incorrect timing cause water reversion
05-04-2006, 09:11 PM
#1
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incorrect timing cause water reversion
Just put distributor back in . 30 minutes running time and realized timing light was faulty. New light corrected timing,timing was off about 15 degrees. Can this cause water reversion ?
05-04-2006, 10:47 PM
#3
Re: incorrect timing cause water reversion
Yes, it can affect it. It depends which way the timing was off. More advance at idle causes the following conditions:
1) Smaller throttle opening for equivalent idle speed resulting in higher manifold vacuum, which during cam overlap, causes more reverse pull on the exhaust.
2) Lower EGT temps measured at the exhaust ports. Not a direct reversion issue, but more temp vaporizes any water present.
Cam timing, overlap, and idle speed are by far bigger contributors to the possibility of reversion then timing at idle speed, but if already on the edge, it's worth taking a look at.
1) Smaller throttle opening for equivalent idle speed resulting in higher manifold vacuum, which during cam overlap, causes more reverse pull on the exhaust.
2) Lower EGT temps measured at the exhaust ports. Not a direct reversion issue, but more temp vaporizes any water present.
Cam timing, overlap, and idle speed are by far bigger contributors to the possibility of reversion then timing at idle speed, but if already on the edge, it's worth taking a look at.
05-07-2006, 07:34 AM
#4
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Re: incorrect timing cause water reversion
Falcon, Does this mean you can help lessen reversion by keeping idle speed up, programming (halltek fuel injection) a leaner fuel mixture at low rpm to increase egt, and trying to find a way to bleed off manifold pressure at idle? And is there any way to measure what the perfect idle speed would be to minimize reversion? Ratickle
05-07-2006, 04:06 PM
#5
Re: incorrect timing cause water reversion
Idle speed up, yes. Controlling both in gear and neutral idle speed is best.
Leaner fuel mixture, maybe, little if any misfiring is a must.
Bleeding off manifold pressure, ? what do you mean?
Idle speed, just trying it I guess. There may be others here that have more direct experience with specific cams that can help.
Leaner fuel mixture, maybe, little if any misfiring is a must.
Bleeding off manifold pressure, ? what do you mean?
Idle speed, just trying it I guess. There may be others here that have more direct experience with specific cams that can help.
05-07-2006, 05:36 PM
#6
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Re: incorrect timing cause water reversion
"1) Smaller throttle opening for equivalent idle speed resulting in higher manifold vacuum, which during cam overlap, causes more reverse pull on the exhaust."
I was wondering if it would be possible to bleed off manifold pressure at idle to eliminate all possible reverse pull on the exhaust. I know there would be some mixture issues etc. but on the Scorpion's 540's I have programmable fuel injection where I can compensate for almost anything on each individual cylinder. Just plug into the laptop, read egt, cam position, O2, etc. and adjust the fuel curve accordingly, then smooth out the individual cylinders for an average. Just curious of anything that allows larger cams for more power.
I was wondering if it would be possible to bleed off manifold pressure at idle to eliminate all possible reverse pull on the exhaust. I know there would be some mixture issues etc. but on the Scorpion's 540's I have programmable fuel injection where I can compensate for almost anything on each individual cylinder. Just plug into the laptop, read egt, cam position, O2, etc. and adjust the fuel curve accordingly, then smooth out the individual cylinders for an average. Just curious of anything that allows larger cams for more power.
05-07-2006, 08:51 PM
#9
Re: incorrect timing cause water reversion
Intentional leak to reduce manifold vacuum = higher rpm, this is what an IAC (idle air control) does to adjust rpm, just like the throttle plates being opened to change "air" intake. If you let in more air to reduce vacuum, you have to compensate with more fuel which then equals higher rpm.
Second question relates back to my first answer, yes, but remember that this only a small part of the equation. Number 1, Cam!!! Number 2, Water, Where!! Number 3, Idle RPM! And last is timing, because it can help slightly with manifold vacuum during the overlap and it raises the egt to help vaporize remaining liquid H2O. If you have a reversion problem and changing cams isn't reasonable, raise idle speed, then look at timing at idle. If your engine has computer control, remember to also look at how it maintains idle speed in gear. Some can use ignition timing along with an IAC to control idle speed. Relying more on timing for low speed rpm control can also affect reversion.
Second question relates back to my first answer, yes, but remember that this only a small part of the equation. Number 1, Cam!!! Number 2, Water, Where!! Number 3, Idle RPM! And last is timing, because it can help slightly with manifold vacuum during the overlap and it raises the egt to help vaporize remaining liquid H2O. If you have a reversion problem and changing cams isn't reasonable, raise idle speed, then look at timing at idle. If your engine has computer control, remember to also look at how it maintains idle speed in gear. Some can use ignition timing along with an IAC to control idle speed. Relying more on timing for low speed rpm control can also affect reversion.
05-07-2006, 10:26 PM
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Re: incorrect timing cause water reversion
'Bleeding' off manifold pressure is like creating an intake manifold leak which would cause a lean condition which would promote a backfire thru the carb which will suck exhaust gases(and water) back into the combustion chamber.
Worst possible thing to try to stop reversion.
Worst possible thing to try to stop reversion.
