VTT adjustment after going FI - need help

[Roland_Price]

Hi, everyone

I've installed a PD blower on my 2016 Camaro, dialed in MAF and VE, but since I still have the stock VT tables the car drives like crap - hard shifts, hesitation upon downshifting and revving back and forth when trying to downshift, etc.

I have found some suitable info on VTT tuning procedure only in this thread's post along with a procedure https://forum.hptuners.com/showthrea...l=1#post714970 , but it's for the Gen4 so I don't know if it's applicable. The other stuff that I looked into is either questionable methods on YT or stuff from the NA builds.

Can anyone please weigh in on the process of tuning VTT without the dyno? I need to get it at least in the ballpark of 10-15% or so, right now Delivered Engine Tq can be up to 30-35% higher than Predicted or Commanded Tq

[GHuggins]

Post your current and stock tune files.

[Roland_Price]

Post your current and stock tune files.

Here they are. Don't judge me in case you find something criminal in these, that's my first self tuned car

Camaro_Stock0.hpt
Camaro_v44_VT_1.hpt

[GHuggins]

Didn't know it was a V6 This is gonna take a while. What's your barometric pressure where you live or where this was dialed in kpa wise?

[Roland_Price]

Didn't know it was a V6 This is gonna take a while. What's your barometric pressure where you live or where this was dialed in kpa wise?

It's 105 kPa here. I found the HPT and dyno logs from May 2024, it was prior to retuning and setting a proper knock sensors level, but still gives a bit of perspective

CamaroV6_v24_run1.hpl
i5313oia.pdf

[GHuggins]

See if this makes any difference. I did not do them all. In fact I only got most of the intake positions done over the last 2 hrs, but see if it makes any difference at all. I would recommend maybe changing your cam positions so you aren't using so many too then if this makes a difference shoot me an email... It also looks like the cams weren't locked in at their specific positions to dial the VE in, so this may be a wasted effort. Try it and see. There are 20 different positions and why I don't like V6's

[Roland_Price]

See if this makes any difference. I did not do them all. In fact I only got most of the intake positions done over the last 2 hrs, but see if it makes any difference at all. I would recommend maybe changing your cam positions so you aren't using so many too then if this makes a difference shoot me an email... It also looks like the cams weren't locked in at their specific positions to dial the VE in, so this may be a wasted effort. Try it and see. There are 20 different positions and why I don't like V6's

Thanks a lot! IT's 11 PM here, I will try it tomorrow and report results. I'm thinking of locking cams to zero in all scenarios, but I don't know what amount of torque and HP I will be losing. In case it's negligible I will certainly do it for the ease of tuning

[GHuggins]

Going by the factory VE, you're probably going to want the intake around 10 and the exhaust around 20 for wot. Going by (your) VE, if it's right, you're going to want the intake and exhaust both set to 10 for wot. You can work it from there going off of that and what feels the best to you as it should be noticeable one way or the other.

Regular driving depends on how much economy and bottom end torque you want. Looks like more positive intake burns more, but makes more torque...

I'm not sure if what I did will be noticed after looking at the tables. It would with the exhaust at 0, but I didn't get to many more of the exhaust settings.

[Roland_Price]

Going by the factory VE, you're probably going to want the intake around 10 and the exhaust around 20 for wot. Going by (your) VE, if it's right, you're going to want the intake and exhaust both set to 10 for wot. You can work it from there going off of that and what feels the best to you as it should be noticeable one way or the other.

Regular driving depends on how much economy and bottom end torque you want. Looks like more positive intake burns more, but makes more torque...

I'm not sure if what I did will be noticed after looking at the tables. It would with the exhaust at 0, but I didn't get to many more of the exhaust settings.

I will lock both at zero and do a couple of runs to confirm my base VE table is valid, flash your changes and drop you an email if you don?t mind)

Just to doublecheck - when you say 10 you mean advance the cam 10 degrees or retard it? I always thought that I need to advance the intake in the lows to get more torque and retard in the highs to get beter scavenging

[GHuggins]

In this case it should be retarded for both or "positive" values. I'm just using the VVE editor to see how it's changing the airflow moving the cams around. Not 100% accurate I know, but I've found it to be in the 90some % accuracy more times than not. This is granted your VE coefficients are dialed in correctly including for cam movement. You can also use the torque models "factory ones" for the same thing to get the cams roughly close to optimal without using a dyno.

[Roland_Price]

In this case it should be retarded for both or "positive" values. I'm just using the VVE editor to see how it's changing the airflow moving the cams around. Not 100% accurate I know, but I've found it to be in the 90some % accuracy more times than not. This is granted your VE coefficients are dialed in correctly including for cam movement. You can also use the torque models "factory ones" for the same thing to get the cams roughly close to optimal without using a dyno.

Thanks, I'll see into it once I get to VVT tuning. Meanwhile... your tune definitely changed things for the better, at least the torque is pretty much spot on in the logs, so thanks a lot for that. But as I locked both cams to zero and checked the VVE is turned out it was waaay off. So I will get it in proper shape and post an update tomorrow if you don't mind. Will you be able to do your VTT magic again?

[KillboyPowerhead]

Curious if you replaced the high pressure fuel pump. I'm tuning an LFX with Mace cams and found that at ~7200 RPM I can't have any extra exhaust retard or else EOI will be after 180 BTDC which is when you want injection to finish, or so I've read/been told. The Mace cams have a longer duration than stock but I'm also NA; seeing IPW of ~3.6 ms at 7200. Just something to consider when playing with the cams at higher RPMs.

[GHuggins]

Curious if you replaced the high pressure fuel pump. I'm tuning an LFX with Mace cams and found that at ~7200 RPM I can't have any extra exhaust retard or else EOI will be after 180 BTDC which is when you want injection to finish, or so I've read/been told. The Mace cams have a longer duration than stock but I'm also NA; seeing IPW of ~3.6 ms at 7200. Just something to consider when playing with the cams at higher RPMs.

