DIY_EFI Digest Saturday, 16 March 1996 Volume 01 : Number 078 In this issue: Re: thermocouples [none] [none] Re: thermocouples Re: Encoder BS ENGINES See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: scicior@xxx.com (Steve Ciciora) Date: Fri, 15 Mar 1996 07:37:40 -0700 Subject: Re: thermocouples > I use the AD594 device to compensate and linearize thermocouples. > Just because the specs say something like "output is 10mV/Deg C" dosn't mean that these devices linerize themocouples. I don't think they do. - -Steven Ciciora > Does anyone have experience multiplexing in front of one? > > ----------------------------------------------- > jac@xxx.us > john carroll > > ------------------------------ From: WERNER_HAUSSMANN@xxx.com Date: Fri, 15 Mar 96 08:25:36 -0700 Subject: [none] Hi Orin The Bosch trottle position comes in both rotations. The Weber trottle body used on the Renault is the opposite rotation of the Ford trottle body as you know. The German cars (BMW) have the trottle body switches in the other directioin. Even so I was not happy with the fit, and I prefer to sense the manifold pressure to go to enrichment. The manifold pressure switch was used on Volvo's and on late Renaults using the LU-jetronic. But I still don't know a PN or where I can get one. Nor do I know at what pressure the switch closes/opens. The trottle body injector I use for the MGB (1800cc) is a E43-AC, ~752cc/min @xxx. It's about 4 times the injector flow of the port injectors for the Renault i18 or Fuego. The MGB engine and manifold can't take the lean running condition of the design value for the L-Jetronic. It therefore idled poorly (too lean) and hesitated when accelerating. I was able to overcome all of that by loosening the spring of the air flow meter by two notches, and by increasing the fuel pressure to 17 lb/squin. The key for good idle and operation is to run at the design mixture level the engine and manifold. This means no lamda (O2) sensor. Decreasing the spring force on the air meter decreases the maximum air measuring capability (runs lean at wide open trottle), so I also toyed with the calibration of the air meter. Depending on the air meter you can increase the fuel flow by changing one of the reference resistor values in the air meter (thats the resistor that feeds the potentiometer). The last and best way is to modify the computer to put out more fuel by a fixed percent across the whole range of operation. This is a little more tricky and beyond my ability to describe here. With any of the changes above, the car ran good and idled just fine cold or hot. I never had any cold start problem with the system. It starts easily with at -10F. You might check the cold start injector circuit, and be sure that the cold start injector is designed for the fuel pressure you are using. You need a low pressure injector. You can get one from the old VW's that use trottle body injection. I really like the Electromotive unit. Did you program it, or are you using the program that comes with it. Werner - --------------------------------------------------------- Subject: Re: L-jetronic Werner, Did you ever find out what the flow specs. are for the Ford (Bosch) injectors are??? I remember you said that you were having trouble with the system running lean on the "B"..I had the same problem when I tried your approach and never could get the thing to run as I would like. I also never overcame the cold start problems..You know, on very cold days it would idle very rough...Warm days ok, but cold days really bad. I have switched over to the Electromotive TEC II and it runs fine, although a little lean, but the system is very expensive and defeated the real purpose...A cheap replacement for the SU's or Zenith carbs...Let me know how you're making out ... Orin Hi Werner, I also had a hard time fitting a switch to the Ford throttle body and what I finally used were 2 micro switches on a bracket that I mounted where the idle air motor had been mounted. I never did like this approach. I looked into using the Bosch switch but as you know it's rotation is backwards and I never really came up with a good solution. The vacuum switch sounds like a good alternative. You never gave me the injector part number. You said you thought it was green color coded but when I talked to you, you couldn't remember. If you have time, please look it up and send it to me. If you know