0Chuck CoW

Ideally, fuel trims should be ZERO in a perfect world. But, that's not likely. I don't mind fuel

trims so long as they are within 0-5 POSITIVE.... I do not like the way the cars run with even as

little as -3%... They shake and run poorly..... Fuel trims above 5 I don't like. Read below....

Ok... While the ECM can adapt to upwards of 20% positive (lean) or so and not nearly

as far Negative (rich) what you don't want is to be running around with a car that's adding 20% to

the fuel calculations (in the form of Fuel Trims) or taking away 15% from the mix.

The car will never run well like that and your mileage will suffer. The second thing is that

one axis of your timing table is in GRAMS/SECOND of airflow and when the airflow or fuel

relative to airflow is manipulated weird things can happen.... This is why I STRONGLY

recommend using the VARARAM air intakes ESPECIALLY ON C6 CORVETTES with automatic transmissions.

In addition to having a reliable, clean, smooth airflow table your transmission will always

shift properly and last a long time. What people don't know (and most tuners too)

is that (on A6 cars especially) the transmissions line pressure values are calculated based

on the airflow values derived form the readings that the MAF takes.

In other words.... The more airflow that comes in, the greater the torque the

engine will produce....and the higher the TCM will elevate the line pressure to prepare

for the increased torque coming from the engine.....

Air intakes that grossly skew the airflow or make turbulence or that VORTEX in the pipe

are VERY BAD for tuners and worse for transmissions.

ONE IMPORTANT THING TO NOTE.... if you're installing a new air intake and you

are under the impression that the Computer will eventually LEARN the WOT fuel.....

You are WRONG. WOT fuel is "COMMANDED" however you only get what you

COMMAND if your MAF table is calibrated correctly... As airflow goes up, the MAF flow should go up....

from roughly 6 grams of airflow at idle for most cars to as much as 500 grams of air for the

C6ZO6 and even more when you add power adders.

Let's say for instance your MAF ERROR is 3%.... Ok, so your Trims are adjusting 3% of about 6

grams of air.... You're talking a VERY small change to your idle airflow and the pcm and

adjust for that.....

Now, at the higher rpms, your making 400-500 grams of air and you're off the same 3%....

That's a much bigger number and an even bigger problem.... Either you're WAAAAY rich or

WAAAAAY lean..... Bad news. Now, let's say you've got an A6 transmission....

and you're running lean cause your maf is wrong..... Just realize that your transmission is

producing WAAAYYYY LESS line pressure and the shifts won't feel good and the trans is

likely slipping.... Especially at WOT.... Bad news again.

Listen to your tuner....Take the cold air advice he gives you....and...

GET YOURSELF A VARARAM to avoid problems.

And don't forget the Chuck CoW TUNE!
Chuck CoW

C5Wolfe

I'm not saying your wrong but I have never heard of a blackwing causing a hydro-lock situation but I personally know of a c-5 with a vara-ram which did [destroyed his engine]. We are subject to flash flooding down here on the beach [outerbanks] so You have to be carefull after a rain.

rebelheart

Sorry to doubt you, but it is always someones uncles, brothers, cousins neighbor who heard of a vararam causing a hydro lock.Not once have I seen or heard of any real proof of this.In New Orleans we have the worst streets and drainage with almost everyday thunderstorms that would wash most cities away,yet within all three local Corvette clubs and many ,many Vararams,not one single problem!

combatvet

I purchased a 04 Z that had been modded by the previous owner. It has Borla Stingers and Dual K&N cone intake. I have gotten the Service Active Handling and Service Traction Control messages. Concord Chevrolet is telling me that the intake could be causing this problem. I'm no gearhead or backyard mechanic by any means, these are the codes that are on the service invoice...C1278,P0101, P0174, C1288. What do they mean and how can I get them fixed? The service message came on again and after I turned it off and back on it cleared the message. Any help will be appreciated, Thanks.

C5Wolfe

No, It wasn't an uncle,brother cousin or neighbor, just a good friend with a "97" Vette!
The reason your Vettes in New Orleans don't hydro lock is that they are probably stolen before their owners have them long enough to encounter any water!

Silverbullet00

Side Bar:


I drove through a nightmare rainstorm from Norman, OK to FT Worth, TX last spring on our way to the Lone Star Corvette Club's Classic show based at Texas Motor Speedway. Vararam B2 has been on my car for several years. No PROBLEM!

0Chuck CoW

ROCK ON! Told ya so!

Chuck CoW

rebelheart

Or even more likely,our corvette owners are bright enough to not drive through foot deep waters!

red97vette

So even if im not getting a check engine light (im still not, after 80 miles of driving) Im still probably running lean? If im understanding you correctly, at idle the car is correcting for the lean condition by adding fuel (not an ideal solution) and at WOT it is not correcting at all, and im running lean as hell? I would hope the computer would look at the A/F ratio throughout the power band and correct for any problems accordingly, by adding up to ~20% more fuel as it as fit where it was needed. I would think the computer would trigger the check engine light if it detected that it was lean, no matter than the RPM, if more than the 20% fuel it can compensate for was required. Is this not the case?
Im not an A4 guy, since I have the Z, so the tranny isnt an issue..

