NoGo

iTrader: (2)

We havn't been hanging you out to dry Deezel. Binks has been running some great tests with me in tow lately, I have been waiting for the results.

The Platflorm:
Binks's Z06 Corvette. Grand-Am Cam and other boltons. Typically runs with MAF. Has an onboard wideband .

The Test:
Binks has spent alot of time trying to get his edit VE table dialed in according to the equation that I showed above. He has a very fast data recorder in link with his wideband so data detail is very good and near ideal for developing an 'on the run' VE table. After dialing in his VE table above the trials began. Binks's runs in open loop at all times (no sissy narrow band O2's )
The trials involve Binks experimenting with 4 different combinations and checking the target a/f ratio against the lambda table:

Trial 1: Nogo equations with MAF
Trial 2: Nogo equations without MAF
Trial 3: Gamover equations with MAF
Trial 4: Gameover equations without MAF

Trial 1: Modified VE Curve (NoGo Eq) - With MAF
The car accuratly tracks the open loop a/f table. Throttle response appears to be good with transitions happening quickly and to the desired a/f ratio. The car appears to drive correctly with proper a/f ratio's. Binks verified this. The car drives well in this condition.

Trail 2: Modified VE Curve (NoGo Eq) - MAFless
The car does not accurately track the a/f table. All a/f ratios are about 15% too rich. Throttle response of the car appears to be sluggish with the target a/f ratio being much to rich. Transition between a/f ratios, however, is very fast. The car appears to be sluggish and most likely heavily loaded. Binks verified this "Car drives like ****".

Trial 3: Modified VE Curve (Gameover Eq) - MAFless
The car does not accuratley track the a/f table. Part throttle a/f ratios appear to be erratic at best and on throttle transitions drop the a/f ratio much to far. The transition between a/f ratio's is nearly instantaneous though. At best, the car looks confused as to what a/f ratio to go to. The a/f appears to be in the right ballpark but very rough. Most likley the car ran very erratic. Binks: "Car ran better"

Trial 4: Modified VE Curve (Gameover Eq) - MAF
The car does not accurately track the a/f table. All a/f ratios are exceptionally lean. The a/f of the car is over 16:1 most of the time. Throttle response is most likley non-existant with the car most likley cutting out the majority of the time. Binks verified this "Runs better than MAFless but still SUCKS". After seeing this data I was surprised the car even ran.

CONCLUSION:
Bottom line is that the VE table is not applied the same with the MAF connected and the MAF disconnected. There is a fueling difference of about 15% between the two operating conditions. Any car that runs with the MAF disconnected should have a very different VE table than a car that is intended to run with the MAF. You can't just have one VE table and decide to run MAF one day and MAFless the next.

The Nogo equation appears to work very well for cars that are intended to run with the MAF. Drivability and throttle response improve and target a/f ratios are very accurate. However, the NoGo equation is too rich for cars that are intending to remove the MAF.

The Gameover equation doesn't appear to work well for cars that are intended to run with the MAF. The resulting VE values skew the a/f far too lean. The gameover equation appears to provide a better target a/f for cars intending run MAFless, but still not good enough to go right from the spreadsheet to MAFless.


If you are intending to go MAFless, find somebody with a dyno and set aside the afternoon. Its not that hard it just takes a while if you don't have the Mission Control setup that Plan B has.

Those are the results folks.

Use the NoGo equation if you plan on keeping the MAF.
Don't use either equation if you plan on going MAFless......find a dyno.

Thanks Binks

deezel

Wow, thanks for the update and the hard work, NoGo and Bink.

marcink

Fine, I plan to keep my MAF so I will use NoGo equation. But does it work the same for cars with the displacement changed from stock? Because if the maximum value in the Edit Main VE Table depends on displacement I would suppose there is something missing from the equation.

And what about the Secondary VE Table? Anybody has figured out already what is it used for? Maybe this one has something to do with the MAFless operation?

Thanks

gameover

NoGo,

Can you pls explain the procedure you used to modify the VE table? I'm confused about the process, are you using the MAF airflow as the main measurement variable?

All of the logged data i have checked against VE table values at part throttle and WOT for stock engines gives g/cyl values very close to the MAF derived numbers. ie. within ~0.02 g/cyl.

Again my formula for calculating g/cyl from the VE table is:

g/cyl = VEvalue * MAP * 51.2 / ((T+273) * 32 * 8192)

if you are using LS1edit the VE table value needs to be multiplied by 5.12.

cheers...

VT2 EXEC LS1

NoGo - I guess your findings reiterate a point made by Plan B in the other MAFless thread about tuning MAFless. The only way the correct VE values can be determined is by putting the car on a dyno, hooking up the wideband O2 sensor, logging every load site and deriving the VE values from the AFR readings.

From the looks of it no VE calculator is going to work for MAFless tuning. I guess this reflects why no mail-order mafless PCM tuning is offered here in Oz.

Plan B

Well yeah…. To tune and engine, you should first measure it and adjust it.

Let’s simplify it a little more…. How do you tune a musical instrument such as a guitar? You firstly measure it and then you adjust it. It’s the same thing really.

gameover

Isn't that the way it always been for SD tuning? Unless you have some whizbang engine simulator software there is no other way to calculate the actual VE of an engine. What you're doing is disable all kinds of learning and enrichment/enleanment so you know at all times the PCM is trying to set a stoich AFR then measure your AFR at various load/RPM points then adjust your VE table - ie. telling the PCM more or less air is entering the cylinder to match the actual amount that is going in - so the PCM then adjusts the fuel accordingly to get your 14.7 AFR you read on the WB02. If you get 14.7 then you have things about right.

