DIY PROMDo It Yourself PROM chip burning help. No PROM begging. No PROMs for sale. No commercial exchange. Not a referral service.
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Im going to guage some interest in a LS1 Maf to TPI MAF converter. I had some ideas about making it programable and using a Micro to offer sort of a improved translator but make it specific for the TPI crowd. is there any interest ?? if so get with me Via email.
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SIGN ME UP!!! I have a 1988 Vette with a Lingenfelter Super Ram and I would really like to use an LS1 MAF...let me know if you plan to build these and how much $$$!!
Thanks, Justin
Z is this just a converter to use a different MAF for a MAF bin? I was looking at the page and they have some MAF - Speed Density setup but it is very vague as to what it does. It would be nice to be able to take a SD car and use a MAF to get it close. I think the tuning would be a lot quicker and easier.
I'm interested. My Wells maf sensor just died and I'm back on the stock maf sensor. The maf airflow at idle with the wells was 17 gm/s with the stocker it's 14-15.
If you want a converter, one can be made for about $30 using an analog freq. to voltage converter. I have some schematics that I can post. If your proficient at soldering, it can be made using a project board. The DIY converter actually works pretty well with an older MAF ECM. I used it for a few years with no issues.
If you want a converter, one can be made for about $30 using an analog freq. to voltage converter. I have some schematics that I can post. If your proficient at soldering, it can be made using a project board. The DIY converter actually works pretty well with an older MAF ECM. I used it for a few years with no issues.
Man that'd be great. I'd really like to have that info. I work in a telecom switch, and have most all I would need (atleast i'm pretty sure for the most part) My MAF took crap, and I intentionally did not buy a new one b/c I wanted to see if there was an upgrade availible to the newer style. (reliability wise)
I originally used a stock 05+ Mustang GT slot-style MAF along with a 10 k resistor to increase the sensor's useable range to 6 volts and divide it back down to 5 volts for the ecm.
I'm now using a PMAS HPX slot-style sensor due to it's increased range without need for the voltage divider.
In my present housing, the HPX sensor has enough range for 10-11 psi at 6,300 rpm. I am getting close to the 5 volt limit with a maximum recorded voltage of 4.86 volts, but its sufficient for now and can be extended further if necessary.
In a "straighter" 3" diameter housing, this sensor should have enough range for about 600 rwhp at 5 volts. My housing bends seem to be reducing the range somewhat.
As far as I'm aware member bl85c is using the older tonsil-style Ford MAF from a t-bird in his application. Either style Ford sensor will work.
The MAF's calibration will be strongly dependent upon the individual sensor style and housing diameter as well as the configuration of the tubing if there are any bends, etc. A custom calibration would need to be developed for each individual application.
The only hardware change (besides wiring the Ford connector to the existing harness) is swapping the MAF signal wire at the ecm to one of the existing MAP sensor input pins.
Ok... I looked back and it doesnt look like I actually made any schematics. I pretty much just went on Jameco and just bought whatever they had that worked. The converter is based around the LM2917 14 pin package. Basically the conversion from frequency to voltage is done by a charge pump that basically turns on and off with the frequency and unloads into a capacitor/resistor. In the spec sheets for the LM2917 (attached to this post), they give the general equations for selecting the resistor and capacitor. The actual values aren't too critical, but the tolerances ARE. I remember having to use the following silver mica capacitor http://www.jameco.com/webapp/wcs/sto...ductId=531039& that has low tolerances and maintains a uniform capacitance over a wide range of temperatures. The resistor used also has to be of a low tolerance, like 1%, so that the converters output is consistant.
Also needed is a 12V voltage regulator and protection circuitry for the converter. You will need a 36V high current transient surge supressor along with a resistor/capacitor low pass filter to provide relatively clean power to the converter circuitry. The transient voltage surge supressor is needed for the inductive voltage spikes from the starter and alternator.
