Spark, Advance, Min. Spark Question

[breal5825]

In the VCM Editor, under Engine > Spark > Advance > Minimum Spark > Base table... what does this table control?

I have a stage 1 package on my car. It's basically a cam and ported heads. When sitting at a red light, my car will sometimes jerk back and forth while in drive and me standing on the break. As we all know, when sitting at a red light just stopped, that jerking / surging shouldn't happen. My shop has been messing with this Min. Spark Base table and it's getting better but lately, I've been unable to get any further support from them. I'd like to mess with this myself to see if I can keep improving the situation.

So, I ask again, what does this table control and what would altering it do to the operation of my engine?

[spoolboy]

Post your tune file and a log of it surging while stopped.

[breal5825]

Post your tune file and a log of it surging while stopped.

Here ya go. This is a full read of my current tune (which I still haven't updated with my shift tables) and a test drive that I took where I was having the issue. I also should state that, maybe I'm using improper terminology when I say surging. While stopped at a red light, in Drive while my foot on the break, the car will jerk back and forth intermittently. I think surging is the proper term but again, I'm a newbie. It gets better each time my shop gives me a tune so whatever they're changing is helping.

I started using the compare option on the VCM Editor tool too try and figure out what they're messing with but again, it's kind of over my head. I'm also uploading the 4th and 3rd tune files so maybe you can see the progression on this issue. This current tune is the 5th iteration.

The surging in this test drive is happening pretty much at every stopping point. The times would be:
14:50:24
14:53:24
14:47:36
15:01:50
15:07:12
15:07:42
15:08:00
15:14:00
15:17:06


A2S_Final_R3_925rev.hpt
A2S_Final_R4_925rev.hpt
Full Read, 2019-10-28.hpt
Brandon Test Drive, Standard Mode, 2019-10-24.hpl

[spoolboy]

Log with these channels while it's surging and post the new log file:idle.Channels.xml

You can open scanner and choose that channel file directly once you have it downloaded to your laptop.

If you have a wideband on OBD there is a channel at the bottom for it. But I'm guessing you don't. You can delete that channel or just not use it.

[breal5825]

Log with these channels while it's surging and post the new log file:idle.Channels.xml

You can open scanner and choose that channel file directly once you have it downloaded to your laptop.

If you have a wideband on OBD there is a channel at the bottom for it. But I'm guessing you don't. You can delete that channel or just not use it.

Got it. Thanks. It's been raining here in NW Ohio for the past two days and I JUST had a major detailing job done to my baby so I can't really take it out on a road right now. Yeah, I know. It's only rain but that detail job was expensive and I'd like it to stay nice for at least a couple weeks.

Thanks for the channel file. I'll get it loaded into the scanner and take it for a drive here soon and will post the results.

[richhurley]

One thing to try is adding more air to the Airflow and Small/Large Range tables . Start with adding 5% to the <1V rows and keeping adding to see if the surging subsides.

[tbrtuning]

One thing to try is adding more air to the Airflow and Small/Large Range tables . Start with adding 5% to the <1V rows and keeping adding to see if the surging subsides.

Airflow tables is the best way to dial things in for a cam in my opinion. Wasn't even touched in the tune he posted

[breal5825]

Airflow tables is the best way to dial things in for a cam in my opinion. Wasn't even touched in the tune he posted

Which tabs in the tune file would these table be in? I am definitely a beginner in this tuning game so I'm not sure where to find the table you're talking about.

Also, what's the risk associated with raising these values up? Is there a point at which engine damage is being risked? I just don't want to do anything potentially dangerous.

[breal5825]

Log with these channels while it's surging and post the new log file:idle.Channels.xml

You can open scanner and choose that channel file directly once you have it downloaded to your laptop.

If you have a wideband on OBD there is a channel at the bottom for it. But I'm guessing you don't. You can delete that channel or just not use it.

BTW: I will be uploading a test drive with these channels ASAP. Now that I have my custom shift tables loaded, as you can see from the other thread you've been helping me on, I can now come back to this.

[richhurley]

Here are the changes you can try to the airflow tables:

Engine -> Airflow -> Electronic Throttle -> Airflow Multiple rows 0.00-0.90 by 5% (x 1.05).
Engine -> Airflow -> Electronic Throttle -> Small Range Multiple the entire table by 95% (x .95).
Engine -> Airflow -> Electronic Throttle -> Large Range Multiple rows 0-554 by 95% (x .95).

