Cobb V3 - Exceeding Target Boost

[d22597]

Just set up a stage 2 tune and wanted to share my thoughts on the new Cobb V3 and get some advice on exceeding target boost. Here is my setup:

 

09 Spec.b, stock airbox/filter, Cobb catted DP, Cobb AP3-SUB-003

 

My first Tune was "Stage2 91 SBv300". Ran good, but was hitting over 17.5 psi (target is 16 +/- .8). So checked on Cobb's site and noticed they have updated tunes. (should have checked first)

 

"v3.01 -Updated calibration to help prevent turbo over boost conditions and to increase the window for knock feedback activity."

 

They also added new LWG tunes for over boost conditions...

 

"LWG: Lower wastegate duty cycles (LWG) for use when normal wastegate calibration produces higher than targeted boost (i.e. over boost)."

 

Next I went with the LWG version "Stage2 91 SBv301 LWG". This tune pulled my boost down to 15 flat (target is 16).

 

Finally, I tried the "Stage2 91 SBv301". This tune brought my boost back up over 17 and hit a 17.7 during a 2500 pull in 5th. (target is 16)

 

Eventually, I would like to get a professional tune and not looking to squeeze everything off of a OTS tune, but in the short term, I would like to make sure I'm being safe with the ots tune.

 

I attached the logs if anyone wants to comment on the tune and how conservative the tune is. (elevation is 800ft, 75deg, RH 58%) I'm not getting any knocks, but concerned with running the higher boost map.

Stg2 91 SBv301 LWG.csv

Stg2 91 SBv301.csv

Stg2 91 SBv301 17psi 6th.csv

[iNVAR]

Your problem is you are doing "pulls" in 5th and 6th. I don't believe your car has "per gear" tuning, which means that the WGDC values dialed in have to be a compromise, and Turbo Dynamics has to make adjustments in the +/- direction to the WGDC depending on gear.

 

As such, the WGDC values are a compromise and work 'best' in only one particular gear. Usually that gear will be 3rd or 4th. So when you pull in 5th and 6th, boost has a tendency to spike up a bit. In your case, you are trying to do a pull in 5th at 2500.

 

If you were on the highway, would you floor it at 2500 to pass another car quickly, or would you drop down to 4th and floor it? If you're lazy, sure, you could stay in 5th and just mash it... but consider this, your gears are:

1st 3.636

2nd 2.235

3rd 1.521

4th 1.137

5th 0.891

6th 0.707

final 3.900

Mine are:

1st 3.166

2nd 1.882

3rd 1.296

4th 0.972

5th 0.738

final 4.111

Your 5th gear is somewhere between my 4th and 5th. And I don't floor it in 5th at 2500, and I rarely ever floor it at 2500 even in 4th. So you really should be downshifting to a lower gear.

 

So I look at your 2nd log, the normal WG one in 3rd gear, and your boost looks just about right, hitting 16, not going over much.

 

Then I look at your LWG one, also in 3rd. Of course you're going to be low. You're using Low WGDC now.

 

And then I look at your last log, and you're pulling in 6th gear from 2300. So I guess the question is, why are you pulling in 5th and 6th gear at such low RPMs? Do you hate your car?

 

Run the normal map, stop doing weird stuff with your car (5th and 6th gear pulls) and you should be fine. Boost comes up quicker in higher gears and it tends to throw things off in your Turbo Dynamics department when you start off at such a low RPM. Also not good for your engine (bogging it down). See how in your 6th gear pull it starts dialing WGDC back massively? You didn't give it a chance to but by the time you got to around 3k you probably would've been underboosting instead.

 

Do a pull in 3rd from 2K, and a pull in 4th from 2500 and see how those two gears work.

 

Then if you want to check, in 5th and 6th gears, floor it around 3K also and see how it performs.

 

P.S. You're logging too much stuff. Get rid of Manifold Absolute Pressure, Knock Active Switch, MAF Volt, AF Sens curr. And before you do pulls, wait until your DAM goes back up to 1. Drive around a few minutes and it'll go up. See how one of your logs starts at 0.875?

[d22597]

Your problem is you are doing "pulls" in 5th and 6th. I don't believe your car has "per gear" tuning, which means that the WGDC values dialed in have to be a compromise, and Turbo Dynamics has to make adjustments in the +/- direction to the WGDC depending on gear.

 

As such, the WGDC values are a compromise and work 'best' in only one particular gear. Usually that gear will be 3rd or 4th. So when you pull in 5th and 6th, boost has a tendency to spike up a bit. In your case, you are trying to do a pull in 5th at 2500.