Tomorrow, I will try to dig up the converter and take some pictures as well as draw up the basic schematics for the converter itself. I posted a general schematic here: http://www.thirdgen.org/techboard/tb...my-latest.html (check out my latest mod), but its probably about as clear as mud as to what needs to be done.
Last edited by dimented24x7; 11-20-2008 at 12:17 AM.
Ok so now I have the general idea on what needs to be done. I have an LT1 MAF on the way, and today I stopped at a local parts place, and picked up the lm2917 14 pin integrated circuit, a printed board, and a project box (various resistors/capacitors) Not sure on what resistors go where yet, and what wires will connect to what pins, but working on building a schematic. Diminted, if you happen to get time to shed a little more light on it, I would really appreciate it.
My MAF crapped out, and this is my only car, and I don't want to run the bosh sensor b/c I personally think it is garbage and way over priced. One of my friends gave me a ford maf from a 99 ranger, and I made it work, but the check engine light stays on (ofcourse) so i'll just use it til I can either get the info, or figure out the rest on the LT-1 MAF.
Again, I really appreciate the help on this guys.
Chris
The only hardware change (besides wiring the Ford connector to the existing harness) is swapping the MAF signal wire at the ecm to one of the existing MAP sensor input pins.
The rest is all done with the tune.
Note: There are some special programming changes required to read the MAF signal instead on one of the MAP input pins. Perhaps this was not obvious in my original post.
The MAF A/D channel reads must be changed from channel A to the new input choice. This is easily changed in the bin if you know the correct addresses, but this isn't common knowledge as far as I'm aware. Let me know if you need assistance.
The 5 volt pull up on the normal VMAF input circuit interferes with the Ford MAF signal. This is why the input change is required.
Ok so now I have the general idea on what needs to be done. I have an LT1 MAF on the way, and today I stopped at a local parts place, and picked up the lm2917 14 pin integrated circuit, a printed board, and a project box (various resistors/capacitors) Not sure on what resistors go where yet, and what wires will connect to what pins, but working on building a schematic. Diminted, if you happen to get time to shed a little more light on it, I would really appreciate it.
Chris
I haven't forgotten about this. I dug the old converter out of storage. I just need to find a working camera to take a pic of it (the CCD crapped out in my good camera). I will also crack it open and see what resistors I used. The 2917 has an internal zener diode voltage regulator that regulates the supply voltage to 7.56 volts, so potentially you could omit the external voltage regulator mentioned above, but I would recommend using a 12 volt regulator anyway for some extra safety. I think I did use the 2917, but if I used the 2907, the resistor/capacitor values that you need may differ due to the difference in supply voltage
Heres the schematic as well as some pics of the converter. The schematic shows the bare minimum number of components. Its STRONGLY recommended that you also use a +12V regulator as well as the voltage can go up to 36V, and this could expose the signal side of the MAF and the IC to potentially damaging voltages if the alternator fails. Also, the 1A fuse is a slow blow. If you use a fast blow fuse, you may want to use a 1.5A so it doesnt blow out when the circuit is first switched on. The filtering cap acts like a short circuit when the converter first gets power. As a last note, teh 1000 mF cap should have a min. 36V rating, or it may go "POP!" when you turn on the ignition.
Also, Im definitely NOT an electrical engineer, so maybe of the EE's could review the design? It worked well in the car, but Im sure some improvements could be made to it.
Last edited by dimented24x7; 11-22-2008 at 05:50 PM.
Ok, so I just finished building this unit. We'll see how it goes, hope I did it right. I guess i'll know when I get my LT-1 MAF in the mail. The ford MAF is still holding up, but there's just something about having ford parts on my car that I just don't like.. lol
Cool. Do you have a DVM with a frequency read in function? That really helps in verifying the operation of the circuit. The voltage output will be 1000 x 10^-12 x 55 x 10^3 x 7.56 x maf output frequency in Hz. I remember the converter being pretty close after I was done, which was surprising given that the MAF output is actually an uneaven duty cycle pulse train.
