Idle / to rich in open loop /

Ok at start up the car is death how do i clean this up , i have nop cat but the car should not stink likr this, do i make the change in
AFR X10 vs coolant temp
now do i add to lean out or
take away to lean out
thx

Ok #1 What year car, OBD1 or OBD2 ?

Tunercat or LT1_edit ?


Just some ideas, to lean out your fuel mixture at idle first you need to hook up a scan tool and see what KPA the car idles at. Then go to your Volumetric Efficency tableand start lowering the numbers in this table area. Once you have the idle tuned, you will need to smoothen out your VE tablearound where you changed so that it smoothly transfers to the next VE table upon acceleration.

Also make sure your fuel injectors have hte correct offsets or tunign is absolutly useless

Chopping up your MAF tables is not recomended, causes irratic acceleration problems.

Subtracting values in the VE table subtract fuel. Basically your telling the engine it is less efficient at X value so it adds less fuel.
A Pro I will not name whos on this forum, told me VE tables is the place to tune.

ALSO VERY IMPORTANT, Your car probably idles in a different MAP range than it used to. You MUST Increase the spark timing in this KPA range to what your car would usually be in when it was stock.
Stock LT1s usually idle between 25-35 KPA, so transfer these timing numbers to the KPA range your car now idles at. This will help your idle richness alot too.

OBD1 car/tuner cat

-what KPA the car idles at, my car idles at 55-60 kpa

-Volumetric Efficency table, what dose this do/for/how much to start with

- you will need to smoothen out your VE tablearound where you changed so that it smoothly transfers to the next VE table upon acceleration.
i thought the ve table was for speed den/ cars

-Also make sure your fuel injectors have hte correct offsets or tunign is absolutly useless, i have 30lbs svo offset at 31.68, F/P set at 43 vac off.

ya i have played with the maf tables and i can fell the tip in/ put it back to stock.

will this help with the high/low blm

i have my timing up to 34* in the closed tps table

this is great info need more thanks

Originally posted by Schurters LT1
- you will need to smoothen out your VE tablearound where you changed so that it smoothly transfers to the next VE table upon acceleration.
i thought the ve table was for speed den/ cars

VE tables are for speed density cars. If you want to do a little experiment, change your ve tables to all 100's...I'll bet it doesn't make one bit of difference on a mass air car.

Also make sure your fuel injectors have hte correct offsets or tunign is absolutly useless, i have 30lbs svo offset at 31.68, F/P set at 43 vac off.

That is your injector constant, not the offsets. :)

I beg to differ DAN K. I have a 97 OBD2 LT1 383 stroker. On the dyno We tuned the VE tables and gained 40 HP. The VE tables are used in MAF cars and DO have an effect.

Basically if you have the VE set to 87 at 3000 RPMS @ 100 KPA this means the PCM will think the engine efficiently uses 87% of the air ingensted into the engine when at Wide open throttle @ 3000 RPMs. Subtract from this number and the PCM sees the engine is less effecient and subtracts fuel and vice versa.

Now the MAF tables allow the PCM to compensate for air temp, humidity and such. Which does change the actual fueling of the PCM. But the PCM starts with the VE tables and uses the MAF and O2s to make changes based on the NUMBERS in the VE table.

Im not certain where the rumor or theory that VE tables do nothing for MAF cars came from or who researched it. I know for a fact someone thats on this board that some of you have even paid for tunes from, has told me VE tables is where its at. My car is the most radical solid roller LT1 383 stroker you can imagine. And the MAF tables are STOCK, the Injector constants are NOT TWEAKED, and the O2s are fully functional, even the PE tables are BARELY increased from STOCK numbers. I tuned with PE table and SPark Advance Table only.


Schurters LT1

As far as closed throttle spark advance 34 is a good number for idle. I actually use 40 degrees at closed throttle. But make sure when you tip into the throttle that the KPA area in the timing tables are GREATER or EQUAL to the closed throttle position or you will get a stumbling. What you should do is find a spark advnce number where you get no spark retard at an idle and work it all the way to 100 KPA. So your timing tables need to be revised from 60KPA to 100KPA.

My timing tables only operate in 75-100 KPA, so at 75-85 KPA I ahve 41 degrees of timing at lower RPMs, 85-95KPS I have 39-40 degrees and at 100 KPA I ahve 39-38 degrees of timing in lower RPM talbes.

