YellowZ06

Even thou I have an engineering degree and have taken calculus 1,2 & 3 I'm still puzzzled I'm sure it's something so simple I am overlooking. Trust me if I haven't tried somthing like 100 times first my self, I would not ask a question.

EVIL

i slept thru calculus and never learned a thing, then the college money ran out and then came the military......

ChrisB

It's a function of the conversion factors and R - see below for derivation - the things you have to watch for are what units you express "R" in (and I apologize - don't know why I kept calling it rydberg's constant, that's something different - it's the gas constant or universal gas constant).

You also need to watch out for how you are expressing flow - is it for each cylinder, for the entire engine, etc

YellowZ06

ChrisB Thanks, That's what I was looking for

HumpinSS

iTrader: (1)

I will calculate a pid tonight and see how this works with EFILIVE v6. I fell aspleep during ALL math classes myself. So based on what we have learned in this thread a feasible method for tunning for positive LTFT's are.............?

gojo

iTrader: (12)

We don't adjust IFRs by kpa since doing that affects AFR settings.
What effect will setting VE by kpa have on AFR?Besides ltrims what else will be affected by changing VE?

Bink

VE table is used in all fueling. Open and closed loop. So it will effect Idle, Part Throttle, Power Enrichment and WOT.
joel

RPM WS6

iTrader: (3)

I understand about MAYBE 10% of the info in this thread. It is waaaay above my head, so I have one simple question: For those of us that have our setups working pretty darn well with low rpm VE changes and minor IFR adjustments, is it really worth re-configuring everything and going through all these calculations? Are the driveablity and/or power gains really worth it? Or is this just more for people trying to remove MAFs from there setups?

I'm really not getting why all this is necessary? What fault are you all trying to correct in your cars?

I have made percentage changes to my VE table in the 400/800/1200 rpm columns, I have multiplied my whole IFR table by 95%, and these two changes have brought my adverage Ltrims at cruise very close to 0 and my cold, warm, and hot starts are basically as good as it gets. Am I missing something?

EVIL

when you sit and free rev your motor from cell to cell across the map, do you notice a smooth cell to cell transition or does it stumble slightly as you move from say map 40 at 800 rpms to map 30 at 1200?? i have noticed on most all cammed cars that it is not a smooth transition, thats where the ve comes in. dont really know how to explain it any easier. if you are looking to get your modded car back as close to an OEM tune, you must take full advantage of every tool avalible.

gojo

iTrader: (12)

Binks, thanks for the confirmation. I figured that with my mods, my car is closer to a Z06 than a C5. Rather than try to get the VE table right, I took a shot and put the Z06 VE table in. It did require changing all the previous settings in the functions you mention. My Ltrims are easier to get close to 0 and they are closer from cell to cell and side to side, my AFR curve has smaller spikes and my idle(750), cruise, etc are great. Don't ask me why. The engine doesn't miss a beat and I guess the tuning is better since I picked up 1 1/2 mph in the 1/8th. I added a new style Bauer TB last week and it ran right with some change in AFR. It all got too easy when I put the Z06 VEs in. So, it seems if you can find the right VE values your way ahead. Does this all make sense?

Bink

* No, you are not missing anything. If you haven't made radical changes to your setup then tweaking your VE should be fine. If you were to change to highly ported heads, higher flowing intake manifold (FAST?),BIG Cam, Headers, Catless and Stroked or DeStroked ( all of these combined) - I think rescaling your VE table via NoGo's REAL world technique might be a good idea. Just my .02.

Bink

Very Cool. Great idea . Makes all the sense in the world to me ...and you proved it works for you. Good Luck.
joel

NoGo

iTrader: (2)

Binks beat me to it.

Using the IFR table to do your LTerms, and alot of the 'older' methods to tune our cars will still work fine for most setups.

When you start going hog-wild, as binks mentioned above, it becomes increasingly difficult to re-obtain the kind of street manners that an EFI car should have. Being able to implement an accurate VE table is a big step in producing a street friendly MONSTER LS1/LS6.

However, even mild setups should see better street manners with an accurate VE table.

Good Luck

66ImpalaLT1

Very cool guys. I'm looking forward to tuning my car with VE. Even with a small cam like mine (T1), I think it will benefit at low rpm's because of its LSA.

Eric

Bink

Eric- What's the LSA on your T1. Better yet, what are the specs? TIA.
joel

RPM WS6

iTrader: (3)

NoGo and Binks,

Thanks for the clarification on the purpose of this tuning meathod. Your explaination is exactly what I thought this was all for; very aggresive setups that run like crap for street driving.

I think this is well beyond what my little cammed car needs.

RPM WS6

iTrader: (3)

T1 is very close to my B1 cam.

T1 = 221/221//.558/.558//112 lsa
B1 = 221/221//.558/.558//114 lsa

ChrisB

Re VE vs. IFR - As has been pointed out it's not neccecarily a one or the other situation. The VE table allows for more fine grained tuning since it is scaled vs. RPM and MAP as opposed to only MAP (or a map analogue) like the IFR table - this allows you to "tune" for more specific instances (e.g. situations where your MAP is the same, but your actual engine fueling needs are different).

The main feature of the VE table you are interested in is it's shape - as this reflects the relative effeciency of your engine in different areas. You should do a sanity check on your calculated values also - generally your maximum VE should be from 90-100% (edit value divided by 30, per NoGo's determination). The general shape of the curve will be similar to stock, though the high's and lows may be exxagerated, with narrower or wider peaks depending on your setup.

I would echo NoGo's sentiment of not tuning your VE table vs. L-trim values - the problem with them is that as you deviate greater from stock there are many factors *other* than errors in the computer model that can cause them to deviate - and in the end they don't directly effect your performance as long as they fall within certain bounds. That doesn't mean it will hurt to try though - by all means, if you have the time go for it - and post up on how it worked out. I would just suggest that using the calculation method will probably yield better results.

Richard@WCCH

iTrader: (3)

So to summerize, the VE table dictates the primary fueling functions via trim cells upon which the maf, O2 sensors and other related sensors use to trim short term and long term fueling strategies in open and closed loop conditions? Could this explain occasional double digit positive STFTs while maintaining single digit negative LTFTs across the same load cell?
I imagine my base fuel value then gets "trimmed" positive or negative according to sensor input.

I can feel the difference in 5% changes in low rpm and MAP cells (car starts easier both hot and cold and surges less when stabbing the brakes), yet LTFTs didn't seem to change.

I haven't experienced stumbling between cells when free revving across the rpm band, but I agree with the assumption that VE could makeup for "holes" when switching between cells in cars with larger displacement and/or cams.

Brilliant job here guys. Thank you, thank you, thank you for sharing.

Richard

EVIL

when i say stumbling, i just mean there is a distinct difference in the engine sound going from cell to cell due to over or under fueling.