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Rob S
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Discussion Starter #1
Hey, would you guys recommend tuning your car in SD mode, or use the MAF sensor? Any other suggestions for a newbie about spark or VE tables? Any help at all would be greatly appreciated. Thanks- Rob (using EFI Live)
 

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If you go speed density, you need to run the appropriate map sensor and os upgrade. That's what I did.
 

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you can use the MAF, but you may run into problems exceeding its max frequency, or run into a problem with Max Delta Airflow. Be sure to to read up on MAF calibrations.
 

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Rob S
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Discussion Starter #5
ok if SD is the way to go, can someone tell me where to get a 2 or 3 bar map senor that works on an LS1?
 

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eBay here. It was an old cobalt 2bar. You just have to take off the two right tabs if you're looking at the label.

I think it was $30 shipped.
 

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redhardsupra said:
SD all the way. we already covered this topic on this board and many other times on other boards. MAF has a limit and it's not descriptive enough to provide a safe tune for anything Forced Induction.
http://tuning.wikispaces.com/tuning+Forced+Induction is the shortest version, i can go much longer on this if you'd like
in that URL it says:
"MAF has a theoretical limit of 512g/sec, but practically i've never seen it go over ~425g/sec"
So if the MAF never reaches its theoretical limit, why so adamant about nixing the MAF? Or are you saying the MAF's dont go over 425g/sec because they are all broken?

I mean sure, if the MAF is being overwhelmed, or youre running a cam with reversion, I can see junking it.
However, if the MAF is not at its limit, why not keep it? Is it not more adaptive to weather and altitude changes?
I can still see logic of a 2bar setup as well, for backup/sanity purposes, but I guess im not getting the main reason for the anti-MAF jihad.

Im not trying to argue im trying to understand the logic behind it.
 

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Let's roll...
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I've been wondering this very same thing. LPE still uses a MAF on their supercharged package and even on some big twin turbo's? I'm not understanding this too well either.
 

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i'm not saying that MAF doesn't work, you can only judge 'goodness' of a part in context of the application. in the context of FI on GM's PCM, MAF's limits are just surpassed so quickly, it makes no sense to use it. for 99% of NA applications, MAF is as good, and in some situations better than SD, simply because you are not dealing with that much airflow. That's the real dividing line between MAF and SD, and not personal preference. I like to tune, and occasionally go road racing, so I chose SD, because I like the throttle response. If I was a bracket racer, I'd probably go OL-MAF so nothing ever changes, and gain consistency this way. That's when I tune people, my first question is 'what's your goal and application?' The key is not to follow a formula here, but know the limits and implications of all different options, and pick the best solution to a given set of problems.

my real jihad is against lying to the computer. traditionally (read: LS1Edit) we here forced to use IFR to tune. Then people started eyeballing MAF to tune, which is much better, but then we figured out SD tuning, which offers the greatest flexibility and least limits, thus I consider it superior to all other techniques available to us.

MAF only tunes don't work for me, because the PCM doesn't work in PURE MAF mode, it's a hybrid between MAF and SD. Thus, if you tune with MAF only, in the < 4000rpm range (where MAF and SD are used both at the same time) values will always change, and you will never quite get it done. So might as well give into the simpler (IMHO) method of just getting your VE done, and then mapping the resulting airflow numbers upon the MAF scale. This way, you can have a 'set and forget' tune, which works in all ranges properly. As a bonus for a job done properly, you also get a fully functional 'backup' so if you MAF fails, you can truck along in SD with no loss in drivability or performance. Isn't that something we'd all want?

The fact that people have sucessful setups built around a MAF, and completely lie on IFR and PE, well, good for them. I'd rather do it proper and without bullshitting--only time will tell who's setup is gonna break sooner.
 

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OK, but you are talking about some rare situations.

I always line up the SD tune via the VE tables before doing the MAF. I never do just the MAF and leave VE alone. Who does that? No one here has suggested doing MAF only...only not to trash the MAF if it will work ok, ON TOP of a well done SD/VE tune. I mean you *have* to have the VE done right in SD mode to calibrate the MAF anyways...right? Whether you use MAF vs airflow or MAF vs LTFT for calibrating it.

My *personal* experience (admitedly limited to about 5 GTO's) is that a properly tuned VE and MAF means a very responsive car under all conditions. For me at least, an SD tune, while running great, doesn't seem to have the throttle response a SD+MAF tune does. Am I wrong here?

One other question you still haven't answered, how much of a difference does an SD tune only make when weather conditions change, and altitude changes? Here in Colorado people regularly go from 3K' to 10K'. A MAF/SD tune will respond to that very well....are you saying an SD-only tune will too?

