02-08-2024, 10:36 PM | #1 |
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Air Fuel Ratios never dip below 13.8!!
So, I've built many turbo Hondas and Nissans over the years, but this is my first BMW...
My question comes from basic tuning concepts, though, regarding AFRs (air fuel ratios) of the OTS maps in BM3. I have seen kern417's thread of what he was getting for basic AFRs across several of the maps (this was a rather old thread, but the info should still be relatively valid). Basic tuning concepts have dictated that AFRs for boost float around 12.2-12.4:1... which gives optimal power and maintains good safe cylinder temps. Wwweeeellll... enter my BMW. I installed several of my parts on at the same time. VRSF catless downpipe, B58TU HPFP and BM3, a week or so ago, and tonight I put my RKTunes front mount CAI. I put a Stage 2+ E30 tune (With the HPFP set to OEM), and it pulls really hard... so much so, my stock clutch can't hold the power even in Comfort Mode. During these little pulls, I was datalogging a bit, just to see how "safe" this tune was, and was SHOCKED to see the AFRs are are at 14.4-14.9:1!!!!! I freaked out and got off the gas thinking my engine was going to explode! So I started bringing the tune down, Stage 1 E30.. same AFRs, even reinstalled the completely STOCK rom and the AFRs only dropped to 13.8:1!! I checked a few things in the logs, timing correction never got more than -4 degs, and there was only one triggering of the knock sensor, very low in the RPM... Here are some links to the logs.. Stage 2+ E30 https://www.bootmod3.net/log?id=65c5...040d6609f38c36 Stage 1 E30 https://www.bootmod3.net/log?id=65c5...f7fd189d78330f Stock Tune https://www.bootmod3.net/log?id=65c5...dbeb79e12a6ea8 So my question is am I missing something important in these logs that is telling me why my AFRs are not where they should be? ...or is this a new "normal" for boosted cars that I haven't heard of? ...could there be a hardware issue, bad O2s? Something...? Any help would be greatly appreciated... |
02-11-2024, 08:52 PM | #2 |
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That was kind a waste of my time, and those logs are gibberish with all those values selected. First log your at less than 50% throttle, of course your not going to be at wide open fueling/timing. Second log, your at a total range of like 3000-3500 lugging the motor for some reason. Do like a proper 4th gear pull, with a log at wide open and then return with that so i have something to look at. Also dont select all the values being on at once.
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02-11-2024, 11:02 PM | #3 |
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Well, I apologize that you feel I wasted your time... But I will address what you said..
I'm not going to do a full throttle pull at 22psi. A decent base map (which is all these OTS essentially are) should have a smooth fuel curve through the entire rpm/pressure range. Only tuning WOT would be, for lack of a better term, stupid. So, I should still be getting 12.2-12.4:1 AFRs while at full boost, no matter the throttle percent. And doing a full throttle pull with those AFRs is a clear way to exploding your ring lands... Sooooo no thanks. Second, unless you see a different screen than I do when I click that link (which very well could be) you can deselect all the channels, and choose which channels you'd like to view. ...at any rate, I appreciate your insight, however, before I risk my ring lands, I am going to drive this tank of gas out completely, change to an E10 91oct map and see what that looks like. Due to the fact that 3 vastly different tunes gave the mainly the same results, it makes me feel this company's E30 is suspect. I think I am also going to change my plugs and coils as the car has 86K I have no idea when/if the previous owner ever replaced them. From there, I will start pushing deeper into the throttle. |
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02-12-2024, 04:31 AM | #4 | |
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Put a pump map with 91/acn and go from there as the post earlier suggested |
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02-12-2024, 09:27 AM | #5 | |
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02-12-2024, 08:54 PM | #6 |
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These are basically OTS maps. These are not my own made maps. As a custom tuner I would run them a little more rich but like everyone else said if you don't go full throttle you can see the car will not add more fueling.
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02-12-2024, 09:29 PM | #7 |
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Hmmm I am hoping that people don't assume that a lack of posts is a lack of experience...
