[JDP Sales]

Originally Posted by cwl011

NPP start wide open all the time, however on cold days it will be loud. You have to remember that the colder the gas is the harder it is to atomize. This will result in a longer harder cold start.

Not true. If you put it in stealth mode in the exhaust menu, it will start closed. Its the only mode in which it will start closed.

All the best,

Jared Royce
801.545.4215

[bhavyas]

Originally Posted by JRS

Here's a (bad) pic of the table for startup timing. The number across the top is the engine coolant temp, the number up and down is the engine run time. The number's in the graph represent the timing taken out of the base timing as far as I know, please correct me if I'm wrong.

If you have a tuner you can adjust these settings to have that roar even when it's hot but the reason they don't do this is it make it harder for the starter to turn the engine over. It's harder to turn over because when you retard the timing the engine fires before top dead center which makes the engine kick back but when it is cold like someone said fuel doesn't atomize so you need to light it off sooner (retard timing) in order to get the engine to start and run.

Thanks for this.. little confused after reading the description thoug..

Not sure what you mean by timing taken out of base timing? Any article you can point out to help understand this better?

[Modshack]

Originally Posted by raptor5244

Yeah, that is pretty typical. Like JRS mentioned the ECU has to use all its sensors to manage the fuel injection process. If the engine is cold you need more fuel, timing changes, higher idle rpm and you run in open loop mode for a bit until the O2 sensors warm up enough before the ECU switches to closed loop. You will then notice the idle come down and things quiet down a bit into a nice exhaust burble. So, if you engine is still warm when you go to start it again next time then the ECU make not need those more aggresive cold start settings, which will reduce the initial bark of the start-up exhaust note. It is still there, just not quite as loud.

This...

[JRS]

bhavyas, I will try to explain what I mean as best I can.

This isn't the Camaro's numbers but this is an example. Most chevy's run about 20 degrees of base timing which is 20 degrees before top dead center that the engine fires, this is 20 degrees advance because it is before top dead center (btdc). The computer retards the timing when it's cold to light the fuel off better because fuel doesn't atomize or burn until the fuel is hot enough to evaporate, remember fuel vapors are what ignite.

If you look at the graph in the pic it shows 14.8 at 32 degrees temp which means it takes 20 -14.8 degrees which means the engine is running at 5.2 degrees before top dead center which is retarded from the base timing of 20 degrees.

Some people may understand when I say with an old distributor if you turned the cap and it retard the timing (after top dead center) the exhaust gets hotter and the engine makes a lot of noise because your firing the fuel off after top dead center which means you fire closer to the exhaust valve opening or when it's open.

I hope this helps because you could have a whole forum on just timing on these Camaro's because of the direct injection and emissions.

[bhavyas]

Originally Posted by JRS

bhavyas, I will try to explain what I mean as best I can.

This isn't the Camaro's numbers but this is an example. Most chevy's run about 20 degrees of base timing which is 20 degrees before top dead center that the engine fires, this is 20 degrees advance because it is before top dead center (btdc). The computer retards the timing when it's cold to light the fuel off better because fuel doesn't atomize or burn until the fuel is hot enough to evaporate, remember fuel vapors are what ignite.

If you look at the graph in the pic it shows 14.8 at 32 degrees temp which means it takes 20 -14.8 degrees which means the engine is running at 5.2 degrees before top dead center which is retarded from the base timing of 20 degrees.

Some people may understand when I say with an old distributor if you turned the cap and it retard the timing (after top dead center) the exhaust gets hotter and the engine makes a lot of noise because your firing the fuel off after top dead center which means you fire closer to the exhaust valve opening or when it's open.

I hope this helps because you could have a whole forum on just timing on these Camaro's because of the direct injection and emissions.

Hmm... very interesting.. the only reason I kept prodding was because I love understanding the mechanics of the car works.. and you know what I just discovered... my concept abt retarded and advanced timing was wrong.. so thanks for that explanation!!