DIY_EFI Digest Sunday, October 10 1999 Volume 04 : Number 572 In this issue: Re:Up Up and Away Re: DIY_EFI Digest V4 #571 Re: DIY_EFI Digest V4 #570 Re: DIY_EFI Digest V4 #570 Re: DIY_EFI Digest V4 #570 Re: DIY_EFI Digest V4 #571 Re: DIY_EFI Digest V4 #570 See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- Date: Mon, 11 Oct 1999 00:50:01 +1000 From: Phil Lamovie Subject: Re:Up Up and Away Hi John et al, sorry 'bout the html had to reload NT (i moved the mouse)and got all of the default settings. Now to buisness. The abundance of calculations offered is in no way justified by the starting assumptions. The tribology of gaseous flows is both relevant and irrelevant in the same breath. The approach to fuel injection as a science of calculations is not a valid one if you accept that the simplest solution is the best. The "manifold absolute pressure" is by it's very explanation a measure of the environment INSIDE the manifold. It has no concern with the outside weather conditions ONLY the inside. The original question remains unanswered. How can the engine tell... Lets take an engine on the dyno at 35% throttle at 3000 rpm. Air temp 20 deg C pressure in manifold 70 kPa Absolute. We adjust our fuel and spark table to give target A/F ratio of 13.5:1 with MBT as the spark setting. I will assume that at this time all the relevant perturbations of the air column are taking place in all of their Bernoullian Wonderment. The very simple point to be had here is that next time the same air temp and pressure are found at the same rpm then the same stored values for fuel and spark will of course produce the same A/F ratio. Note how I completely left out the throttle position. It may be that at 15,000 feet ASL the WOT pressure will be only 70 kPa. If the engine is at 3000 rpm and the air temp is the same the Volumetric efficiency of the engine is the same. The real test for flow is NOT across the butterfly !!! It is of course a variable device where as the inlet port is not. The speed of the air through the inlet port will of course be the same at the same manifold ABSOLUTE pressure and temp and rpm. Carbys care about air velocity EFI couldn't give a rats arse. This is very relevant with plenum type manifolds some what diff with individual trumpets as the mass of the External fraction causes the MBT to be found at slightly shorter trumpet lengths. As all of the mechanical components are bound by their shape in the repetition of their function so is the ecu bound to give the same values for fuel and spark. The point of measuring the pressure is to know what map point to use and how much interpolation b/w points is required. There is absolutely no need to calculate the mass of the atmosphere on Earth and then divide that by the ratio of volume of inlet manifold. Though it would work. Please note the total lack of Patents for Altitude correction of aircraft fuel injection computers. Also total lack of altitude sensors on all Ford and GM vehicles. I suppose they don't have mountains in the USA. My company has also supplied ECUs for Aircraft that have flown from England to Australia, film is available from National Geographic. I promise they were all fitted with absolute sensors. The engine were all dynoed on a thirty foot tower (they had very big props about 33 feet span) 650 hp at sea level)) and then flew half way around the world. Hope the simplicity of it is not too hard to fathom. Phil Injec Racing Developments ------------------------------ Date: Sun, 10 Oct 1999 14:31:01 +0100 From: Ade + Lamb Chop Subject: Re: DIY_EFI Digest V4 #571 At 05:00 10/10/99 -0400, DIY_EFI Digest wrote: >Hi , I'm new to this mailing list. I've been reading some of your messages on >how simple a fuel injection system can be. Just before I graduated H. S. in >98 my school auto program put efi on our race car. Its a 82 regal with a 454, >Th. 400 trans and 3.73 gears in the rear. We were running low 12's and then >with the efi took the car in to the 11.50 area. this car has never really >been tuned to its potential it only see's 5200 rpm through to traps and it >shifts out of 1st and 2nd around 6300. Its Holleys Pro-Jection system. You >can find info on the web at Holley's web page. All it has for inputs are >temp, tps, and a tach sig. I believe the temp sensor only controls the idle >solenoid and a/f below 165 degrees. Theirs 5 or 6 knobs to control the mix >and its real easy to set up. In theory (dons flame proof jacket) Carbs can be every bit as good as fuel injection. It is just that carbs have a little bit of an art to setting them up. FI you just plug a lap top in and correct what needs correcting Like that. Ade ------------------------------ Date: Sun, 10 Oct 1999 14:26:55 +0100 From: Ade + Lamb Chop Subject: Re: DIY_EFI Digest V4 #570 At 15:00 09/10/99 -0400, DIY_EFI Digest wrote: >I think you could easily do with only the distributor as a crank position >input, SO LONG AS YOU DO NOT CONTROL THE IGNITION SYSTEM from the computer. If >you want to do ignition timing, then those errors are going to hit you (well, >I have a qualitative feeling that they will matter). If you are controling the igntion system you would have a VERY accurate CPS so you would just take the speed reading for the Fuel injection from the CPS. The whole point of using the coil is that you don't have a CPS in the first place as the engine was orriginally a carbed engine and the CPS is expensive for minis at the moment. Ade ------------------------------ Date: Sun, 10 Oct 1999 14:26:55 +0100 From: Ade + Lamb Chop Subject: Re: DIY_EFI Digest V4 #570 At 15:00 09/10/99 -0400, DIY_EFI Digest wrote: >I think you could easily do with only the distributor as a crank position >input, SO LONG AS YOU DO NOT CONTROL THE IGNITION SYSTEM