Based on your posted Full Read tune, your tables would be:

Airflow:
0 6.34931315092447
0.0195503421309873 12.5002102658826
0.0488758553274682 22.0241799922693
0.0977517106549365 39.0879590853788
0.151515151515152 58.1358985381522
0.20039100684262 78.9695823146231
0.351906158357771 156.550252377482
0.498533724340176 261.909167475635
0.747800586510264 520.643678375807
0.899315738025415 695.646622098163
1.05083088954057 882.356111942535
1.25122189638319 1196.0518648054
1.50048875855327 1661.33746914658
1.65200391006843 1995.86690578592
1.85239491691105 2514.72483983802
1.99902248289345 2945.48605392106
2.24828934506354 3824.8659253241
2.50244379276637 4832.02572388949
3.01075268817204 7072.53960202197
3.49951124144673 8758.28224359241
3.79765395894428 9292.41821241393

Small Range:
5.94473045258676 0
20.9654444253549 0.0476190476190476
36.6837147745673 0.0927960927960928
75.1268217430553 0.19047619047619
123.335717981764 0.283272283272283
182.4187430666 0.380952380952381
250.383986011493 0.476190476190476
452.055285067957 0.67032967032967

Large Range:
5.95248107899169 0
36.7069666537821 0.0927960927960928
75.1500736222701 0.19047619047619
123.26596234412 0.283272283272283
183.038793178995 0.380952380952381
348.964203255888 0.57020757020757
553.580740346228 0.761904761904762
811.025547012618 1.002442002442
1661.2382611286 1.5006105006105
2945.48605392106 1.998778998779
4831.92651587151 2.5018315018315
7037.07273559297 3.001221001221
7732.27292161021 3.2014652014652
8422.01666663837 3.4017094017094
8941.12262073544 3.6019536019536
9116.7208125657 3.6996336996337
9292.31900439595 3.7985347985348

[breal5825]

Here are the changes you can try to the airflow tables:

Engine -> Airflow -> Electronic Throttle -> Airflow Multiple rows 0.00-0.90 by 5% (x 1.05).
Engine -> Airflow -> Electronic Throttle -> Small Range Multiple the entire table by 95% (x .95).
Engine -> Airflow -> Electronic Throttle -> Large Range Multiple rows 0-554 by 95% (x .95).

Based on your posted Full Read tune, your tables would be:

Airflow:
0 6.34931315092447
0.0195503421309873 12.5002102658826
0.0488758553274682 22.0241799922693
0.0977517106549365 39.0879590853788
0.151515151515152 58.1358985381522
0.20039100684262 78.9695823146231
0.351906158357771 156.550252377482
0.498533724340176 261.909167475635
0.747800586510264 520.643678375807
0.899315738025415 695.646622098163
1.05083088954057 882.356111942535
1.25122189638319 1196.0518648054
1.50048875855327 1661.33746914658
1.65200391006843 1995.86690578592
1.85239491691105 2514.72483983802
1.99902248289345 2945.48605392106
2.24828934506354 3824.8659253241
2.50244379276637 4832.02572388949
3.01075268817204 7072.53960202197
3.49951124144673 8758.28224359241
3.79765395894428 9292.41821241393

Small Range:
5.94473045258676 0
20.9654444253549 0.0476190476190476
36.6837147745673 0.0927960927960928
75.1268217430553 0.19047619047619
123.335717981764 0.283272283272283
182.4187430666 0.380952380952381
250.383986011493 0.476190476190476
452.055285067957 0.67032967032967

Large Range:
5.95248107899169 0
36.7069666537821 0.0927960927960928
75.1500736222701 0.19047619047619
123.26596234412 0.283272283272283
183.038793178995 0.380952380952381
348.964203255888 0.57020757020757
553.580740346228 0.761904761904762
811.025547012618 1.002442002442
1661.2382611286 1.5006105006105
2945.48605392106 1.998778998779
4831.92651587151 2.5018315018315
7037.07273559297 3.001221001221
7732.27292161021 3.2014652014652
8422.01666663837 3.4017094017094
8941.12262073544 3.6019536019536
9116.7208125657 3.6996336996337
9292.31900439595 3.7985347985348

I'll give this a try, if I can ever get connected to my vehicle again. I updated my shift tables recently and they wrote just fine. Then I went on a test drive with VCM Scanner to see if my modifications worked out right, which they did. I then tried to connect again a little later in the day with the channels suggested by spoolboy and now I'm getting this error message. I've tried unloading and reloading the VCM Suite, reloading the drivers, nothing is working. I have a ticket in to support too that has so far gone unanswered.

Capture.PNG

[breal5825]

Log with these channels while it's surging and post the new log file:idle.Channels.xml

You can open scanner and choose that channel file directly once you have it downloaded to your laptop.

If you have a wideband on OBD there is a channel at the bottom for it. But I'm guessing you don't. You can delete that channel or just not use it.

FINALLY managed to get my crap straightened out and was able to do a logged test drive today with the channels you gave me. It is attached to this post. Let me know what you, and anyone else, thinks of the results. The jerking around was most evident very early on in the test drive. I was stopped behind another vehicle at a stop sign at the end of my street so right after I backed out and started driving, I was almost immediately at a prolonged stop and the jerking was pretty bad. Once I got going and the car warmed up, the jerking wasn't as bad at red lights but it was still present to some degree at any stopped situation.

