Sale ends todayGet 30% off any course (excluding packages)

Ends in --- --- ---

Variable Cam Timing and VE

General Tuning Discussion

Forum Posts



Tech Articles

Discuss all things tuning in this section. News, products, problems and results. 

= Resolved threads



I have been building up a VE table on my Focus ST - the COBB features allow me to run the car in OE mode (still speed density) and model/log the calculations based off the OE tables and logic as well as log the same from the VE table I am building. I have been logging all sorts of different driving conditions to form my table and I think I about have it ready.

My question is in regards to VCT timing - and how it affects (in general) VE as I have this compensation table that I can use, and looking to get some base values in there but not sure what effects I should attempt to model. I would thing VE would increase as you advance the intake, but unsure. I have these tables for both intake and exh cams.

The reason I am doing this is the OEM model calculates VE based on a very complex calculation, which uses 15 tables, each models after a camshaft VCT pair position. So building this table lets me operate in a more 'standard' SD tune that I can actually look at and understand, verses the complex tables/math the OEM system uses on the Ford Ecoboost.


I attached what the VCT compensation tables look like and also my VE table as it stands right now. Any feedback would be welcome :) I only reach ~37 MAP max so beyond that is where I am kinda making it up and attempting to keep it safe if it ever winds up in those areas... My turbo is SMALL so VE does seem to trend down in the higher RPMs in its current state.

Attached Files

The stock system works in such a way that, as you adjust the VVT angle, the VE is still correct. If you don't plan to adjust the VVT tables, you can mostly get away with not using the compensation table. You tune the single VE table and you're mostly done.

Why are you switching away from the OE speed we with system? Is this a learning exercise or a long term plan? I wouldn't do that on a car with just bolt ons.

Hi Raymond,

This is a learning exercise as well as an attempt to more closely model the VE of the engine. I am seeing LTFT in the 10% range and did correct this a bit using the stock SD tables (the 15 tables related to each cam pair) but tuning that was a pain, locking the cam pairs and taking runs - each time having to reflash. Instead I want to have an actual VE table to look at and with the added benefit of being able to do fine adjustments live.

After several iterations with the VE model just running in the background I flipped it on yesterday and did some gentle driving. Everything looks great in terms of trims (now +/- 3% vs 10+%). It is much easier to grasp what is going on and what I am changing looking at a VE table vs the 15 cam pair tables where I am not even sure what I am adjusting - but rather just know moving the values in a certain direction will either increase or decrease VE for that given RPM and cam pair.

Very curious why you would not recommend this long term for a bolt on (stock turbo) car? Because that was my plan and I do not want to be moving in the wrong direction :)


Before i respond please answer, what exactly is done to the engine and what is your future plan? How many miles are on it?

Do you have catalogs of the engine completely stock (stage 0)?

Hi Raymond,

Apologize, I missed that.

This is a 2016 Focus ST, basically stock, 18K miles, but full list of modifications to the engine/that would modify airflow are:

-Replaced OEM air filter with a aftermarket 'green' filter, still using a close, stock airbox

-Removed OEM resonator in the exh

-Replaced OEM FMIC with a Levels Performance unit

-(not sure if these matter but will mention them) deleted OEM sound symposer, installed a catch can system

The software I am using is COBB Accesstuner and the OEM tables are easily viewed by loading them via the 'compare' feature, which lets me flip back and forth between what I am working on, and either an OEM map or a stage x OTS map. I have not completed the excel file you and I were discussing in a separate thread because this feature lets me compare quite easily within the software itself.

My future plans are possibly upgrading the turbocharger, if I did this it would be kept to power levels that could be supported by the stock DI fuel system as I am not (yet) interested in adding additional fueling.

I run 91 pump fuel, or E30.

Main interest in moving to the COBB VE/SD system is to move away from the complicated OE system into an actual VE table that (at least for me) is more intuitive. This was started by wanting to improve my fuel trims as they were very high, and while I had not done that much to the engine airflow, I apparently affected it enough to throw off the VE from the OEM calibration :)

I just learned from COBB that despite using their SD tables, the OEM ones are still referenced for some of the boost control inputs if you use the OEM controls - that is something that was not mentioned in the documentation but thusfar I have not noticed any ill effects - I have boost and timing pulled back a bit while I am messing around with getting this conversion running where I am happy with it.

Edit: No, I do not have datalogs of the engine from in bone stock state. I could take some from a stage 0 map today, but have not done so.

Since this is a learning experience, go ahead and do those logs with bone stock hardware and stage 0 before going any further.

