M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: bmwman91 on April 20, 2015, 02:12:23 AM
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EDIT: See post #11 for the latest data and findings.
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I finally got my new data logger working and went out to do some quick measurements with it. It is not really intended to be a full engine measurement system, but rather to just measure a few voltage parameters in support of the next-gen MAF conversion I am putting together for the car. Anyway, I figured that I would post up a little bit of information since everyone loves charts and stuff.
First up is a log showing a pull in 2nd gear with the car's current engine (a Metric Mechanic 2.1L M42 with every bell & whistle that MM offers for it along with a couple of extras). Note that the horizontal axis is TIME in milliseconds, not RPM. For the purposes of what I am working on, RPM is not really a factor which is why I am not logging it (I can always add it to the logger in the future). Also note that the green line is AFR which uses the RIGHT vertical axis.
(http://www.e30tuner.com/assist/B21secondgear01.png)
The M42B21 in the above plot is using a 100% stock M42 air box (complete with sort-of-dirty Mahle filter) and VAM. You can see the wild overshoot as I snap onto the throttle and the flapper door bangs open, and then it oscillates a little which causes the AFR to go lean for 100 msec or so. You should also notice that there is not really much of an appreciable lag between when I open the throttle and when the VAM responds, although obviously all accuracy of its output goes straight out the window. I assume that the DME is programmed to account for this though, but I really have no idea there. There also appears to be a fairly significant delay between throttle / VAM signal changes and the AFR responding, maybe indicating that much of the response delay in the system is just due to the DME. Also, the straight horizontal green line is at 14.7 AFR just as a reference for stoichiometric.
Next up is a fun one. I converted the air flow units to CFM since that is probably what folks on here are more familiar with. The orange line is the same one as above (but in CFM instead of CMH). The blue line is from 2007 and the car's original M42B18. Also of note is that the blue line's output came from a MAF sensor, and since I knew the air temperature I could convert the output to CFM from kg/hr. Now, this comparison is subject to whatever inaccuracy is present in both the MAF I used in 2007 and the 20-something year old VAM in my car now. I'd say that the orange VAM signal might be plus/minus 5% accurate and the blue MAF signal is probably pretty dead-on. The logger I built back in 2007 was rudimentary, to put things nicely, compared to what I am using now. Signal accuracy is probably fine though, so this should be a fair-enough comparison.
(http://www.e30tuner.com/assist/B18B21_AFComp01.png)
There are 4 fun things to note here:
1) Cray-cray (that's a technical term, right?) overshoot of the stock VAM when the throttle opens up. The blue line, again, was from a MAF and it keeps its wits about it a lot better since there is no door flapping around all willy-nilly.
2) The peak you see is (I suspect) due to the MM "Pulse Chamber" intake manifold which they say was designed to boost mid-range torque. Clearly it does what it is advertised to, assuming I am guessing right. The green circle for #2 covers ~2000RPM to ~3500RPM, which makes sense given how well this engine behaves at lower RPMs around town. [COLOR="Red"]EDIT:[/COLOR][/B] This is NOT due to the MM pulse chamber manifold. It is most likely some behavior of the VAM when intake resonances are really bad which make the flapper door open more than it would with steady air flow.
3) The 2.1L engine maxes out the VAM. Output is capped at 240CFM, which is actually in nearly perfect agreement with the Bosch datasheet for the M42's VAM. The first plot shows that the AFR stays good even when the sensor is output is clipped, so the DME doesn't seem to mine the maxed-out VAM since it is working off of custom fuel maps for this engine. I do assume that the VAM is restricting air flow at least little bit in this case though since I am moving enough air through it to peg it at its limit.
4) I "scrunched" the time axis for the blue line for the stock M42. Obviously it took the stock engine longer (about 1 second) to rev all the way up to 7200RPM and I scaled its time axis to align with the MM engine plot for a better comparison.
Another observation is that it is obvious that the stock M42 (blue line) stops breathing as you get into the high-end of the RPM range (it starts flattening at the equivalent of ~5500RPM). The MM M42 looks like it might want to start running of out of breath at the same range, but then it picks back up at ~6000RPM and just keeps going from there. The redline is set at 7700RPM in the DME software, and I can tell you that it pulls nice and hard all the way up to 7700RPM. Apparently I need a bigger air flow meter lol (and I will have a MAF in there soon enough).
