M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => General Topics => Topic started by: bmwman91 on May 03, 2012, 01:33:13 AM
-
Many of you here were following my MAF conversion development thread last year. I lost a lot of my steam 8 months ago due to getting engaged and a job change, but I finally got around to dumping some cash into a first run of these. As some of you are aware, I had a timing chain failure and I am opting for a Metric Mechanic motor as the replacement. This got me thinking about the MAF conversion, and at the very least I wanted one for my new motor. Since the cost of producing one unit is silly, I figured I'd buy parts for 10 of them.
I probably won't have all of the parts for a good 2 weeks, and it'll take me another week after that to assemble & test a couple of them. My new motor isn't going to be ready until maybe July 2, so I can't do much with my car until then. Still, I have run earlier versions in the past and I know how to bench-test them to prove them out. Even still, I would like to see how things work out on a couple of other people's M42 cars. If you want to do a little beta-testing and live in the SF Bay Area (I'd consider folks further away if they are comfortable with electrical work and their M42 isn't their daily driver) let me know. I would probably need 2 - 3 people to help out, and you'd get a discount for it.
I made some improvements to the design (immersion-gold finished PCBs, industrial/MIL spec components, additional parts so users don't need open barrel crimpers) so the cost is probably going to push $250 as opposed to the initial $200 I had wanted to go for. While I don't want to charge more for it, those improvements in quality & ease of installation seem justifiable. The price is for the converter hardware; the MAF sensor is still up to the user to buy, and you can get them for $75-$150 new. Users can easily use open element air filters, or modify their air box a bit to use it with that.
Anyway, what sort of interest is there in this? All units will be hand built be yours truly (uugh!) since the cost of contract assembly isn't really sensible for quantities of less than 100. If these do well, I can invest the proceeds into a larger production run.
Thanks guys!
-
I think I would be interested.
So you were able to properly tune out the resonance peaks that you were seeing? (I can't recall what the exact difficulty was.)
-
Im running speed/density now so I dont need a MAF. I just want to say that a MAF can really help out the engines response. Hopefully people are interested in these. Have you posted the same offer on 318ti.org? Might be some intetested people there as well.
Also, have you looked into Millers MAF conversions? Not sure if they make one for an M42 though. Maybe you could use some of the components to cut costs like the MAF housing.
-
Hi,
Where in the Bay Area are you located?
What are the advantages of this conversion?
Thanks,
Dave
91 318is
in Santa Cruz
-
I think I would be interested.
So you were able to properly tune out the resonance peaks that you were seeing? (I can't recall what the exact difficulty was.)
Yup, no resonance issues at all. That's what 90% of the firmware is dedicated to!
Im running speed/density now so I dont need a MAF. I just want to say that a MAF can really help out the engines response. Hopefully people are interested in these. Have you posted the same offer on 318ti.org? Might be some intetested people there as well.
Also, have you looked into Millers MAF conversions? Not sure if they make one for an M42 though. Maybe you could use some of the components to cut costs like the MAF housing.
For now I am trying to keep this slightly contained since I am doing a small production run. Once everything looks good, I'll have a contract manufacturer make a bunch for me.
I am not 100% sure how Miller's conversion works. I think that they gave up on the M42 conversion too, probably because of the resonance issues. How theirs works is also slightly unknown...I do not know if they are just remapping the ECU and plugging in a dummy resistor in place of the temp sensor, or if they modified the firmware to actually use the mass flow rate. Either way, their setup requires a chip and mine doesn't.
Hi,
Where in the Bay Area are you located?
What are the advantages of this conversion?
Thanks,
Dave
91 318is
in Santa Cruz
I am in Mountain View.
The biggest advantage on a stock motor is an improvement in throttle response. The MAF is far more sensitive than the stock VAM. The stock VAM is pretty well sized, so not much power is to be gained on a stock M42, but a bored/stroked one with some head work would breathe easier with a MAF.
The other big advantage is reliability. Our VAMs are getting old, and a lot of folks are having issues with the carbon track wearing out & giving intermittent fuel cut, and lousy calibration which causes rich/lean running. This setup has no moving parts, can be cleaned with alcohol, costs about the same as a rebuilt M42 VAM and the MAF itself is cheap & readily available new.
