Computer timing question
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From: Holbrook NY
Computer timing question
Can the computer only retard timing? When the wire near the brake booster is disconnected to set the base timing on my 85 'Vette, the engine still has centrifugal advance. Leaving the wire disconnected might be a good way to set up the timing advance curve. There would be no timing retard under load (vacuum advance), or retard from the knock sensor. But weights and springs could be chosen to get maximum tolerable advance. Then the wire could be put back for normal driving and knock prevention. But this only makes sense if the computer can only retard the timing, never advance it. Is that, in fact, the way the computer controllers timing?
George
George
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From: Holbrook NY
Re: Computer timing question (George West)
But if the timing control wire is disconnected, as when setting the base timing, increasing the engine RPMs does increase the advance. The behavior looks exactly like centrifical advance, so I assumed that is was exactly that. Either that, or the computer still does control the timing, even with the magic timing wire disconnected.
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From: Glendale Az
Re: Computer timing question (scorp508)
There is no mechnical or vaccum advance on a C4. The computer can advance/retard as it has to.
:iagree: With the bypass disconnected, the computer still has a little advance to give "in the limp home mode". There is no advance of anykind on a computer controlled C4 distributer. :chevy
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From: Holbrook NY
Re: Computer timing question (69vetteracer)
.........With the bypass disconnected, the computer still has a little advance to give "in the limp home mode".....
That would explain the observed timing advance with RPM while I was setting the base timing. So my idea of setting up the advance for the computer to then retard is obviously nonsense, inspired by my misinterpretation of what I saw with my timing light. I did do a couple of 0-60 timed runs using only the limited advance permitted with the magic timing wire disconnected. 0-60 was 6.15 seconds. Not bad for "limp home mode", but over 1/2 second slower than with the wire connected. Clearly the advance that remains when the wire is disconnected is only minimal, as you just stated.
Thanks for the help.
George
That would explain the observed timing advance with RPM while I was setting the base timing. So my idea of setting up the advance for the computer to then retard is obviously nonsense, inspired by my misinterpretation of what I saw with my timing light. I did do a couple of 0-60 timed runs using only the limited advance permitted with the magic timing wire disconnected. 0-60 was 6.15 seconds. Not bad for "limp home mode", but over 1/2 second slower than with the wire connected. Clearly the advance that remains when the wire is disconnected is only minimal, as you just stated.
Thanks for the help.
George
