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

I get a lot of emails about eliminating the rev hang in the 05+ EVOs. So heres how to fix it.

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 different, use the bottom values.

https://www.evolutionm.net/forums/at...1&d=1367519816


STEP 2 - Zero out all the "ISCV Demand RPM adder" tables.

https://www.evolutionm.net/forums/at...1&d=1367519660

STEP 3 - Enjoy your car without rev hang {thumbup}

Note: Some of these tables may not be in your current .xml file for your ROM and you may have to add them manually.

DEFINITIONS:

88590015

<table name="Decel Fuel Cut Delay #1" category="Global Fuel Settings" address="3d6e" type="2D" level="2" scaling="uint8">
<table name="Load" address="6fc6" type="X Axis" elements="7" scaling="Load"/>
</table>

<table name="Decel Fuel Cut Delay #2" category="Global Fuel Settings" address="3d82" type="2D" level="2" scaling="uint8">
<table name="Load" address="6fc6" type="X Axis" elements="7" scaling="Load"/>
</table>

<table name="ISCV Demand TPS Adder, AC off (FFFF6E84) (mattjin fuel cut delay)" category="ISCV Control" address="3d6e" type="2D" level="1" scaling="ISCV_AX2_8">
<table name="TPS" address="6f9a" type="Y Axis" elements="7" scaling="ThrottlePercentage"/>
</table>

<table name="ISCV Demand TPS Adder, AC on (FFFF6E84) (mattjin fuel cut delay)" category="ISCV Control" address="3d82" type="2D" level="1" scaling="ISCV_AX2_8">
<table name="TPS" address="6f9a" type="Y Axis" elements="7" scaling="ThrottlePercentage"/>
</table>

<table name="ISCV Demand RPM Adder* (sub_1EFC0)" category="ISCV Control" address="41d8" type="2D" level="2" scaling="ISCV_AX2_8">
<table name="RPM" address="6b7a" type="Y Axis" elements="10" scaling="RPM"/>
</table>

<table name="ISCV Demand RPM Adder [rpm 4500, load 170, speed 12 mph] (sub_1EFC0)" category="ISCV Control" address="65de" type="2D" level="2" scaling="ISCV_AX2_8">
<table name="RPM" address="7fb0" type="Y Axis" elements="10" scaling="RPM"/>
</table>

<table name="ISCV Demand RPM Adder (Moderated by Baro, IATS) (FFFF6EA8) (sub_204B6) [sub_1EFC0]" category="ISCV Control" address="672a" type="2D" level="2" scaling="ISCV_AX2_8">
<table name="RPM" address="802a" type="Y Axis" elements="10" scaling="RPM"/>
</table>

96940011

<table name="Decel Fuel Cut Delay #1" category="Fuel" address="3972" type="2D" level="2" scaling="uint8">
<table name="Load" address="5d52" type="X Axis" elements="7" scaling="Load"/>
</table>

<table name="Decel Fuel Cut Delay #3" category="Fuel" address="3986" type="2D" level="2" scaling="uint8">
<table name="Load" address="5d52" type="X Axis" elements="7" scaling="Load"/>
</table>

<table name="ISCV Demand TPS Adder, AC off (FFFF6E84) (mattjin fuel cut delay)" category="ISCV Control" address="3972" type="2D" level="1" scaling="ISCV_AX2_8">
<table name="TPS" address="5d52" type="Y Axis" elements="7" scaling="ThrottlePercentage"/>
</table>

<table name="ISCV Demand TPS Adder, AC on (FFFF6E84) (mattjin fuel cut delay)" category="ISCV Control" address="3986" type="2D" level="1" scaling="ISCV_AX2_8">
<table name="TPS" address="5d52" type="Y Axis" elements="7" scaling="ThrottlePercentage"/>
</table>

<table name="ISCV Demand RPM Adder* (sub_1EFC0)" category="ISCV Control" type="2D" address="3de4" level="2" scaling="ISCV_AX2_8">
<table name="RPM" type="Y Axis" address="594e" elements="10" scaling="RPM"/>
</table>

