Optimizing WOT TQ w/ VCT in Forced Induction

[CCS86]

I would leave the OP tables stock in a stock car, also would leave it stock for stock cams no matter the intake manifold/tb/cai combo. There's nothing to be gained.

IVO/EVC tables are a different story.

I also don't know what you are trying to say here. There are "OP tables" for a number of different aspects of the tune. We are talking about OP VCT tuning. The OP VCT tables define IVO and EVC angles, so you are contradicting yourself.

This thread was started specifically for the purpose of tuning VCT for forced induction. I really don't care whether you or anyone else thinks stock angles on a stock car are ideal. Start a thread about that if you have an axe to grind.

[CCS86]

It may be beneficial to let some of the hot gasses escape. Restrictions in your exhaust, mufflers, catalyctic converters, exhaust manifolds will have a different effect from car to car. This is still good data to collect. I've done the same to my 2012.

These are the cam specs for first gen Mustang GTs.

Intake Cam:
Advertised: 263
.050": 211
Lobe Lift: .235"
Centerline (Park / Max): 139 / 89

Exhaust Cam:
Advertised: 263
.050": 211
Lobe lift: .216
Centerline (Park / Max): 123 / 73

Valve events @ Park (no adv/ret) @.050":
IVO: 33.5 ATDC
IVC: 64.5 ABDC
EVO: 48.5 BBDC
EVC: 17.5 BTDC

Total overlap (Park) @.050: -51

Valve events @ Max @.050:
IVO: 16.5 BTDC
IVC: 14.5 ABDC
EVO: 1.5 ABDC
EVC: 32.5 ATDC

Total overlap (Max) @.050: 49

Good info, thanks!

So is it generally accepted that overlap occuring at less than 0.050" of lift, is of no concern? Or could that still allow some blow-through under boost?

Do we know what the parked overlap is at 0" lift?

[superman07]

Curious to see what data if any people may have on the voodoo with Whipple and the 132 TB and long tubes. Where can I dig up the cam info to create a event map?

higher intake pressure - more Intake retard - but with the high compression it might need spark retard or better fuel?

retard Exhuast cam to reduce / eliminate overlap - Maybe a bit more than normal with long tubes? Is overlap always bad with boost? With a PD blower would you ever want overlap? Nothing to spool.

[txtailtorcher]

I have not had time to test however, basic knowledge would suggest that in turbo applications that had a larger turbine that has trouble spooling you would want no overlap at idle. Approaching the powerband you would increase overlap to achieve target boost pressure quickly and then taper off to hold that pressure and maximize cylinder pressure until the end of the RPM range. Obviously, you would need to take into account that you will have less time to get the same amount of air in the cylinder as RPMs increase so increasing IVO, enabling blow through logic in SD and minimizing the amount of actual blow through by modulating EVC would be best. We have one car at the shop that is in the middle of getting a new engine and centri so I should be able to give some logs and info soon after that one is done and on the dyno.

[Plimmer]

I’ll add my 2c here based on about 18 dyno pulls and about 6 hours at the dyno. I was NA at the time:
1. Have all your test positions pre tuned so you can flash them and go, name them so you can tell where you are. 3 hours into tooning and its easy to loose your way and forget where you are.
2. Log every pull and name the logs the same name as the dyno pulls. Do 2 pulls on the same toon if something is not right. Usually timing on the coyote is not identical one pull to the next.
3. Log a lot of parameters because wheel horse power is not conclusive enough. Because timing and IAT can make comparing pulls difficult, you also need to compare MAF flow to try decide if one toon is better than another.
4. Intake timing seems to make more difference, moving the exhaust didn’t seem to change anything for whp or MAF airflow.

Then I went turbo and I haven’t retested cam timing, but seat of pants I can feel more torque from reducing overlap as rpm increases. But again, it’s hard to compare since the coyote will run with timing a couple degrees different each test.

[kris5597]

Curious to see what data if any people may have on the voodoo with Whipple and the 132 TB and long tubes. Where can I dig up the cam info to create a event map?

higher intake pressure - more Intake retard - but with the high compression it might need spark retard or better fuel?

retard Exhuast cam to reduce / eliminate overlap - Maybe a bit more than normal with long tubes? Is overlap always bad with boost? With a PD blower would you ever want overlap? Nothing to spool.

Yes, absolutely. A lot more than you would think.

I’ll add my 2c here based on about 18 dyno pulls and about 6 hours at the dyno. I was NA at the time:
1. Have all your test positions pre tuned so you can flash them and go, name them so you can tell where you are. 3 hours into tooning and its easy to loose your way and forget where you are.
2. Log every pull and name the logs the same name as the dyno pulls. Do 2 pulls on the same toon if something is not right. Usually timing on the coyote is not identical one pull to the next.
3. Log a lot of parameters because wheel horse power is not conclusive enough. Because timing and IAT can make comparing pulls difficult, you also need to compare MAF flow to try decide if one toon is better than another.
4. Intake timing seems to make more difference, moving the exhaust didn’t seem to change anything for whp or MAF airflow.

Then I went turbo and I haven’t retested cam timing, but seat of pants I can feel more torque from reducing overlap as rpm increases. But again, it’s hard to compare since the coyote will run with timing a couple degrees different each test.