You should first try these spark numbers all teh way to about 3500 RPMS then slowly start pulling timing out at 100 KPA until at 6000 RPMs its at about 33 degrees. Then test for spark retard, if you do not get any then you can increase the timing at WOT. Now the lower the KPA at the same RPM you should increase the timing. EXample: AT 4000 RPMS @ 100 KPA ( full throttle) I have 37 degrees of timing, but at 4000 RPMs @ 90-95 KPA I have 38 degrees of timing, 4000 RPMs 80-85 KPA I have 39 degrees and 70-75 KPA @ 4000 RPMs I have 40 degrees of timing.

The key is to make all transitions smooth and even, yo ucant have the timing tables or VE tables all over hte palce or your car will perform " all over the palce"

I am sorry but i realy don't understand the ve table:confused: i see that i can add/sub with this change my fuel rich/lean sorry can you give me a better walk through on this ;) i want to now all this i think it is very cool:thumb:

your timing table so you are saying
0-rpm to 4000rpm in the 75-85 kpa 41*
85-95 kpa 39*-40*
95-100 kpa 38=39*

tell me about the ve table frist then when i get that timing
thxJeremy

well you need to adjust your timing table 1st before you go adjusting your VE tables.


im aboutto watch the dolphins game. But email me a copy of your tune to tripintaz@bellsouth.net I will take a look at it and see what I can do for ya:)

If you're only running too rich at idle when you first start the car, then you should only modify (raise) the AFR x 10 vs. Coolant table, since you'll be in open loop at that point.

VE tables will affect both open and closed loop.

I over read that part, If you are only rich while cold idle(open loop) then adjusting your AFR tables in that area is the way to go.

Remember the higher the number the LESS fuel.

14:1 A/F ratio is 14 parts air to 1 part fuel(leaner)

10:1 A/F ratio is 10 parts air to 1 part fuel (richer)

Originally posted by TriPinTaZ
I beg to differ DAN K. I have a 97 OBD2 LT1 383 stroker. On the dyno We tuned the VE tables and gained 40 HP.

When I first got into tuning LT1's I started by doing searches in this forum for different things and reading the LT1 Edit list archives. Most of what everyone said was that on an OBD1 maf car the ve tables were not factored into the the cars fueling at part throttle.
There wasn't much discussion about wot fueling being affected by the ve tables. To me it seems like it would more involved than just using the pe vs rpm table anyways, so I never worried about it.
I have seen files from just about every tuner that has done LT1 stuff. Most have not altered the ve tables in any way. But a couple have. The 1 thing that I noticed was that the high rpm/high map ve area was all set at 99.6, which I believe is the highest value that tunercat shows. I never knew why this was done.
When you were doing your tuning on your car, how did you know what to change in the ve tables, and why?
What is the advantage of using the ve tables to tune wot rather than just using the pe tables?

And whether or not ve tables are used at part throttle isn't worth debating. As long as the long term fuel trims are adjusting between 108 and 160 then the PCM is correcting your fueling and you aren't running rich or lean...you're right at 14.7:1.

So to me the only advantage to using the ve tables would be for wot, but why would you do that rather than just use the pe tables?

Simple..... VE tables allow for a much more accurate Tune for Part throttle and WOT.

The MAF tables are kind of like a crap shoot and the PE talbes are only applied at WOT. my MAF tables are stock and my PE tables are near stock. all I did was add 2% more fuel ontop of stock PE.

As for tuners leaving the VEtabels stock, its perfectly ok to use the stock PE tables for small cams such as the LT4 hotcam or cc306. The PCM can compensate for a small cam like these with minor tweaks to the MAF tables and injector constants and timing tables. However ask anyone of them using the MAF table changes, if not done correctly will always result in a stumble at any given RPM when the MAF tables were not changed SMOOTHLY. ITs basically tricking the PCM which works just fine for some applications. But if your Mods are more radical like mine you HAVE to use the VE talbes. Actually all tunes should use the VE tables but it requires dyno time to get them right. So aslong as the PCM can be tricked while keeping the BLMs between 108-160 your "mail order" tune will be ok. Not putting them down one bit and they are well worth the money.

However I have a huge solid roller custom ground cam and changing the VE tables was the only way to get this thing to run properly. The person that helped me with this tune not only had has a cam almost as big as mine, but had his car on the cover of High Tech GM magazine, and he uses OBD1 and tunercat. He only changes his VE tables and Timing tables.

Even aftermarket PCMs like FAST and DFI 7 and MOTEC use the VE tables for tuning, However the MAF is not even used. So the car does not compensate for weather changes such as air temp and humidy as well as a MAF car would.

:)

Originally posted by TriPinTaZ
Simple..... VE tables allow for a much more accurate Tune for Part throttle and WOT.

