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How to Eliminate "Rev-Hang" on the 05+ EVO 8/9s

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Old Jun 19, 2013, 10:58 AM
  #16  
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Originally Posted by el.guerrero View Post
i do this on my 88580714 rom. hang still there.. i notice my afr stay at 13/13.5 during throttle release and brake engine moment..

Anyone?
Email me your ROM and Ill check it out. Email in sig.
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Old Jun 19, 2013, 11:19 PM
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thanks a lot sir.

Sent!
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Old Jun 20, 2013, 04:16 AM
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Boosted , I would appreciate if you could share how you fixed that, I will be looking at that rev hang soon...

Thanks
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Old Jun 20, 2013, 09:46 AM
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This may be a too obvious comment, but just want to make sure folks remember before they get too complex into tables.....Always check for boost leaks periodically. I forgot who got all on me a few years ago about it, maybe it was Boosted, not sure, but boost leaks exist more than you think. I did have a few, and over time you will get them again. Its sometimes amazing how many little ones you get.

The point is when you do have little ones, you will have momentary lean conditions when you off throttle rapidly, because the vacuum will suck in lots of air not calculated by the maf. Unless you are really solid on your logs to see it happening via AFR you may just feel it as rev hang. The lean condition will give you that acceleration because that brief moment you have more vacuum than normal. This makes little boost leaks have this behavior. I had this scenario, and when I resolved some of those newer leaks I had (pinhole in IC pipe), I resolved the really nasty ref hang.

Another clue is if the rev hang seems to get slightly worse slowly over time.

Checking for books leaks should be a regular maintenance tasks. With a 30 dollar tester its super easy too. Its worth checking or confirming so you aren't chasing a fundamental mechanical issue with modifications to the tables.
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Old Jun 20, 2013, 10:48 AM
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is there a reason the hang exists in the first place? i.e., designed that way on purpose?
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Old Jun 20, 2013, 10:54 AM
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Originally Posted by kyoo View Post
is there a reason the hang exists in the first place? i.e., designed that way on purpose?
To a certain degree the information I have read does indicate its intentionally, but only slightly. Once you start changing airflow, modifications, then you also change its behavior. When you have it real bad, you will know, as its clearly not safe for the engine. I had it bad enough at one point that the car could stay at 7k in neutral on track. I still have it a little under certain conditions, but it was due to boost leaks sucking in air under vacuum. Leaks were small enough that regular vacuum didn't cause much of a logable issue.

Mentioned earlier in this thread and in several others is the benefit to keeping revs slightly up during shifts, but stock its subtle.
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Old Jun 20, 2013, 11:24 AM
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Originally Posted by kyoo View Post
is there a reason the hang exists in the first place? i.e., designed that way on purpose?
Its there for emissions purposes, from what I've read.
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Old Jun 20, 2013, 12:10 PM
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Originally Posted by fireroasted View Post
To a certain degree the information I have read does indicate its intentionally, but only slightly. Once you start changing airflow, modifications, then you also change its behavior. When you have it real bad, you will know, as its clearly not safe for the engine. I had it bad enough at one point that the car could stay at 7k in neutral on track. I still have it a little under certain conditions, but it was due to boost leaks sucking in air under vacuum. Leaks were small enough that regular vacuum didn't cause much of a logable issue.

Mentioned earlier in this thread and in several others is the benefit to keeping revs slightly up during shifts, but stock its subtle.
Originally Posted by Boosted Tuning View Post
Its there for emissions purposes, from what I've read.
interesting, good to know. maybe keeps the spool going up top? it's pretty damn annoying for regular driving
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Old Jun 20, 2013, 12:15 PM
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Old Jun 20, 2013, 03:06 PM
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Old Jul 17, 2013, 01:48 PM
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Thanks for this. Rev hang is the very annoying. Really hoping this fixes it on my car. Two questions.

Question 1 - Updated the definitions (ROM 88590015). Opened ECUFlash and when I click on any of the new tables, I can only see the left column. Any idea how to see the right column so I can change the values? Sorry if noob question. Looks like this when I click on a table. Can't figure out how to expand the window.



Question 2 - For Step 1, are we supposed to change all 4 tables as you pictured, or just 2 tables? The wording is kinda confusing.

Originally Posted by Boosted Tuning View Post
STEP 1 - Change the "Decel Fuel Cut Delay" tables (aka "ISCV Demand TPS Adder, AC off (FFFF6E84) (mattjin fuel cut delay)" & "ISCV Demand TPS Adder, AC on (FFFF6E84) (mattjin fuel cut delay)"). Use the values show below:

NOTE: When using the "ISCV Demand TPS Adder, AC off (FFFF6E84) (mattjin fuel cut delay)" & "ISCV Demand TPS Adder, AC on (FFFF6E84) (mattjin fuel cut delay)" tables, the values will be totally different:
So are we supposed to change Decel Fuel Cut Delay #1 & Decel Fuel Cut Delay #2, AND ISCV Demand TPS Adder, AC off (FFFF6E84) (mattjin fuel cut delay) & ISCV Demand TPS Adder, AC on (FFFF6E84) (mattjin fuel cut delay)? Or just change one of the pairs?
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Old Jul 17, 2013, 02:02 PM
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Blitz, in regard to your question #1: Looks like there's a problem with the table definition. Double-check that there aren't any mistakes in the xml file.
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Old Jul 17, 2013, 03:51 PM
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Add this to the Idle Control section of your xml.
The tables simulate the old throttle dash-pot device which slows throttle closing.
Its there to make decel smoother but Mitsu make it a bit to soft and you get rev hang.


<scaling name="ISCVSteps8" units="Steps" toexpr="x" frexpr="x" format="%.0f" min="0" max="255" inc="1" storagetype="uint8" endian="big"/>
<scaling name="ISCVSteps16" units="Steps" toexpr="x" frexpr="x" format="%.0f" min="0" max="255" inc="1" storagetype="uint16" endian="big"/>
<scaling name="Throttle%16" units="TPS %" toexpr="x*100/255" frexpr="x*255/100" format="%.1f" min="0" max="100" inc="0.392" storagetype="uint16" endian="big"/>


<table name="ISCV Dashpot Throttle Adder, AC OFF" category="Idle Control" address="3d6e" type="2D" scaling="ISCVSteps8">
<table name="THROTTLE" address="6f9a" type="Y Axis" elements="7" scaling="Throttle%16"/>
</table>

<table name="ISCV Dashpot Throttle Adder, AC ON" category="Idle Control" address="3d82" type="2D" scaling="ISCVSteps8">
<table name="THROTTLE" address="6f9a" type="Y Axis" elements="7" scaling="Throttle%16"/>
</table>
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Old Jul 17, 2013, 04:11 PM
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Originally Posted by Raptord View Post
Blitz, in regard to your question #1: Looks like there's a problem with the table definition. Double-check that there aren't any mistakes in the xml file.
Thanks but I copied/pasted them exactly from the Boosted's post. Didn't miss any signs or anything. All of my other tables display just fine.
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Old Jul 17, 2013, 06:18 PM
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I'm having this same problem but my car is stock with stock tune. Any ideas?
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