Full-Force

iTrader: (11)

I just tried tuning my car for the 1st time today. I logged about 30 minutes and then went to change my VE table. My LTFT's were mostly in the -15 range. The car idled at -11. All of this was done with the car fully warmed up. I dropped all of the corresponding cells of the ve table by the value in my ltft cells and then wrote it to the vcm.

When I drove the car again it seems that I was still seeing -15's all over thye place. How do I get my ltft's closer to 0?

SSpdDmon

iTrader: (10)

Were you in SD? It sounds like it's still using the MAF for fuel calcuations. If you want to tune it with the MAF still working on the car, you change the MAF table. But, I wouldn't do that unless the car is fairly stock (i.e. no internals, heads, cam, etc.). People tuning the "right" way say to do the VE table and I agree. But, then again, why do they sell MAF Translators? To adjust AFR. So, on a nearly stock car, why couldn't you just adjust the MAF table and avoid messing with the VE table? Something to think about...

TAQuickness

iTrader: (28)

I agree with SSpdDmon - sounds like you weren't in SD mode.


Just adding to the discusion...

If the MAF is 100% bone stock original equipment, there should be no need to recalibrate the MAF.

However, if the MAF has been descreened, ported, or otherwise "upgraded" the stock airflow table is no longer valid for that MAF. The point of tuning the VE table first is to have a known good air flow table. Once the VE table is dialed in, you can then recalibrate the MAF to have a good air flow table.

All that said, If your VE table is correct, there is little need for the MAF unless you plan on running a dry shot.

Bad30th

iTrader: (13)

What year is your car ?

98 and 99 fbodies use the secondary VE table when in SD mode. Did you maybe make the changes to the primary table so that's why they're not being seen ?

Cheers,
Rob (Bad30th)

Bad30th

iTrader: (13)

Negative ghost rider.

I was laboring under this misapprehension myself, until it was pointed out to me that the stock MAF curve isn't calibrated to the MAF itself, but rather to the airflow characteristics of that stock MAF on a stock car.

Once you modify anything regarding airflow (cam, heads, even a freer flowing air filter) the MAF table is no longer accurate :

http://www.allmod.net/hpt/

"The Problem:
To create an easy way of recalibrating MAF, to reflect changes in pre-MAF airflow as a result in modifying the MAF itself, lid, air filter, porting, polishing, hacking anything."


Correctly calibrated MAF tables for stock LS1 MAFs will look very different on a stock car vs. a heads/cam car vs. an FI car. Obviously porting/polishing the MAF would also require an adjustment to the table.

Otherwise, people would just do VE tuning and then turn the MAF back on and it would magically be calibrated for every car.

Cheers,
Rob (Bad30th)

02sierraz71_5.3

iTrader: (2)

I have had good luck with my method for tuning the maf but the ve table needs to be almost perfect because at throttle transitions and low/high rpms the two play off each other. This is why you tune the ve first in sd, then go on. Any mistakes in the ve are played out when you try and adjust the maf you will see them. Its time consuming and a pain in the *** but it makes for a very well running happy engine when both are dialed in.

TAQuickness

iTrader: (28)

Learn something new everyday.

I've talked to some of the remaining guys as Shell's test engine facility, and for test engines, they would calibrate MAF tables to actual air flow. I assumed GM would have done the same thing... But we all know what asuming will get you.

I don't doubt what you are telling me, but if at a given MAF output frequency you have x g/s air flow, how would installing a cam or head that allow better flow change that? I would imagine the MAF output Hz would increase showing a greater flow. Paper vs real life I guess...

Now I wish I hadn't tossed my MAF so I could try this out.

Bad30th

iTrader: (13)

I'm with ya, it seems like there are two possibilities.

One is that the MAF consistently reads x amount of air at y frequency. (But what about air density, and intake restriction or lack thereof ?) While I realize that x amount of air should = y frequency, and that the IAT determines the air density, that doesn't seem to hold up to real-world testing.

The other option would be that that the amount of air at x frequency changes based on intake tract and engine airflow characteristics.

The real-world scenario has to be the second option, or else everyone would be using the unaltered stock MAF table.

I'd really like to hear from someone to can give a definitive answer - all this guessing at tuning is giving me a headache.

I also have the real-world experience of my car currently running like crap with the switch from milled 5.3L heads to 71cc 5.7L heads. Nothing else changed and my P0101 code and drivability issues are terrible right now - looking for answers. I am going to try to redo my tuning from scratch (redo VE, then recal MAF) to see if I can improve it...

