. Would this tune be more for a finalized setup? Also, I've heard an SD Tune is a bitch to do.

I tried a search but it didn't turn much up

Texas_WS6

iTrader: (9)

I run SD Only. But with my mods I don't think there is MAF out there that will work, nor will the PCM calculate that kind of air flow, so MAF for me is out of the Question. For you, keeping the MAF is the wise choice. It will still work right with your mods, and will make the every day drive more plesent. SD is not hard to tune, but the MAF will help the PCM handle ambient changes and elevation changes better the SD only can do.

bayer-z28

iTrader: (14)

^ Well, It's a H/C setup that is only going to get more powerful and It's not a DD.. I don't mean to misconstrue that with "Street car." ie: It's not a track trailer queen, it's for dual purpose.. Once i get this thing tuned in the spring, it should be around 440/390RW.

joecar

MAF is used for a little more than just WOT...

unplug your MAF anyway and see how it runs, it may run just fine on the VE table alone (if you had previously gotten the VE tuned for H/C)... do take a look at the long term fuel trims using a scantool, these will show if you need a re-tune.

Texas_WS6

iTrader: (9)

MAF will still be very helpful at that power level. My vote is to keep it until you reach the max the MAF will work at.

bayer-z28

iTrader: (14)

I know it runs like *** with the MAF disconnected.. Everything I have heard on these board in the past 6 or almost seven years is contradictory. People say the MAF isn't used until WOT, but then people say it is.. Based on what I was taught, the MAF senses the volume of air coming into the intake and the MAP is used for the barometric pressures and can tell differences between various throttle positions by the vacuum readings in the intake.

MeentSS02

iTrader: (11)

The MAF is good for steady-ish state conditions - i.e. when the throttle is held at a certain position (like WOT, but part throttle works too), but it falls behind when you do something more drastic like stab the throttle and let off, etc. That's why the PCM uses a hybrid of speed density and MAF - under transient conditions, when airflow is changing a good amount over a short period of time, the computer can just look up what the fueling value should be based on the parameters it sees until the airflow becomes more steady, then it goes right back to the MAF.

At WOT, the computer uses this hybrid scheme until around 4000 RPMs (at least that's the set point I remember), at which point enough air is flowing that the MAF is very accurate (well, at least stock sized MAFs, not sure about the larger ones), so it only pays attention to the MAF from 4000 RPMs on up.

The issue is when you put a larger MAF on a car - for a set amount of air coming in, if you increase the diameter of the MAF, the air will be going slower over the sensor. MAF sensors also don't like turbulent flow of any sort - if air is tumbling past the sensor rather than going across nice and smooth, the readings won't be as accurate. I've illustrated this point to myself by running my car MAF only (with a 100mm Lingenfelter MAF w/ card sensor on a bolt-on only LS1). At part throttle, the AFR was all over the place - it was swinging way lean and way rich while maintaining steady throttle. That was enough to prove to myself why the PCM uses the hybrid approach at low RPM operation, and to some extent that the MAF is probably too big for my application.

For now, I run in speed density, but I do my own tuning, so I can do whatever the hell I want.

joecar

lol, welcome to the internet...

Summarizing from the HPT forum and from what Steve said above:
above 4000 rpm: MAF only.
below 4000 rpm: MAF for steady state throttle, VE for transient throttle.


When you did H/C/I/E (I can't think what S is) did you have the VE table tuned...?

If you did have the VE tuned/corrected, then the engine should run in CLSD (closed loop MAF-less) or even OLSD (open loop MAF-less) fairly well.

Typically the IFR is set for the injectors used, then the VE table is corrected using a wideband, and then the MAF is likewise also corrected.

If you're modding often, then your first mod would/should be tuning software package and wideband... this will allow you to choose to run MAF'd or MAF-less, and other things.

MontecarloDrag

iTrader: (3)

Why do you want to go mafless? Is it because stock MAF will be a restriction?
If your car has a 75mm MAF, you can upgrade to a truck 85mm MAF very cheap and tune it.

