FAQ: How to tune the PCM? (Series II SC)

I talked to a guy (Zack Howard) that did custom tunes for people and he said VE tuning is useless because like everyone else is saying, it doesn't do much if everything else is working properly. HOWEVER, I do believe that if you have the time, knowledge, and ability to tune for it why not? It's not hurting anything to dial it in for low throttle use if the MAF fails. You WILL see massive amounts of knock at anything over 50-75% throttle running VE only. Don't believe me? Go out and do some scans with the MAF unplugged. KR kicks in reeaalll fast. My car was hit or miss on idle with the MAF unplugged. Sometimes it would start right up and idle fine, other times it would take 2 tries to start and sound like it had a big lopey cam in it at idle. I never had it stall on me while running with it unplugged.

Stock VE table. Engine surged when idiling and stalled most of the time at stops.


Tuned VE table. Smooth idle. No stalling. Cannot tell the difference from MAF operation


The tuned VE table is the result after two tunes. I feel like I have about two more to go until it's dialed in. Then it's on to MAF and timing!

I have no idea when I will get to GenV and N* so I want to get this tuned up as best as possible in the meantime.

 

And you'll have to do it allll over again.....

Abaddon wrote:

And you'll have to do it allll over again.....

No, not really. I will just need to tweak it from where it's currently at.

Getting from stock to some place stable is where most of the work/fun is.

Here's the effective result of tuning MAFF (blue quilt). All the ripples go away. While it's true that if the MAF sensor fails, the engine will run poorly, as long as the MAF is working, fuel delivery will be smooth and correct at ALL steps:

so you're saying VE has NOTHING to do with operation while MAF is functioning properly?

charlieRobinson wrote:

so you're saying VE has NOTHING to do with operation while MAF is functioning properly?

It's not that it's nothing, but the system is in closed loop. In closed loop it primarily relies on O2 readings, STFT, LTFT and then all the other tables combined for predictive corrections. Nobody can say exactly how much the VE table weighs on the calculations, but with O2, STFT, LTFT and MAF involved things are pretty rock solid. The MAF is a massive stabilizing factor because it tells the engine EXACTLY how much air is coming in. With just TPS and MAP (SD) things are a pretty close estimate. But when it needs to take a guess at what should be coming up, it does reference all those other tables. We just don't know the weight each table is given.

Quote :

so you're saying VE has NOTHING to do with operation while MAF is functioning properly?

I'm saying MAF works like a blanket that builds over VE. If VE isn't perfectly smooth, MAF tuning can be adjusted to compensate. That's why the engine runs crappy if you pull the MAF sensor.

This is my simplified view. As deekster has pointed out, the PCM references VE for a variety of reasons.

If you zeroed out your VE table but kept your MAF activated, do you think your car would run 100%?

Do you think it's possible to disable MAF/unplug it and run your car better than ever before with JUST a VE tune?

charlieRobinson wrote:

If you zeroed out your VE table but kept your MAF activated, do you think your car would run 100%?

Do you think it's possible to disable MAF/unplug it and run your car better than ever before with JUST a VE tune?

Can you run the vehicle off of just the VE table? Yes. Can you get it to run perfect? No. That's what the MAF is for. The VE table is what the Engineers get for a "baseline" on the engine. Pretty much every 3800 has the same VE table (Series specific of course).

Will the car run if you 0 out the VE table? If your MAF is correct, yeah, it probably will. I certainly don't have the stones to be changing that table like that though. Mainly because I am certainly NOT punching all those numbers in one by one

Yo people with HPTuners. How the heck do I scan for injector duty %? I add the PID to the scanner but nothing ever displays. I see all other 3800s scanning this value why can't I? Can someone confirm they have this in HPT scanner working fine?

What am I missing?

Sounds like you aren't adding the right PID?

Does a custom PID need to be made for duty cycle?

Injector Duty Cycle based off the RPM and Injector Pulse Width:

IDC=(RPM*IPW)/1200

Does that look right to you all? I found it on the net but I dont see how that will calculate duty cycle.

Yes, that calculation will give you duty cycle - the /1200 is just all the different time calculations in one place. I usually just watch IPW though. If you do create this, anything over 80% means you are very close to the limits of your injector.

Just watch IPW.

Thanks, Derek.
How do I know by IPW values if I am maxing my injectors?

The formula I made for IDC %:
Engine RPM * Injector PW / 122
[PID.12]*[SENS.112]/122
isn't working but I do see IPW values.

Guys, I stumbled onto this thread while looking for another (specifically looking to see if the fuel pump for the 97 Buick 3800 was the same as the Camaros).  So ... I didn't take the time to read this whole thread.   At the risk of sounding condescending ... there are good sources of information in tuning, and by that I mean there's an OEM calibrator that has written 2 books that you can buy off of amazon for like $20.  He knows what he's doing, obviously since he works for the big 3, and does an excellent job of explaining the control strategy for all OEM computers.  While they may approach engine control in slightly different ways, they all have the same things in common.  His name is Greg Banish, and I wish he had published these way back when i first started tuning... even so these books are so well written that I had several "ahhh-haa!" moments when something he said "filled in the gaps" of things I had seen happen but didn't know why.  

