Here are two videos of my Mini on a dyno, testing the boost cut at 22psi.

http://www.youtube.com/watch?v=1isLgxf9YmI

http://www.youtube.com/watch?v=C6qJXEsUhew

Any updates on the problem yet from anyone?

 

http://img824.imageshack.us/img824/4...anpic000c1.jpg

Lower red line is torque without over boost function
Upper red line is torque WITH over boost function

Lower blue line is power without over boost function
Upper blue line is power WITH over boost function

As you can see the boost cut comes at 4300rpm and it's a 50bhp immediate decrease in power.
That is exactly what we are experiencing when driving and boost cut occurs...
That kind of power drop off is like you hit to a wall!!!

I will try a different approach trying to heal the boost cut. Maybe tweaking the upper limit of the voltage from the sensors sent to the ECU will be the answer.
Has anyone done that?
keep this thread alive...

 

Since winter has come (North East USA), the colder weather (<35deg F) most days (~1C), I have not experienced the boost cut anymore. This leads me to believe that even with overboost I am still holding under 22psi, but when the car really heats up (from heatsoak), it is adjusting the ecu by raising boost, which hits the cut.

I always wait until my water temp AND oil temp has warmed up before I flog on it. Even with repeated runs and hard driving, the cold air hitting the FMIC (stock) keeps the temps down, and the cold in general helps cool the engine. The car runs VERY strong in the cold weather for sure. I also do not get the stuttering at 125mph and above like I did in the hot, where it felt like a fuel cutoff and you'd get bursts of acceleration and no acceleration, about 2 times a second. This would be accompanied with backfiring through the exhaust (backpressure pops). Sounds cool but not in terms of performance.

 

The same temperatures over here as well <35F or <1C. I have a forge IC so my intake temps are lower than yours I assume. I drive the car with the same rules as you, and I do not think heatsoak is an issue. When you hit the gas gently everything is OK, but when you are hard on the gas with immediate pressure then there is it...Boost cut...
Watch the videos carefully and you will understand what I mean.

 

I know what you mean, the same thing happens to me too. What tune do you have though? I think the difference here is our parameters are set up differently. My map is set to 19psi, but with overboost hits 22psi when its hotter. Thumper has the same experience I believe, is when his car runs hotter it hits the boost cut more often.
Your boost levels maybe set a little higher, which is why you may see the 22psi cutoff more often, thus not making it related to the ecu compensation for higher car temps.

All in all we are all seeing the boost cut when we hit 22psi, it just depends how and when we all hit it is slightly different.

 

I totally agree with you.
19psi is the most frequent boost pressure that I see as well.
We are discussing this problem some time now but I did not yet found or heard of a solution from a professional or a simple member of this forum or other including my ECU-tuner, and this is a little disappointing.
How the h@ll does anyone drives his car with instants 50bhp drops, without being dangerous on the road, is beyond my logic.

I have faith though...

 

This sounds like the issue I have with Jan's High boost tune! I should have read this sooner. My car will boost strong all the way to 19PSI but then start to stumble If I let off on it, boost is gone.. I will have to drop the RPM down to about 3k rpm for it to build boost again! No CELs and no limp mode just no boost till I drop the RPMs back down.

 

Welcome onboard!
What did you do to fix the boost cut?

 

Jeff @ Alta has said in another thread, they are aware of the issue and has said they are working on a MAP sensor solution.

 

took the tune off the car. I have 3 versions from Jan, The original one with a really weak 1st gear but a good solid tune over all. boosts to about 17-18psi, another one he titled Boost cut and the "high boost" one with the issues. The high boost tune is a beast but the top end where I can run it on the autobahn turds.. Most people in the states will never have the issue with this tune because they will never run the car as fast as I do. Right now I am running the stock map because of the weather and snow tires because I want some traction right now.

 

No boost cut anymore!

I lowered the AMP boost pressure to a maximum of 19psi with the overboost function engaged and the boost cut dissapeared.
Thank you Czar.
The stock turbo now is working better and no boost creep occurs.
At high speeds it does not loose its grunt and overall it produces pretty much the same HP and torque figures.
Having said that, i should also state that with the revised boost pressure it is a little better on the higher rpm (the turbo does not loose its breath from boost creep-spike) and it is the first time that the engine produced the peak horsepower after 6100rpm.

I am pretty happy for now, but always wanting more...

 

I'm not sure if im on point with this conversation, but I might be able to add something to this topic. What you guys are experiencing is a normal safety function of the car and nothing more. there is a given value for each load cel. the value equals max boost allowed before the DME recognises a problem. You guys are turning up the boost to a point where the car thinks theres a problem.

solution. either remap the table that see's over boost or use a fuel cut defender. which is basiclly a zenier diode. at a certain voltage the defender will just cap the signal out and keep it from giving a value that throws the overboost code.

The problem is that there are plausibilty checks out the *** with these cars. if you cap the boost signal, there is going to be a cel. Your only option is to remap the dme to allow values past what the car considers over boost.

 

Again, it is a hard ECU to manipulate and there is no need after all. Crazy boost pressure will not give us extra power. What it will do is actually induce excess heat, which means extra strain to the internal parts of the engine and will definitely shorten it's life.
That is MY opinion on the subject.
Czar, who is far more knowledgeable can chime in and explain more detailed what's what...

 

boost Creep and boost spike are both products of wastgate control. The problem with running higher boost levels is that the volume of exhaust gas leaving the waste gate is to much for the gate the handle. The pressure builds to a point where the amount of exhaust leaving the gate is engouh to cause the boost to rise.


The boost sensor can affect fuel and timing but its nothing that cant be tuned for. The maf is using the boost sensor to fiugre out how well the intercooler did its job. when the intercooler is doing its thing in the early RPM's the car adjusts to add more fuel to meet the new density. but once you pass a certain point (especially after driving for a while). the intercooler cools at a much more, linear rate which makes tuning easier to get right. Your only real problem is tricking the DME into thinking you havent touched it. To get it right you would have to wire both map sensors to see a cap. Even then There is going to be a boost level that DME will see and decide that there is a problem. So it can work but only to a point.

Crazy boost pressures will get us crazy numbers, you just need to keep the heat down.