So my car is behaving strangely. I got a tune yesterday from one of our local tuners and the car was spiking around 24-25 psi then tapering to around 17 at redline on the dyno. Great tune! No CEL's/ limp mode for the overboost condition. It was holding boost perfectly...

As soon as I get it on the street, I pull 2nd gear and it spikes to 27 psi and I throw the p1235 overboost code. Tuned using the OEM boost control solenoids. We turned the wastegate tables waaaay down to get it to behave better, but I'm still getting a big spike in 2nd and 3rd gear pulls and the CEL/ limp mode as a result. So my questions are as follows:

-Are there tables that can be altered that will allow for a bigger spike of boost before the CEL is tripped? I know this is not fixing the issue, but I'd like to retain the OEM boost control instead of going the MBC route.

-Why would there be such a significant difference in behavior between the dyno and the street? It was spiking no higher than 25 psi on the dyno and then it just jumped up to 27 psi on the street...

-Is it possible that replacing the OEM boost control solenoids with the Perrin 3 port would help eliminate these issues?

My tuner has done 3 other EVO X's and none of them have had this problem with the boost levels changing so drastically from the dyno to the street, so any help or suggestions would be much appreciated.

 

You can change the boost limit tables to allow more boost, but I wouldn't recommend it. The right way to fix this is to alter your boost target engine load and reactive/passive WGDC tables to achieve good boost on the street. You can easily tune it for 24 psi peak tapering to 17 psi on the street. The reason you see such a difference is most likely that the load and airflow that the car was seeing on the dyno is not the same as the street. Your car may have been heat soaked on the dyno too, and unable to make as much boost. The best thing to do at this point is to fine tune it on the road. See if your tuner is willing to help you with that.

 

Gotcha. My tuner is a great guy, so he's willing to do some street tuning with me, we just ran out of time yesterday. I'm trying to learn more about this stuff, so it's more or less where should I start and what should I look at.

I noticed there is a setting that can be changed for the time over the boost target it allows before the CEL is thrown. Do you see any issues with altering this time after we get boost where we want it to compensate for say differences in temperature and the occassional higher spike that would result, or is that perhaps playing with fire??

 

Might have to play with the boost solenoid tables a bit to rope in the spikes, although sounds like you also need to boost the numbers some what in the Airflow and Torque limits tables as well.

Depending on the Dyno there is usually more load on the car when on the street. Mustang Dynos usually are closest in that respect but it's still not quite the same.

 

We'll get it worked out. The good news is I finished laying all that sod yesterday.
cam

 

Nice! Hopefully it didn't take until midnight! No lack of faith here, just trying to learn more about this stuff so I can help if possible. Thanks again Cam!

 

1235 is not a overboost code. I keep seeing this posted but it's incorrect.

You can trigger it with the load limit all maxed out and error correction totally off and logged loads not even getting close to any of it.

Torque/airflow tables...

 

Understood... so the torque and airflow tables are where to get started.

I was hoping you guys (GST) would chip in...

Thanks!