Idle tuning for larger TB with ETC.

[DrX]

I have installed the 90mm LS2 TB on my Radix. In trying to get it to idle in gear before any learning takes place I have found that B4349(ETC Throttle Area Conversion) is the only parameter that seems to have any effect on this with ETC. From the units, it looks like the PCM multiplies the desired throttle area by this factor in order to determine the required % throttle opening. So for a larger TB you would expect the factor to be lower in order to yield a lower % throttle opening for the same throttle area. Correct?

The value was .0208 for the OEM 78mm TB. According to my calculations, something like .0157 would make sense for the 90mm TB. It turns out though that it actually required a value closer to .0300 in order to run properly! Am I misunderstanding something here?

[Delco]

I have installed the 90mm LS2 TB on my Radix. In trying to get it to idle in gear before any learning takes place I have found that B4349(ETC Throttle Area Conversion) is the only parameter that seems to have any effect on this with ETC. From the units, it looks like the PCM multiplies the desired throttle area by this factor in order to determine the required % throttle opening. So for a larger TB you would expect the factor to be lower in order to yield a lower % throttle opening for the same throttle area. Correct?

The value was .0208 for the OEM 78mm TB. According to my calculations, something like .0157 would make sense for the 90mm TB. It turns out though that it actually required a value closer to .0300 in order to run properly! Am I misunderstanding something here?

What did you have to do to get the LS2 throttle body on , I tried to do it the other day on a car here and rewired the throttle but couldnt get it to work properly at all on our Aust cars.

Kept throwing tps corollation codes

[Doc]

THROTTLE BODY
If you have a bigger throttle body (FAST 90, or Nick Williams) you want to multiply your Effective Airflow Area by 48%. (put in 1.48, select the whole row, hit 'multiply')
or 1.44 (44%) if you go by straight math
You get this # from Circle Area
Pi * Radius Squared
(Pi*45*45)/(Pi * 37.5*37.5)
which = 6361.725123/4417.864669
which = 1.44

90mm area/75mm area

same thing goes for any different size Throttle body
just do the math and scale accordingly

[DrX]

What did you have to do to get the LS2 throttle body on , I tried to do it the other day on a car here and rewired the throttle but couldnt get it to work properly at all on our Aust cars.

Kept throwing tps corollation codes

As recommended on performancetrucks.net, I used GM TAC module # 12574221(shows as for a 2002 Avalanche when I looked it up, but I believe it was used on some other ETC trucks as well). The other significant difference is that the wiring for the dual TPSensors is switched around. Here is a copy of my last post on this topic from performancetrucks.net :


Had to figure out why the high/low ref wires appear to be crossed going into the LS2 TB according to the truck/LS2 wiring diagrams. Didn't make sense unless the TP Sensor signal wires were also switched, which they weren't. So I looked at the operation of the sensors. According to the behaviour of the signals, sensor 1 in our trucks = sensor 2 on the LS2 and vice versa.

Truck:
"The TP sensor is actually 2 individual TP sensors within one housing. Separate signal, low reference, and 5-volt reference circuits are used to connect the TP sensors and the TAC module. The TP sensor 1 signal voltage increases as the throttle opens, from around 1.0 volt at 0 throttle to above 3.5 volts at 100 percent throttle. TP sensor 2 signal voltage decreases as the throttle is opened, from around 3.8 volts at 0 throttle to below 1.0 volt at 100 percent throttle."

LS2:
"There are 2 individual TP sensors within the throttle body assembly. The TP sensors are used to determine the throttle plate angle. The TP sensors provide the ECM with a signal voltage proportional to throttle plate movement. The TP sensor 1 signal voltage at closed throttle is above 4 volts and decreases as the throttle plate is opened. The TP sensor 2 signal voltage at closed throttle is below 1 volt and increases as the throttle plate is opened."

So for anyone doing their own wiring or checking an install, this is how the OEM wire colours should match up to the LS2 connector as shown above(this was accomplished in my application by simply plugging in the Speartech adapter harness ):

Black OR Black/White(C) Yellow(B) Brown(A)

Purple(F) Light Blue OR Grey(E) Green(D)

An alternate arrangement that theoretically should also work would be to keep the high/low reference wires as per the OEM wiring and switch the Green and Purple TPS signal wires. This would look like:

Light Blue OR Grey(C) Yellow(B) Brown(A)

Green(F) Black OR Black/White(E) Purple(D)

[DrX]

THROTTLE BODY
put in 1.48, select the whole row, hit 'multiply'


Which table are you referring to? I tried modifying the B4403(IAC Effective area table) -the values would have to be decreased/shifted down for a larger TB. Tried all kinds of changes to this table. This didn't seem to have any effect with my ETC setup. Not sure if any of the IAC stuff is relevant. Logging the GM.IAC PID always shows the park position and there is no actual IAC motor as on cable style TBs.

