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Thread: Stage 3 cam issue : torque dip between 3600-4400. TSP VVT3 and GPI stage 3 same issue

  1. #1

    Angry Stage 3 cam issue : torque dip between 3600-4400. TSP VVT3 and GPI stage 3 same issue

    Guys,

    Following this thread : https://forum.hptuners.com/showthrea...efore-4600-rpm

    I removed the TSP VVT3 Cam and installed a GPI Stage 3 cam and performance Morel 4708 Lifters ($750 the set !). I paired them with 7.750 comp cam pushrods, which was the correct lenght after using the comp cam push rod measuring tool (7.700 + 0.050 of preload). Also did a complete engine rebuild since the engine was out.

    This cam is a little less aggressive on the intake but more on the exhaust, with a 112LSA instead of 116LSA

    No matter what I have EXACTLY the same issue than with the TSP VVT3 with the GPI Stage 3 !!!

    Engine makes decent torque down low until 3500 rpm, then fall on its face for the next 1000rpm....Despite consistent timing, no torque management, no knock retard etc (exactly has the TSP). I tried again Ben Charles program or mine, same in both case. Airmass is falling or not climbing in this range. Keep in mind my 3000FT elevation

    On top of that the 112 LSA makes the idle a lot harder to stabilize, I'm struggling a lot of that. PCM keeps giving me P300 Random misfire, even at 1000 rpm idle I get like 10-15 misfires per cylinder. I'm really bummed... I managed to get it better in very low load transition by decreasing the external load torque value, but now my idle surges...Also since the idle is shitty the MAF calibration in this area is difficult to obtain in those low frequencies (2400-2700 and 2800hz)...

    I precise right now I'm on MAF only, I had a comment from Hassan that it was the transition from Dynamic to MAF, nope, not that Dynamic is disabled...

    I precise stock cam was dot to dot on cam timing, Did the same for the TSP and the GPI. Jumping 1 tooth would be 8 degree, I can't see how it could be possible both the TSP and the GPI have exactly the same behavior if it was a timing issue. If stock cam was dot to dot, if only the TSP was having the issue it could have been a ground issue. On 2 different cam I don't see that possible.

    I ordered a stock ported IM to see if the issue could come from my used MSD IM (bought it used). With the TSP I put a 100% stock IM from my Camaro and it reduced the issue, without making it disapear though.

    See some logs

    Prog Alex 062020.hptAlex 062020.hplpull2 14062020.hpl

    I'm lost and pissed...

    Thanks

  2. #2
    Advanced Tuner lt1z350's Avatar
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    What I have found is virtual troque is causing the idle issues. I talk about it alot in the thread I have last posted on. The corelation on the airmass to map virtual torque tables is now way off. look at any lof your old stock logs maybe when you had bolt ons only and look to see what airmass and kpa its idleing at. Then go to the new current one and compare it then go back to your current tune and line the virtual torque up again. its going to take a few adjustments as it gets better it will make more timing idle will most likely be able to come down some and the amount of commanded torque is going to need adjsutment. I have a decent size cam idleing at 650 and its happy. It could even go 600 and be ok as I tested it but I like the throttle better the feel if not so low. Many raise the idle up a lot to compensate it seems where if you get these vt maps back to being correct it will fix a lot of these issues I am finding. Its hard to transfer between these huge swings in values Im guessing. Like if it idles at .15 cyl and 50 kpa and now its .40 and 80 kpa its going to have to transfer between huge torque swings as the stock tune if you look at the .15 50 kpa on the stock tune I bet those values are with in 10 lbs of torque. Any devance from this is making it command wrong torque close or open throttle or more so take or add timing making it impossible to work correctly. I found this was even more important then the correct model on the vve. While many values in the stock tune make no sense to how the stock power ratings might be thats what the factoy set to make it work so trying to follow along those same lines seems to be working for me when comes to making this torque based tune stuff work much better. I went from issues much like you to feeling like I really have a handle on how to fix issues I come across it just takes time logging and keep adjusting so that it then runs well enough to really nail down what the combo wants.
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  3. #3
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    You usually have to disable P300 code with a lower LSA cam. They aren't really misfires, its just the sensor picking up the lope as misfires. It is safe and normal to turn off P0300.
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  4. #4
    I was able to improve a lot my idle by multiplying my Idle external load by 0.8... Still not perfect though. I disabled the P300 code yes after some reading...

    I contacted GPI for my torque issue. They started to look but they think it could be linked to my MSD...Still find that weird because a ton of people have an MSD with a stage 3 cam...

  5. #5
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    If I were betting, I'd say the injection scheduling dependency on that messed up IVT model is the cause...

