OK, this might be a little long.

The car is a 98' Z28, A4, 3.23. It has probably all the bolts ons, and a 232/238 112 LSA cam. The MAF is completely stock to the screen as well as stock injectors. Right now I have a 3400 2.5 converter, but a PT4000 is on the way.

Anyway, the car idles pretty good, and drives well. I finally got the LTFT's down some by reducing the IFR table by 4% (96%). This is really the only change besides things to help the idle. Stock timing tables, and stock PE Vs RPM tables. Stock VE tables too.

I have tried reading the Fuel vs. VE thread on here, but its over my head right now. I need this stuff in everyday terms. Searching hasn't provided any real info, as alot of it cotradicts other threads. I just need to get a basic understanding of these things

Does the PCM take into account the PE Vs RPM tables all the time, or only during WOT? If all the time, couldn't I adjust through the RPM range here to try to fix the KR? If so, which way to adjust? Add fuel, or reduce fuel?

First problem is that I am experiencing KR, basically all through the RPM range. Under load, I only have KR from about 1000 RPMs to roughly 3500. The maximum amount on this last log I did was 3.9* (It's a 98,and I have read about the 3.9* on 98's, but before the recent round of mods, I didnt really have a problem with KR). Does the KR in the lower RPM's really matter that much? Could I just lower the sensitivity in those RPM ranges? Would reducing the timing in these ranges help? If so, when people talk about reducing the timing, what table are they editing it in? It seems like I have 6 timing tables or so...So what should I change, and which way should I change it?

Second problem is that from what I see in the loggings at WOT in cell 22, I am getting slightly negative, -.4 to -.6 LTFT readings. I thought these were supposed to zero out. Cell 15 is getting slightly positive LTFT readings, 1.5-2.2. Is this OK? My O2 readings at WOT seem to be all over the place?

I understand how to calculate the g/cyl= MAF g/s * 15/RPM, but what do I learn from this value? Its the c/cyl measurement, so would I just take the calculated g/cyl, and the RPM I used to get it, and reduce the timing there? How should I pinpoint where the timing should be taken out according to KR?

I have the ATAP files if anyone cares to see them...

I am sorry this is so long guys...but I have to learn it somewhere...

Thanks
Joe

 

The VE tuning is basically math. You just need to use the equation that ChrisB posted.

Drive around logging MAF, MAP, IAT, and RPM. Enter the values into the below equation on a spreadsheet.

'MAFFlow in units of grams/second
'RPM as Revolutions Per Minute
'Displacement in units of Cubic Inches
'MAP in units of KiloPascals
'Temp in units of Degrees Centigrade

VE = MAFFlow * (Temp + 273.15) / (Displacement * RPM * MAP) * 212544 * 30

Use the resulant value to start building a VE table. Corrolate the resulting VE value with the corrosponding MAP and RPM.



The PE table is only used by the PCM when the throttle conditions and MAP conditions posted under the PE table are met.

You have the 98 KR problem. Richening your car is not going to help. You are going to have to do the KR sensor fix, or disable your KR.

Don't worry about the slightly negative LTerms. As long as they are freezing at near zero values you are fine.


To alter your timing table correctly you have to calculate out the g/cyl using the equation that you posted above. You then take this g/cyl value and the corrosponding RPM value that you entered into the equation and alter timing at that point.

To change timing at those points in which you are seeing KR, use the corrosponding MAF, and RPM that you recorded at that point in the equation. This will give you the g/cyl and the RPM that you need to reduce timing at on your timing table.

However, as I said earlier, you have the 98 knock problem.

Good Luck

 

NoGo should write a Tuning book. Seriously. Kind of like a "Tuning for Idiots/Dummies" book. That's it NoGo's LS1 Tuning for Dummies. Could be extra CA$H for the Racecar.
NoGo- you are a natural at simplifyng and teaching.
You could sell it online, like Harlan does.
It would be nice to have the info in a bound book. Hell, I've got printed material from "scan and tune" section all over the dining room!!
joel

 

I've got supercharger books, race suspension, and tuning junk all over my living room. My wife is about ready to kill me......

I wouldn't mind getting together and writing a tuning book with some of the minds in the business......

 

Sweet...thanks. I am going to do a log tomorrow morning and see what I can come up with. So any changes that I will make should be made in the Main VE table, right? What arethe Crank VE, and secondary VE for?