I have other plots for idle, part-throttle cruising, stop & go, etc if people are interested. I just thought that this was interesting stuff that I could share from this project.
The logger itself is a side project of mine. It measures each signal 30,000 times a second, hits them with some digital filters, then downsamples to 10,000Hz and sends the data to the PC (so I have 0.1 msec time resolution). There are also some 4th order anti-aliasing filters on each channel to keep RF noise out and that sort of thing. One thing I did find today was that ignition noise is present in all of the analog signals coming from the stock sensors. That is not really much of a surprise, and it isn't a big deal since the DME seems to be fine with working around it. You cannot see it in the plots as they are scaled here, but the idle plot definitely shows "blips" on a very regular period in the VAM, IAT and TPS signals, probably because they are resistive sensors and EMI + high impedance lines means noise spikes.
Funnily enough, my little logger project is more complex than the MAF converter I am now working on. I guess it is like anything...you spend more time prepping and building tools/fixtures than actually doing whatever it is you are doing.
(http://www.e30tuner.com/assist/fd33e01.jpg)
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Hi bmwman
Graph 1
First a question, is this at wide open throttle?
Because it looks like the afm oscillation is in the afr ratio.
Also to note is the trough between 2000 and 3000 in the AFP ratio. I wonder what is causing that?
Pulse chamber or dme programme.
Graph 2
It is interesting to see the oscillation of the door, I did not believe it would be that bad!
Also that pulse camber of yours, I would not mind seeing a standard inlet manifold on your data logger just to eliminate that variable or compare. Be cool to see an trumpet set up too at various lengths.
Your afm certainly stops you cold. The difference between the engines is quite startling with regards to air flow and that's an adjusted curve, compressed with regards to time.
Cheers Rohan
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Graph 1
- Yes, the plots are with the throttle open 100%.
- The AFR does oscillate as a result of the AFM door flapping around. The dip and second small spike in AFM value after the first big spike are basically sensor error. The "real" air flow into the engine is probably more constant looking, but the DME sees the air flow voltage drop so it cuts fuel momentarily, which is why the AFR goes lean briefly. A MAF would completely eliminate this.
- Yes, the engine is running rich over a wide range. This engine came with a new chip that was tuned for it (not this specific engine, but MM has a generic tune for their 2.1L M42). I did have to switch injectors, and while they are rated at the same bulk flow rate as the ones MM originally specified, maybe they are dumping too much fuel? Either that or it is just due to the tune itself because this engine wants to run a little rich.
Graph 2
- It was also a bit of a surprise to me as well. Honestly, I expected to see a bigger delay between throttle movement and AFM response, with no major oscillation. It looks like there is ~40ms of delay between throttle movement and AFM response, but it definitely has some bad characteristics when you make quick throttle changes.
- I would also like to toss a stock M42 intake manifold on there to see how it compares. The circled #2 area definitely resembles a resonance characteristic, so I am pretty sure it is from the PC manifold. I'll see if some of the local M42 folks I know want to let me borrow one.
- Yes, big difference between the two. I am glad that there is such a big improvement...it means I got what I paid for lol.
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Graph 1
I'm surprised that this was wide open throatle, I thought that at wot and only at wot the afm did not have any influence?
As for running a bit rich perhaps the aftermarket oxygen sensor but you are probably right it would be the tune, MM would be silly to run lean. Or even close too!
I keep looking at the oscillation with the afm and afr, I never thought it would be that bad!
That's all over the place like a brides nighty. ::)
Graph 2
It's also interesting that the m42b18 afm does not oscillate any where near as much as the m42b21 perhaps because the afm is at nearing full capacity on the m42b21.
And how much did you compress the m42b18 with regards to time, roughly?
You could borrow my intake manifold, but postage would kill us as I'm in oz!
Yes I would say you got what what you paid for it looks like there is a 30% increase in air and that does not take into account the time compression!
Any thoughts on why there is oscillation from 4s and above? I'm thinking a cramped cylinder or cylinders with regards to exhaust or inlet manifold.
