So is VE table used in normal driving or not??
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From: Schiller Park, ILL Member: #317
Re: So is VE table used in normal driving or not?? Judging by the improvements to my car's normal driving characteristics after VE table changes, I would say yes it is used in normal driving...
Re: So is VE table used in normal driving or not?? The VE table is used during normal driving. It is used during ALL running conditions of the car.
This has been solidly proven, and should not be up to debate anymore.
This has been solidly proven, and should not be up to debate anymore.
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From: Las Cruces, NM
Re: So is VE table used in normal driving or not?? It should not be a debate but using the calculations provided on this board my calculated VE were 35% larger than stock so now my tables go from ~52% upto 105% (twin turbo car). I put these numbers in and can not tell any difference in idle quality, afr (in-car wideband),etc. I have not done enough testing to confirm that, but with that huge of a change in the VE some other parameter should have had noticable differences.
Gary
Gary
Re: So is VE table used in normal driving or not?? FWIW. You should not make changes to your VE table with the turbo's hooked up. You are going to have some very odd readings. The reason being is that the MAP sensor tops out at 1 bar. Your turbo's though are going to push the intake pressure much greater than 1 bar. As a result, the MAP of the VE value will be fixed while the MAF value increases. This will give you erroneously high VE readings for your table. Probably why you are seeing 35% larger values.
A forced induction engine from the manifold in still moves relatively the same VOLUME of air even with the forced induction hooked up. Just the density of the ingested charge changes.
With that being said, if you want to obtain a more accurate VE table you need to disconnect your turbos (basically impossible) and then calculate it out.
Mapping the VE table of a forced induction car only works if you have a MAP sensor sensor that will give you an accurate reading of the absolute pressure of the manifold.
I would go back to the stock VE table if I were you.
Good Luck
A forced induction engine from the manifold in still moves relatively the same VOLUME of air even with the forced induction hooked up. Just the density of the ingested charge changes.
With that being said, if you want to obtain a more accurate VE table you need to disconnect your turbos (basically impossible) and then calculate it out.
Mapping the VE table of a forced induction car only works if you have a MAP sensor sensor that will give you an accurate reading of the absolute pressure of the manifold.
I would go back to the stock VE table if I were you.
Good Luck
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Re: So is VE table used in normal driving or not??
I did a search and found that there are mixed opinions on the subject. Does the PCM use the VE table under normal conditions or only in speed density?
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Re: So is VE table used in normal driving or not??
I did a search and found that there are mixed opinions on the subject. Does the PCM use the VE table under normal conditions or only in speed density?
I hate Internet Myth BS.FWIW.
joel
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From: Las Cruces, NM
Re: So is VE table used in normal driving or not?? The 35% was consistent even at idle, i.e no boost. Plus at this point I am only running 5 psi of boost and I am at 4500 ft (12.3 psi). So thats essentially only 3 psi above sea level, i.e. not much difference. If the VE table are used and accurate then all my logged numbers should be good until 105 kpa were the VE table stops. Up to this point there is no difference than a NA setup. The computer can and does compensate for density shifts, even with the maf out, so thats not a very good explanation. I am not bashing and I know everyone is still learning.
Gary
Gary
Re: So is VE table used in normal driving or not?? Yes, your VE table calculation will be accurate up until the point that you build boost. However, as I stated above, as soon as you exceed 14.7 psi, your calculations are no longer correct.
Whether or not the computer compensates for density shifts still doesn't change the fact that your engine will always move a consistant volume of air despite the density change. This is a simple fact of engine dynamics, it is not up for debate.
My reason for bringing up this point was to illustrate that forced induction cars can still determine an accurate VE table, they just have to disconnect their 'forced induction' (or ignore it, as you have done) when doing their VE calcs.
Getting back to your numbers though..... they still look very suspect. Just to give you a ballpark example of what your numbers represent: A full-tilt race motor will develop around a 102% VE at peak power. I have NEVER seen an LS1 or LS deriviative motor over 92%.
THIS IS WRONG. REFER TO SYSTEM VE CALC BELOW
It may be worth your while to go back over your numbers.
Good Luck
Whether or not the computer compensates for density shifts still doesn't change the fact that your engine will always move a consistant volume of air despite the density change. This is a simple fact of engine dynamics, it is not up for debate.
My reason for bringing up this point was to illustrate that forced induction cars can still determine an accurate VE table, they just have to disconnect their 'forced induction' (or ignore it, as you have done) when doing their VE calcs.
Getting back to your numbers though..... they still look very suspect. Just to give you a ballpark example of what your numbers represent: A full-tilt race motor will develop around a 102% VE at peak power. I have NEVER seen an LS1 or LS deriviative motor over 92%.
THIS IS WRONG. REFER TO SYSTEM VE CALC BELOW
It may be worth your while to go back over your numbers.
Good Luck
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From: College Station, Tx
Re: So is VE table used in normal driving or not?? Gary - I was definitely a doubter - and I still don't understand the reason the VE tables are used in maf mode, but I they definitely are. Cal took the time out to log a before and after dataset for me with a large VE change (200% scaling). Just looking at the data there *was* a definite change in injector pulswidth for the effected data cells (I think I posted some results in the above linked thread). Was it a 200% change? Definitely not, but it was a definite different value - actually about 10 standard deviation units different - so a real positive change.
