69LT1Bird

iTrader: (1)

Wow, thanks for letting all of us know that the discussion is over. I am not sure what the tuning world would do without your valuable input.

I am sure any of the car companies would be happy to hire you to help cut about $50 in piece price from every car by getting rid of the MAF system.

You could set up a calibration for them that will work for every part of the US, mountains, valleys, hot southern climates all the way up to Alaska, because you obviously know how to make a car run the same no matter where its at or what the climate is like. DD's are different that weekend warrior cars, the general population wants it all.

Thanks for helping.

gametech

iTrader: (1)

Actually, an SD tune CAN be setup to work in any condition. However, the beancounters at Ford decided it wasn't even worth trying. The ones at GM decided to halfway do SD and MAF to meet their goals. The ones at Dodge decided that SD would work without spending the $ on a MAF for every car. Note that NONE of these decisions were based on the best tuning strategy, but rather a combination of cost, engine life, power, and emissions goals. If you toss emissions, most of us have the same (seemingly) conflicting goals to meet.

qqwqeqwrqwqtq

This could be the worst post I've ever read. A properly tuned SD car will certainly compensate for changing conditions. There are hundreds of thousands of stock factory vehicles on the road that run SD and I don't see them driving to the dealer for a re-flash every time the weather changes.

It's not all about money either. See any maf sensors on any newer AMG benz?

I've seen less consistency out of maf cars than SD cars as even a small film of dirt on a maf will greatly effect it's output.

Billiumss

iTrader: (11)

So with a statement like this, I assume you are a high level engineer that works for one of the big 3 in the R&D department for tuning production cars?

If MAFs are so bad, then why do all the major auto manufactures put MAFs on cars/trucks? I'm going to guess because they work. (MAF Only or MAF/VE Blend) MAFs work well for production vehicles and work well for modded vehicles to.

Don't get me wrong, I understand the need for SD tunes and the VE table, makes perfect sense, but for an average car or even an average head/cam car there is no reason to go SD tune only on a MAF based OS. For extreme cases/setups, I can see the benefit of SD tunes when the MAF output signal is way too choppy or you maxed it out under boost.

If MAFs are such a pain and don't work I assume there will be a HUGE recall announced sometime this year on the national news since for the past 25+ years the major auto manufactures got it all wrong when adding a MAF to cars engine control systems.

JonCR96Z

iTrader: (33)

You act like SD is the worse thing that you can do. In a closed loop setup you will NEVER know the difference between MAF and SD, even on a stock car. You can defend MAFs all day long but it's a stupid argument.

Run a MAF if you want, but when it ***** up or becomes a restriction just throw it away. Don't spend money on a bigger MAF that will need to be tuned to worked properly anyway.

qqwqeqwrqwqtq

Don't put words in my mouth. You don't have to be "a high level engineer that works for the big 3 bla bla bla" to know that your post is absolute nonsense.

All the major auto manufacturers do not use maf. Even the manufacturers that currently do still have hundreds of thousands of speed density cars out on the road today. Maybe you did not see my AMG benz example.

I did not say mafs are a pain or they do not work nor did I say they should not be used on the average car. Read my post for clarification if you are confused.

WeathermanShawn

iTrader: (1)

Obviously many people have successfully tuned cars with both methods.

The only problem I have ever had (whether SD or MAF) is trying to DD in open-loop. Each seem to have there peculiarities. With MAF, same frequencies (hz) in different gears can give you differing AFR's. And I have had some drifting with SD depending on ambient temperatures (especially at idle).

INTMD8, what is your view on maintaining closed-loop whether SD or MAF? Seems like if you can get a tune nailed down on a dyno vs street, you will have a lot more success whether you go open-loop or closed.

What do you think?

..WeathermanShawn..

joecar

We can express out personal opinions here...?

The MAF is located a varying distance by cylinder # upstream from each combustion chamber, i.e. measuring future air for the current combustion event and doing it differently for each cylinder... this is supposed to accurately measure the mass of air going in...? By keeping a hot wire "calibrated"...? What if the air is wet/oily/dirty...? Seems like a contraption to me... seems to me to be an obstruction... when it fails it's cheaper to just replace with a pipe and tune for SD...

...and the MAF function is just a table lookup (converts Hz to g/s which is then converted to g using RPM)... just like the VE function (converts kPa and RPM to g*K/kPa which is then converted to g using K and kPa)... they are both calculations based on table lookups... and the MAF can't always compensate for mod parts, e.g. a cam has reversion effects on the MAF when the throttle is significantly open...

The O2 sensors are located some distance downstream, well after combustion has occurred, i.e. measuring past air for the current combustion event... they also protrude into the header pipe, seems to be an obstruction maybe... and they can get fouled... when they fail, it's cheaper to replace with threaded plugs and tune to OL... (altho CL trimming can be nice sometimes)...

it seems to me that the best throttle response is achieved using OLSD (regardless of being stock or modified)...

but I live in flatland so I'm not able to say much about altitude differences, other than if you change altitude during your drive the PCM can only detect the new BARO vaule by detecting a WOT MAP different than the previous BARO value... but the PCM doesn't care about BARO because it uses absolute pressure to calculate airmass from VE.

My $0.02...

JonCR96Z

iTrader: (33)

I don't think any of that is opinion. Looks to be all facts.

I just want to add something about closed loop. It's not always going to do what it's designed to do. As has been said in a modified car it's very unlikely to be 100% accurate (and unmodified for that matter), but it is always going to change fueling. For better or worse. And I would bet that in most every situation where someone "asks" about SD/MAF tuning that they are still going to be using the O2s for feedback.

WeathermanShawn

iTrader: (1)

Thanks Joecar. That really explained it well.

I think most of the problem tuning, whether SD, MAF, or 'combo' is the initial mapping. I can not find a 45 minute log run that does not have some sort of variation in altitude, temperature, etc. So, open-loop tuning ends up with a little more bias perhaps than normal. Identical RPM/MAP's, MAF (hz) can have a fairly big swing in AFR's when you can not keep the variables as constant as you want. (does that make sense?)

You are probably right about the throttle response in OLSD being superior. I agree closed-loop has a lot of unfortunate compromises. Maybe there is some 'user laziness' in that the AFR always appears to always correct itself.

Thanks for the insight.

..WeathermanShawn..

qqwqeqwrqwqtq

I tune many SD cars closed loop with LTFT's disabled, unless it's a car that will be primarily using race fuel, then it is tuned open loop.

My Z06 for example is SD, closed loop, no LTFT's. I've logged the car in 35deg ambient temp to 90deg ambient temp and stft's stay +/- 2% and WOT air/fuel ratio stays within 2 tenths of a point of target 11.8-1.

Is it absolute perfection? No, but either is maf and it's well within the range of acceptability. If perfection was attainable then the factory would have no reason to install o2 sensors.

Billiumss

iTrader: (11)

How are you tuning the Virtual VE table? Are you using HP Tuners with Blue Cat? I know with your application, it must have taken many hours to get the VE table down pretty good with the way the OS is set up. I assume you used a loading dyno?

qqwqeqwrqwqtq

Yeah it was a pain with no RTT with my OS. I have 35+ hours into building the ve table from scratch (which is probably why I've sold 2.5bar base files to many other shops).

No loading dyno but the dynojet has a "dynotrac" feature that will try to hold the brakes at a preset engine rpm or mph. So I would set it for a certain rpm, get data for all those load cells then move up to the next rpm. Would probably be easier with a load dyno to build the ve table but you can get by with using the brakes on a dynojet.