Spark vs boost

[StealBlueSHO]

Would it be possible to have both? Request more boost/reduced timing at lower/mid rpm and reduced boost advanced timing at higher rpms? Seems plausible but then I really don't know anything anyway.

LMS has a way to curb the boost spike in first gear only which helps with traction off the line... not sure if that level of granularity can be continued... if needed..


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I've seen boost spikes are much more manageable and easily mitigated when desired boost is less than 190 kpa....In fact when the desired TIP is in the high 180's I don't even see boost spikes that would require a 3 bar map sensor. And you don't even run lean when you get a boost spike over what the map sensor can read because the 02 sensors would just add the fuel....It's not what you want but but that's what would happen so the idea that you automatically go lean if you exceed the map sensors range is wrong.

I agree that the boost spikes would be much less with lower desired TIP at 186.23kpa which is what the 4+x LMS tunes has. HOWEVER, Torries tunes and your tunes even when the desired tip was 201kpa I had boost spikes in first gear around 4000 rpms or so... 

Look at these LMS logs that were pulled from my car... in first gear the boost just...plateaus without a spike? while in second gear and third gear I see the normal looking boost curves with a peak. I know the are using the throttle to control load output... but can that be adjusted to allow different amounts of load in different gears at different RPMS?

As a side note... see how rich they tune for at the higher RPMs? Would it possibly be beneficial to run rich at the higher RPMs when its easier for the HPFP to do so since its cam driven to cool and compensate for the boost spike after the shift to assist in mitigating knock? They also lean up a bit after the shift.. seems like an interesting theory at least... guess at this one?

But in short, LMS is a prime example of less boost and more spark... more logs to enjoy and consume...


:OKE::

 

[StealBlueSHO]

When I dynoed from stock boost to 18.5 psi I ran the max spark that the fuel could tolerate and made more power at each boost level until about 18.5 psi....18.5 psi was only a few hp more than 17.5 so it wasn't really worth it.

I don't really think that less boost and more spark is necessarily a tactic for max power but rather a guarantee that you can rest easy knowing that people won't have inadequate fuel pressure and less problems and complaints coming back to your company since data logging is not required which is smart in my book. Because strangely enough not all SHO's have the same fuel delivery capabilities.

I've seen some SHO's look fine at 16 psi and some borderline at 13-14 psi.

When operating in an efficient zone of a given turbo, I've never seen a car make more power at lower boost compared to a higher boost when both are running max spark the fuel can handle

I would never send a tune without datalogging and run more than 13 psi.....Of course if I was only running 13 psi I wouldn't even run a 3 bar, there is just no need.

Stealblue on your car if we lowered boost the tables would've commanded more spark but since I'd say we were within the efficiency of the turbos we were moving more air at the higher boost and that coupled with running max spark is why I think it ran well

I think that sums up my take for now until I am provoked by the forum which happens a lot which is why I enjoy the forum lol

So would you be able to run the same spark of 20.5 degress at 13psi vs 16psi? Wouldn't knock become a factor? or are you more concerned about fuel pressure at point? If I am bass akwards let me know... but I assumed that there is a balance between the two?

 

[derfdog15]

AJPTurbo Delivers, in the thread, and in my inbox!

Here are some overlays of his big power pull vs. my pulls. An overlay vs. all three of my dyno runs (including the weird first one - lower power/torque) uncorrected and SAE. Also an overlay of his big pull vs. both of mine.

Note that the torque number is somewhat durring a boost spike like condition/tip in on his, mine is also at low end but more flat overall.

He ran more boost, less spark than I run on the pull, both power and torque are greater, but it shows that in this case boost was worth more power than spark.

SAE correction is a better comparison as it better accounts for weather, etc. His SAE correction factor is 1.04, due to his pull being at 78.94 deg F and 55% humidity.

My SAE correction factor is 1.01, due to 70.70 deg F and 33% humidity.

 

[ajpturbo]

When I dynoed from stock boost to 18.5 psi I ran the max spark that the fuel could tolerate and made more power at each boost level until about 18.5 psi....18.5 psi was only a few hp more than 17.5 so it wasn't really worth it.

I don't really think that less boost and more spark is necessarily a tactic for max power but rather a guarantee that you can rest easy knowing that people won't have inadequate fuel pressure and less problems and complaints coming back to your company since data logging is not required which is smart in my book. Because strangely enough not all SHO's have the same fuel delivery capabilities.

I've seen some SHO's look fine at 16 psi and some borderline at 13-14 psi.