-
I really want one but no funds in the bank for this. I will start selling some parts to see if I can get the funds by the end of this month.
-
Don't worry about hurrying. I won't have all the parts & materials for a couple of weeks, and it'll be a few more until I have them assembled, tested & out to a few beta-testers.
-
Great. I rather get your device than have my maf rebuild for $100. Right now I have a rough idle and 99.9% sure I have no vac leaks but get a maf code on the stomp test. So I either have bad maf, ICV is bad or rubber intake boot might have a leak. All hose have been replaced with silicone ones. Maybe FPR. I believe ICV is fine as it adjusts correctly with AC is on. A few times the idle hunts but mostly is just rough and in the morning it runs rich as I smell burnt gas. Just havent had time, time, as I have 1 year old and new house taking my time, not new job and wedding, did that 3 years ago so I know the feeling. lol
-
I love this sort of thing...one more problem with these great cars getting resolved! Why isn't this a sticky?
I'm in...
-
I like!!
Sidenote----- Hey dave saw a glass moon roof on e-bay for like a grand, I think it was you that put that on your want list in some other thread
-
I like!!
Sidenote----- Hey dave saw a glass moon roof on e-bay for like a grand, I think it was you that put that on your want list in some other thread
LOL, that'd be ideal! A roof worth more than my car! IIRC that roof has been on there for a while. At that price it'll likely stay right where it is...
-
Alrighty, the first PCB is going together pretty well so far. I had to reorder a couple of parts because I mixed up the packages (ordered SSOPs when I needed SOICs) and they should arrive Friday or Monday. From there, I have to keep my fingers crossed that I laid out the PCB properly and put the right resistors/capacitors in the right place lol. This is the only one I am hand-soldering...40+ 0402 components & a bunch of small pitch ICs...my eyes are sore. I think I'll use solder paste & a toaster oven for the rest lol.
-
Progress is good!
What off-the-shelf MAF will you be using? I'd suggest a Ford V8 unit to match my injectors, but that might be too big. I'm planning on a Ford O2 sensor to complete the set.
-
I am working with a Bosch / VW HFM5 unit. It flows up to 800kg/hr, which equates to 400 CFM at 25°C, and 311 CFM at -40°C which is the worst-case condition in terms of flow capacity. Since I doubt that anyone is out flogging their car at 40 below lol, the reduced volumetric capacity in cold conditions is a non-issue. Anyway, I like this sensor because it is readily available, inexpensive ($105 for a new Bosch one, less for off-brand & rebuilt) and it fits the M42 intake boot perfectly (75mm outside diameter of inlet & outlet).
I designed the system to be modular so that I could allow different MAFs to be used. The thing is that I need to get the operating curve of a MAF before it can be used with this setup, which means either trying my luck with Bosch or obtaining a new sensor & putting it on a flow bench.
-
What VW did that unit get installed on? Google tells me that some 5-series have them. New is better though, no doubt. One less potential problem.
Oh - forgot to tell you that I found an e34 535i at the yard. Figured I'd measure the airbox.
It was really small - especially after something short and very solid pushed it back into the front passenger wheel well housing!
I'll keep looking.
-
Haha thanks, Dave. I got a guy on eBay to give me the rough dimensions of one actually!
Here's the MAF:
http://www.ecstuning.com/Search/461L/ES517741/
This particular one was used on all VW 1.8T motors. However, there are 4 or 5 variants of this housing, all with the same sensing element & inner diameter that only differ in the mounting flanges & coupling details. This sensor/housing was used with many car makers, with anything from a 1.8L I4 to some Vw 4.2L V8's making ~360HP stock. It has more than enough flow capacity for any E30 motor, and even a stock M30 as far as I can tell.
-
I wonder whether the conversion will have an impact on fuel economy? It would seem that the MAF could possibly be more accurate, resulting in better economy.
