For months I've been trying to solve an issue with my Evo running rich at idle. My tuner and I were able to get the car finally to the 13AFR range, but the latencys are unusualy low and starting to affect stability of the idle if we go much lower.

Evo IX
Stock block
FP Green HTZ 84mm MHI
FP race manifold
GSC S2 cams
FIC 1650cc HighZ injectors (resister bypass)
Double pumper with pressure switch for second pump (two walblo 255s)
boomba fuel rail with stock FPR and lines
Buschur TBE with high flow cat
Buschur FMIC/LICP/UICP
Spoolinup COP
Stock ECU with speed density


Any ideas of how to solve this? Things to check?

Things I've tried and tested:
I've done multiple boost leak checks
Bypassed the FPR solenoid
Bypassed the EGR stuff
Changed the coils
Changed widebands

I'm going to try some more ideas of mine, but I just wanted to check the fourm to see if anyone has run into this issue.

 

You haven't measured fuel pressure.

At idle it'll be 6 PSI too high as they all are with a 255 pump.

More pressure means you need shorter PW to get the right AFR.
More pressure means you need extra dead time programming in.

Then it's all wrong as the load increases.

 

Does the ROM your tuner is using have the minimum IPW table patch? Has your tuner adjusted it?


Don't listen to Fred. Your car will idle at stoich. I have a feeling something in the tune has been overlooked.

 

I have a fuel pressure gauge on order and will check the rail pressure.

I will check about the IPW table. I assume it's already been applied. To check the ROM do I need to add the table to ECU flash or is it already in the default XML definition?

 

The ROM doesn't have the minimum IPW table patch that I can tell.

After doing some research it looks like the Injector flow rate linearization tables is the most up to date method. I will talk with my tuner about it as that patch isn't applied either.

https://www.evolutionm.net/forums/ec...0-fic1650.html

 

Yes that table supersedes the minimum IPW table.

 

Resistor bypass causes issues if you don't drill out the siphon tube. Have you done this? I would just put the resistor back in.

 

I'm assuming it's the resistor for the fuel pump? Or are you referring to the resistors for the injectors that you bypassed?

 

The injector resister bypass.

http://www.spoolinup.com/Injector-Re...pass_p_73.html

All the rest of my fuel system is stock other then the dual pumper and fuel rail. And for the dual pumper my stock siphon was swapped into the new core.

 

The tune was used on other similar setup Evos and they didn't run rich. So I'm trying to figure out if there is a reason behind this or if my Evo is just different for some reason.

 

Yea check your fuel pressure. Drilling the siphon and running the linearization table should help. Make sure your return line isn't blocked/kinked.

 

I should have the fuel pressure gauge installed in a couple of days. What fuel pressure should I be reading at idle (1000rpm) 14-15 in/hg vacuum?

The linearization table requires a full retune correct? I'm guessing there would need to be changes to the injector latencys.

 

You should see 35-37 psi at idle with the vacuum line connected depending on how big your cams are. Once you start getting over 39-40 at idle it will be harder to tune. i drill the siphon on double Pumpers no matter what the fuel pressure at idle is because it helps with the rich afr when the second pump kicks on.

No it will not require a full retune, just idle and part throttle areas of the map. If you drill the siphon then you may need to touch up afr's up top also.

One thing that can help also is to turn down the timing in the rich idle areas. This will load the motor down some at idle. It in turn will require more fuel to idle. Bump it down around 5-7 degrees.

This is a lot of screwing around so treat your tuner well and he will get it ciphered out I'm sure.

Mr Freds post has settings that are very close, so start with his latencys and linearization settings.

 

The factory spec is 33 PSI at idle, that's at sea level with 18 " ish of manifold vac.


That's what you get before it's broken.

After you fit a 255 pump , you'll see 38 or 39 PSI.

 

Dude how many evo's have you tuned?
Shut up for crying out loud

Your not gonna break anything at idle!