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Thread: 1.4t LTFT help

  1. #1
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    1.4t LTFT help

    Hey dudes, I would like some help with my LTFTs. So far to make power all I have done is command more torque above high throttle percentages and adjust things like boost and torque limits that got in the way. Of course I have enabled PE too and it works good. I have a wide-band. This has worked good so far, but I want to get more advanced with my tuning. I see some people tune with wide-bands and some tune with LTFT. So, if my wide-band is showing good readings all the time, should I even worry about the LTFTs? They are very extreme in the negatives with a few outlier positives. Not sure if this matters, but I have not touched anything related to VE, open loop, cam timing or MAF. I am trying to figure out where to start with that stuff via old threads. Still reading through a few that I found. Thanks for your help.

    I tried to attach my log and tune, but the attachment manager keeps failing to open. I will try again later.

  2. #2
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    Log file. Only difference from the tune file is I enabled no lift shift. As you can see by the name, I put some pre load on the actuator trying to hold boost in the upper rpm. Did not change anything, so I dont know whats going on there.
    Attached Files Attached Files

  3. #3
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    ltft are not rich they are lean meaning positive not negative. You only have 1 bank and its bank 1 not bank 2 if thats what you are looking at. The wideband while in closed loop should read normal because the ecm is using fuel trims to control stoich. The only way to tune with a wideband is to put the vehicle in open loop and tune against the afr error % otherwise just use fuel trims and adjust the fueling map for idle and driving. You cant tune maf while ve in enabled and same same the other way around otherwise youll get conflicting data. You need to tune each system by itself by going maf only and then ve only and bringing the fueling in line.

  4. #4
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    I have noticed that the boost is going down over 5k rpm because the actual desired boost is going down. So, its definitely not mechanical. I am trying to figure out whats causing that. Been changing a few things each time and logging to see if it made a change, if not I do not save the tune. I found that reducing the timing advance above 5k helped a little, but it did not get better as I took more out, so I left it at my first change. Same thing with the airmass. I have started messing around with the throttle blade psi drop. It was all 0 default. The hpt note says set at 20-40kpa for good responsiveness, so I did that. I started with setting it at 20 all over, and that helped the desired boost stay up over 5k, and 40 seems to be good, but 50 or more causes me to hit boost cut at 5500rpm. So I am gonna leave it at 40.

    As for the original topic of LTFT, TCSS07.. yes I only have one bank and I am looking at bank 1. My question is this though: being that I tuned this the way I have, where its pretty much running entirely stock until I floor it, is it even necassary to mess with all that stuff? The only thing I am concerned about is, am I losing much potential power by not having my MAF, or VE, whichever affects this, adjusted for my intake and exhaust? Watching the wide-band while I drive shows me that the AFRs are pretty much dead on with the stock tune under normal circumstances.

  5. #5
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    well youre going to want to get the trims as close to 0 as you can which will make the car run better making sure the fueling is correct. In closed the loop the wideband will read spot on because the ecm is using trims to keep it at stoich but that doesnt mean the fueling is correct as your log indicated its lean but falls within the "ok" parameter that gm has set so it hasnt set a light and without you posting a tune file we cant really offer any help about the boost issue as we cant see how you have it set up but also keep in mind that the stouck turbo doesnt make much power if at all above 17psi

  6. #6
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    Sorry, did not realize that the tune was not attached the first time. Here is my latest tune with the 40 kpa throttle blade pressure drop. I know the file name says psi but its in kpa. I guess I need to read up on calibrating the MAF and doing the whole closed and open loop thing because right now I have no clue where to even start lol. As for the stock turbo not making power above 17psi... I do not know where you got your information but that is simply not true. The pretty widely accepted "sweet spot" of boost on the stock turbo is 20-22psi. I can also say that even with my probably pretty crappy tuning, I notice an increase in power on the old butt dyno from 18 to 22psi. Personally I want to stay as close to 22psi as I can.
    Attached Files Attached Files

  7. #7
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    Well then maybe things have changed for the stock turbo but its a tiny guy and from what zzp says over 17psi didnt amount to any more power but this was years ago so idk tbh. Youll get a little higher torque bump from the boost spike but all youll be doing to increasing the iat2 temps so unless you have concrete data showing the increase in power to justify the higher boost ill choose not to stress it out like that. heres a link i used when i got started out with this type of ecm
    https://forum.hptuners.com/showthrea...-Tuning/page11
    about half way down youll see a post from chris@hptuners

    I dont do open loop tuning i only do closed loop and use fuel trims and for the throttle pressure drop i always kept it at 0

  8. #8
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    Thank you for that link, it was helpful. I have gotta get my wide-band signal run through my EGR before I can really tune the MAF. I did not realize doing that would be basically necessary. As for the boost thing, personally I do not trust anything ZZP says anymore. They have a bunch of idiots working for them, and their customer service policies are horrible. This is my own personal experience talking. But, I do believe that they were using a totally stock intake manifold. Once the massive restriction plates are removed, it is totally different.