-
Nah, I don't foresee any improvements in fuel economy. The stock VAM was pretty accurate actually. It really isn't a BAD sensor, but they are all old, worn out and very expensive to replace. The O2 sensor can help the Motronic to adapt to a lot of wear & tear on the stock sensors & stuff. The technology is old, but proven. MAFs are nice because they give much faster response and don't have moving parts to wear out, and at this point, the conversion should cost about the same as a rebuilt VAM.
-
^ this is the point I will get one. With the new house and baby, a s52 swap is way to down the road so I need to keep my m42 running heathly with a few perks...
I do have one question, what if you add a chip to the ECU? Does it hava better impact with the MAF? Anything else need to be done to the MAF?
-
You should not need to do anything differently with the MAF conversion, no matter which chip you run. An aftermarket chip wouldn't take any MORE advantage of the MAF though, since chips don't make changes to the actual executable code for the ECU, just the look-up tables for fuel & spark. At this point, the MAF is "faster" than the old ECU in these cars!
Now, if one were to increase their M42's displacement, I think that the MAF would start to confer even more benefits.
-
Well, today was a good day. I got enough of the wiring harness assembled to bench-test the first PCB, and it works more or less as expected! The various settings work properly, the outputs are clean & in the proper ranges, both the analog & digital filters appear to be working as designed, serial communication works, firmware updates apply properly and overall the thing looks like it will be good enough for use in a first batch! There is still some testing to be done, and a few little nagging annoyances were found in the user interface that I want to correct, as well as some random misbehavior when the power is turned on & off repeatedly while the USB cable is connected to a PC. So, none of the issues affect normal operation, which is good, but I want to clear them up as best I can anyway.
I'll probably need another week or so to get this one all done & to my liking. Thereafter, I will see about assembling 3 more to send to "beta testers". It will require a little cutting of the factory harness, but the parts that will be supplied will make conversion between this & the stock setup truly plug & play. The only tools someone will need will be some plain old crimpers for butt splices & a heat gun for those splices' insulation (a hair dryer might work too, maybe).
Keep in mind that this doesn't include the MAF sensor. They range from $70 rebuilt to $110 for a new Bosch one, to $220 for an OEM VW one (same as the Bosch one, but pricier for no reason).
-
Hey - I'm next door in Sunnyvale and about to be on summer vacation. Lemme know if I can be of any assistance.
-
Would some porting/head work & little hotter intake cam add to the benefits of the MAF conversion?
-
Would some porting/head work & little hotter intake cam add to the benefits of the MAF conversion?
Yup, an M42 that sucks more air than a stock one will get more benefit from the MAF. The stock AFM is well-suited to a stock M42, but once you start pulling more air, it does start adding a bit of restriction.
-
Hey - I'm next door in Sunnyvale and about to be on summer vacation. Lemme know if I can be of any assistance.
I'll let you know...my car is out of commission for the next month or so. With that being the case, I'll need a couple of local "test subjects" haha!
-
I figured that some of you might like to see some progress pics. Here's the first module. I am still working out a few details on the wiring harness, but this is the general design. One thing I still need to do is track down some potting adhesive to seal up the little plastic box that the converter lives in. The trick is finding some that does not harm electronics or corrode metal since it will sort of be sealed into the box with them!
Anyway...enough babble.
Top side of the motherboard. Voltage regulator, power resistors, poly-fuses & the USB comm chip.
(http://www.e30tuner.com/sales/maf001.jpg)
Bottom side of the motherboard. DSP controller, poly-fuse protection on the 5V input from the ECU, DAC, anti-aliasing filters and reconstruction filter.
(http://www.e30tuner.com/sales/maf002.jpg)
Parts are industrial grade where needed. I worked out all the power dissipation calcs for worst-case scenarios, and this sucker can operate with the air under the hood at 107°C, minimum.
Here's the wiring harness & its components. The thermistor module is modular so that any car can use this once I determine the NTC parameters for the thermistor in the original AFM. Just about every AFM uses a different one (M42, M20 & M30 are all different...I wonder if M20 guys with M30 AFMs know this...).
