Thanks!! - VE table adjustment
Thanks!! - VE table adjustment I just wanted to post up a quick thanks to everyone/anyone with the VE table ideas. Let me tell you - wow what a difference. My car ran pretty well for a big cam car (I thought), but after I installed my new adjustments (scaling the VE table 1200rpm and below) my car runs like a dream. On both cold and hot starts my car fires right up and holds an idle at 800 rpm or more - no more of this 1100rpm, 200rpm, 1100rpm, 3000rpm up and down BS that it used to do for a few seconds.
It still is a little rich at idle, but nothing like it was before. Now its time to hit the dyno for some wideband tuning.
It still is a little rich at idle, but nothing like it was before. Now its time to hit the dyno for some wideband tuning.
Re: Thanks!! - VE table adjustment Yeah pretty amazing, huh? I ended up with the 50-60-70 setting and mine's doing better than ever now also. Now if we could just get a little more timing when the engine is cold . . .
Re: Thanks!! - VE table adjustment Load LS1edit, open your current flash file, go to Edit, Engine Cal, Fuel Tab, click on Main Volumetric Efficiency, highlight the entire 400 rpm column, and scale by 50%, apply changes. Then scale the 800 column by 60%, and the 1200 column by 70%. Apply Changes, save to a new file name, then open LS1prog and flash your PCM.
Re: Thanks!! - VE table adjustment Is there a certain parameter we are shooting for when we tweak these numbers? I thought it was to narrow the injector pulse width but later heard this wasn't the case. Any ideas? I'd like to fine tune mine in better since I just used 60% from 400-1200.
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Re: Thanks!! - VE table adjustment You can look at the injector pulse width, should be 3-4 ms. But the most reliable system I've found is my nose and seat of my pants . . . if it stinks, it's rich; if it stumbles when I punch it, it's lean. The problem is there is some kind of software "acelerator pump" that you are also affecting by changing the VE.
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Verdad Gallardo Re: Thanks!! - VE table adjustment
The problem is there is some kind of software "acelerator pump" that you are also affecting by changing the VE.
Re: Thanks!! - VE table adjustment The VE table is used in determining the minimum amount of fuel necessary to keep the car running at that RPM.
Once the base pulswidth is known then car starts adding in all of the other math, load, performance, emmissions, to adjust the cars fueling.
The Accellerator pump that Cal is talking about is the "tip in" richness that is required to give your car the kind of throttle response you want and stop the car from stumbling with sudden load changes.
When you hammer the throttle your throttlebody opens up and the density of the air inside the manifold changes to atmospheric. Your car is suddenly ingesting air that is much more dense (read more oxygen) than it was previously. To keep up with this sudden addition of oxygen and make the most of it your car uses a "tip in" or "accelerator pump" calculation to suddenly change how much fuel is added to accomodate the additional oxygen.
The accelerator pump calculation is based on volumetric efficiency (or speed density). It uses the predetermine correction factors that we see on the VE table to determine the exact amount of oxygen that the car just ingested. If you have reduced the VE table by a significant amount, the accelerator pump function will not add adequate fuel to deal with the sudden influx of air. The result is that the car stumbles or bogs when you stab the throttle.
Adjusting the VE table is like everything else. As long as you don't go wild, you will be fine.
Good Luck,
Kevin
Once the base pulswidth is known then car starts adding in all of the other math, load, performance, emmissions, to adjust the cars fueling.
The Accellerator pump that Cal is talking about is the "tip in" richness that is required to give your car the kind of throttle response you want and stop the car from stumbling with sudden load changes.
When you hammer the throttle your throttlebody opens up and the density of the air inside the manifold changes to atmospheric. Your car is suddenly ingesting air that is much more dense (read more oxygen) than it was previously. To keep up with this sudden addition of oxygen and make the most of it your car uses a "tip in" or "accelerator pump" calculation to suddenly change how much fuel is added to accomodate the additional oxygen.
The accelerator pump calculation is based on volumetric efficiency (or speed density). It uses the predetermine correction factors that we see on the VE table to determine the exact amount of oxygen that the car just ingested. If you have reduced the VE table by a significant amount, the accelerator pump function will not add adequate fuel to deal with the sudden influx of air. The result is that the car stumbles or bogs when you stab the throttle.
Adjusting the VE table is like everything else. As long as you don't go wild, you will be fine.
Good Luck,
Kevin
Re: Thanks!! - VE table adjustment
Adjusting the VE table is like everything else. As long as you don't go wild, you will be fine.
Re: Thanks!! - VE table adjustment
I think Cal nailed the "proper" way.
How much you shift the table is going to be different for every car.
How much you shift the table is going to be different for every car.
