marballfire

iTrader: (1)

Hey guys. I've been e-mailing back and forth with Bob attempting to resolve this issue, but haven't been able to yet. Here's the problem:

During decel, at about 20 MAP and in the neighborhood of 1000 RPM, my car starts bucking. I have tried richening up the VE tables in that area without much luck, as well as increasing the injector correction offset. I have open loop decel set, so it shouldn't be due to prop gains. I'm not really sure what else might help here. BTW the car is a 5-speed, and the problem didn't exist when i ran the stock computer, so I don't believe its a mechanical issue.

Any help is greatly appreciated

Dominic Sorresso

Try lowering and smoothing SA table in that area? Using Closed Throttle SA.

marballfire

iTrader: (1)

Tried lowering SA in the main table, EBL doesn't have closed throttle SA. That didn't seem to help. I use Open loop Decel, so Prop gains shouldn't be a problem. I've zero'd out the async transition table, as Bob recommended and also tried adding VE in the low map areas. Not sure what to try next...

Ronny

iTrader: (1)

There is a setting MPH vs OL or MPH to allow CL or something to that effect. It is a "constant" for MPH. IOW you can idle OL and run OL up to a certain MPH. I have mine set at 15 mph. It may be "OL idle". I dont have my lappy with me or would give you specifics. Running a bit rich in OL at low speeds may help. You may want to entrichen the OL A/F vs VAC/RPM in those cells you experience bucking.

marballfire

iTrader: (1)

It doesn't seem to be related to speed as much as rpm. I can feel it up through 3rd gear, it is just more obvious in 1 and 2. It tends to come in under 2000 RPM. I'll try enrichening the commanded AFR in the low vac, sub 2k RPM areas. Unfortunately the weather up here has greatly restricted my ability to test changes.

Ronny

iTrader: (1)

As Dom stated lower the SA i bit more.

This may be what is needed as well.

marballfire

iTrader: (1)

I'll look into all this stuff and post back again once I've gotten a chance to drive the car again...3" of snow/sleet expected tonight...

Ronny

iTrader: (1)

Are you by chance using higher fuel pressure or large injectors?

Low pulse widths of injector at low RPM low MAP may necessitate a change in inj offset.

see this thread:

https://www.thirdgen.org/forums/diy-...or-offset.html

marballfire

iTrader: (1)

What would be a good starting point for increasing the injector correction offset by? Engine is a LO5, RV Morse 350 TBI unit, 61# injectors at 15 psi. Engine is stock apart from an open air cleaner.

Edit: I know the engine does have a mild camshaft, but I don't know the specs on it unfortunately.

marballfire

iTrader: (1)

Don't know if this will help any, but here is a screen shot of my SA table, Injector Correction Offset, and Open Loop AFR table. The bucking ONLY happens on deceleration (0% TPS) in the 20 MAP area under 2000 RPMs.

Dominic Sorresso

Sorry but I recall EBL having Closed Throttle SA.

marballfire

iTrader: (1)

Not that I can find...These are all the SA parameters
SA - Initial SA
SA - Idle State SA
SA - IAT/CTS Comp Bias SA
SA - Coolant Comp Bias SA
SA - Maximum SA
SA - Maximum SA Retard
SA - Startup Blend Filter
SA - ALDL Mode Added
LM - Delta TPS% Threshold Enter
LM - Delta MAP Threshold Enter
LM - Maximum MPH Enter
LM - Delta TPS% Lift Stay
LM - Delta MAP Lift Stay
LM - Period of LM SA
SA - Launch Mode
SA - Main Table
SA - Extended table
SA - Coolant Comp Spark Advance
SA - IAT/CTS Compensation
SA - Idle High Compensation
SA - Idle High Map Multiplier
SA - Idle Low Compensation
SA - Idle Low Map Multiplier
Entry: SA - HiWy vs MAP
PE - SA vs Gear/RPM
PE - SA Attack rate/fifth Sec

Of these, the only ones that do anything under closed throttle are those that are for idle, and from what I understand, those only work at idle at a standstill (0 mph), otherwise the main table is used. Someone please correct me if I'm wrong here.

marballfire

iTrader: (1)

Also just realized that I posted my Injector Correction Multiplier table instead of the injector correction offset table...here it is.

Ronny

iTrader: (1)

I am not familiar with that one in EBL? What is its purpose?
I am aware of DE however. And DFCO.
Have you confirmed you are actually in OL during bucking?

I would continue to drop SA incrementally and retest. Same on injector correction's. Note the only range it may see is 11-13-14 volts.

marballfire

iTrader: (1)

OL decel is supposed to help prevent the surging during decel that can be caused by proportional gains. it is definitely in OL during decel as it is set now. This is confirmed in the bin and the WUD.

I will try to drop the SA in the 20 MAP cells under 2000 RPM, but unfortunately I've got 3-4 inches of fresh snow on the ground, so its gonna have to wait a while for testing.

