Poll: LT Headers with hi flow's WILL definitely cause your car to run rich

[Raptor626]

My friend and I are having a disagreement over whether or not LT headers with no tune will throw codes and cause the car to run rich, even with high flow cats.

After having done extensive research I said it undoubtedly would. He maintains that if you're still running cats, regardless of tune, the ecu will adjust. He says this because he has a C55 and says that on the Benz forums everyone is reporting that a tune is not necessary for their cars. So he applied that logic to my car, an L99 SS.


Please pick a side and state why.


This should be good.

[cab2g]

I've heard it both ways (lean and rich), I'm trying to get confirmation in another thread too... http://www.camaro5.com/forums/showpo...5&postcount=34

I personally think it'll make you run rich if anything, but I don't have LTs nor am I an expert in O2 sensors and fluid dynamics...

[Bell040]

throw codes because of lower cat efficiency = yes

run rich at cruising speeds = no
run rich at WOT = maybe



you need 2 polls for 2 questions.


better place for your question: http://www.hptuners.com/forum/forumdisplay.php?f=50

[IROCanSS]

Stupid is as stupid does...

[Raptor626]

Originally Posted by jrhaus76

Stupid is as stupid does...

If something's on your mind you can go ahead and say it. If you wanna make a bitch ass comment like that then I suggest you don't comment at all.

[IROCanSS]

This topic has been beaten to almost to death, only reason they kept it alive is to beat OT again... and again... and again.

If you get headers... GET A F-ING TUNE!

[BowlingSS]

My last two Camaro needed a tune after headers and cats. Both of them also were running rich.

Bill

[RLHMARINES]

I tested a Camaro SS with LT with off road pipe for about 3 days and it was definitely running rich, you could smell the fumes from inside the car on long drives. This car was not tuned because the check engine light was on and it had less than 8,000 miles on the odometer.

[caverman]

From my understanding adding headers allows more air flow which in turn should cause your car to run more lean. However the computer can make small adjustments so it might be putting in more fuel.

The CEL comes from the Cats. The basics behind it this is that there are two sensors reading your cats. One is before the cat to get the initial reading and then one after the cat to get the post cat reading. If the rear sensor doesn't see enough of a change (based on whatever parameters set in the computer) then it will assume your cat is not working properly and thus throw a CEL.

I've heard that because the cat is farther away from the engine it can't heat up enough to burn whatever it needs inside the cat to make the exhaust cleaner. It's also my understanding that the OEM cats have 600 (can't remember the name) cells meaning exhaust holes vs high flow cats have a 200 cell cat. Based on that I would think the 600 cell cat would heat up more as well.

If it wasn't for the cats you wouldn't get a CEL....your car just wouldn't run as good. From my research GM made the OEM tune pretty rich in order to accomodate all the different environments. After all a car in higher altitude is going to act differntly than say a car somewhere that is closer to sea level. You'll pick up close to 10 rwhp just by adjusting the Fuel Trims the correct settings.

I'm no expert but that was my understanding of it.

Of course know that by tuning the car you'll run the risk of losing your power train warranty. Still worth it in my book. Headers and tune made a huge difference.

[Termin8r27]

Originally Posted by caverman

From my understanding adding headers allows more air flow which in turn should cause your car to run more lean. However the computer can make small adjustments so it might be putting in more fuel.

The CEL comes from the Cats. The basics behind it this is that there are two sensors reading your cats. One is before the cat to get the initial reading and then one after the cat to get the post cat reading. If the rear sensor doesn't see enough of a change (based on whatever parameters set in the computer) then it will assume your cat is not working properly and thus throw a CEL.

I've heard that because the cat is farther away from the engine it can't heat up enough to burn whatever it needs inside the cat to make the exhaust cleaner. It's also my understanding that the OEM cats have 600 (can't remember the name) cells meaning exhaust holes vs high flow cats have a 200 cell cat. Based on that I would think the 600 cell cat would heat up more as well.

If it wasn't for the cats you wouldn't get a CEL....your car just wouldn't run as good. From my research GM made the OEM tune pretty rich in order to accomodate all the different environments. After all a car in higher altitude is going to act differntly than say a car somewhere that is closer to sea level. You'll pick up close to 10 rwhp just by adjusting the Fuel Trims the correct settings.

I'm no expert but that was my understanding of it.

Of course know that by tuning the car you'll run the risk of losing your power train warranty. Still worth it in my book. Headers and tune made a huge difference.

I second this.

Mine was running lean after the header install...the headers and new exhaust flow so much more the ECU tries to add more fuel but its usually not enough and not able to compensate fully. I voted yes, but again I think most of the time you're going to run on the lean side.

[mikeSS]

i have heard of lean.

[MarylandSpeed]

I ran my car for almost a year with LT's and no tune. I knew the car was about to get ripped up, and supercharged so I figured why waste the effort. Car ran fine with no issues. Even made decent numbers all told. Are you making the most power, or is your car running the best with LT's and no tune..no in each case. Is the world gonna end if you do not get a tune immediatly after headers..no.

And..the answer to the original question is in the post below. All the dyno runs we did in the header test below are untuned. It is slightly lean down low, and rich up top.

http://www.camaro5.com/forums/showpo...&postcount=131

[Bay Area SS]

I have always heard if anything it will run a lil lean. Every car I have seen with LT's will throw a code eventually. The car will not run proper trust me. Do your self a favor, if you have the money to drop on LT's and exhaust spend a lil more and get tuned. No comparison. My car prior to tune with LT's was runnin lean, threw a code, timing was off etc..

[DonnellyJT]

My TSP LTs with HFCs are throwing codes now. It took a week. I clear the codes and they come back in a day or two. It smells rich to me too. I would say I fall into the typical results category of adding LTs and HFCs before getting a tune.

[jordan 572]

Originally Posted by Raptor626

If something's on your mind you can go ahead and say it. If you wanna make a bitch ass comment like that then I suggest you don't comment at all.

[Rhino79]

Some of the smell is probably because of the hi-flow cats, sure they work, but they can't work as well as 4 factory garbage can cats with smell and emissions. Jannetty did a header test and the car was untuned if I recall correctly and the afr's were high 11's to low 12's on all the pulls.

Would I tune it afterwards, yes. Do you have to? Probably varies from one car to the next.

[Ratt]

I have headers and no tune and the car runs rich. The new Camaros run a little rich totally stock. The VMAX throttle body helps but I need a tune soon.

[Stickboy]

P1133 and P1153 will cause a MIL if not turned off with a tune... and they are for the pre-cat sensors so the answer is yes you will get a MIL without a tune.

[kmcd]

Originally Posted by jrhaus76

This topic has been beaten to almost to death, only reason they kept it alive is to beat OT again... and again... and again.

If you get headers... GET A F-ING TUNE!

[bluetorp]

Narrowband O2 sensors are extremely temperature sensitive. When you move the O2s from the manifold locations close to the exhaust ports down to the collectors on a set of long tubes, you inadvertently change what the sensor reads as stoichiometric because of the change in the operating temperature of the sensor. The PCM still commands what it thinks is 14.7, but because the sensor readings have changed the actual AFR is going to be off to a greater or lesser extent.

With a tune you can compensate for the changed O2 locations and resulting operating temperature by, for example, changing the rich/lean swing points of the sensors.

[Parag]

i put in cam, ported heads, catless LT's, and muffler delete at same time, i was running lean enough to throw a lean code at idle and low rev, and rich over 2000.

so basically, just get a real tune, its hard to try to do it yourself with crappy handheld tuners.