While it will never hurt to double check your numbers, I can believe the higher values due to the twin turbo's - the will increase your VE even if you aren't in boost, as the engine will still be injesting more air than it would otherwise (up to a point). You should watch out with your highest map value though - I would probably put an upper bound at 100 kPa, since any value higher than that will not be discriminated from another - they are all lumped together.
If you would post some of your log files I would be happy to take a look at them.
While it will never hurt to double check your numbers, I can believe the higher values due to the twin turbo's - the will increase your VE even if you aren't in boost, as the engine will still be injesting more air than it would otherwise (up to a point). You should watch out with your highest map value though - I would probably put an upper bound at 100 kPa, since any value higher than that will not be discriminated from another - they are all lumped together.
If you would post some of your log files I would be happy to take a look at them.
Re: So is VE table used in normal driving or not?? Red WS6 99:
I retract my statement about your numbers being suspect. I was a little confused by your high numbers and decided to whip out the book last night.
Your VE numbers should correspond to a twin pump system (your engine as one, and your turbo's as one) being we are measuring massflow our numbers are going to represent the volumetric efficiency of the entire system, not just the single system.
This is represented as
VE Pump 1 / VE Pump 2
Centrifugal / Positive Disp Pist
Centrifugal VE = 100% (there is no 'real' VE of a centrifugal pump being it is not a positive displacement. This theoretical value is used in VE system calcs)
Your Engine = ~75% (the added exhaust restriction of the turbos drops the independant VE of the engine slightly ~5%)
System VE = 100 / 75
System VE = 1.33 or 133%
With that being said most of your numbers should be about 33% higher than a typical single pump system and your peak VE numbers should be right at 100%.
Soooo, your numbers look pretty spot on from the reading I did.
Sorry about the confusion....
Good Luck
I retract my statement about your numbers being suspect. I was a little confused by your high numbers and decided to whip out the book last night.
Your VE numbers should correspond to a twin pump system (your engine as one, and your turbo's as one) being we are measuring massflow our numbers are going to represent the volumetric efficiency of the entire system, not just the single system.
This is represented as
VE Pump 1 / VE Pump 2
Centrifugal / Positive Disp Pist
Centrifugal VE = 100% (there is no 'real' VE of a centrifugal pump being it is not a positive displacement. This theoretical value is used in VE system calcs)
Your Engine = ~75% (the added exhaust restriction of the turbos drops the independant VE of the engine slightly ~5%)
System VE = 100 / 75
System VE = 1.33 or 133%
With that being said most of your numbers should be about 33% higher than a typical single pump system and your peak VE numbers should be right at 100%.
Soooo, your numbers look pretty spot on from the reading I did.
Sorry about the confusion....
Good Luck
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From: Las Cruces, NM
Re: So is VE table used in normal driving or not?? I don't know if I belief my numbers at idle really. The boosted number seem reasonable. Reason is my idle air rate is pretty low like 6 g/s, map is 30 kpa, and idle is 750 rpm. As far as I know, I am the only Incon kit that has idle problems, but then again I am up at 4000-8000 ft.
I have rough idle. I was hoping to see some changes with VE. I will be changing my pcv system (from the Incon setup) which will get rid of the most of the low idle air problem this week.
Gary
I have rough idle. I was hoping to see some changes with VE. I will be changing my pcv system (from the Incon setup) which will get rid of the most of the low idle air problem this week.
Gary
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From: St Louis, MO
Re: So is VE table used in normal driving or not?? red ws6 99: I live at 7000ft elevation, ambient pressure is normally about 80kpa. My idle air rate is 7g/s, map is 40kpa and idle is 800rpm.
I have a 112lsa cam which probably explains why I use 1g/s more air and my map is 10kpa higher at idle.
Just thought you'd like some high altitude numbers to compare with.
Eric
I have a 112lsa cam which probably explains why I use 1g/s more air and my map is 10kpa higher at idle.
Just thought you'd like some high altitude numbers to compare with.
Eric
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From: Las Cruces, NM
Re: So is VE table used in normal driving or not?? Thanks, its hard to get any comparison data. I have the only Incon kit in New Mexico and there are very few turbo cars here or forced induction (ls1). Everybody I know has GNs so that does not help too much. After I calculated the density differences between sea level and here the idle air amounts seemed about right. I just don't think the pcm really compensates for altitude as good as it should. My car even before turbos did not have a very smooth idle. Of course I have come to find out that is partially because the WS6 has more aggressive idle curves, etc when compared to a regular camaro or firebird.
Gary
Gary
Re: So is VE table used in normal driving or not??
My car even before turbos did not have a very smooth idle. Of course I have come to find out that is partially because the WS6 has more aggressive idle curves, etc when compared to a regular camaro or firebird.
Gary
Gary
I really doubt that; if you had a rough idle before there is a problem with your car. Not even a Z06 has a rough idle from the factory.
