[Terry @ BMS]

Hi guys,

We come across this issue often where customers don't understand how the global boost safety setting works and trigger annoyance failsafes when in fact nothing is actually wrong.

The current boost safety logic:

1) User enters the boost safety on user adjustment page. Default is normally 18psi.
2) The JB4 is programmed to target no more than 1/2 below this safety boost level regardless of map definition.
3) If boost exceeds the safety setting for more than 1 second the JB4 reverts to a safety map.
4) The boost failsafe also doubles as the in dash boost gauge "max" reading.

Proposed boost safety logic:

1) The "boost safety" field is reassigned to some other task. The max boost gauge reading is set based on the boost sensor. 20psi for 2.5bar, 36psi for 3.5bar.
2) The JB4 is programmed to trigger a boost safety switch IF boost exceeds the map target +2psi for more than a second on twin turbo firmware, or +3psi for more than a second on single turbo firmware.

Possible issues will crop up when running out of the boost sensor range. So in these situations the boost safety will consider the sensor being used. e.g. a 2.5 bar can't have a safety higher than 20psi, and a 3.5 bar can't have a safety higher than 36psi.

Thoughts?

[Payam @ BMS]

I like that idea.

[PrzeChuj]

I like it to.....

[weebles]

I feel like the gauge setting would be kinda crappy for people with 4 bar sensors like myself.

[yellowfin]

I'd still like to be able to set max for dash gauge.

[wwwROLL TIDEwww]

Sounds reasonable, if I understand it correctly.

But I have question for the current logic...
So for stock twin turbos, would one need to manually set the boost safety to 36 in order to achieve 18 psi w/out triggering boost safety?

[Terry @ BMS]

Originally Posted by wwwROLL TIDEwww

Sounds reasonable, if I understand it correctly.

But I have question for the current logic...
So for stock twin turbos, would one need to manually set the boost safety to 36 in order to achieve 18 psi w/out triggering boost safety?

If the boost target of the map is 18psi, then the boost safety would be 21psi (map target +3psi), unless equipped with a 2.5bar TMAP sensor which would cap the safety at 20.5psi.

[Tuppidsay]

Sounds like a decent change except for the changes to the gauge, unless your gonna come out with gauge backs for each tmap sensor. (please) Ie if target is half of set boost its easy to see on the gauge where boost should be, half. Not so if its done the way you propose. On the other hand doubling set boost is not good practice or safe for those running high boost. I'd vote to implement your safety changes but leave the area for scaling the gauge. And bms boost gauge faces......

[wwwROLL TIDEwww]

Thanks for explaining and being patient with my ignorance.

[Rushan]

The stock tmap can reach 21 psi? Or 20 psi?

[LessIsMore]

I vote yes on this. Should have been this way all along, IMHO.

[Payam @ BMS]

Originally Posted by Rushan

The stock tmap can reach 21 psi? Or 20 psi?

20 Psi is the best to be safe.

[hardparker]

Make that +2 or +3 deviation from target adjustable and I'd be on board. Otherwise, I like it the way it is.

[Terry @ BMS]

Originally Posted by hardparker

Make that +2 or +3 deviation from target adjustable and I'd be on board. Otherwise, I like it the way it is.

Whatever it is will be fixed. The idea is to remove user adjustment that isn't really offering much benefit.

The boost setting could easily be retained for the in dash gauge window though. Another idea on the in dash gauge would be to have it auto scale per map. Where 80% on gauge is 100% of map target, 100% on gauge is over target 20%, etc.

[QKRTHNU]

Could you also factor in the FF and DutyCycle values to see if boost control is improving or if it's indeed out of control? That might be better than just a fixed threshold. Then maybe a second hard limit set higher.

[Terry @ BMS]

The boost safety is more of a catch all. I'm afraid if we try to layer in too much additional logic we'll defeat the purpose. For example if boost jumps 10psi over target but is slowly dropping down so it's 7psi over target after 1 second. We should still trigger the safety IMHO.

[THE BEAST]

I feel its a good idea. Not much difference other than making it more simple.

[luchocamp]

I like the idea.
It is safer for new models.

[Roi354]

Bear with me as I'm very new to all this...

I think I'm having this issue described here - If I accelerate from around 3000rpm then everything is fine but if I drop 2 or 3 gears (DCT) and go WOT from 4500-5000ish then I get map 4 and a double blink.
I was wondering if it's because of the spec - '09 UK spec 335i DCT, DCI, d-ps, latest f/ware JB4 G5 + MHD BEF, BMS meth with 1xCM5 50/50, BUT stock TMAP.

I was thinking maybe I should change the boost safety to 20 from 18 but do you think I should be looking at the 3.5Bar TMAP?

[Zackman218]

I keep getting flashed to map 4 for overboost. Mod list includes: jb4, mhd bef, ******* **, upgraded arm intercooler, gfb dv+, arm intercooler piping, arm charge pipe, walbro 450. I'm targeting 18 sometimes even 19 psi in map 1 and have solid afrs but I keep getting flashed into map 4 for overboost since fail safe is at 18psi. Just wondering how to raise to 20psi to max out my 2.5tmap?

[SPANKY]

The safety is dependent of target correct?So for example,one day if I decide to run more boost with meth and another day less boost for testing,whatever that target is at that moment it will be about a + 2/3 psi over target safety correct?i am using a 3.5bar,if so I think that's a good implement,takes the worry out.

[Payam @ BMS]

Correct, it goes by each map.