When operating in an efficient zone of a given turbo, I've never seen a car make more power at lower boost compared to a higher boost when both are running max spark the fuel can handle

I would never send a tune without datalogging and run more than 13 psi.....Of course if I was only running 13 psi I wouldn't even run a 3 bar, there is just no need.

Stealblue on your car if we lowered boost the tables would've commanded more spark but since I'd say we were within the efficiency of the turbos we were moving more air at the higher boost and that coupled with running max spark is why I think it ran well

I think that sums up my take for now until I am provoked by the forum which happens a lot which is why I enjoy the forum lol

So would you be able to run the same spark of 20.5 degress at 13psi vs 16psi? Wouldn't knock become a factor? or are you more concerned about fuel pressure at point? If I am bass akwards let me know... but I assumed that there is a balance between the two?

I'm not sure what you mean exactly....If you were at 16 psi and 18 degrees on my tune and I lowered the boost to 13 then the spark would naturally rise because your load would go down which would request more spark.

BUt if you mean you are running 20.5 degrees at both boost levels and are not getting KR then I would say you need more spark at 13 psi.

 

[ajpturbo]

AJPTurbo Delivers, in the thread, and in my inbox!

I am good at putting it in the box....I had a hot teacher in highschool and every morning she would tell us to put our homework in a box on here desk....She would say "stick it in my box".....No lie she was a legend in our school lol

 

[StealBlueSHO]

When I dynoed from stock boost to 18.5 psi I ran the max spark that the fuel could tolerate and made more power at each boost level until about 18.5 psi....18.5 psi was only a few hp more than 17.5 so it wasn't really worth it.

I don't really think that less boost and more spark is necessarily a tactic for max power but rather a guarantee that you can rest easy knowing that people won't have inadequate fuel pressure and less problems and complaints coming back to your company since data logging is not required which is smart in my book. Because strangely enough not all SHO's have the same fuel delivery capabilities.

I've seen some SHO's look fine at 16 psi and some borderline at 13-14 psi.

When operating in an efficient zone of a given turbo, I've never seen a car make more power at lower boost compared to a higher boost when both are running max spark the fuel can handle

I would never send a tune without datalogging and run more than 13 psi.....Of course if I was only running 13 psi I wouldn't even run a 3 bar, there is just no need.

Stealblue on your car if we lowered boost the tables would've commanded more spark but since I'd say we were within the efficiency of the turbos we were moving more air at the higher boost and that coupled with running max spark is why I think it ran well

I think that sums up my take for now until I am provoked by the forum which happens a lot which is why I enjoy the forum lol

So would you be able to run the same spark of 20.5 degress at 13psi vs 16psi? Wouldn't knock become a factor? or are you more concerned about fuel pressure at point? If I am bass akwards let me know... but I assumed that there is a balance between the two?

I'm not sure what you mean exactly....If you were at 16 psi and 18 degrees on my tune and I lowered the boost to 13 then the spark would naturally rise because your load would go down which would request more spark.

BUt if you mean you are running 20.5 degrees at both boost levels and are not getting KR then I would say you need more spark at 13 psi.

The second portion answers my question.


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[ajpturbo]

And stealblue when you said my tune had boost spike in 1st gear when I was at 201 kpa desired is that when I had the throttle open and you were playing doctor boost controller LOL?...I think I wanted the gate to open and you wanted to delay the opening which allowed for a bit more spike which was ok because you had fuel pressure.

The throttle closures are awesome at mitigating boost spikes.

And there is a pretty big difference between 201 kpa and 186kpa....If I tune people at less than 185 ish I could keep the throttle open as boost spikes probably wouldn't go over about 215 is on the 2-3 shift.....But when I get into the 190 ish kpa then I need to use the throttle because boost spikes would exceed 220 kpa on the 2-3 shift and fuel pressure plummets and I'd rather not see that happen.

 

[StealBlueSHO]

And stealblue when you said my tune had boost spike in 1st gear when I was at 201 kpa desired is that when I had the throttle open and you were playing doctor boost controller LOL?...I think I wanted the gate to open and you wanted to delay the opening which allowed for a bit more spike which was ok because you had fuel pressure.

The throttle closures are awesome at mitigating boost spikes.

And there is a pretty big difference between 201 kpa and 186kpa....If I tune people at less than 185 ish I could keep the throttle open as boost spikes probably wouldn't go over about 215 is on the 2-3 shift.....But when I get into the 190 ish kpa then I need to use the throttle because boost spikes would exceed 220 kpa on the 2-3 shift and fuel pressure plummets and I'd rather not see that happen.

