KurtRardin

iTrader: (11)

I purchased HPT Pro some time back and used it first thing to do stuff like adjust for gears, etc, but felt a little intimidated by tuning my 98 right away. Well, as you can see in my sig I've got a cam only car, and the tune is for the most part stock. The way the car has been "hunting for an idle/bucking/running like crap" has more than motivated me to learn how to tune this thing. I've been cruising all over both forums (here and HPT), reading stickies, searching old posts, reading Cpig and gary, etc. I just got done reading Greg Bannish's book on tuning (good book btw). So far all of this has made me feel a little "in over my head." I feel like I am learning several things by using the compare feature and looking at other peoples tunes who have similar mods, but I am still a little scared to just throw one of those in. Gregs book may have done more harm to me than good beause now I feel a little gun shy... so many tables and so many chances to destroy my DD. I don't plan on doing any WOT tuning, or track runs any time soon, as I do not have a wideband yet.

What I HAVE been doing, however, has been the SD tuning (maf failure) and adjusting VE tables according to the scanner. Does it seem normal to have negative LTFT values in the low RPM range after a cam change?

After I started logging and trying to get the VE tables correct, I noticed that the majority of tuners shoot for the idle tune before they do anything. Should I focus on that first?... since that is one of my major PITA's. Or will that eventually get ironed out by smoothing out the LTFT/VE table process?
Have many of yall have gotten your car to run really good with tuning just on the street? Gregs book just made it seem like getting a factory like tune is next to impossible without having a PHD in rocket tuning.

Just needed to do a little venting

slowec

iTrader: (9)

You really should not be tuning ve without a wideband. Logging the wb o2 is a must. All else is quessing. I am a newbie tuner too , but this much I am sure.

Radcannon

iTrader: (3)

You NEED widebands. The reason the factory put in narrow is because they have the tune dialed in and the use the narrowband to verify it is working correctly.

I have no idea what you were talking about LTFT and PITA's unless you are referring to Long Term Fueling Tables??? I do calibration at GM so I guess you could say tuning.

Really all you need to know is afr, spark, and some other basic things to get it running right. You will never get a factory tune because you will never have the instrumentation like the factory has. I don't understand why you would ever touch the MAF the mass air flow is calibrated sensor that shouldn't need to be messed with it knows the flow of air through it and if you start changing it you will throw your long term fueling off to try and compensate to keep the engine at stoich.

turbolx

It's not as bad as you may think. Granted, not everyone is cut out for EFI calibration work, but you should be OK if you're not afraid of a little math.

Start in the middle at part throttle first when working on the airflow models. There's too many things that can screw up idle. You should be able to get some clean readings at part load and begin seeing some trends that will give you a better idea of what kind of changes will be necessary both at idle or up at WOT before you get there.

Concentrate on getting the airflow models (VE table and MAF curve) right before doing idle running airflow trims since these are all based on measured airflow for corrections anyway. Just take it one step at a time and you'll be fine.

jimmyblue

iTrader: (11)

Idle tuning is a lot of cut-and-try, and getting it
happy depends on getting the tune right for some
areas of operation that you don't expect to see,
or spend much time in.

Particularly, the airflow accuracy at RPM below
your idle setpoint matters a lot to surging, but
you collect almost zero data in street logging.

The best approach I have found, is to use the
real time tuning OS and real time controls in the
scanner (whichever you have at your disposal).
You can lock IAC position to dial down the RPM,
and mess with the commanded AFR to see how
MAP responds (lower MAP means happier motor).
Similarly for idle timing.

Cammed cars in open loop will idle at MAP levels
that push additional enrichment, in a lot of cases.
Plus more MAP over-enriches further, degrading
efficiency / elevating MAP some more, and so on.
This positive feedback can aggravate surging,
beyond just the simple slowness-to-respond of
an overfueled, undersparked enging (lag which
destabilizes the idle RPM loop).

You can work with the narowbands to get idle
to roughly-stoich, by looking to hit a region of
active switching. However idle exhaust content
on a cammed car will be jacked by overlap air
shoot-through and an indicated-stoich out the
back, probably means somewhat rich at the
intake port. This may mean you have to tweak
O2 sensor switchpoints if you want a happier
idle in closed loop. Not also that the common
widebands are as subject to exhaust-air
spoofing as the narrowbands, being a similar
chemistry and only more elaborate signal
conditioning / heater control.

If you can dial down the airflow and get it to
run clean at 400RPM, you can bet you won't
have the surging problems. It's when you dip
into uncalibrated-RPM territory, and get stuck
in the tar pit, that surge can refuse to let go.

KurtRardin

iTrader: (11)

Thanks, I just learned how to read last week. Thats a skill that would have made getting my degree easier.

PITA's was an acronym for pain in the ***'s... which actually should have been pains in the ***. I realize that the MAF table was calibrated at GM, every howto that i have ever read on tuning has mentioned dialing in the MAF. Gregs book also refered to looking at the maf graphs to sooth out spikes. If that is referring to something different, then i apologize, I am not about to start touching tables that I have no clue about.

Jimmy, thanks for the information. I will definitely try to learn more about that area, and that will make driving much easier. Tar pit is a great way to describe the idle thing. My car will just quit at idle sometimes. And about the 02 signal timing... where can i go to learn more about that, and how would I gauge the effectiveness of a moddification to that area? I need to get a control over my exhaust leaks before I get a wideband. They're all down stream, and I kinda doubt that a leak could travel upstream to the factory 02 sensor...but i've been wrong on other things - luckily people around here let you know when you're wrong about something. Jimmy, where did you learn so much about tuning?

