DIY_EFI Digest Sunday, 25 August 1996 Volume 01 : Number 245 In this issue: Re: DIY_EFI Digest V1 #244 Re: DIY_EFI Digest V1 #244 Re: DIY_EFI MB 450 Djet Strain gages on the drive shaft for torque measurement See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- From: talltom Date: Sat, 24 Aug 1996 11:48:52 -0700 (PDT) Subject: Re: DIY_EFI Digest V1 #244 >------------------------------ > >From: rickydik@xxx.com (RD Rick) >Date: Sat, 24 Aug 1996 00:28:38 -0700 >Subject: Re: Djetronic EFI: was ZEV / REV > >Kalle wrote: > >>Are there any technical sources on the EFI systems used in older >>MB 450 engines, they have analog brain which is a Bosh unit I think >>and a friend of mine has asked if I can modify this to generate timed >>injection for the V8 as at the moment it is a proportional system with >>only 2 phases for all 8 injectors. I have to disagree. The bosch service manual claims that it is a timed injection system. Is there any point and do I just >>take the pulse width for the current revolution and delay the start >>until the correct injectors turn has come and then hold the injector >>open when the valve is open for the same time it would have done >anyway ? It pretty much does that as is. >>I was told that there were 2 pulses on each set of 4 injectors per rev >>(or was it one per 2 revs) is this right or is it a random >unsynchronised>dutycycle that just meters/proportions the fuel? You were ill advised. >I have the Bosch D Jetronic EFI on my two Porsche 914's, and also have >a tester for the Djet. It will test the Merc 450, but I have never >looked at a Mercedes, as I don't much like radiators and hoses and >waterpumps. The D stands for Druck, or pressure. The later Ljet is >for Luft, or air(flow). > >The Djet uses a Manfold Pressure sensor, which is a transformer with a >core that is pulled against a spring by vacuum. It also uses a pair of >trigger points located in the base of the distributor (dizzy to you in >SA). In the 4 cyl VW and Porsche, the trigger points start the >injection for each pair of cylinders on every other revolution. It >would fire four at a time in the V8. Not according to the bosch service manual. It sez that their are four injector circuits with 2 injectors on each, and specifys at what point the injectors begin their pulse in reference to valve opening. Maybe you were thinking of the system used on Cadillac V-8's, they work that way. There is apparently no real >advantage to squirting fuel toward an open valve, as they could have >done it and didn't. Actually they did do it, but several others haven't, and the diferences seem to be minimal. GM uses a batch fire setup while Ford uses sequential and there seems no great performance difference. >The Djet is the grandfather of EFI. It was patentd by Bendix in 1952 >after they reportedly stole it from some guy who developed it in his >garage. Bendix licensed it to Bosch in the sixties, at the request of >VW. Its first use was in the '68 Fastback/Squareback. > >As with all electronics of the era, it is primitive by today's >standards. However, it does an outstanding job in a stock engine. >I am working on mods to it so the hiperf engine in one of my 914 will >idle below 2000, and still get enough fuel at 6000. > >RD > 81 VW Vangon aircooled four with Ljet EFI > 76 Porsche 914 stock commuter with Djet > 73 Porsche 914 hiperf commuter with Djet > 46 Bellanca Cruisair with 165 hp Franklin (Aircooled Motors) engine > 34 Franklin Olympic sedan with 100 hp aircooled upright six > > Except for some boats and ships, all engines are aircooled anyhow. > Why bother with water? Because some of us would prefer do do something with our lives besides screw around rebuilding engines. My water cooled 54 Cornbinder eng. runs fine and has never been rebuilt. ------------------------------ From: talltom Date: Sat, 24 Aug 1996 11:48:56 -0700 (PDT) Subject: Re: DIY_EFI Digest V1 #244 >------------------------------ > >From: rickydik@xxx.com (RD Rick) >Date: Fri, 23 Aug 1996 23:30:52 -0700 >Subject: Re: Data Logging/Dynosores? With all the stuff about old truck parts, Dyno's, torque measurement, HP, and g-meters I would think that some of the electrical wizards here could use some of the hardware off of a 84 280/300zx Nippanzee. I believe the speedometer in these has a graph function that indicates torque, rpm. I'm not really sure, but if it's not torque or HP it sure looks like it ought to be. They also have a g-meter that's totally usless for anything real because it only goes -.5g to + .5g, but the system is there and exists, and I don't see why it couldn't be shuffled to work in the real world. With the info this could gather, ecu's could program themselves for best performance or least polution, and those could be set to owner preferences. This would eliminate thousands of truck parts dyno's..... ` ------------------------------ From: rickydik@xxx.com (RD Rick) Date: Sat, 24 Aug 1996 12:31:42 -0700 Subject: Re: DIY_EFI MB 450 Djet Talltom replied > >>From: rickydik@xxx.com (RD Rick) >>Date: