Fast355

iTrader: (2)

I just thought that I would highlight a change that I made that seems to be working very well. I can definately feel an increased pull at higher RPMs along with the fact it just runs smoother.

I bumped my distributer timing to 10* BTDC, left the initial setting at 10*, moved the SA offset from 9.81 to 0*. This left my timing alone, but advanced the injector firings 10*. That means the injectors fire 10* earlier every time. Seems to be working. Instead of waiting for the piston to be at TDC, then the injector firing, it fires right before TDC. This allows the fuel to stay in suspension better with the incoming air and more fuel to enter with the air.

Pulls smoothly past 5,000 rpm now where it previously pulled, but ran pretty rough there.

V8Astro Captain

iTrader: (1)

Very interesting idea!

What do you mean by SA offset. I can't find anything like that in TunerPro...

Fast355

iTrader: (2)

The offset or bias that is used on the timing table. It is usually set at 9.81*.

I am waiting for a couple of videos to load and process on Youtube to link to. Runs VERY well.

Pre-Tuner

iTrader: (2)

Do you notice any difference in performance under 5K rpm's?

Fast355

iTrader: (2)

It feels smoother throughout and gives the perception of a smoother idle.

Dominic Sorresso

Fast,

Do you think you'd accomplish the same thing by increasing the injector bias?
Have you found that you need to modify the VE tables, lower perhaps?
Are you referring to the Coolant Comp Bias?

Fast355

iTrader: (2)

I am MAF, seems like the DC% and everything stayed the same

Bias is still stock

It idled smoothly before, the BLM #s have always been dead on, even with the stock 5.3 MAF table in the PCM. Just seems to be smoother all around now, ESPECIALLY over 4,500.

Fast355

iTrader: (2)

It will show up here in a few.

Keep in mind that I still have 3.07 gears in place of the speedo calibration for 3.73s. The speedo is reading a good 10-15 mph slow. The traffic was moving roughly 80 mph on the highway. You can see I am moving when the 2nd sign on the side of the highway goes by. You can also tell that I didn't go WOT immediately off the line as the PCM was still in closed loop, in fact, I did not go WOT until it downshifted back into 2nd again.

I was actually kinda racing the V6 Accord in the lane over. Those newer V6 accords with their 250-270 hp V6 is actually a pretty quick car. Easily competes with my low-mid 15 second Van.

http://www.youtube.com/watch?v=GeyY5UZ0V6I

This is an abbreviated run, roughly 0-60 in 1st gear, than up to about 70 in 2nd.

http://youtube.com/watch?v=koWaPeAu3hg

Cold idle

http://www.youtube.com/watch?v=wRehD8He18E

Cold start and idle followed by a little rev. The audio sync is way off courtesy of Youtube.

http://www.youtube.com/watch?v=FmS1m3zlqHo

RednGold86Z

iTrader: (1)

Interesting theory, but (just to be the antagonist, and don't read this as an argument, hehe) I'm not convinced it's the injector spray timing from the TB that is the main cause of newfound power and smoothness (especially at high duty cycle)
Could be your cap and rotor finding better harmony with a clean spot matching between the two. Could be your MAF sampling also found a better point among the oscillations to read, unless you've also converted to dimented's synced sampling.
I just can't imagine a TBI responding to 10 degrees of injector spray difference, that's all.

Fast355

iTrader: (2)

I AM running the updated code.

The cap and rotor are not that old at all. It is possible, but I doubt it.

I dunno about the MAF sampling, could be, but it is still sync reading it.

Not reading it as that. Just an idea to kick around. Regardless of what caused it, it still runs better than before.

va454ss

iTrader: (1)

Labeled the same with EBL?

Fast355

iTrader: (2)

Should be, will have to look later when I pull up the laptop.

dimented24x7

iTrader: (2)

Did you try the advanced injector timing before updating to the newer code? The newer code does make a difference. My ball bearings boucing around in the exhaust sound went away with the sync'd reads, probably due to the more even fueling. I wonder how GM got around this with the earlier systems? IIRC, those didnt have syncronous reads. Just read it at 160 Hz.

Fast355

iTrader: (2)

No

I updated the code

Then switched to the 10* advanced injector timing late this week.

RBob

iTrader: (1)

With the distributor timing and BIN initial timing the same, that it is a wash (no difference in SA timing). Then by changing the SA offset (bias) to 0 from 9.81*, this change advanced the timing by 9.81* across the board.

