Date: 5 Jan 1999 02:47:09 GMT From: "A4 quattro" <richquinlannopsamamatt.net> Subject: Re: More thoughts on my pinging problem
Well, as for boost vs. C/R, my C/R is 9.5:1, and I run 14.5 psi on 93 octane Exxon Pump gas with no detonation. Gotta love modern fuel injection and computer control! (well, SOMEtimes....) -- Rich Quinlan '97 A4 1.8tqms in Pearl, More mods than I can shake a wastegate rod at... **** To reply, remove the 'nospam' after the **** "If it ain't broke, make it faster!!" http://home.att.net/~richquinlan <--- Quinland--my own little world.. Firestarter <NOSPAMnopsamAM.com> wrote in message news:36a0c186.464735232nopsam.preferred.com... >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/ > >------------------------------------------------------------