Edit : After thinking this over, I'm pondering whether my VE table is now way off after the head swap and not the MAF table, even though it's a MAF code that's being thrown - probably because the VE table is so far off now... VE would have changed substantially with the much larger combustion chamber.

Rob (Bad30th)

TAQuickness

iTrader: (28)

One thing the MAF does do is compensate for temperature.

For paper's sake, assume airflow is a constant of 50 g/s

at 86* F the MAF outputs a frequency of 1,000 Hz

at 60* F the MAF outputs a frequency of 1,100 Hz

I believe the main of the purposes of the IAT (along with the barometric pressure and MAP samples) is to calculate density for the VE table values.

At any rate... tossing the MAF really makes tuning easier IMO

PS the numbers I used above are just random numbers.

Full-Force

iTrader: (11)

To my knowledge I was not in SD.

I used one of teh stickies to get started. Here is what I did.

Copied hi octane table to low octane table. Sticky says this assures optimal timing? I set MAF fail frequency to 0 and then made sure it threw the P0103 code.

Then I logged about 30 minutes and my LTFT's were mostly in the -15 range so I leaned it out to what should have put it close to sero but they are still about the same. Was I supposed to do something to get into SD mode before I started changing the VE table? I just went by the sticky, it said nothing ofthe sort.

Im still new to this and I appreciate the help. Another member on here, Lady REDHawk has been a great help too. She is known around these parts to be one of the best tuners.

Is there a writeup on tuning the maf table? That would be like what the maft does right?

Full-Force

iTrader: (11)

For the record I did in fact make chabges to the primary table. Thats what the sticky said do.

The sticky I keep reffering to is the tuning 101 under the READ ME FIRST sticky.

TAQuickness

iTrader: (28)

That's the problem. The tuning doc in the stickes should be updated for that nugget about the 98-00 PCM's.

As you make the changes to the back up VE table, you will also want to make the changes to the primary. This way, when you go back to closed loop with the MAF, your primary ve table will be corect.

RedHardSupra

iTrader: (1)

you know, figuring out what MAF really does and how do we make it useful again after extensive mods was done back in like february between me and TXhorns281, it's in the stickies by now. the whole 'maf sucks' philosophy stemmed from lack of understanding and ability to adjust the maf for your particular setup. by now my maf and SD modes are so calibrated that i will bet you 100bux you won't be able to tell by driving it, or even putting it on the dyno. learn and adjust, not bash and oversimplify.

Viper

iTrader: (6)

I agree, and have been reading extensively.

However, the tuning docs do need updated, otherwise we end up like this. I did the same thing, downloaded it, read it, did it and failed. Spent 2 weeks on here and ls1tuning.com and hptuners.com finding the 'nuggets' that are not in the original docs but make life easier.

Now, I do appreciate we have 'a' document compared to before where it was search, search and search again. But it does need updated.

TAQuickness

iTrader: (28)

Red - point well taken. However, I for one like to understand why I'm adjusting (before or after the adjustment).

RedHardSupra

iTrader: (1)

of course you like to understand, that's why it took me 2 months to figure out how to get one table right
the whole conversation is in the stickies though, how TXhorns and i took two different approaches to the problem, but then we figured out what works practically, and then i made a spreadsheet out of it. it's all there.
short version: pe depends on MAF and VE. MAF depends on VE. thus must have VE perfect first, then do MAF and you're completely in agreement on how much air you're getting when. also it's a really good method for spotting intake bottlenecks

if you wanna read about my take on it: www.allmod.net/hpt

Full-Force

iTrader: (11)

So am I going about it wrong? Where do you turn off the MAF?

It has to be turned off to tune the VE table?

For the record I have not modified the MAF sensor in any way.

TAQuickness

iTrader: (28)

The easiest way is to unplug it. Or you can set the fail high frequency to 0 and the fail limit to 1

This is a document I put together for open loop SD tuning. It requires a WB for this procedure, but It does have some answers you are looking for.

It's also geared for EFILive, but, the tables should be similar or the same in HPT.

TAQuickness

iTrader: (28)

Red - I think I'll start a new thread on actual MAF operations rather than continue to hijack Full's thread.

Full-Force

iTrader: (11)

Hey TA man, JACK AWAY. Dont sweat it.

I forgot, I did in fact set the fail frequency to 0. Does that disable it altogether? Also, do you leave it at 0 forever?