I can see that. Since the ve tables allow for more of a defined change (rpm vs map) rather than the maf tables (afgs) then it would make sense that you can get more accurate with the fueling.

The MAF tables are kind of like a crap shoot and the PE talbes are only applied at WOT. my MAF tables are stock and my PE tables are near stock. all I did was add 2% more fuel ontop of stock PE.

So what are you changing by changing the ve tables? For the part throttle stuff are you just targeting a 128 blm?
I'm still not sure why it would matter what your long term fuel trims are as long as they have the ability to adjust. Shooting for 128 or whatever just seems like overkill.

ITs basically tricking the PCM which works just fine for some applications.

How is changing the ve tables resulting something different than changing the ve tables.? Either way you're changing the way that the PCM calculates it's fueling. Both ways are based on airflow that the PCM reads from a particular sensor...and the maf should be a more accurate way with regards to weather conditions. In otherwords, what is the advantage of a maf sensor if all fueling changes can be more accurately made by changing the ve tables.

But if your Mods are more radical like mine you HAVE to use the VE talbes.

Very unclear as to why?

Actually all tunes should use the VE tables but it requires dyno time to get them right.

Why? What are you targeting with the ve tables? I guess for part throttle you are targeting a 128 blm? Why does it matter for part throttle anyways if blm is adjusting your fueling to achieve a 14.7:1 a/f ratio.
Then for wot you're using wideband a/f data? Why is this better than just using the pe tables for simplicity purposes?


So aslong as the PCM can be tricked while keeping the BLMs between 108-160 your "mail order" tune will be ok.

Why do you consider maf table and injector constant adjustments "tricking"? Aren't these changes doing the same thing as your modifying the ve tables?

Not putting them down one bit and they are well worth the money.

Ok, then I will. I have yet to personally see a mail order anything be remotely close. Seen quite a few things on here, but in person I've never seen 1 even close. :)

but had his car on the cover of High Tech GM magazine

I hope this doesn't really mean anything...:)

Very interested in this as I may be tuning a large solid roller car in the spring. :)

in the AFR x 10 vs. Coolant table vs map what does this mean if the table has a number in it say (142) is that accually 14.2 to 1 a/f ratio the X 10 part is throughing me of what does that mean in the table. what im trying to say is what does the 142 mean. and if i wanted to lean it out i would raise the number corect.

Originally posted by 97Z-M6
in the AFR x 10 vs. Coolant table vs map what does this mean if the table has a number in it say (142) is that accually 14.2 to 1 a/f ratio the X 10 part is throughing me of what does that mean in the table. what im trying to say is what does the 142 mean. and if i wanted to lean it out i would raise the number corect.

14.2 X 10 = 142

so 137 = 13.7 X 10

the lower you go the more fuel is added.

DAN K

- when you chage the VE table lower you are telling the PCM that the engine is less efficient in complete/efficiant combustion.

@ 75 KPA @ 3000 RPMs the VE table reads 87.5 on my tune. This simply means, at that given operating parameters 87.5% of the air entering the engine is being efficiently combusted. Therefor the PC adds X amount of fuel. If you lower this number the PCM will say there is less air being efficiently combusted, so the PCM adds less fuel. Then in closed loop the PCM use the numbers in teh VE tables as a base reference and uses the MAF and O2s to correct A/F.

So changing the MAF sensor tables changes the way the MAF compensates for correct A/F with the 02s. Basically this will work fine. But becomes very innacurate when the engine becomes heavily modified like mine. And inhibits the PCMs ability to compensate for proper A/F acroos the ENTIRE operating parameters of the engine and not just WOT.


As far as wideband O2, You tune the PE for WOT, from this point you need to work the table smoothly down through the operating range at part throttle and decal. Then it takes time and driving and data logging to tune out any tweaks, such as idle too rich or stumbling. ( timing tables help greatly here too)

Like I stated it takes time , but when done correctly the car runs great. I ahve tuned my cars VE tables atleast 20 times from the Dyno tune. You just keep the 95-100 KPA tables from the dyno and use that as a basis for your tune.

TriPinTaz, I'm interested in whole VE table concept and what it does for the engine at part throttle. I've seen a lot of people go back and forth over whether or not they do anything or if they do nothing at all (In my opinion they have to do something, otherwise GM wouldn't have the things in there). Do you have any more information or documents that could help to explain these tables and their effects based on mods better? I've not yet had to use them, but I'd like to be able to utilize every aspect of tuning rather than just the majority of them.

