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Thread: Timing effect on temperature at idle? retarded for cooler?

  1. #1

    Timing effect on temperature at idle? retarded for cooler?

    This is an odd question, how does timing at idle affect engine temperature(coolant/oil). My car idles flawlessly with a 230/250 cam all the way down to 8 degrees of timing and also idles great at 22 degrees of timing, obviously different sounds and rpms. I am curious for summer which way should I push it? I would imagine retarded timing runs cooler allowing more gas in the chamber before combustion, but before i go with trial and error, I figured I would just ask the experts. Thank you in advance

  2. #2
    I had a similar question= Is it better to run more timing and less airflow OR more airflow and less timing?

  3. #3
    I would take the answer to that question too, I am hoping a master tuner will comment with their best practice or thoughts.

  4. #4
    Big thing you want to look it is how much vacuum is being produced at those timing values. You want to run as much timing as you can to produce best vacuum at idle for your power brakes. Unless you have hydraulic brake assist, which doesn’t require vacuum for brake operation.

  5. #5
    Oh wow that's a first for me, but now i have something to target, hence if i understand correctly tune to max vacuum at idle. Thank you

  6. #6
    so running around 60kpa at idle is a good thing?

  7. #7
    The less timing you run, the later in the stroke the combustion happens, so in turn, it is going to shove that flame front further into the exhaust, which also, makes the engine less efficient, and as a by product generates even more heat.

  8. #8
    Advanced Tuner
    Join Date
    Feb 2017
    Idle timing...

    too retarded throws fire into the exhaust (and cooling system)
    too advanced at too low of an RPM (550-750rpm) will cause misfires when the fuel heats up (gasoline mostly) along with the engine

    because gasoline reaction rate is dependent on temperature, the hotter everything gets, the faster it tries to go,
    and imagine a very slow moving engine (550rpm) with a very advanced spark (~20* btdc) trying to get that piston up while the gas is expanding quickly from being so hot... it will make a "PFFT" sound and misfire/stumble

    When I first got my 5.3L running I used factory in-gear timing with OEM camshaft idle speed (18* and 550rpm)
    which is how I first became aware of this issue. It would misfire in gear randomly and was very annoying. I thought because the idle timing was set by the factory that it should be fine...

    wrong. With the timing set in gear at 550rpm with 12-13* it idles smooth as butter.
    Most engines however will have camshaft upgrades, higher idle speed, and better fuels, so this rarely applies.
    Typical idle timing for those engines IS in the 18* range and 680-750rpm
    Last edited by kingtal0n; 07-30-2019 at 11:31 PM.

  9. #9
    thanks kingtalon I'm running 18degrees at 850 rpm its ok for now but will revisit after I get this dang vve done. I was looking at the spark table and its telling me it wants more spark like 34-46 degrees at idle, that cant be right. am I giving it too much air?