it's flow rate, please let me know that also. I also upped the fuel pressure to 17 or 18 PSIG and it did help a lot. You didn't say how you had overcomed the poor idle when cold problem. What have you done there?? Orin ------------------------------ From: WERNER_HAUSSMANN@xxx.com Date: Fri, 15 Mar 96 08:51:14 -0700 Subject: [none] Item Subject: cc:Mail Text Hi James The L-Jetronic uses an air meter with a flap. Yes it is restrictive. My original plan was to get this system going. Put in the fuel delivery system, get the injector(s) working and just prove the feasabilty. Then I was going to move up to the fancy $1800 Electromotive TEC II system. It uses a Mass Air Flow meter. Anyway the L-jetronic seems to work well enough to satisfy me, but I am still itching to add a turbo, and for that I want to control the ignition and will probably need the Electomotive system. A later Bosch system called the LH-Jetronic was digital and used a MAF meter. This was used in the '80s on Volvo up to '88. The L series Bosch systems are very nice because they are so easy to adapt. They only use the ingnition coil signal. No fancy crank sensors are needed. Anyway the problem for hot rodders are that these systems were used mainly in relatively small engines except for Jaguar, BMW and the like. And for the price of those in a junk yard, you might as well use Electromotive systems. The L-Jetronics uses only the air meter signal (air temperature and Air flow, together they give air volume), the water temperature and the ignition (rpm and crank position) to calculate Fuel. Trottle position is not used except to enrich at 2/3 trottle and to cut out the fuel above 1500 rpm when at closed trottle. This is actually very accurate and very simple. The air meter gives out a voltage that changes logorithmically with the air flow. It also has a thermistor for air temperature. To use the L-Jetronic system You will have to find a car with about the same size engine as the one you want to adapt. This is most likely to be your biggest obstacle. Of course you could run two systems, one on each side of a V8. How big an engine are you using anyway? My suggestion is that you should try to get something working, and then keep working to make it better. You can always try to get started with the Holley trottle body. Used ones are often for sale by someone who has upgraded. This way you will get the basics in place like the fuel delivery, the high pressure pump, etc. For more information get the Probst book on Bosch systems. Good Luck Werner ------------------------------ From: "David M Parrish" Date: Fri, 15 Mar 1996 12:56:09 +0000 Subject: Re: thermocouples > > I use the AD594 device to compensate and linearize thermocouples. > > > Just because the specs say something like "output is 10mV/Deg C" dosn't > mean that these devices linerize themocouples. I don't think they do. Nope. It amplifies and provides an ice reference, but doesn't do linearization. The polynomials to linearize the output of all the common thermocouples are well known and I've attached a small Pascal program I used for demonstration with the AD595 and a K thermocouple. You can use the polynomial in the controller firmware, or better yet, use this program to generate a look-up table. > > Does anyone have experience multiplexing in front of one? I may be a bit banger, but I know that mux'ing millivolt signals can be tricky. Any analog guru's out there? Program Kcouple; { AD595 outputV= (K voltage + 11uV)*247.3 K volt = outV/247.3 - 11uV K volt =4.043672e-5*digits - 1.1e-5 (10.24Vref) K volt =2.9631204e-5*digits - 1.1e-5 (15.00Vref) K volt =1.9754136e-5*digits - 1.1e-5 (15.00Vref, 2/3 gain) EGT max = 954oC (1750oF) K thermocouple: 0 to 1370 oC +/- 0.7 oC } var x : integer; v, T : double; Begin writeln(' x K mV T oC T oF'); { NNNN NN.NNNN NNNN.NNN NNNN NNNN.NNN NNNN } for x:=0 to 2047 do begin { v:= 4.043672e-5*x - 1.1e-5;} v:= 1.9754136e-5*x - 1.1e-5; T:= 0.226584602 + v*(24152.10900 + v*(67233.4248 + v*(2210340.682 + v*(-860963914.9 + v*(4.83506e10 + v*(-1.18452e12 + v*(1.38690e13 + v*(-6.33708e13)))))))); writeln(x:4,(v*1000):8:4,T:9:3,T:5:0,((T*9/5)+32):9:3,((T*9/5)+32):5:0); end; End. - --- David Parrish Hey, don't laugh. I taught myself Pascal with the original Wirth compiler. ------------------------------ From: mike@xxx.uk (Mike Rigby-Jones) Date: Sat, 16 Mar 1996 01:12:05 GMT Subject: Re: Encoder On