Look at my signature and tell me if Im running lean or rich. I know that my tuning on it isnt up to par. I know it has to be a little off if not alot. What can I use to correct it?

<small>[ November 30, 2002, 03:44 PM: Message edited by: onebadss ]</small>

 

My guess is your running lean with headers and the HPP3. Just a guess, so you should book a session on the dyno w/ wideband and have a way to tune it, like LS1Edit or at a minimun a MAF Translator.

 

"Look at my signature and tell me if Im running lean or rich."

I'd need to be psychic. Your sig tells us absolutely nothing about your fuel/air mixture. A wideband O2 sensor will tell you exactly what's going on or Autotap (a must have, IMO) will give you a good idea.

 

Colonel's got a point there, but looking at your mods, most of them generally increase air flow so I'd have to say your on the lean side. If I'm right then you've got very crisp throttle response and it noses over a little on the top end. Again that's just a guess, You'll have to dyno it to be sure.

 

Increasing the airflow doesn't necessarily mean leaning the mixture. The PCM learns as it goes. It might be leaner to begin with when new mods are made but before long the mixture will most likely be right back where it was.

Actually, it's been my experience that suddenly increasing the airflow (like installing a lid or removing the filter) causes a richer mixture temporarily due to the PCM overcompensating initially. I can remove my filter and watch my WOT O2s go from .870mv to .930mv. Make another pass and watch them fall to .890. After another couple of passes they'll be back down to .870mv.

 

Colenel: Is there anything else that I could use to determine if I running lean or rich. Ive had lots of people tell me a MAF translator and then some tell me to dyno it. Oh by the way, whats an O2 wideband sensor and where can I get it. Do you think that I could take it to a performance shop and they can tell me where I stand if I didnt want to purchase an Autotap? Then on your last reply you said that the PCM learns as it goes, so does that mean that my car will eventually go back to its correct ratio after a while. Could you give me what each of my mods would do whether it would be leaning or richening it up.

 

</font><blockquote><font size="1" face="Verdana, Helvetica, sans-serif">quote:</font><hr /><font size="2" face="Verdana, Helvetica, sans-serif">Originally posted by onebadss:
<strong>Colenel: Is there anything else that I could use to determine if I running lean or rich. Ive had lots of people tell me a MAF translator and then some tell me to dyno it. Oh by the way, whats an O2 wideband sensor and where can I get it. Do you think that I could take it to a performance shop and they can tell me where I stand if I didnt want to purchase an Autotap? Then on your last reply you said that the PCM learns as it goes, so does that mean that my car will eventually go back to its correct ratio after a while. Could you give me what each of my mods would do whether it would be leaning or richening it up.</strong></font><hr /></blockquote><font size="2" face="Verdana, Helvetica, sans-serif">A wideband O2 sensor is what dyno shops use to monitor fuel/air. They are quite expensive (a couple thousand dollars I believe.) I was saying that if you really want to know exactly what your fuel/air ratio is you need to go to a dyno shop that has a wideband O2 sensor.

Or, if you can't find a shop with a wideband you could at least get a good idea of your air/fuel ratio by checking the WOT O2 readings.

I can't think of one reason any LS1 performance enthusiast should be without Autotap or some other diagnostic scanner.

A MAFT does not tell you fuel/air. It allows you to adjust your WOT fuel/air and adjust the base settings to get Ltrims inline.

"so does that mean that my car will eventually go back to its correct ratio after a while."

Your PCM will adjust until it can maintain a stoic mixture (14.7:1) during closed loop operation (you are in open loop during WOT operation.) Wherever your WOT mixture (see, your WOT mixture is based on what the PCM has learned while in closed loop so indirectly PCM fuel cell changes do effect WOT operation) is once this is accomplished is where it's going to stay unless you change it with a MAFT or programming. So the answer to whether your fuel/air will adjust back normal is yes and no.

BTW, the PCM only has but so much range of adjustability. Once the Ltrims reach + or - %25 no more adjustment can be made. Autotap will tell you what your Ltrims are.

As I've said before, closed loop fuel/air should not be effected long term by airflow increasing mods so long as the fuel system is adequate since the PCM will make corrections to maintain stoic. WOT can be indirectly effected though. Just because the WOT is based off of the closed loop doesn't mean that the WOT will be corrected as accurately as the closed loop.