I know how the ve tables work and what the values mean. I've done a couple of 93's and they work off of the ve tables, so that's not the issue.
I guess I still don't understand what you're shooting for when tuning the ve tables for anything other than wot? Are you just tuning by what the car feels like or trying to get a certain blm? Part throttle doesn't really need much fueling work as the PCM adjusts via O2 sensor feedback. As long as you're within range, you're fine. Just seems to me that some folks worry a little too much about part throttle fueling and trying to get a 128 blm because they think that any value under this means you're rich and over it means you're lean.
I just don't understand what the advantage of tuning the ve tables is when part throttle fueling is all done by the PCM and when wot can be done through pe tables.
But I'd love to learn. :)

well quite frankly, until you have more experience in the area of VE tuning I dont expect you to understand.

Basically if you get the VE tables right, there is LESS for the PCM to correct. and the cars performance is more consistant during part throttle driving.

OUCH:alert: That is out of line:mad:

TriPinTaZ we are all on here to learn how to tune your cars and help others, tell us help us under stand how the ve tables work and work with the PE tables and the coolant tables, for driving and wot, i would like to know this too.

hey winter is coming i have allot of time to read :D

Originally posted by Schurters LT1
OUCH:alert: That is out of line:mad:

TriPinTaZ we are all on here to learn how to tune your cars and help others, tell us help us under stand how the ve tables work and work with the PE tables and the coolant tables, for driving and wot, i would like to know this too.

hey winter is coming i have allot of time to read :D

i didnt mean for it to be so harsh. I thought I explained the VE tables already. VE = Volumetric Efficiency, which in other words is how efficient your engine is at complete combustion of all incoming air. In your PE tables you have the idle cells in the 70's in your VE table. This means that the PCM will refer to these numbers for is base fueling at idle and then use the MAF and O2 feedback to make any compensations for fueling ( If in OPEN LOOP mode it will not use the O2s). the 70's number you have in the VE tables is telling the PCM that at idle the car is approx. using 70% of the incoming air measured by the MAF for efficient/complete cumbustion. So the PCM only adds enough fuel to maintain the A/F ratio based on the info that only 70% of the air will be used for combustion. If you were t change the VE to 100 at idle, the PCM would add more fuel because it thinks 100% of the air going thru the MAF is being efficiently combusted. In this case you would certainly be too rich.

My car has a huge 260/260 @.50 solid roller and my idle VE tables are around 50-60. Because of the large overlap only 50% or so of hte air entering thru my MAF sensor is being combusted at idle.

I do not know how to better expalin this.

Schurters LT1 - After looking at your Tune your VE tables have been modified greatly from a stock tune. You would probably gain better gas mileage abd part throttle driving by enabling closed loop mode and using the WOT table trick i expalined to you in Email. This way the PCM will ignore the O2s at idle. However you may have to lower your idle VE tables a little. But as I also said your Timing tables are way off for 400-4000 RPMs. I cant imagine how your car runs at part throttle.

I sent you a copy of my tune, mine is a closed loop enabled tune sothe VE tables will be a little different then yours.

TriPinTaZ:confused: i never sent you my tune file :confused: i just went back down to the dyno and Spraytheway helped me well tuned my car , i made power but i did it a$$ backwards he fixed it all up i just would like to know how to do all this:D

Originally posted by TriPinTaZ
well quite frankly, until you have more experience in the area of VE tuning I dont expect you to understand.

Sorry wise one. :rolleyes:
You can explain what a ve table is all that you want and that you modified the hell out of them because you're car is highly modified, but until you tell us what kind of data you're looking at in order to know what kinds of changes to make to the tables then you aren't helping anyone. Tha'ts all I've been trying to get out of you.
But it doesn't seem like you've answered any of the questions I've asked you...so I'm not going to worry about it anymore.
The pcm can calculate part throttle fueling for me and I'll use my "tricks" of playing with the maf tables and injector constant in order to get the long term fuel trims to an area where the pcm is able to adjust by itself. Then if I can't tune wot with the pe tables I guess I'll just be screwed. :rolleyes:

Originally posted by TriPinTaZ
well quite frankly, until you have more experience in the area of VE tuning I dont expect you to understand.

I was looking for information as well, not condescending comment about how I don't understand it. I already stated that I don't fully understand it and that I'm looking for information relative to how it works. Like information that involves the modifications themselves and how they make and effect on the engine's VE. Other things such as timing and how it relates would be nice. Since your not interested in helping, I'll look elsewhere. Thanks for being an ass.

sorry it was blk95ta who sent me his file, not you.

As far as the rest of you calling me an ass and that you dont understand the effects MODs have on the VE of an engine......Well Like I said, I dont expect you to understand and Im not going to write a book about it. Go learn like I did, hands on, research, and HANDS ON in the dyno room.....and a very knowlegable Engine Builder.

