Cranking VE vs Primary VE vs Secondary VE
08-19-2015, 09:17 AM
#1
Moderator
Thread Starter
iTrader: (4)
Join Date: Jul 2014
Location: My own internal universe
Posts: 10,446
Received 1,836 Likes
on
1,145 Posts
Cranking VE vs Primary VE vs Secondary VE OK, I'm trying to rough in my new build, and warmed up, running smooth, exhaust smells good, O2's switching, etc.
The primary and secondary VE tables are in full agreement with each other. The cranking VE's are WAY off. Like almost double. I just took 20% out of the cranking VE's, and she fired right up instead of lazily coming to life, but still starts incredibly rich - just not eyes-bleeding rich.
I also took some VE out of the primary and secondary tables at 800 and 1200, but now it seems like it doesn't run right until it gets to 1600 rpm, so I think I need to put those values back, but that could also be residual flooding from start up
So, my questions are:
1. Should the cranking VE's be roughly the same as the primary and secondary VE's - at least on those cells that are duplicates?
2. How long does the motor run on the cranking VE's before switching over to primary/secondary, and how can I change this?
The primary and secondary VE tables are in full agreement with each other. The cranking VE's are WAY off. Like almost double. I just took 20% out of the cranking VE's, and she fired right up instead of lazily coming to life, but still starts incredibly rich - just not eyes-bleeding rich.
I also took some VE out of the primary and secondary tables at 800 and 1200, but now it seems like it doesn't run right until it gets to 1600 rpm, so I think I need to put those values back, but that could also be residual flooding from start up
So, my questions are:
1. Should the cranking VE's be roughly the same as the primary and secondary VE's - at least on those cells that are duplicates?
2. How long does the motor run on the cranking VE's before switching over to primary/secondary, and how can I change this?
08-19-2015, 11:58 AM
#3
Return cranking VE to stock. I haven't found a case where changing it made much difference.
Tune the primary VE table. You'll notice at startup that you're in the 85-100 kPa range on the 400 cells there. Lower those values. That's where the fuel add comes from.
Also, add 2 degrees to your startup timing.
Tune the primary VE table. You'll notice at startup that you're in the 85-100 kPa range on the 400 cells there. Lower those values. That's where the fuel add comes from.
Also, add 2 degrees to your startup timing.
08-19-2015, 12:23 PM
#4
Moderator
Thread Starter
iTrader: (4)
Join Date: Jul 2014
Location: My own internal universe
Posts: 10,446
Received 1,836 Likes
on
1,145 Posts
Thanks, Jake, I'll try that on my lunch break. I won't get a cold start, but a warm start will still give the low RPM conditions.
I added 1 to the EOIT "normal" table, and when she warms up, it's quite nice. You wouldn't know it was a performance cam from the smell. 8 degrees overlap, and it smells like stock. Does the EOIT need to fire early to warm the fuel on the intake valve when the engine is cold, or can I set the entire normal table to 6.55 to avoid the overlap fueling?
I can always just try it and if it doesn't work put it back, I guess, but thought I'd ask while I'm making the edit anyway.
I added 1 to the EOIT "normal" table, and when she warms up, it's quite nice. You wouldn't know it was a performance cam from the smell. 8 degrees overlap, and it smells like stock. Does the EOIT need to fire early to warm the fuel on the intake valve when the engine is cold, or can I set the entire normal table to 6.55 to avoid the overlap fueling?
I can always just try it and if it doesn't work put it back, I guess, but thought I'd ask while I'm making the edit anyway.
08-19-2015, 03:13 PM
#5
Moderator
Thread Starter
iTrader: (4)
Join Date: Jul 2014
Location: My own internal universe
Posts: 10,446
Received 1,836 Likes
on
1,145 Posts
Good call, Jake!! thank you so much.
I left the EOIT alone (already added 1 to the normal table before) so I don't change too much at once. I added 2 degrees to the cranking spark table. I took a bunch of VE out of 400 from 85 to 105. I also took some out of the same range in the 800 column. I had previously pulled some out of the 1200, but I was getting a delay in power, so I put those back where they were.
I left the cranking VE table alone, again to make few changes at once.
Fired right up, no delay in idling, no gas fumes. Smells stock now.
Problem solved.
I left the EOIT alone (already added 1 to the normal table before) so I don't change too much at once. I added 2 degrees to the cranking spark table. I took a bunch of VE out of 400 from 85 to 105. I also took some out of the same range in the 800 column. I had previously pulled some out of the 1200, but I was getting a delay in power, so I put those back where they were.
I left the cranking VE table alone, again to make few changes at once.
Fired right up, no delay in idling, no gas fumes. Smells stock now.
Problem solved.
08-19-2015, 11:13 PM
#6
Yup. I have swapped injectors on this build a couple of times and had a fuel pump problem. So I learned the intricacies of the fueling tables BIG TIME. lol
EOIT just set to 6.55 across the board. It's not really ECT dependent even though the table shows that. I have mine set to 6.25 based on calculations I saw. When you change it your A/F changes with it. So be aware of that.
EOIT just set to 6.55 across the board. It's not really ECT dependent even though the table shows that. I have mine set to 6.25 based on calculations I saw. When you change it your A/F changes with it. So be aware of that.
08-20-2015, 10:42 AM
#7
Moderator
Thread Starter
iTrader: (4)
Join Date: Jul 2014
Location: My own internal universe
Posts: 10,446
Received 1,836 Likes
on
1,145 Posts
10-4. If anything, the changes I made at the hotter temps improved AFR and throttle response, so I'm pretty sure it'll help all around.