(http://www.e30tuner.com/sales/maf003.jpg)
I made most parts of this easily disconnectable so that users can easily swap this in & out. The power harness is sort of permanently installed since you need to splice it into a 12V line from the main relay, but the rest is easily removable. You may notice the M42 AFM plug on here...I was given one of those AFM extensions by another member here and I have found a source for the connector housings. The bad news is that there are only 26 of those rubber boots for the plug left in the WORLD!
The plan is to sell this with a pig-tail that is spliced into the stock AFM harness. All you need to do is match wire colors, crimp some butt splices & put on the sheathing that I supply. There will be an extra pig-tail for the stock AFM connector that you have to chop off so that you can easily put it back. I may offer the M42 plug as an option, but it will add $50 to the cost of the kit and add around 4 weeks to the lead time since the parts all have to come from Germany.
-
I like it.
John
-
That is tremendous - the thoroughness of your work is impressive.
The modular setup is a great idea too. I'll bet most buyers will opt to simply cut the stock harness and install your updated parts. OEM is nice for a cherry low-mileage coupe, but a lot of our cars are no longer pristine specimens and don't carry much value...:rolleyes:
-
That is tremendous - the thoroughness of your work is impressive.
The modular setup is a great idea too. I'll bet most buyers will opt to simply cut the stock harness and install your updated parts. OEM is nice for a cherry low-mileage coupe, but a lot of our cars are no longer pristine specimens and don't carry much value...:rolleyes:
Ha yeah tell me about it. My car isn't really a pristine show-room sample. The motor that is coming in a couple of weeks needs its own insurance policy lol.
I am going to test this out on my sister's E36 M42 later this week. I expect everything to be fine since my bench-tests show it operating properly. Then I should be able to test it out on my new motor, and then start building some of these! I may see if I can work out some sort of adapter plate to sell with it (for those that want to keep a stock look & chop up their stock air box a little...I passed CA SMOG with a setup like that), although all anyone really needs is some 2.75" OD acrylic tubing from TAP plastics and a cone air filter.
-
Congrats on getting the new engine going. Were there any plans on this MAF?
-
Glad to see this have been done the correct way. Amazing work
-
This would go great with my itb setup :)
-
Any updates on this? I know you are busy with wedding plans and I do know how much time that can take. And if you have kids, time, wait what is that..lol
-
Yeah any news on this? I haven't been here for ages and just seen this thread. I would definitaly buy one.. In fact I'm the one who e-mailed you in 2006 to buy your kit but, at that time you weren't willing to sell because of this low rpm wot hesitation issue.
-
Aloha from Maui. I'm out on my honeymoon for now, but I am expecting to finish this up when I get back. The whole, "engine blowing up and waiting for a custom built one for 6 months" thing sort of put a big delay on this project!
-
Aloha, enjoy it.
-
Are you still in Hawaii? If you make it over to Oahu, let me know- I live here. There are a lot of really nice e30 owners here
...and I'm interested in your conversion, but am running Ford injectors, Mark D 92 oct chip, COP kit and Ford o2 sensor; any inherent issues? Would simply adjusting the stock cams lend any benefits with your conversion?
-
Still in Maui, flying out at 1PM tomorrow from OGG. Uugh, I don't want to go home...Hawaii kicks ass.
I plan to come back in the relatively near future...I'll let you know. It would be cool to meet some "tropical" E30 owners! How much do they sell for here, seeing as how the supply is pretty limited?
The MAF conversion will work with any setup. As far as a stock ECU is concerned, it is reading a stock AFM that just responds a lot faster lol.
-
Whats up man, haven't been on here in a long time.
I am really interested in one of these, especially now that my engine is supercharged. I live in Santa Clara as well.
-
So any updates?
-
Yeah I would certainly be interested in purchasing this if and when it is ready.
-
Alrighty, quick update.
I have been working on this quite a bit in the last few weeks. I did some testing and found that there were a couple of areas that I could improve things when I was using the MAF with my mega custom M30 air box and Rally 2100 engine. Talk about a worst-case setup! The hot cams and larger air box volume actually make some crazy resonances. Totally manageable, but I am reworking parts of the controller firmware to handle it properly. I also discovered some circuit design improvements that I can make, that also add another degree of protection to the Motronic's 5V output. So I am working on a way to apply the new circuit connections without re-ordering $500 worth of PCBs, if possible. If I can't find a super robust hot-fix, then I'll order new ones to be certain of the quality.