I have heard about the 98 problem with knock. Isn't there a new style sensor that I can replace my old ones with...?

Thank you so much for explaining that, I think I understand it pretty well. We will see. I'll update my situation tomorrow and let ya know what I get...

 

Obe other thing, will I basically end up calculating a whole new VE table? Or should I mostly be worried where I go WOT at?

 

WOT is actually where it will probably help you the least - there you can tune just as well with the PE vs RPM table. I would try to get as many data points as possible in as varied a range of driving positions as possible (definitely include some WOT, just don't focus on it exclusively) - you will still probably end up with portions of the table without data, there you will have to just fit the data in as best you can.

 

ChrisB is right about the VE table. Several sections of the VE table you will have to "interpolate" to get a good value.

 

ok, let me run this example by you guys. These are some values I got on my way to work this morning...

MAF in g/sec = 103.09
RPM's = 3573
Displacement = .2 (I got this number out of another thread, is it right for a stock cubed motor?)
MAP in KP = 63
TEMP in celcius = 22

So:

103.09 * (22+273.15)/(.2*3573*63) * 212544 * 30

that gave me 4309486.8

I remember reading somewhere that the LS1 Edit values were different, and to divide by 3000, so:

4309486.8 / 3000 = 1436.4956

So now i should take 1436, and insert it into the Main VE table in the appropriate column/row? Since there is not an exact RPM cell for 3573, should I just change the 2 columns closest to that?, same with the MAP? I should use MAP 60 and 65

My stock values look like this

MAP 3200 3600 4000

60 1798 1906 1981

65 1818 1921 1997

So....how's this look for just the first calculation?

 

look for the bolded corrections

 

Quick question. I see IAT is used wouldnt this skew the tables say if yuo logged VE on a cool day and you IAT was 0* C as opposed to a day where your IAT is 33*C. Could a constant ECT (because of themrmostat) be used instead since the engine is within a 5-10* spread

 

Actually having IAT in the calculation would prevent it from being skewed.

 

OK, so displacement is for the whole motor, not just per cylinder..?

so using 347 in the above equation instead of .2 would make my VE = 2431.92...?

Doesnt that seem a little high for the area I am working on?

 

That is awfully high for that MAP and RPM.

 

Thats what I thought? So displacement is supposed to be 347, right? I made a spread sheet to figure the formuala up for me, and everything seems to be coming out way high...this is using the 347 figure, using the .2 figure, everything seemed a little better....???

 

I guess it depends on if we are supposed to be calculating the displacement in cubic feet, or cubic inches. Cubic inches would be 346 or 347, but since 1 cubic foot = 1728 cubic inches, then that would give the .2 I was talking about. So as soon as I find out which way to calculate the displacement, I should be good to go for the calculations...then its on to the changes....

 

I just looked at a couple logs that I have an each one of them cam up at ~65%, ~1950 LS1 Edit (thats averaging ~20 points a piece at 60 kpa and 3500 rpm). Yes, I did have some funky points that came in with off values (one was 250 VE).

Getting a VE table is tricky. You have to do alot of averaging and proper data selection. It also helps to be driving at a steady state condition. All of my VE determinations are done with freeway driving.

Good Luck

 

I go through a filter out all values where tps = 0 and deltaVSS is negative (coasting down), and where the car isn't up to temp yet to start off.

I also kill off the values for each cell were the population < 50 (number of samples). I then filter out all values that are more than 2 standard deviation units from the average.

Generally that gets me a table that tracks pretty well with what you would expect - the biggest problem is getting enough data points to make it statistically valid - you are going to want a tremendous amount of data, and you need to make sure that you vary your driving quite a bit to try and hit all the cells.

 

ok, so maybe log for a complete week straight doing all kinds of driving, and try to build a table from there? Will do.

So I am still confused on whether .2 cubic feet, or 346 cubic inches should be used as the displacement constant?

Is it possible to mess things up really bad, mecahnical wise, by playing with the VE? I just dont want to adjust too much accidentally. If someone could look at my VE table after I get it built, that would be great....

 

Sorry I mean to type 346 for the displacement. Look at this thread for a in depth discussion and a breakdown of the formula


https://ls1tech.com/threads/showflat...=7&amp;fpart=1