Optimizing WOT TQ w/ VCT in Forced Induction

[CCS86]

We have been kicking around this subject in another thread and decided it needed its own space.

According to some sources, VCT action, even in stock trim, is responsible for a lot of the output:
https://www.fordnxt.com/news/how-muc...-the-question/

With forced induction, and positive manifold pressure available to fill cylinders, and also a higher risk of loosing boost
from blow-through (during valve overlap), the optimum angles are most likely quite different. What range of values are
we talking about? Hopefully we can find out.

Obviously, strapping onto a dyno for a nice long session, with a solid plan to test all sorts of angle combinations, would
give you some nice data to pour over and determine optimums at each RPM. Not everyone has that option, and the fact
that we can't "live tune" the VCT settings definitely slows that process. I think we can come up with a protocol that allows
road based logging to give us direction on this.

Here is what I have rattling in my head:

• Pick a set of IVO/EVC angles with a LSA that has no positive overlap (ensuring that we have no blow through)
• Make the OP VCT tables equal to this angle set for all RPMs
• Log a WOT run that includes (at least) MAF rate, RPM and boost pressure (I have a mechanical gauge, so I gopro the
  boost gauge alongside my nGauge to get pairs of RPM vs boost)
• Now advance that angle pair to keep the same LSA and make another run
• Repeat this process for a number of different angle pairs advanced and retarded from the first pair

Looking at this data, we can plot boost pressure (or potentially MAF rate) against RPM. Minimal boost pressure should signify
best cylinder filling, which would correspond to highest MAF rate. Theoretically, the "best" angle pair would vary with RPM,
so you could pick the best angle pair vs RPM and composite them together to populate the OP VCT tables, maybe smoothing
somewhat if the transitions are big.

From there, we could move to optimizing the exhaust valve closing, by retarding it until the onset of blow-through. Similar to above:

• Make a baseline run with our new VCT angles
• Fix IVO angles and add a static +5* or +10* to all EVC angles, run again
• Repeat

At this point I think we need a measure of boost, because the MAF sensor can't differentiate between air combusted and air
blown through. It's possible that you would see STFTs increase, but I don't think that is precise enough. Basically, we would
now be looking at boost vs RPM and any reduction in boost, compared to our baseline, would be from blow-through and should
be avoided. You would pick the maximum EVC angle which did not reduce boost and store that in the table.

This would certainly be a more coarse approach compared to dyno runs, but I think it would net good data and get you much
closer than guessing or copying someone else. I'd love to hear any input on refining this method.



So for picking our baseline angles, we need to know where to start. Here is some info posted by others that should help get us
there. I'd love to hear the actual values listed confirmed, since I'm not an expert in Coyote cam specs:

With our camshafts at resting position.
Our IVO is 33.5 degrees AFTER TDC.
Our EVC is 17.5 degrees BEFORE TDC.
We are at negative over lap at IVO 0 EVC 0 and that is why we are retarded just the exhaust camshaft in fuel economy.

With our IVO at max advance which is 50 degrees, that makes our IVO 16.5 degrees BEFORE TDC.
With our EVC at max retard which is 50 degrees, our EVC IS 32.5 degrees AFTER TDC.

Correct me if I'm wrong..

It's not something I've done heavy research on, just google the cam specs.

From Mr. bbrooks98, an awesome excel worksheet. Validation of the calculations and values here would be nice as well:

This could be useful here. Something i've been tinkering with for a Gen 1 coyote. Let me know if anything looks off.

coyote_valve_event_graph.xlsx

[kris5597]

Let me start off with saying that VCT tuning in no way, shape, or form is quick and painless, it takes countless hours to do on each setup...

A dyno or some sort of horsepower program will be your best bet. VCT tuning is not as complicated as it may seem. The intake cam will follow the VE of the engine and the exhaust cam will aid in additional performance. Using a dyno program compared to a dyno will show positive results, even though in some cases you may have to test the same cam angle positions more than once to check consistency, it still works very good. Depending on your setup, n/a, supercharger, or turbo, VCT tuning is extremely critical, it is where I find power that others can't. Knowing how to do it properly is key. Locked exhaust cam VCT at 0, as you will come back to it later, and go through a fixed position with the intake cam locked at this position for an entire pull, go from max advance down to a logical cam position, or until you no longer positive changes to determining a peak rpm. Then you can overlay all of the intake pulls to determine the best intake cam position at each rpm of the engine to map out the intake cam to maintain the highest VE at each rpm breakpoint. Then you retard the exhaust in the same fashion, with the intake cam map already made. After this is complete, you can go back and make a pull with your "tuned" VCT and check your findings. Typically you will have to make minor changes on the intake side at peak power to adjust slightly, but this will insure that your VCT is right for the setup. A mistake most make, that the VCT for one setup is the same for another, even though it's still N/A or forced induction... wrong. Hope this helps.

[blackbolt22]

Anyone have optimized numbers for a completely stock car? I'm wondering what the optimized baseline is for NA compared to Ford's stock programming. I believe I read they left a lot on the table there but why? It's only for WOT , why not max it out?

EDIT: Speaking of the 11-14 Coyotes or even the S550s.

[kris5597]

Ford got it right with VCT on the vehicles as they come from the factory. I have seen no change in performance with VCT tuning on a stock car.

Kris

[bbrooks98]

Ford got it right with VCT on the vehicles as they come from the factory. I have seen no change in performance with VCT tuning on a stock car.