Here is my best advice. Get it dyno tuned with a wideband O2 sensor or at the very least use a diagnostic scanner like Autotap to set your Ltrims at + or - %5 during part throttle steady state cruising, your O2s at .870-.910mv during WOT operation, and ensure that you're getting no knock retard (knock retard is a whole nother discussion.) You'll thank yourself for getting a diagnostic scanner when problems arise (such as when your SES light comes on and you don't know why) and if you're serious about getting the most from your car you'll end up getting it eventually anyway.

 

I'm moving the to Computer Diagnostics and Tuning... <img border="0" alt="[Burnout]" title="" src="graemlins/burnout.gif" />

 

So if I was to take it to a performance LS1 specialist and they tune it, is there any reason why I would need to buy a MAF translator? When they tune it will they take care of the air/fuel ratio? What all consists in the tuning? Do you know if MTI does the tuning?

 

Once I get the car tuned, will it ever mess up again. Meaning will the ratio be thrown off after a while? What kind of tuning or computer like tools/parts will I need to purchase to keep my car up to spec. Just because I took it in to correct all that needs to be corrected, can it ever go wrong again?

 

You'll only need a MAFT after tuning if you should decide to change the fuel/air ratio (like for running nitrous or for running lower octane fuel), the MAF sensor, injectors, or make major changes to the engine like a different cam. So other than something like that, no. Your tune will stay where they put it indefinitely and should require no further tweaking.

Yes, MTI does dyno tuning and yes they will take care of the fuel/air/timing/idle/and whatever else you want like getting rid of TQ management or turning off the rear O2 sensors, etc... They can pretty much do it all. I don't know what they charge. Give 'em a call and talk to Jayson (the owner.) 281-870-8787

 

I just called MTI and they do tuning there, however I had no idea that it was going to be that expensive. I was thinking like a $100, but I guess I was wrong. Do you have any other suggestions. Is there any kind of device or whatnot to do all the tuning myself? I really cant afford to let them do it, but they do however tuned it in the future if you make any other mods. Thanks.

 

"Is there any kind of device or whatnot to do all the tuning myself?"

Yes, LS1Edit will let you do for yourself anything MTI can do (but you gotta know what you're doing.) For simple adjustments to the fuel/air your cheapest route is the MAFT.

 

What is LS1edit? Is it a program that you install on your computer?? Is a machine? .....???? How much is this product? Would I be better off letting MTI do it or buy LS1edit, learn it, and peform all the tuning myself? Im sure that its gonna take more than an hour to read and understand LS1edit.

 

Don't take this as a flame, but you REALLY should have read up on all of this BEFORE you started your mods. Surely your A/F ratio is off considering the mods you have. You are 'probably' running lean which can be damaging to your engine depending upon the severity of it.

But anyway, to answer your questions. LS1EDIT is the same thing that MTI uses. It is software (along with a cable) that you will install on a computer. It gives you control over many aspects of your computer. It is the best tuning tool so far for your LS1. However, you can really screw up your engine with it too if you don't know what you're doing. It is also $550 + $100 a year for updates. That does not include the cost of monitoring software (ATAP, EASE) and a laptop. My advice to you is to either let someone else do your tuning, or you need to do a few weeks worth or reading to learn everything you need to know to get started tuning on your own. Search the archives of this board and Ls1.com and read, read, read.

<img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

The Colonel is 100% dead on. You really do need a wideband 02 in order to properly monitor your A/F. But I do have one question for the Colonel (or anyone else that knows). How can a MAFT work when the B1 & B2 S1's are taking erronious readings? In other words, I don't see how you could possibly trick your ECM into running lean or rich for any extended length of time when the post combustion A/F will end up too rich or too lean. Why wouldn't the ECM just override the MAF? It knows what is happening at the end of the process and it doesn't agree with what it's reading at the beginning. It seems to me the only way to permanently and correctly adjust A/F is to reprogram the fuel enrichment tables so the computer is working towards a new optimal point. Not trying to flame by any means, just wondering.

