DIY_EFI Digest Saturday, 3 February 1996 Volume 01 : Number 030 In this issue: re: Re: Sensor Questions? Re: Re: Sensor Questions? Holley ProJection 4Di ? Re: Sensor Questions? re: Re: Sensor Questions? Re: Bosch Mono-Jetronic Re: Engine codes Re: Holley ProJection 4Di ? Re: Bosch Mono-Jetronic Re: re: Re: Sensor Questions? Re: re: Re: Sensor Questions? Re: Bosch Mono-Jetronic re: Re: Sensor Questions? Re: re: Re: Sensor Questions? Re: Engine codes re: Re: Sensor Questions? MAF sensor types (was re: Re: Sensor Questions?) re: Re: Sensor Questions? RE: re: Re: Sensor Questions? Re: BOSCH MAF Sensors See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: ehernan3@xxx.com (Edward Hernandez (R)) Date: Fri, 2 Feb 1996 08:04:12 +0500 Subject: re: Re: Sensor Questions? "The solution to this is the MAF (mass air flow) sensor. Instead of measuring the percentage of maximum flow, it measures the actual amount of air that enters the engine. After some corrections for air temperature (simple) the ECM can then calculate the required amount of fuel." Mass Air measurement, at least with a hot wire, does not require temperature correction. That's the beauty of hot wire MAF systems: they measure mass flow rate of air, which is not dependent on temperature. If you measure volume flow rate of air(like Karmen vortex devices), you must measure the air's pressure and temperature before you can calulate it's density and therefore it's mass. That's why such devices have ACT(air charge temp) and BAP(barometric absolute pressure) built into them. Hot wire MAFs do not have these additional sensors. ------------------------------ From: ehernan3@xxx.com (Edward Hernandez (R)) Date: Fri, 2 Feb 1996 08:29:10 +0500 Subject: Re: Re: Sensor Questions? "The airflow into the ports per revolution is almost directly related to the manifold pressure for most engines with a relatively flat volumetric efficiency characteristic." Most engines do not have a relatively flat volumetric efficiency curve, especially those with tuned induction systems. Virtually all mulitport injected systems utilize tuned induction systems. Only TBI systems, which are essentially fancy carburetors, do not use tuned intakes due to problems with wet flow. "FWIW, I installed an aftermarket speed-density system on the weekend and was able to tune the efi and distributorless ignition system to a driveable state within two minutes." Good for you. This is an excellent example of the fact that gasoline engines can run A/F ratio anywhere from 10.5:1 to 15:1(or higher, depending on the combustion chamber) and still be called drivable. That's another way of saying you could get your fueling wrong by about a 30% and the engine will still run. Same goes for spark timing. You can be way off before you would judge a vehicle as not being drivable. The point is, you cannot maintain a specific A/F ratio without knowing how much air the engine is consuming or without an accurate, wide range O2 sensor. This is a big point, since the difference between being drivable and passing EPA emissions fuel ecomony standard is enormous for the OEMs. DIYers need not meet these standards. ------------------------------ From: ken@xxx.no (Ken-Arne Jensen) Date: Fri, 2 Feb 1996 15:23:44 +0100 (MET) Subject: Holley ProJection 4Di ? Hi 2.2.96 This may not be directly within the primary topics of this list, but related: Lately Holley released a digital programmable TBI system ProJection 4Di, which have MAP input sensor and IAC (Idle Air Control) motor. It also control ignition timing, and may be attached to a knock sensor. The VE (Volumetric Efficiency) map, ignition timing and rev limit are programmable from a PC. >From the information Holley have given me so far, this system seems to be a bit better than the old analog controller. The questions I have are: 1) Have anyone out there had any hand-on experience with this particular system? I am especially interested in views around tuneability and fuel economy. Also information around which CPU they use are valuable. 