Here's the Link to the two books.

www.amazon.com/Greg-Banish/e/B001JOVJT2   You can also get them electronically through iBooks, GooglePlay Store or Kindle app for either.

The VE table is a look-up table "model" of airflow through the engine at a particular rpm and manifold pressure.  It assumes a steady-state of operation (constant throttle position) for each cell.  The MAF measures (very precisely) the amount of air passing by it and going into the engine.  The VE table and the MAF work together to predict the amount of air going into the engine.  The 02's make adjustments based on "old" information after-the-fact.  The PCM bias's its fuel calculation to the MAF sensor when the throttle position is steady or moving very slowly.  It bias's the fuel calculation toward the VE table during rapid throttle movements.  It does this because during the transition from steady throttle, to a rapid movement of the throttle... the air that rushes past the MAF doesnt all make it directly into the combustion chamber, it's actually filling the vacuum in the manifold.  If it based it strictly off of the MAF during this transition it would OVER fuel, robbing power and wasting fuel.  Can you run MAF only? Sure.  Can you run VE only? Sure.  But why would you?.   Assuming that you've made the corrections to the VE and the MAF correclty, if you have any fueling problems then you need to make an adjustment to a temperature table (usually engine coolant temp) so that the PCM can compensate for temperature fluctuation (that normally plague you with the change in seasons).

Again, I don't intend to sound like a know-it-all because I'm not.  I'm simply trying to point you guys in the right direction.  I cant say enough good things about those 2 books.  Tuning schools and seminars are not practical for everyone due to cost and location.  Those 2 books will get you 90% of the way.  They don't tell you to enter value "x" into table "y".  They explain what's going on and how these things are controlled so you can make the adjustments that the engine needs.

I hope this helps.  Charles

Can you post the link in plain text or whatever? I am buying these books asap. Thank you
There's is so much in tuning that I have mostly speculated on because it's all essentially reverse-engineering on my end. There is no authority for me to just go and ask 'how do these things actually work?'

For what it's worth, Greg posts as eficalibrator on hptuners forum.  When he chimes in everyone listens... Especially the big name tuning shops.  He also teaches live classes, and was (maybe still is I haven't asked lately) working in a video based learning system.  He sells a set of DVD's through summit, but they are expensive compared to the books.  Don't get me wrong,they are worth every penny, but I don't have the coin.  

You can ask questions on hptuners forum, but read those books because no one there is going to tune your car for you... But they will help as long as your are listening and put forth the effort.  The biggest rub for them is someone looking for a handout tune, who won't listen, and won't put for the effort to learning why.  Greg isn't the only person there that knows what they are doing, injector manufacturers chime in as well.  Charles

I have Greg's books and they are good. I'm pretty sure I recommend them early on in this thread.
edit - ah HA, found it. Well, in the middle of this thread. It's pretty long.

deekster_caddy wrote:

Wed Apr 23, 2014 10:19 am
You don't want to necessarily go as high as possible. There are theoretical 'optimal' timing settings based on RPM and cylinder pressure to have the explosion happen at just the right time. That's really where you want it to be.

For emissions reasons GM makes their "acceleration pump" action a bit lean. I can't remember the setting, but it's basically fuel enrichment for throttle movement. When you snap the throttle open a blip of extra fuel is added to counter the rush of air. That is off a bit giving you the KR spike on throttle movement. One thing you can easily change is the rate at which KR ramps down. (again, I forget the name of the setting but it's in various tuning guides).

There's a book by Greg Banish - http://www.amazon.com/Engine-Management-Advanced-Greg-Banish/dp/1932494421 I highly recommend it as he covers all of those factors. He doesn't get specific to any particular tuning software. It's worth the $15.

Enjoy!

Nice! yeah... that's the problem with long threads. I was "passing through" but wanted to share the info. His 2nd book does look at different software, HPtuners, EFILive, BigStuff3 ... not that it matters much if you don't understand the basics but ... yeah.. excellent, excellent books.

good luck guys.

Does anyone have any tricks for smoothing the MAF table? After using AAs spreadsheet and the Table Modifier Thingy I've gotten my fuel trims pretty well dialed in, but the MAF table has some noticeable lumps in it.

DHP doesnt have a smooth function in every table window?
I circled what the smooth functions in HPT looks like.

You just select your cells and use those smooth filters. I cant imagine DHP being any different

Yeah we don't got that. The only feasble option I can think of is if I sent my MAF table to someone with HPT, they imported it, smoothed it, exported it, and sent it back to me.

Aaron and Scott use DHP. They should know how it's done.

First result and first page results are funny. I am curious to know. Good luck

https://www.google.com/webhp?sourceid=chrome-instant&rlz=1C1CHFX_enUS515US515&ion=1&espv=2&ie=UTF-8#q=how%20to%20smooth%20maf%20dhp

I always tune it in sections. Meaning I add a percentage to say, a group of 7-9 cells at the same time. Then add a small, incremental increase in that percentage to the next group. Once you get it close, increase or decrease where needed. When you have finally get it where you want it, just change any little clumps of cells (2-4) that don't "match" the section manually until it "flows" (ha).

I've even gone and rounded every cell to the nearest .01 before...

However, you may find that the "smooth" version doesn't necessarily work out. Tune to what it needs, not how pretty the column looks.