Replied.....

 

To adress in order.



SSpdDmon
My IFR values were set for my 30lb SVO's using an injector spreadsheet with a 3-bar to 4-bar pressure conversion


Yeah these don't really flow the way the spread sheet would show them to.they have an Odd Gain curve. I will see If i can find the flow test data that was done some time ago at an actuall lab.




SSpdDmon
As I mentioned, fuel was flooding the engine on warm starts. This wasn't an airflow issue.



Sure sounds like an Airflow adjustment issue. Either that or your Scalar values were inccorect for compensation for engine tempature vs cranking.You may have needed a larger IAC Offset and park position setting. fairly common on cammed engines. they pull less vacum so you need larger Base cranking settings for airflow.




SSpdDmon
Yes, dialed in with +/- 0.2 grams per second according to the idle trims



Did you disable the adaptive idle control pids ? they monkey around with idle when you are running with a MAF.



SSpdDmon
Why would I touch this? It's a driveability table that has no effect on fueling.

Yeah it can impact fueling. If you have large map swings,stuff you can't log becuase they happen far faster then the data framming, it can monkey with fueling by disrupting the map. The buck and surge and trailer hitch will cuase fueling swings as the IAC and Idler spark adder try to control the decel and coast throttle. The PCM will jump in and out of Accel Enrich Mode.



SSpdDmon
Somewhat. I was mainly focused on dialing in steady state throttle. Logs were filtered to eliminate transitions so that they wouldn't skew the data.



Ve has nill to no effect on fueling outside of this. If the car was stumbling or hesistating on TIP and large throttle application the VE table values were incorrect.



SSpdDmon
A stock MAF table was used with a screened SLP MAF.

That pretty much rules out ducting issues.



SSpdDmon
It's only a 232/238 .595/.605 112 cam.


No need to SD that vehicle. easily could be done with the MAF intact and good fuel control.

 

No offense, but I respectfully disagree with that method of tuning for the reasons stated in my prior posts. I feel I can say I gave it an honest try. Part of my issue with it may be my ignorance to all the bits of knowledge you have up your sleeve to cure certain issues. However, based on my knowledge of the tables available to edit, how they work, why they exist, and how they interact with the other tables, it just doesn't make sense to me to do it your way.

I know the car doesn't need to be in SD. It is because it runs a little better at idle that way along with the fact that I like futzing with it. I could turn the MAF back on and deal with the idle reversion, but I choose not to. My AFR is running a little rich while I finish dialing it in (even more so in decel due to the SVO's). But considering I'm commanding 15:1 at idle & cruise along with 12.6~13.0:1 at WOT, I'd say this tune is pretty close (a lot closer than what I could get using your way)....and I don't have any hot start issues or any sluggishness.

Attached: Log from luch time cruise to McD's where IAT's ranged from mid-90's to mid-120's.

 

There is no SD mode to use. Essentially what you are doing is forcing the PCM into that mode VIa fualt. The software wasn't written to operate that way. There are tons of things you need to know about how all of the calibration parameters interact to really make a car idle well.

why are you running that engine so rich ? why not feed it some spark ?

Yes there are a ton of tricks. Alot of which are hard earned secrets. I have set you on the road however. The rest is up to you.

Enjoy.23112

 

alright guys, something here is not working for me. I now have my MAF Calibration down a great deal ( it maxes out at like 139 at 12000) I looked at my stock tune and the 12000 mark was still around the 400s. What is messing with this that is not allowing me to get my MAF ERR right?

I am in OL withthe MAF on (14000 hz) My stft's are cycleing though, should those be not moving when I am trying to dial this in?

Someone please help me with this, its getting frustrating.

TIA

 

Because it likes it that rich. As soon as I hit 16:1, idle starts to break up. My experience is a cam of this nature doesn't like nor need more spark. In fact, it likes less. I'm idling a hair above stock idle timing. Keeping timing that low has eliminated virtually all of my bucking/surging during decel (without DFCO enabled). This car drives so smooth....well, you can read my sig. When I got it, a pro tuned it using your method with those hard earned 'secrets' and it was no where near as smooth/crisp/consistent as it is now.

What I don't understand is why people say, "The PCM wasn't designed to operate this way." The '93s operated this way, didn't they? Not by fault, but they were SD cars, right? I don't recall them having a MAF sensor. Why is there a commanded AFR at all if it wasn't designed to work this way? Why would the PCM know what stoich is (or at least have a cell to be told what stoich is)? The fact is, the PCM wasn't designed to operate either way. It was designed to operate a stock car in closed loop, MAF mode. One way or another, we need to change the parameters to get it to run right. Whether we use a MAF or don't use a MAF, fudge the commanded AFR's or change the VE, we're still going for the same result. I just feel that my way is a little more consistent once it's said & done and it's evident in the pic I attached in my last post (average variance of less than a half point AFR). After all, it's still AIR/FUEL/SPARK that we're manipulating. But, that's just my $0.02.

