Internets_Ninja

Before you read the thread I still agree the GM Performance intake is safe on a stock ECU calibration. The purpose of this thread is not to argue otherwise, but only to share my experience. More details further in the thread.

So I decided to try out the GM intake on my 2017 Z06. Being an advanced tuner with HP Tuners I wanted to see how this only mod would do on a stock tune with no other mods. Essentially there is no risk using it with no tune as GM says as the WOT fueling areas stay very close to OEM, it only goes slightly leaner. But I noticed a huge swing in fuel trims at idle and off idle throttle. My fuel trims were going into the negative 20-30% range at idle and -15-20% range off idle, but then all mid range trims were very close to zero, and right before WOT trims were in the +2% range which is well within the norm and also carries into PE mode. I also noticed my peak boost went from about 10.3 psi to 11.4psi so there is definitely added airflow up top which was expected. Anyhow, in summary I had to tune the MAF curve at idle and near idle ranges to bring the fuel trims back in line, but WOT fueling was nearly unchanged.

Curious if anyone else has messed with tuning this intake?

usrodeo4

I'm new to the Corvette world as I just bought a '16 Z (I did own a '65 Roadster 396/425 HP back in the day)...just curious what your post is referencing? Is there a GM intake manifold that provides more H.P. w/o voiding the warranty? I have been down the "Tuned" road before with my previous 997 TT (750 BHP Turbo build) and would like to keep this car OEM/turn key, but I may be interested in factory performance parts that leave the warranty intact and leave the car "OEM". Any input would be welcomed.

Pacembellum

You say your fuel trims were negative at idle but was it running a lean A/F?

C7/Z06 Man

PS: 1.4 psi increase in boost should put some additional pep in it's step. Any track or dyno results to report?

Internets_Ninja

Google C7 Corvette GM Performance Air Intake. It replaces the stock Airbox and filter. It is not an intake manifold. GM claims 11HP gain with no tune needed and retains complete warranty if the dealer installs it for you.

No I think you misinterpreted me. The idle and off idle area fuel trims went way negative meaning it was running rich at an idle. Then I said the WOT( Wide open throttle) fueling areas went slightly leaner than stock fueling which is already rich, especially when COT kicks in. So at WOT it is still plenty safe which is likely why GM says no tune needed. But I was very surprised to see how much fueling I had to pull out in the idle areas. It would probably benefit from some VVE tuning as well but I'll get to that later.

Nope haven't been to the track. I did feel faster but to be honest its hard to tell with that much power. Since the datalogs showed my peak boost hit 11.7PSI multiple times in 3rd and 4th gear I have to believe my butt dyno was correct. (I have an M7 and also live in South FL at 0 Feet). I did some data logging yesterday during the heat of the day and my Peak boost was only 11.4 PSI so I would really only say you get 1lb of extra boost. Anyhow, I ended up tuning the car the rest of the way and it is definitely faster for sure.

Pacembellum

I guess what I’m saying is “so what”. Did it make it go “too rich” or did you NEED to adjust those fuel trims or was it working fine “as designed” ?

Internets_Ninja

I guess that is for you to decide on your own. I posted about my experience. GM says its fine without a tune, I'm sure their calibrators are better than me. I just found it very surprising I had idle fuel trims pulling out as much as 30%. I planned on tuning my car anyhow so I tuned for the intake as well like I would any other intake. Generally you want fuel trims with -5%/+5% everywhere. So I'm not here trying to convince anyone that GM is wrong, but only sharing my experience from a tuner level point of view.

ssmith512

For the tuning ignorant (I am at the top of that list), would these large changes in fuel trims manifest themselves in some drivability form ,or anything that would be noticeable (other than by logging with a wideband)?

Thanks in advance for educating me a tiny bit!

Internets_Ninja

Simple answer, no to both questions. No drive-ability issues and you will gain power. The car is still pig rich at full throttle on the stock tune with the GM Performance intake. Without being a tuner or data logging before and after you would never know.

Complex answer, the ECU has the ability to add and subtract fueling up to approximately 30% from commanded based on fuel trims. The trims change as the air temperature, humidity and density changes to always be where the ECU wants it. If you are at -30% fuel at idle, that doesn't leave a lot of room for the ECU to pull out any fuel if you go high up into the mountains or something and the density decreases greatly. The short term trims will still kick in and pull out fuel so in the grand scheme the car will be fine. My peak negative trims were 30% at idle but most of the time they were about -25%. After my tuning they are back to about -3%-5% which is about normal for the summer time in South FL. Typically they will creep into the positives on cool days during FL's mild winters, especially in the morning where its the most cool and dense air of the day.

