Boost cut/hesitation is killing my AP experience!

[SomnoSpeed3]

Ughh... You know that big boost and then the feeling like the bottom drops out, like the fuel just isn't getting there or something. (I'm a noob and NO mechanic.) It happens most in 2nd gear around 3k RPM and is almost every time. It's so annoying that it makes me want to get rid of the AP but I believe this can be solved or at least lessened. So what is the fix for this? I've read colder plugs, different fuel pump or internals, other things. I'm going to try cleaning the MAF. I read that one as well.
Any other tips (besides bigger and better mods)?

 

[LBV]

First thing to do is datalog some variables with your AP to see what`s going on with your car. Datalog RPM, boost, fuel pressure, AFR, wastegate duty cycle, and timing.

Your fuel pressure could be dipping low in which case you`ll need an upgraded pump or you could be spiking in boost beyond the cut threshold in which case you can up that threshold a couple of psi.

We need to see logs first to help you out.

 

[SomnoSpeed3]

OK, I know how to get logged data but for how long do I log for? How should I drive the car during that time?

 

[LBV]

Assuming you`ve driven the car for a few days already on the map, just stop the car and start logging. Drive through 1st and 2nd normally and then when you get into 3rd and are at 3000 rpm, floor it. Go into the 6000`s for rpm and then when safe to, reach over and stop the datalogging.

Download the csv file from the AP and then post it up for us to see.

 

[AutoEuphoria]

I had the same problem when I had the AP, although my issue was that I wasn't running the exact mods called for in the tune and had a catless downpipe and midpipe.

I would get the upgraded fuel pump internals...it's a good mod to do even if you're 100% stock. I saw fuel pressure nearly double from where it was normally at WOT after the CDFP upgraded internals install.

 

[COBB Tuning]

With the mods you have listed, I would say that it is your fuel pump and not the tune that is the issue. We have seen several cars that once you start modifying and asking more of the fueling system that they need an upgraded mechanical fuel pump. Keep us posted on your findings.

Travis
COBB Tuning

 

[SomnoSpeed3]

Here is a normal 1st, 2nd and redline(ish) 3rd gear pull. Sorry I have no idea how to post this stuff. Hope you guys can understand.
Any help or opinions is appreciated.

 

[SomnoSpeed3]

...and here is one from a dead stop. Same driving.

 

[MS3Zoom24]

ya know idk how to do the maps they put up here and i dont have an AP but at least you could have made an excel graph!!

 

[LBV]

Mmmm. Not much wrong with your logs from what I can see. Fuel pressure is fine that`s for sure.

What`s the boost target on your map? It should show when you connect the AP to the car and view the map on the AP. You`re going as high as 20 psi so your boost cut threshold may be too low (ie. at 19 or 20).

 

[LBV]

ya know idk how to do the maps they put up here and i dont have an AP but at least you could have made an excel graph!!

Actually, when trying to diagnose a problem it`s better to see the actual numbers like he did.

 

[dread]

looks fine to me, you get some knock when you are running lean, but nothing terrible. You need to get a log of the cut happening, but your fuel pressure looks fine.

 

[SomnoSpeed3]

Mmmm. Not much wrong with your logs from what I can see. Fuel pressure is fine that`s for sure.

What`s the boost target on your map? It should show when you connect the AP to the car and view the map on the AP. You`re going as high as 20 psi so your boost cut threshold may be too low (ie. at 19 or 20).

I checked and the map I'm running says the boost max is 18.5. So how do I change that to 20 or so? Should I change it if I can?

 

[SomnoSpeed3]

looks fine to me, you get some knock when you are running lean, but nothing terrible. You need to get a log of the cut happening, but your fuel pressure looks fine.

Well I just took it out for a test after cleaning my MAF and installing the air straigtener (my map calls for a MSCAI w/ straigtener but I did not have one). Guess what??? I could not get the car to recreate the problem! I did four 0-80 pulls at near redline and could had ZERO hesitation or problems! I won't know for sure if the problem is gone for good until I drive it more but so far, it's running better than ever. (crazy)

I'll update as soon as I have anything more. Maybe later this evening.

 

[dread]

If you are using the 103 maps boost cut is set to 20.5 psi on all stage 1+ maps. Yes a/s is required for the ms cai.

 

[dread]

you should reset the ecu

 

[SomnoSpeed3]

Yes I just read that it's max 18.5 but at sea level it's 20.5. I guess that would be my limit, 20.5.

Thanks

 

[SomnoSpeed3]

I plan on reflashing tonight.

Thanks for all the help for this new guy.

 

[AutoEuphoria]

Sorry, not meaning to stir things up but I just find it funny that this post:

With the mods you have listed, I would say that it is your fuel pump and not the tune that is the issue.

was posted by a person who works for Cobb Tuning...and is followed by this:

where fuel pressures are looking very strong.

Again, not trying to stir things up, but that is the same exact problem I had with the AP when I had it. The map said "target 18.5psi" and I was getting 20+. My case is slightly different because I wasn't using the exact mods that the tune called for...so a bit more understandable in my case...but if you're seeing that with just an intake that's kind of sad. Best of luck to you!

 

[SomnoSpeed3]

Well I took a couple more little spins in my MS3 without the datalog and the problem of "feeling like you are letting up on the gas" at 3K or so was still there. Didn't seem as bad or as often but it's still there. I'm going to try and log it happening before I reflash the car.