Ronny

iTrader: (1)

Good info. I will check my .bin to see if I have it set. I might benefit too but do not have surging(manual trans). I have DE set. DFCO is on over 35 mph. Both show clearly on WB.

marballfire

iTrader: (1)

Its option word 3 - Bit 5. If you have your prop gains dialed in and no surging under decel, you may not notice much benefit.

RBob

iTrader: (1)

No closed throttle SA table.

marballfire, have you tried the BIN I put together back at the end of December? If so and it didn't make any difference, enable async injection by setting this table to these values:

INJ - ASync Transition PW - TBI Only

Enter: 686.70 uSec
Exit: 991.90 uSec

See if that does the trick.

RBob.

marballfire

iTrader: (1)

I did try that bin and am still experiencing the same thing. Ill try enabling that and post back when I can drive the car again.

Dominic Sorresso

What's Idle State SA?

Tuned Performance

iTrader: (92)

How did that $61 in the stock ecm perform the one I did for you in september. If it didn't have this issue I can send it to rbob convert for the ebl.

marballfire

iTrader: (1)

In my bin, Idle State SA is 20.04 degrees

The chip you made for me (ANLUmanualmod.bin) didn't have this issue. I have actually gone back to that a couple times to see if the issue was mechanical, however, it still stops when i use the 8746 ECM with your chip. I sent that .bin to RBob at the end of December and he copied over a lot of tables, but the issue persists.

RBob

iTrader: (1)

OK, once you get a chance to try it with async enabled let me know. It may do the trick, and here is why.

Looking at the log you sent me I can now see what appears to be misfire. It occurs once the RPM drops into the 1000 RPM range (I was previously looking at higher RPM).

The AFR is rather on the rich side which may be the cause of the misfire. Running async during this time will actually be leaner (nature of the beast).

May also see if not running async, to lower the VE table in the 800 - 1400 RPM range, in the 20 & 25 KPa columns. That too will lean it out some during decel.

I wouldn't play with the SA as that is the same as with the other BIN.


There is something else that may or may not be part of this, which is IAC throttle follower. Does the car roll down (decel) at the same rate between the two BINs/ECM? This is with the throttle closed. If the one that doesn't buck rolls down at a slower rate, then the IAC is being held open further.

RBob.

marballfire

iTrader: (1)

Haven't gotten a chance to try the async yet...as soon as enough snow melts for me to get out of my driveway, I'll test it out.

In terms of the IAC, I'm not sure about decel rate, but i KNOW that when i rev the engine with the EBL bin vs. the 8746 bin, the IAC closes more slowly. With the EBL bin, I can hear the IAC is either opening more, or taking a lot longer to close than with the 8746 bin...I can just hear more air being sucked into the engine...does that make sense?

RBob

iTrader: (1)

> I can just hear more air being sucked into the engine...does that make sense?

Yes, that makes sense. This is from throttle follower (TF), which is the IAC opening as the throttle is opened. You can adjust the rate at which the IAC closes back down. A faster closing rate can/will also increase emissions.

With TF there is also a minimum step count once the vehicle is over a set MPH. This is the part that I was wondering about. As it would also affect the roll down rate when completely off the throttle.

RBob.

marballfire

iTrader: (1)

OK. so based on what I hear from the engine, the IAC closes down at a SLOWER rate in the EBL bin than in the 8746 bin. I know the EBL has WAYYYY more IAC settings than the 8746, so is this something I would be able to compare between the two?

RBob

iTrader: (1)

> so is this something I would be able to compare between the two?

Yes, many of the TF parameters have the same functionality between the two. To speed up the closing of the IAC due to TF there are three entries, or filters. A higher value will step the IAC at a faster rate:

IAC - TF Decay Filters

And this table defines the break points between the Low, Med, & High entries:

IAC - TF Decay MPH Breakpoints

Med being between the Low & High MPH entries.

When the maximum allowed TF steps is hit there is a delay before the IAC will start to step closed:

IAC - TF Decay Delay

Note that speeding up the closing of TF steps can increase emissions. So keep this in mind if there is an IM240 loop used for testing.

As for an entry that may affect the bucking, it is this one:

IAC - TF Min Steps

Those IAC steps are added to the current steps whenever the vehicle is moving faster then the Low MPH break point.

Now for the same entries in the '8746 code (ANLU):

Note that the '8746 firmware doesn't have the decay delays.

RBob.

marballfire

iTrader: (1)

are those items in the 8746 code visible in the parameter list window? My experience in tunerpro hasn't gone beyond modifying the scalars, flags, and tables in the parameter list.

EDIT: also, in CT, once a car is 25 years old it is emissions exempt. I had my car in for emissions in the summer, so emissions testing is no longer a concern.

Tuned Performance

iTrader: (92)

They are hacked in tuner pro for example 538 is 96 steps. rbob listed the address

marballfire

iTrader: (1)

So how do I actually access and view these entries? Sorry, I didn't even know until 5 minutes ago that things can be viewed/changed that aren't in the parameter list on the left side of the screen...