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    Quote Originally Posted by Sachs View Post
    I was able to improve a lot my idle by multiplying my Idle external load by 0.8... Still not perfect though. I disabled the P300 code yes after some reading...

    I contacted GPI for my torque issue. They started to look but they think it could be linked to my MSD...Still find that weird because a ton of people have an MSD with a stage 3 cam...
    I thought you put a stock ported IM back on and the results was the same?

    I took the entire 90 degree oil temperature column in my idle external load table and pasted it to both 131 and 194 degree columns. This effectively raised the idle external load value (not sure what the number is if its a torque value or what?). I also had to do what the others are talking about and lowered virtual torque in the idle airflow and airmass regions and rpms. I only lowered it at the negative and low spark tables and progressively lowered it less as I got to the 30 and 40 degree spark tables and left those the same.

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    Quote Originally Posted by TriPinTaZ View Post
    You usually have to disable P300 code with a lower LSA cam. They aren't really misfires, its just the sensor picking up the lope as misfires. It is safe and normal to turn off P0300.
    Do we know 100% for sure its not misfiring with cams? My theory is that since if you lock the TC and put it into high gear and lug the engine down to the idle rpm range it will still operate smoothly. I think this is just because the car is moving with the drivetrain locked together so the cars weight is acting like a giant flywheel and causing a relatively smooth torque delivery. However, if you stop the car and let it idle, the only inertia you have then is just the rotating mass of the engine and accessories and flywheel, you then can feel the lope, surge, and vibrations. So is it possible to have not a full misfire but more of a slight misfire or abnormal combustion that would decrease torque delivery? Or is combustion always stable enough to where it either misfires or it doesn't? I just don't understand how it could only partially misfire, I wish we could take over timing control, I would like to see if very high advance 40-50 degrees would smooth out the idle with a cam? I guess there's really no way to distinguish abnormal combustion from an actual misfire.

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    Quote Originally Posted by smokeshow View Post
    If I were betting, I'd say the injection scheduling dependency on that messed up IVT model is the cause...
    Can you elaborate some more? By IVT do you mean intake valve temperature? I though IVT was only used for like one table, unless its used in the background other places?

  9. #9
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    Quote Originally Posted by cmitchell17 View Post
    Do we know 100% for sure its not misfiring with cams? My theory is that since if you lock the TC and put it into high gear and lug the engine down to the idle rpm range it will still operate smoothly. I think this is just because the car is moving with the drivetrain locked together so the cars weight is acting like a giant flywheel and causing a relatively smooth torque delivery. However, if you stop the car and let it idle, the only inertia you have then is just the rotating mass of the engine and accessories and flywheel, you then can feel the lope, surge, and vibrations. So is it possible to have not a full misfire but more of a slight misfire or abnormal combustion that would decrease torque delivery? Or is combustion always stable enough to where it either misfires or it doesn't? I just don't understand how it could only partially misfire, I wish we could take over timing control, I would like to see if very high advance 40-50 degrees would smooth out the idle with a cam? I guess there's really no way to distinguish abnormal combustion from an actual misfire.

    I can't tell from here if it is or is not misfiring. But I can tell you that a majority of cammed cars need to disable P300.

    Also I think Smokeshow was implying SOI and EOI in the torque dip area. Have you tried making changes to the Injector Timing in that area? The Wideband could read fueling is fine even if injection timing isn't optimal.
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    Quote Originally Posted by TriPinTaZ View Post
    I can't tell from here if it is or is not misfiring. But I can tell you that a majority of cammed cars need to disable P300.

    Also I think Smokeshow was implying SOI and EOI in the torque dip area. Have you tried making changes to the Injector Timing in that area? The Wideband could read fueling is fine even if injection timing isn't optimal.
    I forgot how much room I calculated with my cam and overlap but I think I still had plenty 20-30+ degrees from the stock SOI, so I increased it by about 10-20 degrees from stock in the idle regions. I think I went almost to about 360 degrees before I stopped, I saw zero effects changing it any, but I have no reliable indicators on if its running better (gas analyzer etc.) but looking at idle timing, throttle position, and airmass as a indicator of better efficiency, I didn't see any changes either. I was expecting the engine to run significantly different changing injection timing, I thought it was going to really help out combustion given that it would it extra time for the charge to mix and burn faster.