I wasnt trying to be an ass, but since you want me to be one I will.

Buzz Off and keep paying people to make you half assed tunes for your cars

:cry: :cry: :cry: :mad:

The problem Taz is that we appear to be dealing with two different definitions of Volumetric Efficiency (VE)..... the "classical" definition, and yours. Not saying you are wrong, but your definition is not what engine builders traditionally mean when they say VE.

VE is in effect the efficieny of the engine's breathing (not necessarily its combustion)... what is the mass of air actually contained in the cylinder, for purposes of combustion, compared to the theoretical volume of the cylinder. If you rotate a stock LT1 crank 2 times, it "displaces" 350 cubic inches of internal cylinder volume. Theoretically, if you filled the cylinders with 100% of the air mass, calculated at MAP and IAT, that would occupy that volume, your VE would be 100%.

But it doesn't necessarily happen that way. The dynamics of the pulsating air flow, including the results of the cam profile will either limit or enhance air flow. In your typical mass produced stock engine, you might only see 80% of the mass of the air actually filling the cylinders. With a well designed high performance engine, you might see 90-95% VE. With an engine that runs in a narrow range of RPM (e.g. NASCAR), with the ability to "tune" intake and exhaust runner frequencies, you can exceed 100% VE. The pressure in the cylinder is actually above atmospheric pressure because of the wave pulses.

Speed-density relies heavilly on VE. It is very easy to calculate the displaced volume as the engine rotates.... basically displacement X rpm/2 (with appropriate "units", of course). And it is very easy to calculate the density of the air available to fill the cylinders, by using the perfect gas law and the absolute pressure (MAP) in the intake, and the absolute temperature (IAT + 460 in the english system) in the intake.

Now you have displaced volume x density = mass air flow.

But that's at 100% VE. The engine doesn't operate at 100% VE, so the designers put it on an engine dyno, and measure the VE under various operating conditions. Now your equeation, for determining mass flow becomes:

displaced volume X density X VE = actual mass air flow.

The fuel sytem now needs to deliver the correct mass of fuel to match the actual mass air flow.

So.... that explains why you need to know VE, in order to properly tune a speed-density setup. And that's the traditional meaning of VE... the ratio of the actual air flow the the displaced volume.

In theory, a "mass air" setup eliminates all of the above..... it directly measures the mass flow of air at any point in time.... doesn't need to know displacement, rpm, MAP, IAT or VE.

But, if the mass-air system is required to default to speed-density when the mass air measurement is lost, it needs to have the VE table available.

You are apparently bringin up a different concept, which someohow relates to "combustion efficiency". And in all honesty, I can't follow what you are saying.... not to say you are wrong.... only that I can not understand your explanation of VE as it relates to mass air. And I think that is why people are having a hard time understanding you.

Look at what you are saying.... the mass-air sensor makes an air flow measurment at idle, and you call that 100%. Then, when that air goes through the engine, only 70% of it is actually "burned", so you are proposing that the PCM needs to know that 70% figure, in order to determine the fuel mass rate. But..... if 100# is entering the intake, and only 70# of it is being burned, where is the other 30# going? You could say, well, that goes out the exhaust, due to overlap, or incomplete combustion. But, the fallecy of that approach is that, unless you have added 100% of the fuel mass to match 100% of the air mass, you don't have enough fuel, because if you aren't burning the entire mixture, and some of the mixture goes out the exhaust, that mixture is not just air... it is an air/fuel mix.

The only exception to this would be the air lost due to overlap. At low load/low rpm, it is possible that only air enters the cylinder volume during the initial stages of the intake stroke, the injector is not firing, so only air is escaping out the open (overlap) exhaust valve, not fuel. In that respect, the concept of VE and mass air would work.

But at higher RPM/higher load, once you drive the injector above 50% duty cycle, you are losing both air and fuel, because the injector is firing well in advance of the intake event.

It is entirely possible GM has some concept of VE and how it relates to mass-air systems. But that would not be the traditional concept of VE. All we are trying to do here is understand what this seemingly new concept of VE is, and how the PCM programming handles it.

I really don't know the answer.... I have no need to know, since I don't even use the stock PCM. But I would like to learn the answer. :)

I was trying to explain what the NUMERICAL input in the VE tables themselves meant to the PCM. Not what the VE reading on the MAP means.:)

Originally posted by TriPinTaZ
Buzz Off and keep paying people to make you half assed tunes for your cars

OK. :rolleyes:
Thanks for answering the questions I asked you. Much appreciated. :)