Very nice!! ;D
Cheers Rohan
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At WOT, the AFM is still used. It is the O2 sensor that gets ignored at WOT (and above a certain RPM too I think). The DME works in closed-loop mode when the O2 sensor is being used because the O2 sensor closes the feedback loop for the fuel injection calculation (in addition to RPM and AFM input). At WOT, the stock O2 is too slow so the DME ignores it and only uses AFM input and RPM to look up fuel injection values.
I figure it is the tune since the Wide-Band O2 sensor setup I have is finally working properly.
Yeah, there is some pretty big overshoot and oscillation. Functionally, it is probably not all that big of a deal since it only lasts ~250ms. Still, it can be better with a MAF.
The plot for the M42B18 was taken from a MAF, not an AFM as noted in my original post. That is the reason for the lack of overshoot...the B18 had a MAF and the B21 has the stock AFM.
The smaller oscillations are probably just due to hitting various cavity resonances in the intake or something to that effect causing the AFM door to deviate a little. The blue plot looks similar, despite being taken from a MAF. However, I am thinking that much of that might just be measurement error/noise because my electronics skills were nothing in 2007 compared to now, and the logger that I built back then was terrible lol. It was fine for overall accuracy, but a lot of ignition noise got in and was not well handled.
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My apologies your absolutely right about the O2 and afm!
It would definitely be the tune, can you imagine someone getting a mm motor then bad fuel!
Running a bit rich would be safe and no one would normally pick it either.
Any reason you didn't keep the maf conversion going on the mm motor? Warranty perhaps.
The small oscillations are from resonance effects, but would a maf solve this?
I'd say your getting about 30% more air with the new motor add to that the increase in compression, any wonder your getting nearly twice the power now! 8)
Cheers Rohan
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I had the MAF on the MM engine at first, but the car did not run well with it. I later found out that it was due to failing valve springs and a vacuum leak that I caused. So I put the AFM back on. A couple of months later when all of the issues got sorted out I just left the AFM in there since it was running well and I was completely burned-out on the car and trying to do anything with it. MM took care of the valve spring issues for me at no charge and it was not really even their fault that there were issues (their spring supplier started having quality issues).
Anyway, I have had time to mess with other electronics projects since then and I have discovered some improvements that I can make to the MAF converter. I am working on that now and hope to be running on a MAF again in a couple of months!
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So that's why your not using maf and m30 airbox.
Yes that would have been annoying, to say the least.
Trying to figure what was wrong because it couldn't be the new motor.
So I'd be guessing you would have changed quite a few things finding the fault.
Maybe try this on maf and and m30 airbox.
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Yeah when I had the new motor I figured that the issues had to be with the MAF converter. Much to my disappointment it was a failing valve spring (which completely broke shortly thereafter). A second one broke a few months later, and MM once again covered all costs to make everything right for me. Still, by the time that was done I was completely burned-out on car projects and had zero interest in tinkering for about a year. The broken valve springs were also around the same time that I got married and bought a house...luckily I married a very patient girl!
Anyway, my next step will be to use the MAF and modified M30 air box that I put so much work into. I just need to work out the new MAF converter firmware and design some updated PCBs.
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Great to hear that your still doing this!
I look forward to seeing it!
Post all 3 up when you have it done, it would be a very interesting comparison!
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It's always really cool when we get to see somebody investing time and brainpower in our old M42s. Very nice work!
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OK M42 fans, I finally have decent data for comparing the stock VAM and a MAF on the 2.1L MM engine. The VAM uses a stock M42 air box with a 1 year old Mahle paper filter, and the MAF uses a modified M30 air box with a fairly new Mahle paper filter (60% more surface area than the M42 filter).
Here is the quick and dirty summation of my findings: Using a MAF doesn't gain you anything on the M42, even with a strung-out 2.1L.
Surprising? Not really. Disappointing? A little. BMW really knows what they are doing (and yet we are constantly second-guessing their design choices!), and the stock M42 air box & VAM are just not restricting anything based on the data I am seeing. The filter element in the M42 has the same surface area as the M20 and S14, so obviously it is good for ~200bhp, at least. As for the VAM, I was expecting it to be at least a little restrictive at higher RPMs on my 2.1L beast, but so far that just does not seem to be the case.
