Map Limit didn't engage during Shift Cut

[cj.surr]

And I threw a rod in my built motor. At the top of 3rd gear, it kissed rev limiter for about .3s and then was in shift cut for .2s. Torque reintroduction for .1s. During that period, MAP exceeded the limit specified and maxed out my MAP sensor. MAP limit did not engage until torque reintroduction was fully complete. So the engine saw full load at over 315kpa (sensor max) where I had my MAP limit at 290kpa.

Seems like a major oversight that it would be disabled during flat shift, especially so during torque reintroduction. No doubt in my mind that the engine would have stayed together if MAP limit engaged. Fully built BMW motor, so I'm out a lot of time and money. Really disappointed overall.

E28.pclr Log 2019-10-19 3;27;01 pm motor blow n.llg

[Ducie54]

So when you first configured your RPM limit did your boost pressure still rise? I wouldn't be using Ignition cut on a turbo Engine but that's me as your still pumping fuel into a hot turbo manifold. 

Also you AFR is not even close to tracking the target? 

[Ducie54]

After another look it looks like your MAP limit cut is set up like the RPM limit cut. So when you hit RPM cut the boost pressure goes up how do you expect the MAP limit to DROP boost? I would take it back to the tuner and ask why this hasn't been tested. I would also add more resolution in your boost target table at the MAP limit. So when it gets close to MAP limit the DC% drops. EG set 295kpa row several % lower than the 290 row, set the 300 kpa to ZERO. That way your not relying on PID to reduce DC% when @ MAP limit.

[cj.surr]

3 hours ago, Ducie54 said:

So when you first configured your RPM limit did your boost pressure still rise? I wouldn't be using Ignition cut on a turbo Engine but that's me as your still pumping fuel into a hot turbo manifold. 

Also you AFR is not even close to tracking the target? 

I don't remember the boost pressure rising when setting up the RPM limit. That being said, I didn't set it up 8 seconds into a drag run, so obviously the manifold would be much colder and much less prone to boost level rise. I'm not saying my RPM limit and shift cut settings are perfect, I can see that they need some changes. 

AFR target is 12.0 and it's in low 11s... Not sure what your point is there.

53 minutes ago, Ducie54 said:

After another look it looks like your MAP limit cut is set up like the RPM limit cut. So when you hit RPM cut the boost pressure goes up how do you expect the MAP limit to DROP boost? I would take it back to the tuner and ask why this hasn't been tested. I would also add more resolution in your boost target table at the MAP limit. So when it gets close to MAP limit the DC% drops. EG set 295kpa row several % lower than the 290 row, set the 300 kpa to ZERO. That way your not relying on PID to reduce DC% when @ MAP limit.

I am the tuner and I don't expect MAP limit to control boost. That's why I have the hard limit set at 3kpa and basically no control range. I have a slow ign % return on igntion cut. If it overboosts, I get 100% ignition cut and a couple seconds to lift off the pedal. That's how I want it and how I have tested it successfully. My turbo is far too high strung to try to use fuel or ignition cut to control it. 

I see what you're saying about lowering the DC but it should have never been in that boost area. Boost cut should have engaged at 293kpa. Instead it let me get to over 315kpa at full load.

You can try to bash the tune all you want, but at the end of the day, MAP limit didn't work when it should have and that's what allowed the motor to blow. The car was still in progress of being tuned, I was counting on MAP limit to save the motor if it came to that. 

[Ducie54]

Boost cut cant engage @293KPA as you were already in RPM cut. Once RPM cut dropped out MAP Limit was activated. 

The trend shows boost raises when ignition starts being pulled from rpm cut then more again from shift cut. One point during your cut ignition angle is @ -5 deg while at 100% throttle Still with fuel being sprayed.  

[cj.surr]

1 hour ago, Ducie54 said:

Boost cut cant engage @293KPA as you were already in RPM cut. Once RPM cut dropped out MAP Limit was activated. 

The trend shows boost raises when ignition starts being pulled from rpm cut then more again from shift cut. One point during your cut ignition angle is @ -5 deg while at 100% throttle Still with fuel being sprayed.  

I'm very aware of what happened. I feel like you didn't read my first post.

My question is: why doesn't MAP limit engage during rev limit or shift cut or torque introduction? All of these can be progressive cuts, meaning some cylinders are still being fired at full load and over the MAP limit. It seems like an oversight to me. I'd really like to see it changed.

