There is a check balance for when the ECU puts vacuum to the waste gate and air density detected from the MAF and MAPs. If they are too far off then it can trigger limp.

There is a couple reasons people are getting boost cuts. The ones that get it from spikes alone should just have their maps altered and see how dropping peak boost a few PSI does. On the dyno we dropped from 20 max to 18 max psi and only saw a max 2-4 hp/tq loss. The graphs from the 2 maps were almost line for line. I never got a chance to road test, but in theory it may help at almost no loss to power.

 

Here are 2 datalog graphs...both are 3rd gear pulls.

First one has no cut....notice how it doesn't reach 22 and all is fine:


Boost cut, notice it exceed 22 and immediately cut....I stayed at WOT even after the cut so you can see the whole idea a little better.


At the point the boost cut occurs, wastegate duty cycle drops to 0 and stays there, along with the BPV immediately being activated. AFR's continue down as if the boost cut never happened.

These are just two examples...I have plenty other logs, some where I do a 3rd to 4th shift, some where I get a 2nd gear cut, some with a 5th gear cut, some where I roll into WOT and still get the cut, albeit later than if I just mashed the throttle. All have one thing in common though: 22psi.

I also think what Mike was saying was true, some people are seeing cuts because of a load limit being exceeded. I don't think that's the issue with mine though, its distinctly a MAP sensor issue. And has nothing to do with the BPV. Got it on stock JCW BPV, got it on the 710D, and got it with a stiffer spring.

 

Did you ever try blasting your heat on max? lol
I am really surprised that once i did this I had 0 boost cuts after multiple hard runs, right after having had them non stop two minutes before that.

 

Saw your post the other day. Assuming what you found, it may suggest a water line temp sensor is sending a signal that is either good enough (heat on, water cooling effect) or not (no incremental cooling) to trip the boost cut. Don't know the car near well enough, but have you looked for a water temp sensor in the cooling system downstream (return side) of the heater that could be it? I'm guessing it may be on the return side if it is just localized cooling, but I suppose it could be the overall cooling system and temp too. Could play with something like wrapping the relevant sensor in a cold pack temporarily to see if it has an effect. If so, maybe change out if defective, or add a bit of resistance.

 

Tried max A/C by any chance? Counterintuitive, but on a lot of cars when you spin up the cooling fans all the way--by going full blast on A/C if car is configured that way--even w/ the added A/C load at the refrigerant cooling panel you may be able to drop the water temp some. Easy to try in any case.

 

Yeah, I wasn't watching my boost levels after blasting the heat, but I'm assuming it never hit 22. If it was hitting 22 and not cutting that'd be very interesting. I haven't tried with the AC yet. However I've read people saying with AC on the ecu will bring water temp down to 195 or 205 instead of 215, but I have watched this and seen no change in the op temp.
If there is indeed something with the sensors with having the heat on, even though op water temp was still at 215, maybe Jan or tuners could find something related to fix this...

 

I think we are missing the point here guys...

We are trying to find the cure using weird techniques. In the meantime we are prone to catch a cold or sweat our @ss off.

Our biggest concern should be if there are consequent effects from the boost cuts when reproduced so many times.
Is there short or long term problems caused to the engine internals?
For example, piston rings maybe?
Most boost cuts come together with a violent misfire and a big bang from the excess fuel in the engine. These violent misfires, I am pretty confident, will induce cylinder leakage.
I did a cylinder leak down test the other day and it indicated cylinder pressure leakage into the crankcase which dictates piston/ring problems on cylinders No. 2,3 and 4!

 

Mine were never accompanied by misfires...they are very undramatic cuts.

However, what you said about the pistons is seemingly becoming quite an issue.....you're going to see a lot of that happening. Mark my words

No more 22psi for me.

 

I rejected the 22psi setting a while ago as well, but as the test results indicate it was a little late for my pistons.
And imagine, I never asked for it.
Anyway, consequently I lost some power as well (nearly 15whp) and that sucks too...
Guys, I would advice you to do compression and cylinder leak down tests if you are experiencing boost cuts accompanied with misfires like at this video, which shows my car on a dyno, testing boost cuts. On the left side of the steering wheel is the boost gauge. Watch closely the cuts being reproduced 4 times. As soon as the boost climbs up to 1,5bar/22psi it immediately drops to 0,6bar. Two of the boost cuts are with misfires (the 2nd and 3rd i think) and two without. If you listen with caution you can hear the bangs from the exhaust on the 2nd and 3rd boost cut.
Here is the link:
http://www.youtube.com/watch?v=C6qJX...e_gdata_player

 

I have boot cuts but not accompanied with misfired, it's a very "quiet"occurrence.

