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Date: 20 Dec 1998 20:02:56 PST
From: danfnopsam.com
Subject: Re: Turbocharged Engine pings under boost


I would direct your attention to J&S. They should have experience w/your problem on why that $400 device is not doing its job. This assuming your assumptions are correct: GOOD high octane. True 8:1 comp(not at ~8.5 w/carboned up piston tops). It is possible that you have some internal engine noise triggering the J&S unit prematurely. Danny >I recently installed sort of a home grown turbo system on my car. It >really runs great but it starts to ping when it reaches maximum boost. > >The reason I am posting this message in the Saab and Volvo newsgroups >is because they are two of the most popular turbocharged makes sold in >America. > >Here's the specs: > >Car: 1980 Fiat 2000 Spider >Engine : two liter twin cam >fuel delivery system: Bosch L-jetronic FI >Compression ratio: 8.1:1 (stock C/R) >Maximum Boost: 7 pounds >Turbo: Rayjay 301F >Fuel enrichement device: rising rate fuel pressure regulator >engine managment system: J&S Safeguard knock retard device > >First of all: > >I retarded the static timing to 5º BTDC which is 5º below factory >spec, put some octane booster in the tank and even cranked up the fuel >pressure a bit but it still pings. > >I installed a $400 J&S knock sensor to prevent this but I can't seem >to get it adjusted properly. > >If I turn the sensitivity dial all the way down, it doesn't pick up >the ping (I've got a meter that tells me how much the timing is being >retarded). > >if I turn it up even just a bit, it picks up all kinds of weird noises >under slight acceleration and starts backing off on the timing upto >20º long before I reach any boost. > >So either it's picking up false noises or my engine pings under even >slight accleration and I really have problems that I don't know about. > >Here's what I want to know. > >What kind of C/R and boost pressure do Saab and Volvos run? I do >realize that these cars use a knock sensor. > >According to several sources, an engine with a C/R of 8.1:1 using 92 >octane gasoline should be able to handle 7 pounds without an >intercooler with no problems of detonation. > >From what I remember, the engine doesn't start to ping until I hit >maximum boost which means I can turn the wastegate down to 4 pounds >(it has a range of 4 to 7 pounds) and it would probably be OK. > >But I really want to run 7 pounds because more pounds = more power but >on the same token I don't want to burn my engine up. > >Then again it's been in the 50s today so 4 pounds be OK in this >weather but in the summer when it's 95ºF, I don't know what is going >to happen. > >I've got an adjustable (0.5 to 24 pound) pressure switch, which I am >thinking about using to trigger the cold start valve which will dump >fuel into the engine under boost. > >I've got it already mounted after the throttle body. > >I did a test before the turbo installation and triggered the cold >start valve under wide open throttle with my fog light switch and it >tended to flood the engine out but it may work fine under boost. > >I also have an air fuel meter guage and can say that the ping is not >caused by an overly lean mixture. The mixture is around 14.1 under >maximum boost. > >Seems like I read somewhere that under boost, a mixture of 12.1 to >13.0 is the right range under boost so maybe that is the trick to >getting rid of the detonation. > >Sorry for posting all of these figures in pounds per square inch but I >am not familiar with BAR because I live in America. If someone knows >the formula to convert PSI to BAR, please post so I can convert these >figures. > >Any ideas to stopping detonation are appreciation. > > >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/ > >------------------------------------------------------------ danfnopsam.com

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