hi guys

i have a built B18 with a garrett to4e (afi turbo kit). it is tuned to 20psi on s300.

right the problem is the air/fuel ratio@WOT it is around 10.2/10.6
and cruising between 60/70mph the afr can be 12.8/13.8 but sometimes it goes to between 14.2/15.2!!!

is this the tune?
or is there something else?

any ideas or thoughts would really help!!

 

Looks like more time needs to be spent on the part-throttle cruising region of the fuel map.

Anything below 14.5 at cruising is (IMHO) too rich.

Your S300 has onboard datalogging. Connect to SManager, make sure your target lambda map is setup correctly and drive around for a few hours to populate all the cells below ~750mbar (typically column 6). SManager has the option to recommend fuel % changes to make the recorded lambda values match the target lambda values. Adjust the fuel cells that way until your cruising AFR's are between 14.5 and 15.0:1.

If you want to keep things simple, enable closed loop. Make sure your narrowband sensor is still connected or the simulated narrowband output of your wideband is wired to the ECU. Enable closed loop in SManager, make sure the correct input pin is selected, and that your closed loop disable is at ~750mbar. The ECU should now be targeting 14.7:1 AFR at cruising/idle.

 

right ok thanks for that. i will give it a go!!

so where the afr is now being a little rich is not going to cause any damage to the engine right?

 

10.6 under boost is kinda rich, sounds like the tuner is erring on the side of caution. I usually tune street turbo cars to 11:6-11.8 AFR at full boost. your AFR's under cruising should be around 14.7, mild load 13.6-12.4. Basically the higher the load, the richer the mix should be up to an extent because the extra fuel provides cooling and a rich AFR will burn less violently and release less energy... way over simplified ... being that rich under full boost won't immediately damage your engine but it can (in some instances) cause accelerated piston ring wear from having unburnt fuel constantly washing off the oil film on your cylinder wall , and sometimes it can cause overheating of the exhaust valves from delay of combustion but I wouldn't worry so much about this. If you put your car on a dyno and run at 10.6 afr full boost and then bring it to about 11.4-11.6 afr you will see an improvement in power across the board.