itsdaveonline

How much timing are you running?`
Just curious on how much timing you guys are running near WOT. Feel free to post up your entire table if you want.

Seems my LS2 does not like any more than 26 Deg on 91 octane and 52xxft elv. I'm wondering how much more timing i can toss in with 100 octane.

I've heard of GTO's and vettes running more, but maybe the weight of the CTSV is causing much higher loads and more prone to pre-ignition

HCI2000SS

iTrader: (2)

I have a 6.0 in my Camaro and it likes 26 at WOT as well. Before the Fast I take it was at 29

itsdaveonline

I can't seem to run any more than 26 without picking up trace amounts of knock retard. I guess that sounds about normal though! Cam is a 111lsa too, so that's not helping.

Did ya happen to know what the stock values were for that car?

HCI2000SS

iTrader: (2)

No sorry I don't recall. Mine was the same way...any more than 26 and it was starting to knock

Naf

iTrader: (1)

Why not put it on a dyno and find out properly. Too many factors effect timin.

Iat
Oil deposits
Coolant temp
Elevation
Fuel
Etc

18-24 is a good range which you can test on the dyno.

Too much timin and you could be losing power...

vmapper

iTrader: (8)

^^ This ...
Increase timing until you no longer make any more power... then you know how much timing you should run.

I usually find that a dip is made 3500-4400 rpm for the max TQ, then can ramp up timing. on stockish LS6/LS2's would end up between 24-28° on 91 pump (NO added ethanol - E10).

IF the ability to increase power from 91 octane is there.. may not be relevant to add more timing.

DMM

An efficient chamber design, as the 243 heads are equipped, do not require or benefit from excessive ignition advance.

The faster the flame travels across the chamber by design, the less need there is for it to get a head start by lighting the mixture sooner through ignition advance.

07CTS-V

iTrader: (6)

I run 34* on 93 and 40* on a 50/50 93/Cam2 mix.

itsdaveonline

34 degrees? Wow that seems like alot for 93. What mods do you have?

And for the dyno comments my car has been on one and it did not gain any more power past 26 it only increased knock retard counts. It's also worth mentioning we reduced the amount of timing being pulled by iat temps by a good amount.

Im wondering if people haven't touched that table and increased main timing only to have it pulled in real time by iat. My main timing table is only a degree or so higher than stock.

Naf

iTrader: (1)

I left my iat tables alone, for once you get over 30c you have to pull timin to save your engine. If you dont want the ecu to pull timin then add a meth kit and activate it after 25c.

07CTS-V

iTrader: (6)

I had a low compression 427. I report actual timing as datalogged. I don't pull timing until about 120*-ish IAT, or coolant temps over 230-ish, half the knock sensitivity, double the retard attack rate, lowered max retard....


On stock cam and bolt on LS's I am generally around 24* and H&C ones around 27-28*.

Itsdaveonline - I was reading some of your EOIT threads, some good stuff in there. That's part of the secret for huge cam tuning.

itsdaveonline

Ah okay that makes more sense with a low comp 427. Figured you were stating actual observed timing. But wanted to go apples for apples comparison.

I forget when i pull timing but i think i start pulling 1-3 deg around 100-120 iat then it gets much more aggressive and closer to stock at higher iat.

Yeah i think that eoit adjustments have helped. I only messed with it up to 2000 rpm. I actually advanced mine up to 29 deg and it seems to help with surge and low rpm cruising. Im waiting on more people to test before i mess around any more lol

How come you reduced sensitivity? Was it due to LT's and stiffer springs?

itsdaveonline

Naf 30c = 86 f. Pulling timing at those temps seems excessively conservative. Just my 2 cents. Not saying your right or wrong.

07CTS-V

iTrader: (6)

Yes, plus stiff motor mounts.

Naf

iTrader: (1)

I am running high compression, even though i have a cold air intake i dont fool with the iat table. I rather lose a fee ponies than my motors..

07CTS-V

iTrader: (6)

That's one way to look at it. Another is if your total timing is correct and you motor isn't affected until the iat is 130*, why pull timing before then?