Hmmm negative, I wasn't referencing the wastegate mod.. the difference in the first gear spike is noted here... here is the log when you were tuning my car and the desired TIP was 199... notice the difference in the boost curve in first gear.. yes, your tune is running more boost by 13kpa.. however, that spike in first is what i would expect to see... in LMS that does not exist... both tunes are using the throttle to control spikes.

IN ANY EVENT... regardless of boost spikes which is has been beat to death...

The reason for the spike vs boost question is simply this....

If I am at the track, and my WGDC is sitting at 80% throughout the entire run my IAT's are going to climb yes? More so than if it was sitting at 60%?

IIRC the ecu scales back spark as the IAT's climbs?

So.. if I am running a tune that is originally targeting 20 degress of spark, but because my wastegate is running at 80% my IAT's climb, which by the time I am in 3rd gear, the ECU would scaling back on spark to 15 degress due to hotter air at the sensors which in effect would cause me to loose power?

If I am running a tune that is originally targeting 20 degress of spark, but my wastegate is running at 60% so my IAT's are not as hot, so when I am in 3rd gear, the ECU wouldn't scale the spark back as much if at all so I am still sitting at 20 degress of spark.. however, my boost will be lower but I maintain higher spark throughout the entire run...

So at which point is the breaking point? is 5 degrees of spark worth 1psi or so?

or am I looking at this all wrong?

 

[FoMoCoSHO]

SBS, yes when iat's climb the spark compensations take over so at my last outing I was down a ton of spark, like 8-10 degrees depending on where you look. Ambient was over 100 and IAT2 was over 170.

Trying to gauge how much power 1 degree of spark vs 1 PSI makes will vary by platform due to the amount of work performed. Number of cylinders, compression ratio, etc will all have an impact on how much work the extra mechanical leverage will provide.

 

[StealBlueSHO]

SBS, yes when iat's climb the spark compensations take over so at my last outing I was down a ton of spark, like 8-10 degrees depending on where you look. Ambient was over 100 and IAT2 was over 170.

Trying to gauge how much power 1 degree of spark vs 1 PSI makes will vary by platform due to the amount of work performed. Number of cylinders, compression ratio, etc will all have an impact on how much work the extra mechanical leverage will provide.

Thats some pretty harsh stuff to be running logs.. although.. I did the same LOL... Ambient was in the 115's once.. I should look at the logs again...

As far as the spark vs psi, I was hoping to reference only our platform for this.. as like stated, each platform is different, and so the equation would be different.

 

[derfdog15]

Look at the dyno data I posted above, I want to say that was a 17 psi TIP command, to my 15.25 psi tip command. His spark was 16 degrees advance, vs mine being 18-20 degrees advance.

Granted, not a major spark difference, but still a pretty decent difference in power, and especially the torque.

 

[StealBlueSHO]

Look at the dyno data I posted above, I want to say that was a 17 psi TIP command, to my 15.25 psi tip command. His spark was 16 degrees advance, vs mine being 18-20 degrees advance.

Granted, not a major spark difference, but still a pretty decent difference in power, and especially the torque.

RIGHT, but that is a 3rd gear pull on a dyno... not a multigear pull on the street or track where the IAT's are really going to climb. On a dyno, you are pulling one gear with a big ass fan in front of your car..

A long track run or on the street where IAT's are really going to come into play, that is what I am more curious about.. because again.. at what point do you start shooting yourself in the foot because of the hot air from high boost by our snails causing the IAT's to climb and pull enough spark to make a difference..

where does that line cross where running your turbos so close to efficiency that you start to loose ET because you are dropping spark due to IAT compensation? Again... its one of those.. I believe.. the answer to be.. "Well, try different tunes at the track.."

 

[derfdog15]

Like I said, once I get my times nailed down on current setup so I can apples to apples my time to the dyno numbers, I will work on checking a few other wastegate settings (it will be warmer so I can go higher on the spring).

I am running between 15 and 16psi now, with 20 degrees spark, after I know what I can do on these settings with my springs, I'll go down in boost, up in spark a bit for the track. If I get lucky and end up at a test and tune like the last one, where I can get 20 runs in the night, I can get a whole lotta comparison.

Of course doing so will require Brad to be patient with me, or us to make some arbitrary combinations/boost and spark desires, and then run the tunes. Will probably be march or april before tracks open and I am able, but I think it would be nice to see.