Brandon Test Drive, Standard Mode, Idle Channels, 2019-11-05.hpl

[spoolboy]

Your peaks of your rpm swings are going over 1000rpm which is probably high enough to cause the engine to slightly load the stock low-stall converter.

A couple of things you can try. First, see if the car will be happy idling around 850 or even 800rpm instead of 928. Open up all of your idle rpm tables and lower the lowest settings to 850 instead of 928 and then blend the cells near them into the higher numbers in the next couple of cells.

If that helps but doesn't completely fix it, try dropping to 800rpm and blending again. If that is worse instead of better....

Does your car have a larger throttle body? If so, it might explain what I'm seeing.

Comparing your log to a log from my (similar) car, I see that your throttle blade is not open as far at the same idle rpm as mine is. Instead there is more ignition advance being commanded to acheive a higher idle rpm. This is backwards to what most engines with a larger cam want. They definitely need more airflow AND tend to idle better/higher with more igniition lead. Your idle vacuum is also low as a result of this. I beleive the airflow tables mentioned above can affect the idle throttle blade position. I would shoot for 20% open or a little more at a warm idle.

The other thing you can work with is the PID controls for the spark and airflow in the idle tables. I am not knowledgeable on adjusting these yet.

Hope that helps.

[kenandjenn4551]

In the VCM Editor, under Engine > Spark > Advance > Minimum Spark > Base table... what does this table control?

I have a stage 1 package on my car. It's basically a cam and ported heads. When sitting at a red light, my car will sometimes jerk back and forth while in drive and me standing on the break. As we all know, when sitting at a red light just stopped, that jerking / surging shouldn't happen. My shop has been messing with this Min. Spark Base table and it's getting better but lately, I've been unable to get any further support from them. I'd like to mess with this myself to see if I can keep improving the situation.

So, I ask again, what does this table control and what would altering it do to the operation of my engine?

The Idle Torques will solve this. The car likely has a ton of timing movement.... this really needs to be limited to keep the idle relatively stable.

I set my minimum timing values to 2* in the idle cells and my PT timing is 18 degrees. The surging you feel while stopped is the car overcompensating with torque to bring up a idle that is below desired.

I would set your idle at 800-850 initially and play with Drive Proportional Spark to try and calm it down.

In reality, it takes a lot of fine tuning on the Spark and Throttle torque side to get everything to really play nice, but Proportional spark will really make it surge in drive.

Essentially, you want to allow the rpms to fluctuate some, but not to much. My car has about a +/- 50-70 rpms swing from the base of 800.

If it dips to much below 800 rpms, idle torques (both spark and throttle) will kick in and raise the idle.... if to much correction is applied... surge, surge, surge.

Ideally, your timing will only move maybe 10-15 degrees and do so rapidly. On the plus side, this produces a nice cam lope that isn't the "Chop" that everyone has due to huge timing movement.

Send me an IM....I have spent many, many hours working on this area of my tune and it is tough when you first start out.

[breal5825]

Your peaks of your rpm swings are going over 1000rpm which is probably high enough to cause the engine to slightly load the stock low-stall converter.

A couple of things you can try. First, see if the car will be happy idling around 850 or even 800rpm instead of 928. Open up all of your idle rpm tables and lower the lowest settings to 850 instead of 928 and then blend the cells near them into the higher numbers in the next couple of cells.

If that helps but doesn't completely fix it, try dropping to 800rpm and blending again. If that is worse instead of better....

Does your car have a larger throttle body? If so, it might explain what I'm seeing.

Comparing your log to a log from my (similar) car, I see that your throttle blade is not open as far at the same idle rpm as mine is. Instead there is more ignition advance being commanded to acheive a higher idle rpm. This is backwards to what most engines with a larger cam want. They definitely need more airflow AND tend to idle better/higher with more igniition lead. Your idle vacuum is also low as a result of this. I beleive the airflow tables mentioned above can affect the idle throttle blade position. I would shoot for 20% open or a little more at a warm idle.

The other thing you can work with is the PID controls for the spark and airflow in the idle tables. I am not knowledgeable on adjusting these yet.

Hope that helps.

One thing I'm going to stop doing when referring to my issue is called it, "surging". I'm a rookie and I've been corrected on what that term actually means and I now know that's not what I'm experiencing. This jerking effect while at a standstill, in drive and foot on the break is an issue that is not surging.

When I first got the car from the shop, they had the idle set at 850. I loved the sound but the jerking was terrible. Using my limited knowledge at the time, I asked for a raised idle because my thought was that the increased idle would smooth out the car. My shop did this for me but maybe that wasn't the right way to go. I'll try dropping it back down to 850 and see if that fixes thing. Another reason I wanted the idle higher was because sometimes with my foot off the gas and idling through parking lots or drifting up to my driveway, at low speeds like that, the car would stall. Raising the idle virtually eliminated that situation as well. Since doing that, it hasn't stalled even once.