2) Holley claims the system to be "Sequential", what does that mean for a TBI system with only 4 injectors? Thanks for any help! //// Ken-Arne Jensen // E-Mail: ken@xxx.no / /// Computer Science Department // URL: http://www.cs.uit.no/~ken // // University of Tromsų // Phone: +47-776-44042 /// / N-9000 Tromsų, NORWAY // Fax: 44054 (barcode="ken@xxx.ui") //// ------------------------------ From: atsakiri@xxx.com Date: Fri, 02 Feb 96 09:28:15 -0500 Subject: Re: Sensor Questions? > This is a big point, since the difference between being drivable > and passing EPA emissions fuel ecomony standard is enormous for > the OEMs. I second that. So true. Anthony Tsakiris - --------------------------------------------------------------------------- The opinions expressed are my own and not necessarily those of my employer. ------------------------------ From: ehernan3@xxx.com (Edward Hernandez (R)) Date: Fri, 2 Feb 1996 09:38:45 +0500 Subject: re: Re: Sensor Questions? "Oh man, now I'm confused. MAF isn't good as the basis for fuel injection alone, since the amount of air past the MAF sensor isn't necessarily the amount of air into the engine. Remember the plenum stores air, so a sudden increase in the amount of required air will draw a vacuum on the plenum before the MAF actually sees the increase in airflow." You are absolutely right. That's whys carburetors had pump shots. EFI systems(even SD based) have acceleration enrichment strategies that are a function of throttle transients. That's one of the main reasons for using a TPS(throttle position sensor) on hot wire MAF engines. SD systems are NOT "perfectly capable" of learning about engine mods which affect volumetric efficiency and never will be because of the way they work. You have to teach them. Part throttle learning from O2 sensors doesn't work "perfectly" because engine pumping losses change dramatically with throttle angle. Vol eff curves at part throttle bear no resemblance to WOT vol eff(In fact, there is no such thing as "part throttle vol eff"). Properly designed MAF systems learn by themselves. You just can't beat measuring air consumption directly as opposed to guessing and inferring it. I'm not discarding SD based systems outright. They work great if you have the time to map a system out, and they are less expensive. It just seemed to me that they have recently been touted as being capable of doing things things they simply cannot do as well as a MAF system. If you have the time and facilities for mapping and engine's air consumption, good for you. Most of us do not. ------------------------------ From: ehernan3@xxx.com (Edward Hernandez (R)) Date: Fri, 2 Feb 1996 09:38:44 +0500 Subject: Re: Bosch Mono-Jetronic "I always assumed that manufacturers went open loop to run richer (more power) at WOT. Anyone know for sure?" "Yes, it runs rich at WOT to obtain the best power. I'm not sure if running *exactly* stochiometric at WOT is bad for the engine..." Three reasons we run rich at WOT: 1) Power. Unless you have an ideal, perfectly vaporized mixure, running rich always makes more power than running stoich. Basically, there isn't enough time to burn droplets, and some fuel goes unburned, leaving "excess air" available. Running rich is a way of providing more droplets for this excess air that's available to burn it. Perfect mixtures have no droplets; all air and fuel is completely utilized during combustion, and therefore running rich would actually decrease power. But we can't prepare perfect mixtures yet... 2) Engine durability. Again, without ideal mixture preparation, running stoich at WOT is like running lean: longer burn rates, which raises combustion chamber temperatures, melting pistons, eroding plug electrodes and burning exhaust valves. Higher temps can lead to detonation(which can break ring lands) and can eventually lead to preignition(not the same as detonation; it's much worse). 3) Catalyst durability. Running stoich at WOT causes high cat temperatures for reasons cited above. High cat temperatures degrades their effectiveness over time, and we need them to last a really long time. Running rich drops exhaust temps and help the cats last longer. High mileage recalls are no fun for OEMs. Yes, rumors of EPA mandated WOT A/F ratios has OEMs worried, especially certain Asian manufactures who run extremely rich at WOT. ------------------------------ From: m_mcdonald@xxx.com Date: Fri, 2 Feb 96 09:46:52 EST Subject: Re: Engine codes >> At 12:43 AM 2/1/96 EST, Will McGonegal wrote: >> ... if anyone is still interested in trying to figure out the port >> themselves, I can pass along the information needed to set up the baud rate >> and the circuitry used in the RS232 interface. > Yes, I would be very interested in geting any information that might help me > extract data from my GM TPI ECM. Since I'm not interested in extracting > data from all GM computers ever made, this MIGHT be just what the doctor > ordered. > Thanks a million, > George M. Dailey gmd@xxx.com Rinda Technologies in Chicago has an excellent hardware/software package named DIACOM. Its basic price for a wide variety of GM and Chrysler (but not Ford :-( ) cars is $300-$400. The package connects a GM car's ALDL to an inexpensive laptop PC and displays all kinds of information from the car's serial data stream. Rinda is in Chicago, Illinois and their