 

[FoMoCoSHO]

SBS, yes when iat's climb the spark compensations take over so at my last outing I was down a ton of spark, like 8-10 degrees depending on where you look. Ambient was over 100 and IAT2 was over 170.

Trying to gauge how much power 1 degree of spark vs 1 PSI makes will vary by platform due to the amount of work performed. Number of cylinders, compression ratio, etc will all have an impact on how much work the extra mechanical leverage will provide.

Thats some pretty harsh stuff to be running logs.. although.. I did the same LOL... Ambient was in the 115's once.. I should look at the logs again...

As far as the spark vs psi, I was hoping to reference only our platform for this.. as like stated, each platform is different, and so the equation would be different.

I like to know how my tune behaves in the worst conditions as well as the best.

AJP passed with flying colors. Trace of KR and it ran 12.6x. Corrected was 12.2x.

10 degrees x 4HP which is my best guess on what a degree of spark makes = 40 ish HP which jives with my time vs corrected time.

 

[ajpturbo]

SBS I don't think you have it wrong at all....Lots of good observations as usual...It's a tough riddle and stop making me look at logs lol...You antagonize me with data then I can't resist.

I just looked and yeah LMS does handle the boost spike well in 1st...But I'm curious how mine would've reacted when having a lower desired tip.....The boost logic is a P&I based...Proportionate and integral controller....So like I said things change when you request more boost because how the wastegates react is based on the error of where the boost is currently among other complex things.

Obviously I can't speak to what LMS does but they could have made some changes to improve the response of the gate.

I can say there are some changes I make to the gates to help with boost taper and that could've made the the boost ramp up faster....I can see that when you look at the spool up from 2600-3500 rpm mine was spooling up faster and higher boost in 1st gear than LMS...So maybe my boost logic had it spool up faster because something I did ramped on the gate more and that caused me to overshoot and spike....Could be good or bad depending on what you want...If you sping then it's bad.

LMS boost looks like it's smooth no doubt and handled well. Kudos.

I think my attempt to minimize boost taper helps thought..It looks like at the end of 2nd there is less boost fall off compared to what I am requesting...Even in 1st too but just a bit....It looks bad on mine but that's because the boost was too high so the slope is more severe.

See we can play nice.

For analysis this in depth I think is where dyno are nice

I never really see LMS tunes add spark it just stays flat with the knock sensor...Which is GOOD....but I think they are shy on spark at times which is safe

I run the boost I do because what I see on the dyno..Well into the 400's for the torque...I've seen LMS tunes on the same dyno as the one I ran on and it was kyle04 posted here and it was either low 400's or even shy of 400 I forget but I like the torque my tune gave.

Although the peak power wasn't that much more so is there a benefit? I dunno...I still never really understand why derf and I can make so much torque but not the peak power? I guess because the turbos aren't moving the air because they are tiny?

And excuse some of my typos...I type pretty fast for a outdoor non office working person lol I'm not a receptionist...I'm proud to type with proper form at 30-40 words a minute lol

 

[8nutz8]

If I am at the track, and my WGDC is sitting at 80% throughout the entire run my IAT's are going to climb yes? More so than if it was sitting at 60%?

IIRC the ecu scales back spark as the IAT's climbs?

So.. if I am running a tune that is originally targeting 20 degress of spark, but because my wastegate is running at 80% my IAT's climb, which by the time I am in 3rd gear, the ECU would scaling back on spark to 15 degress due to hotter air at the sensors which in effect would cause me to loose power?

If I am running a tune that is originally targeting 20 degress of spark, but my wastegate is running at 60% so my IAT's are not as hot, so when I am in 3rd gear, the ECU wouldn't scale the spark back as much if at all so I am still sitting at 20 degress of spark.. however, my boost will be lower but I maintain higher spark throughout the entire run...

So at which point is the breaking point? is 5 degrees of spark worth 1psi or so?

