Chevy Impala SS Forum banner

1 - 20 of 93 Posts
R

·
Guest
Joined
·
0 Posts
Discussion Starter #1
My brother and i are tuning my 1996 impala. We are using EFI Live V7 for logging and Tunercat, And So far so good. We just finished tuning my VE tables and already I noticed more power and better gas mileage. You may be thinking EFI Live is for LS1, it is but it will log LT1 also. There are some things that don’t work like knock count.


“ Let’s start with VE, and the VE table. Volumetric efficiency for our application can be considered, in the simplest of terms, as the amount of air entering the engine. As far as it is used in the VE table, it is a calculation, rather than and actual measured value. This data is entered into the VE table, which is plotted on a MAP vs. RPM basis. VE values are used by the PCM to set the fueling of the engine, in conjunction with the MAF, or solely if we are in SD mode. These values are of course calculated by GM’s engineers to be correct using the stock components the come with our vehicles.
From the factory, our vehicles (for the most part) come equipped with a MAF, which is a device that measures the actual airmass entering the engine. So, if we have a MAF, why do we have a VE table at all? One thing the VE table does is provide a reference airmass calculation. The PCM uses this reference to compare the measured airmass supplied by the MAF to so it can ensure that the MAF is operating correctly. Also, while the MAF is accurate at measuring airmass that is entering the engine at a constant rate, it is not at all accurate when the airmass is changing, like during throttle transitions during normal driving. At these times, the PCM blends the MAF signal with the airmass calculations derived by the VE table to provide accurate fueling. So, above 4000 RPM, or during steady MAP conditions, fueling is set using the airmass measurement provided by the MAF alone. Under 4000 RPM, during unsteady MAP conditions, fueling is set using the airmass measurement provided by the MAF, modified by the airmass calculation derived from the VE table. Understanding the close interaction between the MAF and VE table, it is easy to see why it is important that they both are correct and working together. Unless of course we remove the MAF from the picture completely. More on this later.”
 
R

·
Guest
Joined
·
0 Posts
Discussion Starter #3
Most people don't like OBD II. i do and the more i understand it the easer it is to tune it. I am about to start working on tuning my MAF soon.
 
K

·
Guest
Joined
·
0 Posts
Discussion Starter #4
What I was saying was, I don't believe OBD-I 8051 PCMs use the VE tables for fueling when they are in MAF mode. What you pasted says the OBD-II LT1 PCM does use VE, even in MAF mode. Frankly it sounds like more sophisticated control and may be why OBD-II cars have historically produced lower power numbers than OBD-I cars: the tuner didn't bother dialing in VE. Hmm.
 
R

·
Guest
Joined
·
0 Posts
Discussion Starter #5
OBDI and OBDII functions the same. They have to perform the same task, meter the fuel delivery. The reason why "OBD-II cars have historically produced lower power numbers than OBD-I cars:" is because the tuner didn't bother dialing in VE. They are very important in both applications maybe OBDII uses the VE tables more for better emissions.

My 1994 camaro has OBDI and the more bolt on I put on the car the worse it ran and I started to get knock. The knock I was getting was during aggressive throttle movement. My impala is doing the same thing and it is pig rich at low RPM. After tuning VE tables I have better Gas mileage, the engine is more responsive, and I have more power.

Let’s play the numbers game!


1994 Camaro lt1 OBDI
I ran 14.1 at 98 mph 60ft 2.3 all day with bolt on.
headers, no cats, 3" cat back, 1.6 roller rockers, TB, K&N intake, MSD wires (later I went to stock wires), 4.10:1 gears, sound system, and injectors.
After tuning VE tables and nothing else 13.1 at 107 mph 60ft 2.3 with cats I just pass Maryland emission and my clutch was slipping when I put it into 3rd gear.

2000 camaro LS1 OBDII
My brother’s car 13.7 not sure on MPH.
Bolt on, air intake and exhaust.
Hours of tuning later!
12.7 Not sure on MPH.
Now he has others mods and a cam. His car is fully loaded just no back seats and race rims. 11.6 At 120 MPH all tuning no power add on (NA).

I did not run the impala yet.

So I have 3 cars that have Positive improvements with tuning the VE tables ranging from OBDI and OBDII, LT1 and LS1

I think it is time to put to rest the theory that OBDI is better than OBDII.
 
K

·
Guest
Joined
·
0 Posts
Discussion Starter #6
Wow, that's encouraging. Think it's worth it on a stock car?

So does VE appear to be used in MAF mode to effect BLMs on either OBD-I or OBD-II PCMs? Historically, everyone says that the 8051 does NOT use VE to control BLMs in MAF mode, but obviously it will in speed density.
 