toll-free number is 800-888-4146. They charge $5.00 for a demonstration diskette and advertising. You can obtain this demonstration software on CompuServe. Begin with GO AUTO or GO AUTOS or GO CAR or GO CARS and get to the FOR TECHS ONLY forum. Look for files whose keywords include DIACOM -- there's probably only one of them. Download the file and run it on your PC. Unless you're a computer hacker who understands parallel port programming and data communication protocols, you're much better off buying the package from Rinda Technologies. I have no connection with this company other than being impressed by their demonstration software. Marll McDonald KB1AGM m_mcdonald@xxx.com ------------------------------ From: "Robert Gallant" Date: Fri, 2 Feb 96 10:35:36 EST Subject: Re: Holley ProJection 4Di ? > Lately Holley released a digital programmable TBI system ProJection 4Di, > 1) Have anyone out there had any hand-on experience with this particular > system? > I am especially interested in views around tuneability and fuel economy. > Also information around which CPU they use are valuable. I have one on my supercharged Rx7. It is VERY tunable. So much so, that I am looking to put the car on a dyno to tune it. But my installation isn't typical. Holley supplies some base maps for V8 cars. > 2) Holley claims the system to be "Sequential", what does that mean for > a TBI system with only 4 injectors? I'm using the 700 cfm throttlebody with four 65 lb/hr injectors. There is one injector firing per ignition pulse. So each injector fires every fourth ignition pulse. I put some of the maps on my web page. If anyone is interested Email back to me and I'll give them the address. Later Rob gallant@xxx.mil ------------------------------ From: MSargent@xxx. Sargent) Date: Fri, 2 Feb 1996 11:06:04 -0500 Subject: Re: Bosch Mono-Jetronic > Check your linkage! The reason I get more power when I back off, is that I have added a header, 3" exhaust, and K&N filter, so the engine breathes a lot easier than it did when calibrated at the factory. When not at WOT, the ECM adapts for the new flow, but at WOT it goes to the factory closed loop settings, which will be too lean. +--------------------------------------------------------------------------+ | Michael F. Sargent | Net: msargent@xxx.com | Phone: 1(613)721-0902 | | Gallium Software Inc.| | FAX: 1(613)721-1278 | +--------------------------------------------------------------------------+ ------------------------------ From: "Brian Warburton, c/o Turbo Systems Ltd" Date: Fri, 02 Feb 1996 16:13:15 Subject: Re: re: Re: Sensor Questions? > > No, not unless the # of BLM cells (or adaptive locations) is equal to the > number of possible fuel map cells under those conditions .. so that EVERY > point in the fuel map is compensated .. to it's needed adjustment > > Jim > Not entirely sure why you would need the same number of adaptive (BLM) cells as main fuel map cells, I think you'll find that a bit of interpolation here and there will resolve any differences. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Brian Warburton, "Still searching for the perfect curve....." email: bwarb@xxx.net Advanced Automotive Electronics Ltd, Van-Nuys House, Scotlands Drive, Farnham Common, England. SL2-3ES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ------------------------------ From: "Brian Warburton, c/o Turbo Systems Ltd" Date: Fri, 02 Feb 1996 16:13:15 Subject: Re: re: Re: Sensor Questions? > > No, not unless the # of BLM cells (or adaptive locations) is equal to the > number of possible fuel map cells under those conditions .. so that EVERY > point in the fuel map is compensated .. to it's needed adjustment > > Jim > Not entirely sure why you would need the same number of adaptive (BLM) cells as main fuel map cells, I think you'll find that a bit of interpolation here and there will resolve any differences. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Brian Warburton, "Still searching for the perfect curve....." email: bwarb@xxx.net Advanced Automotive Electronics Ltd, Van-Nuys House, Scotlands Drive, Farnham Common, England. SL2-3ES ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ------------------------------ From: Tommy.Palm@xxx.se Date: Fri, 2 Feb 1996 13:04:46 -0500 Subject: Re: Bosch Mono-Jetronic >>Land Shark wrote: and Wouter de Waal: >'nother thing. This system can "limp home" if _everything_ is bust. I.e= =2E all >the sensors can be out (except the rpm info from the ignition) and >apparently you'll still get home. > >Sounds like black magic to me :-) > I drove my SAAB 9000Turbo for weeks w/o my MAF when i was lending the MA= F to a friend. A little jumpy idle and low mpg when cruising