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TDI Power Enhancements Discussions about increasing the power of your TDI engine. i.e. chips, injectors, powerboxes, clutches, etc. Handling, suspensions, wheels, type discussion should be put into the "Upgrades (non TDI Engine related)" forum. Non TDI vehicle related postings will be moved or removed. Please note the Performance Disclaimer.

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Old July 8th, 2018, 22:37   #1
Digital Corpus
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Default Why Flatten the Stock SOI Hump?

Sorry, but I'm doing this post remotely and I "can't" be bothered to post a MKIII or MKIV SOI map. However, they're commonly known so I suspect such an image is redundant. Anyhow, to the question...

Why flatten the hump? Even before VAGSuite, now redone and being developed by another individual as EDCSuite (distributed via Facebook btw), it was dogma to flatten the hump @ ~2000 RPM & 10-15 mg/str. Why has this been done?

I'm busy doing iterative logging for test-and-adjusting my GTB1756VK and redoing the N75 map. Having more precise values instead of relying on the min and max duty cycle maps, is preferable in my book. It is common method for some tuners, and I don't fault them as to why they use this method to which I can explain some this logic at a later date; anyhow I digress. What I've seen while logging is that this bump yielded the PID control to consistently open my vanes in this IQ range and then close them up when requesting a higher IQ.

Whether this is only correlation and not actual causation, I suspect it is the latter, which means that the more advanced timing nets more exhaust gasses aiding in spinning up the turbo charger with that hump. Why is the hump removed and the timing retarded instead of raising the retarded section of the map?
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Old July 9th, 2018, 06:59   #2
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I always thought it had something to do with fuel economy at 55ish mph cruise. Maybe that's the american standard for the "highway" mileage number or something. The rest of the map is running a bit retarded to aid in catalyst heating but they wanted to get better numbers to toss on the window sticker. When I did it I'd bring up the rest to the level of the bump rather than bringing it down where everything else was..

Just speculation on my part though.
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Old July 9th, 2018, 12:14   #3
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The more info the better. Thanks for the input. Anyone else with theory or fact?
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Old July 9th, 2018, 14:24   #4
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As above lumps like that will be for a cycle based co2 vs noise vs NOx trade off reason... If you want to flatten it bring the map up to match it and it should give you better fuel consumption everywhere.



Fact is advancing timing makes more diesel noise but makes for more efficient combusion - up to a point anyway.



For fun you could bring the map up all over and see if you get better mpg numbers...



Although actually with R520's you probably don't need as much advance as the original setup as you deliver more fuel in an earlier time of the compression stroke. So the best spot for you might actually be in between the bump and the low areas....
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Old July 9th, 2018, 17:10   #5
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Iím running 100% Diesel HPR from Propel too. From the few non-paywall research papers Iíve been able to find, the increase cetane rating can aid in reducing ignition delay by 0.5-1 ms. However, when I ran the conversion to crank degrees, that seemed rather high. Iím thinking that Iíll need a PCP sensor to establish appropriate timing adjustments, if needed.
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Last edited by Digital Corpus; July 10th, 2018 at 01:11. Reason: Damn you auto-correct
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Old July 9th, 2018, 19:32   #6
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Old July 10th, 2018, 14:39   #7
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Quote:
Originally Posted by Digital Corpus View Post
Iím running 100% Diesel HPR from Propel too. From the few non-paywall research papers Iíve been able to find, the increase cetane rating can aid in reducing ignition delay by 0.5-1 ms. However, when I ran the conversion to crank degrees, that seemed rather high. Iím thinking that Iíll need a PCP sensor to establish appropriate timing adjustments, if needed.

Adjusting timing in that area you will be safe just using a dyno and tuning SOI to give the best torque for a given fuel quantity in that region.


