LDB C5

The headers and exhaust are done, and I drove the Vette on Saturday. Runs great! I was having serious withdraw symptons so the timing was good! Performance improvement is noticable

I have a question for the crew: I know I need a tine to get rid of the rear O2 sensors, but do I need a Dyno tune or will a simple flash tune work? How much of a "seat of the pants" difference between the two?You guys are the experts, let me know..

johnnyvettes

you need a dyno tune to get everything out of the headers . once tuned the 02 sensors should be off or they can turn them off . did I say that no not me

Bluvette1

I assume you are running offroad pipes?(no cats) If so the rear O2's can be shut off in the PCM. If you need to go for emissions though you will not pass. In order to pass you need O2 Simulators. Your 2 front O2 sensors are adjusting your air fuel along with your MAF sensor there is no real need for a dyno tune unless you want a number.

LDB C5

Thanks for the reply

I am running "high flo" cats, but no rear O2 sensors. I have been told by several sponser / tuners that emissions is no problem if the rear O2 sensors are tuned out. What gives?

Just J

I'm interested in this answer as well. I've got the LGM Pro Long Tube headers with high flow cats, and was getting the check engine light. I loaded a Halltech Email Tune and that light is gone. But the question of whether or not it will pass emissions is definitely on my mind.

johnnyvettes

if you have no codes it will pass .

FrankTank

Len, congrats on the headers! You'll have to stop by so I can hear them

To pass emissions, you'll have to
get a dyno tune, and they will simply turn the Rear 02's off (it is the rear o2's btw) and you will pass no problem...you just have to make sure you drive the car about a week so the computer will go back in "readiness" mode.

Don't go the cheap way and buy 02 simulators, ask Dave (DPG about that) he ended up sending his PCM for a mail order tune to just have the 02's turned off.

If my car can pass with the cam and headers etc.. going lope lope lope blub bulp bulp while waiting in line,, your's will for sure

Really the Dyno tune is the way to go, you'll also get every ounce of power out of the headers as well.

Bluvette1

Although you do not have a check engine light, the emission system runs its checks and if you go to the emissions center they will tell you that not all your readiness codes have been met. Depending on the year of the car there are certain codes that have to be met, even throughout the 1997-2004 certain emissions change even though these are all C5's not all the same emissions are checked. We have done alot of LG Headers and always use the simulators. You can leave it alone and try when your time comes up.

johnnyvettes

I am not going to argue with John he know this stuff inside out . just repeating what I have been told in the past .

SupermanZ

Congrats Len....Dyno tune is the way to go.

rudyarias

True or in my case my 2002 Z06 was not passing because the PCM was not reporting the second O2 sensor working. On the advise of the service manager at my dealer. I applied for and received an emissions exemption on my 2002 Z06. I cited that it was a "race car" that was driven to/from the track as well as car shows. Sent in the app and photos of it in the paddock with its One Lap stickers :-)

Mopar Jimmy

I can vouch for the fact that this man knows his sh it and then some! That being said, don't you agree JOHN that he would pick up a few extra ponies with a dyno tune also to maximize the benfit of the long tubes?

Javier@DIDRACE.COM

len sent you a pm

DPG

Don't get me started on the o2 sims. I went through 2 sets of sims, both failing right before having to take emission, go figure. Got tired of it, so went ahead with the mail in tune from Charlie out in Cali. I've heard both sides, that you will pass emissions with the rears turned off, and the other side, failing because the computer is never ready. But the failing has been rare from what I've seen. I guess we'll find out when I go sometime this week, wish me luck.

LDB C5

Hey Dave,

Let me knwo what happens. I want to get this sorted out sonner rather than later!

DPG

Will do. Been driving the car the past couple of days, so hopefully another day or 2 after its done raining and off to get it tested. I would get a code by now. I also sent a pm to Charlie who tuned my pcm to ask what his experience is with emissions and what not. I'll let you guys know what happens, hopefully by Friday.

FrankTank

Every person I have talked to, all different year C5's with heads/cam or supercharger, all running headers have said the way to go is a Dyno tune and shut off or "tune out" the rear O2's. My car passed with flyiing colors..with a good size cam on top of that...it's all in the tune.

Every person I have spoken to about using O2 sims has had mixed feedback..most end up ditching the sims because the don't pass emissions, or short out numerous times as in Dave's case....sure anything is possible...
I am sure plenty of people pass with O2 sims..but the dyno tune is the safest way to go IMO..and you are also getting the added power and full potential out of the headers.



Len- if you have FLP tune it, you will pass emissions, they know they're stuff and it's been proven time and time again.

Bluvette1

I did not mean to start a big problem. All I know is that by turning the O2's off in the program with LS1 edit you would not pass emission. There is no magic in turning them off a certain way that you will pass. I do not know if HP Tuners works differently. As for the problem with O2 simulator going out I have had zero problems with them, maybe a manufacturer's problem that DPG had. Jim as for the dyno tune you can look for about 10 hp gain, I don't think it is worth the $$, unless you want a number. I suggest give it a try with the program shut off if you dont want the sims. That my 2cents.

DPG

Len
Just got back from emissions testing and I passed

Get them tuned out. I also spoke with the guy who did the tune for me and he also said it shouldn't be a problem.

LDB C5

Hey Dave, Great News

I sent you a pm.