I do not have an aftermarket throttle body. It's still the factory stock. I was considering that upgrade but I didn't want to put any more money into performance upgrades until this core issue was solved. If I adjust the idle back down as per your suggestion, will the ignition advance self correct since I'll be idling at 850 instead of 925? Will I be at risk of stalling again while at low speeds?

[breal5825]

The Idle Torques will solve this. The car likely has a ton of timing movement.... this really needs to be limited to keep the idle relatively stable.

I set my minimum timing values to 2* in the idle cells and my PT timing is 18 degrees. The surging you feel while stopped is the car overcompensating with torque to bring up a idle that is below desired.

I would set your idle at 800-850 initially and play with Drive Proportional Spark to try and calm it down.

In reality, it takes a lot of fine tuning on the Spark and Throttle torque side to get everything to really play nice, but Proportional spark will really make it surge in drive.

Essentially, you want to allow the rpms to fluctuate some, but not to much. My car has about a +/- 50-70 rpms swing from the base of 800.

If it dips to much below 800 rpms, idle torques (both spark and throttle) will kick in and raise the idle.... if to much correction is applied... surge, surge, surge.

Ideally, your timing will only move maybe 10-15 degrees and do so rapidly. On the plus side, this produces a nice cam lope that isn't the "Chop" that everyone has due to huge timing movement.

Send me an IM....I have spent many, many hours working on this area of my tune and it is tough when you first start out.

Sending a private message now. Thanks for any help provided. My biggest fear is that I'm going to make some kind of adjustment that's going to blow up the engine. The shop that did the engine work told me about a previous customer that attempted to tune his Hellcat Redeye and the engine, in their words, exploded. Bottom line, I'm scared as hell to modify anything that I don't completely understand or that an expert has looked over and given me some kind of green light. I love this car and I want to keep it for awhile.

[richhurley]

I had the same issue and at first started working with the idle torque tables which helped a bit. The fix for me was putting the idle torque tables back to stock and adjusting the airflow tables.

[breal5825]

I had the same issue and at first started working with the idle torque tables which helped a bit. The fix for me was putting the idle torque tables back to stock and adjusting the airflow tables.

OK. I still have yet to try the various suggestions on this thread of the airflow tables (your suggestion) and lowering the idle speed (spoolboy and kenandjenn4551). When you say the idle torque table, are you referring to the Engine > Idle > Torque > Drive / Reverse table? On my tune, it is set to ones (1) for all RPMs. I don't have a stock version of that table. When I got my car back from the shop, the initial tune was all I had in the car. What would a stock version of this table look like and what does this table control? For example, if I set the values to all 2s, what does that really mean and how would it affect the car at idle?

[breal5825]

I had the same issue and at first started working with the idle torque tables which helped a bit. The fix for me was putting the idle torque tables back to stock and adjusting the airflow tables.

If I'm looking at these tables correctly, here's what I think is happening. The gas pedal in this car is a throttle by wire system. Thus, when I push on the gas pedal, I'm actually increasing the voltage that's flowing to the throttle body. For the airflow table, as we increase the voltage, we're opening the throttle body wider. By increasing rows 0 to 0.9, we're telling the vehicle that at these lower levels of throttle, open the throttle body 5% more than the stock settings. Also, it looks like max throttle voltage is 3.8 volts so 0 to 0.9 is actually everything from 0% to 25% throttle. Am I on the right track? What effect will this have during driving? In my test drives, typical driving for me is virtually always below 25% throttle. Sure. I get on it from time to time but just regular driving with traffic all around me and I can't go crazy, I'm pretty much always going to be less than 25% throttle. What will that increased airflow do to the air/fuel mixture and engine performance?

As for the Small and Large Range tables, this looks kind of like the inverse of the Airflow table. These two tables seem to actually represent one table as the Small Range values live between the 6 to 554 rows on the Large Range table. By having two tables, it's allowing us to have finer control at lower throttle. By decreasing everything on the Small and everything up to 554 on the Large, we're saying that when the airflow is this much pounds-per-hour, this is where the throttle voltage should be on the gas pedal. By increasing the 0% to 25% on the airflow table, we need to make up for that by decreasing the relative values on these two tables.

Am I making sense and following along with what's happening?

And again, the big ask here, what's the risk, if any, to my car. If I upload this modification and start the car, what's the worse thing that could possibly happen? I'm not afraid to admit that I'm a bit scared to do something like this without knowing the answer to this question. Many, many thanks for everyone's time on this.

[richhurley]

I was referring to the Engine -> Idle -> Airflow -> Idle Torque Spark/Idle Torque Throttle tables.