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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N54 Turbo Engine / Drivetrain / Exhaust Modifications - 335i > Flash vs Piggyback - Where we stand today.



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      01-23-2011, 10:57 AM   #23
Joshboody
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Originally Posted by shiv@vishnu View Post
Just as a note, I have yet to see evidence that cylinder 6 is the most knock prone. Nor do I recall seeing any failed engine tear downs suggest this to be fact either. Besides that, we just use Ignition Advance on cylinder 1 as a general reference for tune aggression relative to the stock tune. Not as a specific value to apply a discrete offset upon. So not monitoring each individual cylinder for knock isn't necessary unless you have a "bad" cylinder. But I'd say the rattly noises, copious oil consumption, loss of power, smoky exhaust and various DME codes would probably be the first indicator of such a problem.
I am still very curious about aggression. From above I understand that procede reads cylinder 1 advance... not retard, or knock activity... but the actual timing advance for cylinder 1 from the DME. From this DME advance target, the aggression level is created (along with other non-ignition factors). So there is an optimal ign target and aggression is scaled from there? If this was the case the aggression would be calculated by how many times optimal timing can be reached throughout the rpm range.

How about reading the actual knock sensors activity?
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      01-23-2011, 11:04 AM   #24
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Originally Posted by Clap135 View Post
Cobb: I have yet to see any stage 1 car knock, the timing curve, and the dme ability to raise timing is set below the knock point. Which is alot better imo.
All these logs are in the winter. Once the air thins, we will see knock from Cobb.

From my reading of the threads, Cobb did not state that there are multiple load based ignition maps, or any weather corrections. My understanding is one map based on load... if this is the case be prepared for some knock caos.
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      01-23-2011, 11:05 AM   #25
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Quote:
Originally Posted by Joshboody View Post
All these logs are in the winter. Once the air thins, we will see knock from Cobb.

From my reading of the threads, Cobb did not state that there are multiple load based ignition maps, or any weather corrections. My understanding is one map based on load... if this is the case be prepared for some knock caos.
Simply look at timing, even if boost goes up during hot months, the cars still will not knock with that timing curve.
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      01-23-2011, 12:05 PM   #26
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Originally Posted by Joshboody View Post
I am still very curious about aggression. From above I understand that procede reads cylinder 1 advance... not retard, or knock activity... but the actual timing advance for cylinder 1 from the DME. From this DME advance target, the aggression level is created (along with other non-ignition factors). So there is an optimal ign target and aggression is scaled from there? If this was the case the aggression would be calculated by how many times optimal timing can be reached throughout the rpm range.

How about reading the actual knock sensors activity?
It's pretty easy to calculate relative knock activity by just monitoring ignition advance. Since the DME perceived load is consistent regardless of what boost pressure the car actually runs. Which means that apart from some basic IAT/Coolant compensations (which we account for), the DME will target the same ignition advance values time and time again. You can confirm by simply running race gas and logging CAN DME Advance. Regardless of actual boost (within the physical knock threshold) or gear, timing logs will be repeatable. With repeatable set point, determining relative knock is just a matter of subtraction calculated set-point minus actual DME CAN advance. This is why aggression goes to 0.0 (or close to it) when running a pump gas tune on race gas.

And you are correct. If a flash tune is currently targeting ~4 deg in the midrange and ramping up to 11 deg by redline AND only running 13-11psi on 93oct in the winter, you aren't going to see knock. Not by a virtue of anything other than the fact that the tune is very conservative. You'd see the same thing if you run a Procede at 11psi with 100% ignition correction.

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Originally Posted by packinDSS View Post
Shiv', do most car manufacturers ecu target load like ours? Or is this a rarity. Did BMW ecu always do this way? Even on naturally aspirated vehicles? I never heard or read this when I was in the supercharged cobra forums. Im just curious.
Like BMW, most modern turbo engines target based boost target upon calculated (or if equipped with a MAF, measured) mass airflow readings. At the OEM level, after safety/emissions concerns, the ultimate goal to is to make the claimed power output. And do so in a variety of conditions. Which is why some manufacturers go so far as to state XBHP up to Y' of altitude (like Audi). Which is why they also design turbo hardware that has enough overhead to accommodate these goals (ie, running more boost at altitude). All this is nice and achievable if:

-You aren't concerned about making more power when conditions are good.
-You aren't concerned that the DME is trying to target the same power output wen condition are bad.
-Load requests are always within the reach of turbo system capacity (ie, the DME is NOT targeting 16psi at 7000rpm when it is only capable of supporting 13psi)
-Load requests don't exceed what the engine can support given allowable knock threhsolds (ie, supporting reasonable boost pressures on pump gas).

