DIY_EFI Digest Sunday, September 12 1999 Volume 04 : Number 520 In this issue: Re: Wired foo Re: Bosch MAF for VAF swap Re: Bosch MAF for VAF See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- Date: Sat, 11 Sep 1999 13:47:32 -0700 (PDT) From: Orin Eman Subject: Re: Wired foo > On Sat, 11 Sep 1999, DIY_EFI Digest wrote: > > Naturally, the experts think it's too good to be true -- although they > > can't exactly say why. > I don't know why they can't. I can; it violates the Second Law of > Thermodynamics. Entropy has to increase. That engine decreases entropy > by converting heat energy into rotational energy. The engine has to > output entropy somewhere. You can convert heat energy into rotational energy easily enough... it's what you car engine does. There is a lot of heat energy to convert though. I suspect that there isn't enough heat energy in ambient air to drive it through their system and have any energy left over. In fact, I'd guess you would have to input energy. Imagine if it did work - a self-powered refrigerator! Orin. ------------------------------ Date: Sat, 11 Sep 1999 18:53:55 -0400 From: bjanesi@xxx.com Subject: Re: Bosch MAF for VAF swap Hi Alex- Thanks for the response. Although I have a basic understanding of electronics, I'm not an electrical design engineer, so this is probably a bit over my head. Tying the MAF output to the O2 sensor output does sound interesting though, but what about cold start-up when running open loop? I guess there would have to be a default setting for open loop. I know the Split Second Co. has a control box with 3 different pots; I believe one sets the base idle, one sets mid-range, and the 3rd sets voltage at maximum air-flow. Fine tuning is done primarily via observation of an O2 sensor meter, so it is a manual approach to what it sounds like you have done automatically with the adaptive feedback. Any chance you have a schematic on any of this? Any info would be appreciated. Thanks again, Brad (brad.anesi@xxx.com <--- use this address if sending attachments) - ---------------------------------------------------- Date: Sat, 11 Sep 1999 09:27:41 +0000 From: "Alex C. Peper" Subject: Re: Volvo/Saab Bosch MAF swap for VAF I made some controllers for Bosch Hot Wire and Bosch Vane with PIC 73 Used built in 8 bit converter and 10 bit PWM output direct connection on hot wire.( used voltage divider and opamp on 10 V. vane meter.) Was used as O2 sensor adaptive feed back control, with 12 point internal correction table. Also had prototype to load EEPROM values and rpm input. You could look into adjustable gain opamps and DAC's Alex ___________________________________________________________________ Get the Internet just the way you want it. Free software, free e-mail, and free Internet access for a month! Try Juno Web: http://dl.www.juno.com/dynoget/tagj. ------------------------------ Date: Sat, 11 Sep 1999 18:51:55 -0400 From: bjanesi@xxx.com Subject: Re: Bosch MAF for VAF Thanks for the input John- I think the problem is not so much knowing the flow, as it is correctly adjusting the hot-wire voltage output over a range of flow conditions to match what is normally delivered to the PCM by the stock VAF meter. Monitoring via an air-fuel (O2 sensor) meter, is probably a better way to correctly adjust this, but I suspect a single static adjustment will only provide a match at one flow setting, and not the entire range (but I don't yet have any specific data to back up that statement). FWIW, I do have an extra pressure transducer pulled from an APC-equipped Saab turbo. What year is your 900? Brad Anesi - ----------------------------------------- Date: Sat, 11 Sep 1999 09:35:41 -0700 From: "John Dammeyer" Subject: Measuring MAF Hi, I'll put in my two cents here. Don't know how clever you are with electronics but if you purchase a differential pressure transducer you can build a simple flow meter by measuring the difference in pressure at two points. Create a supply tube that has a restriction and measure the pressure at the restriction and the point before the restriction. (venturi in effect). As long as you know the temperature of the air flow and the size of the tubes you can calculate the airflow. Then, just use a DC powered fan with a variable power supply to push air through this pipe into the MAF sensor. Alternatively, you might be able to rent a hot wire anemometer from an air conditioning firm and if you place that in the air stream of your air supply you can also calibrate the MAF sensor. I'm willing to bet that once you get a few accurate set points you can probably extrapolate the entire curve. BTW. Thanks for the info on the SAAB. I have a 900 Turbo. Regards, John ___________________________________________________________________ Get the Internet just the way you want it. Free software, free e-mail, and free Internet access for a month! Try Juno Web: http://dl.www.juno.com/dynoget/tagj. ------------------------------ End of DIY_EFI Digest V4 #520 ***************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. A non-digest (direct mail) version of this list is also available; to subscribe to that instead, replace "diy_efi-digest" in the command above with "diy_efi".