gsxrred1000

iTrader: (3)

Where do you start making changes in the tune as far as timing on c16 over pump gas?

Also will it hurt to still spray water/meth on top of c16 ?

Air/fuel should still be 11.0-11.5 on c16 ?

Any other changes that should be made when swapping fuel out ?

Thanks Travis

pantera_efi

iTrader: (1)

Hi GSX, the Stoichiometric AFR of C-16 is 14.82.

This is NOT an "oxygenated" fuel as is pump gas in most cases. (your area ?)

You will find 12.5-12.8 is the best AFR OR with a EGO/UEGO (Lambda Read) it will be the same. (.893-.902)

The C-16 weighs less .760 pump/.735 C-16 SG

Most will state a +6 degree at WOT over pump gas.

This is when your Pump Gas timing is correct.

I would like to know your C.R., MAP, and current Spark Advance Values ?

Lance

gsxrred1000

iTrader: (3)

Pumpgas and 50/50 meth/water my timing is 10 degrees at wot on 20 psi
Compression ratio is 9.9:1 if I'm correct. L33 rotating assembly in gen 3 iron block with standard 5.3 ho headgaskets. 799 heads.

gsxrred1000

iTrader: (3)

See if this pic helps. Still shot from my phone while I was tuning. This is pumpgas/meth tune.

kingtal0n

iTrader: (1)

timing map is rough, timing shall gradually increase from idle region into cruise portions. Full cruise timing by 2400-2800rpm is traditional (later on higher compression engines). IMO yours is too early, and too abrupt.

the question you are asking is custom, it requires time on a dynometer and/or race track to "dial in". Usually I start around 15* when switching from a 10* (~15-18psi of boost often times) Pump gas map to C16 fuel, and then try +2 and -2 on a dyno to see where it wants to be. Its just for the dyno pass in those cases (most of the time we just want to see how much power the engine will make, then turn it back down for pump fuel). Other times its for a race car so the dyno is not ideal; you would rather run the car, make the changes, run it again, etc.. because weight, and rate of change in engine loading are factors that alter racing character and the dyno may actually screw the car up (it won't race as well) when its tuned for max dynometer output.

pantera_efi

iTrader: (1)

Hi GSX, I would try 16* at WOT (20 psi).

What King stated is correct, with a track report of your Inlet Air Temperature (MAT) after the turbo/intercooler ?

DO you use an intercooler ?

Lance

gsxrred1000

iTrader: (3)

Yes 4" eBay intercooler. 3" pipe from turbo to intercooler and intercooler to TB.
Usually see an increase from 90 degrees to 130 on full 1/4 mile pass with pump gas meth at 20 psi. Have never seen higher than 130 inlet temp. So 16* at 20 psi from like 3k rpm to 7k and maybe pull 2 * @ peak torque ?

gsxrred1000

iTrader: (3)

Can you show me a picture of what u mean as gradual to cruise timing ? Been trying to help spool time from off idle to full boost and that's why my lower timing is so high. Not sure how much I can get away with down low and how soon to blend it in.

kingtal0n

iTrader: (1)

gradual means gradient, it could be an infinite number of steps gradually approaching a number. There is a function in the stand-alone called "interpolate" and if you selected the entire map, or parts of it, you can interpolate to cause a "gradient" of numbers.

Before computer control, distributors spun with engine RPM and timing would advance as RPM rises due to some centrifugal weight inside the distributor. This is an approximation, using "safe" timing numbers to gain a feature called "safety factor" or probability to be reliable, thus the ability of the distributor to properly time the engine 100% of the time is lost (the wrong timing numbers are used sometimes) but the engine will still be reliable because timing is below some threshold we have determined where the engine should still run safely (non optimal but safe is fine in 1975).

Advance curve for a distributor that can use different springs to custom tailor the curve:
[


The beauty of computer controlled timing is now we can put timing in places where distributors normally wouldn't be able to tell we wanted timing (or remove timing). It isn't just the engine we are timing for, other factors such as how the vehicle is used are more important. For example if the engine is for professional sponsor racing it would have been engine dyno'd prior to being installed into a vehicle on the fuel choice. It may have even had copies of itself made and put aside so we are not testing the actual engine going into the boat. Then there is the daily driver aspect, long miles gives a lot of time for things to change electrically, it could be something as small as the voltage supplied to the coil that changes the ideal setting for dwell in one particular region of the timing map. So that means if your ECU doesn't have a good dwell map for non-ideal voltages you could wind up changing the battery and suddenly be several degrees off in the timing map.

Picture2: dwell


Where do those numbers come from? What coils are they for? Did they get corrupted somehow? Why do different tunes for engines using the same coils have different dwell numbers? How do you test what is "ideal dwell"? Is the timing on the engine you are tuning staying where it should be at 8,000rpm?

