Explanation of VE tables in HP Tuners??
10-04-2005, 08:28 PM
#1
Explanation of VE tables in HP Tuners?? I am going thru several .bin files from the depository and I noticed the VE tables on the stock cars was higher than the majority of the bigger motor cars. Why is this? Help me understand the percentages..
10-04-2005, 09:33 PM
#2
Were all the ones you looked at tuned in speed density? It's possible that a stock displacement h/c car would have better ve than a superstroker because of headflow limitations, but for a stock h/c car to have higher ve isn't realistic. The percentage basically means "at this rpm and manifold pressure, the volume of air that goes into each cylinder is ___ % of the cylinder volume".
On a side note, I think hptuners is different from ls1edit in this respect because ls1edit's ve numbers incorporate cylinder volume, while hptuners has a seperate entry for cylinder volume.
On a side note, I think hptuners is different from ls1edit in this respect because ls1edit's ve numbers incorporate cylinder volume, while hptuners has a seperate entry for cylinder volume.
10-04-2005, 10:09 PM
#3
TECH Senior Member
stock or smaller cam -- more efficient at lower RPMs , but as you get higher they become much less efficient, big cam , due to overlap you get **** poor performance at lower RPMs (which is why an M6 car will become sluggish after putting a big cam in... nothing gears don't fix) but they're VERY efficient at higher RPMs... generally bigger motors don't make a ton of power all over, they make it where you need it (on a big cam A4 car, you get a converter to put you in the right RPM range)
Regarding the volume... HPT uses the theoretical limit of a cylinder based on the Cylinder size (bore/stroke) whereas LS1 Edit displays these same values as gram/second I believe... same data just a different way of representing it
Regarding the volume... HPT uses the theoretical limit of a cylinder based on the Cylinder size (bore/stroke) whereas LS1 Edit displays these same values as gram/second I believe... same data just a different way of representing it
10-04-2005, 10:27 PM
#5
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I would say that the difference lies with the heads,
intake runners and exhaust, which will all be less
taxed by a small displacement engine than a large.
VE is what's left after taxes.
intake runners and exhaust, which will all be less
taxed by a small displacement engine than a large.
VE is what's left after taxes.
10-04-2005, 11:04 PM
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the ve's are a given amount of air/fuel at a certain freq right? what i was confused about is why do the numbers get lower with cammed cars and are higher on stock ones? could someone explain?
10-04-2005, 11:54 PM
#7
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VE is the fudge factor between actual air pumped
and the ideal yolume pumping. Down low valves
both being open lets air bleed across, reversion
or just the drawing in of both exhaust and fresh.
Overlap reduces the air taken in and pushed through.
and the ideal yolume pumping. Down low valves
both being open lets air bleed across, reversion
or just the drawing in of both exhaust and fresh.
Overlap reduces the air taken in and pushed through.
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10-05-2005, 08:10 AM
#8
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No, it's a 2-D "topographic map" of the airflow
with the axes being MAP and RPM, and the
VE is used like MassFlow=VE(MAP,RPM)*MAP*RPM
(modified by various other compensations but you
get the picture). This is how you get a mass of air
value, without using a MAF.
with the axes being MAP and RPM, and the
VE is used like MassFlow=VE(MAP,RPM)*MAP*RPM
(modified by various other compensations but you
get the picture). This is how you get a mass of air
value, without using a MAF.
10-05-2005, 02:12 PM
#11
Originally Posted by foff667
were the VE's on the FI cars you were looking at even tuned? Alot of people still dont even touch the VE tables.
10-05-2005, 03:29 PM
#12
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A couple of thoughts (although I probably have no idea what I am talking about): The VE table is really a table indicating the mass of air (thus the mass of fuel can be determined). I believe the optimal (or maximum) mass is calcluated using standard SAE values (20* C @ sea level with dry air). We can view this table in either mass or %'s (at least in EFILive). I assume the maximum amount is also assuming infinite time to fill the cylinder. So, the maximum amount is "fixed" per engine cycle. Thus, for every cycle, how much air (in terms of mass) would a 5.7L engine displace. If you have EFILive, change all the values (when viewing in the table as %) to 100%. Then, change the properties so that you can see the value in G*Kelvin/kPa. I see 2.4684. I assume this is how much air (at standard conditions) a 5.7L engine would displace every cycle.
On a stock 2001 vette (6sp), I see values as high as 99% efficient. I don't think that a stock vette is 99% efficient at 5600 RPMs and 100kPa. However, I do believe that GM wants the VE table to be "safe"; therefore, it is much richer than people would believe. The VE table is the failsafe. Under normal conditions (a stock tune), I see GM wants to command AFR's as rich as 11.8:1 under WOT. Therefore, I imagine if the MAF fails, GM has the VE table setup to be fairly rich for safety. So, it doesn't surprise me that some modified VE tables (on modifed cars) are less than stock values.
I have also seen people with really high VE values because they were simply failing to realize their injectors weren't big enough. The WB keeps reading lean, and they just keep adding #'s to increase VE to add more fuel. However, the duty cycle might already be 95%+, so the injectors probably can never supply enough fuel to achieve the commanded AFR.
On a stock 2001 vette (6sp), I see values as high as 99% efficient. I don't think that a stock vette is 99% efficient at 5600 RPMs and 100kPa. However, I do believe that GM wants the VE table to be "safe"; therefore, it is much richer than people would believe. The VE table is the failsafe. Under normal conditions (a stock tune), I see GM wants to command AFR's as rich as 11.8:1 under WOT. Therefore, I imagine if the MAF fails, GM has the VE table setup to be fairly rich for safety. So, it doesn't surprise me that some modified VE tables (on modifed cars) are less than stock values.
I have also seen people with really high VE values because they were simply failing to realize their injectors weren't big enough. The WB keeps reading lean, and they just keep adding #'s to increase VE to add more fuel. However, the duty cycle might already be 95%+, so the injectors probably can never supply enough fuel to achieve the commanded AFR.
10-05-2005, 03:52 PM
#13
The percentage basically means "at this rpm and manifold pressure, the volume of air that goes into each cylinder is ___ % of the cylinder volume".
