Spark tables
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Joined: Jul 2016
Posts: 88
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Car: 90 iroc z
Engine: 358 tpi
Transmission: Auto
Spark tables
Can someone explain to me how and when i will know to adjust my spark tables. In other words what symptoms will let me know i need to adjust the tables .... How will i know i have"detonation"
Joined: Sep 2003
Posts: 25,895
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From: Pittsburgh PA
Car: 89 Iroc-z
Engine: 555 BBC Turbo
Transmission: TH400
Axle/Gears: MWC 9” 3.00
Re: Spark tables
In general,
idle timing you can adjust for desired vacuum (along with fuel afr) and idle stability. Big cam tends to want more advance. Advance can change idle rpm, so work with advance, desired rpm, and throttle opening/ iac counts to get to desired speed and conditions
part throttle you can try to monitor knock sensor to see if it detects counts. Or go by feel somewhat plus monitor plenum vacuum and throttle position % for desired cruising speed. Lowest throttle opening that shows lowest map value or higher vacuum amount that still maintains speed is desired. Should be the most power and efficiency. Else, you watch gas mileage. Proper fuel and spark yielding most mileage is desired. Ideally having cyl pressure monitoring would find best combination of fuel and timing
wot you need a dyno ideally. Keep goin up til power no longer increases, then back off 1 or 2 deg, or more depending how safe you wanna be. Power shows most pressure in cyl so as long as the knock sensor doesn’t detect anything, power is an indicator of proper timing.
If you can hear detonation you are way over the edge lol. And not all knock counts seen are real events so dont chase your tail.
idle timing you can adjust for desired vacuum (along with fuel afr) and idle stability. Big cam tends to want more advance. Advance can change idle rpm, so work with advance, desired rpm, and throttle opening/ iac counts to get to desired speed and conditions
part throttle you can try to monitor knock sensor to see if it detects counts. Or go by feel somewhat plus monitor plenum vacuum and throttle position % for desired cruising speed. Lowest throttle opening that shows lowest map value or higher vacuum amount that still maintains speed is desired. Should be the most power and efficiency. Else, you watch gas mileage. Proper fuel and spark yielding most mileage is desired. Ideally having cyl pressure monitoring would find best combination of fuel and timing
wot you need a dyno ideally. Keep goin up til power no longer increases, then back off 1 or 2 deg, or more depending how safe you wanna be. Power shows most pressure in cyl so as long as the knock sensor doesn’t detect anything, power is an indicator of proper timing.
If you can hear detonation you are way over the edge lol. And not all knock counts seen are real events so dont chase your tail.
Last edited by Orr89RocZ; Mar 27, 2019 at 08:15 AM.
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