Wed, 13 Mar 1996 23:52:04 GMT, you wrote: > > 1:) Turbocharger : I have already designed most the system, but for my >application efficiency not power is important. > 2:) Replace the crackshaft with a high efficiency crack. (I have one changed >the horse power from 3.5 to 3.9!!!) These are cool things smaller with larger >counterwieghts. They provide a smother ride too! > 3:) Fuel injection. Especially with a turbocharger could get a briggs in the >stratosphere as far as RPM goes. > 4:) A new piston : You'd melt a standard piston real quick, they're a low >grade aluminum, cheap as hell. Replacing it with a Stainless steel piston would >make it nearly flame proof. > 5:) A new connecting rod. Most are made of aluminum to, and would shear with >no problem at that speed and Horse power. > 6:) Increased compression ratio. A briggs and startton has a compression >ratio of 4.7:1 max at the factory. I like 10:1 or 11:1 much better. > 7:) Change Cam profile to a design more conducive to fuel injection. >(A lot of these changes I've considered to do with my Super Mileage Vehicle) > Walla: A Briggs that runs at Å10HP, and 7-8000 RPM. All from a 3.5HP I'm >deranged, it's sick that I know so much about such a shitty old engine! > > Jim Staff > Hey its good to know that some sad people still play with these things. I had several of these engines to play with some years back. I ported one and put larger valves in and raised the compression as much as possible, also got rid of the so called 'carb' and put on one from a Honda 125 OHC. Don't know what sort of power it got but the kart it was in went pretty well!!! I think you would have a major problem getting 10:1 compression from the beast. The area needed for the valves o move up and down pretty much limits the max compression especially if you put big valves in. Stainless steel piston???? Bit heavy I would have thought? Why not graft in a crank and piston from said Honda?? ( BTW most pistons tend to be flame proof!!!!) This would solve the con rod problem as well (I have seen several of these snap even when the engine was powering a mower) The flywheel is also a little suspect for high rpms. In fact its lethal so get rid of it or at least strengthen it in some way. As for a turbo, well it'd have to be VERY small just to be turned over by a B&S let alone produce boost. I managed to get some kind of vacuum pump from a old milking machine which could be used in reverse as a pressure pump. It was a vane device and had a fair displacement so I was toying with the idea of supercharging but never really got it finished. I think that would be the way to go instead of turbos. cheers Mike RJ ------------------------------ From: "Clinton L. Corbin : Backgrind/Gold : Pager 0544" Date: Fri, 15 Mar 96 19:49:23 PST Subject: BS ENGINES >> 4:) A new piston : You'd melt a standard piston real quick, they're a low >>grade aluminum, cheap as hell. Replacing it with a Stainless steel piston would >>make it nearly flame proof. > >Stainless steel piston???? Bit heavy I would have thought? Why not >graft in a crank and piston from said Honda?? ( BTW most pistons tend >to be flame proof!!!!) This would solve the con rod problem as well >(I have seen several of these snap even when the engine was powering a >mower) Aluminum pistons being flame proof?! Aluminum melts at around 1100F (used to work in an aluminum foundry). Flame temp inside an IC engine is around 1600F. At 1600F, aluminum is a really pretty BRIGHT orange liquid! The only thing that saves the piston is the limited time that the fuel/air is burning (relative to the total time) and the heat transfer to the cylinder. If you increase the amount of energy being generated in the combustion chamber (say by turbocharging or just increasing the breathing of the engine) enough, the piston will not be able to dump the extra energy to the cylinder and bam, you melt a nice hole in the piston. BTW, molten aluminum is not the best lube in the world! All in all, aluminum is not the best material for a piston. Unfortunately, a really great material (Carbon/Carbon Composites) costs about fifty times as much! Maybe someday we will all have pistons that CANNOT melt. Clint ccorbin@xxx.com ------------------------------ End of DIY_EFI Digest V1 #78 **************************** 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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