We can all rest, assured that BMW made a very good air box & VAM sensor setup for the M42 when they designed this engine. So, that much is a big plus. The obvious downside is that it is a big nail in the coffin for the idea that there is more power to be gained from a MAF conversion. Sorry folks, it looks like the only areas where the M42 got handicapped are the stock software tune, and the conservative stock cams (and do note that hotter cams will not do anything good for your fuel economy, so even the stock ones have their purpose). The stock cams aren't really a handicap anyway since they traded power for fuel economy, so basically it's just the stock software that sucks. BMW really knew what they were doing in designing this engine (duh), except for the horrifically over-complicated and unreliable timing case setup lol. My MAF conversion adventure has been about a decade long, and I can now finally say that I have reached a conclusion, not necessarily the one I wanted, but at least I know what the deal is now.
So, here are air flow and AFR readings taken during 2nd gear WOT pulls.
(http://www.e30tuner.com/assist/b21secondgear_vdoto2_vamvsmaf.png)
There is an important fact to keep in mind here. The air flow values are from 2 different sensors. Air flow values are calculated as a function of the output voltage from the sensors, so the accuracy of the air flow values is subject to whatever tolerance deviations are present in these individual sensors. For example, an "ideal" M42 VAM sensor might have this as its transfer function: Air Flow = (5 x Voltage) + 30, so my logger reads the voltage and calculates air flow based on that. This actual sensor might have a transfer function like: Air Flow = (5.176 x Voltage) + 28.97, so obviously my calculated air flow value will not be entirely accurate. Neither the VAM or MAF that I am using have been put on a flow bench to measure their actual transfer functions...I am going based on Bosch data for "ideal" sensors.
You will notice that the AFR differs between the two sensors' WOT pulls. The fact that the MAF pull is ~5% leaner over most of the pull could indicate that the MAF is under-reporting flow, or that the VAM is over-reporting flow to the ECU. Or, it could be due to the "lumpier" MAF converter signal (the plot above has had some pretty heavy smoothing applied so it is easier to interpret visually) causing a little bit of confusion in the ECU, which I have seen cause lean conditions in the past. I find it unlikely that the MAF setup is actually flowing more air since the next plot of RPM vs time indicates NO performance difference between the two sensors. If you are also thinking, "damn, those are some rich AFR numbers for an NA engine" then I am right there with you. I need to find a local dyno shop that can work with the M1.7ECU to get things better dialed in. Either that, or MM did it on purpose so I could use 91 octane with their 11.5:1 compression build.
This next plot shows engine RPM vs time for four 2nd gear WOT pulls, two with each sensor. I unplugged the Motronic to reset it before doing the MAF pulls, and then unplugged it again to reset it after swapping the stock VAM setup in. This was to try to minimize any LTFT (long-term fuel trim) adaptations, although I don't know if those even effect the WOT maps. The runs were done on the same stretch of road within 40 minutes of each other. The <0.2 second variation between runs is probably just margin-of-error due to the driver (me) and slight road variations. VAM and MAF lines are all mixed in with no obvious difference.
(http://www.e30tuner.com/assist/b21secondgear_time_vamvsmaf.png)
Just for everyone's info, here is what a 2nd gear WOT pull looks like with a MAF. I think that it should be fairly self-explanatory why you cannot just hook a MAF up to the ECU. Throttle was 100% open, so don't worry about the fact that the log shows ~95%, it's just a calibration issue. The fuzzy yellow line is what comes out of the MAF sensor, and the blue line is my converter's output which mimics the VAM's output and goes to the ECU.
(http://www.e30tuner.com/assist/b21secondgear_fullmafdata.png)
Here's a zoomed-in view of part of the plot. You can see that the MAF output is showing every intake valve opening once the throttle gets opened up a bit.
(http://www.e30tuner.com/assist/b21secondgear_fullmafdatazoom.png)
As I mentioned in a previous post, I was having issues with the RPM signal. It turns out that the physical installation of the RPM conditioner was just fine. The issues were in my logger's firmware, and I fixed them. Measuring RPM takes a lot more coding than measuring voltages! I cleaned-up the board installation anyway though since it wasn't really ideal to begin with.
(http://www.e30tuner.com/assist/motronicmadness03.jpg)
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Hi bmwman
Graph 1
Why do you loose the benefits of the pulse camber with maf?