[Ducie54]

I was trying put it nicely that you did a poor job on setting you limits. MAP limit WAS engaged during shift cut it pulled 3.6 Deg out it just wont do both MAP and RPM at ONCE.

Why don't you set the RPM cut so it doesn't create a Boost over spike?

And this is why the wastegate DC% table is so important, why do you have a target DC of 48% @ 300kpa if your limit is 290KPA?

[cj.surr]

8 minutes ago, Ducie54 said:

I was trying put it nicely that you did a poor job on setting you limits. MAP limit WAS engaged during shift cut it pulled 3.6 Deg out it just wont do both MAP and RPM at ONCE.

Why don't you set the RPM cut so it doesn't create a Boost over spike?

And this is why the wastegate DC% table is so important, why do you have a target DC of 48% @ 300kpa if your limit is 290KPA?

 

When I look at the log, I see MAP limit being activated at 22.18s. At 22.03s, my MAP is over the limit at 303kpa and rising. The hard limit is set to 100% igntion cut and the hard limit delta is set at 3kpa. MAP limit at this point is somewhere between 290 and 300kpa. 100% ignition cut did NOT engage and MAP limit did not pull timing. The timing being pulled is from the torque reintroduction. MAP limit 100% cut only takes place after torque reintroduction is complete. The MAP limit status is not logged at a fast enough rate to get an exact idea of when it was actually flagged as active, but you can tell the ignition cut is not where it should be.

I don't understand why you're being argumentative. I completely understand that the RPM limit settings were too aggressive. Your suggestion about the DC% table is honestly ridiculous because the engine should have a 100% ignition cut INSTANTLY if it ever passes the MAP limit + 3 kpa. The ECU should never need to be pulling a DC% from there. The wastegate would not act fast enough to save the engine anyway. And you can completely forget about that helping in a wastegate failure scenario.... It's a hack and incomplete way to prevent an overboost.

It's clear that the hard limit on boost cut did not come in when it should have because it was during a shift cut (partial cut). What I want is an answer from the developers why it was programmed this way and if this can be changed.

[Ducie54]

21 minutes ago, cj.surr said:

When I look at the log, I see MAP limit being activated at 22.18s. At 22.03s, my MAP is over the limit at 303kpa and rising. The hard limit is set to 100% igntion cut and the hard limit delta is set at 3kpa. MAP limit at this point is somewhere between 290 and 300kpa. 100% ignition cut did NOT engage and MAP limit did not pull timing.

 Again Map and Rpm limit will not activate at once you can see that in the log file. RPM limit starts @ 21.581 and finish's at 21.181 MAP limit starts at 21.181ms at 315 kpa. Soft cut kicks in timing goes from 8.9 to 4.3 @22.232ms 297Kpa @ 22.271 MAP is now at 213Kpa and outside Hard cut range. 

36 minutes ago, cj.surr said:

I don't understand why you're being argumentative. I completely understand that the RPM limit settings were too aggressive. Your suggestion about the DC% table is honestly ridiculous because the engine should have a 100% ignition cut INSTANTLY if it ever passes the MAP limit + 3 kpa. The ECU should never need to be pulling a DC% from there. The wastegate would not act fast enough to save the engine anyway. And you can completely forget about that helping in a wastegate failure scenario.... It's a hack and incomplete way to prevent an overboost.

 

Im argumentative as your topic says (Map Limit didn't engage during Shift Cut) Which is false and the above screen shot show it was engaged, your blaming that as to the reason of the damage. My suggestion come from the theory of HPA academy and works well when boost is over target. BUT cutting fuel and ignition will also be best for setting a limit. 

 

44 minutes ago, cj.surr said:

It's clear that the hard limit on boost cut did not come in when it should have because it was during a shift cut (partial cut). What I want is an answer from the developers why it was programmed this way and if this can be changed.

No it didn't come into effect as you were still in RPM cut. By the time it switched from RPM to MAP limit and applied soft cut it was UNDER the MAP hard cut threshold. The help file shows a 3D pic of how the advance mode works.

[cj.surr]

29 minutes ago, Ducie54 said:

 Again Map and Rpm limit will not activate at once

Yes, exactly. This is the problem with the code. Why wouldn't this be possible? I have already explained how this can be dangerous. MAP Limit should always be able to 100% cut ignition if boost is above the hard limit.

It shouldn't matter if the engine is in RPM Limit, shift cut, whatever. If there are ignition events occuring, MAP should not be above the limit, period. 