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Joined: Nov 2001
Posts: 1,645
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From: Hanover MD
Re: Thanks!! - VE table adjustment when i started tweaking my ve, i would make a small change, then hook up efi live, and go for a spin. i have 2 routes i take, and try to maintain the same driving style on each and see what i end up with.
ve made a huge difference in the few cars that i have tuned for drivability. still havent had a chance to tune on the dyno yet since i am just trying to get the OEM drivability back first.
ve made a huge difference in the few cars that i have tuned for drivability. still havent had a chance to tune on the dyno yet since i am just trying to get the OEM drivability back first.
Re: Thanks!! - VE table adjustment Just to let everyone know. My car has been having problems with Cold starts once I drive off and come to a stop about 3 blocks down the street it will go down to 400rpms then back up to 1000 rpms, it does this all the time until it is up to normal operating temps then it kind of goes away. I first multiplied the 400-1200 by 80% had little to no effect. I then did the 50-60-70. That was a no no for my car, so goes to show that all cars are not the same. When I came to a stop it would just sit at 400 rpms and wouldn't go up at all. So its putting a lot of air in but no fuel. I then went back to stock and then adjusted by multi by 70% 400-1200 rpms seems to be a lot better for now, but I might need to adjust IACs a little bit. The other problem that I have is the bucking issues at around 1500 rpms. I noticed when I did the 70% it helped a little bit, but its still there. Any help would be appreciated thanks. BTW Great thread too and Cal for his tips 
Re: Thanks!! - VE table adjustment Well, after more miles on the 60% VE tune for 400-1200, the car has reverted back to it's stalling and surging with hot starts and seems to be getting worse.
Any Ideas now?
Any Ideas now?
TECH Addict
Joined: Nov 2001
Posts: 2,207
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From: College Station, Tx
Re: Thanks!! - VE table adjustment How much time do you spend driving in the 400-1200 range? Assuming the tables are indexed correctly you should only have a change in that range.
Now if your l-trims are different and are carrying over a bit that could cause a problem, but it should still only be for a bit untill you move into a new cell.
What it boils down to is that your O2's are fixing your part throttle a/f ratio. Do you have splits between your two sides - is it possible you have an exhaust leak anywhere?
Try resetting your computer and seeing if the fix holds for awhile again - if it does it is almost certainly your o2's initiating a fueling change. Have your l-trims/s-trims changed at all?
Now if your l-trims are different and are carrying over a bit that could cause a problem, but it should still only be for a bit untill you move into a new cell.
What it boils down to is that your O2's are fixing your part throttle a/f ratio. Do you have splits between your two sides - is it possible you have an exhaust leak anywhere?
Try resetting your computer and seeing if the fix holds for awhile again - if it does it is almost certainly your o2's initiating a fueling change. Have your l-trims/s-trims changed at all?
Re: Thanks!! - VE table adjustment Haven't logged the L-trims, I thought they were useless at that low of a range.
Suprisingly, with the 2.73 gear I spend alot of time in the 1000-1200 rpm range which I believe adds to the problems. Around town cruising the car stays pretty near 1000 rpm untill I get on the highway or something. Maybe I need to tweak my shift tables to hold it higher before it shifts to the next gear?
Suprisingly, with the 2.73 gear I spend alot of time in the 1000-1200 rpm range which I believe adds to the problems. Around town cruising the car stays pretty near 1000 rpm untill I get on the highway or something. Maybe I need to tweak my shift tables to hold it higher before it shifts to the next gear?
Joined: Nov 2001
Posts: 34,632
Likes: 2,557
From: Schiller Park, ILL Member: #317
Re: Thanks!! - VE table adjustment
How much time do you spend driving in the 400-1200 range? Assuming the tables are indexed correctly you should only have a change in that range.
Now if your l-trims are different and are carrying over a bit that could cause a problem, but it should still only be for a bit untill you move into a new cell.
What it boils down to is that your O2's are fixing your part throttle a/f ratio. Do you have splits between your two sides - is it possible you have an exhaust leak anywhere?
Try resetting your computer and seeing if the fix holds for awhile again - if it does it is almost certainly your o2's initiating a fueling change. Have your l-trims/s-trims changed at all?
Now if your l-trims are different and are carrying over a bit that could cause a problem, but it should still only be for a bit untill you move into a new cell.
What it boils down to is that your O2's are fixing your part throttle a/f ratio. Do you have splits between your two sides - is it possible you have an exhaust leak anywhere?
Try resetting your computer and seeing if the fix holds for awhile again - if it does it is almost certainly your o2's initiating a fueling change. Have your l-trims/s-trims changed at all?
I have it to a point where both cold and warm starts seem to be good at the moment (knock on wood).My Ltrims are elevated and split at idle, (about +13.3 and +7.8) not sure why they are split but they pretty much even out as I drive. Strims are good (and even).
Do you think Ltrims are my issue? I have messed with all kinds of IAC changes and many different VE table chnages in the 400-1200 range and I'm getting frustrated again. I was gonna try raising the idle some, but I don't think that will help any (idle is at 800rpm in P & D).
Should I try adjusting my IFR table to bring down the Ltrims a little? Would that have an effect on my intermittent surge while stopping issue?