EDIT** Another thing...aftermarket heads/cams are designed to get more air into the engine and into the cylinders. More air means more fuel and with the right timing, more power, right? Using my way, grams/cylinder (as read by the PCM) increased from low .70's to high .80's. That equates to roughly a 25% increase in airflow. I make ~430hp to the tire. Bolt-on LS1's with my mods usually make ~340's. 345*1.25= 431.25...coincidence??? Using your way, gram/cylinder calculations don't change becasue the MAF values are left stock. I just think that's a little odd for a motor breathing much better...

 

If you're in open loop, there should be no LTFT's or STFT's. %Error is a simple calculation. It's what you see on the WB divided by what you're commanding. Starting with a stock or slightly guess-timated MAF curve, you multiply that percent error to the MAF table (or 50% of it when trying to fine tune). Rinse and repeat. If you're down in the 130 grams/sec range at 12,000Hz, something is seriously wrong with what you're doing. How are you logging this?

 

Depends on the pro doing the tunning. Not all pro's are equally trained and or knowledgeable.Timming was the Right way to fix it. Not tweaking the throttle cracker settings will make a car buck and surge and leaving on the Idle adaptives will definately make it even worse.

Having been through the actual source code I can say with certianty that in fact the PCM is not designed to operate in SD mode.

92-93 pcms we far different animals then 94/95 and 96/97 and even 97/98 and 99-up boxs. differing hardware software and strategy for implementation are keys here.

92-93 PCMs are dedicated Sd systems. but they are based on older pre 92 systems like $8d 1227730 systems. they had true SD algorythms.

94/95 pcms had dual mode operating systems with Ve tables that were based on an Actuall Airflow algorythm. That calculation used Ideal Gas Law principals to determine Injector PW.

96/97 lt1 PCMs were a shift towards the 8 bit Airflow model and had 2 proccesor cores based on the 68hc11. The airflow modeling did not follow Ideal gas law but more of a Map volume differential model for figuring in for TB deltas.

97-up ls1 box had 2 variations. the first boxs were dual proccesor 68hc11 subvariants. they had similar coding but half the processing power of the later 99 up pcms which fell back to a more common 68332 32/16 bit acrhitecture.

Bear in mind they went to a dynamic airflow handling mode for Transients based looslely on the airflow modeling implemented in the later lt1 systems.

Your VE values are based on MAF 97-up ls1 . In fact the root of the Equation is K which is the airflow term derived from the MAF calibration table. K is the root of the running VE table when not in failrue mode. Think of the Ve table as a modifier upon which

ETC IAT term "K" and Injector size and a airmass calculation and wall wetting calculation are applied to. this adds up to Dyna Air. This is essentially what is used for final PW calculations. It is also used in the grm/Cyl calculations that are derived for load.

K is important. By removing K from the system you break alot of other stuff in the process. Most imortantly the base algorythms.

that however is not to say that there isn't a substitue K value becuase there is. K becomes Assumed in the event of a MAF failure and is inffered from a DTC diagnostic Table. It inffers a given airflow rate in the event of a MAF fialure based on TPS and RPM. similar to alpha N. It also shuts down numerous adaptive functions..

that would be your Ecpected Airflow VS TPS table found in your Diagnostic Tables area. Crank that way up and see what happens to your Sd cal then.

 

When talking about coolant and intake temperatures, wouldn't it be logical that a value "K" represents degrees Kelvin??? Isn't an accurate airflow representation (grams*Kelvin)/kPa when other constants like volume are known?? That's air mass, temperature and pressure right there. Those are the units my VE table shows.

Granted the technical side of the automotive PCM is over my head with what the engineers were trying to do. However, I still have yet to see anything solid that says, "THIS IS RIGHT...I CAN PROVE IT TO YOU....HERE'S THE PROOF." If we're talking science, that's the way things become accepted...through peer review. If nobody wants to share...it'll be hard for 'opinions' to be accepted as facts. Then, population doesn't learn...

The only airflow (actually airmass) vs. tps% table that my software shows in the diagnostic section has to do with ETC cars (ETC Predicted Airflow). The DTC it trips is disabled from the factory. There are Upper/Lower TP% diagnostic tables that expect a certain TP% for a given RPM and a MAF Rationality table that makes sure calc'd MAP airflow is relatively close to MAF calc'd airflow. But, that's about it...

