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Flash vs Piggyback - Where we stand today.
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01-22-2011, 06:50 PM | #1 |
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Flash vs Piggyback - Where we stand today.
After observing more AP logs and reading more into load targeting versus directly controlling the wastegates, I am believing that the differences are a matter of execution.
The AP doesn't target boost levels, it targets a load index across the RPM range, which in most cases is around 13psi tapering to 11 at redline. Depending on ambient conditions (elevation, IATs, barometric pressure etc.) the car will trim throttle, reduce or increase boost as necessary in order to achieve the said load targets. 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. If I am not mistaken, the argument from the flash camp is that this method of targeting allows the full utilization of the feature set of the DME. This is both positive and negative in a way. Positive for those who want consistent performance given the conditions (road racing) versus those who want to reap the benefits of lower DA, colder ambient conditions, etc by targeting boost. In regards to timing, EVERY single AP log I've seen from Clap or Alan show a spot-on timing curve (2 degrees at low RPM ramping to about 10 degrees at redline) which in my opinion means the curve as designated by Cobb is spot-on for the conditions, if not a little conservative. Now how does this relate to the Procede? Since the Procede has direct control over the wastegates and the subsequent boost targeting, it does not target a load index; it targets boost, while offsetting the crank position sensor to reduce, or soon, increase timing over the stock ignition set point. Offsetting the crank position sensor (AKA CPS offsetting), in its current form, allows manipulation of ignition advance, following the stock curve. I am not certain if it is possible for CPS offsetting to target a specific timing curve like the AP does at this time. The argument from the piggyback camp shows that it is more beneficial to directly control the wastegates, instead of trimming throttle or allowing boost overshoot events in the first place. As we've seen on the various AP logs, the logs are not consistent across the board when it comes to boost. One overshoots, one has major oscillation issues, and one is spot-on, ironically, with full bolt-ons on a map not intended for them. In this regard, Shiv's statement that no two wastegates are built equal appears to be a valid one. Although Cobb acknowledges the overshoot issues are something that need to be addressed, and the fact throttle trimming is less than ideal, both instances do not appear to affect the smoothness or drivability of the Cobb AP, since the boost is being dumped pre-throttle body to achieve the targeted load index. The Procede beta maps that are currently out for testing incorporate a new level of control that was only recently discovered, which opens up a new possibility in regards to power gains. Shiv can chime in regarding the specifics if he wants. In regards to the JB4, the recent addition of CAN access and direct boost targeting is much welcomed. Previously, the JB3's mapping was more a multiplier algorithm on top of stock boost, which is why we saw inconsistent boost levels and curves in a multitude of conditions, all else equal. The JB4 has the most aggressive timing curve out of all three of the solutions presented, as it is attempting to target 10 degrees in the midrange ramping to 14. The challenge we are faced with, especially in the case of a freshly installed JB4, is the car will not be able to achieve the targeted ignition set point, and thus will result in knock, still attempting to ramp to the targeted ignition set point after the knock event. Being that this car has a highly intelligent DME and a STRONG block to withstand repeated knock events, the DME will eventually recognize this, and less aggressively ramp ignition after a knock retard event. In my opinion, a freshly installed JB4 should be placed on a very conservative boost level initially, as knocking at 14psi is far worse than knocking at say, 11-12psi on pump gas. Either way, allowing the DME to correct ignition advance in a reactive fashion is far from optimal. In my honest opinion, running methanol injection at a modest 15-16psi boost level with proper failsafes on this tune would make the timing argument a bit less relevant. ALL of this information may be obsolete when the Procede tuner software and Cobb ATR come out, allowing those with tuning knowledge to maximize the potential of our N54 motors. As I stated before, I have ZERO tuning experience on any platform. I am simply trying to put all the information in one post I've gathered from logs and discussing with more knowledgeable folks such as Clap135 and others in this community. Please feel free to correct any misinformation I may have provided in this post.
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Last edited by themyst; 01-23-2011 at 09:13 AM.. |
01-22-2011, 06:51 PM | #2 |
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Good info. This thread was useful for a bit: http://www.e90post.com/forums/showthread.php?t=475789
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01-22-2011, 06:55 PM | #3 |
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nice information
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01-22-2011, 06:55 PM | #4 |
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Forgive me, I have too much time on my hands lately. With my car in the body shop, I feel like a soccer player with a broken leg.
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01-22-2011, 11:57 PM | #5 |
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Good info Myst. Thanks for taking the time to spell it out for some of us. I'm a tune sampling whore and I have no problems with it. My car has been knocked in an accident as well as in the engine - I'm sure that if it could talk it would moon me and and flip me off.
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01-23-2011, 12:50 AM | #7 |
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In this forum: People freaking out over the smallest details as they attempt to identify the best tune capable of extracting the most power on a white, black, blue, silver or grey car on a Sunday morning at 3:00am running on pump gas with the most and least-relevant bolt-on mods available.
Reality: Any one of the tunes will yield the same result. You don't mind driving right off the compressor map, right? Solution: "Upgraded" stock turbos featuring ported turbine housings, clipped compressor wheels and the same welded manifolds are available for the low, low price of $4199. |
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01-23-2011, 01:29 AM | #8 | |||||
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Themyst-- Great work collecting all that info. I just added my 2 bits in below...