It's almost like your using a different inlet manifold.
Looks like that engine is set up for fuel economy, not!
Graph 2
That's dead linear, no pulse chamber in any of them.
Graph 3
I thought the corrected blue line would be more of an average of the actual reading.In the higher rpm range it does nor even touch the maf output.
Amazing you can actually see the changes in air flow with the valve opening and closing.
Nearly went blind reading this on my phone, but great work.
Cheers Rohan
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Hi bmwman
Graph 1
Why do you loose the benefits of the pulse camber with maf?
It's almost like your using a different inlet manifold.
Looks like that engine is set up for fuel economy, not!
Graph 2
That's dead linear, no pulse chamber in any of them.
Graph 3
I thought the corrected blue line would be more of an average of the actual reading.In the higher rpm range it does nor even touch the maf output.
Amazing you can actually see the changes in air flow with the valve opening and closing.
Nearly went blind reading this on my phone, but great work.
Cheers Rohan
Graph 1
I am also interested in why the shape of the air flow curve changes so much. I am swapping the sensors AND air filter boxes here, so the stock M42 air box must be contributing some sort of resonance and/or working with the pulse chamber manifold. Basically, I really need to stick a stock upper manifold on there to see what, exactly, the pulse chamber manifold is doing.
Graph 2
Right. Whatever that "bulge" in air flow is with the stock VAM, it does not seem to make a noticeable change in power output. From a purely subjective point, the car "feels" like it pulls harder in that range with the stock setup.
Graph 3
Good observation. Everything is correct though. The crazy yellow line is MASS air flow (kg / hr), and the blue line is VOLUME air flow (m^3 / hr). They are related by air density, and so there is a scaling factor between them that changes with temperature and pressure.
Whatever the case, I feel like the car is running WAY too rich at WOT. Don't NA engines usually shoot for ~13:1 AFR at WOT? I realize that there is no one-size-fits-all rule for these things, but 11.5:1 and 12:1 seems too rich.
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Hi bmwman
What's your exhaust and valve set up?
Afr for maximum power na engines should be between 12 and 12.5.
Is it possible that the acoustics are coming from back of the afm? There's a fair sized surround on the flipper door.
Cheers Rohan
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I keep looking at your last couple of graphs and get an air density of 1.2. Hmmm
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Hey bmwman, how's your idle quality with those cams? Mine idles plain terribly now that the DME has adapted. It might have even developed a vacuum leak while fiddling with stuff. Your cams are hotter than mine so I was wondering how smooth yours is.
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The idle is fantastic. Smooth and steady. It sounds like you have a vacuum leak.
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My idle is spot on as well at 850-900rpm with no AFM 8)
Cheers,
~Ralph
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Good to know! I'll keep looking. Might need to degree that cam too
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So, I revisited the data that I took this summer and put together another plot. This time I displayed the air flow rates and AFR's from all 4 runs, with RPM as the X-axis. The most obvious thing is that the first run from each sensor is MUCH richer than the second run. Remember that I unplugged/reset the Motronic before swapping sensors, so it was re-learning all of the short- and long-term fuel trim settings. There was ~5 minutes of run-time after reconnecting the Motronic and doing the first pull, and then another 5 minutes after that until the second pull. Since the second pull is leaner, a big factor must be in allowing the Motronic to adjust based on run-time data from the O2 sensor.
OK. Here's the plan. I reinstalled the datalogger hardware this evening. I am to put at least 100 miles on this thing so that the Motronic will (hopefully) be fully adjusted, and then I will log some more 2nd gear pulls with the MAF (which is on there now). I will probably also log the idle and some part-throttle driving just for the sake of completeness. Thereafter, the VAM will get stuffed back in, the Motronic reset and after 100+ miles I will do the same measurements with it. Does anyone here know how many hours of operation it generally takes for the Motronic to establish its long-term fuel trim values?
Here is the plot of data that I mentioned at the start of this post.
(http://www.e30tuner.com/assist/b21secondgear_allcfm_allafr.png)
The green and orange lines are the first runs after resetting the Motronic with the engine at full operating temperature (green is MAF, orange is VAM). Similarly, the blue and yellow lines are the second runs, at which point the Motornic has had 10-15 minutes of operation at full operating temperature (blue is MAF, yellow is VAM).