slow, fuellack fel= t at = >150km/h, no clogged sparkpluggs. The limphome system just gives a const= ant pulswith that is coolanttemp dependenant and triggers every 2 ignintion = pulse. I have used equal system w/ one extra TBI inj as limp home for all my DI= Y-EFI. It covers all errors as long as i still have fuelpress. No magic. Think = of diesel engines...thats more magic. Tommy = ------------------------------ From: tom sparks Date: Fri, 2 Feb 1996 12:28:56 -0600 Subject: re: Re: Sensor Questions? At 09:38 AM 2/2/96 +0500, you wrote: You just can't beat measuring air consumption directly as opposed to guessing and inferring it. > I'm not discarding SD based systems outright. They work great if you have the time to map a system out, and they are less expensive. It just seemed to me that they have recently been touted as being capable of doing things things they simply cannot do as well as a MAF system. If you have the time and facilities for mapping and engine's air consumption, good for you. Most of us do not. > > OK, so the hot wire system seems to be the simple solution for measuring air consumption by an engine. If a person wanted to experiment with such a device, could you recommend an OEM part to start with? Also, I have a table somewhere of various OEM injectors and their lbs./hour ratings. Is there a similar list somewhere of the various OEM hotwire MAFs and their primary operating ranges? If anyone wants to send me any information about OEM parts that might prove useful to DIY-EFI people out there, (not just MAFs but things like inductive pick-ups, driver circuits, injectors, throttle bodies, etc.) I'll compile them and post them back to the list for the convenience of the group. Part numbers would be best but if you have just the applications, that might also work. Be as specific as possible with the application information, you know how parts guys are sticklers for specifics. Best Regards, Tom Sparks ------------------------------ From: Land Shark Date: Fri, 2 Feb 1996 12:00:59 -0700 (MST) Subject: Re: re: Re: Sensor Questions? At 04:13 PM 2/2/96, you wrote: >Not entirely sure why you would need the same number of adaptive >(BLM) cells as main fuel map cells, I think you'll find that a bit >of interpolation here and there will resolve any differences. You need them because ... (tech weenie geek hat on!) 1) The relationship is a discrete function, of 2nd order to rpm and 1st to MAP (geek hat off) 2) Changing any accessory will very likely change said functions SHAPE from the stock shape ... and unless EACH point in the fueling map is countered by an individual correction, the "interpolation" will be off .. 3) Worst of all, since EGO feedback is off under higher loads/rpms and WOT, you'll never fill in those BLM cells anyway :( Jim ------------------------------ From: "George M. Dailey" Date: Fri, 2 Feb 1996 13:13:58 -0600 Subject: Re: Engine codes >>> At 12:43 AM 2/1/96 EST, Will McGonegal wrote: >>> ... if anyone is still interested in trying to figure out the port >>> themselves, I can pass along the information needed to set up the baud rate >>> and the circuitry used in the RS232 interface. > George M. Dailey gmd@xxx.com wrote: >> Yes, I would be very interested. At 09:46 AM 2/2/96 EST, Marll McDonald wrote: >Rinda Technologies in Chicago has an excellent hardware/software package >named DIACOM. Its basic price for a wide variety of GM and Chrysler >(but not Ford :-( ).... George's response was: Does Diacom have and any idea about their massive following? The latest J.C. Witney catalog #586k (inside cover page) has an Auto Xray XP240 scanner for $280 complete, no PC needed. The illustration shows a two line display (32 characters). Interface cables are available for GM (king of autos), Ford :-}, and that other car maker ... Chrysler for only $29 each. I do not own one, and I don't know anybody that owns one. I'd be willing to bet that it works as advertised. I neglected to tell you folks out in DIY FI land, what my true reason was for wanting to read ALDL data. Here's my confession. I have constructed a mid engine, rear wheel driven sports car from scratch. The engine is a '85 PFI 3.8L Buick V6. The plan is to transmit the ALDl data to a dedicated PC, peramanently mounted in the car and connected to a small VGA monitor. Software would convert the data to usefull information that would be displayed on the monitor. Boom, no additional instruments needed and a wealth of data on demand. The car (Bianca) was designed to house a PC. Think of her as a streached Lamborghini Contach with all the room and comfort of a full size '70's Olds. Data logging would also be utilized. The PC would also control some BODY