A

·
Guest
Joined
·
0 Posts
Discussion Starter #7
How about this theory. For OBD2 cars, run a OBD1 conversion PCM, datalog in SD mode with DataMaster, fine tune the VE table using the BLM #'s, revert to non-SD and tune MAF tables using the BLM's. Copy the OBD1 file tables into the OBD2 file tables and prog your OBD2 pcm.
Viola! Now you have a perfectly tuned OBD2 car or am I totally off the mark.

AkNovaMan
 
G

·
Guest
Joined
·
0 Posts
Discussion Starter #8
Hey Rich, care to post up your .bin file so we can compare the changes you've made ?
 
R

·
Guest
Joined
·
0 Posts
Discussion Starter #9
aknovaman

your close but you can do what you did to the OBDI to the OBDII no need to convert.
that is what i did.

I don't know how to post my bin file but if someone would tell me or i could send them a email.
 
R

·
Guest
Joined
·
0 Posts
Discussion Starter #11
More Numbers for the nonbelievers.
:eek:
This is my brothers cam only 2000 LS1 camaro.
VE TUNED ALL THE WAY!!


 
A

·
Guest
Joined
·
0 Posts
Discussion Starter #12
What cam are you using? Any suggestions for a 5.3 LS1 truck?
AkNovaMan
 
R

·
Guest
Joined
·
0 Posts
Discussion Starter #13
Originally posted by rich91080:
OBDI and OBDII functions the same. They have to perform the same task, meter the fuel delivery.
They have a different algorithm of calculating the amount of fuel delivered. OBD-I does not use VE tables if the MAF is connected. If you don't believe me, zero out the VE tables in a OBD-I. The car will run just as well. I tried it with my old setup. If your claim was true, the car would not run at all.

OBD-II does use VE tables to verify MAF operation.
 
R

·
Guest
Joined
·
0 Posts
Discussion Starter #14
Here is some food for thought taken from

http://www.customefis.com/GMEFI.html


VE – Volumetric Efficiency is a term that corrects for different engine efficiencies. An engine is basically an air pump and the better the pump, the more power it can generate. Some engines are better pumps than others at a given RPM and MAP condition, so this term allows the equation to be calibrated for different engines. This is the single most important term that a speed density EFI system is famous for. There is a table in the ECM EPROM (chip) that gives VE for a given RPM and MAP condition. The important concept to grasp here is that the VE table is used in both open and closed loop modes, and essentially all modes. What is not so obvious to a novice is that this table, when programmed correctly, will result in a 14.7 A/F ratio with no closed loop or open loop correction taking place. In other words, this table provides a baseline that tells the ECM where 14.7 A/F ratio is so that other A/F ratios can be commanded and the ECM will be at the desired AFR. When this table is adjusted correctly, the engine runs the smoothest, not because the engine is running at 14.7 necessarily, but because all other ratios depend on this table being accurate. If this table is off, the closed loop term will correct the A/F ratio back to 14.7 to a degree. If this table is way off, the closed loop term can’t compensate and the engine may not run period. A good example of when this table needs adjusting is when a hot cam is installed. A stock cam typically idles at 17 inches vacuum. But a hot cam might idle at 15 inches or less of vacuum. The VE table will be calling for more fuel at a lower vacuum reading (higher MAP), but the engine doesn’t need the extra fuel because its still idling. In this case, the calibration doesn’t match the engine’s airflow characteristics. Unless the VE table is changed to lower the efficiency at this MAP and RPM, the engine will run very rich and probably stumble and blow black smoke. The majority of retuning a GM EFI system for non-GM and non-stock engines is done in the VE table since this is the baseline of the entire system.
 
I

·
Guest
Joined
·
0 Posts
Discussion Starter #15
Originally posted by rich91080:
More Numbers for the nonbelievers.
:eek:
This is my brothers cam only 2000 LS1 camaro.
VE TUNED ALL THE WAY!!
Sorry, but a difference of 3TQ/HP isn't convincing evidence. I've done a lot of dyno pulls and typically see 5 HP/TQ differences between pulls with no changes. Now if you had 10-20HP, that would be convincing.

Also, 3 HP/TQ increase does NOT = a second decrease from ET. There are other factors in play... weather, traction, etc...
 
R

·
Guest
Joined
·
0 Posts
Discussion Starter #16
Got 'Cupcake' Bearings?

you misunderstood there is no tuning between pulls it was just 2 pulls. And also it is more than you.

