VE table shape
Thread Starter
Teching In
Joined: Oct 2005
Posts: 33
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VE table shape Can someone explain the overall shape of the VE table? Why does it peak at around 5300 rpm then fall back? I have only tuned this table up to about 4000 rpm, the rest is stock. I understand that as the MAP increases, the motor will become more efficient thus the higher %.
I just want to get some discussion going on the reasoning behind some of the trends in the plot.
Jeremy
I just want to get some discussion going on the reasoning behind some of the trends in the plot.
Jeremy
Top end fade is the flow restriction posed by all of the stacked
up resistances - intake and head runners, the inerta of the air
column vs the cam-open chop time, the spent gas residual
pressure in the cylinder.
The over-100% peak in the middle can be resonant intake runner
effects building out the cylinder fill (or, just a cheat to make it
fit mixture-wise).
My opinion is that the motor is a fairly regular, continuous pump
at the heart of it all and the response surface should be smooth
and continuous. I don't like the look of that "pocket" at the lower
MAP, 2800RPM or so. Unless this has EGR or something to depress
the air, that looks like a lean divot.
Also the area above peak, where it drops a little and then plateaus
on out to 7200? Not too realistic, even though you probably don't
go there. More like "drop and keep on dropping", this is where the
big cam will carry you on out but a little cam will starve the motor
for air (open time).
I don't have a good idea of why MAP would increase VE (MAP already
being in the SD equation, RPM*MAP*VE(). Maybe it's about more MAP
overcoming the residual pressure, or MAP making the air column scoot
better at the beginning of intake cycle. Something has to fit up the
air column start/stop/resonant effects.
up resistances - intake and head runners, the inerta of the air
column vs the cam-open chop time, the spent gas residual
pressure in the cylinder.
The over-100% peak in the middle can be resonant intake runner
effects building out the cylinder fill (or, just a cheat to make it
fit mixture-wise).
My opinion is that the motor is a fairly regular, continuous pump
at the heart of it all and the response surface should be smooth
and continuous. I don't like the look of that "pocket" at the lower
MAP, 2800RPM or so. Unless this has EGR or something to depress
the air, that looks like a lean divot.
Also the area above peak, where it drops a little and then plateaus
on out to 7200? Not too realistic, even though you probably don't
go there. More like "drop and keep on dropping", this is where the
big cam will carry you on out but a little cam will starve the motor
for air (open time).
I don't have a good idea of why MAP would increase VE (MAP already
being in the SD equation, RPM*MAP*VE(). Maybe it's about more MAP
overcoming the residual pressure, or MAP making the air column scoot
better at the beginning of intake cycle. Something has to fit up the
air column start/stop/resonant effects.
Thread Starter
Teching In
Joined: Oct 2005
Posts: 33
Likes: 0
Originally Posted by jimmyblue
Top end fade is the flow restriction posed by all of the stacked
up resistances - intake and head runners, the inerta of the air
column vs the cam-open chop time, the spent gas residual
pressure in the cylinder.
The over-100% peak in the middle can be resonant intake runner
effects building out the cylinder fill (or, just a cheat to make it
fit mixture-wise).
My opinion is that the motor is a fairly regular, continuous pump
at the heart of it all and the response surface should be smooth
and continuous. I don't like the look of that "pocket" at the lower
MAP, 2800RPM or so. Unless this has EGR or something to depress
the air, that looks like a lean divot.
Also the area above peak, where it drops a little and then plateaus
on out to 7200? Not too realistic, even though you probably don't
go there. More like "drop and keep on dropping", this is where the
big cam will carry you on out but a little cam will starve the motor
for air (open time).
I don't have a good idea of why MAP would increase VE (MAP already
being in the SD equation, RPM*MAP*VE(). Maybe it's about more MAP
overcoming the residual pressure, or MAP making the air column scoot
better at the beginning of intake cycle. Something has to fit up the
air column start/stop/resonant effects.
up resistances - intake and head runners, the inerta of the air
column vs the cam-open chop time, the spent gas residual
pressure in the cylinder.
The over-100% peak in the middle can be resonant intake runner
effects building out the cylinder fill (or, just a cheat to make it
fit mixture-wise).
My opinion is that the motor is a fairly regular, continuous pump
at the heart of it all and the response surface should be smooth
and continuous. I don't like the look of that "pocket" at the lower
MAP, 2800RPM or so. Unless this has EGR or something to depress
the air, that looks like a lean divot.
Also the area above peak, where it drops a little and then plateaus
on out to 7200? Not too realistic, even though you probably don't
go there. More like "drop and keep on dropping", this is where the
big cam will carry you on out but a little cam will starve the motor
for air (open time).