RBob.

dimented24x7

iTrader: (2)

Good point. If he originally had his initial timing at 10 deg. BTDC and the dist. timing at 0 deg TDC, then he would have had 10 degrees pulled out at all times before. Changing the dist. timing brings the timing back in line with the tables. Removing the SA bias adds another 10 degrees on top of that. Assuming this is correct, there would be a total change of 20 degrees of SA.

Fast355

iTrader: (2)

Except that I went from 9.81 to 0 on the bias (I am talking about in the timing table equation and re-pasted the table, takes 10* out immediately) and left the distributer setting in the BIN at 0*. Then by advancing the distributer 10* the result is NO net change in timing, verified it with a timing light. I still have the same 19-21* of timing at idle I have always had.

alvanwie

Fast355 I think you confused everyone in your initial post because you said the initial in the ECM was set to 10*.

Fast355

iTrader: (2)

Yeah should have read what I posted better. It was set at 0* in the ECM. That change advances the injector firings 10*, but ALSO advances the timing 10*, that needs to be taken care of. Sorry for the confusion. The end result of the changes is just 10* initial timing on startup and 10* advanced injector firings, as well as possibly getting a better contact point on the cap and rotor. Regardless of what caused the change (not increased timing since I verified it with a timing light), it runs great all the way through the RPM range now. You only have to watch one of the videos to tell that. The 3.07 gears are kinda lame, but with 3.73s I would have traction problems.

dimented24x7

iTrader: (2)

Interesting that it makes a difference. I thought of how the base timing might influence the firings, but I never really thought it would produce much effect...

Edit: NVM... I see now

va454ss

iTrader: (1)

So has anyone else tried this?

Results?

Just so I understand fully: Timing at the dizzy set at 10*. Initial set a 0*.

Both "SA-IAT/CTS Comp Bias SA" and "SA-Coolant Comp Bias SA" set to 0* vs original settings of 9.84*?

oldred95

I'm going to give this a try. From what I understand the Main SA bias constant and the Base Spark Advance constant both need to be set to 0 (zero) and the distributor set to 10 advanced. I for the life of me can't remember what my distributor is set at, 10 advanced or 12 advanced but I'm going to give this a try anyway.

oldred95

Just tried this and I didn't do anything but idle it but before where my idle was somewhat unstable its silky smooth now. The thing that concerned me was that in the datalog it shows my idle timing is 40.xx degrees advanced. I don't believe it is actually that much, feels sounds and acts still like its at 20 advanced like it was set but I can't be for sure. Seems to me like in order for it to display right the Main Spark Bias needs to be raised from 10 up to 20. I wish Chris would chime in.

oldred95

Apparently nobody is interested so I will continue my conversation with myself. I have no idea how Fast did it by setting both the BIAS and Base Timing in the bin to zero. It did not work for me. Gave me 40 degrees of idle timing which resulted in a rediculously smooth idle but it spark knocked like mad. For me the spark BIAS had to be set at 20 to counteract the setting of zero on the base timing which from what I could tell and understand still gave me 10 degrees advance injector timing. Went for a drive and it felt totally different. It was smooth as glass and typically on 100 degree days I notice quite a bit of lag compared to say 80-90 degree days but that was gone. It actually had more power with less throttle. Didn't take it very high due to the slipping transmission but from what I can tell it works very well.

RBob

iTrader: (1)

If I understand what Fast355 was doing, I'll explain. Basically he is changing when the injectors fire by changing the distributor base timing. The injector firing point is relative to when the DRP is signaled to the ECM.

The ECM fires the injectors relative to the DRP. By moving the distibutor base timing the injector opening point relative to the crank angle has also changed. There are benefits to this. As the intake valve opening point vs cam spec moves, changing when the injector fires within the intake stroke can provide for smoother operation.

When making the changes to your calibration be careful with the bias value vs what is in the SA tables. THis area doesn't really change when the injector fires (vs. crank angle). It comes down to the distributor base timing setting.

If the distributor base timing is advanced, so is the injector opening point. And vice-versa, can also retard the injector opeing point by lowering the distributor base timing setting.

Done correctly this has no affect on the spark time. Other then cranking, max SA, and max retard. To keep the same SA (within maximum's) set the initial SA the same as the distributor base as it is changed.

RBob.

va454ss

iTrader: (1)

.

Pre-Tuner

iTrader: (2)

Let me make sure I have this correct.