Tuned Performance

iTrader: (92)

IAC - TF Min Steps 540 is 0A

marballfire

iTrader: (1)

So do I need a hacked xdf file to view those? Sorry, I'm lost right now.

Tuned Performance

iTrader: (92)

look at the hex value or add the perimeter to the scaler list.

RBob

iTrader: (1)

0A as hex is 10 in decimal. So that value matches the stock ANLU value. You can use the Windows calculator to convert from hex to decimal. Open it up to scientific mode (View menu), click the Hex radio button, enter the hex value, then click the Dec radio button.

On a stick car I change the decay filters so that the RPM matches up on regular shifts. Closing the IAC too quickly causes the RPM to also drop quickly, making it more difficult to shift smoothly to the next gear.

RBob.

marballfire

iTrader: (1)

Cool. I found and made those changes to my EBL bin. I'll post back here with the results in a few days.

Ronny

iTrader: (1)

Is it not the idle SA when locked when bit is checked? Mine is set in constants at 20d when vehicle is at rest throttle closed regardless of RPM.

marballfire

iTrader: (1)

I believe that's right. as long as the car isn't moving, the throttle is closed, and the option word is checked, SA should be whatever you have it set to.

RBob

iTrader: (1)

Correct, +- any idle speed compensation SA.

RBob.

Dominic Sorresso

Ok. My confusion may come from the fact that the LT-5 cal has a Closed Throttle SA not an Idle State SA. So timing goes to x when throttle is closed regardless of speed.

RBob,

Just a quick refresher on relationship between TF v MPH and Min TF v MPH.
I don't remember if these were in EBL when I was using it, but they are in the LT-5 cal. Is one max and the other min? Any suggestion on how to tune the two?

marballfire

iTrader: (1)

Results seem to be pretty positive. I made the above changes and did several VE learns today. Disabled open loop decel to do some learning in that area and it pulled A LOT of VE in the low MAP area, as much as 30% over the course of several learns. Bucking sensation is greatly reduced, if not eliminated. The VE tables are the smoothest now that they've ever been as well. On the below table I only smoothed about 5 cells in the low RPM, MAP area to flatten that area. Next step is the TT-1 once i get a little more cash flow!

RBob

iTrader: (1)

That will do it. VE table looks good too.

RBob.

RBob

iTrader: (1)

It appears that the ECM calculates the TF steps from the TPS%, and also does a look up of it versus MPH (not the min table). Then chooses the one that has the lower number of steps.

BobR.

Dominic Sorresso

Rbob,

IOW, the min table is the default unless the TF table overrides based on ore factors. The reason I ask is because sometimes on Closed Throttle decel the motor will just shutdown. A characteristic of the LT-5 is that it wants to stall.
That explains some of the calibration values for IAC, idle,decel etc.you really can't slam the IAC shut or the motor will stall. So I've put in a bit more delay and decay in the IACs. I was reading one of your IAC papers and read about making sure that the motor doesn't dip below 4-500 rpm because it gets into the range of engine shutdown. That describes what happens when it stalls. I was curious if it could be the motor hunting between The Min and TF tables because it will oscillate a bit on decel.

RBob

iTrader: (1)

It is likely from the stall saver logic. That will cause an engine to stall like the key was turned off. Try setting the "SA - Stall Saver Enable RPM1" to 0.

The reason for the stall is that the ECM reverts back to the base spark advance by disabling the EST function of the ICM. $8D does the same thing, IIRC, I have a write up on it in the Tuning Guide Book sticky.

RBob.

Dominic Sorresso

RBob,

Thanks. I have attached a shot of the Stall Saver params as they are in my cal and compared to a stock bin. One of the issues I and a number of other ZR-1 drivers face is the use of more radical cams, albeit mild when compared
to SBC performance cams. So I have attached a screen shot of TPRT with my current and also stock values for the Stall Saver params. Also in the screen are the SA tables for too low/too high idle. I have lowered these values which helped tame some of the neutral coasting oscillation characteristic of modded LT-5s. Cammed LT-5s appear to be particularly sensitive to too much input on the controls. IOW, PID controls need to be minimized to maintain a smoother operation. Too big of a delta sends the motor off. What's curious in the posted params is that the Stall Saver disable rpm is 375, while the enable is 350. You are suggesting that I move the
RPM1 Enable to 0, correct? I'll give it a shot.

RBob

iTrader: (1)

Yes, set RPM1 to 0, if that doesn't do it try setting the 3 of them to 0. I don't have a bench for that ECM so can't try it.

RBob.

Dominic Sorresso

Bob,

We tried a bin w RPM1 (Stall Saver ENABLE) set to 0 and it appears that the stalling issue got worse. Should the Stall Saver DISABLE be set to 0 rather than the 375?
Is it odd that the DISABLE is set slightly above the ENABLE but that's the way it is in the stock bin?