Date: Wed, 23 Dec 1998 07:15:32 -0600 From: "DSDTINC" <dsdtincnopsamcom> Subject: Re: More thoughts on my pinging problem
Have you considered water injection? That worked quite well for WW II fighter planes. When the pilots needed extra horsepower for takeoff or in combat, they hit a switch to inject water into the fuel-air flow. The water allowed the superchargers to "overboost" without detonation. Horsepower increases ranged from 8-18% with water injection. Water injection eliminates (or at least reduces) pinging by absorbing enough of the heat caused by compression to the point where the remaining heat is insufficient to ignite the fuel-air mixture. The droplets also improve combustion, but I won't go into that now (since the topic is pinging). You can read about a modern water injection system at: http://www.aquamist.co.uk/ If you want to try water injection without having to buy and install a water injection system, consider an emulsion-type fuel additive such as F2-21. One-two milliliters per US gallon of gasoline adds enough water to eliminate pinging in all but the extreme cases. The resulting emulsion is complete stable. (I.e., the water will not separate from the gasoline.) Let me know if you want more info. (Don't forget to edit my e-mail address if you reply.) Dave DSD Technologies, Inc. Firestarter wrote in message <368a7bbb.270432769nopsam.preferred.com>... >This is a continuation from my earlier post entitlted "Turbocharged >engine pings under boost". > >I have a theory. I first thought that the O2 sensor would benefit my >turbo system, but now I am thinking it may actually be causing my fuel >enrichment problem. > >Here's the reason. > >The oxygen sensor's job is to keep the mixture within an acceptable >range (for emmision purposes). I came to the conclusion that the O2 >sensor's goal is to make up any deviation caused by wearing >components, changes in altitude, temperature, etc. > >The system has a set of known variables it goes by but relies on the >reading from the O2 sensor to keep these in range in case something >changes. > >That's the problem with carburators. You set them to run at a given >temperature, humidity and altitute but when you stray away from those >conditions, the mixture changes. > >On my X 1/9 which has almost 200,000 miles on it, a new oxygen sensor >made a world of difference because the engine was running way too >rich. I even got an extra 10 miles per gallon! > >But on the Spider which has a new air flow meter and half as many >miles on the componetns, a new oxygen sensor made no difference. > >Some earlier L-jetronic systems like the ones used on Datsun Z cars up >until 1979 did not use an O2 sensor but the system was otherwise the >same. Actually this system was a clone built by Nippon Denson under >licence from Bosch. > >When I hit boost, I want to mixture to be at around 12.1. As of now, >the richest it get's is 14.1. Just like it before I installed the >turbo under WOT. > >I keep cranking up the fuel regualtor but it does not have any effect >on the mixture under boost. > >It did not occur to me until now, but the oxygen sensor is doing what >it is supposed to do. My original theory was that when the turbo >started forcing air into the engine, the O2 sensor would pick up the >lean mixture and add more fuel which would keep the mixture from >leaning out. It seems to be doing this, however it also seems to be >limiting the fuel mixture to 14.1 under boost. > >Under wide open throttle, the contacts close in the throttle position >switch and bypass' the control loop. This is one of the tricks used by >Legend industries. At 1 pound, a pressure switch closed the WOT >contacts which bypassed the closed loop allowing the other two >switches to trick the coolant temperature switch into thinking the >engine was running colder which enrichened the fuel mixture. > >Without tricking the TPS, the lambda system would override the first >two switches and try to keep the mixture from getting any richer than >14.1 . > >That's why I suspect my fuel pressure regulator is not doing it's job. > >I think it's as simple as disconnecting the oxygen sensor from the >computer. > >In one of my experiments, I found that by doing this caused the engine >to run lean and not cycle. Some say by doing this causes the engine to >run rich. But if you look in the shop manual, it says to disconnect >the O2 sensor and set the mixture by turning the screw in the air flow >meter. > >Or I can rig up the same sort of switch to close the WOT throttle >contacts under boost like LI did, but I see no reason to because by >unplugging the O2 sensor will do the same. > >Or install the pressure switch to break the circuit between the >computer and O2 sensor under boost. > >So here is what I need to do, unplug the O2 sensor, set the mixture to >14.1, leave the sensor unplugged and see what the mixture is under >boost. > >As boost increases, the fuel pressure should also rise and get richer. >Then I can adjust the fuel pressure regulator to what I want the >mixture to be. > >The control loops seems to be defeating the purpose of the rising rate >fuel pressure regulator. > >However there is always the fact that the mixture may actaully go the >other way under boost. I will just have to wait and see. > > >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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