Full story on "Advanced Timing"
#1
10-13-2010 | 12:05 PM
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Senior Member
Joined: May 2008
Posts: 591
From: Farmer City, IL
Full story on "Advanced Timing"
I've heard bits and pieces about the advanced timing mod.
I have read up on how to do this, fairly simple.
Just wondering what excatly it does, and what are the risk, challenges in doing this.
Any help is muchly apprieciated as always.
I have read up on how to do this, fairly simple.
Just wondering what excatly it does, and what are the risk, challenges in doing this.
Any help is muchly apprieciated as always.
#2
10-13-2010 | 02:10 PM
Senior Member
Joined: Nov 2008
Posts: 2,726
From: southern New Hampshire
"Fairly simple..."
For cars with good old fashioned distributors, yes, advancing timing was easy, however, in this day-and-age; you typically need to reprogram the ECU to advance the ignition timing. Not so simple.
In generic terms, advancing the timing changes the point prior to each cylinder's TDC where the spark event occurs. Such an advance will start the flame front moving through the air/fuel mixture earlier, and as such, there will be more a higher pressure/temperature achieved at TCD and again at what I'll call the Peak Pressure Point (PPP) which typically occurs somewhere between 17 and 20 degrees after TDC. Assuming the fuel used has sufficient anti-knock properties (aka detonation resistance), the engine will eeek a tad more power (higher heat/pressure at the PPP translates directly to more power) from any given amount of air and fuel, and that will translate directly to more power in full power applications or better fuel economy in lower power applications.
Detonation; plain and simple. When the temperature/pressure at the PPP is higher than panned by the engine designers, detonation (spontaneous combustion of small (or not so small) pockets of "end gas") may result. Light detonation is typically considered harmless (even desirable by some), but things can quickly get out of hand and engine damage can result.
In a modern car, the challenge is to get the programming correct so that the ECU pays attention to the detonation sensors and keeps the air to fuel mixture properly balanced and the ignition timing retarded just enough to keep the engine on the ragged edge of disaster (i.e. at the point of incipient detonation).
I suspect (but cannot prove) that most (if not all) modern ECUs are flexible enough to be programmed (by the manufacturer and in a few cases by third parties) for any given fuel mixture, at any giving ignition timing, for any given fuel grade, at any given compression ratio, and optionally with any given amount of external boost. The problem here is that given the highly dynamic nature of modern automobile engine operation, the mixture, timing, fuel grade, compression ratio, and boost pressure; building an ECU with a fast enough processor to keep all of the variables dynamically in play, keep the engine working as efficiently as possible and to prevent it from blowing itself up might cost more than the manufacturer is willing to spend on millions of cars. What we get instead is an ECU with preprogrammed mapping that kinda-sorta keeps things in check, assuming the engine is operating as the designers intended. Change something like the timing and your ECU may not be able to keep up.
#5
10-15-2010 | 01:04 AM
Senior Member
Joined: Jan 2006
Posts: 3,183
From: Aberdeen, MD
what you are doing is moving the crank position sensor, the sensor determines where the cylinders are and based on how close it is to top dead center it fires a plug, moving the slider up retards the timing, moving it down advances timing. there are no marks as to tell how much you have changed your ignition timing, if its too much (hopefully) the ecu will pick it up and either run in a default setting or just pull timing back enough. ecu reprogram is not part of this mod nor is it needed, as long as the sensor is in the correct range the ignition timing will stay that way.
i have done this mod about 3years ago, and up until about 4 months ago i got the chance to see where the timing was at as well as the emissions via a 5gas analyzer. Lets just say im glad they dont do 5-gas on OBDII vehicles, turns out im running on the lean side, a little bit too much, and my timing is 13degrees advanced. I dont remember what gas i had in there at the time but you want to either mix low grade with mid-grade gas, or just straight mid grade. Ive been running 65k miles like that on regular, mid grade, mix or whatever, no problems.
i have done this mod about 3years ago, and up until about 4 months ago i got the chance to see where the timing was at as well as the emissions via a 5gas analyzer. Lets just say im glad they dont do 5-gas on OBDII vehicles, turns out im running on the lean side, a little bit too much, and my timing is 13degrees advanced. I dont remember what gas i had in there at the time but you want to either mix low grade with mid-grade gas, or just straight mid grade. Ive been running 65k miles like that on regular, mid grade, mix or whatever, no problems.
#7
10-19-2010 | 08:25 PM
Senior Member
Joined: Jan 2006
Posts: 3,183
From: Aberdeen, MD
This is where my whole hate for electronic throttle bodies comes into play. If you dont know, even if you slam the pedal to the floor the throttle plate gradually opens it never snaps, the difference is...well throttle response no, pick up yes just a tad in the lower rpms
#9
10-20-2010 | 12:58 PM
Senior Member
Joined: Jan 2006
Posts: 3,183
From: Aberdeen, MD
well its free, easy, wont cause damage, car will still be slow. ill put it to you in a different way, if had really know how slow the car was and how much you have to do to make it quick....no i wouldnt of bothered, its just something to do