cobra502

I need to resolve and maybe learn something from the dilemma I have with airflow. Below, I went through my Trinity logs from stock to where I am are today.

Using the Trinity, I started out with a completely stock Z51 and consistently got 330-340 g/s max from the "MAF Sensor Mass Airflow" parameter at 100% throttle. Then I added an Airaid air filter and basically got the same numbers. Then I added the AFE CAI system and improved to around 350-360. I had tunes created by “Diablew” for the Airaid and AFE CAI steps. A lot of money spent for a little improvement specifically aimed at improving airflow. It seems to me that the engine is telling me it doesn’t need any more flow for it to perform better. It has what it needs. I have heard several times from people that GM has placed a limiter on air flow in the LT1 engine right around where I am experiencing max air flow.

If you increase airflow then you should increase performance, right? Since there has not been much of an increase in flow through the engine by moding the intake system there has to be a restriction someplace. So, I thinking it has to be in the exhaust system.

I am thinking of adding a Corsa X-Pipe. I would think removing the two cats should reduce back pressure and improve airflow. I’m just not keen on spending another $500.00+ on a x-pipe for no more improvement.

In conclusion, I think, no I know, the only thing that has improved the performance of my C7 is the tunes Lew did.

Thanks for your time and help.

SharkGrayStingray

i have the afe cai and corsa double helix and xtreme exhaust. I have 3 or 4 datalogs from my intune with these mods and i can check if i have the maf airflow recorded on them and see what they show for you. give me an hour or so.

SharkGrayStingray

looks like the most i got was 357 @ 84% throttle. Don't have any WOT runs...

Don't know how much help i was...

Higgs Boson

Without a proper tune the MAF will not report correct airflow numbers.

Your mail order handheld tune is not a proper tune.

This is why shops spend big money on dynos, 10K dollar widebands, and lots of training/education....so they can properly calibrate pcm's.

Besides, your airflow numbers are going to vary with weather/density altitude anyways. they are a very poor measurement of performance.

\Boost Monkey/

Man...

So as Higgs suggested, are you working an off the shelf flash tune here? Are you saying you had an outside source provide you with a modified tune based solely on an intake upgrade? Did you send him a data log before or some type of data to base his retune off of? Because honestly I wouldn't even mess with changing the parameters of a tune based only on adding an intake. I would at least wait and add an exhaust system (ie headers, test pipes, X pipes, whatever) PLUS an intake before I even attempted to retune based on upgrades.

Cats are the most restrictive part of any exhaust system, on any car. You need to ditch them to see any type of real improvement. If you want to breath more you have to exhale more. But thats modding basics, sure you know already.

Lastly, as Higgs said its a proper dyno tune or nothing. OTS tunes are only so good. Every car is different and in different environments/parts of the country.

cobra502

Cody,

Thanks for the response. I agree with most of what you say. I'm sure you missed my mentioning Lew Eaton (Diablew) who has been doing my tunes. Dynos are down the road. This project is about seeing how much(little) it can cost to wake this C7 up. For me it's one step at a time and getting answers when something doesn't look right to me. Dynos can get expensive and when I get my answers that will probably be next.

cobra502

Thanks for your response and opinions, that's what I'm looking for. Well, let me try and respond to your comments. No, no, no, no to what you implied about the procedure. As I mentioned, Lew Eaton did my tunes and I think most of you can say he's as good as they come. At each step of the way Lew changed the tune as I sent him logs.

The whole idea of this project is to see how much money one needs to spend to wake this C7 up. Sure, anybody can throw a crap load of money at a car to get results until they blow it up. I'll do it one step at a time and maybe learn something along the way.

Thanks, for commenting and if you have any constructive thoughts why this lack of improvement with airflow is happening, please send it along.

Higgs Boson

Did you buy some wheels from me a few months ago?

The main point of my post was that using airflow numbers from the maf signal for accurate power numbers is dubious at best. An intake will increase airflow but even a slight repositioning of the MAF can alter the Hz vs cfm (lb/min, g/s, whatever) number and this is why recalibration of the maf curve is necessary. This can also throw off spark timing values and other values that reference the maf output and really mess with power output and even transmission shifts.

remote tuning cannot accurately (precisely) recalibrate the maf values, but it can get sort of close so that the trims aren't totally wacky and you can drive your car. it really comes down to how precise you want it i guess.

if you have an opportunity to perfectly calibrate your maf then you will be much better off in comparing airflow numbers.

\Boost Monkey/

You said "no, no no no" but you confirmed that you were sending him logs and he was retuning accordingly? That's what I was asking to get a better handle on your OP. Background to understand your process.

I mean sure, there are multiple limiting factors to how much atmospheric air can or will be taken in. But it's all atmospheric without a charge and depends on density which will change readings. As Higgs said, time of day, weather, altitude etc can greatly affect this. You could literally retune every season for optimal performance year around.

As I said, modifications to free up exhaust flow, improving scavenging, etc is also a large part of the breathing process.

I just don't understand the emphasis on airflow readings from the MAF as a gauge of performance that's all. My bad.

cobra502

No, I did not buy any wheels. I'm the guy from Katy who pm'd you the other day. Thanks for your input. As I understand it you are referring to the old style round MAF. The new slotted MAF can only be orientated one way.

I'll pm you about getting together.

Edd

sycraft

where in Katy, I am in Katy too.

Higgs Boson

I am not talking about maf clocking. airflow readings are altered by maf placement, coolant temp readings vary depending on sensor placement, O2 sensor function varies depending on placement, oil pressure readings depend on where you measure it, etc.

\Boost Monkey/

Have you tried using a DPM to measure your different intake mods versus MAF readings? As stated, MAF readings can be easily altered while even using almost identical conditions.

Mike@DiabloSport

The tune he started with was developed in house on our dyno, with the AFE intake.
The MAF curve should not be an issue here.

Thanks

jimman

Are you talking air flow volume or pressure differentials??

Higgs Boson

He is talking about CFM measured in g/s or lb/min

6Speeder

Using a CAI like the AFE or CKNZ you can actually be flowing more air but the MAF will read LESS air flow. If the tubing at the MAF is larger than stock you are getting more air but the sampling MAF will read less air.

jimman

Ok, for example you have 350 cuin engine running at 4000 rpms, what is the maximum CFM that can be attained?

Higgs Boson

you mean with no air filter, intake, throttle body, intake manifold, exhaust manifolds or headers, catalytic converters, exhaust pipes, or mufflers? or some of those? or all of those?

what kind of intake? what kind of throttle body? what kind of exhaust?

oh yeah, what kind of camshaft? what valves?


shall i go on????

jimman

Re read the question what is the MAXIMUM CFM that can be attained.