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Discussion Starter #1 (Edited)
After owning my 2018 hatch for more than half a year, I decided that enough was enough and decided to figure out how to get rid of the rev hang. As we all know, the rev hang for the 5 speed manual transmission is extremely annoying, especially at higher RPMs. Thankfully, it can be fixed by flashing the ECU. Unfortunately, it does require spending some $$$ for some hardware and software.

Before we continue, please do note that flashing your ECU is a potentially dangerous activity. If you change parameters without knowing what they do, you could render your car immobile. I am only an enthusiast and do not tune any cars professionally, so these findings are from the best of my knowledge, and may not be completely accurate. If you are not willing to take the risk, it is best to consult a professional tuner instead.

Please proceed at your own risk!

The following tools/software are required:
- tactrix 2.0
- subaruEdit Personal

I will not be guiding you on setting that up as there is already plenty of information online about it.

Once you received the stock ROM dump from epifan, we can begin modding.

1) Open up your ROM in subaruEdit
2) Find the tables for (Fueling \ Overrun)

1-FuelingOverrunTable.PNG

3) Open up the table for "Desired Overrun Mass Air Flow A"

You should see something like this:

2-DesiredOverrunMAFA.PNG

As we can see, the overrun table adds a lot of air (and correspondingly, lots of fuel) at high RPMs. This contributes to the rev hang we experience when we clutch in, or decelerate.

The values of interest are located between the coolant temps 80 - 110C. We only need to modify these values because they are in the range of normal driving coolant temperatures.

For my current setup, I made the following adjustments. Feel free to adjust more or less to your liking.

Decreasing these values more will cause the RPMs to drop faster, and may also make stop and go driving more difficult.

For RPM >= 4400 and coolant temp >= 80, use 50% of value (reduce 50%)

3-InterpolateHighRPM.PNG

For 2800 >= RPM = 80, use 70% of value (reduce 30%)

4-InterpolateMidRPM.PNG

For 1600 >= RPM = 80, use 80% of value (reduce 20%)

5-InterpolateLowRPM.PNG

In the end, we should get a table that looks something like this:

6-Resut.PNG

You may have to manually adjust some values so that the map is smooth, and such that the values increase monotonically as the RPMs increase.

4) Perform the same steps on tables "Desired Overrun Mass Air Flow B" and "Desired Overrun Mass Air Flow C"

5) Upload ROM to ECU with flash utility

With the rev hang delete, I noticed the following changes:
- The car is less jerky between shifts. I no longer burn the clutch shifting between 1->2 trying to get a smooth transition.
- Rev hang completely eliminated at high RPM (> 4000).
- Throttle seems more responsive

Credits:
RalliSport Automotive for dropping hints on what to modify for rev hang. The original thread discussing FB20D tuning is here: subaruxvforum [dot] com/forum/performance-modifications/171066-2018-fb20d-tuning.html

I hope you will find this guide useful.
 

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I have the tactrix 2.0 adapter and the subaruEdit Personal. So far, I've just had Rallisport delete the rev hang (which IS awesome with it gone) from my tune and adjust a couple of other settings. But that was with the original tune. I have the new ECU tune from the recall saved as a loadable ROM, but haven't been able to get in contact with Rallisport for a while to get the rev hang from the new tune deleted. This seems like it might be worth experimenting with. Thanks for posting.
 

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~$300 to get rid of rev hang seems worth it but I'm a little nervous about messing around with things like this.

NoSlushbox4Me, did your tune from Rallisport look similar to what grfaust has concerning the 'Desired Overrun Mass Air Flow' charts? I'm just looking for some sort of verification that the info is legit. A google search on the topic yielded nothing else.
 

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It looks like I have the lite version of subaruEdit, not the personal version. I can't see or modify the maps, yet. Looking into upgrading to the personal version.
 