    This is off-topic, but do you know how to make the throttle stay true to the accelerator pedal? Or at least cut back to idle throttle percentage when the pedal is not applied? The rev hang is driving me nuts, and I can see in the log that the throttle stays at like 36% and very slowly creeps down, even though I let off the pedal 5 seconds ago.The commanded throttle actuator value is a few percent behind as the RPMs are falling. Once the engine is idling, the commanded throttle value is at about 4% where it is supposed to be, but the throttle position SAE value is still at almost 20%. And the accelerator pedal value is at 20% even while idling, and only goes to 85.5% when floored. The throttle position SAE goes to 83.9% which I read is normal, but the commanded throttle is at 100%. Throw the relative throttle position value in there and it gets even more confusing. You can see all this in the log I posted. I just do not understand why they are all so different all the time. Is there any way I can make the throttle blade directly correlate with the pedal, or at least only be a few percent off, without putting a cable throttle in?

  9. #9
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    I couldn't agree more with you about them and also that was what I read about like 5 years ago. I also feel they have dropped off a bit as a whole but that's a different conversation lmao. But it still is a tiny turbo and with gm having issues with the turbos stock as is id rather not push the little guy to hard but if the turbo holds the boost and temps stay decent I guess press on lol. Now if you're talking about the bigger v2 or v3 that zzp makes thats different. my coworker at work has the v2 and i tuned him to 23psi and it rips pretty good. But yeah you need to get that logging or youll have to just make adjustments based off rpm which can get a little tricky but not undo able.


    i dont think youll ever get the app and tps to match up on these cars tbh. i always just logged the peal and tps sae. id maybe try to zero out the throttle pressure drop since that adds map and could be holding the throttle open during the coastdown. when i had my 15 1.4 turbo i kept it at 0. pm and we can talk a little more about it

  10. #10
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    Well as much as I?m peeved at zzp, they are the only ones making cams for the 1.4.. Im just kinda seeing what the stock turbo can do, and when it starts to give out Im gonna make my own manifold and put a different turbo on it, like an audi 1.8 or Evo turbo. This cars mods are just cheapo diy stuff for fun and experimentation purposes. Adding the wide-band into the egr will be my project for this week hopefully.

    The throttle thing though, I got rid of the throttle pressure drop stuff. Got the boost to stay up by messing with the tables Chris mentioned in that thread you linked me to. Still hangs like crazy, it always has. I was playing around with some of the idle related tables this evening, Im gonna go try them out here in a little bit, so Ill let you know how it goes. If that doesnt work, I saw one guy mention on another thread that moving the vacuum line to the bpv from in front of the throttle blade to before it can help. I guess the theory is the bpv sees vacuum faster, opens faster, and dumps the boost so it doesnt hold the throttle open and or keep feeding into the engine...? Worth a shot if my tables dont work

  11. #11
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    My tables did work. Its not perfect, but its definitely better. Check it out. I basically disabled all of the fancy idle stuff by zeroing out the tables and maxing out the enable/disable values. Of course as soon as I opened my mouth about keeping the boost up with those other tables... I start hitting a boost cut around 5500rpm again. You can see that in this log too. I will have to work on that. Once I get my tuning down on my car, I can basically just transfer the tune to the VW based rail buggy I am starting to build. It will be powered by a 1.4t of course. I will just have to make some minor changes to suit off-road use better, such as bringing the boost on early for torque purposes.
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  12. #12
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    Did you wire your wideband through the egr, or do you have a pro model? I can?t find a Sonic E78 ECM pinout, just trucks which don?t have egr

  13. #13
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    sorry been crazy few days. i had the mpvi1 pro unit so i just hooked it up to the mpvi unit to read the aux input

  14. #14
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    Egr won't work as we don't have one and ac won't work either. I have been down those paths. Use a serial to usb cable. Check easy, and no offsets to worry about. Here are some things that may help.

    https://www.cruzetalk.com/threads/ho...4/post-3256129

    https://www.cruzetalk.com/threads/ho...8/post-3255299

  15. #15
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    Again, just get a serial able and do it like in the link. It super easy. It literally cannot get easier or cheaper than that. 10 minutes and 20 bucks will save you much anguish.