Hmmm. I haven't messed with many V6's. I try to avoid them like the plague just for the simple reason of taking FOREVER to do the air and torque models Sooo, I know they should be adjusting the injection for the intake cam, so I guess it's tied to the intake only and not at all to the exhaust in this case or in any GM for what you're saying? Good to know. Could you not at that point shift them both slightly opposite of one another to gain a little more headroom without losing too much in power?

[GHuggins]

Thanks, I'll see into it once I get to VVT tuning. Meanwhile... your tune definitely changed things for the better, at least the torque is pretty much spot on in the logs, so thanks a lot for that. But as I locked both cams to zero and checked the VVE is turned out it was waaay off. So I will get it in proper shape and post an update tomorrow if you don't mind. Will you be able to do your VTT magic again?

Yes, just make sure the VE is as close as you can correctly get it.

[KillboyPowerhead]

Hmmm. I haven't messed with many V6's. I try to avoid them like the plague just for the simple reason of taking FOREVER to do the air and torque models Sooo, I know they should be adjusting the injection for the intake cam, so I guess it's tied to the intake only and not at all to the exhaust in this case or in any GM for what you're saying? Good to know. Could you not at that point shift them both slightly opposite of one another to gain a little more headroom without losing too much in power?

Hmm not sure what you mean by adjusting injection for the intake cam. At the higher RPMs I'm starting injection at EVC + injector dwell time (which I believe is 0.3 ms for the LFX). In my case (Mace cams) EVC is about 334 BTDC, so with an IPW of ~3.6 ms that actually puts EOI slightly past 180 BTDC.

Not sure how different the LGX is but I'm guessing the cams are similar to the LFX/LLT/LY7 where EVC is around 351 BTDC I believe, so with an IPW of 3.6 ms you could have ~8 degrees (cam degrees) of exhaust retard to have EOI around 180 BTDC, but supercharged I'm guessing the IPW is a fair bit higher, and to have EOI by 180 BTDC at 7200 with EVC at 351 BTDC you're maxed out at ~4 ms IPW (guess this is also assuming the LFX and LGX have the same fuel pressure, which for me is upwards of 16 MPa/2320 PSI).

[GHuggins]

Hmm not sure what you mean by adjusting injection for the intake cam. At the higher RPMs I'm starting injection at EVC + injector dwell time (which I believe is 0.3 ms for the LFX). In my case (Mace cams) EVC is about 334 BTDC, so with an IPW of ~3.6 ms that actually puts EOI slightly past 180 BTDC.

Not sure how different the LGX is but I'm guessing the cams are similar to the LFX/LLT/LY7 where EVC is around 351 BTDC I believe, so with an IPW of 3.6 ms you could have ~8 degrees (cam degrees) of exhaust retard to have EOI around 180 BTDC, but supercharged I'm guessing the IPW is a fair bit higher, and to have EOI by 180 BTDC at 7200 with EVC at 351 BTDC you're maxed out at ~4 ms IPW (guess this is also assuming the LFX and LGX have the same fuel pressure, which for me is upwards of 16 MPa/2320 PSI).

Yeah, I guess gen V's don't adjust the eoi for cam movement as they have a completely different programmable soi table that should already have that incorporated into it. I was thinking of the gen 4's for some reason where they change eoi for the moving cam. Of course its also been stated that the 180 isn't necessarily a set in stone value for the injection window which is why I guess you see some doing fine past that whereas most don't like going past that. Guess you would need a dyno for sure in this case.

[KillboyPowerhead]

Indeed, would ultimately need a dyno to know for sure, but most of what I could find regarding injection timing suggested that EOI much past 180 BTDC starts to hurt torque, although I guess every engine is different. One could also raise the HPFP pressure slightly if EOI is going slightly past 180; the LFX has a max setting of 15 MPa and I regularly see it hit ~16 MPa; the factory pump has a pressure relief at ~17.5 MPa so I imagine you could safely bump up the pressure to 15.5 MPa if needed.

If you needed more pressure/flow, do you know if simply replacing the HPFP would be adequate (assuming the injectors are still big enough), or would you need a bigger fuel lobe on the cam to run it too?

[GHuggins]

You can go up to a bigger bore hpfp as long as it's able to control the idle pressure ok. Seen that to be an issue on the smaller 4 bangers where they would make so much pressure at idle that it would actually cause the main fuel line to leak... I've even had some guys just going up on injectors for example the l83 guys using lt4 injectors with the stock smaller l83 hpfp and be ok although I recommend keeping a hpfp that's capable of flowing what the injectors will. I've actually got a few guys running boost on l83's with the lt4 injectors and l83 hpfp still on them. I honestly have no idea on the V6ers with what you can or can't do...

[KillboyPowerhead]

Forgot about this: http://www.getoverkilled.ca/camaro5supercharger.html. Looks like these V6's can handle 8 lbs. of boost before needing any fuel system upgrades, and the LGX can apparently handle +12 lbs. with just bigger injectors and a LPFP upgrade. http://www.getoverkilled.ca/camaro6supercharger.html

[Roland_Price]

Forgot about this: http://www.getoverkilled.ca/camaro5supercharger.html. Looks like these V6's can handle 8 lbs. of boost before needing any fuel system upgrades, and the LGX can apparently handle +12 lbs. with just bigger injectors and a LPFP upgrade. http://www.getoverkilled.ca/camaro6supercharger.html

I am yet to confirm this point - after proper VE tuning I'm going 3.00" pulley on my Edelbrock. I'm running stock injectors and ZL1 LPFP with 11.5 PSI of boost top, and I'm currently on 3.25"