Sea Level vs Altitude Tuning

[cleatus12r]

Here is the attachment screenshot.

[soutthpaw]

scratch this response I missed your comment on the previous page.... Ill read it then get back to ya

[soutthpaw]

its easier to see once i put it in the graph format. That sure is weird at 22C. Like I said before, it must be that way due to some boneheaded emissions testing. Bet it would not be as obvious if I was running 5w40 synthetic, which i will be switching too next oil change. so if i raised that to the 3C level or so the dead throttle should go away?

another question, if i change the negative multiplier in the Adder to Pulsewidth Multiplier would that increase the boost levels? I guess it would be more accurate to call it a subtractor to Pulsewidth Multiplier

[cleatus12r]

Originally Posted by soutthpaw

its easier to see once i put it in the graph format. That sure is weird at 22C. Like I said before, it must be that way due to some boneheaded emissions testing. Bet it would not be as obvious if I was running 5w40 synthetic, which i will be switching too next oil change. so if i raised that to the 3C level or so the dead throttle should go away?

another question, if i change the negative multiplier in the Adder to Pulsewidth Multiplier would that increase the boost levels? I guess it would be more accurate to call it a subtractor to Pulsewidth Multiplier

The thing I was trying to get at is that there is no pulse width multiplication above the stock values until the EOT is above 22 degrees C. Factor in that the low boost fueling is WAY LESS than stock at less than about 5 PSI and you have an absolute turd until there is some boost or until there is some engine temperature. You know that the accelerator pedal is even really "doggy" in stock when cold....well, it's even worse with this program due to the low boost fueling that has been taken away. If the numbers were to represent a percentage, there would be points of 10% less fuel in the Fuel Sipper program for any given boost/RPM combination.

You can put zeros or positive numbers in the "adder" map. It's not going to hurt anything. The PCM will not pull fuel under high boost.

[soutthpaw]

I knew I read it somewhere, It was in the infamous 80E thread at PSN posted by Swamps.

"Firehunter: higher altitude = less dense air, which in turn means lower cylinder pressures and temperatures during the compression stroke, delaying the start of ignition. Advancing the injection timing under these conditions allows the start of ignition to begin at a more "optimal" point in terms of crank-angle than if the timing was left at a more retarded setting.

About 4 years ago Tadd (now Elite Diesel) and I got together at his old shop in Alamosa, CO (7500' Elev.) for a week of cylinder pressure testing and tuning on his dyno. We provided the truck with a fully built engine and everything on it and he provided the tuning, pressure transducer and scope. When I returned to Nashville (500' Elev.) I found that I had to pull 5-10* of timing out of the timing table we developed.

Aggie: Exactly--the injection delay table allows the start of injection, but even more so the start of ignition, to occur at the desired point in the engine cycle regardless of temperature or ICP pressure.
The pressure exerted on the injector intensifier piston is a function of the ICP pressure minus the pressure drop through the poppet valve. Higher viscocity oil resists flow, giving a greater pressure drop, so you end up with less pressure on the piston."

I dont think I added more than 4 degrees anywhere on the high altitude timing over what Bill had as sea level.. but I did change the high altitude maps to match his sea level maps then tweak from there... I want to wait and see what Bill's comments are on the the topic before getting to carried away. On a side note, I noticed when I tried doing a straight copy and paste I got similar aberrations to the map images on that thread that Bill posted... and the anomaly was on the copy map not the map I pasted too... Interesting, no? Then it would give an program error and shut down some of the time.


OH, I didn't compare that file you posted the image from to the stock map so I need to take a look when I get a chance.. Also got my Bluetooth keypad today so that will make working with the 3D maps nicer..

[Power Hungry]

Originally Posted by cleatus12r

The problem with tuning the 7.3L is that there is no table ANYWHERE that sets start of injection. There are numerous factors that come into play and the the SOI tables are just another "modifier". Injection pressure control, engine oil temperature, boost pressure, etc. all play a part in when the PCM DECIDES to initiate SOI. It's not a simple "oh, 7 degrees BTDC is the "timing" and that's it." The PCM bases fueling rates and SOI on a large number of things.

Here's a hint as to why the timing table has a dip in it. Compare the MFD in the "ICP desired" map. See a trend? As the ICP ramps up quickly, the SOI takes a dip. Increased injection pressure actually advances the ignition point of the fuel in the combustion chamber due to better atomization and higher fuel rate (more fuel in less time).

Higher boost pressures in the higher RPM ranges affect the ignition point as well. More boost = higher dynamic compression = earlier ignition point. So therefore, a slightly less advanced SOI.

'Zactly! Especially the part about ICP vs. SOI. Most people don't catch that relationship and then wonder why their engines suddenly become air-cooled.

[Power Hungry]

Okay... time to wear my fingers out.

The first thing you may notice is that the SOI table (fn1200) is curved while the altitude table (fn1201) is (more or less) linear. This is because fn1201 is an altitude adder to the base SOI. The amount added is not constant, but instead is a percentage value based on altitude. To be honest, I don't have a definite explanation on how the percentage is calculated in relation to altitude which is why in most cases I leave it alone and work with fn1200 instead. I'd be inclined to think that calibrations that have had to remove timing when dropping to sea-level may have had both tables modified and the PCM could no longer compensate for the change in altitude.

The "dip" in the main SOI (fn1200) map, as Cody indicated, is because of the inherent shift in SOI due to the increase in injection pressures. It is quite complex how all the maps interrelate with each other and overlooking any one component in the process can result in catastrophic failure. This is why I try to keep changes as simple and as few as possible.

Consider this...

10 years ago the only changes we made to diesel calibrations were functions 1104 and 1204 and we made 100 HP. Many people in the tuning business complain that this is NOT the way to tune engines. Part of me agrees, and part of me disagrees. The agreement comes from the fact that there is no RPM compensation for SOI so you may end up with excessive SOI at lower RPMs in order to achieve the desired SOI at higher RPMs.

The benefits from using these tables are quite clear. Since these tables are related to EOT, you can easily control at what temperatures the modified power curve comes on and this helps prevent excessive power output when the engine is below operating temperature. Also, since the fuel table (fn1104) is curved based on ICP, you can maintain a stock profile at idle/low throttle and progressively curve the fuel delivery based on driver demand.

There is no clear cut explanation on how to properly handle tuning these processors because the dynamics of tuning these engines is a bit more complex than people realize. P-pumped engines have much fewer tuning issues because the relative pressure of the injected fuel doesn't vary nearly as much and the timing curve is constant. Of course, P-pumps are louder throughout the RPM range while HEUI engines are relative quiet in comparison.

Anyway, I hope this helps a little bit. I'll get a bit more involved in this discussion as I get caught up on orders.

Take care.

[soutthpaw]

How do I view the Maps by Address such as FN1200 I tried to select all, highlighting a single map etc and cannot get the view by address or ID to not be grayed out? for your explanation to make sense I need to look at those FN's and connect the dots, so to speak.
look forward to more of your explanation when u get caught up...

[Power Hungry]

Unfortunately, Addresses and Function IDs are disabled and I don't have any control over that. At some point, I can put the Function IDs in the description/name.

[soutthpaw]

which one is FN1204 the others u named in your previous reply

Also am I correct in thinking that the weird looking maps for stock are somewhat related to Ford trying to optimize for emissions reasons. most of your maps seem to be a lot smoother and more linear curves.. Which seems to make more sense to me...