Sat, 24 Aug 1996 00:28:38 -0700 >>Subject: Re: Djetronic EFI: was ZEV / REV >> >>Kalle wrote: >> >>>Are there any technical sources on the EFI systems used in older >>>MB 450 engines, they have analog brain which is a Bosh unit I think >>>and a friend of mine has asked if I can modify this to generate timed >>>injection for the V8 as at the moment it is a proportional system with>>>only 2 phases for all 8 injectors. > >I have to disagree. The bosch service manual claims that it is a timed >injection system. > > Is there any point and do I just >>>take the pulse width for the current revolution and delay the start >>>until the correct injectors turn has come and then hold the injector >>>open when the valve is open for the same time it would have done >>anyway ? > >It pretty much does that as is. > >>>I was told that there were 2 pulses on each set of 4 injectors per rev>>>(or was it one per 2 revs) is this right or is it a random >>unsynchronised>dutycycle that just meters/proportions the fuel? > >You were ill advised. > >>I have the Bosch D Jetronic EFI on my two Porsche 914's, and also have >>a tester for the Djet. It will test the Merc 450, but I have never >>looked at a Mercedes, as I don't much like radiators and hoses and >>waterpumps. The D stands for Druck, or pressure. The later Ljet is >>for Luft, or air(flow). >> >>The Djet uses a Manfold Pressure sensor, which is a transformer with a >>core that is pulled against a spring by vacuum. It also uses a pair of >>trigger points located in the base of the distributor (dizzy to you in >>SA). In the 4 cyl VW and Porsche, the trigger points start the >>injection for each pair of cylinders on every other revolution. It >>would fire four at a time in the V8. > >Not according to the bosch service manual. It sez that their are four >injector circuits with 2 injectors on each, and specifys at what point the >injectors begin their pulse in reference to valve opening. Maybe you were >thinking of the system used on Cadillac V-8's, they work that way. No, I just was going on very old memory. You are right, four pairs. > There is apparently no real >>advantage to squirting fuel toward an open valve, as they could have >>done it and didn't. > >Actually they did do it, but several others haven't, and the >diferences seem>to be minimal. GM uses a batch fire setup while Ford >uses sequential and>there seems no great performance difference. Bosch did it in some 914's, not others. > >>The Djet is the grandfather of EFI. It was patentd by Bendix in 1952 >>after they reportedly stole it from some guy who developed it in his >>garage. Bendix licensed it to Bosch in the sixties, at the request of >>VW. Its first use was in the '68 Fastback/Squareback. >> >>As with all electronics of the era, it is primitive by today's >>standards. However, it does an outstanding job in a stock engine. >>I am working on mods to it so the hiperf engine in one of my 914 will >>idle below 2000, and still get enough fuel at 6000. >> >>RD >> 81 VW Vangon aircooled four with Ljet EFI >> 76 Porsche 914 stock commuter with Djet >> 73 Porsche 914 hiperf commuter with Djet >> 46 Bellanca Cruisair with 165 hp Franklin (Aircooled Motors) >> 34 Franklin Olympic sedan with 100 hp aircooled upright six >> >> Except for some boats and ships, all engines are aircooled anyhow. >> Why bother with water? > >Because some of us would prefer do do something with our lives besides >screw>around rebuilding engines. My water cooled 54 Cornbinder eng. >runs fine and>has never been rebuilt. Well the cornbinder engine in my '63 Metro needs to be rebuilt. Wanna' help? RD ------------------------------ From: Daniel R Burk Date: Sat, 24 Aug 1996 22:54:56 -0700 Subject: Strain gages on the drive shaft for torque measurement In regards to the message about placing strain gages on the drive shaft: There exist slip ring assemblies that allow one to gage up a drive shaft. There is a spinning amplifier that is placed on the driveshaft to boost the gain from the wheatstone bridge configuration strain gages. The slip ring has remarkably low noise: Witness the fact that they are still widely used in automotive testing to gather wheel loading information. Another method used to determine torque (as well as payload in trucks) is to gage up the axle assembly. The gages are placed on the axle housing where they measure the deformation caused by either truck payload, or torque from the engine. I have heard engineers at my firm say that readings within 10 ft-lbs are possible. Don't just rule out slip rings by saying they are "complicated". Most modern slip rings use brushes on gold contacts, where the contacts are mounted on a spindle of only a quarter inch diameter. The angular velocity is therefore very low. Hence, brush noise is minimal. - --- Cheers, --Daniel Burk ['84 Trans Am WS6/L69] Instrumentation engineer at Michigan Scientific Corp. ------------------------------ End of DIY_EFI Digest V1 #245 ***************************** 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".