Listen guys read the info I post if you want believe it if you want, but on race day I will be there and all you nonbelievers will be in my rear view mirror.


Funny thing is no one is showing me anything that proves the information I have posted wrong. Everyone just say “it’s wrong it’s wrong” but no one is supporting there argument.


Again I am quoting from web site that is not biased.
 
R

·
Guest
Joined
·
0 Posts
Discussion Starter #17
Originally posted by rich91080:
Here is some food for thought taken from

http://www.customefis.com/GMEFI.html


VE – Volumetric Efficiency is a term that corrects for different engine efficiencies. An engine is basically an air pump and the better the pump, the more power it can generate. Some engines are better pumps than others at a given RPM and MAP condition, so this term allows the equation to be calibrated for different engines. This is the single most important term that a speed density EFI system is famous for. There is a table in the ECM EPROM (chip) that gives VE for a given RPM and MAP condition. The important concept to grasp here is that the VE table is used in both open and closed loop modes, and essentially all modes. What is not so obvious to a novice is that this table, when programmed correctly, will result in a 14.7 A/F ratio with no closed loop or open loop correction taking place. In other words, this table provides a baseline that tells the ECM where 14.7 A/F ratio is so that other A/F ratios can be commanded and the ECM will be at the desired AFR. When this table is adjusted correctly, the engine runs the smoothest, not because the engine is running at 14.7 necessarily, but because all other ratios depend on this table being accurate. If this table is off, the closed loop term will correct the A/F ratio back to 14.7 to a degree. If this table is way off, the closed loop term can’t compensate and the engine may not run period. A good example of when this table needs adjusting is when a hot cam is installed. A stock cam typically idles at 17 inches vacuum. But a hot cam might idle at 15 inches or less of vacuum. The VE table will be calling for more fuel at a lower vacuum reading (higher MAP), but the engine doesn’t need the extra fuel because its still idling. In this case, the calibration doesn’t match the engine’s airflow characteristics. Unless the VE table is changed to lower the efficiency at this MAP and RPM, the engine will run very rich and probably stumble and blow black smoke. The majority of retuning a GM EFI system for non-GM and non-stock engines is done in the VE table since this is the baseline of the entire system.
Have you missed the "speed density" part in this paragraph?
 
R

·
Guest
Joined
·
0 Posts
Discussion Starter #18
SO

The majority of retuning a GM EFI system for non-GM and non-stock engines is done in the VE table since this is the baseline of the entire system. The important concept to grasp here is that the VE table is used in both open and closed loop modes, and essentially all modes. What is not so obvious to a novice is that this table, when programmed correctly, will result in a 14.7 A/F ratio with no closed loop or open loop correction taking place. In other words, this table provides a baseline that tells the ECM where 14.7 A/F ratio is so that other A/F ratios can be commanded and the ECM will be at the desired AFR. When this table is adjusted correctly, the engine runs the smoothest, not because the engine is running at 14.7 necessarily, but because all other ratios depend on this table being accurate. If this table is off, the closed loop term will correct the A/F ratio back to 14.7 to a degree.
One thing the VE table does is provide a reference airmass calculation. The PCM uses this reference to compare the measured airmass supplied by the MAF to so it can ensure that the MAF is operating correctly. Also, while the MAF is accurate at measuring airmass that is entering the engine at a constant rate, it is not at all accurate when the airmass is changing, like during throttle transitions during normal driving. At these times, the PCM blends the MAF signal with the airmass calculations derived by the VE table to provide accurate fueling. So, above 4000 RPM, or during steady MAP conditions, fueling is set using the airmass measurement provided by the MAF alone. Under 4000 RPM, during unsteady MAP conditions, fueling is set using the airmass measurement provided by the MAF, modified by the airmass calculation derived from the VE table. Understanding the close interaction between the MAF and VE table, it is easy to see why it is important that they both are correct and working together. Unless of course we remove the MAF from the picture completely.
 
K

·
Guest
Joined
·
0 Posts
Discussion Starter #19
Yes, from what I can tell from the source of the quote, that GMEFI guy is talking about speed density tuning, (i.e. NO MAF)


Dang it where is Bry? Bry what do you have to say about dis?

Karl
 
R

·
Guest
Joined
·
0 Posts
Discussion Starter #20
How about this everybody is telling me VE is not important when using the MAF. And then they tell me zero out my VE tables and all this other nonsense. :confused:

Why don't you guys try tuning you VE tables and tell how your car runs. The worst thing that will happen is you will make more power, and get better gas mileage. Everyone says VE tables don't work if this is true tuning them, it won't hurt.
 
1 - 20 of 93 Posts
Top