You will notice that the first runs are much richer than the second ones. My main interest here is the blue and yellow lines below 3500RPM. On these second runs, the MAF runs a lot leaner than the VAM (AFR of 15.0 vs 13.5). This corresponds exactly to the big "bump" in air flow signal coming from the VAM in that range. Someone correct me if I am wrong, but an AFR of 15.0 at WOT is not a recipe for power, and I think that this must be why I "feel the bog" in that range.
I have no reason to believe that the VAM+stock air box is magically flowing that much more air in that range, and as noted in a prior post, I think that it is a resonance effect interacting with the VAM's door which causes an artificially high output voltage from the VAM sensor, which just about any M42 tune will have factored in. Since the MAF accurately reports air flow here, it ends up passing through the tuning tables and leads to leaner running since the table tuned with the assumption that air flow is over-reported in this range. I do seem to recall hearing unverified information over the years that indicates that the Motronic runs off of the 2D maps below 4000RPM regardless of throttle position, which means that it is using the air flow voltage as a primary load signal, and then above 4000RPM if the throttle is open more than 80% it switches to 1D maps for faster response (in which case the air flow signal is largely ignored). From looking at how well the AFR's match above 4000RPM, this seems like it could be the case.
The initial implications here are that there may very well be no way that the M42 can ever have a "perfect" plug-and-play MAF conversion. You would either need a chip with a tune that is not based on a big bump in voltage from 2500-3500RPM, or you would need a MAF converter that taps into the crank position sensor and throttle potentiometer...in which case it really can't be called plug-and-play anymore since you are cutting wires. Maybe I could work an FFT algorithm in to the converter that basically allows the RPM to be read from the pulse frequency of the raw MAF signal, and then a correction curve is applied which mimics the VAM's goofy signal bump from 2500-3500RPM.
Phew. That is a lot of text. At this point, I know one thing for certain. It is time to find a tuner that can work with M1.7 and get a custom tune for this engine with the MAF installed.
For a little bit of extra fun, this link has a ~11,000 pixel wide plot. This one has the raw MAF output signal on it, and it is super duper wide which allows you to see how ugly the signal is. Every single intake valve opening is clearly visible! Remember, in this plot the horizontal axis is in milliseconds, not RPM.
http://www.e30tuner.com/assist/b21secondgear_superwideintakepulses.png (http://www.e30tuner.com/assist/b21secondgear_superwideintakepulses.png)
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Hi bmwman91
First a question, why continue with the maf conversion? Throttle response, tuning?
That peak at 3000 rpm is so lean for the maf, that would be caused from your inlet manifold and the engine getting more air that is not being pulled through the maf. Makes me wonder how the afm compensates for it. Or more correctly sees it at 3000 rpm.
Looks like the afm and maf run better just after they have been reset. Has me baffled with regards to what the maf is doing below 2500 rpm. What size is the maf?
Cheers Rohan
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The MAF OD is 75mm (exact fit into the M42 intake boot).
The issue, as far as I can tell, is that the stock AFM over-reports the air flow in the 2500-3500RPM range. The peak that you see there looks sort of characteristic of a Helmholtz resonance, and that is no surprise because the stock AFM has a big air chamber in it and moving parts. It is very repeatable and is seen every time in that range when the throttle is mostly open. I think that BMW knew this, and tuned the fuel maps accordingly. Basically, the DME is expecting air flow to be reported higher than it actually is in that range due to non-linear behavior of the sensor, and the map bins for that RPM at high load will be operating out of a higher load range than they should be. When the MAF is in there, it is correctly reporting the real air flow, but since the DME is "expecting" a higher load value (higher voltage), it is operating out of lower load bins and running lean. Hopefully that makes sense. In short, the stock sensor is inaccurate in that range in a predictable way, and the DME is tuned for that. The MAF is very accurate in that range, which is in conflict with the fact that the DME is not tuned for an accurate air flow signal in that range.
