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Thread: Switched to 2 Bar OS, now car doesn't want to start

  1. #1
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    Switched to 2 Bar OS, now car doesn't want to start

    So I got my VE dialed in without the boost--car ran great. I added back everything that I had disabled except for the MAF and created new tune with 2 bar OS. Followed the directions on a video on setting up expanded VE table, spark, PE and Boost Enhancement as suggested. Installed my 2 bar MAP sensor and connected the supercharger (bypassed it during the 1 bar VE tuning).

    Did the "Write Entire" as instructed. When I attempted to start the car, it didn't want to start. I finally got it running by holding the throttle open a little but it ran very poorly as if it was extremely rich (smoking also). Put it back to the previous tune (Write Entire again) and it cranked up and ran fine. Went back and looked at the VE table in the 2 bar tune and the lower half was exactly as the original tune which I had copied over. I see the cranking VE tables but they are identical in both the original and 2 bar tune. Did not modify them at all. 2 bar boost tune.hpt What am I missing?

    Attached is a copy of the 2 bar tune if I can figure out how to do this.

    Thanks



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  2. #2
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    Did you confirm the map linear and offset to you sensor?

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    Nothing jumps out at me, post your 1 bar file where you dialed in the VE where it ran fine for comparison.
    It doesn't have to be perfect, it just needs to be done in two weeks...

    A wise man once said "google it"

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    Tuning Addict blindsquirrel's Avatar
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    So do you not have injector data, or is it just set up wrong? (flow rate is flat = referenced fuel system, offset is sloped = returnless fuel system)

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    Attached are 2 tunes: VE Tune Final is where I was tuning the VE with all MAF, STFT, LTFT, COT, DFCO disabled and EQ ratio set to 1.0. On the second tune, I added everything back except the MAF. I didn't drive the car after putting everything back, but it cranked and appeared to run ok at idle.

    BTW, this is a LT1 (gen 2) with Torqhead conversion.

    VE Tune Final.hptVE Tune Final--parameters set back to normal.hpt

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    Quote Originally Posted by gtstorey View Post
    Did you confirm the map linear and offset to you sensor?
    Don't know what that means. This is my first foray into HP Tuners. Have had some experience with the LT1 Edit so I have had a little tuning experience but no expert by any means.

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    Quote Originally Posted by blindsquirrel View Post
    So do you not have injector data, or is it just set up wrong? (flow rate is flat = referenced fuel system, offset is sloped = returnless fuel system)
    Will look around and see if I can find this.

    Thanks to all responding. I thought this would be a relatively easy switch over to 2 bar OS. Looks easy on the video As I stated above, while dialing in the VE (VE Final tune), the car ran perfectly.
    Last edited by David94TA; 03-31-2023 at 03:38 PM.

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    Quote Originally Posted by blindsquirrel View Post
    So do you not have injector data, or is it just set up wrong? (flow rate is flat = referenced fuel system, offset is sloped = returnless fuel system)
    No, it is not returnless fuel system--it is the stock 4th gen LT1 set up

  9. #9
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    There are settings in the tune to change for different MAP sensors (set a linear factor and offset). What is the part number for yours?

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    Quote Originally Posted by gtstorey View Post
    There are settings in the tune to change for different MAP sensors (set a linear factor and offset). What is the part number for yours?
    16040609

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    to me I would suspect a map sensor issue TBH, if its true that the VE Tune Final.hpt file worked fine, you then switched to a 2 bar map sensor and threw in that 2 bar boost tune(which is essentially the same, just with the map sensor scaled to 200kpa) the vehicle should start, run & drive. Thats my non professional diagnosis lol
    It doesn't have to be perfect, it just needs to be done in two weeks...

    A wise man once said "google it"

  12. #12
    Tuning Addict blindsquirrel's Avatar
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    GM 2 bar map sensor Linear and offsets for HPtuners software
    MAP Sensor Linear: 207.66
    MAP Sensor Offset: 9
    Allegedly, according to The Internet. And you know how that can go.

    Located at Engine > Airflow > General - MAP Sensor Linear/MAP Sensor Offset

    'Injector data' is not just flow rate, it's flow rate and min pulsewidth and offsets and short pulse adder. Injectors where all that data is not available do not work well with the stock PCM. They may work fine with aftermarket ECUs where you pick your parts from a drop-down menu.

  13. #13
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    Quote Originally Posted by David94TA View Post
    16040609
    That is an old one. The data I can find online would indicate a linear of 201.9 per 5 volts and an offset of +2.3828. This is based upon data found here; https://sites.google.com/site/sloppy...identification
    If this is correct, you should have a map value in the scanner with key on/engine off of less than 100kpa or 14.5psi.

    You should be able to find this under an airflow tab.

    You also might find a stock file for an early 2000's Grand Prix or Regal to compare this too.
    Last edited by gtstorey; 03-31-2023 at 04:26 PM.

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    Quote Originally Posted by Bill@HPTuners View Post
    to me I would suspect a map sensor issue TBH, if its true that the VE Tune Final.hpt file worked fine, you then switched to a 2 bar map sensor and threw in that 2 bar boost tune(which is essentially the same, just with the map sensor scaled to 200kpa) the vehicle should start, run & drive. Thats my non professional diagnosis lol
    Yes, the above is exactly how it was. That's what was confusing me--I thought the main difference would be the PCM would be reading a 2 bar MAP sensor and the VE tables were expanded.

    Thanks for your input.
    94 TA 385ci T56 9.3cr 224/236 571/573 117lsa Procharger 9lbs boost at 6000 9 inch 3.21 gear

  15. #15
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    Put the old 1-bar sensor back on, change linear/offset back to stock to eliminate the new MAP as the cause. No need to revert to the old 1-bar OS.

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    Will do. FYI, I didn't change the linear/offset settings but the 2 bar OS has different values than the 1 bar OS.
    94 TA 385ci T56 9.3cr 224/236 571/573 117lsa Procharger 9lbs boost at 6000 9 inch 3.21 gear

  17. #17
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    Yes, it auto-populates that when the OS is changed. Doesn't mean it's correct for any actual sensor, they'd have no way of knowing what your linear/offset is. I wish it didn't get changed at all but not much you can do other than make sure it gets the correct values put in.

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    Where do I find those values?
    94 TA 385ci T56 9.3cr 224/236 571/573 117lsa Procharger 9lbs boost at 6000 9 inch 3.21 gear

  19. #19
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    Do you not have a folder where you keep your old tune files for exactly this kind of situation? No stock file for the car? No file from before the 2-bar sensor got installed?

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    Yes I do. But are the values for the 2 Bar tune not different than the stock tune?

    Edit: I did some searching and did find linear and offset values for this 2 bar map sensor. They are different than what was populated into those fields. I'll put the correct values in and see what happens. What showed up in the populated fields was Linear value of 200.00 and offset of 10.33. The supposed correct values that I found were 207.66 and 9.
    Last edited by David94TA; 03-31-2023 at 08:16 PM.
    94 TA 385ci T56 9.3cr 224/236 571/573 117lsa Procharger 9lbs boost at 6000 9 inch 3.21 gear