Does the corvette ecu have a "learning" feature? For example if you throw on headers, high flow cats and exhaust, which results in the car running rich/lean compared to the stock setup will it correct over time and eventually work its way back to stock a/f's?

Thanks!

Pete

 

I installed stailess works headers, Random high flow cats and X pipe. Picked up 21 HP at the wheels. Haven't tuned yet but plan to. Would be interested in others opinions on whether the tune is necessary.

 

I just put on Kook's and off road x pipe w/no cats.

 

I installed a set of SLP headers (great headers and great results but a royal PITA to install so I won't do SLP again) about 2 years ago. The car adjusted it's A/F mix some after the install but not to where it needs to be. I ran real rich for a long time and then had LS-1 Edit performed. Major difference + I picked up another 8 rwhp on the dyno. It'll cost you upwards of $500 for the full tune but it's worth it.

 

ok listen to this, IF you slap on bolt ons, your gonna increase the AIR vrs the fuel. so your going to be runnning extremly lean. I watched the computer on my car while it was dynoing, if my boy didnt richen my car i would be lookin for a new LS1.

 

thats an excellent point So if the car is not tuned, one should bring it up to full throttle very slowly over time to allow the ecu time to adjust? Forgive my lack of knowledge on this but I am not that familiar with Corvette's(this is my first), do they run in closed loop or open loop at WOT?

Thanks

pete

 

anybody? The million dollar question is will the stock ecu bring the a/f back to stock levels after a header install? I am thinking yes, but only after quite a bit of driving?

thanks

Pete

 

I have had my headers on for almost a year now and haven't had any tuning done yet. I do plan on doing it eventually, but I haven't had any problems so far.

 

Okay... so here is the deal. The computer WILL adjust to a degree over time. What does that mean??? Yes it can compensate up to a point. It takes time to learn so mashing the gas minutes after you make a big change is not really recommended. Depending on your mods or mod type will determine how much you can get away with before you need to have the ECU reprogrammed for the changes. Here is my personal experience so far:
I added a Vararam as my only mod. Car ran a little funny for a day or two then seemed to adjust. Power was up in the SOTP meter. Then I hit my first hot/humid summer day and mashed the gas on the highway. Pinging ensued. Never had that before the Vararam. How will it adjust to that over time. Maybe, but I want to get it tuned to make sure that all instances are covered. (of course I am adding headers as well so I want to get them on first)
So..yes it will adjust. Will it adjust for all situations. Maybe. Are headers your only mod? so on..

Oh and to answer your other question... WOT is open loop. They call that PE (power enrichment) mode and it throws emissions and O2 sensor readings to the wind, BUT it is still a table that needs to adjust for changes.

Will the car drive fine after headers, intake .... yep. Would I personally trust it long term... nope.

Again... just my .02

--Bill

 

If the car has a MAF it will learn the new fuel requirements. The only time I've never seen a MAF compensate enough is with a larger cam and heads, or forced induction.

 

You're getting mixed information here, so be careful. LS1's run RICH when they're opened up; new generation technology, not just a carb. A lot of variables involved including engine RPMs, MAF sensor output, colling system temp., oxygen sensor output, wheel speed, etc. etc. The PCM is programmed to make adjustments richer and leaner, I think on a range of +5 to -5, from the original "0 point" on the fuel injection "map" programmed into the computer. The map controls the fuel trims and there are long term and short term trims in the computer. Blah, blah, blah. Lots of info and there's a fairly good explanation on one of the forum member's web sites, but I can't find it now. BTW, the PCM goes into "closed loop" at WOT.

Upshot, you'll get better performance, better fuel economy, and less soot on the tail if you get the tune. Is it necessary? Were headers necessary? Will it harm your car? Depends on what you call harm....extra carbon build-up in the combustion chamber, more knock=more timing retard=less power, yada, yada, yada.

Do the tune.

 

You increase the air at the MAF and it tells the PCM to send in more fuel to compensate. Very rare to hear of an LS1 running lean from air intake and exhaust bolt-ons; in fact I've never heard of any. Usually means an air leak downstream of the MAF.

 

Not true. Closed Loop is normal mode. To be 100% accurate it is only true Open Loop at cold start. PE mode is a modified Closed Loop but many consider it Open Loop because it is ignoring O2 sensors.

The PCM on GEN III engines only operates in True Open Loop Mode during cold engine startup because the heated O2 sensors need time to warm up to operating temperatures. Cold startup is where the engine runs in speed density mode, whereby it only looks at map/maf sensors, and other information such as engine speed and throttle position. Then it goes into, closed loop mode, but has a Power Enrichment Mode for WOT operation. This mode of operation is a modified version of Speed Density still relying heavily on the MAF for airflow metering to determine engine load, but does not send updates to the PCM like fuel trim adjustments.

In any case...your right. Get the tune.


--Bill


--Bill

 

headers help increase the scavanging of the cylinders,increasing the air moved in and out of the cylinders and opening up the air intake helps increase it even more.more air needs more fuel to make more power.the pcm will compensate until it goes into "safe mode".safe meaning that it will begin to over compensate and your fuel trims [long term]will get near +18%[plus meaning that the engine is actually lean{o2 sensors seeing more air than fuel in exhaust,it then tells the pcm,then te pcm increases the injector on time to increase fuel}.+ numbers mean fuel is being added.- numbers mean fuel being taken out. depending on the designs of the intakes and headers will dictate the amount of compensation.-25% and +25% turn on the check engine light.
also,like somebody else posted,the o2's switch off @ wot and the power enrichment tables take over.the o2's switch back on when you lift.
short and sweet get the tune,you won't regret it.

 

I had Long Tubes/hi flow cats installed and then drove approximately 1K miles and ran rich the whole time. Threw a code shortly after install once but never had a problem after that. Just recently had the car dyno/tuned and LS6 intake installed and seem to be running even richer now than I was before (judging by the amount of soot on the tail pipes). I'll be calling up the tuner to see if he can maybe do something about that.