Smooth Boost or boost jump. What is causing this, I am baffled.

[FreeFlyFreak]

I mentioned this in a post in another thread here: max boost and load?

But thought I would give the issue its own thread as I believe it warrants it.

I stumbled across something in cld12pks map that had me baffled, the issue was this, the map worked great most of the time but if I rolled into the throttle slowly the boost would build to 10ish psi and then would not increase, even though throttle position was increasing. Then all of a sudden at what seems to be a set pedal position the WGDC would jump from 0 to something high and boost would jump instantly from 10's psi to 18's.

So I have been trying different maps trying to find out why and hopefully tune it out.
I have not figured it out yet and am looking for help.

It seems to be related to about 50 APP corrected, in other words the Throttle position that relates to 50 in the APP tables is where it seems to jump.......IF it jumps, and that is making it even more confusing.
I have seen that I can stop the spike from happening if I roll into throttle slightly quicker.

I have attached 4 logs and two maps to demonstrate what I am talking about.

Note particularly, in the log named Boost Jump Map4, the boost hits 10 psi at an actual pedal position of approx 40%, the pedal keeps getting pressed and the psi/load does not increase at all until approx 70% pedal (49% after app corr.) where the boost suddenly jumps to 16.5 psi. So that is 30% of pedal deflection that has zero effect on the car in that log.
Contrast that with the map that is called Smooth Boost Map 4, SAME map waaay different results.

An even better example of linear boost is in Smooth Boost Map 3, but compare that to the log of Boost Jump Map3. Same map, one log linear boost one log huge boost jump....

I have no idea why, so I attached the logs and maps, shout up if you have any ideas.
The maps have different APP tables which seem to have affected the pedal position that the jump happens at. There are also differences in the slope of the load and boost curves, basically I was trying to figure out what was causing/affecting this in order to tune the problem out.

Any ideas............. post up.

[FreeFlyFreak]

Well after more experimentation today, the change at 50 ish throttle is not related to throttle position, it is something else affecting where the abrupt change happens.
Because now I have a map that changes at 70 ish throttle instead of 50ish and the app tables haven't changed.
Right now I am leaning toward WGDC tables as the key as that was the major change in that map, but much more playing is needed for sure. Off to try another map right now.

[superskaterxes]

what about OL/CL transition?

[fjames]

I looked at S4 and J4 logs and the corresponding map (I assume.) It gets confusing lol.

One thing odd, the CL/OL transition happens much later (in both APP and load) on S4, but S4 is where you're moving the pedal faster, i.e. you'd think if there was going to be a difference, S4 would transition faster, not slower as it does. The load target for transition is right on with S4 however.

Boost Comp for 3rd gear is well down in the midrange on that map.

Another thing that seems backward is that you're hitting high boost at lower APP in J4. Since you're moving the pedal slower in J4, you'd think you'd have to give it more pedal than S4 to see the same boost. Or turn it around, it seems like you'd get higher boost with less pedal in S4 because you're moving it faster.

Something else funny - it's taking the same pedal range to make the same boost increase in both logs. From about 8 psi -> 16 psi takes ~30% pedal increase in both logs, they're just over different ranges (40/70 and 60/90.)

Have you tried a known good map to rule out mechanical issues? The boost you're "stuck" at looks like around spring pressure for you car.

[superskaterxes]

maby your actuator is getting stuck and hence why u see the jump

[FreeFlyFreak]

Originally Posted by superskaterxes what about OL/CL transition?

Nope. The logs show the loop, the problem is nowhere near it.

Originally Posted by fjames Have you tried a known good map to rule out mechanical issues? The boost you're "stuck" at looks like around spring pressure for you car.

That is what I am assuming it is, as the WGDC is zero, that is why the boost isnt rising, on the one log the boost stay at spring pressure from 40-70% actual pedal, then bam WGDC opens and boost jumps immediately from 10psi to 17-18. That is what I dont understand, there are no flat spots in any tables, so it is either using a different table at this point, or using some weird logic, or there is a mechanical issue with the WGDC solenoid.
Because it has hit spring pressure and that is it. Till it hits the magic spike area.

Originally Posted by superskaterxes maby your actuator is getting stuck and hence why u see the jump

Dont think it is the actuator (maybe the WGDC solenoid), as the WGDC is zeroed not commanding the actuator to close, then the WGDC opens and commands the WG closed, so when the actuator is told to move it does, that is where the problem happens.

If I drive aggressively, like I usually, do it is not a problem, but I stumbled across it and now I am just trying to figure out the cause. So far no joy.

I am going to try the same map I just used, and failed, but put the stock ramp up of boost and load so it gets above spring pressure early in the throttle, Im thinking that will solve it, but I have been surprised before.

Originally Posted by fjames I looked at S4 and J4 logs and the corresponding map (I assume.) It gets confusing lol.

