COBB Accessport Custom Feature Overview

[Darkrune]

Please explain how it drops to -9 psi.

When you take your foot off the gas it goes into vacuum. Which is why -9 psi is obtained during transient power curves. Idle vacuum is around 3psi.

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[kevg73]

How much vacuum does the 2.3 create?

From my experience in my EB the boost gauge on the dash drops down to at least -10 psi when I lift. Don't know exactly how accurate that gauge is but I would say their claim of -9 psi seems very reasonable.

 

[Herr_Poopschitz]

From my experience in my EB the boost gauge on the dash drops down to at least -10 psi when I lift. Don't know exactly how accurate that gauge is but I would say their claim of -9 psi seems very reasonable.

465-517 mmHg.

 

[Darkrune]

465-517 mmHg.

It is more common that vacuum be measured in mm of mercury, for the car industry, they moved away from that for simplicity of instrumentation purposes.

 

[COBB Tuning]

Does the accessport retain the selected mode after shut down or do you have select the tune you want every time you start the car?
My biggest and so far only gripe with the car is having to toggle to sport+ mode every time I start the car. I like sport+ mode and want it to stay in that mode until I decide to switch.
mike

Once a specific tune is flashed to the ECU, it stays there until the ECU is re-flashed again. Each tune has different map slots. Check out the map notes to see the different options. The map slot you select will stay the same until you change it to something else or re-flash the ECU with a different tune that has a different number of slots. If it's the same number, the slot you were previously in will be remembered even on a re-flash. The default setting for the first time the car is flashed will be slot 1 (max performance).

465-517 mmHg.

This equals 8.99 - 9.99 PSI. Source

The exact values aren't super relevant as they will change slightly across different cars in different conditions. However, every turbo car using this feature will have very similar shaped graphs. The real point is that when using FFS, you lose a lot less boost pressure between shifts. FWIW, the data from this graph was taken on a Subaru but is still useful in showing the benefits of FFS.

Please explain how it drops to -9 psi.

When the throttle closes it forces the Bypass Valve open and depressurizes the intake tract. When the intake tract isn't under pressure, it's in vacuum.

From my experience in my EB the boost gauge on the dash drops down to at least -10 psi when I lift. Don't know exactly how accurate that gauge is but I would say their claim of -9 psi seems very reasonable.

Both of our cars are high on lifts right now so I can quite see the gauge. But, I'm pretty sure the negative, or vacuum, side of the boost gauge is in inches of mercury (inHg). If that's correct, when you lift, it'll probably be closer to a negative 15-20 as a value. In this specific example, it made better sense to use the same unit of measurement when graphing the data.

Kyle@COBB

 

[Herr_Poopschitz]

This equals 8.99 - 9.99 PSI. Source

The exact values aren't super relevant as they will change slightly across different cars in different conditions. However, every turbo car using this feature will have very similar graphs. The real point is that when using FFS, you lose a lot less boost pressure between shifts. FWIW, the data from this graph was taken on a Subaru but is still useful in showing the benefits of FFS.

When the throttle closes it forces the Bypass Valve open and depressurizes the intake tract. When the intake tract isn't under pressure, it's in vacuum. In this specific example, this car pulled ~-9PSI. Usually vacuum is listed in mm or inHg but it makes better sense when seeing the data to use the same unit of measurement.

Kyle@COBB

Brain fart. Too much working in metric. I was confusing mmHg w/ in. Sorry about that. Carry on.

 

[Nick@JDM]

My explanation is probably not correct, but negative boost is indicating vacuum. Which is just like any other NA car, in that the pistons are "sucking" air in instead of air being forced in.

This is correct. When you let off the gas the throttle body closes and the bypass or blow off valve opens. The bypass or blow off valve vents or recirculates the boost pressure since it is not needed for off throttle situations.

The engine will then start to pull air in creating a vacuum in the intake manifold. Typically you will see around 22-24 inhg of vacuum (below 0 on a boost gauge) at idle on FI and N/A cars. When NA cars go WOT the gauge will fall toward 0. On FI cars you will start to see boost pressure in PSI once the needle crosses over 0 vacuum.

In short, two different units are typically used to measure pressure on the same gauge. Boost is in pounds per square inch (in America) and vacuum in inches of mercury.

 

[Renner]

Sub'd

 

[OVRKILL]

COBB, I have put about 1,000 miles on my AP3 so far and I'm really enjoying it. Is it possible to make the tach drop a bit faster during upshifts? Waiting for the revs to drop after turning onto the highway isn't safe here, so I've been putting wear on my clutch and upsetting the car by releasing the clutch early.

I will have a custom tune from someone in your network after I install an intercooler.

edited! clarity

 

[dragonacc]

COBB, I have put about 1,000 miles on my AP3 so far and I'm really enjoying it. Is it possible to make the tach drop a bit faster during upshifts? Waiting for the revs to drop after turning onto the highway isn't safe here, so I've been putting wear on my clutch and upsetting the car by engaging early.

I will have a custom tune from someone in your network after I install an intercooler.

Are you talking about wanting the revs to fall faster while you have the clutch engaged before you shift to the next gear? You should put a light weight flywheel in. The Ecoboost uses a heavy dual mass flyweel if I'm not mistaken and that will cause the engine to change speeds up and down slower.

 

[OVRKILL]

Are you talking about wanting the revs to fall faster while you have the clutch engaged before you shift to the next gear? You should put a light weight flywheel in. The Ecoboost uses a heavy dual mass flyweel if I'm not mistaken and that will cause the engine to change speeds up and down slower.

I figured that the slow drop was ECM controlled to prevent a rich spike. That could very well be the cause. I had no idea that a flywheel/clutch could have that much inertia.

 

[dragonacc]

I figured that the slow drop was ECM controlled to prevent a rich spike. That could very well be the cause. I had no idea that a flywheel/clutch could have that much inertia.

According to WMS the stock flywheel/clutch combo weighs over 60lbs. Real heavy.

 

[Papaya]

*Bumb*

Is COBB still alive? 1st a lot of posts about the product and now nothing anymore. :shrug:

 

[wireless]

They aren't very active on here -- they will jump in for a bit and then vanish haha

 

[greg hazlett]

Sounds like some other vendors, lol!

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