I'd recommend targeting a spark lead that will remain consistent, it's what I do. We know where MBT is at on the coyote, and instead of having the knock sensor interfere and alter the timing curve, target a slightly lower spark lead, one you know will not skew the results. Once you narrowed down your intake VCT that will follow VE, retard the exhaust as you stated. Add the timing back in, make small adjustments to the intake cam to confirm findings with added spark lead.

Kris

[CCS86]

With a PD blower would you ever want overlap?

Yes, absolutely. A lot more than you would think.
Kris

Can you explain your reasoning here?

[superman07]

Curious if overlap would require enabling the blow through logic. It is currently disabled on the whipple cal.

[kris5597]

To not make it over complicated, after dyno testing and tuning, VCT results pointed to the PD loving overlap, more than a naturally aspirated setup, for comparison.

[CCS86]

To not make it over complicated, after dyno testing and tuning, VCT results pointed to the PD loving overlap, more than a naturally aspirated setup, for comparison.

It just doesn't make conceptual sense to me. I have no dyno testing to backup my intuition.

To my knowledge, overlap helps in both getting out the last bits of combusted charge (better scavenging), and helping to initiate cylinder filling for the next event, using inertia from the exhaust flow.

Better scavenging should improve power in any application, so I could see a small amount of overlap being helpful. But with positive MAP ready to fill the cylinders, even when cylinder pressure isn't very low, it's hard to picture overlap being much help there.

[bbrooks98]

It just doesn't make conceptual sense to me. I have no dyno testing to backup my intuition.

To my knowledge, overlap helps in both getting out the last bits of combusted charge (better scavenging), and helping to initiate cylinder filling for the next event, using inertia from the exhaust flow.

Better scavenging should improve power in any application, so I could see a small amount of overlap being helpful. But with positive MAP ready to fill the cylinders, even when cylinder pressure isn't very low, it's hard to picture overlap being much help there.

That was my understanding as well. I was always under the impression that too much overlap on a PD blower you'd actually lose boost.


Once of the things I've been meaning to setup since I'm turbo is getting some back pressure data and seeing how different amounts of overlap effect back pressure and if there is a power vs back pressure correlation throughout different engine speeds. I'm curious if that can be an effective vct tuning tool working with a smaller sized turbocharger.

[CCS86]

That was my understanding as well. I was always under the impression that too much overlap on a PD blower you'd actually lose boost.


Once of the things I've been meaning to setup since I'm turbo is getting some back pressure data and seeing how different amounts of overlap effect back pressure and if there is a power vs back pressure correlation throughout different engine speeds. I'm curious if that can be an effective vct tuning tool working with a smaller sized turbocharger.

Yeah, the turbo complicates the equation for sure! The method I laid out uses boost to infer the dynamics of the system. But, when exhaust flow is actually developing your boost, the logic breaks down.

[kris5597]

Like I said, don't overthink or complicate it. Just test it for yourself and see what you find.

Kris

[curt@injected]

I prefer to sweep them on the dyno and then overlap the graphs to find the ideal angles. Some set ups can take 40 pulls or more. I usually shut off all knock retard and advance and start with a safe spark number so that it doesn't influence my results.

There are some huge gains to be had if you have the patience to do it.

[blackbolt22]

Are we sure there is nothing to be gained on a stock engine with these OP Angles? -40 Intake from 1750 to 4000, and 15 exhaust from 3k+ .. Surely these blanket angles can be optimized but how much is it worth? Sorry for bringing up N/A in your thread OP but it was discussed here and I love to theorize

Prior to me buying HPT I spoke to VMP and they told me there were significant untapped gains to be had in the lower RPMs (not so much at peak) @ WOT on a bone stock coyote..... Any truth to this?

11-14StockOpAngles.PNG

[curt@injected]

There are gains to be had stock on some of the 11-14 cals, but not on anything 15 and newer. At least not much

Quite a few of the 11-14 cals have some low rpm torque that can be had with vcm tuning.

[CCS86]

Do we know what the parked overlap is at 0" lift?

Anyone know this?

ThatWhite5.0 shows it at -51* overlap, parked, @ 0.050" lift

[blackbolt22]

Anyone know this?

ThatWhite5.0 shows it at -51* overlap, parked, @ 0.050" lift

The way I had figured it out @ 0" lift was -0.5 true overlap @ Park if the specs I saw were accurate on the stock cams (11-14).

-51 overlap is correct @ .050"

[CCS86]

The way I had figured it out @ 0" lift was -0.5 true overlap @ Park if the specs I saw were accurate on the stock cams (11-14).

-51 overlap is correct @ .050"

Interesting. So, it takes essentially 50* of crank rotation to move from exhaust valve at 0.050" lift to intake valve 0.050"?


I was searching around for a good valve even calculator. This one seems pretty good, but I can get the settings to match the posted specs. It seems like the "advance" field needs a negative value to to allow an intake centerline value higher than the exhaust (but it won't allow it):

https://mgispeedware.com/camshaft-calculator/

[CCS86]

According to this simpler calculator, we are just barely into positive overlap, while parked, at zero lift:


Fifty-thou-lift.jpg


Zero-lift.jpg