Subaru Impreza GC8 & RS Forum & Community: RS25.com - View Single Post - DIY: ProjectLambda Stock ECU Reflash Tuning (Master Reference Thread)
View Single Post
Old 08-23-2016, 09:51 AM  
ImprezaRSC
2.0L Turbo
 
Car: 2000 2.5RS BRP
Fav Mod: 8 SEMA awards.
Join Date: Jul 2004
Trader Rating: (2)
Posts: 1,170
Default

I'll see if I can explain some of the finer points of E85 tuning with this software. (Forgive me if I go in a few circles. You will have to read this a few times to get it.) Mike is great about customer support, but these little things could use a bit of explanation in print. Cleaning up the fuel adjustments is more the point of writing this. I adjust these finer points to eliminate bogs, pops, and improve mileage. Throttle response got a lot sharper from minding a few of these smaller details in the mapping. Nobody really seems to be talking about this stuff, so I figure you're doing ok on your own or might not notice an issue.

I'll work my way down the table menus on the left of the software and just explain adjustments at each node.

Global Adjustments

The first place to start is load scaling. There were two twists here for my specific combo--440 injectors and a smaller displacement engine. These hard figures for me will be different than yours.

Gas - .04247
E85 - .05589

Note the difference of 25% between these load scales, roughly equivalent to the requirement of 20% more fueling with E85. That's the important part. I bumped up the difference due to running a richer target AFR on E85. A higher load scaling brought the STFT fuel trims within +/-5% on E85. My LTFTs really do never move.

Further regarding the global setup, turn off the fuel temperature sensor on E85. Ethanol runs colder, so this sensor will detect colder temps. Turning this off is one less thing to confuse the PCM. Turn off P0181, P0182, and P0183--all the fuel temp sensor codes. You don't have to, but I do so for the sake of cleanliness after turning off the sensor.

I also lowered the fan operating temperatures about 2C. Your choice of thermostat means more to these figures than the fuel. Ethanol runs colder, so I turn this down a little bit for shits and giggles.

Finer adjustments

I set injector end angle to 235deg across the board, except for 400-800rpm. You're setting when the injector turns off. In turn, the PCM adjusts when it comes on in reference to crankshaft angle. If I had usability of my engine's AVCS, I'd spend more time dialing in this table. Trying to add a gradient to this table makes the engine feel like it's playing scales on an instrument. Flattening this out with a static figure made my throttle feel more flat and torquey instead of quite so "v-tec" like.

Injector Offset is 1.74

Minimum pulsewidth is lowered to 1.22, since my injectors are bigger. Lowering this
cleans up idle AFR. Going too far will lean it out under power, though.

I'll skip base fueling adjustments here because this is so specific to my twin throttle manifold. A turbo would look just as "weird" to a beginner. My cranking fuel settings on twins is a little different, too.

Power fueling isa bit easier to explain

Initial fuel ratio is set between .853-.823 lambda through the rpm band.
Final fuel ratio is set between .848-.805 lambda through the rpm band.

These are about half a point leaner than a turbo would like, IMO. I'll swap in colder plugs before trying to lean it out any more.

Blend delay is 2.
Enable delay is 3.

I set these timers lower to speed up response to open loop fueling. It doesn't ask me a few times if I really mean it by working the throttle more than once.

Throttleenable for me is 14%-11% below 3600. Above that, is 0% so it's always in open loop when the cams are on power.

Load enable is set to 59kPa and 49kPa for me, so anything past cruise kPa triggers open loop. I only have closed loop fueling slightly enabled for highway cruising. Anything more triggers open loop fueling pretty quickly.

For timing, I aim for 32deg total. Any more than that becomes sensitive to knock with high temperatures even on E85. This is where I need to see if colder plugs help out at all. Playing a bit conservative here, but still toeing the line enough.

Idle air adjustments I've had to play with a lot because of my twin throttles. I've had to adjust nothing between gas and ethanol here.

Temperature sensors I didn't adjust.

Warmup fueling I shaved a bit off of, and here's why. After getting cranking fuel dialed in, it would then die out while warming up, with STFT's often being +20-30%. Pulling 20-30% out of these warmup table figures brought STFT back in line. Pulling back some fuel here kept the engine from drowning out in fuel while warming up.

Acceleraton enrichment was very crucial to me because of my intake manifold, less so because of the fuel. For you, adding a little bit of fuel on tip-in isn't a bad thing. Adjust the 2nd table, enrichment compensation, instead of the accel enrichment. You're adjusting a percentage this way, instead of a global adjustment. It's a finer adjustment on the 2nd table, and that's all it needs. When I was playing on the first table, it was adding too much fuel with incremental adjustments.

Decel enlean is like accel enrich. As much fuel as you're putting in, this takes it out. If you lift the throttle and get a fireball, then pulling fuel here eliminates the fireball. If you get an intake pop when you lift the throttle, then you need more fuel during decel. Pretty straight forward, here.

Deceleration fuel cut is the last table on the list. You're on your own with this one. I have a higher idle, smaller engine, and bigger injectors. My figures here would be nothing like the rest of you. The only thing I can say reliably is that you can adjust here if you're engine is dying out as it approaches idle.

The largest problem that I have tackled has been overly rich fueling at the wrong times. That's what all these little side tables have helped me fix. Make datalogs, then adjust. Rinse. Repeat. STFT's have been my guide. The stock o2 sensor is a little slow to respond, but you're at it's mercy to make everything work happily. Keeping that sensor happy keeps the PCM happy.

Cleaning up the fueling makes a night and day difference in how the throttle feels. Mileage improved, along with power. Adjustments are more intricate than just a global figure. If you like statistics, then you'll like noodling with these numbers.

Last edited by ImprezaRSC; 04-30-2017 at 11:21 AM..
ImprezaRSC is offline   Reply With Quote