Why stick with the MAF? No reason, really. Throttle response improved a tiny bit, but it is still very limited by the old DME. A more modern ECU would give my MUCH better throttle response. At this point, it is just fun to have the MAF and M30 air box in there since they sound really cool (somewhere between stock and ITBs). I am making my plans for a switch to Megasquirt 3 Pro since the guys at diyautotune now have a breakout board with our 88 pin connector, so I do not need to chop up the stock harness at all. They even said that if I can get 10 people committed to buy, they will do a plug-n-play Megasquirt 3 Pro for the M42.
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Hi
Can you adjust output voltage on the maf conversion around 3000 rpm and trick the ecu? But to do that you would need a crank sensor as you previously mentioned. But you could possibly do something like that, by offsetting the voltage in that air flow range!
Cheers
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I like the progress with the maf conversion, and I cant wait to see if it ever gets anywhere. I know that Miller didnt want to touch anything for the M42 for whatever reason, and maybe this is part of it. I tuned my m42 via Tunerpro and an Ostrich with a wideband and made huge improvements over the chip that I purchased (the chip tune was terrible). I would love to play around with a conversion tune personally, Im wondering if changing the afm scale factors or some other maps may result in better AFRs...
I wonder if the afm chart is richer because of the acceleration enrichment. When the door opens quickly it adds fuel, so if there is no door to open will it still add fuel in the same manner? tuning around the enrichment was...interesting ;)
On another note, a plug and play MS would be great! Id be interested depending on price and a timeline.
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Slight resurrection...
I did a little more data logging today now that I am 100% certain that the long term fuel trim (LTFT) is fully in place. Here is a comparison between 2 of the runs I did today, and a couple from a year ago shortly after I reset the ECU.
(http://www.e30tuner.com/assist/b21_secondgear_ltftcomp.png)
What's what?
MAF 1 and MAF 2 lines are from today's WOT pulls in 2nd gear, and I last reset the ECU ~4 months ago during an audio project.
MAF 3 is a 2nd gear WOT pull from about 5 minutes after resetting the ECU.
MAF 4 is a 2nd gear WOT pull from about 10 minutes after resetting the ECU.
So, I think that the AFR's look fairly good, except in the 2500 - 3500 RPM range. The LTFT leans things out even more in that range. I am amazed that I don't have issues with knock since the engine has 11.5:1 compression and we only get 91 octane around here. It must be somewhat of a testament to Metric Mechanic's head and piston developments.
Anyway, I am going to try to work with MarkD to get a customized map that enriches things in that range a little so that I don't get that dead spot in the powerband anymore. What are everyone's thoughts on the rest of the AFR's throughout the powerband?
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To me personally, I think the whole of MAF 1 & 2 look pretty lean. I have mine tuned down to between 12.5 and 13:1. That's where you're going to get best power and mean best torque. Are you a till running moronic or did you get your mega squirt up and running?
Also, just wondering what you're using to log your afr's. I would like to do the same for my current and stock tunes and share them here. I have a feeling it may be nice for some people to see them side by side. The stock tune is really pretty bad.
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Maf 3 looks the best but even that is not great, but my question is was the Ecu in open or closed circuit with the Ecu. Was the engine warm?
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To me personally, I think the whole of MAF 1 & 2 look pretty lean. I have mine tuned down to between 12.5 and 13:1. That's where you're going to get best power and mean best torque. Are you a till running moronic or did you get your mega squirt up and running?
Also, just wondering what you're using to log your afr's. I would like to do the same for my current and stock tunes and share them here. I have a feeling it may be nice for some people to see them side by side. The stock tune is really pretty bad.
I ran these by MarkD and he thought that MAF3 & MAF4 were too rich for this engine. Maf 1 & MAF 2 are definitely too lean though, at least in the one spot.
I am still running a Motronic with a custom tune from Metric Mechanic.
Maf 3 looks the best but even that is not great, but my question is was the Ecu in open or closed circuit with the Ecu. Was the engine warm?
The ECU is running in closed loop, but at WOT it ignores the O2 sensor.
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Maf 3 looks the best but even that is not great, but my question is was the Ecu in open or closed circuit with the Ecu. Was the engine warm?
The ECU is running in closed loop, but at WOT it ignores the O2 sensor.
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But not the afm at wot, or in this case the maf.
Can you trick the ecu using the maf conversion increasing the afm voltage over that rev range/air flow range for that peak at 2000-3000 rpm.