Soundengineer wrote an awesome schematic for hooking up a wideband in the narrowband bung. Is there any tuning that needs to take place in order for the ECU to process the information... and is the collector a decent place for a wideband?

Thanks for all the help everyone. I am not defeted by the complexities of calculations and learning deep topics, but this one is a little different in that there isnt really a manual to refer to.
In the Marine Corps, I mainly dealt with explosives, and used them in both urban heavy combat environments where time-on-target was the biggest priority, and then special case scenarios where complex calculations were needed to determine precisely how much demo was needed and what stand-off was necessary... I must say that being shot at and shooting back while smacking C4 on someones door... or crunching numbers for reinforced concrete and ibeams on a bridge or bunker that needs to be destroyed is a less daunting task than tuning. HPTuners doesnt require that you go to their school at Parris Island though... And yes, thats how you spell Parris Island.

Oh, while I still have the floor, lol, I can only assume that when opperating in a MAF failure, all changes to the VE should be done on the secondary table... right? That is what it is refering to isnt it?

Oh, and by LTFT i was refering to long term fuel trims. Thanks again everyone.

moehorsepower

iTrader: (3)

As JimmyBlue states it is a lot of trial and error, Remember what works for one usually does not work for all. When Nitro Dave had the shop we would have two cars with identical mods done to them, One car would start right up and even idle while the other would surge and die. One took more timing, less fuel ect.The #1 aspect to tuning is make absolutely sure everything is mechanically functioning, non fouled plugs, no burnt wires, exhaust leaks..........

turbolx

amen!

KurtRardin

iTrader: (11)

After Jimmy mentioned the VCM controls in the scanner, I opened it up and noticed several things pertaining to the idle. Next time I get a chance to do some scanning I will definitely try that. And I get what you're saying, MoeHorsePower, about similar vehicles and different tunes needed even with similar mods. I suppose that's what is going to make learning how to tune anoying, lol. Even if I open the compare file its still just a picture for someone elses car, and not necessarily something that will work for me

9000th01SS. I didnt start this thread to light anyones short fuses. If you don't want some smart *** reply, then dont act like I did you some injustice by spelling the name of an author incorrectly. Here's a link to where everyone can find the book http://www.google.com/search?hl=en&q...nnish&aq=f&oq= Or you can look in the sig box for several of the posts above... as the author to the book has actually replied. Unless you have something to contribute, please stop replying.

Thanks for all the good advice everyone. I'm trying my best to take good notes so that the next time I fire up the scanner I can hopefully get a few things smoothed out. Soundengineer's wideband writeup (stock location) is something that I think I'll do as well. Having a new 02 bung welded into my exhaust was something holding me up from getting a wideband.

KurtRardin

iTrader: (11)

Greg, will an exhaust leak behind my header collector affect the oxygen sensor in the collector? Also, should I be making VE table adjustments in the secondary table rather than the primary table (low octane vs high octane)?

Frost

iTrader: (45)

I'd say that it actually facilitates learning since you realize that there is a process that must be understood rather than some tables copied from one place to another...

turbolx

It depends on how close it is to the measurement point. Remember that the pulses go in both directions, so "pollution" from outside air pulsing in through a leak can potentially go upstream by some amount depending on conditions. Ideally, I want no leaks whatsoever.
If one table needed to go up, why wouldn't the other? You'll notice that there are only very slight differences between these two tables from the factory, mostly due to the breakpoints selected. You want the math models (VE tables) to match the reality of the engine's hardware. If you changed the mechanicals in reality, then the math models need an update as well.

KurtRardin

iTrader: (11)

Ok. I wasnt sure if it locked into reading the low octane table only durring a MAF failure. Things are starting to become a bit more clear in my world. I guess from the beginning, where people state that there are multiple ways to achieve a good running car with tuning completely different perimeters, I got a little confused - mainly over how I was going to decide what tuning style I would adapt without any tuning knowledge. At that point I decided that I needed something different to source other than cpig and gary, and thats where your book came in. I gotta say, it spells out a lot of what an EFI system goes to work with, and how each sensor comes into play, and how the ECU might use that data to make its decisions. It also made me realize that a factory ECU has had a LOT of man hours in every table... and making changes to those tables without the background or sophisticated equipment seems impossible in my little world... especially when the end result is a perfect running car. But, in the end, I suppose that if my AFR is correct, the timing is where it needs to be, and it idles and runs without knock... then I'd call that a good tune. Things like "friction airflow decay" are going to beat the crap out of me... not knowing if I would benefit from adjusting it, or weather its a table that absoultely shouldnt be altered unless you're doing something insane like fitting this ECU to run on a massey ferguson tractor. I think it will start to come together for me though. As you can see by the number of posts that I have made vs. the time I have been a member here... I appreciate the search feature!

Frost

iTrader: (45)

Use a controlled approach, change one table at a time and note it's effect. My largest starting detriment was making changes that were too small

KurtRardin

iTrader: (11)

I purposely spelled it wrong in the link, genious, just to show you that if you had searched it that way you would have still found it. The fact that you didnt catch that makes it even funnier. You know, I was trying to be funny in my reply to your initial comment on my spelling error. Somehow though, you took it as a serious insult, and even found a way to call me a bragger...? "oops forgot the smilie to indicate I'm not 100% serious" There's the smartass that I was pointing out. So far you haven't done anything to contribute to my thread, except to fill it with garbage. Maybe that's how you got over 2600 posts in under a year. Its pretty obvious that you don't know how to search since even a google inquirey using misspelled information yielded the same result.

I suppose that if I want to get any more usefull information out of this thread, I will just have to PM the ones who responded with usefull information, since this thread is full of useless arguing.

SD99TA214

iTrader: (27)

this started out as a useful thread........shame.