Raptord

iTrader: (10)

The car should idle at your desired rpm, but if the BISS isn't set the same as your desired rpm, that's when problems arise; the IAC has to fight the BISS to get to the desired idle, it starts over-compensating, and you get what we have now; unstable idle. (My theory at least)

I'm still playing around with mine as well, trying to find the sweet spot. As I get new info I'll post back in this thread.

wizzo 8

iTrader: (35)

Well I spent almost 3 hrs playing around with BISS settings, idle stepper settings, 500 rpm revovery, Idle stability timing control and sensitivity, idle rpm in drive, iscv demand rpm adder 500-5000rpm with no luck. I didnt touch the idle stepper look up table. I dont remember having this problem when it was warm out. I may just stop worrying about it for now since its starting to warm up now. I also checked for vacuum leaks.

wizzo 8

iTrader: (35)

I tried cleaning my maf and air filter to see if it would help but it didnt. Anyone else have any luck with this?

RJSP

I´m sure you know this, but have you checked the TPS? I recently installed a new TB and idle was crap with a lot of stalling until I made sure TPS was adjusted properly, ie. reading 100% at wot (car off just ignition on) and reading around 14% at idle.

Also, since I run without and ISCV I have to keep revs at around 800 - 900 rpm at idle. In my case I have seen that because of the freer flowing intake maybe the is less vacuum effect just at idle, and in the MAF calibration for idle loads (19 and 25 Hz) I had to take out around 1 to 1.5% of flow (fuel) to improve idle stability and help avoid stalling, everywhere else in the MAF scale I´ve had to add flow to compensate for the intake mods. In essence my stalling seems to have occured when ever I had too much fuel and less air at the time the revs come down so the car would stall.

All the above of couse was done after rulling out vacuum leaks or pre trubo exhaust leaks.

Good luck,

Ricardo

wizzo 8

iTrader: (35)

Thanks for the info. I was also thinking it was a maf setting. Ill try it and see what happens

wizzo 8

iTrader: (35)

I lower the first 2 blocks by 1.5% but didn't change anything. Oh well worth a try

RJSP

Another thing that would make a difference in my "clutch in stall" was the adjustment of the bov/dv. I run a GFB response DV and if the preload is too much, stalling tendency gets worse, also running it in 50/50 recirculating/VTA helped a lot to avoid stalling and didn´t upset the MAF.

Jack_of_Trades

iTrader: (17)

I battled this for ages once on a car and it ended up being a bad MAF. Plugging in a known good MAF solved the problem. It was possible that messing with the MAF scaling would have made the issue tolerable though. I would definitely look into MAF tweaks to see if you can get it under control.

wizzo 8

iTrader: (35)

Yes I belive it is something to do with a maf setting. Im building the motor at the end of april so Ill deal with it after the build I guess. Im will play around with some maf settings to see what happens in the mean time. I will also play around with the preload and port settings of my Synapse bov

1091x

Good info I'll give it a try

Raceghost

iTrader: (4)

This is the table deffinition in the 94170715 Rom file, it is incorrect.

<table name="ISCV Demand RPM Adder* (sub_1B1DA)" category="ISCV Control" address="47d6" type="2D" level="2" scaling="ISCV_AX2_8">
<table name="RPM" address="635a" type="Y Axis" elements="10" scaling="RPM"/>
</table>




Can someone give me the correct deffinitions for this table please?

merlin.oz

Raceghost,

47C6 is the ISCV Decel (Fuel-Cut) Demand Step Position Adder

and

47D6 is the ISCV Decel (Fuel-Cut) Demand Step Position Limit

both have 635A as the RPM axis.

The table units are steps (uint8).

Raceghost

iTrader: (4)

Bump for Merlin. Never saw this post last year. Finally to the point of tuning again. Can you give me the Table definitions for the post above. I only have ICSV Demand RPM adder table in ISCV location. I don't have either if the ICSV Tables you list. I have Decel Fuel Cut tables in Fuel, but they are not the same definition addresses you speak of. Thanks.

turbotiger

Gotta give props to the OP. the 'ISCV Demand RPM Adder*' table fixed my idle issue with Kelford 272 cams I've been having ever since installation. I have the first 6 entries set to 11.8 and that made my idle a ton more stable. Up a hilll, a/c on, doesn't matter, it doesn't tend to die anymore.

mrfred

iTrader: (50)

I've been assessing this issue for my Evo recently. My car doesn't stall, but in warmer weather, it dips down in the mid-600 rpm range when coming to a stop after a long decel. It does *not* look like its primarily an ISCV issue for my setup. The primary issue I'm seeing is lean fuelling when attempting to establish idle. The injectors shut off during decel, and then kick back on when nearing idle conditions, but since the intake manifold runners get cleared of all wall wetting during decel, fuel needs to build back up again before target AFRs will reestablish, at least that's my idea for the moment.

There is an "idle approach" enrichment, but it provides a very minor amount of enrichment, ~3-5% for the stock settings. Instead, it looks to me that Mitsubishi attempts to reestablish AFRs by kicking on the injectors earlier than needed for idle. For completely stock mapping, the injectors kick back on 200 rpm before reaching target idle. Like many people with big cams, I have raised my target idle to allow for smoother idle. However, changing the target idle does not simultaneously raise the rpm where the injectors kick back on. That needs to be handled by the decel fuel cut tables. The "start rpm" for the idle approach enrichment should also be raised by the same amount.

So far, I have only raised the decel fuel cut end engine speed by 100 rpm to match my 100 rpm idle speed increase (900 rpm target idle), and this has helped. Its not totally fixed though, and my next step is to raise the idle approach enrichment start engine speed by 100 rpm as well. If that doesn't fix it, then I'll experiment further, probably with the amount of idle approach enrichement, and then maybe with the ISCV demand as well.

For people with lightweight flywheels and/or high compression ratio, raising the ISCV Demand RPM adder values that the OP mentioned should help by allowing the engine to slow more gradually when pushing in the clutch. My clutch/flywheel combo is only 1-2 lbs lighter than the stock setup, so my setup shouldn't need much change. I wouldn't use exactly the values shown in the first post of this thread though. I would probably do something like:

500 0
1200 0 (changed from 1000 rpm to 1200 rpm)
1500 19.2 (stock = 0)
2000 19.2 (stock = 0)
2500 19.2 (stock val)
3000 28.6 (stock val)
3500 34.1 (stock val)
4000 42.4 (stock val)
4500 45.9 (stock val)
5000 45.9 (stock val)

An important difference is that I'm not including any adder in the idle range where the ISCV demand trims are active. Intead, I've set the 1500 rpm and 2000 rpm values to value to match the 2500 rpm value, and then changed 1000 rpm to 1200 rpm so that there is no adder in the idle range. I think this strategy should be helpful in combating fast rpm drop when pushing in the clutch.