Will it necessitate a change in VE tables, or just the afterstart PE side?
Will it necessitate a change in VE tables, or just the afterstart PE side?
Trending Topics
08-20-2015, 04:55 PM
#8
VE table changes typically. You're changing when you spray fuel. So you end up with a better burn and less unburnt fuel by delaying the EOIT. You should notice better response and a smoother idle too.
I was able to drop my idle down another 100 RPM to get the chop back. And I also was able to add a ton of timing in my low RPM cells (which is counter-intuitive to a big cam - usually you do less timing in the 1400-1600 cells to force the motor to load up to get rid of bucking... I had to go from 22 degrees to 34-36 in those areas to get rid of bucking - but damn it's make a **** ton of torque there).
I was able to drop my idle down another 100 RPM to get the chop back. And I also was able to add a ton of timing in my low RPM cells (which is counter-intuitive to a big cam - usually you do less timing in the 1400-1600 cells to force the motor to load up to get rid of bucking... I had to go from 22 degrees to 34-36 in those areas to get rid of bucking - but damn it's make a **** ton of torque there).
08-20-2015, 07:24 PM
#9
VE table changes typically. You're changing when you spray fuel. So you end up with a better burn and less unburnt fuel by delaying the EOIT. You should notice better response and a smoother idle too.
I was able to drop my idle down another 100 RPM to get the chop back. And I also was able to add a ton of timing in my low RPM cells (which is counter-intuitive to a big cam - usually you do less timing in the 1400-1600 cells to force the motor to load up to get rid of bucking... I had to go from 22 degrees to 34-36 in those areas to get rid of bucking - but damn it's make a **** ton of torque there).
I was able to drop my idle down another 100 RPM to get the chop back. And I also was able to add a ton of timing in my low RPM cells (which is counter-intuitive to a big cam - usually you do less timing in the 1400-1600 cells to force the motor to load up to get rid of bucking... I had to go from 22 degrees to 34-36 in those areas to get rid of bucking - but damn it's make a **** ton of torque there).
08-20-2015, 07:51 PM
#10
To force the motor to load up, thereby pushing RPM up and opening the throttle blade more.
When the blade is very nearly cracked and both the intake and exhaust valves are open due to the higher overlap of the bigger cam, the exhaust provides a "path of least resistance." Then you get dirty air in there and that makes for a bad burn. As resistance is decreased from a fresh intake charge, by opening the blade, the likelihood of sucking in spent exhaust gas is less.
When the blade is very nearly cracked and both the intake and exhaust valves are open due to the higher overlap of the bigger cam, the exhaust provides a "path of least resistance." Then you get dirty air in there and that makes for a bad burn. As resistance is decreased from a fresh intake charge, by opening the blade, the likelihood of sucking in spent exhaust gas is less.
08-20-2015, 07:53 PM
#11
Moderator
Thread Starter
iTrader: (4)
Join Date: Jul 2014
Location: My own internal universe
Posts: 10,446
Received 1,836 Likes
on
1,145 Posts
VE table changes typically. You're changing when you spray fuel. So you end up with a better burn and less unburnt fuel by delaying the EOIT. You should notice better response and a smoother idle too.
I was able to drop my idle down another 100 RPM to get the chop back. And I also was able to add a ton of timing in my low RPM cells (which is counter-intuitive to a big cam - usually you do less timing in the 1400-1600 cells to force the motor to load up to get rid of bucking... I had to go from 22 degrees to 34-36 in those areas to get rid of bucking - but damn it's make a **** ton of torque there).
I was able to drop my idle down another 100 RPM to get the chop back. And I also was able to add a ton of timing in my low RPM cells (which is counter-intuitive to a big cam - usually you do less timing in the 1400-1600 cells to force the motor to load up to get rid of bucking... I had to go from 22 degrees to 34-36 in those areas to get rid of bucking - but damn it's make a **** ton of torque there).
And you answered my next question - I was going to ask if I should add timing to the idle range cells like I did for start up. I get this sort of momentary delay when I gas it down low, but when it gets to 3K, hang on tight. I had thought adding a few degrees would be beneficial. I would never have guessed adding 12 degrees.
I must be on the right track if I keep finding stuff in line with your observations!
08-21-2015, 08:39 AM
#13
Moderator
Thread Starter
iTrader: (4)
Join Date: Jul 2014
Location: My own internal universe
Posts: 10,446
Received 1,836 Likes
on
1,145 Posts
10-15-2017, 05:53 AM
#14
TECH Addict
Return cranking VE to stock. I haven't found a case where changing it made much difference.
Tune the primary VE table. You'll notice at startup that you're in the 85-100 kPa range on the 400 cells there. Lower those values. That's where the fuel add comes from.
Also, add 2 degrees to your startup timing.
Tune the primary VE table. You'll notice at startup that you're in the 85-100 kPa range on the 400 cells there. Lower those values. That's where the fuel add comes from.
Also, add 2 degrees to your startup timing.
Thanks Joe
09-20-2021, 05:16 AM
#16
Hey Jake, would you mind sharing a copy of that tune? I've been fighting some startup issues and I'm concerned where that trend will go as the weather starts to cool off around here. I'm also interested in that part you mentioned about adding timing to get rid of bucking. I've got 2 spots that I can't seem to smooth out. One is around 20-25mph when cold with light throttle and the other is around 40mph with light decel.
The following users liked this post:
G Atsma (09-20-2021)