MAF tune works better for a mild powered car. You can tune SD very good but still you may have small problems when wheather or altitude changes. No big issues tho.

If the car is not a daily driver, you can go SD no problem, it works good. MAF is still better for your mods, but you shouldn't have problems if tuned correctly.

bayer-z28

iTrader: (14)

^ I forgot I had this thread floating around. I am not sure what was tuned on the car last time. It wasn't driven, just dyno tuned. (Texas Speed) Wasn't quite a fan of what they did, after everything was said and done. It felt nice to have the car tuned, but once I learned more, I was rather disappointed.

Not sure now If I should do a 100mm MAF/Card or an 85mm MAF with the FAST 102. -based on air speed from MeanSS02's post.

bayer-z28

iTrader: (14)

BUMP


I've decided to run an 85mm MAF, 98mm Lid on the 102/102 swap. Again, based on MeentSS02's post above on air speed. Based on that theory, I have also been seeing the 100mm MAF as WAY too big. Even for a h/c LS1 with a 102/102.

Is this accurate?

99mongooSS

iTrader: (4)

velocity is everything on a N/A setup.

ringram

Actually cylinder airmass is everything. A tiny fast port wont necessarily load more mass into the port than a larger slower moving one..

LSxPwrDZ

iTrader: (4)

I wouldn't delete the MAF sensor unless it was maxing the PCM 512g/sec limit. The Frequency limit can be gotten around by using a larger housing for the MAF. The PCM works really well to use all the data it receives to provide consistant fueling. Taking away one of the option's of input in my opinion lower's the ability of the PCM to do it's job.

My current car was run in SD mainly because NA it was pulling in over the 512g/sec limit. Even that limit can be gotten around by scaling the injector's back on a percentage bases but I personally don't like that method even though it has to be done on some newer Gen4 app's.

lemons12

iTrader: (71)

Let's say you get a reputable tuner to do an SD tune. If you have all your own tuning equipment, how difficult is it to tune the car for varying weather and elevation.
I drive my car about one a week.. I'm building a 347/d1 setup and would love to get rid of the maf.

bayer-z28

iTrader: (14)

Are you referring to velocity in the MAF?

This 85mm MAF may or may not be a restriction. I think, in a way, a slight restriction on the intake side would actually help me a little. (Almost like a little "back-pressure" is a good thing.)

Eagle02

iTrader: (20)

For driveability's sake, you want the MAF. The 85mm MAF will flow MORE than enough to get you to the numbers you're looking for and it will allow your tuner to tune your car to behave better than it would on a SD only or MAF only tune. Most any tuner worth their salt can tune to damn near any cam now, and with the numbers you're looking for, your cam doesn't even sound that radical.

What makes you want to take the MAF out?

Eagle02

iTrader: (20)

You're headed in the right direction with this.

bayer-z28

iTrader: (14)

^ Ok.. cool.. This is an older thread. I ditched the SD idea and I was mainly looking for the right sized MAF recommendations. I think I asked on the local boards and the resident tuner told me an 85. I was second guessing the 100mm maf but I saw it to be just WAY too big for that "card" to really pick up on anything. Bigger "pipe" and same volume = slower speeds. I have the 85maf now. Just making double sure.

Thanks tho.. At least I know I'm sniffing down the right trail here.

MeentSS02

iTrader: (11)

How difficult? Not very...just a little time consuming. If I'm really working on the tune, I'll just log data every time I drive - with HPT, their interface works as a standalone data logging tool, so I don't always have to have the laptop in the car.

I've been able to get the SD tune good enough on my car that I can drive it nearly year-round, but it took a lot of work, and it still requires a tweak about twice a year. I've actually not used a MAF since about 2005-ish, and my car was a daily driver until May of 2007. I only drive it about once a week now, and only in good weather, but it'll easily handle temps from near 100 down to the 40s without much variation.