2015 GT Valve Overlap Tuning

[kris5597]

Well, the negative overlap is relative to what really makes power on the setup at hand. I feel its several components paired together resulting in that being the optimal tune for that setup. At first I thought it was the IMRCs, however, once they open at WOT, they are of no restriction. I honestly think its the long tube runner and plenum volume of the stock intake manifold paired with the short tube odd pairing of the stock exhaust manifolds attached to large catalytic converters. All of these components paired with larger valves, cams, and better flowing heads, requires a abnormal tuning of the VCT for the car to function efficiently. Imagine having a race engine and them slapping a cork in the intake and exhaust, VE is going to take a massive dive and to get the car to operate, massive tuning changes will have to be made for the decrease in airflow. That would be my guess. However, no one has proved this yet. And tuners that have tested this argue that it isn't the case, however, they have NOT tuned VCT correctly, which leaves me to believe the potential is still there. I learned to tune on VCT vehicles, so I know how well it can be adjusted to increase VE. Most Mustang tuners I feel come from single cam non VCT engines, so it's all new technology and tuning to them.

[02GTP]

I think you are over thinking this. Not surprised with no real mods there was 0 gain, because Ford did all the testing for you to get it perfect the way it is. Now with long tubes that can change things a little but I don't think there is much to be had. Maybe with a different intake mani and cams it will have to be significantly altered but there just isn't much to be had with bolt ons.

[kris5597]

Well, I am speaking off of experience. The vehicle dialed in from the factory with best optimization on the tune how the car sits, I agree. I have never really found significant gains on any engine I have tuned with VCT when they are stock. However, when modified with bolt ons, absolutely. Extreme changes in VCT compared to stock mapping. Swapping camshafts will change VCT because they are designed to focus VE at different rpms from stock, so that's a no brainer. However, whenever you install bolt ons, that also alters VE. There is power to be made for sure. Think of it this way. The coyote, road runner, and CJ engine are all the same engine. There are a few components that set them apart. The 2015 engine shares a lot of components to the road runner and CJ engine, a lot more than the 11-14 GT. Why wouldn't the same engine share similar VCT tables because it comes in a different chassis?

What separates the 2015 GT engine from the Boss and CJ engine?

[kris5597]

Check out these VCT tables from a different engine I have tuned. I have explanations for each below.

This is stock VCT on a stock engine on this vehicle.
Screen Shot 09-22-15 at 12.45 PM 001.PNG

This is the same engine, everything else stock, except going from a long runner intake manifold to a short runner intake manifold with a larger plenum. Look how much VCT needed to change to compensate for the new intake manifold. On this particular engine, a little torque was lost down low, however, the car carries hp over 1000 rpm higher.
Screen Shot 09-22-15 at 12.44 PM.PNG

This is a slightly different engine that has stock VCT but came from the factory with the manifold previously discussed that was swap on the previous engine. Look how similar VCT is between this engine and the previous with the same intake manifold.
Screen Shot 09-22-15 at 01.02 PM.PNG

This is the same engine with intake, header, and exhaust tuned.
Screen Shot 09-22-15 at 12.45 PM.PNG

[kris5597]

This is Stock 2015 GT Intake and Exhaust VCT.
Screen Shot 09-22-15 at 01.42 PM.PNG

This is 11-14 modified VCT on a bolt on car.
Screen Shot 09-22-15 at 01.43 PM.PNG

This is stock Boss 302 VCT
Screen Shot 09-22-15 at 01.42 PM 001.PNG

This is Cobra Jet VCT
Screen Shot 09-22-15 at 01.42 PM 002.PNG

Look at the difference in overlap. The only thing that sets the Boss engine apart from the 2015 that will make a difference is the boss has slightly better heads, the 2015 has a more aggressive intake cam (same as cobra jet), and the Boss intake manifold. This is why I feel the 2015 really needs a boss manifold or cobra jet manifold with the VCT properly optimized.

[txcharlie]

Anyone seen this:

https://www.youtube.com/watch?v=cAlw9RpTZ4I

[SSpdDmon]

So what they're saying is...

Lower RPMs - advance the intake (earlier open/close); retard (later open/close) the exhaust -- results in more overlap?
Higher RPMs - retard the intake; advance the exhaust -- results in less overlap?

Question is - at what point is too much overlap bad because we encounter P2V / V2V contact OR deoptimize flow? I think this makes sense with regards to playing with the cams to improve the power under the curve. Without significant changes to other parts, probably not going to find much in terms of peak numbers. Fair statement?

[SSpdDmon]

http://twoguysgarage.com/tgg-909-2011-mustang/

Go to 9 min mark

[kris5597]

So what they're saying is...

Lower RPMs - advance the intake (earlier open/close); retard (later open/close) the exhaust -- results in more overlap?
Higher RPMs - retard the intake; advance the exhaust -- results in less overlap?

