DIY_EFI Digest Sunday, March 26 2000 Volume 05 : Number 122 In this issue: Re: Plenum sizing (a little off topic) Valve seats Re: Valve seats Re: O2 sensor question - how it works Re: O2 sensor question - how it works Re: Plenum sizing (a little off topic) Re: Valve seats Re: O2 sensor question - how it works RE: Valve seats MAP sensing for IR systems Re: MAP sensing for IR systems Re: DIY_EFI Digest V5 #119 Re: MAP sensing for IR systems Re: Plenum sizing (a little off topic) Re: Plenum sizing (a little off topic) Cheap protection... Re: Plenum sizing (a little off topic) RE: Cheap protection... Re: Cheap protection... Re: Cheap protection... Re: Cheap protection... See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- Date: Sat, 25 Mar 2000 08:21:03 -0500 From: Scott Knight Subject: Re: Plenum sizing (a little off topic) Grumpy, > Course there is the split manifold like the Viper has using two throttle > bodies. > Lot smaller packaging, and more along the lines of IR, but I'd imagine > different cross sectional area (larger) then a common plenum one, but that > is guessing on my part. > How about 8 butterflies, and a true IR, with a common filter area?. Well, there certainly is plenty of room to do about anything like that if I wanted to. The problem is that for right now, the engine bay needs to at least look 'normal' because I autocross and street race this car. At least I could stick a SuperRam on there if I wanted a big plenum in a bulky package, and that requires only minor fabrication to work with the LT1. Just about anything else is going to be built from the ground up. I might go there in the future if I have time for that, but for now, the important thing is to get it running, and I thought it would be easy to add on to the OE intake. In fact, there is nothing on the top or rear of the plenum except space, so I could really add all I needed if I didn't care about ugliness. Would be fun on the dyno to see what it really wants. Later dates. - -- Scott Knight mailto:scott@xxx.com http://www.scottknight.com/ IRC:SS396man '95 Black Impala SS '94 Ducati 900SS CR - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sat, 25 Mar 2000 13:34:33 +0000 From: Mike Blakey Subject: Valve seats I have a cast iron head, Ford V6 Essex, which does not have valve seat inserts. It has to date been very reliable, running on a Carb and ECU ignition (home made). Here in the UK we have just (1st Jan 2000) had leaded fuel banned, so I am concerned as to the potential problems. I've heard so much conflicting advice about un-leaded fuel and valve seat inserts. Does anyone have any real experience of running without lead on a tuned motor? - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sat, 25 Mar 2000 06:52:35 -0700 From: bearbvd@xxx.net (Greg Hermann) Subject: Re: Valve seats >I have a cast iron head, Ford V6 Essex, which does not have valve seat >inserts. It >has to date been very reliable, running on a Carb and ECU ignition (home made). >Here in the UK we have just (1st Jan 2000) had leaded fuel banned, so I am >concerned as to the potential problems. I've heard so much conflicting >advice about >un-leaded fuel and valve seat inserts. Does anyone have any real experience of >running without lead on a tuned motor? How late a model is this engine?? Factories have gone, in some more recent cases, to induction hardening the seat area in iron heads. If these heads had this done at the factory, don't worry about it. Greg - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sat, 25 Mar 100 22:23:17 +0800 (WST) From: Bernd Felsche Subject: Re: O2 sensor question - how it works nacelp writes: >> Garfield Willis writes: >> >factory-set "parallel trim value" in the ECU circuitry (which doesn't >> >have the luxury of doing a free-air calibration like we proformance >> >users can), and as such, varys widely for only slight (15% overall) >> >changes in the sensor calibration itself. But there's nothing "typical" >> >about the cal resistor value. It varys widely. >> >> Why can't the ECU do a "free-air" calibration on over-run? >> (Say after 50 revs of "purge".) Just curious. >Some wall setting does occur from reversion. What's this "wall setting" thing? Do you mean wall wetting? Isn't that likely to have evaporated after 50 revs or so? How does reversion apply to a steady-state over-run condition? Sorry to ask so many dumb questions... >PCV valve >Charcoal canister. Certainly worth taking into account. But I thought they were controlled from the ECU nowadays. Not like it's a 1980's antique. :-) Even then; the charcoal cannister won't usually discharge until there's a significant throttle opening on the older systems (usually determined by manifold vacuum) otherwise the idle becomes unstable due to excess fuel vapours from the canister. I'm not sure exactly how that applies to over-run. There's even more manifold depression on over-run so any vacuum-servo valve won't be opening. Anyway, it would make sense not to feed any fuel at all as the spark is often suppressed on over-run as well; it'd just screw up your HC emissions. >Are all contibuting to emissions even thou the fuel may be off during >overrun. - -- Real Name: Bernd Felsche Email: nospam.bernie@xxx.au http://www.perth.dialix.com.au/~bernie - Private HP - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sat, 25 Mar 2000 09:18:11 -0500 From: "nacelp" Subject: Re: O2 sensor question - how it works > Do you mean wall wetting? Shoot me for a dam typo........ > Isn't that likely to have evaporated after 50 revs or so? No, not on all engines. > How does reversion apply to a steady-state over-run condition? Cause before you went into an over run condition, you have have been in a range where it was occuring, and maybe WET'd the walls. You can be amazed by actually working on a car after a over run and shut down, water droplets form every where under the butterflies, and sometimes the WALLS are still WET with fuel. Let it heat soak for a few minutes, and you'll never see it... > Sorry to ask so many dumb questions... > >PCV valve > >Charcoal canister. > Certainly worth taking into account. > But I thought they were controlled from the ECU nowadays. > Not like it's a 1980's antique. :-) I didn't realize you were limiting this to specific years. You have to purge things completely for a 0'ing of calibrating a O2 devise, 0, as in free state. > Even then; the charcoal cannister won't usually discharge until > there's a significant throttle opening on the older systems (usually > determined by manifold vacuum) otherwise the idle becomes unstable > due to excess fuel vapours from the canister. I'm not sure exactly > how that applies to over-run. There's even more manifold depression > on over-run so any vacuum-servo valve won't be opening. Think about it, you have very high vac., with the throttle closed at high rpm, much more so then at idle. The CCP solenoids are cheap, and with dust/use/age, the will "bleed some" > > Anyway, it would make sense not to feed any fuel at all as the spark > is often suppressed on over-run as well; it'd just screw up your HC > emissions. We were talking about WB O2s. > >Are all contibuting to emissions even thou the fuel may be off during > >overrun. An engine is an air pump. Fuel on or off, spark on or off, if the engine is turning, it's pumping air. Throw anything into it, and it effects it's emissions. Grumpy > > -- > Real Name: Bernd Felsche > Email: nospam.bernie@xxx.au > http://www.perth.dialix.com.au/~bernie - Private HP > -------------------------------------------------------------------------- - -- > To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) > in the body of a message (not the subject) to majordomo@xxx.org > - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sat, 25 Mar 100 22:44:08 +0800 (WST) From: Bernd Felsche Subject: Re: Plenum sizing (a little off topic) Scott Knight writes: >> Course there is the split manifold like the Viper has using two throttle >> bodies. >> Lot smaller packaging, and more along the lines of IR, but I'd imagine >> different cross sectional area (larger) then a common plenum one, but that >> is guessing on my part. >> How about 8 butterflies, and a true IR, with a common filter area?. >Well, there certainly is plenty of room to do about anything like that >if I wanted to. The problem is that for right now, the engine bay needs >to at least look 'normal' because I autocross and street race this car. >At least I could stick a SuperRam on there if I wanted a big plenum in a >bulky package, and that requires only minor fabrication to work with the >LT1. Just about anything else is going to be built from the ground up. >I might go there in the future if I have time for that, but for now, the >important thing is to get it running, and I thought it would be easy to >add on to the OE intake. In fact, there is nothing on the top or rear >of the plenum except space, so I could really add all I needed if I >didn't care about ugliness. Would be fun on the dyno to see what it >really wants. The plenum size isn't as important as the resonance characteristics. Intake pulses will reflect off the large cross-section change at the end of the intake tract. The frequency can be calculated to provide the desired dynamic supercharge. Depending on how you do your airflow measurement, the larger plenum will dampen any pressure/flow changes which you sense in either the plenum or in the main inlet leading into it at the throttle valve end. That makes measurement of transients more difficult. A smaller plenum will not mask those transients as severely