DIY_EFI Digest Thursday, December 9 1999 Volume 04 : Number 686 In this issue: Re: mopar injector options maximum ON before damage EGO sensors work at stoich because See the end of the digest for information on subscribing to the DIY_EFI or DIY_EFI-Digest mailing lists. ---------------------------------------------------------------------- Date: Thu, 09 Dec 1999 06:45:43 -0500 From: David Brode Subject: Re: mopar injector options > > From: "Bruce Plecan" > Subject: Re: Mopar injector options > > | If anyone cares to read about various Mopar FI hacks, > | there are a few options shown at > | http://pages.cthome.net/gus/fuel.html > > I'm not thrilled by em. Crushing a FPR to change the spring rate is a one time > deal, and if wrong you've wasted it.... > > Some testing has shown 100 PSI for a TPI injector is no problem. Been > documented at the syty area. > > Lower pressure generate lousy spray patterns. I'm leaning toward a variable rate > one, done by a lister here. Can you tell me more, or head me to info about this lister and his regulator? > We speak CSH, HQ lingo here, least I do > Grumpy Hurray for you. I wish I knew more, but this list is helping me learn. Dave Brode FI newbie ------------------------------ Date: Fri, 10 Dec 1999 02:48:38 +1100 From: Phil Lamovie Subject: maximum ON before damage Hi John et al, Injectors that are higher resistance 10 -16 ohms are saturated inductors and require no current limiting. They can be left on indefinitely as long as they have been designed correctly. They are a bit slow to open and thus have a higher minimum ms before stability is reached. approx. 2.5 ms. Lower resistance injectors are high current devices that must be handled with respect. They will draw 3-5 amps and will self destruct in seconds with out current limiting. The usual ratio being 4:1. They are fast to open 0.4 - 0.9 ms and thus need to be limiting very soon after saturation. The limiting factor with any injector is the max. time in ms available at max. rpm. If that rpm is say 6,000 rpm we have 10 ms total. If it takes 1.2 ms to open (saturated type) and 1.1 ms to close you only have 7.7 ms left. Just to make things difficult the first period of 1.2 ms has NO flow. So really that 2.5 ms lower limit (for stability's sake) means you have 2.5 -8.9 ms to play with. Now the required flow needs to take place in this window thus the duty cycle limit of approx. 80%. Don't forget that at minus 20 deg C the accelerator can still be floored and you can't run out of duty cycle at any air/water/manifold vac or the valves will say ouch. Once again I must ask are you pulsing once per revolution or every second / If once your figures don't add up. If every second your choice is incorrect. The sequence is not an issue. How often do you fire No. 1 injector ? If you apply a table with load vs rpm values instead of you falutin' volumetric eff. table you would find that the map sensor response of 1-3 ms is sufficiently fast to react within 1/4 of a revolution even at moderately high rpm. If your code does a run through in under 10 ms you will never miss more than 1 p/w correction. You might be in the middle of an output event as the vacuum drops but most throttle movements take 200 - 300 ms from start to finish and thus many injection cycles b/w start and finish. As to the 40 ms pulse... I don't think so. The maximum fuel required is more a function of poor combustion at low rpm than anything else but given a max. p/w of 8.5 at 6000 rpm then the pulse width at full load 1000 rpm would be 8.5 plus the excess fuel required due to poor tumble, swirl, vaporization etc. etc. Probably no worse than 4 -5 ms extra will be required. Don't forget to decay this in proportion to the rate of change of rpm (derivative of PID ) This still points to a short coming that you have imposed with your 12.7 ms upper limit. Full load plus cold air plus cold water plus acc enrichment will put you badly in debt even at low rpm. 8.5 + 20% + 60% + 5 ms = 17.24 ms Your in the pursuit Phil ------------------------------ Date: Fri, 10 Dec 1999 03:02:27 +1100 From: Phil Lamovie Subject: EGO sensors work at stoich because Hi All, EGO sensors work at stoich because they were designed to. Better question is who wants it in the first place ? Answer... the catalytic converter needs the mixtures to be very close to lambda if it has any chance to do it's job. Slightly rich say 0.95 to reduce nox by reduction and slightly lean say 1.05 lambda to oxidize hc's by way of combustion. Worse than that it needs to oscillate between the two quite often. At least 3-5 times a second. It's all quite tedious and has not got a DAMN THING to do with how an engine wants to run. The mere words closed loop and O2 sensor (which it patently isn't) give me the willys. Never confuse pollution control with correct engine management. Never use a single wire O2 sensor for doing anything other than filling the whole that it came in. If that's a sensor then a ruler would be a piece of wood with 1 foot written on it in words with no other markings. This "sensor" would allow you to judge if an object was more or less than a foot long but not anything else. Same with a simple O2 sensor. It only sees richer or leaner than lambda and any $10 voltmeter attached to it would still render it an on/off switch. Your in didactitude.. Phil ------------------------------ End of DIY_EFI Digest V4 #686 ***************************** 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".