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    Quote Originally Posted by cmitchell17 View Post
    I forgot how much room I calculated with my cam and overlap but I think I still had plenty 20-30+ degrees from the stock SOI, so I increased it by about 10-20 degrees from stock in the idle regions. I think I went almost to about 360 degrees before I stopped, I saw zero effects changing it any, but I have no reliable indicators on if its running better (gas analyzer etc.) but looking at idle timing, throttle position, and airmass as a indicator of better efficiency, I didn't see any changes either. I was expecting the engine to run significantly different changing injection timing, I thought it was going to really help out combustion given that it would it extra time for the charge to mix and burn faster.
    Could it be a trans issue?
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    Quote Originally Posted by TriPinTaZ View Post
    Could it be a trans issue?
    I do have the TC slipping problem. I had the "triple flush" done when it was under warranty but now I've got almost 90k and need to get the updated flush done with the machine and the new mobil 1 fluid but I don't want to pay for it.

    However, I think its just due to the nature of having a high duration/high overlap cam. My guess is the main issue that makes big cams run the way they do is just from the high exhaust revision that impedes combustion. There's no published data about combustion with big cams since OEMs don't use them.

  13. #13
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    Looking at this again, it does look like an exhaust or intake tuning issue. And it is interesting that the stock calibration ramps the cam forward right where you're seeing your torque dip...may be partially due to the exhaust ports themselves. But that IVT needs addressing for sure.

  14. #14
    Quote Originally Posted by smokeshow View Post
    Looking at this again, it does look like an exhaust or intake tuning issue. And it is interesting that the stock calibration ramps the cam forward right where you're seeing your torque dip...may be partially due to the exhaust ports themselves. But that IVT needs addressing for sure.
    What do you mean intake or exhaust tuning issue ?

    Just FYI I tried a stock ported IM : no changes except perhaps better torque from 2500-3000 rpm but still the same dip in airflow. Today I ran E85 for the first time : same, was pretty sure it could not change anything.

    I tried to play with SOI in the past with no effect... this was without the ported heads. Could SOI/EOI affect the airflow of the engine ? What I really find weird is that an engine is a positive pump : airflow should be proportional to its speed. More revolutions = more airflow in an almost linear fashion (more pressure drop in intake and IM at higher flows yes). What could impact my airflow in those ranges ?

    Look at one of my first E85 runs today (not optimized by far) : I have 2 dips in fact

    Sans titre (1).jpg


    My question is : would cam timing create such an issue ? I would assume a cam retarted a lot would mean the engine would be a dog below 3000 rpm...Which is not the case...

    Also, yes it did not degree the cam, but even if did and found it off by 4deg : 1- Jumping a teeth is 8deg 2- 4deg of retard would not create a dip from 3500-4500 right ? It would be all accross the range...

    Seriously this is getting old...
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    Last edited by Sachs; 07-19-2020 at 09:57 PM.

  15. #15
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    Cam timing could cause a dip in power. Are you 100% sure the cam isn't moving at all?
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  16. #16
    Yep looking at my pull : desired angle 0 actual angle is 0 to 0.4 deg measured by the VVT system. Since the cam phaser is locked this one can't move. And I have a C5R katech timing chain.

    When I was talking about cam timimg I was talking about physical cam timing not the VVT doing something weird since it is disabled... My physical cam timing is dot to dot
    Last edited by Sachs; 07-20-2020 at 08:46 AM.

  17. #17
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    Quote Originally Posted by Sachs View Post
    Yep looking at my pull : desired angle 0 actual angle is 0 to 0.4 deg measured by the VVT system. Since the cam phaser is locked this one can't move. And I have a C5R katech timing chain.

    When I was talking about cam timimg I was talking about physical cam timing not the VVT doing something weird since it is disabled... My physical cam timing is dot to dot

    I figured. Physical cam timing can move the power band up and down, but it shouldn't cause a dip like that. Some other possibles are tire slip on dyno, clutch slip(but you're auto) and maybe dyno error but I thought you said in another thread that you went to two different dynos.
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  18. #18
    Quote Originally Posted by TriPinTaZ View Post
    I figured. Physical cam timing can move the power band up and down, but it shouldn't cause a dip like that. Some other possibles are tire slip on dyno, clutch slip(but you're auto) and maybe dyno error but I thought you said in another thread that you went to two different dynos.
    My C7 is a M7 not an Auto. But no clutch slip nope...I went to only one dyno so far... I feel the dip in the pant and the airflow shows it as well, as less airflow = less power...

  19. #19
    This whole stuff is a nightmare...

    Pissed about all this stuff I bought a Katech Stage 2 complete engine. I have the same issue with it, and I know the engine has no issues since Katech dynoed it before shipping. The difference is this time I got VVT, so I'm gonna play with it. For now I used the stock VVT table (minus I reduced the VVT to 11 deg max for in the low loads). The issue I am fighting since the beginning is related to my car / ecu... Where, I can't tell... At least I know I can sell my old engine without issues ...

  20. #20
    What is the exhaust setup on the car?