Another thing to note is that at idle, the LT1 MAF has a very low output. This will cause the idle AFR to vary in a step-wise fashion due to the low voltage output to the 8-bit A/D converter. One way around this is to use a 0-100 kOhm trimming pot in place of the 55k resistor if you find it to be objectionable. More resistance = more voltage for a given frequency which equates to more resolution. But, it limits how high an airflow you can see as the voltage will peg sooner.
your circuit looks fine. The only things that could be done different, aren't a big deal.
you could also place a diode inline of the IGN source, this way, any negative spikes never make it through the diode. the transorb sort of does that already. and the other thing would be to use a pi filter instead of a T filter, with an input cap, series inductor, and output cap. this would truly make the power clean, and might improve the conversion, or at least, make it more consistent. probably not a big deal though.
I put the LT1 MAF on, started the car, but it didn't work. I pulled the wire that goes to the computer, and measured the output, and the voltage goes up as the the throttle increases. I connected my scan tool with it hooked up, but the grams/sec does not change when the engine is reved up. Any suggestions? seems I might have something wired wrong. On the stock maf connector I am seeing 14 volts on the blue wire, and red wire, with the engine off, key on, I am seeing 5 volts onthe green wire. The black wire is ground, and the black w/ white stripe is also ground. I believe the black w/ white is the return to the computer where the output wire should be going to the computer.
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Also one more thing, When I put the stock maf on, and watch it during engine operation I am seeing the element wire glowing red hot, then it cools, and does it again. I didn't think it was supposed to do this. Thought it only got that hot when you turn the engine off, and it goes through the burn-off cycle. Is this correct, or do I need to swap out the relay?
Last edited by 92 Vert T/A; 12-02-2008 at 10:53 AM.
Reason: Automerged Doublepost
Edit:
Oops... Looks like the problem might be on my end
I forgot to show teh 10k resistor on the voltage output. There needs to be a 10k resistor on the voltage output tied to ground. Without this, theres no sink or source current in the output (and hence no output). Try it and see if it works.
Last edited by dimented24x7; 12-02-2008 at 06:22 PM.
Man, that's good news. I'll try it and see what happens. It will be funny to watch my fellow TPI friends wonder how an LT1 MAF is working on my car. I'll post pictures when I get it all looking pretty.. lol
Glad to hear it works. I'll have to update teh schematic above with the correct one showing the missing resistor. Have you had a chance to run the car off of the LT1 MAF?
I added the resistor while I was at work yesterday, and tested it out on the way home. It ended up throwing a check engine light when I was about a block from my house. I have a scanner that I plug into the diagnostic connector so I can monitor what it is doing while driving, and it still looked ok, but that could be in limp home mode. The car wasn't running bad though. Not sure what it's doing, but I'll mess around with it more over the weekend. If I take the lead going to the black wire on the harness, and disconnect it so I can measure the voltage that the computer is getting, about what should it be at idle?
Also keep in mind that you will need to update your MAF tables. The LT1 MAF will have a different curve than the stock MAF as it goes up to around 400 grams/sec. You can make your ECM see more than 255 grams/sec by altering the injector constant.
For instance, halving the injector constant can allow you to represent up to 512 grams/sec. If you actually have 30 #/h injectors, but you type in 15 #/h as the injector constant in the ECM, the ECM will give injector pulsewidths that are twice as long as they should be. This means that your doubling the ammount of fuel delivered. You can then restore the correct fueling by halving all your MAF tables. This means that you wont have to worry about pegging out at 255 grams/sec, as you will never reach that value. 255 in one of the MAF tables in the ECM would now correspond to 512 grams/sec. The only downside to this is that it halves your resolution in the uppermost tables as the airflow is in 2 g/sec increments.
As far as I'm aware member bl85c is using the older tonsil-style Ford MAF from a t-bird in his application. Either style Ford sensor will work.
I'm using this maf with decent results, however I'm experiencing my share of issues lately. Fast355's also using this maf on his blazer without an issue.