I live @6k' feet, and my favorite road course track is near 3k'. Id feel much more comfortable knowing my PCM is gonna adapt quickly.

You mention people "lying" with the IFR and PE and no one here is reccomending that...that ive seen.
I strongly beleive a solid SD/VE tune is the basis for the rest of the tuning process, and if the MAF is not overloaded/reversion-ized, I say keep it.

Ill repeat, im not trying to argue with you just because, im just trying to learn and I appreciate the efforts you are making to educate everyone.
 

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What he's trying to say is if you are moving a substantial amount of air (read more than the maf can read) the speed density tune is the only "correct" way to tune a car.

We had this discussion in another thread recently and I said a guy was fine with a MAF until I realized he had his MAF pegged.

Basically, no matter how much air you move past the max of the MAF, your pcm will only be told it's getting the max amount of air the MAF can read. So in order to correct this, you have to command a richer a/f ratio from then on in PE to get more fuel in. As you can see, this is far less accurate than reading the actual amount of kpa in the manifold from a 2bar and adjusting fuel from there and commanding the a/f you want.

And yes, speed density would adjust for elevation since speed density relies on pressure in the manifold whereas a maxxed maf would not.
 

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I get that. Honest. If your MAF is pegged, shitcan it. If you got an uber cam with overlap, shitcan the MAF. Im cool with it.

I just think the MAF is a useful tool otherwise and I see no reason to subscribe to the "MAF is always broken, always use SD" train of thought.

Thanks for answering the altitude thing. I suspected as much, but wasn't sure.
 

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Steel Chicken said:
OK, but you are talking about some rare situations.
this post was about FI on LS2, so i gave my opinion in that context.

Steel Chicken said:
I always line up the SD tune via the VE tables before doing the MAF. I never do just the MAF and leave VE alone. Who does that?
a lot of people, especially 'pros'
Steel Chicken said:
No one here has suggested doing MAF only...only not to trash the MAF if it will work ok, ON TOP of a well done SD/VE tune. I mean you *have* to have the VE done right in SD mode to calibrate the MAF anyways...right? Whether you use MAF vs airflow or MAF vs LTFT for calibrating it.
yes, that's the method i 'invented' almost 2yrs ago, in the days when everyone was tossing their MAFs, i proved that MAFs are to be understood and calibrated, not feared and ignored. they have their place, just not on my car ;)
Steel Chicken said:
My *personal* experience (admitedly limited to about 5 GTO's) is that a properly tuned VE and MAF means a very responsive car under all conditions. For me at least, an SD tune, while running great, doesn't seem to have the throttle response a SD+MAF tune does. Am I wrong here?
and my experience is the opposite. i did 2 track days back to back to get a hype-less experience, one in SD one in MAF/SD and i like the SD better. no scientific methods, but i know that on the track my senses go superman, or i'd end up on the wall, that's why i'm willing to trust myself with that judgement.
Steel Chicken said:
One other question you still haven't answered, how much of a difference does an SD tune only make when weather conditions change, and altitude changes? Here in Colorado people regularly go from 3K' to 10K'. A MAF/SD tune will respond to that very well....are you saying an SD-only tune will too?
read my 'how speed density works' paper, it will explain how SD accounts for everything, in terms of formulas so there's no vague bullshit.
Steel Chicken said:
I live @6k' feet, and my favorite road course track is near 3k'. Id feel much more comfortable knowing my PCM is gonna adapt quickly.
I'd rather have it adapt quickly too, like when you shoot nitrous, i'd like IAT to instantly show me -100C, not slowly dribble down and by the time it's anywhere near real values, the run would be long done with.
Steel Chicken said:
You mention people "lying" with the IFR and PE and no one here is recommending that...that i've seen.
every single 'pro' tune i've seen does it.
Steel Chicken said:
I strongly believe a solid SD/VE tune is the basis for the rest of the tuning process, and if the MAF is not overloaded/reversion-ized, I say keep it.
amen brother! ;)
Steel Chicken said:
I'll repeat, i'm not trying to argue with you just because, i'm just trying to learn and I appreciate the efforts you are making to educate everyone.
good, the harder you argue, the more formulas i'll find to fling back, and that's where the knowledge comes out ;)
 

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thanks for the detailed response. learned alot :)
ive also seen those pro tunes adjust IFR tables and it makes me wanna choke a hoe.
 

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still chuggin on a maf here.they are tuning blown vettes at 750+whp on the stock maf's. if it aint broke, dont fix it.
 
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