This is exactly the scenario that plays out in my head. I figure there has to be a happy efficiency range for these turbos that boils down to WGDC . . and i wonder if i'm not a good bit above it because of my boost level/altitude. . . but maybe not because i'm still getting 16-19* spark on straight 91 octane. But what if i was to dial back the boost and bring spark up to mean best torque levels? Happy turbos+good spark is where the power is at right?
Ignitions spark is mainly based on load/boost and IAT is just a modifier so load is gonna do the lions share in commanding timing, not to say IAT's don't have a relevant impact. My E20 tune commands just an extra 4.5 degrees of timing and holy hell can i feel it. I would safely say 25-30hp which inspires the thought that timing in this platform worth a little more.
As far as you mentioned earlier with LMS tunes commanding richer afr in the top end . . i've always felt throwing fuel to quench out kr is a cheap trick. Not to mention there's also a sweet spot for fuel at which you go richer it will make less power-much like MBT for timing.
Brad's gonna be a busy man this track season  :beer2:

 

[StealBlueSHO]

Stealblue on your car if we lowered boost the tables would've commanded more spark but since I'd say we were within the efficiency of the turbos we were moving more air at the higher boost and that coupled with running max spark is why I think it ran well

So spark follows load tables.. and based on datalogging the load PID, the load PID appears to follow the MAP pid or vice versa exclusively 99% of the time. I have seen cases during a log when I have had one my vacuum lines pop off (Thanks LMS for the weird blow off valve issues on the 4+x tune that doesn't allow the BOV to open correctly) causing the ECU to drop the WGDC to 0 effectively killing off all the boost.. which then because my load had just plummeted my spark advance went sky high I think into the 40's or so...

Point being, if spark follows the load tables.. and there has been mention that the logic in our vehicles pushes spark right up against the knock sensor as it scales it up, as a tuner, do you have control over how much spark gets added? In other words, can you program definitively that max spark would be 20 degrees for this given load?

Not exactly related to my original question... but curious non the less...

 

[8nutz8]

Stealblue on your car if we lowered boost the tables would've commanded more spark but since I'd say we were within the efficiency of the turbos we were moving more air at the higher boost and that coupled with running max spark is why I think it ran well

So spark follows load tables.. and based on datalogging the load PID, the load PID appears to follow the MAP pid or vice versa exclusively 99% of the time. I have seen cases during a log when I have had one my vacuum lines pop off (Thanks LMS for the weird blow off valve issues on the 4+x tune that doesn't allow the BOV to open correctly) causing the ECU to drop the WGDC to 0 effectively killing off all the boost.. which then because my load had just plummeted my spark advance went sky high I think into the 40's or so...

Point being, if spark follows the load tables.. and there has been mention that the logic in our vehicles pushes spark right up against the knock sensor as it scales it up, as a tuner, do you have control over how much spark gets added? In other words, can you program definitively that max spark would be 20 degrees for this given load?

Not exactly related to my original question... but curious non the less...

doubt it's your my opinion your looking for but from my interpretation. .
to command a max 20* for given load i believe you'd have to set your base spark to 20* and then essentially disable the knock sensors adaptive capabilities as to not add or subtract spark advance based on what they're seeing. i'm sure the expert will be here soon to elaborate but the tuner can control if and how much the knock sensors adjust Spark.


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[ajpturbo]

Not sure if this will be what you are looking for exactly but...You can set a max spark advance or total spark advance allowed by load and RPM.

And you can set how much spark can be pulled or added by load and RPM via the knock sensors.

Sometimes if you see your knock sensor go flat during a pull it's not because the spark is dialed in perfect and it's neither adding or pulling but  rather because it may want to add more spark but is not allowed because you have reached a max allowed spark value so the knock sensor lost it's authority.

For instance...If you left the spark strategy stock and ran E85 and you added a few degrees of spark you would probably see your knock sensor flat and you would expect to see the knock sensors add spark but since the spark was added to the tables possibly putting you up on a spark limiter then the knock sensor would not be allowed to add spark over that.

 

[Livernois Motorsports]

Stealblue on your car if we lowered boost the tables would've commanded more spark but since I'd say we were within the efficiency of the turbos we were moving more air at the higher boost and that coupled with running max spark is why I think it ran well

So spark follows load tables.. and based on datalogging the load PID, the load PID appears to follow the MAP pid or vice versa exclusively 99% of the time. I have seen cases during a log when I have had one my vacuum lines pop off (Thanks LMS for the weird blow off valve issues on the 4+x tune that doesn't allow the BOV to open correctly) causing the ECU to drop the WGDC to 0 effectively killing off all the boost.. which then because my load had just plummeted my spark advance went sky high I think into the 40's or so...

Point being, if spark follows the load tables.. and there has been mention that the logic in our vehicles pushes spark right up against the knock sensor as it scales it up, as a tuner, do you have control over how much spark gets added? In other words, can you program definitively that max spark would be 20 degrees for this given load?

Not exactly related to my original question... but curious non the less...

The tune is essentially doing what it should, it kills off the boost if the situation warrants it and if there is no boost timing is increased because the load fell off.
That's how it's written so I'm not sure where the question is that?