and will allow pressure pulses from appropriately-phased cylinders to be used for dynamic supercharge as well; so you get (at least) two boost peaks throughout the rev range, dependent upon tract lengths. An example of the use of multiple plenums is on the VR6 engine with variable intake manifold. There are three; one smallish one for two grouops of 3 cylinders each, and a large collector plenum which feeds into them. The short lengths to the small plenums act as ram tubes, and also provide a high-pressure pulse to a neighbour at higher engine speeds. The long length to the main collector comes into play at low speed. - -- Real Name: Bernd Felsche Email: nospam.bernie@xxx.au http://www.perth.dialix.com.au/~bernie - Private HP - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sat, 25 Mar 2000 09:39:05 -0700 From: "Programmer" Subject: Re: Valve seats That was a real concern here too...I've yet to see a problem directly related to loss of lead in fuel. Lyndon. - -----Original Message----- From: Mike Blakey To: DIY_EFI@xxx.org> Date: March 25, 2000 6:37 AM Subject: Valve seats >I have a cast iron head, Ford V6 Essex, which does not have valve seat inserts. It >has to date been very reliable, running on a Carb and ECU ignition (home made). >Here in the UK we have just (1st Jan 2000) had leaded fuel banned, so I am >concerned as to the potential problems. I've heard so much conflicting advice about >un-leaded fuel and valve seat inserts. Does anyone have any real experience of >running without lead on a tuned motor? >--------------------------------------------------------------------------- - - >To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) >in the body of a message (not the subject) to majordomo@xxx.org > - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sat, 25 Mar 2000 08:32:14 -0800 From: garwillis@xxx.com (Garfield Willis) Subject: Re: O2 sensor question - how it works On Sat, 25 Mar 100 17:54:19 +0800 (WST), Bernd Felsche wrote: >Why can't the ECU do a "free-air" calibration on over-run? >(Say after 50 revs of "purge".) Just curious. It's surprising how long it takes to actually GET to free-air concentrations of O2. I don't think a span of time as brief as 50 revs is enough to clean the exhaust; it's a fairly big "gas capacitor" if you will. But you're right; shutdown is about the only possible time available. Methinks it's the old story of the fixed cal resistor trim being "good enough for who it's for". Best engineering choice given the alternatives. >I've found the later SAE papers to be less-generous with technical >details. Could just be the non-random sample I've chosen. Yup, it's just like patents. Depends entirely on the authors. Win some lose most. Gar - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sat, 25 Mar 2000 17:39:40 -0000 From: "Rich M" Subject: RE: Valve seats Mike, I've recently been investigating the options also (1980 RS2000 - 2L pinto); There will be a 'real' additive available in the next few weeks in the UK called Tetraboost. It is being manufactured specifically, contains tetraethyl lead in a Toluene base! If you are interested contact Nik Cookson at Tetraboost, London - 0181 870 9933. I've enquired about hard seat inserts and been quoted £100 to supply and freeze fit 4 hard seats in the Pinto head. - seems the best option really, ends all the messing. That was Paul Inch Engine Services, Plymouth 01752 255563. He considered it unneccesary to renew valves or guides purely on the grounds of the issues of unleaded fuel. Rich > -----Original Message----- > From: owner-diy_efi@xxx.org]On > Behalf Of Mike Blakey > Sent: 25 March 2000 13:35 > To: DIY_EFI@xxx.org > Subject: Valve seats > > > I have a cast iron head, Ford V6 Essex, which does not have valve > seat inserts. It > has to date been very reliable, running on a Carb and ECU > ignition (home made). > Here in the UK we have just (1st Jan 2000) had leaded fuel > banned, so I am > concerned as to the potential problems. I've heard so much > conflicting advice about > un-leaded fuel and valve seat inserts. Does anyone have any real > experience of > running without lead on a tuned motor? > ------------------------------------------------------------------ > ---------- > To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without > the quotes) > in the body of a message (not the subject) to majordomo@xxx.org > - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sat, 25 Mar 2000 12:18:23 PST From: "mike mager" Subject: MAP sensing for IR systems What are the practicalities of MAP sensing for an IR (Independent Runner) intake system? 