BM3 Stage 2 is smoother on F83 with stock downpipes?

[TPNml]

Just out of curiosity, I flashed the BM3 Stage 2 (multimap) tune onto my F83 with stock downpipes and DCT for a little bit.

For some reason, throttle tip-in at <30% throttle is much smoother with Stage 2 than it is with Stage 1. The clutch seems to engage more smoothly and the car takes off from stops/low-speed rolls much smoother than on Stage 1. There also seems to be slightly less boost oscillation in the 3-4krpm range (which oscillated up to 1psi with Stage 1, which my tuner told me to not worry about). The above is true of the map even when the map is on a setting where maximum boost target is set to 0psi. (Yes, I flashed back and forth between the maps and it still feels this way a day later).

I have several questions:

1. Do you guys have any idea what would be causing this on the map?
2. Is it possible to "convert" a Stage 2 map to a Stage 1 map by limiting the maximum boost to, say, 21psi in BM3 (without requiring a complete custom tune)?
3. What is different (other than higher boost targets and the respective heat generated by extra boost) which makes Stage 2 "unsafe" to run on stock downpipes when Stage 1 is "safe"? And how do tuners such as F80Paul or Cary Jordan work around these limitations when customers request a custom tune running stock downpipes?

If I can find a way to make Stage 2 as safe as Stage 1 (including disabling pops and bangs), I think I will run Stage 2 from now on instead of Stage 1. I do not intend to track the car on Stage 2 (I may track the car, but if I do, it will be on stock/Stage 1 map, or I will get downpipes first).

[n8dgr84]

There was no distinction in boost targeting - I believe it is probably more related to timing and VANOS parameters. You can create a larger intake-exhaust overlap without cats as that will damage them.

[TPNml]

To be specific, the extra timing advance can damage the cats after repeated WOT runs due to overtemperature (which causes melting and damage to the catalyst and can result in the exhaust getting clogged), right?

[n8dgr84]

unburnt fuel that burns in the cats

[DaddyMotown]

Are there any examples of such reported issues. A lot of people, myself included, haven’t had any issues with bm3 stage 2 on stock DP.

[n8dgr84]

An OTS tune will likely not have VANOS adjustments (which could reduce lives of cats) but you can check it against Stage 1 in the Advanced channels if you're curious.

My awesome new BM3 tuner, Ata, at Tier1Tuning, advised me that is what they do on catless Stage 2+. He also eliminated a boost spike, smoothed out the power delivery and safely lowered my HPFP to save the stock injectors on my E60 flexfuel tune that F80Paul had maxed out and running a little too lean for my liking. Reach out to him if you have any questions.

[Ata_T1T]

Originally Posted by n8dgr84

An OTS tune will likely not have VANOS adjustments (which could reduce lives of cats) but you can check it against Stage 1 in the Advanced channels if you're curious.

My awesome new BM3 tuner, Ata, at Tier1Tuning, advised me that is what they do on catless Stage 2+. He also eliminated a boost spike, smoothed out the power delivery and safely lowered my HPFP to save the stock injectors on my E60 flexfuel tune that F80Paul had maxed out and running a little too lean for my liking. Reach out to him if you have any questions.

Hi, I'm Ata from Tier1Tuning.

This is correct, as far as I am aware, the OTS tunes utilize the stock VANOS tables. With my revisions to my clients cars, I have noticed that if the VANOS tables are not adjusted with limiters raised, often times you notice a "power hump" during low/mid throttle when going through the rev range slowly. Is this what you are experiencing? Also does this happen in all drive modes or just specifically sport and sport+?

I've been able to mitigate this with my clients with my VANOS + Pedal mapping calibrations.

If you have any questions, please feel free to reach out and I'd be happy to assist. We do our best on every single tune to optimize all parameter's, from fueling pressure to VANOS to timing and drivability.


But to answer your intitial questions:

Do you guys have any idea what would be causing this on the map? Could be vanos, pedal mapping or boost request offsets. I'd be able to tell you more with a log.


Is it possible to "convert" a Stage 2 map to a Stage 1 map by limiting the maximum boost to, say, 21psi in BM3 (without requiring a complete custom tune)? - You may be able to change the "boost limit" in the map config, but I dont guarantee this will work.

What is different (other than higher boost targets and the respective heat generated by extra boost) which makes Stage 2 "unsafe" to run on stock downpipes when Stage 1 is "safe"? And how do tuners such as F80Paul or Cary Jordan work around these limitations when customers request a custom tune running stock downpipes?

- This one is a bit more difficult to answer. Its all about compromise and balance with this one, its not a one size fits all answers, but typically the aim is to keep the EGT's from sky rocketing through the roof. This is done by a compromise of running a richer mixture for engine safety (but potentially not good for the cats as unburnt fuel is not good), but also considering how lean it should be for the cats to not get destroyed (but also not to glow red due to excessively high EGT).


But as a rule of thumb:

The leaner the mixture the hotter the exhaust.....the richer the cooler it is..

