knock sensors, ancient history

[Todd King]

  <<<   From: talltom <talltom at teleport.com>
  Date: Mon, 2 Sep 1996 09:36:12 -0700 (PDT)
  Subject: Re: Knock sensors
    I did a Corvette with a turbo on it and used a old buick spark retard
  system, and while it worked, I wasn't really very happy with it. It would
  retard 3 degrees for every clatter it didn't like, and hold it for 20-60
  seconds. The problem was that it was inconsistent, back to back runs would
  vary widely. In fact one day it decided to run harder than it had previous
  and fried the tires hitting second. The result being the rear end stepped
  out to the left and the car climbed the curb to teh demise of the right
  front corner.
    My question is what kind of expieriences have others had with knock
  retard systems? I'd think that by now this would have been refined some.
  >>>
  
        The knock system is subject to false knock indications and must
  be carefully calibrated for the various engine combos, sensor placement,
  etc. However, properly executed it works very well. On the '87 Turbo
  Regals the ECM processing of the knock system (ESC) signals can be 
  programmed for retard attack rate, timing recovery rate, etc. Never will
  we see the timing retard linger for more than a brief instant though-
  you may have had a false knock problem?
  
  <<<   From: "Robert J. Harris" <bob at bobthecomputerguy.com>
  Date: Mon, 2 Sep 1996 10:06:26 -0700
  Subject: Ancient History
  He drilled the heads so that the untimed variable flow injector sprayed
  directly on the intake valve from the back side of the valve pocket.  What
  was lacking in mechanical sophistication was made up in simple physics.
  ...
  From: "Tony Bryant" <bryantt at psc.fp.co.nz>
  Date: Tue, 3 Sep 1996 08:53:10 +1200
  Subject: Re: Ancient History
  ...
  What I want to know, is what happens when you have radical
  cam timing? This nice puddle of fuel on the inlet valve
  ...
  comments?
  >>>
  
  Comments? OK! :-) Get some forced induction and say "later" to all the
  big cam blues, and make more power to boot! True story: Kent Rudbeck
  of Muncie, Ind (one of many) runs 10.3x at near 130mph in his 231" V6 
  Turbo Regal. Cam specs at 0.050"? Duration- 200deg; lift- about 0.430".
  My Turbo Regal went 12.59 at 108.9 a few weeks ago with a ridiculously 
  slow launch (taking it easy on it); mods from stock are minimal at best. 
  Engine internals are pure stock; these times are typical for these cars.
  Well, sorry about the lumpy cam diatribe...
        We are getting some interesting EFI data during these 1/4 mile
  runs. We all appreciate the control potential that EFI gives us over the 
  various engine parameters. But in reality there are lots of unexpected
  things going on. For example from the runs I made a few weeks ago I
  found that 1) my MAF sensor was maxed at 255 (8 bit) the entire run.
  2) my injector duty cycle was 100% almost the entire run, even with
  injectors that are 25% larger than stock (36lb/hr vs 28lb/hr). So this
  means that the only things controlling the A/F during the run were
  airflow (boost) and base fuel pressure setting. Basically I could have
  wired the injectors "ON" to a twelve volt source and had exactly the
  same results! These static MAF and injector duty cycles at WOT are not 
  uncommon; it's amazing how fast you can go, even when the EFI is out of 
  control!
        As for spraying the back of the intake valve- that's typical
  as well. Interesting that many of the fuel injectors used these days
  make little attempt to atomize- what they fire is a stream, not a mist.
  You can make loads of power either way!
  
  Todd  Todd_King at ccm.co.intel.com