'Theoretically', with symmetrical intake and exhaust, each cylinder has the same MAP, and needs the same fueling and advance, but what happens in the real world? My books fail to address this obscure issue. Thanks, Mike ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sat, 25 Mar 2000 15:27:05 -0500 From: "nacelp" Subject: Re: MAP sensing for IR systems You need to tie em all together, that is each runner to a common "tank" of min volume, or redo all the filtering, in the ecm. But, then, you want them tied together for referencing to the Fuel Pressure regulator, Also, helps to a small degree smooth out the idle. 1/16-1/8" ID line. Grumpy > What are the practicalities of MAP sensing for an IR (Independent Runner) > intake system? 'Theoretically', with symmetrical intake and exhaust, each > cylinder has the same MAP, and needs the same fueling and advance, but what > happens in the real world? My books fail to address this obscure issue. > > Thanks, > Mike - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sat, 25 Mar 2000 14:43:53 -0800 From: Scotty Grover Subject: Re: DIY_EFI Digest V5 #119 To the Campbells: Try http://users.exis.net/~audserv/Injection.html . The information there may be of some help. > Good Luck, Scotty > Date: Thu, 23 Mar 2000 23:01:23 +1000 > From: "Geoff, Kate & Theo Campbell" > Subject: Bosch ECM circuit mods > > Does anyone know if it is possible to modify, or get information on how to > modify, a Bosch LE-jetronic ECM (analogue). I have a basic diagram with > component numbers & values, but don't know which ones change which > variables. I am thinking along the lines of an early "programmable" > (screwdriver) after-market unit and it's limited settings. - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sun, 26 Mar 100 09:11:39 +0800 (WST) From: Bernd Felsche Subject: Re: MAP sensing for IR systems mike mager writes: >What are the practicalities of MAP sensing for an IR (Independent Runner) >intake system? 'Theoretically', with symmetrical intake and exhaust, each >cylinder has the same MAP, and needs the same fueling and advance, but what >happens in the real world? My books fail to address this obscure issue. Flow dynamics is what happens. That means you need to filter the readings to determine the average pressure - but that probably won't do you as much good because the average pressure doesn't tell you the amount of flow - not directly. You'd need to do quite a deal of testing to determine the mass of air drawn into the cylinder for the average pressure. OTOH, if you measured the pressure just above the intake valve(s) from just before opening, until just after closing, you'd get a reasonable picture of cylinder filling. Note that this could be affected by excessive exhaust backpressure! Another option might be to measure the pressure difference along the runner which also tells you the flow direction - and depending on the length of the runner, will not be as susceptible as a single-point pressure measurement. It would still be smart to measure the pressure difference during intake. An integration of that signal over time is closely related to the amount of air drawn in. You still need to know an absolute pressure, which to save on pressure transducers, could be from a common "collector". - -- Real Name: Bernd Felsche Email: nospam.bernie@xxx.au http://www.perth.dialix.com.au/~bernie - Private HP - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sat, 25 Mar 2000 20:44:12 -0500 From: Scott Knight Subject: Re: Plenum sizing (a little off topic) Bernd, > The plenum size isn't as important as the resonance characteristics. Here is the part where I turn into a complete putz. My understanding was that the runners set up the supercharge frequency by themselves with their shape, area and length. Then the plenum was the Big Damper that allowed you to run a single throttlebody and have all the intake port entrances see the same pressure (within reason). The bigger the plenum, the more damping and consequently possibly soggy throttle response if too big. Seems the pressure waves that come up from the closed valve reflect back into the port at the opening in the plenum. I know this is basically what you said, but that 'resonance characteristics' part has me a little confused. I didn't realize there were plenum shape (?) considerations. This could easily turn into a whole study all it's own... I know there have been engines with variable plenum designs. The VW you mention, and the V6 SHO Taurus is the first that comes to my mind. My understanding was that the SHO just opened the valve between the two halves to make the plenum volume(s) twice as big somehow enhancing high rpm performance. Thought it was strictly due to the volume. Is there more? thanks. - -- Scott Knight mailto:scott@xxx.com http://www.scottknight.com/ IRC:SS396man '95 Black Impala SS '94 Ducati 900SS CR - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sun, 26 Mar 100 10:55:08 +0800 (WST) From: Bernd