I don't have experience with BMWs, no, that is where the assistance is really needed. As far as tuning, it's been a while since I have been in the scene (just getting back in with this car) but I come from Honda/Acura tuning, having authored TurboEDIT (A Hondata alternative) and having been a lead developer of PGMFI.org's custom ECU ROM. And I can't tell if this is a "newb hazing" or what... But telling someone to run full throttle boost pulls on AFRs higher than 12.5:1 is wreckless. WRX seems to know this, as you start rich and lean out to make power. "Leaner is meaner" only works until your ring lands explode. I'll make cleaner logs, fine... But full throttle pulls aren't coming until I can isolate the reason why less aggressive maps (more fuel less timing) aren't changing my AFRs. With my TU HPFP, I would assume, a stock ROM would run rich given given the pumps increased flow, clearly this wasn't the case. This is where I was hoping I could get some insight... More along the idea of what the DME is doing. I.E... is the regulator being controlled by the DME, and thus fluctuating the pressure values causing the flow rates to be augmented by pressure and not pulse width to reach some target efficiency value? Previous experience has the ECU extrapolating from the fuel tables and using algorithms that take into account various sensors. Now newer cars have more sensors, therefore more trims.. or adaptations, I guess they're called in BMW jargon... Does anyone know how pulse widths are calculated, because it's clearly not a direct extrapolatation of the maps? There are a lot more sensors than when I was coding back in the day and any help in understanding the process would be a great help. I'm not trying to be obstinant, just trying to adapt years of previous knowledge to technology used today... |
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02-12-2024, 11:12 PM | #8 | ||
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If you don't feel comfortable with the partial throttle data you're seeing, you can always get a custom tune from a reputable tuner.
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02-13-2024, 04:56 PM | #9 |
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They run lean at part throttle.. you're not going to see those 12.2-1 afr numbers anymore. Those days are gone.
Also, unless the car is breaking up or bucking or whatever it's 100% fine. The failsafes in the tuning are so advanced you can practically stay 100% throttle even if it was and nothing will happen. Worst case it'll throw the car into limp mode for safety before you'll ever hurt anything. You'd need to do something crazy for the most part.
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02-13-2024, 10:48 PM | #10 |
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Okay, I will give it a try... As I said it feels great when dig into it on the Stage 2+ E30... Just the AFRs were my concern.
Alright, I finally ran that tank of E30 out and filled with 91 E10. I put the Stage 2 91oct OTS map on it and yep, I want my E30 back!!! Hahah!! This detuned map feels like a sloth compared to the E30. My stock clutch holds this power fine. Anyway, it's running smooth, albeit slow, but no issues so far. I will run the logs sometime tomorrow night. Thank you all for the great information. I look forward to discussing the upcoming logs! |
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02-14-2024, 02:42 AM | #11 |
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I imagine you could have ran the higher octane/E mixture with the lesser tune. You can always error in favor of higher octane mixutre 🤙
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02-14-2024, 04:59 AM | #12 | |
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02-14-2024, 08:16 AM | #13 |
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Yeah, that I did know... However, the station that supplies the E30 is a local chain that, after some online research, has mixed reviews as to their quality, and having less than a half tank, it wasn't that big of a deal.
Now I have known good quality fuel and feel better about troubleshooting potential hardware issues. ...oh, and what really sucks... They're the main supplier of higher ethanol mixes in my area. I will have to do some digging to see if I can find another supplier once everything is dialed and I can trust my hardware again. |
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02-17-2024, 06:35 PM | #14 |
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Keep in mind we are in the world of direct injection and full ECU knock correction.
Fully appreciate your concerns though. 12.0-12.5 used to give you the best bag for the buck. BMW runs almost full power at 14.7 (which technically is the optimal ratio, but in yester-years would have resulted in you punching a hole through a piston!) |
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02-18-2024, 01:12 PM | #15 |
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Well, I apologize for not getting these sooner. Some things came up while I was at the Super Bowl rally in KC (as I am sure you've heard). Anyway...