That being said, running too rich, will plug your cat with deposits...and running too lean could burn it right out as well as other things

But there are other factors to consider, such as the amount of ignition timing that is being used. If ignition is not advanced optimally, what happens is your mixture is ignited in a way where the exhaust valve is opening/open and some of this heat that is designed for the combustion chamber, gets put onto the poor cats.

Keep in mind burbles and such are also not the greatest for cats. A lot of people run very aggressive burbles with a higher powered tune. Many people tend to disagree that burbles are bad for your cats, but in principal, its explosions inside ur turbo and DP.. so with that information, its a conclusion that one can reach on their own.

I hope that helps a bit.

[TPNml]

Thanks so much for the good information, everyone! The theory behind stage 1 vs stage 2 tunes makes a lot more sense to me now.

What I am experiencing is that throttle tip-in on stage 2 is unexplainably smoother than on stage 1 (specifically at low to mid throttle/RPM on clutch engagement). It's like the throttle is being fed in more progressively or something. Stage 1 kind of feels like a go-kart with a centrifugal clutch (slightly) while stage 2 feels a little more like a PDK or a torque converter auto even.

I just got back from running WOT datalogs on OTS stage 1 vs stage 2 (both 93 octane). The stage 2 tune has higher WGDC compared to stage 1 (roughly 88% vs 84%) and causes the DME to pull more timing (average of 2-2.5 deg per cylinder correction on stage 2 vs 0-1 deg per cylinder on stage 1). As such, I will probably not run stage 2 long term to avoid damaging the car.

Stage 2 log: https://www.bootmod3.net/log?id=6539...0ff15afe4f1b4e
Stage 1 log: https://www.bootmod3.net/log?id=6539...21e165fab0fa3e

What I am also interested in comparing is stage 2 ACN91 vs stage 1 93 wrt timing. I will run more data logs to test.

[n8dgr84]

Originally Posted by TPNml

Thanks so much for the good information, everyone! The theory behind stage 1 vs stage 2 tunes makes a lot more sense to me now.

What I am experiencing is that throttle tip-in on stage 2 is unexplainably smoother than on stage 1 (specifically at low to mid throttle/RPM on clutch engagement). It's like the throttle is being fed in more progressively or something. Stage 1 kind of feels like a go-kart with a centrifugal clutch (slightly) while stage 2 feels a little more like a PDK or a torque converter auto even.

I just got back from running WOT datalogs on OTS stage 1 vs stage 2 (both 93 octane). The stage 2 tune has higher WGDC compared to stage 1 (roughly 88% vs 84%) and causes the DME to pull more timing (average of 2-2.5 deg per cylinder correction on stage 2 vs 0-1 deg per cylinder on stage 1). As such, I will probably not run stage 2 long term to avoid damaging the car.

Stage 2 log: https://www.bootmod3.net/log?id=6539...0ff15afe4f1b4e
Stage 1 log: https://www.bootmod3.net/log?id=6539...21e165fab0fa3e

What I am also interested in comparing is stage 2 ACN91 vs stage 1 93 wrt timing. I will run more data logs to test.

A typical log is done in Sport+ (for cooling) and with DSC OFF in 3-4th gear starting from 3500-6500rpm. A quick stab to 5000rpm wont tell you much, but Stage 2 is not suitable, as you've indicated. If you have access to ethanol, add 3 gallons to a tank and you'll see a big difference.

[Ata_T1T]

Originally Posted by TPNml

Thanks so much for the good information, everyone! The theory behind stage 1 vs stage 2 tunes makes a lot more sense to me now.

What I am experiencing is that throttle tip-in on stage 2 is unexplainably smoother than on stage 1 (specifically at low to mid throttle/RPM on clutch engagement). It's like the throttle is being fed in more progressively or something. Stage 1 kind of feels like a go-kart with a centrifugal clutch (slightly) while stage 2 feels a little more like a PDK or a torque converter auto even.

I just got back from running WOT datalogs on OTS stage 1 vs stage 2 (both 93 octane). The stage 2 tune has higher WGDC compared to stage 1 (roughly 88% vs 84%) and causes the DME to pull more timing (average of 2-2.5 deg per cylinder correction on stage 2 vs 0-1 deg per cylinder on stage 1). As such, I will probably not run stage 2 long term to avoid damaging the car.

Stage 2 log: https://www.bootmod3.net/log?id=6539...0ff15afe4f1b4e
Stage 1 log: https://www.bootmod3.net/log?id=6539...21e165fab0fa3e

What I am also interested in comparing is stage 2 ACN91 vs stage 1 93 wrt timing. I will run more data logs to test.

OTS is in my opinion too aggressive with the timing. It uses the same strategy as BMW, which is riding the knock sensors. I argue that while this is suitable for a stock car, when tuning its best to find a sweet spot with timing for your local fuel and leave it there.

If you would like a custom tune (AKA stage 1.5) thats safe for your local fueling, reach out to me and I'd be happy to assist. My pricing is also very fair.