Quote:
Like a flash, the Procede establishes a boost target which its PID boost control system targets, trying to keep error (target boost - actual boost) to a minimum. Whereas the DME (stock, Cobb, GIAC) defines the boost target based upon achieving reasonably constant airflow (ie, more boost in hotter conditions when air is thin, less boost in colder conditions when air is desnse), the Procede defines it's target boost based upon basic tuning fundamentals (ie, the engine can happily run more boost on a cold night but less boost on a hot summer day). Besides intake air temp (IAT), other contributors to Procede boost target calculations: -Coolant Temp -Oil Temp -Historical knock activity -Barometric pressure Quote:
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01-23-2011, 02:10 AM | #9 |
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@Shiv - Regarding the V5 beta maps, will the ignition advance parameter be re-scaled to accommodate the ability to advance ignition when conditions allow? e.g. meth/race.
@Cobb - In your Stage 1 OTS maps, are you changing the tables of any features not accessible by any piggyback? e.g. VANOS One question went unanswered from all parties involved however; is it possible to monitor the knock activity of the hottest cylinder, which seems to be Cylinder 6? From my understanding, both piggies and even the AP are monitoring Cylinder 1 in their respective datalogs. After finding this bit of information out, I think many of us would feel a lot safer monitoring the hottest cylinder for knock activity.
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01-23-2011, 02:32 AM | #10 | |||
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01-23-2011, 02:56 AM | #11 |
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Shiv - I guess my direct question was how many degrees are we meth guys going to be able to advance beyond the stock ignition set point? 4-6 degrees over pump gas is so vague, as some of us run that much more ignition over pump gas on the stock set point.
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01-23-2011, 03:07 AM | #12 |
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About 2-3 degrees beyond stock advance set point. Worth pretty big gains in the 5000-6000rpm when octane permits.
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01-23-2011, 07:19 AM | #13 |
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01-23-2011, 07:37 AM | #14 |
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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.
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01-23-2011, 08:38 AM | #16 |
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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. 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. The fact that the DME is still in control is a good thing as it can still pull timing from knock. The AP actually sets the desired ignition advance. COBB apparently has chosen to pull a little timing to back off of the knock threshold. That's a typical thing to do when increasing boost. The DME is very good at monitoring knock and the factory curve adds more timing than it should and relies on the knock sensor to pull it back slightly. This is the best for emissions and mileage but could be potentially damaging with a lot of boost. This was shown when cp-e tested their car on a 50/50 mix of gas/e85. That is plenty of alcohol to prevent knock and yet when adding more than a couple of deg of timing the car would knock. The knock monitoring that the DME is capable of and uses is why the JB3/4 is still in operation today. 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. 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. Load/boost: Nice job here myst. The only thing I would add is that the AP may have trouble at higher boost as the load for a FBO car running 18 psi is probably not defined in the tables. In that case it will require development - actually programming the values for cam timing, ign timing, fueling, injection points, injector duty cycle, vanos operation, throttle operation, wastegate, etc. That will likely take a lot of time and will be aided by simple extrapolation of existing values but there is much danger here in that at those load levels knock can do a lot of damage. Get it right and nothing will be faster. Get it wrong and you could destroy things quick. Giac seems the most advanced here. I'd be damn scared to push things as a privateer with ATR in the 16+ psi range without an engine dyno, 6 egts, 6 widebands, and a hell of a knock amp - all of which I believe COBB has at it's disposal - ref GTR. The procede has an easier time here because it lies to the ecu and offsets some of the DME lower load values to safely run high boost. Because the AP has full command of every value it may make more power and be smoother, better driveability ultimately but this is likely pretty far off. The procede is also more likely to be able to handle upgraded turbos sooner than the AP. Lastly I really like the ability to change the functions of the dash - boost for fuel, etc. I'm not sure how the AP can compete here. It might be worth Shiv's time to develop a a product that could implement that functionality for the flash guys. |
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01-23-2011, 09:06 AM | #17 | |
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From Audi-VW to japanese as Lancer or Impreza, to turbo diesel engines! |
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01-23-2011, 09:25 AM | #18 |
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boom,
Very nice! I agree completely!
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01-23-2011, 09:30 AM | #19 | |
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My personal opinion is, we are close to maximum power levels on the stock turbos today, regardless of delivery format. If Cobb's stage 2/3 maps and ATR prove significant gains over what the Piggybacks bring to the table at the same boost level, then we'll have an exciting 2011. If there's no significant gain, I don't believe the piggy vendors will have anything to worry about. I, for one, don't want to switch tunes for a third time. I love the way progressive meth works on either piggyback, and sure as hell would not want to experiment with a wastegate bypass or monitoring a flow gauge constantly to compensate for a lack of this feature on any flash tune. There are certain points not mentioned in the original post, as I drew this up with the goal of Clap135 not tearing me to shreds
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01-23-2011, 09:38 AM | #20 |
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Here are some fun facts based solely on data:
Piggyback, simply do not offset timing enough not to knock. They all knock, some more than others. 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. Proof: I have yet to see a procede/jb3 car run 0-2 degree down low at 13psi Onto the power argument: Procede and autotuning maps, these maps will make more power sometimes, and knock others Cobb: These OTS maps will generally make the same power, sometimes less, however won't knock. Max power potential: This is where it matters for me. Every piggy back out there is made to work on a wide range of cars. If you are beta testing things, you will quickly realize that some things work on some cars, but not on others. It is the end tuners responsibility to sacrafice some things so his tune works on a wide range of cars. ATR: The only car I have to worry about satisfying is my own. Simply put that will make it faster, safer, more responsive, more dialed, whatever you want to call it, than any autotuned car that uses logic meant for 1000's of cars. |
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