Another part of my testing involves building a 50,000 sample per second data logger (10,000 samples per second x 5 channels) with hefty analog and digital filtering. I want to collect PRISTINE voltage information on the inputs and outputs of the MAF converter, the stock AFM and the AFR from my wide-band setup. That will allow me to make the final fine-tuning adjustments to this. The hardware for the logger is 95% done, and the firmware should be complete in a couple of days. I'll be in Austin all this week for work...which means LOTS of time to work on this project at night in my hotel room! If anyone here is in the Austin area and wants to grab a beer, let me know.
From there, I just need to order up a solder paste stencil and get an old toaster oven so that I can reflow solder all of the awful little 0402 components (0.04"x0.02" / 1.0x0.5mm) and other crud on one side of the PCB faster. My hands and eyes will break if I have to individually solder 50+ little components 20 more times lol.
-
Your work is humbling, to say the least. Out of curiosity, how much of your last tweaking is actually functionally necessary and how much is striving for perfection?
-
Another question out of curiosity, knowing you have thought of this. In your sampler, why implement filtering in the firmware when you can post process on your PC?
-
I'd say 60% for perfection, 40% for necessity. There actually are some improvements that I hadn't thought of that will make this a better product for people. I wouldn't try to go for 100% perfection...this thing would NEVER be done! It's 95% of the way there anyway.
Digital filtering helps me to lower the analog anti-aliasing filter requirements. It sounds super complicated, but really the filter can be designed to my requirements in about 5 minutes in MatLab and I have implemented them many times so it is easy to implement them in firmware. The DSP microcontroller in the logger can actually apply the filter much more easily than PC software since the microcontroller has specific single-cycle instructions for exactly what I want to do!
I am interested in signal data in the 0-1000Hz band, nothing else. Years ago I made a little data logger module to read similar voltages, but I ignored the whole aliasing thing and got lots of ugly readings. Lesson learned. If I want clean data to simulate my converter's performance with, then it all needs to be very clean. The analog input sections on the MAF converter filter out anything above 1000Hz so much that I don't need to worry about the effects of high frequency noise. I already proved out that stuff a while ago with a frequency generator and oscilloscope. The big challenge is handling the low frequency pulses as intake valves open and resonate in the intake track.
-
How would something like this work with tunerpro/ostrich 2.0
With n/a itb build or a boost build?
Very interested for it!
-
It should work A-OK with any ECU. If you are working with a stock ECU and tuning it with tunerpro, you don't need to do anything different. The ECU thinks that the stock AFM is there still, except it is more responsive!
-
Awesome.. Be sure to include me with the first batch!
-
I'm now an expert with 20 minutes of google search experience... Feel free to ignore these questions, from what I've read, it is a more complicated and interesting topic than I would have thought it would be.
It sounds like you are attempting to eliminate the effect if resonance in your intake on the MAF that the AFM isn't affected by?
Doing that means that you would need to ability for others to control that algorithm for their own setups?
In a perfect world you would just put an AFM and a MAF in series, suck air through them, and generate a lookup table for the conversion. Do you know how much difference you are getting in the real world is due to your unique input configuration?
How difficult is it to get proper air flow through a MAF? Interesting that it is possible to have uneven flow through a MAF so that it either under or over reports air flow. Also interesting that resonance causes an additive effect as the air is measured flowing in both directions.
-
You can put a MAF and AFM in series and make a simple lookup table, but it will only be valid for the one air temperature that it was done at. The MAF reports kg/hr of air flow, and the AFM reports m^3/hr. They are related by density, which is primarily affected by temperature changes in daily life. Altitude also factors in. My converter does the density conversion in real-time so that the MAF's kg/hr output becomes true m^3/hr output for the ECU, since that is what it is expecting to do correct fuel calculations.