<table name="ISCV Demand RPM Adder [rpm 4500, load 170, speed 12 mph] (sub_1EFC0)" category="ISCV Control" type="2D" address="56e0" level="2" scaling="ISCV_AX2_8">
<table name="RPM" type="Y Axis" address="6e92" elements="10" scaling="RPM"/>
</table>

<table name="ISCV Demand RPM Adder (Moderated by Baro, IATS) (FFFF6EA8) (sub_204B6) [sub_1EFC0]" category="ISCV Control" type="2D" address="57f0" level="2" scaling="ISCV_AX2_8">
<table name="RPM" type="Y Axis" address="6ef0" elements="10" scaling="RPM"/>
</table>

{thumbup}

for the decel fuel cut delay, which values are we supposed to be switching to? the top or the bottom?

Bottom.

That's what I figured, do I need to modify decel fuel cut 3 &4?

Yeah, just do them the same way. The ones that a lil lower stock, will be the lil lower modified one.

just want to point out that :

1) fuel cut delay do not exist, those were wrong definitions, the label is wrong, the load is wrong the units are wrong, why keep using something that has nothing labeled right and with values that represent nothing ?
2) the ISCV demand tables shown in those pictures are also wrong, it should be TPS % on the left not RPM and mrfred who found the real table only attributed 7 elements to it so I'm wondering what are really doing the 3 more shown in the above pictures ?!

Decel fuel cut has originally been guessed by mattjin but has since then been corrected by mrfred
see there in the 1st post : https://www.evolutionm.net/forums/ec...sassembly.html
The address used should be the same as decel fuel cut (double check before changin anything), update the table definition from mrfred thread and you're good.
http://img12.imageshack.us/img12/9402/iscvdemand.jpg

for your information :

- I also zeroed them because I appreciate the instant engine-braking this change provides
- know that doing that can hide the real problem, if everything was ok you shouldn't have more than a "livable" 1sec of hang
- stock has a small amount of it, it's meant to make gear changes smoother, zeroing those tables can make the car buck every time you lift-off (depends in great part on your recirc/bov)
- ISCV control is very complicated and takes lots of things into account : a/c , power steering, braking, acceleration, temperature etc... a good 100 parameters are taken into account so your throttle hang can come from a lots of things (turn out mine was coming from the steering pump, it blew up one day and after the change my hang was gone and I could drive normally without zeroing those tables)
- log your ISC steps at idle (warm engine) you should have something between 20-40 steps if you have 50+ you have a real problem somewhere

I battled with throttle hang problems for 2 years on my car, I hope you'll fix yours faster than that, good luck !

I'd be careful with zeroing out everything in the low rpm range. This can lead to the car dying while coming off throttle after cruising.

Dan

I'm subbing in!!!

All that doesnt matter. Yes the decel fuel tables were defined "wrong" but that doesnt matter. All that matters is that doing this works.

1 - Wrong, doing this will not "hide" any problems. And if you let off throttle at redline, the rev hang can last for many seconds, not just 1 second
2 - Incorrect. Zeroing the tables will NOT make the car buck on lift off
3 - Wrong. This is the cause of rev hang and this is the correct fix.

Umm those stock are already zero'd out in the low range. {thumbup}

Depends on the rom... I have found that Tephra V7 cars (as they are all zero'd) with stalling from high rpm issues can be fixed with adding some percentage there.

Dan

No, it doesnt depend on the ROM. They all have the first couple boxes zero'd when stock. Also its not zero'd out on V7 ROMs either (the stock tables I posted are from an unmodifed V7 ROM).

Its true though, that adding some demand there can help get rid of stalling when dropping from high RPM.

I'm loving the cat fight... I wish i had enough knowledge to slap someone in the face with some tuning bs i pulled out of my ass to try and discredit a legitimate tuner to make me look better... I would sooooo be on this... But i dont. So i am waiting for my car to finish to impliment this and see how she likes it...

I have a ton of respect for Boosted and I am not trying to make myself look better. I am speaking from experiences I've had and trying to help the community as a whole. I don't tune for a living. I will investigate and report back. From my experience taking cars from a stock rom to V7 has caused issues with stalling coming down from high rpm. I have found differences in these tables and revised them and solved the stalling issues, that is all.

Dan

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?