 

In the GM source Code the K is the airflow term used in this family of PCMs.




I could easily prove it but why give every software company acess to that info ?It was hard to come by and should not be shared.

Its a shame that so many tables are missing from the currently avaiable software.

 

I think that the PCM will go to a back-up mode if the maf is disconnected. In this back-up mode fueling is based on the the VE table. If the VE table is changed to have 0 ltft and stft factors then this table is correct. If the engine is not in PE mode the A/F ratio should be 14.7. If in PE the A/F ratio should be what is set from the PE table. This will give good preformance with fast changes.

The maf should be enabled. Once that is done the MAF cal table should be changed. Due to the fact that the intake air flow has changed and the cal table is not set to each MAF it is close but can be made better. If the engine is not in PE mode the A/F ratio should be 14.7. If in PE the A/F ratio should be what is set from the PE table. This will give good preformance with fast changes.

If the engine is not in PE mode the NBO2 can be used with the STFT to tune.

Why is a WBO2 not accurate? It may give a average of the actual A/F ratio but if it samples fast this will still be very close. That is why there used.

 

Your leaving a good part of the actual airflow behavoir off the table. The camshafts overlap cycle will play havoc with the WB readings due to waste oygen.

 

Curious, would you agree with this statement?

The air mass per cylinder can be determined from the VE table using the following formula:
g/cyl = VE*MAP/charge temperature
Ve is in g*K/kPa,
MAP is in kPa,
charge temperature is in degrees Kelvin.

Where is the "waste O2" coming from? Since the cylinder is at a positive pressure on the exhaust stroke, any overlap between the intake and exhaust valves would tend to have the exhaust exit via the intake since it's at a negative pressure relative to atmospheric. In fact, this is what causes reversion at low engine speeds, correct?

 

Hey LS1

How the throttle pedal calibrated. I think that it changes from start. Do u know how it works?

 

No more like this

K*"Ve Table rpm vs Map"/ Factor= Final PW.

This is a very simplified Exsperssion of the equation in Use.

K would be Maf Input

 

Most of the ETC calibration is actually in the ETC control Unit. You can however tweak the Size of the TB and All of its coeffieicnets for Ideling and starting behavoirs. Warning if you play here small changes have a huge impact. there is also a declaration table for Relative IAC counts vs Airflow through the IAC. Essentially the ETC software in the Control Unit is on a Class 2 serial Communication Line. The PCM sends out Info over this Class 2 line in Serial format to the ETC module. It then decodes that information into throttle movement data. But you can lie to it.

 

you guys really need to look in the advanced section under 'complex math' thread, there's a lot of info there.

the main idea is that your resulting AFR is going to be a result of VE, MAP, TEMPS, IFR and IPW. VE and TEMPS and IFR are highly nonlinear functions, start mulitplying them together and you have a nonlinear hell. so replacing tuning all this stuff with just IFR or just VE is just silly, because it will never cover all the cases needed to run properly. that's why VE just doesn't converge for a lot of people.

i'm working on a model where we'll be able to tune all these things at the same time. it's not going to be perfect, but it's gonna be better than what we've seen using the AFR% corrections.

 

I could see the last sentence being true to pree 2001 systems but what then takes over for the "Real VE table" GM deleted with 2001 OS's.

If I'm reading correctly, the VE should not be touched even with a H/C car. Tune it elsewhere because the VE table won't help you. It wasn't made to be changed. Not saying you are wrong. Believe me, I'm still a novoice but call things as I see them.

[IMG][/IMG]
Base 2002 Vette stock VE Table

[IMG][/IMG]

2002 Z06 stock VE table.

Why did GM change the VE table to tune the Z06 if this is where you are not supposed to tune? Larger cam = changed VE table.

 

If I'm interpreting this correctly, this is why we tune the VE first and then the MAF. From what I understand, there's a VE calculated airflow value and a MAF calculated airflow value. Below 4,000rpm (or whatever value you set B0120 to), these are blended together with the factor you mention. EFI Live describes it as follows:
By killing the MAF at first, we eliminate the MAF's influence and re-map the VE table's values (listed in grams*kelvin/kpa....not a VE%). Once those numbers are established, we re-enable the MAF with the assumption that the VE is now correct. Personally, I drop B0120 to a low value so that the VE blending factor doesn't interfere. Then, I can dial in the MAF.

Like I mentioned before, my experience shows fueling most definitely varies with RPM (rich down low and lean up top). Why wouldn't two of the main infuential factors like VE and MAF need to change accordingly? The airflow characteristics are nowhere near the same when you throw on headers, heads and a cam. It just doesn't add up for me.

 

Back up VE table???

New screen name?

Been around these parts before...as somebody else?