I don't have a good idea of why MAP would increase VE (MAP already
being in the SD equation, RPM*MAP*VE(). Maybe it's about more MAP
overcoming the residual pressure, or MAP making the air column scoot
better at the beginning of intake cycle. Something has to fit up the
air column start/stop/resonant effects.
Thanks,
Jeremy
From what I understand, the shape and rpm range of the VE table mirrors the TORQUE curve from a chassis/engine dyno run. IE, if you make peak torque at 4900, the VE table should rise to 4900, then fall after that. I do not think that it mirrors the hp curve. If it did, you would see VE tables rising to 6000-6500, then falling off.
__________________
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
2013 Corvette Grand Sport A6 LME forged 416, Greg Good ported TFS 255 LS3 heads, 222/242 .629"/.604" 121LSA Pat G blower cam, ARH 1 7/8" headers, ESC Novi 1500 Supercharger w/8 rib direct drive conversion, 747rwhp/709rwtq on 93 octane, 801rwhp/735rwtq on race fuel, 10.1 @ 147.25mph 1/4 mile, 174.7mph Half Mile.
2016 Corvette Z51 M7 Magnuson Heartbeat 2300 supercharger, TSP LT headers, Pat G tuned, 667rwhp, 662rwtq, 191mph TX Mile.
2009.5 Pontiac G8 GT 6.0L, A6, AFR 230v2 heads. 506rwhp/442rwtq. 11.413 @ 121.29mph 1/4 mile, 168.7mph TX Mile
2000 Pewter Ram Air Trans Am M6 heads/cam 508 rwhp/445 rwtq SAE, 183.092 TX Mile
2022 Cadillac Escalade 6.2L A10 S&B CAI, Corsa catback.
2023 Corvette 3LT Z51 soon to be modified.
Custom LSX tuning in person or via email press here.
Originally Posted by Patrick G
From what I understand, the shape and rpm range of the VE table mirrors the TORQUE curve from a chassis/engine dyno run. IE, if you make peak torque at 4900, the VE table should rise to 4900, then fall after that. I do not think that it mirrors the hp curve. If it did, you would see VE tables rising to 6000-6500, then falling off.
Also, couldn't you take a dyno run and back-figure it to a VE table?? You should be able to!
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Here's my VE graph:
.JPG)
And the table that goes along with it:
.JPG)
My car is bolt-on only, tuned open loop speed density. If you need the mod list, just ask. Pretty much just full intake/exhaust.
And the table that goes along with it:
My car is bolt-on only, tuned open loop speed density. If you need the mod list, just ask. Pretty much just full intake/exhaust.
hey gary, what timing tables are you running? stock or zo6? ive turned off dfco so it shouldnt richen up. i think. i just threw the ls6 timing tables and put it back in SD, so im gonna see how that works out.
Originally Posted by Gary Z
I think ninobrn99's VE table can not accurate. At lower engine speeds, VE will be reduced due to heating of the incoming air.
Aren't you supposed to tune the VE table for all the same air temperature and then you use the Fuel-Air Multiplier to correct for incoming air temp situations?
Originally Posted by H8 LUZN
How are you suppsed to build a VE table if you dont have a MAF (i.e. no reference for airflow)????
In SD mode you only have MAP and RPM... no airflow...
In SD mode you only have MAP and RPM... no airflow...
I don't even use narrow band O2 sensors anymore...the bungs are plugged from now on on my car.
Originally Posted by 2002_Z28_Six_Speed
Aren't you supposed to tune the VE table for all the same air temperature and then you use the Fuel-Air Multiplier to correct for incoming air temp situations?
Basically, you just gotta tune it like you drive it.
I believe IAT is in there as a correction factor for density->mass
but the IAT is only going to be right, at steady state (and maybe
not -that- right, at low flows if heat is transferred after the IAT
location).
Regardless, it's pretty unlikely that VE would kick up at the high
RPM end of the table.
Here's a table I fitted for a TRex cam (over the email) by using
open loop NBO2 voltages....
but the IAT is only going to be right, at steady state (and maybe
not -that- right, at low flows if heat is transferred after the IAT
location).
Regardless, it's pretty unlikely that VE would kick up at the high
RPM end of the table.
Here's a table I fitted for a TRex cam (over the email) by using
open loop NBO2 voltages....
Originally Posted by MeentSS02
Now, with SD tunes, you do need to make sure your operating ECT is fairly constant, as your commanded AFR in the OLFA table doesn't exactly correlate at other ECTs.
If you see your closed loop tune acting up when the temperature changes it's not cause the sd tune can't compensate for temperature. I would look for a fix in the charge temp bias vs airflow table.