Yes same number same map.

Originally Posted by fjames One thing odd, the CL/OL transition happens much later (in both APP and load) on S4, but S4 is where you're moving the pedal faster, i.e. you'd think if there was going to be a difference, S4 would transition faster, not slower as it does. The load target for transition is right on with S4 however. Boost Comp for 3rd gear is well down in the midrange on that map. Another thing that seems backward is that you're hitting high boost at lower APP in J4. Since you're moving the pedal slower in J4, you'd think you'd have to give it more pedal than S4 to see the same boost. Or turn it around, it seems like you'd get higher boost with less pedal in S4 because you're moving it faster. Something else funny - it's taking the same pedal range to make the same boost increase in both logs. From about 8 psi -> 16 psi takes ~30% pedal increase in both logs, they're just over different ranges (40/70 and 60/90.) Have you tried a known good map to rule out mechanical issues? The boost you're "stuck" at looks like around spring pressure for you car.

I think some of the differences you are seeing there is that the APP tables are different between the maps, I am logging actual pedal so you have to look at the map and convert to see what pedal the ECU is using after conversion. One map is fairly linear APP, the other is stock APP.

[jahman]

I have this same issue. I always thought it was only my car being queer and had thought about logging it and seeing whats up but never got around to it.

If its mechanical then we both have the issue, but I too am using a c12pk similar map. I notice it more in 4th gear and rolling into the throttle. Its rare I do this, but when I do I experience exactly what you are. I kinda like it though, lol, it really fucking takes off at that spike.

I never thought much about it because after all, theres nothing smooth about this car...nothing. But if you can figure it out, we should probably change it.

[FreeFlyFreak]

It is certainly not a mechanical issue, that occurred to me while I was driving just now.
It cant be mechanical, because I can change at will where it occurs, by changing the map.

It is just a matter of finding out what is causing it.
I have a feeling that, because we are just working with some of the tables, and we dont know the logic, that there are some changes we can make that then conflict with the hidden tables and then the car does things we dont expect.

I am leaning toward the best way to tune this car, to minimize this kind of conflict, is to to stick close to stock in some areas, such as the rapid boost load ramp up.

I just tried a map that was more stock like, boost load ramping up quick, and though there was too much traffic to say the issue is fixed it looked much improved, there still appeared to be somewhat of a level flat spot, where boost didnt build with pedal movement, but I saw no spike when I exited the "flat spot" just a return to linear boost build up, and that was good.
But with the traffic I cant say for sure.
I will try to test more later when the traffic dies down, get some logs and post the map and logs.

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EDIT post merge:

Ok after much experimentation I have an idea what is going on this (dont know why), it seems the car ramps up to spring pressure about 10psi following the TRL table, i have managed to get it a little above spring pressure by using higher WGDC, but the highest I have seen is 13psi ish, then the load levels out, for approx 20% points on the throttle 9If you have a fairly steep linear APP table). It is as if it drops out of the table and maintains more or less what it has got at that point until you press the pedal 20% more.

The point at which further throttle movement has no effect for 20% can be changed either using the slope of the TRL table, or by using the APP tables, problem with the APP tables is if you flatten it out like stock, the 20% dead spot becomes larger.

After the 20% of nothing happening, then the ecu seems to hop back into the TRL table at whatever that point is, and that is what causes the problem.
Especially if you have a steep TRL table! like cld12pks map.
Even the Linear Throttle maps have this going on, just not as severe a jump as cld12pk's map as the steepness of the TRL table is less.

I have not found a way to get rid of the "dead spot" in the pedal, but I have found a way to stop the huge boost jump from 10's to 17's, and that is to ramp the load up fast, similar to stock, until you hit loads that equate to 10-13 psi (will change with temp... another problem), that allows you to have the "top part of the curve" much flatter, so when that 20% of dead spot is over and you jump back into the table you are not far from where you left off in terms of load/boost, and WG opens smoothly, boost increases linearly with throttle again, no huge spike.

Another way to tackle it is to not drive like a friggin nancy, like I say I stumbled on it by accident, because I was stuck in moderate traffic. The way I normally drive I would never have noticed there was a problem.
But once I noticed I had to try and figure out what was going on, my GF sometimes drives tha car and........

I still dont know WHY that is happening, but at least I know what I can do about it.

[cld12pk2go]

Interesting. I have never observed the phenomenon you describe.

I know that my boost target table is like the OTS except the top 2 or 3 rows for highest throttle %, which leaves a gap between ~10 PSI and 21 PSI.

I just haven't bothered to smooth between these over then next several rows since the ~10 PSI range is fine for normal aggressive driving and then 21 PSI is great for smoking 3rd gear.

[superskaterxes]

driving like a nancy ftl....... haha