new $EE tuning thing!

[steveo]

Yep, I agree the goal is to get to MBT, and I do have concerns about too much advance, or at least more advance than what's really necessary...without a dyno it's really tough to tell what's perfect, and then even if you do, it's only for a certain point on the timing map.

as far as efficient timing advance goes, due to its combustion chamber design and unique cooling system, you'll find that under light loads, the lt1 has a particularly wide flat area between the two timing advance points of 'just enough timing to burn everything' and 'too much timing, and power loss starts'.

really big. in terms of power and feel, on my car i could -barely- tell the difference between 35 and 65 degrees in cruise range. but you could see it on a vacuum gauge for sure, if you held steady throttle and varied timing.

don't be afraid to experiment with a crapload of timing in cruise range. the combustion temperature and stress on internal components is very low when the engine is unloaded. a bit of detonation will not blow stuff up or melt pistons if you aren't running like that for hours. in my experience your car will protest with surging and bucking and feeling 'strained' way before it hits the point of knock anyway.

your experience may vary.

[Thatdudeorion]

as far as efficient timing advance goes, due to its combustion chamber design and unique cooling system, you'll find that under light loads, the lt1 has a particularly wide flat area between the two timing advance points of 'just enough timing to burn everything' and 'too much timing, and power loss starts'.

really big. in terms of power and feel, on my car i could -barely- tell the difference between 35 and 65 degrees in cruise range. but you could see it on a vacuum gauge for sure, if you held steady throttle and varied timing.

don't be afraid to experiment with a crapload of timing in cruise range. the combustion temperature and stress on internal components is very low when the engine is unloaded. a bit of detonation will not blow stuff up or melt pistons if you aren't running like that for hours. in my experience your car will protest with surging and bucking and feeling 'strained' way before it hits the point of knock anyway.

your experience may vary.

Yeah, this has been pretty much my experience exactly, and I have tried to use the MAP readings to get it dialed in, and I think without a steady state dyno we're probably just going to have to accept 'close enough' particularly in my case as I don't think there's more than 500' of contiguous level roadway, and heck, even if there were, I still don't know how close I could get it, as even at closed-throttle idle, the MAP readings jump around quite a bit whether you're tweaking timing or not.

[atlantadan]

I've got a Caprice with the LT1 and try as I might, I can't get this program to work. It errors out every second or so, and then logs an issue with the data stream. I'm going to start pulling the same fuses I pull to flash using TunerCat (which works), but does anyone have any other ideas?

[steveo]

if you can find out specifically what fuse you have to pull to get it working, that might be a start to us figuring out why it just doesn't work on some b-bodies.

some experimentation is definitely required to help get this working, as nobody with programming ability that uses eehack seems to own a b-body.

[91ss]

Steveo, are you familiar with the downshift pressure modifiers? Trying to figure out if what the units are in, PSI? And if positive values increase pressure or the opposite. The few bins i've looked through tend to have values go negative as the MPH go up. Wonder if it's like Ford's EPC where the more you reduce the current, the higher the pressure goes. It's also interesting that the most of the bins only populate only the 3-2 shift table and not the other two.

[steveo]

Steveo, are you familiar with the downshift pressure modifiers?

not a question for me, i don't really work with the auto trans end of stuff..

[lionelhutz]

The values in the pressure tables are not the line pressure in psi. They are just values from 0-96 which represent the minimum to maximum possible line pressure. All of the various applicable "psi" values are all added together and then used to lookup the force motor current in the force motor table. A look at the code would be required to confirm, but in theory the modifiers should all just add to the main pressure table value and a higher final answer would command more line pressure.

The tables are likely used to create a smoother shift. The performance applications typically seem to only have non-zero values in the 3-2 table. This could partly explained because of 2nd gear using the 2-4 band. The pressure might be dropped so the band doesn't bite too hard and make the shift abrupt. Bands can be trickier to apply because once they start to grab enough mechanical action takes over and makes them apply harder and harder.

But, it could also just be because low speeds in the gear mean low rpm's so when you kick it down the converter is flashing and putting the maximum torque into the transmission hence upping the line pressure. Then, at high speeds the converter is closer to locked so no torque multiplication and you want a softer shift.

[91ss]

Yeah,didn't think it would be psi. Good info the range.
Like the Ford EPC, the values relate to the current going to pressure control. The higher the current, the more the control closes off which reduces pressure. No, current - full pressure.. aka a failsafe if something goes wrong. I'm thinking the tables and force motor might work the same way. The cop and towing caprice bins have more negative values sooner.

[atlantadan]

if you can find out specifically what fuse you have to pull to get it working, that might be a start to us figuring out why it just doesn't work on some b-bodies. some experimentation is definitely required.

I pulled the SLS underhood fuse, and the #15 AC/DRL, and #25 air bag fuses in the main panel. That stabilized it a LOT and made the program useable for datalogging, but it still errored out. I'll continue poking. Those are the exact fuses I have to pull to use TunerCat to flash in this wagon.

[steveo]

the 'debug' screen should print the result of the comm errors, might give us clues?