functions. It's not that I'm to cheap to by Diacom or XP240 (I just might by the XP240) but, if I'm going to make this work I need to get some type of simple PC to ALDL communication established. Any help on the software end would be much needed. thanks' George M. Dailey gmd@xxx.com ------------------------------ From: "David M Parrish" Date: Fri, 2 Feb 1996 15:57:36 +0000 Subject: re: Re: Sensor Questions? > From: tom sparks > OK, so the hot wire system seems to be the simple solution for measuring air > consumption by an engine. If a person wanted to experiment with such a > device, could you recommend an OEM part to start with? A list of various cars that have various types of MAF censors, (Especially the hot-whatever types.) would be very useful when junk-yard prospecting. If you really want to experiment, there were articles in both EDN and Electronic Design of air flow meters using common miniature light bulbs with the glass removed as the hot wire sensing element. You could build either one for less than $15. - --- David Parrish ------------------------------ From: "Zublin, Bryan (SD-MS)" Date: Fri, 02 Feb 1996 14:11:00 -0800 (PST) Subject: MAF sensor types (was re: Re: Sensor Questions?) > OK, so the hot wire system seems to be the simple solution for measuring air > consumption by an engine. If a person wanted to experiment with such a > device, could you recommend an OEM part to start with? It would be great if we had some hard data on the web site regarding the calibration curves of various MAF sensors. Until then, maybe start a general info section. Here's my input (off the top of my head). Most of this info I have read in the SAE publications from the last 15 years. I paid a bunch of money for the back issues... Type #1 - Bosch I think the first ones to develop a MAF sensor for auto applications were Bosch. It consists of a thin platinum wire in the full air flow stream. The output is analog with a non-linear characteristic. To clean the wire of dirt build up, a "burnoff" voltage is sent to the wire to heat it up red hot for a couple of seconds. This is done after the engine is turned off. This type of MAF is common on many European cars. Type #2 - Hitachi Bypass (analog output) Hitachi later developed a MAF that measures a portion of the entire air flow ("bypass type"). The advantages include less dirt build up and damage immunity from intake backfiring. A disadvantage is that the reverse air flow is not measured, so if there is a lot of pulsation at the meter, it will cause errors (?). The hot wire (or hot film) does not require a "burn off" over its lifetime. The output is analog and non-linear like the Bosch type. This type is used on many Ford cars, including the Mustang 5.0L engine (models 1987 up). It can handle *at least* 210 hp. Others have mentioned that it can handle up to 300 hp in stock form, and many speed shops sell upgraded units that can flow much more. The last time I checked with Ford, this sensor cost $150. This was the cheapest (new) MAF that I could find. Other types were $300 or more. Type #3 - Hitachi Bypass (digital PWM output) One of the other Japanese manufacturers (Mitsubishi? Hitachi?) wrote a SAE paper on a MAF that has a pulse width modulated (PWM) digital output. The sensor was the same (hot wire), but the electronics were run in the switching mode. Advantages include lower power dissipation, simple interface to the ECU (no analog to digital converter required, just measure the duty cycle), and less susceptible to electrical interference (think of FM radio compared to AM radio). I don't know which cars have this type. I assume that the pulse width output will be non-linear, the same characteristic of the analog output types (#1 and #2). Type #4 ??? - Karman Vortex (is this really a MAF?) Another type of air flow sensor is the "Karman Vortex" type, but I'm not sure if this is a *true* mass air flow meter (ie. no compensation needed for air temp or altitude). Apparently, these are used in the Mitsubishi's, and have a digital output that varies *linearly* with increasing air flow (note that the type #3 discussed above varies the duty cycle, with fixed frequency). The Karman Vortex type is also used in the Toyota Supra Turbo, from years 1988 thru 1991 (?). I'm not sure what the newer Supras use. It's interesting to note that Toyota used this type only in the Supra Turbo, when all of their other cars sold in the US with EFI used the standard trap door type. Why? Here is some more info on the one used in Mitsubishi's, quoting Peter Wales of Superchips: "The Karman (how do you spell that?) Vortex system used in the Mitsubishis is very linear. I tried to find a limit on it by driving