EVRGRN

Interesting thread, thank you.

dar02081961

-25% or so fuel trims at idle will set a code. Were you setting codes?

If you have negative fuel trims at idle yet you have in range fuel trims when driving the car you have an issue not specifically related to the intake (if its properly installed).
Of course negative fuel trims means the PCM is removing fuel.

If the PCM is removing 20-30% of the predicted fuel requirement at idle that means 20-30% of the anticipated airflow is absent.
That is a bunch of air not being seen by the MAF sensor, more than any CAI manufacture would intentionally allow.

I know you say you tuned the trims out at idle but the CAI shouldn't have required you to that.
I am wondering if something else may have been wrong? Did you clean the MAF sensor while doing the intake mod?
Negative fuel trims (to little air at idle) is a very rare condition, as opposed to to much air (positive fuel trims) which is quite common and often due to vacuum leaks.

usrodeo4

Interesting numbers....so your data logger saw peak boost go up 1.4 psi, from 10.3 to 11.7 psi? I am new to the Z06, what is the established/published OEM peak psi boost? Chevy says the CAI is good for 11 H.P. (I assume ASE B.H.P) but as I recall the old boost guideline is 1 psi is worth approx. 5 to 6% BHP, so a 1.4 psi boost would be, well we can all do the math but well over 11 H.P. As you seem to have some tuning experience with the Z that I do not yet have I would love to hear your comments. Regardless, as I am planning to keep this car OEM it looks like this is the only upgrade I have available so will be installing this soon.

usrodeo4

Agreed...

C7/Z06 Man

If I remember correctly at WOT the peak OEM boost is 9.4 psi in the C7/Z06. In my car the 'few' times I have gotten a chance to watch the boost gage it has never exceeded 9.4 and usually falls a little short.

BrunoTheMellow

So your car was already reading nearly 1 psi higher than stock and it went up another 1.4 psi from an intake box and filter only ?

The box that only claims like 11 hp on the z06 and hasn't been proven yet? Maybe I missed it but I haven't seen a single before/after dyno on it.

When on the other hand, the largely proven halltech intake adds only 1.0 psi and 40-50 hp... My car. Halltech only, no tune. Datalogged 10.3 max boost.

Sounds fishy. Did you run at 100 ambient and then 30 ambient?

Internets_Ninja

I posted here to ask if anyone else has had a different experience. I am an advanced tuner and have been working on cars and modifying since I was a teenager. I'm sure everything is installed properly, in fact I checked over everything again because I surely though I had an intake leak of some kind to see trims like this. All I have to offer is my experience with this intake and screenshots from the datalogs before and after installation and then tuning which you will see below. Also I was mentioning boost by memory so it was a peak of 10.3 on the stock intake and 11.46 on the GM intake. The peak could have also had to do with some of my tuning. Unless you're a tuner it wont make sense if I told you what tables were changed. Anyhow, thats still a solid 1PSI increase in boost.


You all are calling me out like I'm making things up. No codes. MAF isn't dirty. If I was really down 25-30% of airflow I would likely have idle issues. I was just sharing my experience and I could not find anyone with any sort of information or dyno or anything on the GM intake.


Stock Tune, Stock intake.



GM Intake peak boost, tuned by me. Sorry peak was 11.46 not 11.7. My original post was by memory.


GM Intake, stock tune. LTFT's pegged at or near -25%, STFT still trying to pull fuel from one side. No I do not have an exhaust leak and no intake leaks.



GM intake, My tune including adjusting MAF. Strangely I did not have to pull 25% of fuel out. They came in line after I pulled out around 10-12% depending on the area.

Internets_Ninja

My thought here is that the velocity across the MAF has increased at idle, so it is idling higher in the Hz range, hence adding more fuel. Then the O2's are saying woahhh take fuel out. This is not uncommon with aftermarket intakes but I haven't observed such a large swing before.

Internets_Ninja

Its HAF here in South Florida right now and the logs were all in within a few days of testing, same hot weather. As posted above it was actually only 1.1 PSI peak difference. But you can clearly see that with the GM intake the boost level is higher comparatively at all RPM ranges.

dar02081961

Stock Z06's can see 10.5-11 psi on data logs.
The 9.4 psi number given by GM is the lowest you will see at any point after going WOT, even on the hottest day in the summer.
Kinda of a worst case and consistently repeatable number.
You will normally see between 10 and 11 on most data logs especially in the cooler months of the year.

dar02081961

Cant see it here but are you logging the closed loop open loop PID?
You are probably in closed loop but often times if you are not above 190* engine coolant temp you wont go closed loop.
The only way to be sure is to log the PID.

Point is if you are using a cooler thermostat you may not go CL when you normally would anticipate.