noob needs help with ve tables

[kierancameron]

right folks i've read a few threads and i'm getting confused.

i have a 99 camaro ls1 engine and pcm trasnplant. i have turned off vats and a few other non required items and am now trying to tune the engine.

as it is a 99 camaro it was suggested i copy the 04 holden clubsport ls1 ve table as it was a more powerful tune due to better fuel etc. having compared the two the holden map looks more aggressive and a better starting point for my requirements.

when working with the main ve table however parts of the full load high rpm map are over 100. my understanding of this table is the 100 represents atmospheric pressure and therefore anything above a bar ( or 100 on the table ) is positive pressure or boost.

am i right or am i being dumb.

p.s. i'm used to tuning turbo'd jap 4 pots, this v8 lark is all new

[kierancameron]

bump up

[WeathermanShawn]

Kieran:

Are you boosted, or N/A?

Not sure where you are going with your question. Normally the VE Tables along with the MAF Tables are representing the Airflow Values in an engine.

Perhaps tells us your exact engine specifications along with any engine modifications. Are you MAF-Enabled? Closed-Loop or Open?

[kierancameron]

Kieran:

Are you boosted, or N/A?

Not sure where you are going with your question. Normally the VE Tables along with the MAF Tables are representing the Airflow Values in an engine.

Perhaps tells us your exact engine specifications along with any engine modifications. Are you MAF-Enabled? Closed-Loop or Open?
essentially it's a stock ls1 with stock tune. still na. i just can;t understand why parts of the ve table are greater than 100?

[joecar]

Post some .tun and .log files.

[kierancameron]

the main ve table from this tune

http://www.holdencrazy.com/EFILive/TuneFileRepository/Stock/HSV/2004%20HSV%20Clubsport%20Sedan%20Manual%20LS1%205. 7%20Litre%20(12225074).tun

[WeathermanShawn]

I'm still not clear exactly what you are asking..but for a vehicle at sea-level, atmospheric pressure is ~101.2 kPa. With a strong high pressure you could hit 105 kPa.

The VE Table you are describing would be normal for a N/A vehicle..:).

[kierancameron]

thats kinda what i'm asking. is over 100kpa normal. and your saying it is so coolio :)

[joecar]

There is no explanation for that... a VE table that models the physical hardware does not look like that.

You can get VE slightly greater than 100% near peak torque in some cases... if you tune and match the intake, heads/cam, headers.

[WeathermanShawn]

I was not sure if the OP was talking about the MAP Axis of 100-105 kPa being 'normal' or the actual VE Table values.:confused:.

I agree, the actual VE Table values look suspect.

Perhaps the OP can elaborate a little more..

[kierancameron]

the file i have linked above is a stock map for a ls1 engined hsv clubsport from 2004. if you look at the upper ranges of the ve table, high load high rpm area's the values are 103-105. now my understanding of how efilive works and the tuning of these vehicles means that you are basically seeing positive pressure ( or in other words boost ) on an na engine. it doesn't make sense to me thats all.

[WeathermanShawn]

the file i have linked above is a stock map for a ls1 engined hsv clubsport from 2004. if you look at the upper ranges of the ve table, high load high rpm area's the values are 103-105. now my understanding of how efilive works and the tuning of these vehicles means that you are basically seeing positive pressure ( or in other words boost ) on an na engine. it doesn't make sense to me thats all.

I am not really sure where you getting that VE Values over 100% are positive pressure or boost (do you have a reference or link?). If you take Joecar's CALC.VE Formula..

..VE[g*K/kPa] and VE[%] using pids (assuming engine 5.669L V8): VE[g*K/kPa] = {SAE.MAF.gps}*({GM.DYNAIRTMP_DMA.C}+273.15)*15/({SAE.RPM}*{SAE.MAP.kPa}) VE[%] = {SAE.MAF.gps}*({GM.DYNAIRTMP_DMA.C}+273.15)*3445.2/({SAE.RPM}*{SAE.MAP.kPa}*5.669)..the VE Values are simply Airflow values. To get a VE Value of ~105% at 5200 Rpm's & 100 MAP, DAT=10C, you would need a MAF flow of 330 g/s.