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Ok, I have the necessary version of subaruEdit now. The maps in the previously tuned ROMs I have are hidden (which I understand) so I can't see what was done to them. I did these overrun fueling changes to the new recall tune and it does reduce the rev hang, but it's not as good as the rev hang delete in the tunes done by Rallisport. That eliminated the rev hang. To be closer, I think the changes should be applied across the entire RPM range and be more significant reductions. But, I really really really hate rev hang.
 

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If a little rev hang deletion is good, a lot of rev hang deletion must be better. For all 3 maps (A, B, and C) I went ahead and set 0% overrun fuelling for 1000 RPM and higher for the 80 deg F and warmer tables. For the same RPM range in the 70 deg F table, I set the overrun fuelling to 50%. After a quick test drive, it's very good now. The revs drop how they should, considering there's no lightweight flywheel or anything like that. From a quick internet search, I didn't see any reason to keep any of the overrun fuelling. Eventually I may zero it all out if I find a rev hang quirk that bothers me. If the temperature of the air coming in is the 70 deg F, 80 deg F, etc., then I might at least zero out the overrun fuelling at lower temperatures than 80 deg F. However on a 43 deg F day here (today) it seemed really good with these current settings.

22804


This modification is being done to my own personal car and I accept responsability (and enjoyment) only for how my personal car changes because of this. If you are uncomfortable making this sort of modification to your personal car, then consider that before proceeding.
 

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Lots of good information there. Definitely more motivated to check this out in the spring :)

Decreasing these values more will cause the RPMs to drop faster, and may also make stop and go driving more difficult.
Any effect on stop and go driving with your new settings? 1/3 of my commute is stop and go, so I'd be interested in this.
 

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The only affect I've noticed is that without the forced overrev, in low gears if you dump the clutch too fast you get the slight jerkiness of a manual transmission car that has had the clutch dumped too fast at too low of a throttle setting. It's more an effect of poor shifting habits than it is engine tuning. Any manual trans car without rev hang would do the same thing if the clutch is engaged too quickly without enough throttle. I'm ok with the car giving me direct feedback on how well I'm shifting.
 

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If a little rev hang deletion is good, a lot of rev hang deletion must be better. For all 3 maps (A, B, and C) I went ahead and set 0% overrun fuelling for 1000 RPM and higher for the 80 deg F and warmer tables. For the same RPM range in the 70 deg F table, I set the overrun fuelling to 50%. After a quick test drive, it's very good now. The revs drop how they should, considering there's no lightweight flywheel or anything like that. From a quick internet search, I didn't see any reason to keep any of the overrun fuelling. Eventually I may zero it all out if I find a rev hang quirk that bothers me. If the temperature of the air coming in is the 70 deg F, 80 deg F, etc., then I might at least zero out the overrun fuelling at lower temperatures than 80 deg F. However on a 43 deg F day here (today) it seemed really good with these current settings.

View attachment 22804

This modification is being done to my own personal car and I accept responsability (and enjoyment) only for how my personal car changes because of this. If you are uncomfortable making this sort of modification to your personal car, then consider that before proceeding.
I'm going to do exactly as you've done. Before I proceed I would like a little clarification. Did you actually go by degrees Fahrenheit or degrees Celsius? I see you've written the temps in °F but I see the screenshot is °C. I don't want to mess anything up if I don't have to.
 

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:D
I made the incorrect assumption that the temperatures were degrees F because this adjustment had to do with air flow and those temps made some sense for air temp in degrees F too. But the label on the left does indeed say coolant temp in degrees C. That's what I used.
 

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:D
I made the incorrect assumption that the temperatures were degrees F because this adjustment had to do with air flow and those temps made some sense for air temp in degrees F too. But the label on the left does indeed say coolant temp in degrees C. That's what I used.
Didn't mean to call you out like that, thank you I appreciate it. 😅
 

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No problem. Good catch. I don't mind having details I missed pointed out. I'm learning stuff here too.
 
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