All these criteria of easily met on a bone stock car that runs 6-9psi depending on conditions. Double that boost pressure and all bets are off.

shiv

Last edited by shiv@vishnu; 01-23-2011 at 12:30 PM.
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      01-23-2011, 12:18 PM   #27
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Thanks Myst and Shiv. Good starting point. A couple more points that I would add or suggest:

Wastegates. I don't think there is a big variance in the actual mechanical wastegates. It seems pretty strange to me that "some would be soft and others would be hard, etc." I would suggest that the increased DC required by some vehicles is a result of a minor boost leaks in the IC piping or core. Those with aftermarket FMICs should leak test them - submerge in water and pressurize before installing. I've had two personal experiences where brand new ICs required welding to seal. The stock plastic end tanks also seem like likely leak points to me.
With all due respect, there is variance in wastegates. This is fact. You can test this yourself by vacuum testing wastegates on different cars. They will not all share the same cracking pressure. This is also one reason that some wastegates rattle. And why some rattle more than others. And why fixing this rattle involves running more DC in some cars and less in others. Let's not forget that some techs eliminated rattle by adjusting wastegate stiffness and setting it to factory spec. Suggesting that intercooler leaks is the case for all these variances doesn't seem very reasonable given the long history of mechanical wastegate issues with our cars. Not to mention that BMW released a few wastegate designs/part number.

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Timing: The Procede is a very advanced piggyback. It does more than any piggyback I've ever heard of by a mile. That said, it is limited to offsetting the stock curve. This is reliable but only if the stock curve is stable.
And it is stable. Like any computer, if you feed in the same inputs, you get the same outputs.

Quote:
I don't believe the Procede will ever effectively add more timing that the DME will. My guess is that the car would run 12 deg on race gas/meth with the proceded adding 2, subtracting 2, or nothing at all - the DME will add timing until it knocks slightly.
I don't follow.

Quote:
The danger here comes with the AP and ATR. If a user adds timing to the DME curve it will continually try to hit it and may damage the motor.
The potential for damage exists on any user-tunable platform. The AP is no exception.

Regards,
Shiv
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      01-23-2011, 12:28 PM   #28
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On the AP, boost overshoot, throttle closure isn't an issue whatsoever since the load index itself is not affected. The tune trims throttle, dumps boost, whatever it needs to do in order to achieve the load target.
This is one misinformation. The reaction to boost overshoot may or may not be able to be corrected, and it also affects driveability. It is not desired.
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      01-23-2011, 12:31 PM   #29
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Actually, people who experience overshoots/throttle closure say that it does no affect driveability. Cobb already stated, they can remove the throttle closure issue if users request it. This will probably an option with ATR if I had to guess
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      01-23-2011, 01:05 PM   #30
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Actually, people who experience overshoots/throttle closure say that it does no affect driveability. Cobb already stated, they can remove the throttle closure issue if users request it. This will probably an option with ATR if I had to guess
Throttle closure is necessary to control overboost conditions in Cobb's flash so why would they allow something fundamentally required by their flash to work properly easily removed on their customer's request?
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      01-23-2011, 01:06 PM   #31
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Throttle closure is necessary to control overboost conditions in Cobb's flash so why would they allow something fundamentally required by their flash to work properly easily removed on their customer's request?
Because once ATR comes out, you are responsible for your car, not them. keep in mind, cobb is not out there to push anything with ots maps.
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      01-23-2011, 01:47 PM   #32
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I suggest you do some more reading!
I could do more reading about piggyback v flash tunes but I have spent at least 10 hours per week over the last 4 years.
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      01-23-2011, 01:48 PM   #33
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I could do more reading about piggyback v flash tunes but I have spent at least 10 hours per week over the last 4 years.
I don't know where you've been reading but there is no way the jb3 is superior to the Procede.
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      01-23-2011, 01:49 PM   #34
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Quote:
Originally Posted by Joshboody View Post
All these logs are in the winter. Once the air thins, we will see knock from Cobb.

