Subaru Impreza GC8 & RS Forum & Community: - View Single Post - DIY: ProjectLambda Stock ECU Reflash Tuning (Master Reference Thread)
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Old 08-23-2016, 09:52 AM  
2.0L Turbo
Car: 2000 2.5RS BRP
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Acceleration enrichment strategery .

Fine tuning acceleration enrichment will have you jumping through a few different tables. I've been using kPa enabled enrichment on the AH-966X template.

3 tables to be concerned with

Fuel-Acceleration Enrich

This is for finer changes in throttle percentage. (2%-19%.) The columns are scalable, but a little pointless. I tried getting down to 1.5% to really perfect cruising on twin throttles, but it just didn't help me. Adjusting the mapping here is more important than rescaling the column values for throttle percentage. Larger injectors will need this table re-mapped to avoid over-richening on tip-in. You only actually need their larger capacity under boost or at high rpm.

FYI--those two pointless columns on the right? Don't mess with those.

Fuel Acceleration Enrich RPM Compensation

This table adjusts your pulsewidth considering the RPM that you're at. If you're at 4,000rpm and need a bigger slug of fuel than at 3,000rpm, that's basically what this table is for. I tended to tailor this one more around my bigger stock heads and cams without active AVCS, giving it a bit more fuel up top and not adding as much down low. SOHC engines might not want as much up top, instead wanting more fuel in the middle rpm, say from 2500-5500rpm.

Volumetric Efficiency - Throttle Compensation

This is where things get a little trickier. You're swinging into the outfield here. I set this table up to "pick up" where the Fuel-Acceleration Enrich table leaves off. That table stops modifying fueling at 19% throttle. This table, I've back-filled to 27% throttle. It's basically for throttle changes percentages after tip-in.

There's further nuance at play in this table. You're adjusting fueling, but irrespective of RPM. It's labelled as being able to dial in fueling according to pressure waves. Most of us at home, that's a little over our heads. It might be easier to explain it as tailoring fueling to the airflow characteristics of your engine combination. Consider my earlier comparison of my 2.0 with non-active AVCS vs. a stock 2.5L SOHC. My 2.0 loves the top end, wanting more fuel up there and less in the middle. The 2.5L SOHC loves the midrange but runs out of breath up top. Adjust your numbers accordingly. The 2.5L mapping is way off on my combination, and my mapping would be way off for a 2.5L SOHC.

Change the cams in the SOHC to Delta 2000s or something comparable, and you'll get more of that same midrange punch character. Keep that same curve in the map, but increase all the figures a tad.

Part of where the map blending gets tricky is just where my experience stops. We're all going to have different experiences with dialing things in. My twins can reach 100kPa at 5-7% throttle, basically just twitching the throttles at idle. If I give too much throttle at low rpm, it bogs. shit. I've doubled the throttle area on a detuned stock motor. I'm not adding as much fuel as you might think, more because of the non-active AVCS. I've had to tune more around that than I have dialing in for the mods. Just dumping in fuel is easy, but you can really get it right with polishing the details in these tables.

How do you know you're getting somewhere using these tables correctly? I'll just say from my own experience what I was seeing. I was pegging the AFR readings to full rich just by cracking or opening the throttle. I dialed back added fuel in these tables until throttle changes showed AFRs closer to open loop targets. If you don't add enough fuel during throttle changes, then you'll see a lean AFR. If you're adding too much, you'll see a rich AFR. The trick is WHEN you're seeing it. I was seeing it way too rich at 1-5% changes in throttle and then level out a bit up top.

(Mike, correct me if I'm wrong here.) The ECU won't adjust for the AFR shown in open loop, but it will still show you the number present at the sensor in the logs. That's how you know where you're headed. An external wideband will give you a better idea of where your AFRs are at and when, but the ECU is still only going to do what you tell it and respond to what it can see.

Confused? Good. Let that marinate in your noodle for a while. You'll get the hang of it. Until then---

Last edited by ImprezaRSC; 10-22-2017 at 07:03 AM..
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