advance 5 degrees

[ghostrider_23]

so I have been reading threads on mods and keep hearing about advancing the timing 5 degrees. I have 3 questions

What does the bike do or how does the bike react to this advancing?

How do you advance the timing, any step-by-step instructions?

Are there any other mods I would have to as a result of advancing the timing?

[plewis51]

Great write up and info in the wiki:
http://wiki.gstwins.com/index.php?n=Upgrades.IgnitionAdvancer

[Unsane]

What does the bike do or how does the bike react to this advancing?

To start with, ignition timing is normally slightly advanced in combustion engines due to the speed at which the fuel/air mixture burns - as the combustion gases expand the combustion chamber volume must be the correct size and already expanding itself so as to accommodate the incoming pressure from air/fuel explosion.

If the timing is not advanced enough (retarded), the combustion chamber will be too big for the explosion to effectively transfer its force into the piston
BUT
If the timing is too far advanced, the combustion chamber will still be contracting (as the piston is still traveling upwards) as the explosion occurs and this hammers the piston crown - known as pinging or knocking - which can over time destroy your engine.

On the same token, a lean air/fuel mixture burns faster and will therefore act in a similar way to over-advanced timing - whereas a rich air/fuel mixture will burn slower and act in a similar way to retarded timing.

So, in a perfect world with a stoichiometric air/fuel mixture and the correct timing, the combustion explosion will transfer its force into the piston in the most efficient way.




But we do not live in a perfect world 




The engine is almost every production vehicle is tuned to achieve a balance of power, economy and emission output and often one will come at the expense of another (especially given that emissions and economy are more important to the average punter). On top of this, especially with carburetted engines, it is difficult for the fuel/air mixture to be optimal for all climates - different altitude and temperatures inversely affect oxygen content in the air, thus affecting the oxygen content being drawn into your engine and while fuel injection can be programmed to compensate, carbys cannot - the result is that many carby-fed engines will be tuned on the RICH side so one engine can run well on cold days and hot days - at the beach and high up in the mountains.

The theory of advancing the timing by 5 degrees exploits this rich tuning - results will vary based on your geographic location (temperature and altitude) and the state of engine tune.

Note that ignition timing needs to advance as the RPM rises so given you are changing base timing by 5 degrees, this will have a different effect at low and high RPM. My bike felt torquier at lower RPM but flat at high RPMS, most likely due to the over advanced timing and insufficuent fuel to burn correctly.

How do you advance the timing, any step-by-step instructions?

As plewis suggests check out DIY turorial in the wiki

Are there any other mods I would have to as a result of advancing the timing?

Ensure your carbies are tuned correctly - maybe even jet them a little bigger

Its a slow day at work.

[burning1]

On the same token, a lean air/fuel mixture burns faster and will therefore act in a similar way to over-advanced timing - whereas a rich air/fuel mixture will burn slower and act in a similar way to retarded timing.

Good to know. My race bike has the stock jetting, which is a little lean from the factory. One of the only engine mods I've run is to install an ignition advancer, along with running higher octane fuel to reduce the chance of detonation. Plugs were white on inspection, as one would expect on a very hot running, lean engine. So, interesting to know that lean conditions interact with advanced ignition timing.

[Unsane]

Good to know. My race bike has the stock jetting, which is a little lean from the factory. One of the only engine mods I've run is to install an ignition advancer, along with running higher octane fuel to reduce the chance of detonation. Plugs were white on inspection, as one would expect on a very hot running, lean engine. So, interesting to know that lean conditions interact with advanced ignition timing.

Does your race bike ping if you don't use hi-octane fuel?

I owned a VL Commodore years ago (Australian car that uses a 3.0 litre SOHC version of the GTR Skyline RB family engine) and with programmable engine management and 98RON fuel, we advanced the timing up to 31 degrees before it started pinging - went from 90rwkw up to 114rwkw with fuel+timing and nothing more than an airfilter and gutted cat converter and it hauled ass (relatively speaking). There is a lot to be said for tuning an engine to suit basic mods!

[Unsane]

You would probably find the engine would run cooler with richer jetting and regular RON fuel - due to a lean burn being a hot burn. I would suspect the only thing stopping pre-ignition in your race bike would be the higher octane fuel!

[burning1]

I haven't noticed pinging with the race bike, but to be honest it can be hard to tell with wind and mechanical noise. Inspection of the plugs doesn't reveal any pre-ignition damage though. When the engine was completely stock, I'd run 89 when I had it handy, or 91 if I ran out of gas and had to buy it trackside (pretty typical for me. Yesterday I burned 7 gallons.) I switched to 91 knowing that advancing the ignition would probably cause knock with the relatively lean stock jetting.

I am planning to re-jet, install a few common mods, and dyno the bike.

I'm back and forth on how far to tune the engine. Race gas is readily available where I ride, but I'm not sure adding several hundred dollars a year to my fuel bill is viable.

[mass-hole]

I was running 93 in my bike since I got it, installed the advancer about a month after I got it, then at some point I tried putting 87 in it when I was trying to be cheap and the bike ran like crap for the entire tank, I am assuming it might have to do with the advancer. Never ran the bike on 87 before the advancer so I dont know how it would have run.

[centuryghost]

I have the V&H advancer, jetted up one size from stock and run 87. No pinging and a noticeably stronger pull in the lower range. I find no reason not to do it.

[ASUDave]

One thing I'm not clear on with the advance is, can it be done on newer bikes? It seems most of the info on the wiki is for older bikes.

btw, I have an 09. I don't plan to do the 5* advance yet, but wonder if it can be done on the newer bikes.

[jfoley]

I have an 01, interested as well.

[Unsane]

Mine is a 2004 and the advance mod works exactly as described

The the baseplate mounting screw holes get elongated allowing the entire baseplate to be twisted slightly - the ignition pickup is attached directly to the baseplate so any movement will affect the point at which the "chopper" passes the pickup - thus affecting your ignition timing.

I found a noticeable difference in low end torque, throttle response and better idle (when warmed up) but top end power did seem to suffer. I wish I still had access to a dyno!

[Unsane]

Can I ask a question though...

In Australia, the three grades of fuel available at petrol stations are

• Regular - 91RON
• Premium - 96RON
• Ultra Premium - 98RON

What octane rating fuel are you getting at the pump over in the States?

[burning1]

We use RON+MON/2

Common fuel ratings are 87, 89, 91. AFAIK, they are more or less the same fuel as what you have.