from the computer. If >you want to do ignition timing, then those errors are going to hit you (well, >I have a qualitative feeling that they will matter). If you are controling the igntion system you would have a VERY accurate CPS so you would just take the speed reading for the Fuel injection from the CPS. The whole point of using the coil is that you don't have a CPS in the first place as the engine was orriginally a carbed engine and the CPS is expensive for minis at the moment. Ade ------------------------------ Date: Sun, 10 Oct 1999 14:23:19 +0100 From: Ade + Lamb Chop Subject: Re: DIY_EFI Digest V4 #570 At 15:00 09/10/99 -0400, DIY_EFI Digest wrote: >Subject: RE: How completcated does Efi HAVE to be? Not that complicated! >Bosch LE/LE2 based systems have been taking EFi trigger signals from the >ignition for years.. That is good to know. >Don't lose sight of the big problem with mini's - siamesed ports! For those >not so familiar, the head has two inlet ports which each split in two to >feed two inlet valves; Cyls 1&2 are fed by one inlet tract and cyls 3&4 fed >from the second. Throw the firing order into the equation, and you will >appreciate the problem of mixture distribution, specially from a throttle >body injection arrangement. for this reason, Mini's run with uneven mixture >across the cylinders even with carbs that feed fuel into the airstream >continuously. Consider what happens when you inject pulses of fuel into the >airflow way back at the throttle body, synchronous with the engine cycle. >This is why I believe some (if not all) TBi sytems inject 'asynchronously' >(randomly?). Certainly Vauxhall/Opel Multec TBI systems inject 5 pulses per >cycle to try and spread out the uneven distribution so that each cylinder >gets a fighting chance of seeing reasonable mixture on average. Carbs manage it acceptably I was thinking of just streaming fuel in the same way carbs do. After all Tbi is just a carb with an injector controled by a processor rather than 'machincal means' >Don't let this put you off - Rover obviously achieve reasonable results; >indeed if you 're not using the 'A' series engine, and you've got an 8-port >head, then please bung this message in the bin... SU carbs have been doing it for 40 years!!! 8 port!! Don't be silly!! :-) Mind you there are the Arden heads 8 port X flow/8 Valve and KAD 16V alloy heads But if I had that sort of money I would need to ask you lot would I!!! Thanx, Ade ------------------------------ Date: Sun, 10 Oct 1999 14:31:01 +0100 From: Ade + Lamb Chop Subject: Re: DIY_EFI Digest V4 #571 At 05:00 10/10/99 -0400, DIY_EFI Digest wrote: >Hi , I'm new to this mailing list. I've been reading some of your messages on >how simple a fuel injection system can be. Just before I graduated H. S. in >98 my school auto program put efi on our race car. Its a 82 regal with a 454, >Th. 400 trans and 3.73 gears in the rear. We were running low 12's and then >with the efi took the car in to the 11.50 area. this car has never really >been tuned to its potential it only see's 5200 rpm through to traps and it >shifts out of 1st and 2nd around 6300. Its Holleys Pro-Jection system. You >can find info on the web at Holley's web page. All it has for inputs are >temp, tps, and a tach sig. I believe the temp sensor only controls the idle >solenoid and a/f below 165 degrees. Theirs 5 or 6 knobs to control the mix >and its real easy to set up. In theory (dons flame proof jacket) Carbs can be every bit as good as fuel injection. It is just that carbs have a little bit of an art to setting them up. FI you just plug a lap top in and correct what needs correcting Like that. Ade ------------------------------ Date: Sun, 10 Oct 1999 14:23:19 +0100 From: Ade + Lamb Chop Subject: Re: DIY_EFI Digest V4 #570 At 15:00 09/10/99 -0400, DIY_EFI Digest wrote: >Subject: RE: How completcated does Efi HAVE to be? Not that complicated! >Bosch LE/LE2 based systems have been taking EFi trigger signals from the >ignition for years.. That is good to know. >Don't lose sight of the big problem with mini's - siamesed ports! For those >not so familiar, the head has two inlet ports which each split in two to >feed two inlet valves; Cyls 1&2 are fed by one inlet tract and cyls 3&4 fed >from the second. Throw the firing order into the equation, and you will >appreciate the problem of mixture distribution, specially from a throttle >body injection arrangement. for this reason, Mini's run with uneven mixture >across the cylinders even with carbs that feed fuel into the airstream >continuously. Consider what happens when you inject pulses of fuel into the >airflow way back at the throttle body, synchronous with the engine cycle. >This is why I believe some (if not all) TBi sytems inject 'asynchronously' >(randomly?). Certainly Vauxhall/Opel Multec TBI systems inject 5 pulses per >cycle to try and spread out the uneven distribution so that each cylinder >gets a fighting chance of seeing reasonable mixture on average. Carbs manage it acceptably I was thinking of just streaming fuel in the same way carbs do. After all Tbi is just a carb with an injector controled by a processor rather than 'machincal means' >Don't let this put you off - Rover obviously achieve reasonable results; >indeed if you 're not using the 'A' series engine, and you've got an 8-port >head, then please bung this message in the bin... SU carbs have been doing it for 40 years!!! 8 port!! Don't be silly!! :-) Mind you there are the Arden heads 8 port X flow/8 Valve and KAD 16V alloy heads But if I had that sort of money I would need to ask you lot would I!!! Thanx, Ade ------------------------------ End of DIY_EFI Digest V4 #572 ***************************** 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".