If you're planning on a turbo upgrade, at that point it will be helpful to go with the simplified VE. Before then it's a judgment call.

Since this is a learning experience, go ahead and do those logs with bone stock hardware and stage 0 before going any further.

If you're planning on a turbo upgrade, at that point it will be helpful to go with the simplified VE. Before then it's a judgment call.

Hi Raymond,

As in go back to the OE air filter/FMIC, etc? I do not have that equipment anymore, I could load up a Stage 0 map and take some logs to compare, but the airflow changes would still be present. What would you be looking for in this case? Just trying to wrap my head around what you might be looking for.

As far as running in this mode being a matter of preference? Could you expand on that? What would be the downsides in your eyes? I am awaiting feedback from COBB on if the issue of the boost control system referencing the OE speed density tables could be fixed by also swapping to their version of boost control. That I would agree kinda stinks because on a stock turbo I do not see it being needed.

The other option would be to modify the OE tables, which I already did through locking the cams in all 15 positions and taking logs - and that got my trims much closer in line. I could continue to do that to dial those tables in but if possible I would like to use the custom VE tables instead. You sound at least slightly objected to this plan however so very curious as to your thoughts on why :)


You need to consider that there's the software and the calibration (the values actually in the tables).

The OE software is way more sophisticated. It basically has a dozen VE tables, and complicated calculations and learning algorithm to account for heatsoak, altitude, etc. Notice how you were able to swap out all that hardware and it ran fine with just some slightly different fuel trims? That's a testament to how robust the OEM software is and how big the margin for error is. Furthermore, since the cam positions have separate VE tables that interacts with the airflow learning, you can run the engine on a dyno and start playing around with boost control and VVT position and your charge air estimation is going to be pretty close if you don't have drastic hardware differences.

The OE boost control system, in a general sense, understands the relationship between accelerator pedal position, throttle position, VVT position, spark timing, and wastegate position. It's all based on a torque model, and that torque model depends on the accuracy of the charge air estimation.

The problem with the OE software is the calibration work load. There's a lot of stuff baked in there that you don't even have access to, and once you get to a certain level of modification it's just a whole lot to deal with. When those tunes are made in the lab in Dearborn they have multiple engine dynos running for many many man hours comparing the calculated air charge (the modeled air) to actual air measured by lab grade instruments. If the fuel trims are off, they know if it's because of the charge air estimation or if it's some other problem like valve deposits, clogged injector, etc. Granted, there is some engine to engine variation, but in completely stock form you'd be hard pressed to beat the stock calibration on the stock software, except with some small adjustments of the VE to account for tolerances in parts.

When you flip the switch and go to the replacement control logic, in some ways you've gone back in time 20 years to mid 90s level controls. Everything is a look up table; it's not based on a physical model of the engine. You don't have the flexibility of a dozen VE tables. Every time you change anything you can throw off all the compensations factors. A lot of the robustness that Ford spent millions and millions of dollars on goes away. It's on you to not screw it up.

You switch to the simplified controls because you have to, not because it's better.

I'm going to quote all the warnings from the Cobb Ecoboost custom speed density page:


CCF SD for Ford has been designed with the purpose of coming up with the best implementation for the unique attributes of the Ford ECU, while allowing for an easy and simplified conversion from the OEM SD models. CCF SD is not like other SD systems that you may be familiar with, including even COBB implementations for other platforms. As such, it is critical that you read through this guide and understand how CCF SD for EcoBoost works before attempting to tune. If you have any questions, we are always willing to help.


There are many unique qualities to Ford ECU logic that can make it challenging for someone new to the platform. If you are new to Ford tuning, it is recommended that you first become proficient at tuning OEM stock turbo set-ups before tackling SD tunes. OEM tuning can be much more forgiving to mistakes than SD tuning.


Any diagnostic trouble code (DTC) related to the manifold pressure sensor will cause the Ford ECU to revert to the OEM tables (as a failsafe). This can result in an erroneous load calculation if the OEM calibrations settings were not altered. If this occurs when the vehicle is accelerating, a lean condition and incorrect timing can result. It will also likely cause the engine to eventually stall. If there is the possibility that any of the MAP sensor related DTCs (P0068, P0107, or P0108) could be triggered, it is critical that those DTCs are disabled in the tune. The installation of an aftermarket MAP sensor (required for SD if the factory MAP sensor is not sufficient) will make it more likely for these DTCs to be triggered, even though there may be nothing wrong with the sensor itself. Please see "Tuning SD – Initial Map Configuration" section for more details.


