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Date: Wed, 30 Dec 1998 06:00:40 GMT
From: NOSPAMnopsamAM.com (Firestarter)
Subject: Re: More thoughts on my pinging problem


On Mon, 28 Dec 1998 19:46:08 -0500, "B. Vibert" <usgtrvtqnopsamail.com> wrote: >Network Voyager wrote: > >> >> >Hi, again, Firestarter - - - >> > >> >Forget your pressure regulator, it's working just fine, too. Remember >> >that the box has the capacity to adjust the *duration* of injection - >> >that's where the quantity of flow is determined. A major role of the O2 >> >sensor is to determine how flow is relating to the combustion process, >> >with the box then determining how long/much to inject +/-. > > >Hi > >I missed the first part of this conversation so I may be off base here. If this >is a K-jetronic type system there is no duration of injection, it is pressure >regulated. More air flow (fine tuned by O2 sensor and other sensors) means more >pressure which causes the injector to flow more. >I would suggest tuning the mixture as it appears to now be beyond the range >that the O2 sensor can correct for. If it is K-jetronic you need a 3mm hex key >(I think) and a tiny adjustment makes a large change. > > >> >> >Pressure regulation assures efficient operation of the injectors. As >> >gasoline engines don't depend on pressure to operate the injectors, wear >> >can be compensated for (an is) on each individual injector. > >Depends on the system, some systems don't work this way. >> >> So if everything is then good then the car will likely run for a >> bit as there is fuel flow but no regulation (once part removed).... >> > >Aftermarket rising-rate pressure regulators are a popular addition to modified >K-jetronic engines. What system is on the car in question? > >Burl Vibert > >> > >> >bob noble >> >Reno, NV >> > >> >Firestarter wrote: >> >> >> >> This is a continuation from my earlier post entitlted "Turbocharged >> >> engine pings under boost". I was the original poster of the question. The injection system is an L-jetronic system. The car is a Fiat Spider. As I understand under positive manifold pressure, the flap inside the air flow meter is maxxed out so the injectors are as well. However I installed a rising rate fuel pressure regulator so the pressure increases with manifold pressure which is suppose to make up the difference. I found that unplugging the O2 sensor, I get a constant mixture of 13:1 even at 7 pounds of boost. And with a some adjusting, I got the mixture to 13:1 with the O2 sensor connected. I was able to reach this mixture by cranking up the fuel pressure. When this happened, the control loop appeared to have stopped cycling uner cruise and stayed a constant 14:1. But even at this, the engine still pinged. However my J&S knock sensor which is supposed to retard the timing based on engine knock appears to be retarding the timing based on RPMS. In other words, I think it's picking up false knocks. When the timing is backed off an incredible 20º, the pinging is reduced but is still there. I know that with the timing backed off this much has to effecting power to some extent. I am starting to think my problem is I am exceding the maximum rated boost level for my engine. From what I have read, my engine which has a "factory" C/R of 8.1:1 should be able to run a boost pressure of 7 pounds on 92 Octane without an intercooler. however I suspect that since the head has been milled when I had the engine overhauled, + 40,000 miles (possibly some carbon buildup), the C/R is much higher than I suspect. A friend once had a 2.3L Thunderbird that was turbocharged. It ran a boost pressure of 15 pounds but the C/R was probably reduced to 7.5:1. My engine seems to ping at around 5 pounds. Estimating the C/R could be as high as 8.7:1, 5 pounds may be the maximum boost pressure I can run. Unless I install an intercooler. In other words, the temperature of the air leaving the turbo is just too hot and ignites due to the C/R. Due to the overwhelming amount of SPAM I receive, send replies via email to mailto:firestarternopsamcron.com ------------------------------------------------------------ 1980 Fiat 2000 TURBO Spider (Fuel injected) Summertime daily driver 1981 Fiat 2000 Spider (Dual 40 webbers) Growl! 1981 Fiat X 1/9 (Fuel injected) Slot car like handling 1994 Jeep Wrangler (2.5 liter) Wintertime daily driver Get your own Forwarding address : http://www.netforward.com/ ------------------------------------------------------------

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