Sorry if this is a stupid question but I’m learning as I go and I don’t know a lot about this stuff. I have a 02 c5z My car is bone stock and I’m thinking about buying some Dynatech long tube headers from somebody off Craigslist. Will it make the car a decent bit louder with just headers? I have the stock TI exhaust, and also would I need to tune the car right after? And with these headers I’ll be catless right? So I wouldn’t be able to pass smog

 

Longtubes will be louder, they wont be smog legal(in addition to the catless setup).

You will get a decent bump in power right away.

A tune isn't required, but you will gain a bit more power from getting it tuned after installing the headers as well.

 

The LTs allow the car to "exhale" very well. Need a CAI intake to equally balance the car for "inhale".

Yes-a tune, dyno or mail order (I used ECS-a forum vendor) will optimize the set-up.

 

+1

As far as Catless, I don't know about Dynatech, but with regular headers you typically have the option of pre-fit mid-pipes with or without Converters. Smog legality is based on whether or not your county does the sniffer test, or only reads the computer...Here in NC there are a ton of rides with long tubes and no cats, tuned for power and pass emissions just fine.

 

headers usually make the exhaust have more of a tuned sound, tune necessary. my cat back was just loud, was going to replace it but waited til I installed headers, now sounds incredible !!!!!( have a high flow cat X pipe)

 

Do it right and get a tune

 

Smog will depend on the state. As others have said a tune isn't required but it certainly helps. If you are planning on doing all the bolt ons, you may want to get everything done at once.

 

Just one clarification - moving the original position of Catalytic Converters is technically illegal in regards to emissions. Long or Mid-length headers will move back the position of Cats (hence 50-state-legal shorties), therefore will technically not pass emissions, if they decide to check the position of your Convertors.

This is NOT directly correlated to the sniffer or computer test, which is run irregardless of the location of Convertors.

 

You are going to need a tune, for nothing else it will be to delete the rear 02 sensors which will more than likely give you problems with the CEL coming on. A tune will take care of these and give you a bit of a crisper response.

 

I agree. It's going to be gasping to a certain extent, without a nice tune.

 

My personal opinion is that it's not so much that you needed tune because of the new headers, it's that you need a tune specific to your car regardless of what you have. The base tune that comes from the factory is very close for what they built the car to be. But it is not perfect because every vehicle is different and a tune using a wideband will set the car up dead on the money. If you I've gone through the trouble of adding mods, then it's just common sense to get a decent tune on the car at the same time. It'll be much closer to the ideal set up and that's really what you're looking for.

 

Interesting hypothesis. I agree that nicely tuned, motor runs far better, even more so with greater modifications.

Although I have never gotten around to hand-tuning post headers, untuned people have reported stumbling, general lethargic response, etc. And of course, there is also the unoptimized full throttle A/F ratio. Key to get right, aka full throttle on the motor.

Optimized VE (Volumetric Efficiency) is another story (I.E. SD Tune...).

 

I wonder how relevant it is. Not many have reported SD tune after headers, to crispen up the throttle response. Not required if still using the MAF...

Everything I hear is 'get a tune after headers', and nothing more. We're talking a couple of minutes on the dyno? Versus hours on the street. Wth?

 

I'm not sure I'm following what you're saying here. Vee is always important because that's what the computer falls back to when there is a throttle transient. Anytime the throttle changes the PCM stops using the MAF temporarily and goes back to ve because changing dynamics of the MAF make it inaccurate. So they use a base table to fuel the car during those times.

It really comes down to how fussy you are about the drivability. In my case, I really wasn't willing to compromise anything so I spent an insane amount of time fixing all those little annoying drivability issues. Can a tuner do that while someone is paying them a living wage? My quick answer would be no. They can get plenty close enough but for me, I'm not happy with anything short of perfection. Once you've felt how nice a big cam car can work at the bottom end you change your mind about this stuff. Jmho.

 

I totally agree with what you are saying, for the most part. What I was trying to illustrate is the inaccurate common knowledge of 'getting a tune', especially after Headers.

You have already mentioned, and I can confirm implementing this, there's nothing like running a fully hand-tuned car on the street. This most certainly is NOT the same thing as getting it tuned on the dyno (or mail-order, or similar).

Where I am curious in your response, is the nature of MAF.
I ran a pure SD tune, with 4" silicone coupling in place of the MAF on the LS2. My throttle response, particularly part-to-full throttle, was tangibly better than running the same tune, with MAF enabled (before when I ran it some MAF'd).
My point is, I cannot see the VE table being referenced at all in this scenario, I do not believe it is, much if any...
Therefore, EVEN if tuned for part-throttle and ironed out the VE table over time - it will make little difference, if still running your MAF

 

I think you've got this completely backward. Your SD tune is using VE only. It's the MAF you are not using. It's likely your MAF is actually unplugged on an SD tune. That's what SD is, speed/density. Take the engine speed and the manifold absolute pressure and cross-reference those to come up with a fuel charge. End of story. No fancy O2 sensors and computers in the mix.

 

I don't think so, I believe we're on the same page - I ran SD on the car (MAF sensor completely removed), implementing several street runs to get the VE calculated [with the MAF inoperational]. It ended up working like a charm, snappy throttle, near perfect fueling (this is besides the full-throttle PE tuning, happens also to be irrelevant of the MAF).

However, I am referring to a VE tuned MAF'd setup. This is where there might be confusion.
IF is the case (i.e. re-install/re-enable MAF AFTER VE tuned), the PCM seems to still be utilizing the MAF for fueling calculations, with the throttle response NOT as crisp. Definite delay in throttle application/transitions.
I don't know what is the deal, in correlation to the VE table and MAF sensor together, when street tuned.

 

I don’t know what the hell any of you are saying 😂😂😂😂

 

Okay, I misunderstood what you were trying to say.

Okay,what happens is when you have a perfect SD tune and then you also re-enable the MAF, what the computer does is it attempts to use the MAF as much as possible. When the engine is cold and until it gets up to the temperature where it will go into closed loop, it will use VE only. From there it uses the mass air flow except when there is a change in map, meaning there's been either a change in throttling or load. There is lag from when the computer realizes you are making a change until it swaps back to the ve table to figure out what it really wants to do. Unfortunately it already has the engine fueled incorrectly because it was attempting to use the MAF for that brief period until it saw that it needed ve to get a baseline number.

Map and RPM are absolute, so there is no lag and no guess work there. MAF takes time to give the computer an accurate reading and it really only works best when in a cruise situation where the throttle is constant.

Keep in mind the way the MAF actually works. They input a voltage/current to a wire and heat it up. They factor in the intake air temperature which may or may not be the truth at any given point anyway, and then they measure the resistance on that wire assuming that the air density can be calculated by how much temperature drop there is on that wire along with what was the temperature of the air causing that temperature drop/resistance. In other words, it's a hell of a mess anytime a change is taking place because it simply takes too long for that to heat up and cool down.

There are numerous tables that help to alleviate those problems but often times they are not tuned when people do a tune. It gets complicated for sure.

 

PS. This is also why anytime you get so much as a microscopic amount of dirt on that MAF all hell breaks loose. The dirt insulates the wire and now the computer can't predict what is happening even if it does have the proper IAT to work with.