Kris

I'm interested in the why it does what it does mostly in the lower rpm range (2000-3800). Just from my dyno testing i've found gains with similar boss OP cam tables to be an improvement over stock. Granted my car has a cobra jet intake along with twin turbos. On paper they look pretty good too if you start plugging the values into the sheet. The tricky part with making dynamic compression changes is that you need to maximize ignition timing to make full use of the cam change. Like said, it could take countless hours of testing.
Boss cam timing vs stock GT.jpg
Where my understanding gets fuzzy is with the EVC. From a few sources i've read its says EVC should be between 5-15degrees ATDC. So combine that with low to no overlap it puts us in the -50 and about 3-11 degrees exhaust retard range for low rpm max torque. If we move the intake not as far advanced we have a larger window of less overlap, and better EVC angles but i'm convinced the IVC is worth more being set earlier down low.
Coyote 5L Dyn CR vs IVC.jpg

I did spend a day doing some dyno testing. What i mostly concluded was EVC seemed to work best with the exhaust commanded around 10 degrees retard with my combination but i never thought at the time to tested below 8 degrees retard at low rpm. I later went and did the sheet to try and understand what i was seeing, which opened up more questions.

Can you get away with overlap at low rpm? A few books i've read say that with low air velocity overlap should be avoided.
Narrow Lobe separation and early IVC improve low rpm torque. Does this stop increasing dynamic compression at some point or is your piston to valve clearance pretty much the limit?
Wide lobe separation benefits higher rpm. This I believe will vary depending on the power adder. With a turbo with moderate backpressure i tried to keep the overlap to a minimum while using the widest separation angle possible. WIth an NA car or blower car i'm sure you could probably get away with more exhaust retard and gain scavenging.

This was my results from tuning the VCT at wastegate pressure(6r80 locked up in 3rd for reference)

VCT tuning.jpg

[kris5597]

Yes, you can get away with some overlap at low rpm, however, as you mentioned, low air velocity in that area will not need much overlap. With a turbo, overlap and low spark advance will aid in decreasing spool time.

Were you asking another question?

Kris

[bbrooks98]

Yes, you can get away with some overlap at low rpm, however, as you mentioned, low air velocity in that area will not need much overlap. With a turbo, overlap and low spark advance will aid in decreasing spool time.

Were you asking another question?

Kris

That's what i plan to test next time i get back on the dyno. The first time was mostly spent moving the intake cam with the exhaust fixed to find what it liked. Do you have any results to show?

[kris5597]

No, unfortunately not. All of the dynos I kept pictures of were of the finished calibration.

Kris

[veeefour]

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.

[Thatwhite5.0]

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

[murfie]

http://citeseerx.ist.psu.edu/viewdoc...=rep1&type=pdf

Good read if you are interested in this topic of optimizing VCT. It discusses a real time approach, but compares a lot to the mapped points approach, which they find similar results. Basically proving the mapped point approach works, and you don't need a real time approach. Doing this you will need to use the mapped point approach to not only to make it easy on your self, but optimize the stock ECU.

[CCS86]

Murphie, thanks for that link! I'll dig in when I get a chance.

Let's drop the discussion about whether stock engines need VCT tuning or not. This thread is meant to be very specific to forced induction. Let's keep it clean and productive.

[kris5597]

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 am not sure what you mean by that? Changing modifications that affect the torque curve of an engine affects its VE, which most certainly requires VCT tuning.

Murphie, thanks for that link! I'll dig in when I get a chance.

Let's drop the discussion about whether stock engines need VCT tuning or not. This thread is meant to be very specific to forced induction. Let's keep it clean and productive.

VCT tuning is VCT tuning. It is required no matter how the air gets into the engine, it is required to maximize effciency on every setup. You'd be surprised how similar a VCT map looks on an N/A engine would compared to a properly designed turbo kit.

Kris

[veeefour]

I am not sure what you mean by that? Changing modifications that affect the torque curve of an engine affects its VE, which most certainly requires VCT tuning.



VCT tuning is VCT tuning. It is required no matter how the air gets into the engine, it is required to maximize effciency on every setup. You'd be surprised how similar a VCT map looks on an N/A engine would compared to a properly designed turbo kit.

Kris

I mean you can't gain any power by changing stock OP angles with stock cams - Ford already did the job. You can help yourself by changing EVC and IVO for better drive-ability and that's all.

[w00t692]

Ford did the work for OP with stock trim. If you think that there's nothing to gain by changing OP cam angling you are very mistaken. If we were to assume that we would have left upwards of 20 horsepower on the table on some of the setups we've tuned, and up to 100 whp on PD blower supercharged cars. I feel like what you're saying is not based in reality. The one part that changes the necessary cam timing the most is the intake manifold. Everything else is small potatoes.

[veeefour]

Let me guess? You got excited with 20 hp gain judging by your Virtual Dyno data logging or you overreacted reading +20 g/s from MAF?

Either way...I'll stick with my findings coming form countless hours spent on dyno and you can keep chasing ghosts.

[kris5597]

Real dyno, virtual dyno, MAF data... all relevant information when used properly. We use it all and find the same results. We are here discussing facts and actual findings. How exactly are you tuning VCT and not finding positive results. Every VCT engine we've tuned over the last 10 years required VCT tuning, no matter the setup, to maximize power.

[w00t692]

Dyno plus verified trap speed changes. Lemme guess, this isn't good enough... Probably means I broke it worse.

I'm trying not to be rude here but i cannot possibly see how you don't get positive results from properly dialing in cam timing. I see it all the time. ALL the time. Every setup that changes the intake manifold needs a very different curve than the OEM targets.

[bbrooks98]

This thread sounds more like a penis contest than something of useful information. Let's see some results/discuss theory. If something works or is better for your setup explain your findings preferably with data.

[w00t692]

Not really. Someone is saying not to even bother tuning VCT, meanwhile the OP of the thread has literally shown the power he has gained from changing it, and we are reiterating that yes, it is something that should be tuned.