The value of B4349 seems to be all that is required for effective area calculations with respect to throttle opening. But it seems backwards to increase rather than decrease it according to the units. Or perhaps I am just looking at it from the wrong hemisphere.:nixweiss:

[jfpilla]

DRX,
You're correct. ETC is the value to change. As you said lowering it reduces airflow and raising it increases airflow. If you're not cammed I'm surprised it doesn't idle fairly well without changes. No leaks?
If your IFR's, VE's and MAF are correct then when you log Dynair gms and IACDES gms they should be close. Raising ETC lowers IACDES and viceversa. Lowering IACDES tells the PCM that less air is coming in (or more fuel if you lowered IFR's) so it opens the blade and the opposite. You may then need to set IDLE/DESIRED AIRFLOW. When that's right you may also need to use STARTUP FRICTION AIRFLOW to get the startup RPM's where you like them.
Joe

[DrX]

DRX,
You're correct. ETC is the value to change. As you said lowering it reduces airflow and raising it increases airflow. If you're not cammed I'm surprised it doesn't idle fairly well without changes. No leaks?
If your IFR's, VE's and MAF are correct then when you log Dynair gms and IACDES gms they should be close. Raising ETC lowers IACDES and viceversa. Lowering IACDES tells the PCM that less air is coming in (or more fuel if you lowered IFR's) so it opens the blade and the opposite. You may then need to set IDLE/DESIRED AIRFLOW. When that's right you may also need to use STARTUP FRICTION AIRFLOW to get the startup RPM's where you like them.
Joe

So, then I actually should be decreasing B4349 to compensate for the larger TB as I had thought. Since I had to increase it, something else must be messed up. It started up and idled OK in P/N before I changed anything. But would shake, rattle and stall if I shifted into gear. If I waited for it to warm up to learn enable ECT(80*C), I could get it to learn and recover. Don't want to have to do that after every reflash. I changed everything at the same time-trans and converter, TB, and fuel system, new intake gaskets. I would think that a leak would cause a lean idle condition causing me to have to close the throttle with B4349 rather than open it. AFR is looking good at part and WOT. Seems to run great other than the idle in gear issue. No MAF.

[jfpilla]

DRX,
I only pointed out the affect of the changes. I don't know enough about your car and tune to be sure of whether you need to go up or down. I did know you are mafless. I slipped, but it's the reason I indicated Dynair and Iacdes should be close. This is more important than thought and helps keep the tune from changing when done right. You will probably have to find the ETC value by trial and error. Fortunately there are not to many possibilities and EFI is fast.

[Doc]

Jfpilla,
Thanks for the explanation. I hope I didn't mess anybody up. I just felt that first cup of coffee and threw my hand up in the air as fast as I could.

[DrX]

I appreciate everyones input. Helps get the gears turning. Never know what is going to set off a Eureka! moment.

[DrX]

I played around with B4349 a little and arrived at a value of .0135(makes sense because it was lower than the .0208 for the 78mm TB) where Desired Idle Airflow matched Calculated Airflow in Park(TP 2%). They didn't match in gear though(TP 5%). I increased the value to .0140 and modified the VE table a little in the idle cells using AutoVE until they matched both in Park and in gear. Seemed to work OK. Nice smooth shift into and out of gear, idled smoothly in both P and in gear. Until I started it up cold the next morning...wouldn't even idle in Park??

[DrX]

Excuse me...it was another value that wouldn't idle in P or gear. With B4349 at .0140 it would idle in P but not in gear when cold. Seemed OK under most other conditions.

[jfpilla]

Excuse me...it was another value that wouldn't idle in P or gear. With B4349 at .0140 it would idle in P but not in gear when cold. Seemed OK under most other conditions.

Try reducing VE's from 1200rpms and under by 5% at a time. When it's idling and you turn the A/C on and off is there any stumble and does the above correct both either or both?