around with it stuck out of the window and I met no limit (broke a few speed limits though). "The Starion air mass meter was fitted to every Starion and Conquest ever made anywhere in the world from 83 to whenever they stopped. I believe a lot of other Mitsubish turbo cars were fitted with it as well, all from the same era. In a junk yard you need to remove the whole airbox and disconnect it from the loom. I believe the air box is fixed with 2 bolts through the fender wall. "The air mass meter will give out a train of pulses which increases in speed as more air is drawn though it. In theory each certain amount of air requires a certain amount of fuel, so you count the number of pulses and give a squirt from the injector. Then it doesn't matter what the engine is doing, if it is using air, it is getting the mixture in the correct proportions. This will run the car fine." Bryan Zublin bzublin@xxx.com ------------------------------ From: "Zublin, Bryan (SD-MS)" Date: Fri, 02 Feb 1996 14:23:00 -0800 (PST) Subject: re: Re: Sensor Questions? >If you really want to experiment, there were articles in both EDN and >Electronic Design of air flow meters using common miniature light bulbs >with the glass removed as the hot wire sensing element. You could build >either one for less than $15. Wow, this is taking diy to the extreme. I would recommend using available MAFs from the OEMs, they have already worked out all of the accuracy, durability and reliability issues. IMHO. Bryan Zublin bzublin@xxx.com ------------------------------ From: "Clinton L. Corbin" Date: Fri, 2 Feb 96 19:35:58 PST Subject: RE: re: Re: Sensor Questions? >"Oh man, now I'm confused. MAF isn't good as the basis for fuel injection >alone, since the amount of air past the MAF sensor isn't necessarily the >amount of air into the engine. Remember the plenum stores air, so a sudden >increase in the amount of required air will draw a vacuum on the plenum before >the MAF actually sees the increase in airflow." Quick question: what exactly is going to cause this "sudden increase in the amount of required air" that is going to draw a vacuum? About the only thing that I can think of would be going down a steep hill and then closing the throttle. At this point, you need a leaner mixture anyway. While air does have mass, this will primarily cause a delay from when you open the throttle. >You are absolutely right. That's whys carburetors had pump shots. EFI systems >(even SD based) have acceleration enrichment strategies that are a function of >throttle transients. That's one of the main reasons for using a TPS(throttle >position sensor) on hot wire MAF engines. SD systems are NOT "perfectly >capable" of learning about engine mods which affect volumetric efficiency and >never will be because of the way they work. You have to teach them. Part >throttle learning from O2 sensors doesn't work "perfect Definitely agree on the need for an acceleration enrichment. And the need for a TPS sensor. Only a do believe that both MAF (mass air flow) and SD (speed, density) systems need them. >I'm not discarding SD based systems outright. They work great if you have >the time to map a system out, and they are less expensive. It just seemed to >me that they have recently been touted as being capable of doing things things >they simply cannot do as well as a MAF system. If you have the time and >facilities for mapping and engine's air consumption, good for you. Most of us >do not. Just remember that a MAF system also has to be calibrated to the engine it is on. The MAF give out a voltage (or frequency) depending on how much air is going through it. It does not tell you "currently, there is x Kg/sec flowing through me". How long you need to keep the injectors open is also dependent on the size of the injectors (and the number). Both systems must be calibrated. But I do agree that the MAF system will take less time. Just my two cents worth, so all those in opposition, fire away! Clint ------------------------------ From: Land Shark Date: Fri, 02 Feb 1996 22:26:01 -0700 Subject: Re: BOSCH MAF Sensors At 14:11 2/2/96 -0800, you wrote: >Type #1 - Bosch Actually there are TWO types of Bosch MAF .. A) Hot WIRE Sensors (HWS) which require burnoff and are generally a pain in the butt top use! B) Hot Film Sensors (HFM) which only need 12v and gnd to produce a nice nifty signal as an f(Q) where Q=airmass in kg/hr I like B (the HFM) myself! Jim ------------------------------ End of DIY_EFI Digest V1 #30 **************************** To subscribe to DIY_EFI-Digest, send the command: subscribe diy_efi-digest in the body of a message to "Majordomo@xxx. 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