I get 'super knock' on a different occurrence, first hard acceleration after a cold start (as in after a night sitting ans going to work and oil temp is at operating temp, not when engine is cold)

 

Yes, sorry to say but your motor is toast.

 

Thumper do you have a graph lay out like this that shows multiple parameters on the same time line? I know you have a general idea of whats going on already, but I just wanted to see what the other sensors were picking up at that same time for comparative reasons.

I would post mine but I don't have access to tunign software at this moment so I can't view it. Still irritated about having the ability to log data, but can't view it.

 

I'd have to make them in excel....

 

If your car is cutting boost,throwing knock codes, ect and it can't be avoided under normal driving conditions, then you need to stop driving it until you make the needed changes or repairs to fix it.

Right now there is only a small amount of people tuning the US R56. When you consider that most people cars are either RMW or Alta/Cobb tuned then your list goes down to about 4 or 5 people that have most of the data trying to figure this out.

That's why I said if you have graphs post them so more people can look them over or data log your car and send them to your tuner.

The realistic truth is that we got hosed with the R56 and the way the ECU works. It's going to take time to fully understand it even with the tuning abilities we have right now. So if you want your car to stay operational then you may need to dial the power back a bit in the mean time until some one figures things out a little more.

 

I couldn't agree more with what you said.

19psi will do the job. Mine had a better power curve pulling strong without loosing its steam close to the redline, compared to the 22psi map.
A little less in absolute numbers (-5whp) but way better drivability and response, no boost spikes and lower EGTs.
I wish I have done that from the start...

 

The thing is my map is tuned for 17 psi...
Its when it gets hot that there are spikes/creep/ecu compensation for voltage readings to up the boost, which then hits 22psi.

on a separate note,

Had AC on, on my way home last night after work (~65F outside), got a boost cut. Water Temp was @ 220F. I gotta try the heat trick again and see what the IAT and Water Temp are and how high boost gets. It could be as "simple" as tuning the ecu to run cooler water temps, or even a cooler thermostat if one exists for the R56. I say "simple" in quotes because who knows how deep down those parameters are. I remember someone saying Jan was able to keep their car running at 195F, but haven't really seen it...
Wish I had a data logger to see all the parameters when car hits the boost cut.

 

Theres an app for that.


In all seriousness though data logging software is not that expensive

 

Look into a linear throttle map from alta... I have had mine for a while now, and when I switched back to stock throttle mapping yesterday, i found the car to be un-drivable because of the same reason. Also, I live in florida so its always 90+ degrees here.

 

Maybe I missed it, but im a bit confused, whats the linear throttle have anything to do with the boost cuts? My last map was a linear throttle and it was WAY too twitchy, but it didn't change anything with the boost cuts still.
I'm looking into the NCS expert for some programming things, can that do live data logging on laptops I wonder?

 

Trying to figure out why you get cut so fast, my map is 21 max and i have hit actual cut where the wastegate dumps one time i wonder what variables im missing bcause i wanna try to figure out your solution.

 

Im sure its a separate issue now that you mention it, but when I had my non linear map on id hit about quarter pedal, the car would go all out then all of a sudden, nothing, it would just drop out of nowhere as if i let off the gas almost completely.

However, aside from that issue ive never experienced any other boost cut...

 

You quoted me on that, I don't think you directed your quesiton at me though, right?
I'm rmw tuned

 

Touche i mis read

 

Your car can be set up for 17 psi and still spike to 28 if the ECU didn't step in to cut it at 22. It's all a matter of how the waste gate is reacting or being controlled.

220 deg. is normal operating temp. The radiator fan will not even come on till about 230 deg on stock cars. The thermostat is controlled by the ECU. With the AP I can have the map written to open it at any temp. My car runs around 190-200 all the time. Jan can probably do the same. Any case your ECU should not cut power if it sees ECT's in the 220 range since that is normal temp.

High IAT like 140's, will cause the car to pull timing and boost, but usually it just backs it off ,not a full cut. I can see it cutting boost though if it got too high, I have just never seen it.

It's going to be tough to figure out with out knowing what your car is doing at the time it cuts. Really need to have some one look at the car or data logs.