C5Wolfe

We Outerbanks Vette owners may not be that smart but were smart enough to build out homes "above" sea level!!

C5Wolfe

P.S.
Rebelheart, I'm just having fun with you so take no offense, I think Louisiana and especially New Orleans, New Iberia and the whole area is one of the most beautiful places on the planet!
You also have the best author in the world [James Lee Burke] who writes my favorite books that are based in new Iberia.
Have a great day friend!
Dave

SoDiezl350

I made a detailed post in this thread a while back that might explain things a bit better: http://forums.corvetteforum.com/c5-g...ink-i-may.html

To summarize:

Under part throttle, the ECM uses data from the o2 sensors as well as the MAF to determine the amount of fuel necessary to achieve a stoichiometric(14.7:1) air fuel ratio. The MAF measures airflow while the O2 sensors measure air fuel ratio. The ECM will use a table into which it plugs the MAF readings to determine the amount of fuel it has to supply. If the O2 sensors show that based on the MAF data the air fuel ratio is not stoichiometric, then the air fuel mixture is adjusted to match the desired AFR and recorded as a long term fuel trim. This is called closed loop mode because it repeatedly analyzes the O2 sensors to achieve a target AFR.


Under full throttle, the ECM only uses MAF data to determine fuel requirements. There are numerous reasons for this that aren't particularly relevant. The main point here is that there is no feedback from the o2 sensors to ensure you are getting the correct air fuel ratio. Generally, most mods do not require the MAF sensor calibration to be adjusted. Even long tube headers do not affect the MAF calibration. They require a new tune because the Volumetric Efficiency of the engine has changed, but the MAF calibration stays the same as the actual flow characteristics of the intake have not changed.

In the case of the Vararam, the MAF calibration has to be adjusted because it has significantly modified the intake flow characteristics. The 2 step solution to this problem is to purchase a MAF screen as well as get a tune. The screen is there to ensure the airflow remains laminar instead of turbulent while the tune is necessary to recalibrate the MAF.
IMO, both are necessary as it is very difficult to calibrate a sensor which has to operate both under laminar and turbulent flow. The tune is necessary because despite the screen, the intake still seems to skew the sensor readings down, meaning the airflow is greater than what the MAF is measuring.

rebelheart

Yes indeed!Cajun country has a beauty all of it's own.

blkbrd69

Great post.

0Chuck CoW

The car can NOT check itself at WOT nor does it have wideband O2 sensors for self calibration.

At part throttle, the factory O2 sensors can "trim" the fuel plus or minus to make it run correctly,

but at WOT fuel is COMMANDED based on the MAF sensor reading and a lookup table.

If the MAF sensor reading has changed, then the WOT fuel will be plus or minus by the amount the

MAF sensor is out of calibration.

The problem is that part throttle uses very little airflow and 3 or 4 percent is not a big deal....

However when your breathing 400 grams or so of air at WOT, 3 or 4 percent

rich or lean is a VERY BIG problem. As the RPMs go up, you get progressively more

out of wack and it becomes more and more important to tune the more mods you have and the

more air the engine breathes.

NOW, you might not be moving much more air with your new air intake (any random intake)

but due to flow characteristics which are specific to each one, a cheap intake

might not flow much more air, but because of it's design and shape, it might make the pcm "THINK"

there is more or less air and even the wimpy-ist of air intakes that flows NO MORE AIR

than stock, can drastically hose up your car by throwing the MAF readings grossly out of range

in either the rich or lean direction.... Sadly, only a tuner would be able to tell you what's wrong.....

SO, when Chuck CoW says "USE A VARARAM" if I'm tuning your car....

You can now see why we make such recommendations.

It's something PROVEN, reliable, and plays nice with the MAF and ECM

and I've tuned them 1,000s of time with good results....

Good reason to use one.

Air intakes....ARE NOT JUST AIR INTAKES.... They are EXTREMELY IMPORTANT.

Stay TUNED!
Chuck CoW

red97vette

Thank you for your detailed reply, very good information, I appreciate it!
I got the check engine light after around 100 miles of driving and after your detailed explanation it seems wise to remove the PD, which is what I just did. I hope that running the vararam with the stock air bridge does the trick. I do realize that its probably going to mess with the tables a bit, but hopefully runnable now with out triggering the engine light.

0Chuck CoW

That will make it so tuning is not a necessity.

Chuck CoW

papafrancisco

This is my understanding:

PD = external tuning

No PD = internal tuning, maybe

PD = increased HP of some sorts plus it looks cool. correct?

M56x-11

Hmm, I just installed this system without the PD. I'm not throwing codes as of yet. But the car is now dying when I come to a stop?
Any suggestions? Never did this prior to the installation of the VR2.

04blackice

Get halltech screen.no more light