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Originally posted by tweaked Look. I am sick of the people that say this can't be done or that a halteck is the answer. in some classes of racing you can't use aftermarket fuel managment. other people could do this to get more power that can't afford $3000 for the new computer and somebody to tune it right.. there is no mouse trap syndrome under my hood. the MAF is a self contained box with a throttle cable comming out of it. If you arn't going to help me then shut the hell up!. I don't want to be rude but this sux ass. everytime someone wants to try something new, a few people attack them for thinking out side the box. If I could get this to work I am sure there are several people that would want the how to. The MAF is another Mazda mistake. it robs power plane and simple. the computer only goes into open loop at very high engine operation. it can't prossess fast enough to keep up with the changes that happen above some where around 5500 RPM at the other end of this shaft, in side a sealed box, is a variable resistor. this resistor slides in a circular motion as the door is opened farther. as the electrical resistance changes the computer makes minor adjustments to compensate for timing and fuel. One mre thing if you guys are sooo worried about me running rich at WOT. I could set up a small.... kind of shock absorber to slow the "opening of the door" but as of yet I have noticed no ill affect on mixture Hell, you want cheap, go with and SDS or any of the "cheaper" stand-alone system available for under $1,000... I'd recommend you do your homework before making wrongful assumptions at pointed out above.  You're trying to tinker with something you don't have the proper knowledge of?  That always leads to no where... -Ted |
Mazdaspeed7 is working on one, but I beleive has hit a wall with the power supply... I am not sure though.
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OK, I just don't know if this MAF conversion is possible without some real professional development.
Have you ever watched the AFM sensor when you touch the throttle off idle? It jumps in very far for a second when you first touch the throttle, then returns, even thugh you still have the throttle open. This is due the engine vacuum being initially depleted when the butterflies open , then resuming to normal engine intake. The ECU takes advantage of this natural process to use it as the "accelerator pump" that carbs have. The engine needs that little enrichening jump. The computer is programmed like that. I am not sure if the hot-wire sensor can react quickly enough to accomodate that- and if it can't then a computer in-line with the AFM signal needs to be built to simulate it. |
Most EFI's use the TPS to sense the need for extra fuel when you stomp the gas. Hot wire reacts pretty fast, but the issue I have is how linear the signal is vs. flow rate. I am considering one for a turbo VW aircooled bug at the moment. I hate carbs, and I hate flappers too. If the MAF was linear, I'd use that vs speed density. It just seems more correct to me.
-Les |
I think the best solution would be a software one- like the signal interpreter software on the board of a wideband o2 sensor display.
If someone could make a board that would simply convert the hot wire signal, to the proper cooresponding MAF output voltage to the ECU. Just install the hot-wire, the converter, and go. Enough with linkages, and crap- all these baind-aid solutions. But like I said, that needs more or less profesional development. Cause I don't know how!! |
This just strikes me as a lot of hard work for very little gain. I applaud you for thinking laterally to get around a problem but I don't think you've got enough of a grasp on how EFI works to overcome the many problems this conversion would cause. The power gained by removing the restriction caused by the AFM would be lost because of the screwed up fuelling. The obvious downfall of your design is that airflow into the engine is not linearly related to throttle position. That's it. Some systems can run off throttle position and RPM only but that's only on racecars that run mainly WOT, and would be totally unsuitable for a road car.
If you're dead set on eleminating the AFM but not the stock ECU, consider the HKS VPC, but in terms of $/hp an aftermarket ECU is still better. BTW, for every one knocking air flow meters, remember the ECU needs to know how much air is going into the engine, and the only way to do this is with an AFM. You can only estimate air flow from manifold pressure or throttle position, which is why most cars have use an AFM. A manufacturer has to worry about economy and emissions, not just peak power, so an accurate measure of air flow is required. The ideal setup would be a hot wire type AFM capable of flowing large amounts of air without causing a restiction. |
yes I do understand how efi works. I was over simplifying for the sake of the forum.
I may have been a little off on how this particular EFI system works, but this IS how most work. there may be slight differences, but the things work about the same. when open loop happens is nearly irrelivant, not completly, but nearly. the MAF is used for tuning and fuel you were right just not completly. so was I. it adjusts how much fuel based on how much air. this is basic tuning. A big thanks to every one that has offered advice. I did consider the wok involved befor hand. to date I have spen about 30 minutes procurring a used MAF, another cutting ut up to eliminate the flapper and still have the shaft. 15 minutes fitting it to a "kit box" from radio shack. and about an hour figuring out where the cable an lever need to be on the shaft so that is opens in parallel with the unit that is still stock. this will be greatly reduced since now I know and all I have to do is measure and write it down. ( i need to remember to measure) Any way I am going to order a variable fuel reg. next week. I will do som research to find one that I like. at an affordible price of course. |
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