Also, as an alternative to LS1Edit, you may want to consider the Predator. It's handheld, comes with the cable attached, allows A/F adjustment up to 1.5 points, allows timing adjustment up to 2 degrees, is net upgradeable, can be custom tuned, has a built in real time diagnostics scanning capability, and costs way less than Edit. E-mail me if you're interested and I will give you the info. I can also put dyno packages together for anyone who's in the Northern Ca. area through my friend's shop. For the time being, the Predator is the only real competitor to Edit. It won't let you change as many parameters, but it has just enough adjustability to get your WOT A/F where it should be (in most cases). And you don't need a laptop either. Just something to consider. <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

 

"How can a MAFT work when the B1 & B2 S1's are taking erronious readings? In other words, I don't see how you could possibly trick your ECM into running lean or rich for any extended length of time when the post combustion A/F will end up too rich or too lean. Why wouldn't the ECM just override the MAF?"

Very simple. The PCM is only learning when it is in closed loop operation. You're in open loop when at WOT. You have a base setting and a WOT setting on the MAFT. Once your base is set (meaning that you get your Ltrims where you want them) you can make adjustment to the WOT mixture. These adjustments have WILL NOT be learned out by the PCM since they will only be affecting the mixture at WOT when the PCM is NOT learning.

Clear as mud now? <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

 

Also bringing this down from a few posts ago for you to re-read. <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

"Your PCM will adjust until it can maintain a stoic mixture (14.7:1) during closed loop operation (you are in open loop during WOT operation.) Wherever your WOT mixture (see, your WOT mixture is based on what the PCM has learned while in closed loop so indirectly PCM fuel cell changes do effect WOT operation) is once this is accomplished is where it's going to stay unless you change it with a MAFT or programming. So the answer to whether your fuel/air will adjust back normal is yes and no."

 

OK, I think I get it now. A MAFT really only adjusts WOT A/F which won't ever be corrected since it's using data from closed loop. The part I still don't quite get is what part the closed loop base setting plays. If I am understanding correctly, the MAFT is setting a base in closed loop for use in open loop. So why doesn't the ECM still compensate for this false reading? Thanks for the info, it's much appreciated. <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

 

You may be fully understanding but just to make sure I'll try to be as thorough as possible.

There are TWO adjustments on the MAFT. One is called the base setting and one is called the WOT setting. The base setting is used to bring the Ltrims close to zero. Some people like 'em a little on the positive side. Some people like 'em a little on the negative side for different reasons. The point is to get them fairly close to zero to give the PCM a good place at which to start.

Scenario...

You've just changed from 26.4 lb injectors to 30 lb injectors. You drive it around awhile to let your PCM learn. Let's say the Ltrims were zero before the injector change. Now your Ltrims are negative (probably about %14 negative since the new injectors flow about %14 more than the old ones) indicating that the PCM has pulled some fuel in order to get the idle and part throttle (CLOSED LOOP) back to a mixture of 14.7:1 which is a theorectical .450mv as read by your O2 sensors (in actuality you will notice that your O2 readings switch back and forth from lower than .450mv to higher than .450mv over and over but the average is about .450mv during closed loop operation.) Let's say that your WOT O2 readings were about .870mv before the larger injectors. What will they read now? You guessed it. They're reading higher than .870mv. Maybe .950mv or so. This is too rich for best power. The closed loop mixture adjusted back to where it was supposed to so why didn't the WOT O2 readings adjust back to .870mv? [READ THIS PART CAREFULLY] Because the WOT fuel cells (again, WOT is ALWAYS open loop meaning that the O2 sensors are NOT being read by the PCM) is an approximation that is merely based, and I'd say rather loosely, on what the PCM learns during closed loop. This relationship between open loop and closed loop is NOT a 1:1 ratio. When the PCM subtracts %15 from the closed loop fuel cells it doesn't subtract %15 from the WOT fuel cells. I don't know how much it does subtract but it is nowhere close to %15. Well why is that? You'd have to ask GM why they programmed it that way. It works fine when the engine is stock and that's all they really cared about.

Now, as we've already stated, the MAFT has TWO settings. The first one we adjust is the base setting. If we set it on -%15 we should get the Ltrims back close to zero. We're doing the Ltrims' work for them by decreasing the reported load from the MAF sensor. Now we give it some driving time to let everything settle in. We recheck the Ltrims. If they're still off we make another base setting adjustment. Once we are satified with our Ltrims we check the WOT O2 readings and make adjustments using the WOT **** on the MAFT. These changes will NOT make any difference on the Ltrims or closed loop fuel/air mixture whatsoever.

That make sense? <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

<small>[ December 05, 2002, 08:30 PM: Message edited by: Colonel ]</small>