Resonance is a bigger issue with MAFs because they are much more sensitive. The AFM has slow response, but that gives the advantage of dampening the intake pulses so that the output looks smoother, albeit delayed. The MAF can easily resolve individual intake pulses and its output looks sort of like a sine sweep of varying amplitude and offset. Being that the sensor has a non-linear transfer function, you do not get good results when applying analog filtering since analog filters are, at least in their normal operating range, approximately linear. In short, putting an analog filter on the MAF output will cause you to run very, very lean at WOT. The filtering must be done in software so that you can account for the non-linearity of the sensor.
The filtering algorithms are set, although selectable by the user (and you can turn it off). A 6 cylinder would likely need less filtering than a 4, and an 8 would need even less thanks to valve overlap. Users do not need to tune much of anything in most cases, unless they are going stand-alone and want to really customize the air flow voltages to make tuning easier. Otherwise, everyone else can treat it like the stock sensor is still in there.
-
Interesting stuff, thanks for sharing.
-
I know you kind of addressed this already, but to be clear, will this work with say a stock BMW MAF from a 328 or something? Will custom programming be necessary to get it to work with different MAFs, or will it say work with a few standard MAFs and anything not on that list will need custom programming?
I ask because I have a nice Bosch 3 inch MAF from a m3/328 and it'd be real convenient to be able to use it some day :)
-
So, the thing is designed to be very easy to configure to emulate a variety of stock VAMs. However, it is not really set up to be easily used with lots of different MAFs. If I had set it up so that you could fully adjust the MAF and VAM parameters, it would basically be another Split Second setup where you really need to install a wide-band O2 sensor and spend a bunch of time tuning stuff. The benefit of this is the no-hassle setup, with the restriction of using specific MAF sensors that I have very, VERY accurate data for the output of.
The other tricky part is the wiring. As of now, I have been able to source all of the required stock connector housings and terminals for the MAF that I have selected, which allows me to build a high quality wire harness. I can always sell a version with no MAF connector that users can attach a chopped wiring harness from another car to, as long as I am able to get the right data about the sensor. And of course, it needs to give 0-5V DC output and use +12V/GND/Vref/Vout connections. Some Bosch sensors also have a self-clean mode where they draw a ton of current for a few seconds to burn crud off of the sensing element...not a big deal, but you'd need to put a beefier fuse into the harness I include.
I do plan to add more MAFs to the controller software so that people have a little more choice. For now, I am focused on the one that I am because it is cheap, easily available and can flow plenty of air.
-
Awesome :)
-
Any updates? I am running an 8.5 pound flywheel, and if i am not careful the engine will occasionally stall when revving down to idle, do you think this will help that at all? I figure the AFM may delay the engine getting air again/delay the air reading
-
Any updates? I am running an 8.5 pound flywheel, and if i am not careful the engine will occasionally stall when revving down to idle, do you think this will help that at all? I figure the AFM may delay the engine getting air again/delay the air reading
OT But with my 11lb flywheel the car likes to idle more around 1000 rpms. You can adjust the throttle cable to bump up your idle a bit to keep from stalling.
-
Any updates?
This would be perfect for my turbo seeing how my afm just blew up from being on the boosted side.
-
bump also interested
-
BMWMan might have this project on hold, given the car troubles he's been having. Keep your fingers crossed - hopefully he'll have a few units in the pipeline soon.
-
Any news ?
-
Sorry for having this totally fall off the burner. My car has basically not been running for the last year, and then stuff like a wedding and buying a house happened which further distracted me. The car should be alive in a week or two, and then I get to spend a month or so ripping out 1200 square feet of carpet and refinishing old hardwood floors in my house lol.
-
Its all good... I was in your boat 3 years ago... Now i have a little one who is taking up a lot of my r&d time for my car.
-
Hope you get your car running soon and the reno work out of the way. :D
If you get back on this project I would be very interested in a kit or I can beta test if you like (pretty clever with electronics)
Before I found this thread I saw that MAF on ECS Tuning, got me thinking.
-
haven't checked in on m42club in a while- glad to see you made progress on this project. we talked a while back about using a 750i ECU to do a MAF conversion, but what you've done here allows the use of chip tuning, so even better. i'm definitely in when it's available; i'm pretty sure the VAF meter is holding me back from making power on the top-end with the DBilas setup.
hope married life is treating you well and good luck with the house project.