Naf

iTrader: (1)

Curtisy of innovate motorsports
Tuner Resources
Spark Timing Myths Debunked

A widely-held myth is that maximum advance always means maximum power. Here’s what’s wrong with this thinking:

The spark plug ignites the mixture and the fire starts burning. The speed of this flame front depends on the mixture, this means how many air and fuel molecules are packed together in the combustion chamber. The closer they are packed together in the same volume, the easier it is for the fire to jump from one set of molecules to the other. The burning speed is also dependent on the air-fuel-ratio. At about 12.5 to 13 air-fuel-ratio the mixture burns fastest. A leaner mixture than that burns slower. A richer mixture also burns slower. That's why the maximum power mixture is at the fastest burn speed. It takes some time for this flame front to consume all the fuel in the combustion chamber. As it burns, the pressure and temperature in the cylinder increases. This pressure peaks at some point after TDC. Many experiments have shown that the optimum position for this pressure peak is about 15 to 20 degrees after TDC. The exact location of the optimum pressure peak is actually independent of engine load or RPM, but dependent on engine geometry.

Typically all the mixture is burned before about 70 deg ATDC. But because the mixture density and AFR in the engine change all the time, the fire has to be ignited just at the right time to get the peak pressure at the optimal point. As the engine speed increases, you need to ignite the mixture in the combustion chamber earlier because there is less time between spark and optimum peak pressure angle. If the mixture density is changed due to for example boost or higher compression ratio, the spark has to be ignited later to hit the same optimal point.

If the mixture is ignited to early, the piston is still moving up towards TDC as the pressure from the burning mixture builds. This has several effects:

The pressure buildup before TDC tries to turn the engine backward, costing power.
The point where the pressure in the cylinder peaks is much closer to TDC, with the result of less mechanical leverage on the crankshaft (less power) and also causes MUCH higher pressure peaks and temperatures, leading to knock.
Many people with aftermarket turbos don't change the spark advance very much, believing that earlier spark creates more power. To combat knock they make the mixture richer. All that happens really then is that the mixture burns slower and therefore hits the peak pressure closer to the right point. This of course reaffirms the belief that the richer mixture creates more power. In reality the flame front speed was adjusted to get the right peak pressure point. The same result (with more power, less emissions and less fuel consumption) could be achieved by leaving the mixture at the leaner optimum and retarding the ignition more instead.

Turbo charging or increasing the compression ratio changes the mixture density (more air and fuel molecules are packed together). This increases the peak pressure and temperature. The pressure and temperature can get so high that the remaining unburned mixture ignites by itself at the hottest part in the combustion chamber. This self-ignition happens explosively and is called 'knock'. All engines knock somewhat. If there is very little unburned mixture remaining when it self-ignites, the explosion of that small amount does not cause any problems because it can't create a large, sharp pressure peak. Igniting the mixture later (retarding) causes the peak pressure to be much lower and cures the knock.

The advances in power of modern engines, despite the lower quality of gasoline today, comes partially from improvements in combustion chamber and spark plug location. Modern engines are optimized so that the flame front has the least distance to travel and consumes the mixture as fast as possible. An already burned mixture can no longer explode and therefore higher compression ratios are possible with lower octane fuel. Some race or high performance engines actually have 2 or three spark plugs to ignite the mixture from multiple points. This is done so that the actual burn time is faster with multiple flame fronts. Again, this is to consume the mixture faster without giving it a chance to self-ignite.

Higher octane fuel is more resistant to self-ignition. It takes a higher temperature and pressure to cause it to burn by itself. That's why race fuels are used for engines with high compression or boost. Lead additives have been used, and are still used to raise the self-ignition threshhold of gasoline, but lead is toxic and therefore no longer used for pump-gas. Of course a blown engine is toxic to your wallet.

07CTS-V

iTrader: (6)

I didn't read all that but it was stated several times above that we dyno tune our own cars and tune for max power, not timing.

Motown Cad

Okay showing my ignorance here but how do you set your timing? with a laptop going into the obd2 port? Dyno? Or what?

InfrareV

You'll typically do this using a laptop with the appropriate software(HPTuners, EFILive). The software company will provide you with an ODB2 interface that allows you to modify the factory tune including the timing tables.