From my reading of the threads, Cobb did not state that there are multiple load based ignition maps, or any weather corrections. My understanding is one map based on load... if this is the case be prepared for some knock caos.
I have GIAC Stage 2 and I ran it with stock intercooler for 2-3 runs (55 celsius IATs) and while with 91 octane I have seen some timing pull (not sure it was knock - I couldn't feel it and no code was registered in the car), once I put 93 octane I have never ever seen timing pull, let alone any knock events.

I would say a good tune will NOT knock.
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      01-23-2011, 01:51 PM   #35
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I don't know where you've been reading but there is no way the jb3 is superior to the Procede.
Must be n54tech
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      01-23-2011, 01:57 PM   #36
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I don't know where you've been reading but there is no way the jb3 is superior to the Procede.
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Originally Posted by fisherbln View Post
Must be n54tech

I mean this with all due respect.
Guys can you please keep the fanboyism down in this thread. This thread so far is one of the best I've read this week. Everyone has their favorite tune, but start a different thread if you guys want to pump camps.
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      01-23-2011, 01:58 PM   #37
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Because once ATR comes out, you are responsible for your car, not them. keep in mind, cobb is not out there to push anything with ots maps.
Very much true, this is the main feature I'm waiting for because I have a cobb tuner in Chicago that I've used before that does great work in the subbie world. Plus they have an AWD dyno which helps.
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      01-23-2011, 02:10 PM   #38
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Actually, people who experience overshoots/throttle closure say that it does no affect driveability. Cobb already stated, they can remove the throttle closure issue if users request it.
I am not sure if there is much of an "issue." I know Alan had some throttle problems, but I believe four of us have posted AP logs and three show none or little throttle correction activity. As I look my logs over, timing and WGDC are locked step-for-step doing what they do best.
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      01-23-2011, 02:10 PM   #39
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kitten blood>sstt>jb3+jb+>jb4<=,giac,cobb<JB3<Procede IMO
Fixed

and yes, that makes more sense that your post.
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      01-23-2011, 02:35 PM   #40
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I mean this with all due respect.
Guys can you please keep the fanboyism down in this thread. This thread so far is one of the best I've read this week. Everyone has their favorite tune, but start a different thread if you guys want to pump camps.
+1. No tune is superior to another. Each have positives and negatives. Stating that one tune is better than another is stupid and only results in the next tuner war thread. Seen it 79767987080764 times already.
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      01-23-2011, 02:49 PM   #41
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Originally Posted by tscdennab View Post
I have GIAC Stage 2 and I ran it with stock intercooler for 2-3 runs (55 celsius IATs) and while with 91 octane I have seen some timing pull (not sure it was knock - I couldn't feel it and no code was registered in the car), once I put 93 octane I have never ever seen timing pull, let alone any knock events.

I would say a good tune will NOT knock.
If there's 1 2D load based timing map you'll either see knock or very conservative advance.
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      01-23-2011, 04:54 PM   #42
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Originally Posted by tscdennab View Post
I have GIAC Stage 2 and I ran it with stock intercooler for 2-3 runs (55 celsius IATs) and while with 91 octane I have seen some timing pull (not sure it was knock - I couldn't feel it and no code was registered in the car), once I put 93 octane I have never ever seen timing pull, let alone any knock events.

I would say a good tune will NOT knock.
That was knock. But there are different degrees of it.
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      01-23-2011, 06:54 PM   #43
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Just curious, How would one go about detecting knock?
How does the DME detect it? Do all tunes rely on just the DME to predict knock?
I know some tunes are retroactive and some proactive when it comes to timing adjustments, just curious how the system goes about detecting/prediction knock.
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      01-23-2011, 06:59 PM   #44
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Just curious, How would one go about detecting knock?
How does the DME detect it? Do all tunes rely on just the DME to predict knock?
I know some tunes are retroactive and some proactive when it comes to timing adjustments, just curious how the system goes about detecting/prediction knock.
The knock sensor.
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