It is important to understand that after the SD tune is complete for a given car, any further changes to engine hardware that impacts airflow efficiency in or out of the engine can potentially require tweaking or re-tuning of the VE table to avoid fueling/timing issues (due to incorrectly calculated SD load). Additionally, mechanical issues, such as intake/exhaust leaks, and issues related to the aging of the motor, such as combustion deposits and loss of compression, can also impact actual VE. It is highly recommended that a permanent wideband o2 sensor and gauge is installed in the vehicle and that the driver understands how to read the gauge and determine what is normal for their tune.


Any SD calculation, including CCF SD, requires an input for cylinder charge temperature, which is critical to the determination of accurate aircharge via SD. The estimation of cylinder change temperature is accomplished for CCF SD via the CAT sensor input. Generally, when the CAT sensor is in the recommended location (post-IC), the vehicle is moving and the driver is on the throttle, the CAT input can be a fairly reliable representation of actual cylinder charge temp. However, when the vehicle is sitting still (or at low speeds) and the driver is off the throttle (or low throttle), or the vehicle has been sitting with the engine off and a hot engine bay for a period of time, there is the potential for the CAT sensor to become heat soaked. That is, the sensor now reads higher than the actual intake air temp. When SD is active, this would cause the calculated SD aircharge (as well as load) to be lower than it should be, causing the car to run lean (and with generally more timing advance). This effect may subside after the vehicle gets moving and throttle (as well as MAP) increases, but it will generally not be an instantaneous improvement. Knowing this, we have implemented the In-Cylinder MCT Compensation feature so these conditions can be accommodated. Please make sure to take advantage of this feature to avoid heat soak based issues.


Thank you - great insight and that clears up a lot. I think I zeroed in on the trims being off as an indicator that something was wrong, but I knew I could fix it if I calibrated the SD tables to match.

I did start this process by running spring WG pressure, pulled some timing across loads above 1.0 and locking the cams into all 15 different positions and taking logs of steady state, idle, and ramp runs. After being pretty frustrated to find out that the AP3 can only hold 10 logs and I had lost a lot of data that I had to go re-collect I did make adjustments to the 15 factory tables for MAP vs Air charge to match (this resulted in anywhere from a 3 to 10 percent adjustment depending on the table and RPM in the downwards direction, which in this case increases VE, I used the supplemental excel calculator they provide to see how these changes affected a simulated VE table.

Doing this I did see improvements, and once I started reading more into the system I wanted to try out their method, mostly because as I had mentioned above I could work directly with a more tangible table.

But you make great points, this should be an exception when there is no other choice, because you lose a lot of great work the Ford engineers did. I think I got tunnel vision after I was seeing such great progress to my trims as I made adjustments.

So yes, it was a great learning exercise, but if I am on the same page as you are now, you would suggest I instead focus my efforts on the OEM table adjustment to correct trims while maintaining all of the other OE functions.

One thing I found interesting was logging the tune I paid for from Stratified to monitor these OE MAP vs Air Charge tables is that they did not touch them, the correlate exactly with the OE/COBB OTS values - but I do see large trims on that tune as well - perhaps that is not something you get adjusted from them until you go beyond the stock turbo, or pay for their full custom tunes - based on the amount of work involved in adjusting them :)

Once again thank you for taking the time to walk me through this - still learning and got a bit carried away watching Andre make such fast progress working with VE tables for fuel trim calibration and I wanted to work with something similar to experiment :)

Glad you're learning from it. If it comes time to change the turbo or something like that, you'll probably want to make the leap. And if you get another project that uses a standalone or a stock ECU with an old speed density algorithm (say an old 90s GM or a 90s Honda) then it makes more sense.

If you think about it, it's pretty amazing how well these newer speed density systems work. On my '95 Rx-7, which is oldschool speed density you can pretty easily run lean on stock ECU when you start swapping parts out. The Ecoboost stuff (I had a stage 1 Cobb 2015 2.3 Mustang) is hardly fool proof but there's a lot more margin for error in it.

Thanks Raymond, if I had to guess, these Ecoboosts coming with a wideband and fully closed loop fueling is probably what saves us from seeing lean conditions when changing airflow (to a point). Sounds like there is even more than that going on within the logic that I am not yet aware of :)

If you have any tips on adjusting the OE SD tables I would love to hear it (or even if I am on the right track with my method - as I am only touching the MAP to Air Charge tables)


We usually reply within 12hrs (often sooner)

Need Help?

Need help choosing a course?

Experiencing website difficulties?

Or need to contact us for any other reason?