Here are two pulls from today. Hope these are cleaner for everyone. I removed a few of the channels that were being logged (basically went by kern417's post about logs and suggested channels). Stage 2 91 oct (3rd gear) https://www.bootmod3.net/log?id=65d2...f7375a14155528 Stage 2 91 oct (4th gear) https://www.bootmod3.net/log?id=65d2...f2c967f9aa527f Yeah, this is taking a lot to accept from my dinosaur days, however, these logs seem to be more in line with what I would expect from boosted cars. However, boost falls off 8psi over the rpm band, and when looking at the "Boost target" actual boost is following the target pretty well... Is this normal for this map? BM3 tuners bled off boost as rpm increased or am I misinterpreting this info? Also seems like there is a 2-4deg timing retard to correct ...something? There is no knock, and AFRs look sweet (even for me! ). Any help interpreting these would be great, thanks for putting up with me and this learning curve! This tank is almost empty so I'm going to put some E30 back in, and try that map again... Stay tuned! ———- OK... I'm back with E30 logs. Keep in mind that my clutch can't hold the E30 tune well but this is way better than what I had before. AFRs more in-line with what I'm used to seeing here too... I still am feeling sketch about the part throttle, but you guys have given me a little more confidence about it. Stage 2+ E30 (3rd Gear) https://www.bootmod3.net/log?id=65d2...f7fd189d7dd550 Stage 2+ E30 (4th Gear, little clutch slip at 3300rpm, and 3700rpm) https://www.bootmod3.net/log?id=65d2...f7375a14156014 3rd gear E30 pull is the cleanest.. Looking at boost it fades about 2psi or or as RPMs build, but the difference here is that it deviates from the target boost line line by that 2psi. The big thing I see this time is the timing correction. There is a 7-8 deg timing retard over the rpm band!!! Thinking my plugs or coils... any thoughts? Last edited by sigterm2.0; 02-18-2024 at 07:29 PM.. |
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02-18-2024, 07:22 PM | #16 |
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I hate to throw a wrench in this thread, but this is exactly why I chose MHD. catless, dorch s2 fuel pump, and my timing and boost deviation is on point. Impressively so… I do mix my gas 50/50 91 and e85 for the e40 map, just easier and rather error on the side of MORE octane… but I see these bm3 logs and 🤷‍♂️
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02-18-2024, 07:40 PM | #17 |
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Hmm, I had originally thought I would go with MHD (I even use their red Universal Wireless Adapter in my car with BM3), but I liked the idea of having the map editor and being able to edit my own maps (MHD might have this but I didn't come across it). It seems that MHD is only OTS maps.
Now the irritating thing I am finding that is that with BM3s OTS maps, I can't edit them, they're locked. Meaning I have to start from a stock map and retune to get to the power I am at now, instead of using the OTS as a basemap, and customizing it for my specific application. Not ideal... more cost, more time... But I have been happy with the interfaces, and ease of use of BM3. |
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02-19-2024, 05:46 AM | #18 | |
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Other than that do yourself a favour and run the stock tune and look at AFR. Full power is made at 14.7:1 all the way through. These DI motors from BMW run stoich at full load on PUMP gas. Let alone on ethanol mixes which allow even leaner air fuel ratios. |
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02-19-2024, 05:56 AM | #19 | |
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02-19-2024, 07:41 AM | #20 | |
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02-19-2024, 01:00 PM | #21 |
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That was generally the rule of thumb... Run richer on boosted apps due to the potential for increased cylinder temps. Naturally aspirated were run about 13.1-13.4:1 AFR because they didn't run as hot... The extra fuel helped keep the EGTs in check on boosted applications.
Though, what I am starting to see is that BMW does try to run a stoich, at least at part throttle, even under boost. Direct injection is a great method for fuel distribution... I just didn't realize it could allow for stoich AFRs under boost! That's new to me... Here is a good article I found about direct injection. https://www.consumerreports.org/cro/...050%20percent. I am not opposed to learning new things. I appreciate all the knowledge everyone has been contributing! |
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