I wonder if it is more of a function to trade some hang while helping to prevent stalling. I still think fuel cut is a better option also, but its just my guess.

 

DSM's cut fuel but don't stall. They will cut fuel when you lift off and then kick fuel back in at 1350 rpm or whatever you set it to.

 

Evos cut fuel also, but there is a delay in the fuel cut when you have been accellerating hard. This could be me quoting someone else, but I can guarantee that if you cut fuel the revs won't climb/hang.

In my first sentence above I was referring specifically to the ISCV opening fully and then (more specifically) not decaying to a fully closed state quickly when you let off.

 

I think we are on the same page but don't understand each other. The ISCV can do whatever it wants. It is simply parking at whatever angle it sees fit and that is fine by me. The injectors not shutting off is the issue however for throttle hang. I believe that might have been me that said that about cutting fuel killing any throttle hang. I said that a really long time ago in the throttle hang thread. I actually wouldn't doubt that it is a periphery bit as it is a "feature" that I think mitsu implemented to keep the cats from cooling off after a hard pull which will cause them to fail prematurely.

 

The ECU is probably maintaining open loop conditions until it passes below some minimum rpm. As long as its in open loop it will likely dump fuel in accordance with the fuel map. Carburated motors dump fuel too when letting off the throttle and there is no rev hang there. I suspect that if the ISCV can be made to clamp down, then the problem will be solved.

 

But they would rev-hang if there was an idle valve opening. But do what you want with the idle valve, but if you cut the fuel the revs will drop.

Getting a little off-topic, but I 100% agree with Dan, the issue is the fuel cut not kicking in. It does not happen to all models of Evo's, so wouldn't the best way of dealing with the issue be for those that have it to examine closely the correctly working roms? It might be worthwhile for someone to make a list of the problem roms too.

What I will add is that I can make my car throttle hang by screwing with the decel fuel cut delay maps. Normally it does not.

 

+2 please

 

I took special note of my RPM and AFR today while driving around. As usual, just letting off the gas results in an immediate fuel cut and max lean AFR.

Then I got on it ~40% through part of 2 & 3, then let off in gear. The AFR stayed stoich/rich until right at 3k RPM where it went lean again. I figured that may have been the RPM, but after a few subsequent tries in just 2nd and just 3rd gear the results were higher and lower depending where I let off. It didn't seem to be time specific to an exact/set amount, but I was not able to easily replicate the same load/RPM conditions to test. There is quite a bit of time as my car coasts pretty well while the fuel is still on.

 

Post 23 has a log i posted. You can see i did a pull and let off and the car goes to stoich until the ISCV decays to a specific point and the car goes lean again.

It has been terribly rainy here so the evo has been in the garage and i havent had a chance to play since i posted the log. I did make a change to one table that had no results. I will try again but it is really like a needle in a haystack.

 

A log of RPM, IPW, TPS, and ISCV should show up what is happening. Interesting to see if the decel cut wont kick in until the idle steps are below a certain amount but for certain roms there might be an upper rpm limit for decel cut!

I may have found an upper RPM limit, but I will move the discussion to the correct thread. Sorry for hijacking.

 

do you want to see the same thing i posted in 23? It is a 27min log with all those parameters. I cant attach the file but i can email it if you want it.

 

I have a question about the ISCV Demand RPM Adder [rpm > 4500, load > 170, speed > 12 mph] (sub_1EFC0) table. To me it looks like at a certain rpm and above a certain ISCV demand (the values in the table) it will add an rpm adder. Is there a table that defines how much of an adder? If I were to increase all of the values in the table >100% than the ecu would never add the adder?

To me this seems like a good table to start with to eliminate throttle hang. I returned the ISCV stepper look up table back to stock and have for the most part eliminated hang using the decel fuel cut tables, but I still have it pretty bad when I get up to higher rpm and higher loads.

 

It is actually starting to sound to me like a very mild antilag recipe. Just retard the timing alot in the areas of the map where the hanging happens. You have the air supply already....

You wont see boost, but it may help gearshift response a little.

 

lol youve been reading my mind

 

Something else I noticed with the idle control. My car raises the target idle with the thermo fan on. So there might be a few more things to go looking for.