-
Hi bmwman,
I've been away from our forum for a long time and I was assuming that you have finished your kit and has sold many of them already. And finally I logged on to buy one for myself with a tought of finding a burning threat at the very top of the other threats. But, I have found a deserted one :( So I did read the last messages and I can see you are busy with the new responsibilities. I wonder, are you planning to go back to maf kit project any time soon?
-
i m still thinking reading bout the maf conversion..i was just wondering why cant we use a maf which give the out put 0-5volts instead?
like this one here http://www.ebay.com.au/itm/BMW-Air-Flow-Mass-Meter-Sensor-MAF-E46-318i-318ti-316i-316ti-0280218075-/261196365638
thank u
-
I'm in, love to get rid of the afm!
-
i m still thinking reading bout the maf conversion..i was just wondering why cant we use a maf which give the out put 0-5volts instead?
like this one here http://www.ebay.com.au/itm/BMW-Air-Flow-Mass-Meter-Sensor-MAF-E46-318i-318ti-316i-316ti-0280218075-/261196365638
thank u
Just about all automotive sensors operate on a 0-5V range. The issue is getting the right transfer function (look up the term). The ECU expects a very specific voltage-vs-airflow relationship, which is specific to the stock AFM part. On top of that, a MAF's output is proportional to mass flow rate (kg/hr) but the stock AFM's output is proportional to volume flow rate (m^3/hr). Assuming barometric changes are minimal (altitude), the two are related through air temperature. Conceivably you can hook up a MAF to the stock ECU/chip and it will run just fine at ONE temperature. Once air temp shifts by more than 10 degrees Celsius, the ECU will not be getting the right information from the MAF anymore and your mixture will start to get a little lean/rich. You could stick a fixed value resistor onto the ECU's air temp sensor pins and fool it into thinking that it is a constant temperature outside which would bypass that issue, but you may have knock problems on hot days since the ECU does retard ignition timing when the air is very hot. And of course, I do not know of any MAF with a transfer function that matches the stock AFM's transfer function at any normal temperature. I went through all of this in 2005 when I developed my first converter and the "temperature fooling" method doesn't work well.
ALL of the above ignores the fact that the M42 has some pretty heavy resonances in the intake/air box, and a MAF is so sensitive that it will have very large output voltage swings during these resonant modes that the ECU cannot properly read. The signal swings are bad enough that the ECU will stop injecting fuel under 100% throttle conditions from 2300-3000RPM. Using a cone air filter helps by eliminating the cavity resonances in the stock air box, but the stock air box really is best and chances are that you will lose power from using a cone filter.
I really do apologize for letting this project die. After I got my last set of prototypes together, I realized that there were some things that I didn't like about how I designed it, and while it worked, I just wasn't comfortable selling it without correcting some things. Too much of an engineer here I guess, but I don't want to commit to taking people's money for something that I know has little issues. The project has been under part-time development again, and the next rev should be better than the last one...it's all a big learning experience. Working on my house still takes priority (happy wife = happy life lol), but the next revision of the MAF converter is seeing some development at least.
-
thanks for the good explanation..if i hook up a 5v maf wit a temperature sensor..together wit a air fuel controller like safc...i guess wit a proper tuning it will work right?
-
thanks for the good explanation..if i hook up a 5v maf wit a temperature sensor..together wit a air fuel controller like safc...i guess wit a proper tuning it will work right?
It would work at the one ambient air temperature that you tuned it at. At other temperatures you would run lean or rich. In short, you can't just plug a MAF into an ECU that was programmed for an AFM because the two types of sensors measure two different things (related, but different). You would need to modify the microcode in the ECU to use kg/hr input rather than m^3 input, and unless you have spent a lifetime working with automotive embedded controls, you can't do it. I can't. Only a small handful of people can. My converter works from the outside, and even that involves a few thousand lines of microcode and some fancy digital filter design software. Which brings me back to the other big point...the MAF is "too sensitive" and the signals it gives the ECU at certain RPMs will cause fuel cut. That's why you need the fancy digital filtering stuff.
-
Bugger
So when will this conversion be available roughly?
Is this similar to what split second has done?