A good method of tuning this on the fly is add a variable resistor to your coolant temp sensor circuit. Then you can manually set coolant temp to reflect any number you want. Then flash in a tune where you set SOI timing correction via coolant temp to allow a range of coolant temps to give you a range of main timings in one go,



At full load you need to worry about the peak cylinder pressures getting too high.
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Old July 11th, 2018, 07:25   #8
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Originally Posted by m1ketdi View Post
A good method of tuning this on the fly is add a variable resistor to your coolant temp sensor circuit. Then you can manually set coolant temp to reflect any number you want. Then flash in a tune where you set SOI timing correction via coolant temp to allow a range of coolant temps to give you a range of main timings in one go,
I really like this idea

I was dreading needing to reflash a hundred times to get the injection timing set correct throughout the maps. This way I can just adjust it with the cruise control set on flat ground, when it reads the lowest IQ for the set speed it's at its most efficient timing.
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Old July 11th, 2018, 09:02   #9
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or just use VCDS adaptation channel 4 to adjust timing till it suits your purposes, then adjust the tune accordingly (ALH of course)
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Old July 11th, 2018, 14:29   #10
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http://www.ecuconnections.com/forum/...sistor#p133025
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Old July 11th, 2018, 16:56   #11
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m1ketdi, thanks for the notes to make things easier, though obviously it takes time to make fine tune adjustments. I’m on an MSA15.5 ECU so I still only have one timing map. I did loose a bunch of data due to no backup and a reformat (my bad, all the way) but it’s caused me to go through things again and I’m noting a lot of EDC15 tunes that have a data dose to fit in an MSA15.5’s memory. I haven’t flashed them and tested them yet, but it was a rather interesting note because of the MSA15.5 supports some of the advanced features in the latter mapping, it’s a nice way to apply some upgrades.

Similarly, I know some on the club had noted better performance (like faster spooling of a turbo) by just swapping out the older ECU for the newer one but keeping the maps the same. Though the precise number escapes me, I do know that there is a voltage divider and a low pass filter with a time 5-RC time constant of ~160 ms. If there is other heavy handed filtering in the hardware, this can account for some of the transient differences.
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Old July 12th, 2018, 04:22   #12
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Originally Posted by Digital Corpus View Post
...that the more advanced timing nets more exhaust gasses aiding in spinning up the turbo charger with that hump.

How does more advanced timing create more volume of exhaust to spool the turbo sooner?
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Old July 12th, 2018, 14:39   #13
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Quote:
Originally Posted by Digital Corpus View Post
m1ketdi, thanks for the notes to make things easier, though obviously it takes time to make fine tune adjustments. Iím on an MSA15.5 ECU so I still only have one timing map. I did loose a bunch of data due to no backup and a reformat (my bad, all the way) but itís caused me to go through things again and Iím noting a lot of EDC15 tunes that have a data dose to fit in an MSA15.5ís memory. I havenít flashed them and tested them yet, but it was a rather interesting note because of the MSA15.5 supports some of the advanced features in the latter mapping, itís a nice way to apply some upgrades.

Similarly, I know some on the club had noted better performance (like faster spooling of a turbo) by just swapping out the older ECU for the newer one but keeping the maps the same. Though the precise number escapes me, I do know that there is a voltage divider and a low pass filter with a time 5-RC time constant of ~160 ms. If there is other heavy handed filtering in the hardware, this can account for some of the transient differences.

I had't really thought too much about the different ecu's and how this mod would work. I'll take a look at what I have on my computer as I am sure that even msa15.5 will have some timing corrections based on coolant temp in there.
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Old July 12th, 2018, 21:49   #14
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How does more advanced timing create more volume of exhaust to spool the turbo sooner?
Simple question, but very complicated answer. Many a scientific research paper is regarding diesel injection timing and its effects. I don't understand it well enough to provide a competent answer aside from that there is a sweet spot and advancing or retarding from this point will reduce the efficacy of spooling the turbo. This sweet spot isn't necessarily the same one as emissions optimization either.
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I had't really thought too much about the different ecu's and how this mod would work. I'll take a look at what I have on my computer as I am sure that even msa15.5 will have some timing corrections based on coolant temp in there.
Some might, but the FA, GL, and GH ones don't have more than one timing map per codeblock, generally. I'm trolling through those I can find to verify this.
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Old July 13th, 2018, 05:23   #15
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Quote:
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...I do know that there is a voltage divider and a low pass filter with a time 5-RC time constant of ~160 ms. If there is other heavy handed filtering in the hardware, this can account for some of the transient differences.
Wow, I hadn't considered the "improved response" with a later ECU was due to hardware smoothing on the output drivers. I had assumed it was due to faster output sampling or more processing power!

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