Question is - at what point is too much overlap bad because we encounter P2V / V2V contact OR deoptimize flow? I think this makes sense with regards to playing with the cams to improve the power under the curve. Without significant changes to other parts, probably not going to find much in terms of peak numbers. Fair statement?

Yes to your first statement.

Almost every vehicle comes from the factory with VCT limitation to prevent V2P contact with stock internal components, so that shouldn't be an issue. This definitely work improving low to midrange power, but it absolutely helps with top end power as well.

You must bracket cam angles to optimize the best torque curve, no other way to do it.

[murfie]

for VCT on the 2015 mustang Ive noticed a few extra values under configuration that i dont see in 2011-14 tunes. intake valve closing 239*, intake valve opening 340*, exhaust valve closing 369*. im going to assume 360* is TDC. This could explain alot of the difference you are seeing with the 2015's.

[murfie]

from comparing tunes this is my guess at what would work as a good place to start.

[Higgs Boson]

from comparing tunes this is my guess at what would work as a good place to start.

Am I seeing 23 degrees of underlap at 1000 and 17 degrees of overlap at 7200?

[murfie]

If im looking at this part of the editor correctly things work around 360* and not 0* for top dead center in the 2015 ECU. so if you add 9 to my exhaust and minus 20 from my intake values things may look a bit more normal.

[kris5597]

Am I seeing 23 degrees of underlap at 1000 and 17 degrees of overlap at 7200?

Your actually seeing 5* of overlap at 1000 and 13 degrees of underlap at 7200. In the VCT tables he has listed, he is closing the exhaust valve 13 degrees before the intake valve starts to open.

[kris5597]

from comparing tunes this is my guess at what would work as a good place to start.

How do you figure this is a good place to start? You are going the opposite direction for overlap 6000+ rpm. And, have you confirmed you're actually hitting 24 degrees of intake advance from 1200-3000rpm?

[murfie]

Are you seeing my attachments? They don't show up on my phone. Forgive me if I don't get the numbers exactly right doing this from memory. At 1000rpm I would be getting 34* over lap with the intake opening at 34* before tdc. -14* + 340* to get 326* for the intake -9* + 369* to get 360*. 360*-326*= 34*. At 7200rpm there would be 26*overlapThe key is knowing 360*is tdc and that in the 15 ecu the intake is set to open at 340* (20* advanced from tdc) and the exhaust is set to close at 369* (9* retarded from tdc). You could set the tables to all 0* and get 29* over lap. The 11-14 ecu calculate off *0. Comparing what I've seen in a lot of 11-14 tunes I've came up with these values. I will soon be doing some logging to test my findings.

[kris5597]

I see what your saying. So your saying that with the predefined IVO and EVC positions given in the configuration tables, IVO and EVC are adjusted by setting the VCT tables to a certain advance or retard and then you add that number to the predefined IVO or EVC position. So at the largest amount of overlap, 3200rpm, you are seeing 71* of overlap? Which if VCT follows the VE curve, that should be around peak torque.

My question is this, how to you know that the configuration tables are showing the set IVO and EVC position and that information that you have stated is correct? TBH that would make more sense and show the 2015 engines actually hitting normal appearing VCT compared to all other coyotes.

Kris

[kris5597]

With that information sir, I believe we have a break through. I made an excel document to show 2015 GT VCT and overlap on stock tune compared to 11-14 Gt overlap on stock tune. As you can see on the right hand column, the overlap difference, stock for stock.

[murfie]

A trend I see in tunes is to keep the exhaust closing pretty constant and close to TDC while moving the intake to adjust the overlap. My example doesn't do this and also my be a little aggressive for stock intake and exhaust. the other thing I see is the changes being made are under optimum power which in the 15 seems to be disabled in mapped points. under the mapped points there are variables for IVO and EVC for each mapped point. My guess would be it works similar to timing and theres a percentage pulled for each table to determine the final numbers.

[kris5597]

Yes, the mapped points would also use those values and add up to IVO and EVC positions there too. However, on my vehicle, I have enabled OP mode so I can tune WOT. Once VE is dialed in at WOT, I can trickle down from there to adjust partial throttle VCT for best driveability and fuel economy. All of which will take a lot of time. However, if I'm the only ones that's ever documented and done this, I'd say that's worth the time. EVC position is definitely ideal to stay constant, as in the combustion cycle and the way the valve events work, EVC is not nearly as important as IVO. On engines I have tuned before, the exhaust cam normally stays fixed while you completely tune all cam angles on the intake cam at all rpm breakpoints to find maximum VE at all rpm breakpoints. THIS is the best way to maintain as much torque as possible at all rpms, which result in more hp of course.

Did you review my spreadsheet?