-
gosh..i guess there is no short cut or cheap way to do this...damm
-
gosh..i guess there is no short cut or cheap way to do this...damm
None that I am aware of. If there was, everyone would be running a MAF instead of the VAM.
The good news is that you really are not losing any power on an internally stock M42. Unless you are making over 180HP at the crank, chances are that a MAF will provide no benefit to power. Throttle response does improve a bit, but most people seem to think that the MAF is all about making more power.
-
Hi my name is Mark and I live in Reno... I am really interested in your project trials...That is if I am not too far from you. I have a 1979 320i with a e36 m42 swap. I am really sick of chasing the gremlins in this afm setup. Poor idle, poor throttle response, etc... PLEASE let me know how it all works out and if I can get my greasy paws on a setup!!! Thanks again.... :)
-
Do you think that some of the noise/resonance in the intake was caused by the twin-plate throttle body vs a regular throttle body?
-
Do you think that some of the noise/resonance in the intake was caused by the twin-plate throttle body vs a regular throttle body?
No, that isn't really the issue. Every intake has resonant modes. It's just a hell of a lot more pronounced on a 4 cylinder since there is basically no intake overlap, so you end up with big discrete pulses. If you look at many 4 cylinder cars with MAFs, you will see resonator chambers (Helmholtz resonators) on the intake which are there to help damp out the resonances. The rest can be dealt with by the ECU. The Megasquirt guys had a heck of a time getting a MAF to work properly with 4 cylinder engines, and they finally worked it out, but they have access to information like crank position, so they can basically average the air flow value over one intake cycle. Anyway, that's not really an option with this converter since the goal is to not have to hack up any more wires than necessary.
-
Hi my name is Mark and I live in Reno... I am really interested in your project trials...That is if I am not too far from you. I have a 1979 320i with a e36 m42 swap. I am really sick of chasing the gremlins in this afm setup. Poor idle, poor throttle response, etc... PLEASE let me know how it all works out and if I can get my greasy paws on a setup!!! Thanks again.... :)
Hi Mark,
A well maintained M42 will idle just fine with the stock AFM, and the throttle response shouldn't be too terrible. It sounds like you may have some vacuum leaks or other old sensors causing you trouble.
-
Is this going to happen? I am interested in it for my DASC m42
Also I have a lightweight (8.5lb) flywheel and sometimes the cars stalls when the revs are coming down, would this help with that at all? Really only happens like once a month so I guess its not a big deal
-
Hey Nick,
It'll happen someday. Got a lot going on and I am not working on it actively at the moment.
I doubt that a MAF would help with your stall issue. It sounds more like a gunked up ICV. You have probably shot carb cleaner through, but I recommend submerging it in rubbing alcohol. I did that for a few hours and then shoot it up good with my fingers plugging the inlet/outlet. After a few rinses through with more alcohol I stuck it in an oven at 150 degrees for a few hours to evaporate the remaining alcohol inside. That helped my idle tremendously, and my flywheel isn't much heavier (11.5lbs).
-
Did you submerge the whole ICV or just the end?
I think the biggest reason I am interested in this is that it will let me run a bigger air filter, the biggest one I can fit now must has less area than the stock filter.
-
Yeah, dunked the whole ICV. Sloshed it around to get the air pockets out and let it sit for a while. Capped the tubes with my fingers and shook vigorously. Drained it out. Repeated that a few times. Everything was good thereafter.
What sort of intake setup do you have right now? The stock M42 AFM is good for around 180bhp before it hinders things, and even at 205bhp it might only rob like 2-3hp (and it doesn't hit max output so it's still accurate). Based on my experience adapting the M30 air filter box to my car, it is doable with the stock AFM too. You just have to cut a little more off the top.
-
Lol this is my intake. the afm is so long there just isnt room for a big filter. I have a tiny cone filter on there and its wedged up against the fender. Also FYI I am located in the bay area!
(http://www.tenhulzenautomotive.com/uploads/2/2/8/4/22847328/1863062_orig.jpg)
-
Damn, call me jealous...the DASC is a very rare bird! I'd definitely love to take a look at that setup sometime!