[Ducie54]

So your topic should be why does Rpm limit lock out map limit. 

Agreed should be nice if both worked simultaneously but a RPM cut shouldn't build boost if setup correctly. 

HPA do some good webinars on boost control and setting limits. 

[Adamw]

I know there were some significant changes made to the limiters in 5.6.7 firmware so I held off replying until I could test your file in an ecu with 5.6.7.  Unfortunately I still see a similar effect where the MAP limit doesnot initiate until the gear shift cut is finished.

Im not sure it there is a reason for it or if it is something that can be improved but I will bring it to @Simon's attention so he can pass your logs and file on to the engineers for a look.  The limiter priorities and how all the limiters interact is very complex and even over my head in the few discussions I have had with the engineers in the past.  

I really do sympathise, but its hard to imagine how 25Kpa extra boost for 0.2 of a second would have broken the camels back.  How did the rod fail?  Is it bent or was it a tensile failure?  Or is it too mashed up to tell.  Typically too much cylinder pressure will bend the rod but it will still be in one piece.  Are the rodbolts still intact?  Is the bigend blue?

[cj.surr]

5 hours ago, Adamw said:

I know there were some significant changes made to the limiters in 5.6.7 firmware so I held off replying until I could test your file in an ecu with 5.6.7.  Unfortunately I still see a similar effect where the MAP limit doesnot initiate until the gear shift cut is finished.

Im not sure it there is a reason for it or if it is something that can be improved but I will bring it to @Simon's attention so he can pass your logs and file on to the engineers for a look.  The limiter priorities and how all the limiters interact is very complex and even over my head in the few discussions I have had with the engineers in the past. 

I really do sympathise, but its hard to imagine how 25Kpa extra boost for 0.2 of a second would have broken the camels back.  How did the rod fail?  Is it bent or was it a tensile failure?  Or is it too mashed up to tell.  Typically too much cylinder pressure will bend the rod but it will still be in one piece.  Are the rodbolts still intact?  Is the bigend blue?

Thanks for taking the time to look into this and pass it along. 

I don't know anything yet about the failure except that part of the rod exited the oil pan. 

I was also surprised how close I was to the edge, but the car runs 93 octane (AKI) and direct port water meth. So it's not going to be as knock resistant as E85 or race gas like most people run at these kinds of boost levels. 

In addition, my timing in that 320kpa cell was fairly aggressive considering that I have never attempted to dyno tune it at that level and never expected the ECU to see that cell. It is only about 1 deg less than at 280 kpa. I can be pretty sure that the failure was due to preignition (my best guess) or extreme knock. I will also be testing my injectors and water nozzles to see if that played a factor. However, I don't think it's a coincidence that a motor that has been seemingly perfectly healthy at 270-280 kpa for over two years would completely fail the first time it saw 320 kpa. It was a very short period of time but I think it's completely possible to destroy a rod in 5-10 cycles. 

[cj.surr]

Still hoping to hear from Link on this one... I am feeling left out to dry.

[Simon]

Hi CJ 

The Gear cut takes the higher priority over just about all other limits.

A hard cut on the fuel will be higher priority so if you set the map limit to have the hard cut on then when it then hit the hard limit it would then over ride the gear cut. 

Regards

 

Simon

 

[cj.surr]

42 minutes ago, Simon said:

Hi CJ 

The Gear cut takes the higher priority over just about all other limits.

Clearly, but why? My experience should be a clear example of a reason why boost cut should take a higher priority. As the tuner, this seems like an unreasonable thing to have to assume. Common sense says that the cut that is calling for the highest % cut should take priority. 

I'd rather not do a fuel cut because I have secondary methanol injection and it's slower than ignition cut.

[Stevieturbo]

On 10/22/2019 at 1:11 PM, cj.surr said:

In addition, my timing in that 320kpa cell was fairly aggressive considering that I have never attempted to dyno tune it at that level and never expected the ECU to see that cell. It is only about 1 deg less than at 280 kpa. I can be pretty sure that the failure was due to preignition (my best guess) or extreme knock. I will also be testing my injectors and water nozzles to see if that played a factor. However, I don't think it's a coincidence that a motor that has been seemingly perfectly healthy at 270-280 kpa for over two years would completely fail the first time it saw 320 kpa. It was a very short period of time but I think it's completely possible to destroy a rod in 5-10 cycles. 