We can think of many scary questions, but the truth is, even if you see the correct number and know from experience that number is usually the right one, it doesn't necessarily mean the computer is actually using that number. Dwell setting can undercharge or overcharge a coil which may cause premature spark or a weak spark, however unlikely. The symptom of overcharging coils would probably be broken pistons. The symptom of undercharging coils might be poor fuel economy, fuel smell while running increased, poor carbon deposits increasing, and requiring more and more WOT advance. We might wind up with undercharging coils at WOT using 32* of timing, not realizing that if there was a 4.5 instead of a 2.5 in a line of cells somewhere it would be 24* instead and the engine would Crispen up, make more torque, and the air fuel ratio would even change on the wideband even though no more fuel was being injected (less unreacted oxygen means a richer a/f ratio usually). A weak coil is just one of the paths to a dirty cylinder and poor combustion, it could be the plug, wires, coils, dwell, wiring, voltage, or even the design of the head or the conditions present during the reaction. Imagine you have a water injection system leaking water unknowingly during idle into the intake. It winds up cooling the valves and head enough to prevent the already sloppy large injectors we are using from giving a nice evaporated mixture. In the past it was fine because the valve and head would heat up enough to evaporate the fuel but now we have poor combustion quality due to the local temperatures being wet down to water's preferable range of 212*F steam production, whereas the fuel would probably behave itself much better at 400*F. The point here is that dwell is the least of our concerns; there are plenty of other ways to wind up with a poor performing ignition system. IMO I feel like chevrolet kind of took most of the guess work out of it since there are so many performance engines using oem coils, so this platform at least is blessed with that. To re-state the point another way, there are many aspects which are "contained" as a factory given (like the OEM coil and OEM dwell settings in the computer, are "given" to us) that we don't really know how to account for or wouldn't want to account for (you wouldn't want to change or re-design the oem coil and you wouldn't want to mess with the OEM dwell setting right off the bat if it was your only engine and you are on a budget) Instead, lets focus on the intricacies of timing that we can account for.

Intricacies of timing that we can see coming and account for:
Timing is exactly personal so each change is different depending on the engine, but, generally:
1. rising 'boost' (increasing pressure) generally means reducing timing, regardless of the fuel type, as reducing pressure (vacuum situation) means advancing it
2. reducing timing on a dyno to correlate an EGT spike with significantly reduced torque gives us a lowest point to start from
3. The region of the map that leads into 1st gear boost situation can be customized to spool a turbo faster
4. Fuel type and vehicle use are the largest factors when trying to find ideal timing per the application, i.e. boat engines get stuck at one specific RPM for an hour so knowing optimal timing becomes far more critical than when the engine is only briefly passing through that region.
5. If VE is falling off as engine RPM increases then injector pulse is also falling off (even as duty cycle is increasing, this is one way to detect a falling torque curve without a dyno, by using the wideband) and more timing could be added (Thanks to the reduced VE)
6. The colder the engine parts are, the more timing we can usually use safely. IAT might pull fuel when things get hot- but it doesn't increase timing. It pulls both fuel and timing. CTS does the same thing. Hotter engines are more efficient; we want it hot when we cruise, and idle, part of the reason we need less timing to begin with. But during WOT the high temp works against the fuel quality, when we goto WOT, suddenly we would prefer a cool engine. Methanol does an incredible job of giving you this 93 pump gas duality. An engine running 93 will get hot, efficient as it can (for such a cheap liquid) and economy is peaking. Then, add methanol when you want the WOT condition to be cool.


there are probably a lot more this is just off the top of my head to show that we DO have some control over the situation and need to actively think about what is happening inside the engine.


Now lets examine the an exact vehicle. Each map is unique for that vehicle because weight and rolling resistance, rotating parts mass, exact final gear ratios, and the engine VE in that region will all have a say. For cruise timing, you would want to put the vehicle in final gear, drive along at the minimum cruise speed and note the engine RPM there. Find that spot, going uphill, so there is MORE load on the engine, you watch where the map reads from. Its different on every vehicle. You look at all the cells AROUND that area- the one before especially, because we always think of the cell as only having part of the say (its almost always touching multiple cells at once, the ones nearby...) In that spot you have discovered you will put the max cruise timing acceptable. What is max acceptable cruise timing? If I was going to guess a number it would be between 38* and 45* for modern, after 1995 engines. How can we find it? Such a thing is possible, you will data-log the cruise situation and record vehicle MPH, Engine pressure, and injector duty cycle. You will repeat the experiment at various speeds and timing numbers. The result which leads you to the highest speed with lowest injector duty cycle and best engine vacuum wins. It should also correlate with lowest EGT, but not always, since the VE of the engine being very high with a lean air fuel ratio can sometimes give us good economy with a higher EGT than a richer air fuel ratio with more engine vacuum (less VE) which gives us a lower EGT but also uses more fuel.

In general, For cruise timing it is often acceptable to follow a 'distributor' trend, where some max number peaks between 2400-3200rpm and stays there until out of cruising territory (once you pass 4000rpm in final gear you are often no longer "cruising" regardless of how much engine vacuum reads, so we often reduce timing for increased safety factor.)

kingtal0n

iTrader: (1)

Engines are so similar that, here is a timing map for a 2jz-gte, We could use this map in the LSx platform, on a stock engine up to 14psi of boost, with a fair margin of safety on a same weight vehicle.

I am posting it to show "gradual" into cruise timing, examine the map and notice:

1. until 1000rpm timing is 15-18 above -5" of vacuum, fairly flat for stability. It is ok to use the same number around the idle region to stabilize the engine. The computer often has it's own "idle timing stability feature" which would prefer to work from a solid base to begin with (same number across the board in the idle region) since rapidly changing numbers in the timing map will have consequences for the computer's prediction algorithm-timing output to try and stabilize the idle rpm.
2. timing gradually increases as rpm rises until around 2500
3. lets look at one row of vacuum: 16 18 18 22 25 28 32 36 38 38 ...

see how it does not abruptly move from 18 to 32 or something ridiculous (compare to the map you posted)