unisettings ch12 nube question

[sambb]

I'm going to have a crack at capping my overboost (it'll flick up to 25psi without MBC intervention) with unisettings. I've been pointed in the direction of unisettings ch12 but just can't get my head around how this will work. What worries me is that the guides seem to talk about fuel limitation on this channel and I can't understand how this relates to boost.
I've waded through some pretty confusing forums trying to find an answer and the best I could find is that by limiting peak fuel, the ecu will limit peak boost accordingly. Is that correct?
I'd need to go down as low as 80-85% in the scaling to get my boost to 20-21psi if the scaling is infact linear like that. Thats a big change which worries me. Don't want to lean out at the top and grenade my engine so any help appreciated.

thanks
sam

[h100vw]

I'm going to have a crack at capping my overboost (it'll flick up to 25psi without MBC intervention) with unisettings. I've been pointed in the direction of unisettings ch12 but just can't get my head around how this will work. What worries me is that the guides seem to talk about fuel limitation on this channel and I can't understand how this relates to boost.
I've waded through some pretty confusing forums trying to find an answer and the best I could find is that by limiting peak fuel, the ecu will limit peak boost accordingly. Is that correct?
I'd need to go down as low as 80-85% in the scaling to get my boost to 20-21psi if the scaling is infact linear like that. Thats a big change which worries me. Don't want to lean out at the top and grenade my engine so any help appreciated.

thanks
sam

Just drop the boost to 80% and the fuelling should be ok. Just not sure how it affects the rest of the boost curve.

It won't end up all over the street. You can log the fuel to check it. One run wont' kill it.

gavin

[seangti]

Have you checked to ensure that vacuum line from N75 is connected to the wastegate actuator? Or isn't cracked? That's some big boost.

[sambb]

No it's all mechanically ok. Essentially its happening because I have a 3in dump yet still run phase 1. The n75 is simply unable to catch the boost spike in time. Software doesn't exactly match the hardware. I new it was going to happen when I got the exhaust done and even had the boost capping hardware installed ready to adjust on the first drive. It's only gone that high twice - first drive under very controlled circumstances, and when my actuator hose split about 3 months ago. It's a non issue really. Boost is bolted to 20psi and timing is safe and mixtures at 12 and a bit on a 3rd gear pull. Itd just be neater to only have a solenoid again that's all.

[sambb]

For anyone whose interested, I adjusted Ch12 to bring down my peak boost.
I first closed off my N75 bypass to get the engine into a state where it COULD overboost again, and then set ch12 to 85%. This definitely dropped the boost down (12-15psi) so was a good starting point. Then I kept bringing it up until my boost peaks were 20psi in 3rd on the N75 alone. The problem with that though was that the boost in lower gears was a lot lower and the peak boost in third was too sensitive to load. Also the traction/ESP must use the N75 because suddenly there was lots of intervention on corner exit and throwing it through turns that I hadn't seen so much of before.
I ended up setting ch12 to 90% which had it going to 22psi in 3rd (was a 5 degree night so all safe) and then reintroduced a touch of pressure relief bypass to the N75 to clip boost back down to 20psi. That way I know I still have a strong ramp up and body to the boost, I have a safe guard in case the adaptation channels default for some reason, plus the lower gears are holding stronger boost.
Logged it this morning and have the same peak MAF g/s as before so I havent gone backwards. VCDS showed no timing pull. I'll check the AFR's with a sensor up its bum and if thats all good I'll start adding timing.
Anyone know how long it takes for the trims etc to adapt after a change to a channel like this?

[sambb]

Any thoughts on this. With ch 12 scaling on 100% and using quite a bit of Mbc to keep boost at 20psi, I would see very slight timing pull at the start of the boost ramp. With ch 12 at 90% and using only a touch of Mbc I found slight timing pull only at high rpm on third gear pulls eg between 5-6k rpm.
I figured that in the first instance that the boost curve was too full on down low. I'm thinking though that the high rpm timing pull could only be due to fuelling if the peak boost is the same and it was actually tapering off more than before. Any thoughts?
so I split the difference and am running 94% on ch 12 and have no timing pull low or high, but now have slight throttle cut happening. In a third gear pull the throttle plate angle will pull back to 97% at least three times during the run and can be really be felt too. Feels like a slight miss but isn't. What can cause throttle cut, but not timing pull?bhave I not let it have enough time to adapt fuel trims?
my mixtures on ch 12 @ 100% were always in the 12's.
any ideas or leads appreciated

[seangti]

Hi Sam,
Mate, get your hands on ME7 Logger from 403 Forbidden. You only need the logger, not the flasher at the moment (flasher is for uploading tunes). It provides a huge amount of data logging through OBD, 20 samples per second x 60 items. PM Gavin or I if you want to know more specifics, or we can discuss in a thread, Gavin introduced me to it and it's so much more powerful to log than VCDS. I can probably even email you the zip file, so all you need to do is unzip and start logging. VCDS just doesn't have the sampling rate for precise tweaking. You'll get perhaps 12-15 samples in a 3rd gear pull in VCDS, as opposed to a few hundred on ME7 Logger, plus you get the 60 columns of data as opposed to 9. PM me your email address and I can send you a sample of my logs.

Re fuel trims, they seem to settle after about 10-15mins, First block (Add) usually a few minutes, Multi obviously more and needs driving. VCDS has plenty of info on their site and youtube videos. I'm assuming you're resetting the trims and clearing any faults each time you fiddle with this stuff? Are you also checking the readiness section that it's all "Passed". I believe that will affect the timing too. If you can add a screen print of blocks 032 and 033 after 15mins of driving I'd be interested to see.

I've just retuned my red car so have been learning a lot of the fueling, boost, wastegate duty cycle stuff, though am very green on the timing side of things.

[sambb]

Thanks for that mate. I'll definitely look into the me7 logger. I've got another kkl cable on the way since mine hasn't been working on all the groups with vcds, so it might be the right time to get involved with me7.
ive been making the ch 12 sel scaling changes through lemmiwinks. Do I reset my fuel trims prior to testing in lemmiwinks or with vcds lite - hadn't been doing that. I've not run any timing advance offset at this stage. The above is all on phase 1 base timing. Didn't want to have another variable in play at the same time as boost (fuel) changes.
thanks

[seangti]

Do I reset my fuel trims prior to testing in lemmiwinks or with vcds lite - hadn't been doing that.
thanks

I had been doing it in vcds. When I was loading a new tune it would reset to zero automatically anyway. It was on the VCDS site that I saw the process to reset fuel trims and why you'd do that - their youtube video is very good too. I'm not sure what kind of memory is in the ECU, if it's constantly variable over say a 10min period for example, or much longer duration which would than "absorb" poor readings.

But as I'm learning, there are so many more variables that effect performance than just boost or fuel trims alone. Do you know your waste gate duty cycle? At 20psi, it'd have to be nearing it's limit I'd thought.

[sambb]

Ok I'll look into the fuel trim reset stuff. No I dont know my duty cycle. As I said I think it's my cable that's limiting me. Logging group 31, 32, 099, 111 and 115 hasn't been possible so I haven't been able to see the fuel trims and requested boost vs actual boost. I'll have to read up on what it is that causes throttle cut alone, but not timing pull too.