 

If you were on the highway, would you floor it at 2500 to pass another car quickly, or would you drop down to 4th and floor it? If you're lazy, sure, you could stay in 5th and just mash it... but consider this: *I* don't even do that, and my 5th gear is shorter, and so is my final drive.

 

Your gears are:

 

Mine are:

 

So I look at your 2nd log, the normal WG one in 3rd gear, and your boost looks just about right, hitting 16, not going over much.

 

Then I look at your LWG one, also in 3rd. Of course you're going to be low. You're using Low WGDC now.

 

And then I look at your last log, and you're pulling in 6th gear from 2300. So I guess the question is, why are you pulling in 5th and 6th gear at such low RPMs? Do you hate your car?

 

Run the normal map, stop doing weird stuff with your car (5th and 6th gear pulls) and you should be fine. Boost comes up quicker in higher gears and it tends to throw things off in your Turbo Dynamics department when you start off at such a low RPM. Also not good for your engine (bogging it down). See how in your 6th gear pull it starts dialing WGDC back massively? You didn't give it a chance to but by the time you got to around 3k you probably would've been underboosting instead.

 

Do a pull in 3rd from 2K, and a pull in 4th from 2500 and see how those two gears work.

 

Then if you want to check, in 5th and 6th gears, floor it around 3K also and see how it performs.

 

P.S. You're logging too much stuff. Get rid of Manifold Absolute Pressure, Knock Active Switch, MAF Volt, AF Sens curr. And before you do pulls, wait until your DAM goes back up to 1. Drive around a few minutes and it'll go up. See how one of your logs starts at 0.875?

 

Thanks..I appreciate the help and explanation! I first saw the high boost on the Cobb monitor during typical city highway driving, but wasn't logging when it happened. Then I tried to reproduce so I would have the log. I will keep above 3k when pulling in 5th and 6th from now on

 

 

-Greg

[iNVAR]

I made some edits to the original post, but looks like you caught it before I did that. Your 5th is taller than mine, but your final is shorter

[iNVAR]

How's stuff going with your car? Better I hope?

[d22597]

How's stuff going with your car? Better I hope?

 

Going well, thanks! I ended up throwing a CEL and over boosted during a track day on the Cobb map. I was in third powering out of a corner and was like hitting a brick wall. I loaded the LWG map and ran it for 3 more sessions without issue.

 

I did pull the trigger on a TMIC and in the middle of a e-tune from Cryo. So far, the tune is progressing well!

[iNVAR]

You were in 3rd going into 4th? Or were in 3rd the whole time?

[d22597]

You were in 3rd going into 4th? Or were in 3rd the whole time?

 

In third the whole time. Carousel at mid ohio. Guessing around 3k, but not for sure.

[iNVAR]

Interesting that you'd hit overboost in a steady gear. I wonder what Cobb's limit is. What was the temperature like outdoors?

 

It's more common when you upshift and are at higher RPMs, say 5K in 3rd and shift to 4th and immediately throttle hard.

[d22597]

Interesting that you'd hit overboost in a steady gear. I wonder what Cobb's limit is. What was the temperature like outdoors?

 

It's more common when you upshift and are at higher RPMs, say 5K in 3rd and shift to 4th and immediately throttle hard.

 

It was pretty cold. Maybe low 40s. First run of the day and last corner of the first lap. There is a chance I was in 4th since I was taking it slow on the first lap on a cold morning, but thought I was in 3rd.

 

It happened right after I passed the entrance to the pits so it was a very frustrating and embarrassing lap with a light show on the gauges :-/

[iNVAR]

Yeah. Well, I'm sure Cryo will take care of it. When you custom tune things, they're dialed in better. But to be perfectly honest, if you plan on regularly tracking the car, you should learn how to tweak your maps on your own and as well. That's not a knock against Cryo, or any tuner for that matter. It's just that when you start driving it hard, you should be monitoring things and making adjustments when necessary. The amount of hours (hundreds at least) I've put into my own car's map to make it safe and knock free you simply can't expect any tuner to devote that much time to it no matter how good.

[d22597]

Yeah. Well, I'm sure Cryo will take care of it. When you custom tune things, they're dialed in better. But to be perfectly honest, if you plan on regularly tracking the car, you should learn how to tweak your maps on your own and as well. That's not a knock against Cryo, or any tuner for that matter. It's just that when you start driving it hard, you should be monitoring things and making adjustments when necessary. The amount of hours (hundreds at least) I've put into my own car's map to make it safe and knock free you simply can't expect any tuner to devote that much time to it no matter how good.

 

Agreed. I'm not sure if it will be on the track all that often, but I do plan on getting more familiar with reading the logs and making small changes.

 

Just finished some pulls and sent more logs to Cryo. Still have a ways to go and already smoother than the Cobb ots map!