[DrX]

I haven't noticed anything other than a "thump" when the AC clutch engages at idle but that started before the TB mod. Not sure what is causing it. No stumble. I adjusted the VE table by -5% as you suggested. Will see what happens when I start it up cold in the morning.

[DrX]

Decreased the VE by 8% and increased B4349 to .0157 where the basic math says it should be for the 90mm TB. A/C still has no effect. Seems to idle not bad in Park or gear this way but of course it lean(BEN=1.13 at idle).

[jfpilla]

Decreased the VE by 8% and increased B4349 to .0157 where the basic math says it should be for the 90mm TB. A/C still has no effect. Seems to idle not bad in Park or gear this way but of course it lean(BEN=1.13 at idle).



Check the IACDES and DYNAIR values.
What are they?

[DrX]

Check the IACDES and DYNAIR values.
What are they?

Of course it varies with ECT and time from startup, but this is a good example of what I am seeing right now:

IACDesir 6.00(Park) 8.90(Gear)

Dynair 6.50(Park) 8.90(Gear)

Immediately after the reflash Park was 6.0 and 6.0. Haven't done anything but gone for drive since then. Looks even more lean now-up to 18 AFR! It was at 16 a half hour ago??

[jfpilla]

I played around with B4349 a little and arrived at a value of .0135(makes sense because it was lower than the .0208 for the 78mm TB) where Desired Idle Airflow matched Calculated Airflow in Park(TP 2%). They didn't match in gear though(TP 5%). I increased the value to .0140 and modified the VE table a little in the idle cells using AutoVE until they matched both in Park and in gear. Seemed to work OK. Nice smooth shift into and out of gear, idled smoothly in both P and in gear. Until I started it up cold the next morning...wouldn't even idle in Park??

When you were at this point it sounds like everything worked well except cold startup idle. Did you try raising Desired Aiflow(B4307) at cold temps?
If not, try the tune that was in and raise DAF.

[DrX]

When you were at this point it sounds like everything worked well except cold startup idle. Did you try raising Desired Aiflow(B4307) at cold temps?
If not, try the tune that was in and raise DAF.

Actually, it worked OK except for pre-learn idle in gear. I may have already tried adjusting B4307. I will try again just adjusting the cold/in gear portion of it. Not sure why the desired airflow would have to be changed except to compensate for error in the calibration of the TB. And in that case airflow should be off in both Park and in gear. I have not changed any engine internals so shouldn't its idle airflow requirements remain the same? Would the new converter affect in-gear idle in any way?

[jfpilla]

That was my point in post #6.

[DrX]

I rebuilt the VE tables manually starting from the tune supplied with the Radix kit and leaving the idle portion untouched. I also set B4349 to .0157 in accordance with the difference in areas between the 78 and 90mm TBs. Started it up cold today and it idled OK both in Park and in Gear! I think the AutoVE is messing up my tables.

At idle, in park, after a drive, IAT = 24*C: my AFR was 14.35. Commanded was at 14.68(I have it set to 14.63 in the tune??). But BEN for these cells is 1.02 rather than the expected .98
So I looked back at the beginning of the log which was after a little heat soak(IAT = 41*C). There logged idle AFR was 15.0, so BEN would be 1.02. MY IAT VE Multipliers in this range were all set to a value of 1(no correction). Just logging a cold start(today IAT was 5*C at first startup) would likely yield a different result yet again. The resultant BEN factor seems to vary significantly depending on how much logging time is spent at various IATs. Here, on a single logging run it seemed to lean out as IAT increases and vice versa(seems backward).

[jfpilla]

I can't help much with Auto VE. There are others on this Forum who do a lot of it. I set my VE's. I don't get crazy. I hook up the MAF and it runs great.
I don't know why IAT should mess up a tune to where it affects startup?

[Chris81]

So, I guess this goes against using .0320 for 90 mm TB's..

Let me make sure I'm hearing this right, does a smaller number in B4349 result in the TB opening MORE instead of LESS?

I'm just trying to get this straight because it is probably why I can't get this stroker Vette to drive right! lol

[jfpilla]

Not enough people have been doing it long enough to know what values are right. If the 90mm was the only change then lowering would likely be correct. But you have a cam and you need more air at idle and what other tables have been adjusted? Suggest you try different values and see what works. If all your tables are correct then IACDES should be close to MAFgms/DYNAIR.