Bit silly running high boost, untested cells on pump fuel with aggressive timing ? Ultimately that's what the real problem is here.

 

And a fuel cut will be a lot safer than an ignition cut. It just seems a lot choose ignition cut because it's more likely to make silly banging noises during a cut. But yes, improper ignition can and will destroy shit. Big time.

[cj.surr]

11 minutes ago, Stevieturbo said:

Bit silly running high boost, untested cells on pump fuel with aggressive timing ? Ultimately that's what the real problem is here.

 

And a fuel cut will be a lot safer than an ignition cut. It just seems a lot choose ignition cut because it's more likely to make silly banging noises during a cut. But yes, improper ignition can and will destroy shit. Big time.

Another super tuner looking to shit on my tune for their own ego, awesome. I had a hard limit boost cut at 290kpa and was targeting 270kpa. Why should I anticipate a need to have my timing settings dialed in at 320kpa, a level I didn't want to be at, and shouldn't have been able to get to?

Also wall wetting and secondary injection is a thing, not everybody wants the occasional lean firing that comes with a fuel cut. There is no inherent danger to the engine from an ignition cut.

[Ducie54]

Instead of getting defensive, I would be asking for help to stop it happening again. Plenty of ways to do this. 

[cj.surr]

20 minutes ago, Ducie54 said:

Instead of getting defensive, I would be asking for help to stop it happening again. Plenty of ways to do this. 

I already know multiple ways to keep this from happening again. I could make an aux input that activates a low GP rev limit if MAP is above a certain value. 

My point is that the integrated MAP limit feature is NOT comprehensive, as seen by my experience. I was just hoping for Link to change the MAP limit to actually protect the motor in all scenarios. This way I can continue using the feature and this will not happen to someone else. It is not fair to assume that the tuner would know that MAP limit doesn't work during shift cut or torque reintroduction. The programming oversight cost me thousands of dollars and lots of my time, as well as making me look bad by oiling down the whole track. As well as ending my season. It's not like I'm asking anyone to build me another motor, but a "sorry" would have been in line, in my opinion.

[Simon]

We hate to see any engine destroyed.

What we can certainly aim to do is document the way the limits interact better to try keep all informed.

 

 

[cj.surr]

10 hours ago, Simon said:

We hate to see any engine destroyed.

What we can certainly aim to do is document the way the limits interact better to try keep all informed.

 

 

OK, so to recap this thread, and please correct me if I'm wrong... Due to lack of response on the actual substance of my original post, I am assuming:

A- Link is not disclosing a reason for disabling boost cut during shift cut and torque reintroduction.

B- Link will not be changing boost cut to take priority over all other cuts

 

[Richard Hill]

On 10/22/2019 at 1:11 PM, cj.surr said:

in addition, my timing in that 320kpa cell was fairly aggressive considering that I have never attempted to dyno tune it at that level and never expected the ECU to see that cell. It is only about 1 deg less than at 280 kpa. I can be pretty sure that the failure was due to preignition (my best guess) or extreme knock. 

We always hard code safety into the main ignition table by ramping ignition down quite hard above the targeted/tuned MAP values.  We also ramp fuel up quite a lot in these areas too.  This is before we add any other layers of engine safety.  Belt and braces.

HTH,

 Richard. 

[Stevieturbo]

On 10/31/2019 at 10:02 PM, cj.surr said:

Another super tuner looking to shit on my tune for their own ego, awesome. I had a hard limit boost cut at 290kpa and was targeting 270kpa. Why should I anticipate a need to have my timing settings dialed in at 320kpa, a level I didn't want to be at, and shouldn't have been able to get to?

Also wall wetting and secondary injection is a thing, not everybody wants the occasional lean firing that comes with a fuel cut. There is no inherent danger to the engine from an ignition cut.

Perhaps get back into the real world and use some common sense.

Why should you need to anticipate basic tuning for cells ? Seriously, think about what you're saying.

 

And BS about the "lean firing that comes with fuel cut" 

[Ducie54]

35 minutes ago, Stevieturbo said:

Perhaps get back into the real world and use some common sense.

Why should you need to anticipate basic tuning for cells ? Seriously, think about what you're saying.

 

And BS about the "lean firing that comes with fuel cut" 

Glad I'm not the only one thinking the same thing. 20 times the statistics show it has hit MAP limit, you would of hoped the tuner worked it out before it blew. 

Trying so so hard not to pick this to threads.