For instance, my H/C 2002 Camaro gets close to that Value in the upper regions. However, my VE Table approximates what a dyno curve of it looks like. It peaks ~4800-5200 Rpms then falls off.

In reality at that point with the Tune you posted, you are all MAF anyway. So unless you are Tuning SD, why worry about it.

The bottom line is that VE Values over 100% have nothing to do with positive pressure or boost. You need a lot of work done on a vehicle to hit it..

[joecar]

the file i have linked above is a stock map for a ls1 engined hsv clubsport from 2004. if you look at the upper ranges of the ve table, high load high rpm area's the values are 103-105. now my understanding of how efilive works and the tuning of these vehicles means that you are basically seeing positive pressure ( or in other words boost ) on an na engine. it doesn't make sense to me thats all.As Shawn said, that does not imply positive pressure... it simply means the PCM calculates cylinder airmass greater than what the cylinder can actually hold;

GM may or may not necessarily correctly model the cylinder airmass.

I don't like viewing VE in % units, I instead prefer g*K/kPa.

:)

As Shawn said, a correctly modeled VE table looks like the TQ curve from a dyno pull.

[dian]

thats what i would expect as well. ve should be more or less proportional to map and follow the torque curve. but if i look at the stock calibration of my 2000 c5 corvette, its quite different: ve is 91% @ 50 kpa and 99% @ 100 kpa. shouldnt it have doubled? at 100 kpa it rises to 99% @ 5200 rpm (far beyond peak torque) and stays at that value at higher rmp, while cylinder filling decreases for sure.

i guess this is what op was saying. so what am i missing here? is that a trick to enrichen the mixture? but commanded lambda doesnt support this, it doesnt change much at highrer loads and rpm.

edit: i was just able to look at 2002 os 12212156 and interestingly there ve peaks at 4400 rpm (105%) and falls to 88% at 6400 for 100 kpa. where does the difference come from?

[joecar]

thats what i would expect as well. ve should be more or less proportional to map and follow the torque curve. but if i look at the stock calibration of my 2000 c5 corvette, its quite different: ve is 91% @ 50 kpa and 99% @ 100 kpa. shouldnt it have doubled? at 100 kpa it rises to 99% @ 5200 rpm (far beyond peak torque) and stays at that value at higher rmp, while cylinder filling decreases for sure.

...

TQ is proportional to VE.

But VE is not proportional to MAP...

to start with, flowrate (air flowing past open valve into cylinder) is proportional to the squareroot of pressure...
and then there are various complications (restrictions to flow, venturi effect where port narrows, ...) all of which make the MAP-to-VE relationship complex (not linear, but polynomial of decaying exponential terms)...

look at any VE table, compare 50% to 100%, you will see there is no simple evident relationship;

( BTW: I like to look at VE in g*K/kPa units, this form of VE is simply cylinder fill airmass normalized for temperature and pressure; the V7 tunetool has an option setting for viewing VE in g*K/kPa units ).




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is that a trick to enrichen the mixture? but commanded lambda doesnt support this, it doesnt change much at highrer loads and rpm.
...
I don't understand your question...

Commanded lambda (I prefer EQR (Equivalence Ratio), EQR = 1/Lambda) is settable in the PE table... if your VE and/or MAF tables are both correct, then you can measure the same lambda in the exhaust gas as the commanded lambda.

Note that when PE enables, you typically will not be trimming to stoichiometric any more, and if the PE table is richer than stoich (and it should) then it will determine fueling (i.e. PE table will then determine commanded lambda or commanded EQR)

( BTW: I like to use EQR for commanded fueling, and Lambda for wideband measured exhaust gas, this way I can avoid confusion in conversation by narrowing down the 4 combinations down to 2 )




...
edit: i was just able to look at 2002 os 12212156 and interestingly there ve peaks at 4400 rpm (105%) and falls to 88% at 6400 for 100 kpa. where does the difference come from?
The VE peak depends on the installed advance of the cam (advancing the cam moves the peak lower, retarding the cam moves the peak higher).

As engine spins faster, there is less time to ingest a given amount of air, so retarding the cam (or increasing the duration) opens the window wider to allow more time.