[Chris81]

Yea, i've tryed .0320 and it doesn't seem to be working well at all.. so i'm going to go back stock and watch my values and most likely reduce, I need to rerun the RAFIG as well. Its good info to know though at far as the reduction method seems to make sense.. i've seen alot of people increase but not many decrease..although, there was a guy on LS1tech with a stout H/C with a BIG cam (250ish duration) that had good luck reducing this table I believe.

I'll try it and update with my findings.

The car has a FAST 90, LS2 TB, big cam (240/244)..etc..

[jfpilla]

Chris81,
I've been playing with Inj.Offset and with most tables stock my ETC is 307 and I think it will end up 310. I'm not saying it's right. It's just how it is with this method.
Joe

Engine Calibration.Idle.General
{B4350} Maximum Desired Idle Area, changed from "84.0" to "90.0".
Engine Calibration.Idle.General
{B4349} ETC Throttle Area Conversion, changed to "0.0307"
Engine Calibration.Fuel.Injectors
{B4001} Injector Flow Rate. Calibrated
Engine Calibration.Idle.Start-up
{B4344} Startup Friction Airflow Decay.
Engine Calibration.Idle.General
{B4307} Desired Airflow. stock Z06
{B4308} Airflow Parked. stock Z06
Engine Calibration.MAF
{B5001} MAF Sensor Calibration, stock Z06
Engine Calibration.Fuel.Injectors
{B3701} Injector Pulse Width Voltage Adjustment, modified.

[DrX]

So, I guess this goes against using .0320 for 90 mm TB's..

Let me make sure I'm hearing this right, does a smaller number in B4349 result in the TB opening MORE instead of LESS?

I'm just trying to get this straight because it is probably why I can't get this stroker Vette to drive right! lol

My understanding is that B4349 justs allows the PCM to convert throttle area to % throttle opening for idle on ETC vehicles.

For example, if desired idle throttle area is 80 sq mm:
80 x .0320=2.56% throttle position
80 X .0160=1.28%
So a smaller number = less throttle opening for ETControlled idle airflow when learning is not active. Under non-idle conditions TP is determined by pedal position.

As I am running in SD, my VE values also affect the correlation between desired and calculated idle airflow. Decreasing the VE value at a given MAP/RPM has the same effect as decreasing B4349 and vice versa. I had to adjust the VE table in the cells corresponding to both park and in gear idle in order to get des and calc airflow to match under both conditions.

My problem seemed to be obtaining accurate VE values for idle as AFR at idle varies significantly with IAT. For example, today the ambient air was 5*C so this would be my IAT at startup. After driving for a while I idled for about 20 minutes and watched my IAT rise to 42*C due to heat soak of the intake. While driving my idle AFR was about 14.7 but by 42*C IAT it was up to 15.5 or higher. This was with a +4% VE multiplier(COS3) kicking in at 40*C IAT.

Not sure if .0157 is the ideal value for B4349. I just used it because it is directly proportional to the difference in the cross sectional areas of the 78 vs 90 mm TBs. A simple calculation in this case because both TBs have a constant radius for their full circumference. I am pretty sure that there is only 1 "correct" value for B4349 for a given TB. I would would like to know what this value is set to on the LS2 cars using the same TB. If more idle airflow is required other tables should be changed as described by jfpilla. Of course you can cheat on B4349 like some do with IFR or alter it temporarily to get an idea which way you have to go with your other tables.

[Chris81]

Chris81,
I've been playing with Inj.Offset and with most tables stock my ETC is 307 and I think it will end up 310. I'm not saying it's right. It's just how it is with this method.
Joe

Engine Calibration.Idle.General
{B4350} Maximum Desired Idle Area, changed from "84.0" to "90.0".
Engine Calibration.Idle.General
{B4349} ETC Throttle Area Conversion, changed to "0.0307"
Engine Calibration.Fuel.Injectors
{B4001} Injector Flow Rate. Calibrated
Engine Calibration.Idle.Start-up
{B4344} Startup Friction Airflow Decay.
Engine Calibration.Idle.General
{B4307} Desired Airflow. stock Z06
{B4308} Airflow Parked. stock Z06
Engine Calibration.MAF
{B5001} MAF Sensor Calibration, stock Z06
Engine Calibration.Fuel.Injectors
{B3701} Injector Pulse Width Voltage Adjustment, modified.




Could I check out a copy of your tune file to compare?? That would help out alot! I'll be doing some more tuning this week on the car.

cspears6@gmail.com