Felsche Subject: Re: Plenum sizing (a little off topic) Scott Knight writes: >Bernd, >> The plenum size isn't as important as the resonance characteristics. > >Here is the part where I turn into a complete putz. My understanding >was that the runners set up the supercharge frequency by themselves with >their shape, area and length. Then the plenum was the Big Damper that >allowed you to run a single throttlebody and have all the intake port >entrances see the same pressure (within reason). The bigger the plenum, >the more damping and consequently possibly soggy throttle response if >too big. Seems the pressure waves that come up from the closed valve >reflect back into the port at the opening in the plenum. I know this is >basically what you said, but that 'resonance characteristics' part has >me a little confused. I didn't realize there were plenum shape (?) >considerations. This could easily turn into a whole study all it's >own... The transition from runner/tract to plenum is what causes the reflection. An infinite plenum (free air) has no internal resonances to take into account. However, one where there are walls in the vicinity of the end of the runner, i.e. all practical sizes, will have it's own characteristic resonances detrmined by the dimensions of the plenum. I'm not surprised at all that this makes you feel like a putz trying to get to grips with it; The acoustic design is complicated because you're not dealing with steady-state resonances; pressures, temperatures and pulse strengths are usually widely varied. >I know there have been engines with variable plenum designs. The VW you >mention, and the V6 SHO Taurus is the first that comes to my mind. My >understanding was that the SHO just opened the valve between the two >halves to make the plenum volume(s) twice as big somehow enhancing high >rpm performance. Thought it was strictly due to the volume. Is there >more? Yes; the pressure pulses pass from one plenum to the other. The Porsche system (forgot it's fancy name) is also a three-stage switching system where connection of the "plenums" results in improved induction at the highest engine speeds. The Helmholtz equations can be used to approximate the (ideal) resonant frequency plenum/runner combination - assuming a single runner: f0 = c/(2*pi) * sqrt(Am/(l*V)) Where "Am" is the mean cross-sectional area of the runner, "l" is the runner length and V the volume of the plenum. I think you can figure out what "c" and "pi" are. :-) "f0" is the resonant frequency near which the system will act as an amplifier. At approximately half and double f0, the system will start to act as a damper. - -- Real Name: Bernd Felsche Email: nospam.bernie@xxx.au http://www.perth.dialix.com.au/~bernie - Private HP - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sun, 26 Mar 100 11:28:11 +0800 (WST) From: Bernd Felsche Subject: Cheap protection... I'm a little baffled here: Where can I find some examples of cheap signal "isolation" circuits for automotive application? To "cut my teeth" on uC practical applications, I'm designing a uC-based system (fancy interior light delay with acoustic warning) with 5 inputs from switches and "12V" from various automotive circuits. The uC is running at 5V. Cost is a significant factor - the uC is worth only a few bucks, so I don't want to spend hundreds protecting it! Opto-couplers are a bit OTT (IMHO) and large. So far, a simple voltage divider with forward signal diode, and filter capacitor feeding into a (hex) Schmitt trigger (74C14) is how far I've got. But the voltage can vary from about 8V to perhaps in excess of 16V, but I want those levels to be "true" always. The Schmitt will sense 3.5 to 5V as true when running at 5V. Should I include a (4.7V) Zener on the input to the trigger? These component counts are crazy! I'm looking at about 40 for a simple controller; most (around 30) for input protection. - -- Real Name: Bernd Felsche Email: nospam.bernie@xxx.au http://www.perth.dialix.com.au/~bernie - Private HP - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sat, 25 Mar 2000 22:58:31 -0500 From: "nacelp" Subject: Re: Plenum sizing (a little off topic) > > The plenum size isn't as important as the resonance characteristics. > Bzzt. It all has to work in harmony. > Here is the part where I turn into a complete putz. Only if ya let it get away from you. You can study things in such fine detail, that you lose sight of the over all picture. Simply put, on a v-8, 4 stroke engine, at any one time, you'll have a pair of cylinders at each operating stroke, so there will be an intake valve closing, and one opening (or close to that stage), the closing one will tend to slightly "reflect/pressurize" the intake, and with the one valve opening have a slight head start for cylinder filling. All this