Distributor set to 10° advance
Initial SA set to “0” from 9.84
SA IAT/CTS bias set to “0” from 9.84
SA Coolant bias set to “0” from 9.84

This seems to give me the same result as oldred94. 40xx degrees at idle displayed on the WUD.

What am I missing? Are one or both of the bias values supposed to be set to 20°?

RBob

iTrader: (1)

This is the only one that affects when the injectors fire:

Distributor set to 10° advance

By setting the initial along with the bias's to zero you are adding a lot of timing.

9.84 + 9.84 + 9.84 is 29.52 degrees of additional spark timing.

Which has no affect on the injector firing point. The way the code works is that the SA timing values from the tables are added together. Then the initial SA and the bias values are subtracted off.

RBob.

junkcltr

iTrader: (1)

We are talking about injector firing timing w/r/t DRP using bank fire (possibly batch fire) mode on a V8 here. It isn't going to make a difference how long you change the firing w/r/t DRP because of the 8 cyls. Well, as long as you fit the injector fire within the window for the current inject period.

What mask are we talking about here and in what mode? For example, if using the $0D mask with the incorrect fuel settings then this may help fix a problem with the incorrect fuel settings. As for any normal operating bin using bank or batch fire on a V8........this change shouldn't make a difference.

Fast335,
If you are using the $0D mask with the TBI_to_TBI doc changes then things aren't right and that could be why you are seeing a benefit. Also, the timing in the $0D is setup kind of strange. The $0D in CPI mode has a table for delaying the injector fire w/r/t DRP because of the software interrupt use. I don't see anything special about the videos. What are they supposed to be showing?

Pre-Tuner

iTrader: (2)

So by reducing the initial and biases, I'm actually adding timing?

So I advance the distributor 10°.

Set the Initial to 10°.

Leave the bias's alone?

Bear with my math:
Distributor adv. +10
+9.84 Initial -10
total timing added= 0

Correct?

RBob

iTrader: (1)

Yes, that is correct.

RBob.

Pre-Tuner

iTrader: (2)

Thank for the help and your patience.

oldred95

If thats the case then I've already had it like that for years. If I'm thinking right all that is doing is telling the PCM that the base timing is advanced 10 degrees. If I'm understanding this correctly then that doesn't advance the injector firing does it not? I thought the point was to trick the PCM into not knowing that the base timing has been advanced. That is why I had to set the base timing on the chip to 0, at the distributor to 10, and the spark bias to 20. Kept my timing the same but it acts and felt like it advanced the injector timing.

robertfrank

iTrader: (27)

Hey Fast if you could show me the actual tables for this change that would be awesome. I'd like to try this out.

Ronny

iTrader: (1)

RBobs quoteone correctly this has no affect on the spark time. Other then cranking, max SA, and max retard. To keep the same SA (within maximum's) set the initial SA the same as the distributor base as it is changed.
RBob.
Read his post completely above.

It does not appear that one can "affectively" change when the injector fires other than changing the SA. DRP will fire injector.

Now see Dominics comments. Quoteo you think you'd accomplish the same thing by increasing the injector bias? If I read this correctly the "injector bias" affects the injector timing. I see that tables is voltage referenced. So I recall higher voltage or lower voltage affects the injector timing so table compensates if voltage is other than 14.0. Using this table you might be able to tweek injector timing.

FAST was MAF in this thread using a PCM....

Drumer919

I did this today, got max timing at idle (45°) and it ran like ****.

Why is my coolant bias at 20°?

I think after reading back over this I did it wrong. All I change is actual distributor timing and the initial advance (the one that tells the computer where the disty is) but I leave the bias' the same?

dimented24x7

iTrader: (2)

It may be best not to play with the bias', if thats what your doing. Since tunerpro can be made to take the bias into account and show you your base timing, its best to leave them as is. The point of the bias is to allow for negative SA since the PCM cant effectivly do negative table lookups.

If you want to advance the injector firings, which may or may not help, you advance the dist. and set the base timing at the distributer in the PCM to the ammount the dist. is advanced. If you make it so the base timing is set at 10 deg BTDC, then you also set the base timing in the PCM to 10 deg BTDC. This way the PCM knows to remove 10 degrees from teh commanded advance to account for where the dist. is. Also keep in mind that if you advance the dist. too far, it will cause difficult starts, and can even damage or destroy the starter and flexplate if the engine kicks back. Id add no more than 10 degrees of advance at the dist.

If you ever go to MPFI with the PCM, there are settings in there that let you command when the injectors fire with respect to TDC. You can advance or retard the firings.