The PCM simply needs to know how many grams of air is entering the cylinder (either from MAF or SD) then it takes 14.7 and works out the grams of fuel it needs to inject. If you get the air right the fuel will follow.

Maybe PlanB can comment on his experiences on how close the stock VE table is to reality for a stock engine running MAFless?

This thread was about the units of the VE table, hence my question to Nogo as to what the test he did was actually trying to show...

Plan B

On a stock car? Ok.... No problem.... Think about this for a minute. (I'll keep it simple)

When you change your ignition timing, you will alter the AFR. Now what?

Bink

gameover - I can't speak for NoGo...but I do know what the purpose of the test was. After you provided the EXCELLENT info on the units of the VE table a couple of things seem to be explained- including the origin of the "30" in NoGo's Original Equation.The thread then morphed into a search for the most correct/accurate VE equation. Many of us here have used this equation to set up our PCMs. If the Original equation was wrong then we needed to find the correct one-that simple.
Without your input and help we would not have been able to pursue this. I, personally, have a much better understanding of past fueling problems. And I now "see" how you can use your equation without an RPM value ( Duh - Hey deezel! - I finally get it!!).Thank you, gameover, we're all very glad you're here.
I have a question - if you log with a Wideband O2 and Output RPM, MAP and AFR why couldn't you use these to calculate your MAFLESS table?? Then you wouldn't need a load dyno.
joel

NoGo

iTrader: (2)

You can log with a wideband and determine your VE table to run MAFless, but you are going to have to start with the MAF off.

Bink

Not me ......I'm keeping my MAF!!!
joel

gameover

i thought you might say... "If you disconnect the MAF on a stocky and check the AFR's they are not even close to 14.7..." Is that a true statement in general?

Bink

I was just the mule. And, I provided perceptive driver feedback ( Nogo, the car ran Great or NoGo the car ran like ****). NoGo - He is The MAN - did the bulk of the work (all of the astute analysis ).

FWIW.
I don't know if most realize it but Nogo is not your average tuner.The man tunes gazillion HP Turbines for a Living. It seems that his life IS Power Generation. A very humble man . As I said, FWIW.

jimmyblue

iTrader: (11)

Looking at this discussion I see where folks are
trying to to get RPM into the g/cyl number, but it
doesn't belong because g/cyl is a per-intake-stroke
value?

(X)g/cyl * (4)cyl/revolution * (RPM)revolution/minute * minute/60sec
= (X)(4/60)(RPM) g/sec.

I think that's right?

There's a method that one of my old (probably dead
by now) physics teachers used to drum into us,
which he called "dimensional analysis". This being,
every quantity and every conversion you apply,
you write down the physics units carefully in the
numerator and denominator along with the numbers.
Then, just like in algebra where you'd strike out any
x/x and y/y you find, to simplify your work, you do
the same with sec/sec and gm/gm and cm/cm and
what's left is (or should be) the final units of your
result along with the quantity. At the time it all
seemed like arbitrary tedious ****, but I've found it the
only way to keep straight and have any confidence in
my calculations (which can get pretty wooly in the
semiconductor device physics that I still have to
trudge through every so often). If anybody's still with
me here, I'm just offering it as a suggestion to help you
determine whether various conversions / equations make
physical sense - the units tell, if they are kept up
along the way. But usually people just and
when I go on this way so for the most part I don't.

NoGo

iTrader: (2)

We have been using the MAF reading to back-calculate to the VE value.

Basically record:
Airflow
RPM
MAP
IAT

And crunch the numbers. To get to your eq you can go through all the trouble of re-calculating the numbers or you can just adjust your table results by 1.175....... the results are the same.

As I stated above, your formula seems to work better when going directly MAFless. Proof to your statement that the formula is directly from the PCM. However, with the MAF connected, no matter how I crunch it your values make the car go sick lean.

Example:
Recorded a/f at WOT: 250 g/sec (pretty typical)

Resulting VE using NoGo = 2366
Resulting VE using Gameover = 10285.82 ---> 2008 Edit Units

Or roughly a VE table reduction of 1.17. We plugged in your values, and the car goes lean (with the MAF plugged in). If I put your VE values into any car (with MAF plugged in) it goes lean. :shrug:

NoGo

iTrader: (2)

Jimmy,

Canceling units is a great way to check math. Unfortunately, we have some numbers but don't exactly know the units..........

Plan B

At wide open throttle. Most are a little rich. At varying load points, they are all over the place. Some 03/04 cars can even get a little lean in places at varying load points and throttle positions. Every car is different…. Way different. Every bolt on will effect the VE’s and some of the larger cams like Binks can turn them into a cityscape.

If you can’t measure and adjust the VE’s correctly, leave the MAF in place as it does a pretty good job of putting a veil over the whole area. The trouble is, the veil can only smooth things to a point.

Think of it this way; If you were going up the road to buy everyone lunch, it’s always a good idea to ask the individuals what they’d like to eat first.

SS346

LOL! sorry guys, but i had a little chuckle about the equasion thing. Simple you dont need any formulas whatsoever to make the correct ve changes, all you need is a wideband,dyno and a scanning tool, 20/20 vision also helps you just cant 'punch in' a few numbers and think it will work, you gotta give the engine what its asking for, the best example is the one Plan b gave about the lunch thingy!

Bink

Yep, some of us are pretty silly.....we like to understand how things work.

joel

gameover

That's right, like spark you just increase it until you hear pinging, fuel you add more until it's right, shift firmness until you like the shift... but then it would be a funny conversation about how many whatsits of timing you put in at certain thingamajig of airflow to achieve the optimum sherwing of go fast stuff now wouldn't it??