other stuff is kinda neat to talk about but loses it meaning kinda quickly in the real world, when you start taking about engine accleration rates. It gets to in car testing. With all the money gm/ford/fiat/VW/MB has if there was a good mathmatical model for this stuff it would be a done deal, but it takes as much computer modeling a predicting weather (long term). The cross sectional area, is more about tuning for accleration rate, the lenght for rpm range, and plenum for HP. You can dial these in for a steady state if you want but that don't win at anything other then cruise conditions, its a matter of give and take for what your application is. My understanding > was that the runners set up the supercharge frequency by themselves with > their shape, area and length. Then the plenum was the Big Damper that > allowed you to run a single throttlebody and have all the intake port > entrances see the same pressure (within reason). Damper, well sorta. But, most importantly is that it allows the cylinders to draw on a large volume of air, which is necessary at higher rpm/VEs. Like you mention thou you can go too large, but that isn't as bad as when talking about carbs, when you had the problem of fuel falling out of air stream. Lots of opinions carry over from carbs to EFI, and simply don't apply. Like (not to start the same lame thread again), dyno tuning can optimize a engine for running on a dyno, with the new programmable software, it's getting alot better, but it still takes in car testing to get it perfect. The bigger the plenum, > the more damping and consequently possibly soggy throttle response if > too big. Seems the pressure waves that come up from the closed valve > reflect back into the port at the opening in the plenum. I know this is > basically what you said, but that 'resonance characteristics' part has > me a little confused. I didn't realize there were plenum shape (?) > considerations. This could easily turn into a whole study all it's > own... If that's all you want to do, yep, I'd rather leave things adjustable so I can taylor the plenum, runners to what I want and tune in car. Les Grumpy > > I know there have been engines with variable plenum designs. The VW you > mention, and the V6 SHO Taurus is the first that comes to my mind. My > understanding was that the SHO just opened the valve between the two > halves to make the plenum volume(s) twice as big somehow enhancing high > rpm performance. Thought it was strictly due to the volume. Is there > more? > > thanks. > -- > Scott Knight mailto:scott@xxx.com > http://www.scottknight.com/ IRC:SS396man > '95 Black Impala SS > '94 Ducati 900SS CR > -------------------------------------------------------------------------- - -- > To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) > in the body of a message (not the subject) to majordomo@xxx.org > - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sat, 25 Mar 2000 21:55:35 -0800 From: "Buchholz, Steven" Subject: RE: Cheap protection... ... I forget the actual numbers, but not too long ago I was surprised to read that blowing the horn puts spikes that can be somewhere in the 200v region on the power lines ... I don't think the problem is the cost of replacing the CPU ... it is more the hassle of having to fix something that's broken. I've seen optocouplers that come in small SMT packages ... I'll bet the cost isn't that much. AAMOF, I picked up a really cool demo kit from http://www.lumex.com that included optocouplers and a whole selection of lamps, LEDs & displays. It isn't clear to me that you need to have a voltage divider to protect the input ... a series resistor, perhaps with diodes to the rails should be sufficient. Some parts already have the diodes built in. I'd also put ferrite bead filters on the signal inputs. You may want to look around to see if someone doesn't offer an input device that has built-in protection. Steve Buchholz San Jose, CA (USA) > -----Original Message----- > > Cost is a significant factor - the uC is worth only a few bucks, so > I don't want to spend hundreds protecting it! Opto-couplers are a > bit OTT (IMHO) and large. > > So far, a simple voltage divider with forward signal diode, and > filter capacitor feeding into a (hex) Schmitt trigger (74C14) is how > far I've got. But the voltage can vary from about 8V to perhaps in > excess of 16V, but I want those levels to be "true" always. The > Schmitt will sense 3.5 to 5V as true when running at 5V. > > Should I include a (4.7V) Zener on the input to the trigger? - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sun, 26 Mar 2000 15:05:18 From: "Mike (Perth, Western Australia)" Subject: Re: Cheap protection... At 11:28 AM 26/3/2000 +0800, you wrote: >Cost is a significant factor - the uC is worth only a few bucks, so >I don't want to spend hundreds protecting it! Opto-couplers are a >bit OTT (IMHO) and large. Yeah true - cost is a bummer and yes Opto's shouldn't be necessary due to common ground (provided its a 'good' ground). >So far, a simple voltage divider with forward signal diode, and >filter capacitor feeding into a (hex) Schmitt trigger (74C14) is how >far I've got. But the voltage can vary from about 8V to perhaps in >excess of 16V, but I want those levels to be "true" always. The >Schmitt will sense 3.5 to 5V as true when running at 5V. Well, another option is to use a protected MAX232 RS-232 input/output chip, this already has lots of ESD protection and overvoltage too, depending on the source impedance you'd probably also want a series resistor to the MAX232 input. BTW: The standard MAX232 will protect fairly well, though there are a heap of 15Kv ESD rated devices, which also have wider input range and can handle negative transients quite well. Hey Bernd, did you get that cheap pump from Dick SMith - rockingham ? Rgds :) Mike - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sun, 26 Mar 2000 8:59:50 +0000 From: Mike Blakey Subject: Re: Cheap protection... Why bother with isolation? DC coupled will be fine. Use a voltage divider and do the de-bounce/filtering in software. A simple signal diode from input to Vcc will protect your uP as the Vcc is low imperance. --+--- +5v l l ------- / \ /__\ 1N4148 l l +---------+ l 12v source >-----l 13k l---+------------> input input +---------+ l to uP l l +-----+ l l l 10k l l l +-----+ l l l --+----- GND - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ Date: Sun, 26 Mar 2000 17:51:00 From: "Mike (Perth, Western Australia)" Subject: Re: Cheap protection... At 08:59 AM 26/3/2000 +0000, you wrote: > Use a voltage divider and do the de-bounce/filtering in software. Yeah agree with that for the most part unless the signal range is limited - then use a cheap transistor like BC547 etc. ie Atennuate first then amplify to the 5v range required. > A simple signal diode from input to Vcc will protect your uP as the Vcc is low >imperance. I can see a problem with this. Although one hopes the 5v rail is low impedance - remember its connecte to your other logic so its not good practice to use this as a sink for any incoming noise - it will be reflected across the voltage to your CPU and eprom etc - it might be OK for a range of frequencies but, 5v regulators are notorious for parasitic oscillations, leave the o/p bypass cap off and the device will go into a 65MHz resonant mode - looks awful ! This can also happen if external noise is injected onto the 5v rail, which is what you want to avoid. Its also possible to trigger the 5v bypass transistor into saturation if the spike on its 5v output is too high as this temporarily reverse biases the bypass transistor first then causing a 'over-correction' which can lead to momentary high voltage - it all depends on how bad the noise is. In my design I use a high current 5v regulator (3 or 5Amp) with a reverse diode (UF4004) across output back to input *and* and big fat transzorb across the 5vrail near any inputs with a choke as well on i/p to regulator and on the common pullup rail near any inputs... This is all in addition to using high impedance input rs-232 receivers to translate the dirty automotive stuff down to the nice 5v (or 3v) levels needed for stability... Oh and usually prefer to do some minimal filtering with a low esr input cap due to c=vdi/dt, ie Cap doesn't allow instantaneous voltage changes. The capacitance of even 100nF has far better transient response then the capacitance found in a 1n4148. Don't get me wrong, I'm sure your approach will work for most of the time, but any high voltages from ignition impressed on the line could make your 5v flakey for a time - long enough for a failure or partial failure that looks like s/w errors... Rgds Mike Massen Ancient Sufi saying: "Should your God save you from adversity, choose another God" Pictures of site installation at Mendulong near Sipitang, Sabah (Malaysia) for container based RAPS... http://www.wantree.com.au/~erazmus Vehicle modifications on GMH Turbo, twin tyres, possible 175Kw at wheels Preliminary pictures at http://www.wantree.com.au/~erazmus/Twin_tyre_vehicle/ My editorial on twin-tyre opinion and good reference about tyres:- http://www.geocities.com/MotorCity/2195/ttyreopinion.html - ---------------------------------------------------------------------------- To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes) in the body of a message (not the subject) to majordomo@xxx.org ------------------------------ End of DIY_EFI Digest V5 #122 ***************************** 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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