Dumb Boost Targets Question

[nathaninwa]

That's not the tune that matches that log. and your boost pull is way to short. do a dyno run in 3rd gear or get a 1-2-3 drag type pull and post that log and msq

[NigeT]

That is strange. The tune has been gradually evolving by small changes (and boost target table changes to help me test the bias table settings). I restored the last restore point time stamped prior to the log to try to get the matching one. I guess I'll have to recheck that.
I don't have access to a dump, and have little spare time, so I've been using the recent few days of unusually good weather to log whatever data I can from my commute to from work. This was just an oddity that I saw in the log - since (boost target + boost tolerance) > MAP I couldn't understand why fuel was cut.

How close to boost target does MAP need to stay during a boost pull to be happy that the bias value is good? Is around +-5kPa reasonable, or should I ensure it always falls slightly short if target (in Setup Mode)?

Thanks.

[nathaninwa]

I meant a dyno type pull in a safe area, 3rd gear from 2000 to redline

I'm happy when less than 10kpa on target

Bring up status 2 in the datalog. It hits 64 which is boost cut. Right at 170kpa. The tolerance is the KPA under overboost number that things turn back on

[NigeT]

Thanks. I've been trying to get in the longer full rev range pulls where safe. This was just a normal spurt of acceleration.

Would the overboost have been detected between logged data samples? That would make sense. The status2 value is a good tip - I was going to dig around the doc for exactly that.

I thought tolerance was how much above target MAP can go before boost cut and hysteresis was how much it had to fall below target before boost resumes - have just got that backwards? From memory the values are both 10kPa.

When you say you are happy with "less than 10kPa on target" do you mean MAP <= (target + 10kPa)?

Thanks for your amazing patience.

[nathaninwa]

I reread the tool tip. Sounds like the tolerance kinda ignores the overboost number and gives you a following overboost. So your tolerance was 10kpa, target was 160, so when you went 170, it overboosted

You might need to open that window up some. I target 240 with an overboost of 270. This allows for some variance without going into spark cut

I'm happy with 10, let's say 10ish. If I target 240, and I can land 235-245 I'm done with that row. Depending on movment, il let a 232 slide knowing that 10kpa is less than 1psi, something we're just not going to feel

If it gets greater than 10, I'll work on it so I don't creep into my 20kpa delta territory

[NigeT]

I was wondering about increasing the tolerance a little, irn seeing some variance in boost achieved for the same bias on different runs (at similar rpm). My overboost limit is I think 200kPa and higher boost target 185kPa, so would it be reasonable to set tolerance to say 15-20? Maybe the high end to allow a bit more flexibility at the lower boost targets.

It sounds like target +-5 is what I should be shooting for. I think I'm in or very near that for 140 and 160 targets, just need to verify 175 and 185 targets. They are only used for the higher rpms to bolster torque where it is dropping, so may be harder to get a reading for.

Then it's on to getting Basic or Advanced Mode to work. I've tried Basic Mode a couple of times since going to the 1.4 firmware but just got loads of over boost (tolerance) fuel cut (catalytic converter).

Thank you.

[nathaninwa]

If it works like that where ultimate overboost is hard set and the tolerance can be followed to the set point. Your at such low boost do you need the tolerance setup?

[NigeT]

I know that the Boost was limited because I'm running a standard engine (pistons, rods etc) which requires torque and power limiting, and that the higher boost targets were set to achieve but not exceed that limit, so maybe 200kPa limit at 3500rpm would be too much, but at 6500rpm it is safe.
I guess it depends how the tolerance works, but it does seem like a target relative over boost trigger, from what I've seen in logs (and experience on the road when the car seems to just stop, usually mid overtake).

[NigeT]

I am now pretty happy that my Boost Duty Bias table is pretty good for the targets I am using.

Can anyone recommend a good starting point for Basic Mode Boost Control settings?

I currently have Boost Control Lower Limit set to 50 - can this be lowered a bit? Is there a good starting point for the Close Loop Sensitivity for Basic Mode? I ran with it around 100 this evening.

I can't attach a log - they are way too big to upload and MLV seems to have developed the feature of hanging when loading a log requiring task manager to kill the JVM.

[NigeT]

I upped Basic Mode Closed Loop Sensitivity to 200, but it immediately triggered overboost cut (20kPa above target) - this is still with a 50kPa delta.

So I then went to 150. It seems now to mostly get near the target (100 didn't really, and certainly drooped as rpm increased) without overboosting. How does this look to you guys? Would it be worth reducing the delta?

Many thanks.