Cheers
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Maf 3 looks the best but even that is not great, but my question is was the Ecu in open or closed circuit with the Ecu. Was the engine warm?
The ECU is running in closed loop, but at WOT it ignores the O2 sensor.
But not the afm at wot, or in this case the maf.
Can you trick the ecu using the maf conversion increasing the afm voltage over that rev range/air flow range for that peak at 2000-3000 rpm.
Cheers
[/quote]
Sure, it would be easy enough to modify my MAF converter to take RPM and throttle position as inputs and have it "lie" about the air flow in that range. However, I do not see that as a very good solution and my preference is to just get a proper tune. That is hard to do because nobody local can work with old Motornic units!
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I think maf 4 looks pretty good for the most part! Still a little off in some areas but not terrible. It could be leaned out in the midrange for sure.
You're still using the stock ecu with the MM chip correct? What are you using for the logs? I could take some logs of my car and post them with my tune to see what they're like. I may be able to help with the afr tuning aswell. I decoded the stock ecu files and have all the map locations. I've been using tunerpro and the stock ecu so far but will be switching over the MSPNP at some point.
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The logger is a custom-built unit of mine (shown near the beginning of the thread). Yes, I am running the Motronic + MM chip. If you could send me an XDF and BIN that would be super helpful, assuming that the chip I have still has the maps in the same places (MarkD did the tune from what I understand). I'd like to get a look at how the fueling table looks for the stock AFM, particularly in the 2500-3500RPM range.
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Dredging this up from the depths again...
I have been doing a lot of research into the stock ECU's map programming and stuff, as well as talking to SSSQuid about doing some live dyno tuning in December. For the time being, I figured enough things out to modify my WOT fuel maps and deal with the 2500-3500RPM leaning issue. Sure, enough, the maps all had a lean region in that RPM range, and I am convinced that it is precisely because the stock VAM over-reports air flow in that range at WOT thanks to intake resonance.
Here are some AFR comparisons from 2nd gear WOT pulls. The first 2 (green and blue) are with the base tune for my built engine. The second two (orange and yellow) are from today with the first round of mods I made to my WOT fuel tables. Not only are the numbers more sensible, but it has a lot more power in that RPM range. I did also make some small changes to the fueling near max 6000 to enrich things a little there too, although it doesn't look like it did all that much. It could be because my original pulls were done in the middle of summer, and today the temperature was a lot lower and the humidity a lot higher. Who knows.
(http://www.e30tuner.com/assist/AFRComp_27OCT2016A0.png)
Also, here is a little plot showing what all I did to the WOT fuel map. The values are converted to AFR's for ease of viewing (instead of the raw hex values from the BIN dump).
(http://www.e30tuner.com/assist/5A20_ComparisonA0.png)
So, in a month or two I expect to have a FULL custom tune done on a dyno. This excites me, because the car is fun as hell now, and I think that there may be a fair bit of optimization in the fuel and spark tables that has yet to be done. I will definitely post up the dyno results when those are in! This also puts some stuff to bed regarding the MAF conversion...to actually have it run right, you either need a modified WOT fuel table, or a MAF converter that also takes in RPM and throttle position so as to mimic the stock sensor's non-linearities.
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I just finished setting up the next stage in my logging adventures. These will be used simultaneously with the wide-band O2 sensor system to get my tune dialed in. Some remote tuning is planned for the near future, and then some live dyno tuning to get things perfected later in December.
Yes, quad EGT probes is overkill, but given the work I have put in so far, I want to see how well balanced the cylinders are. Some things I have seen in the MAF signal suggest that certain cylinders are slightly starved at some RPM's. Now it's time to see.
For reference, the threads in the stock header are M8x1.0, and as long as the threaded portion of the fitting is 11mm or less it will not protrude into the runner. The ID of the runners is ~32mm, and I adjusted the probe tips to protrude ~12mm into the exhaust stream. M8x1.0 EGT probe fittings are reasonably common, and I am thankful that BMW put standard bungs in the stock manifold. They are a bit closer to the head than is usually recommended, but since I am not planning long-term use of these, it should be fine.
(http://www.e30tuner.com/assist/egtsetup01.jpg)
(http://www.e30tuner.com/assist/egtsetup02.jpg)