Passing IM240 Emissions Test - RB25DET

[Black 1via RB25det swap]

Righto, in need of some tips for young players!

Just towed the project car from Wodonga to Sydney for its IM240 test. It's an S13 with an RB25DET engine swap. Running stock injectors, a Walbro 255 fuel pump on 98 Octane at the moment. Close to stock turbo, APEXI Power FC computer and a 2.5 inch exhaust with 600 cell cat converter (new).

Had made sure to get the car tuned as emissions friendly as possible (or so I had thought) in preparation for the test. After driving the 6 hours to the testing centre, I bombed the test pretty badly namely the car was running rich at Idle but was passing the test at highway speeds. The testers suggested a better tune and maybe new oxygen sensor as it may be lagging. I'm also reading that switching to E85 and re-mapping may solve the issue. Is it as simple as that or will switching to E85 require major modifications to the engine etc?

Any advice of avoiding this debacle in the future?

[Dose Pipe Sutututu]

E85 will pass with flying colours provided you get the cat hot enough to toast off the NOx and CO2 at idle, get it idling at stoich & drop the timing a bit (but you're using a PowerFC so a cheater's way would be to retard the CAS)

[Black 1via RB25det swap]

Sorry just to clarify what was stoich meant to mean?

[Dose Pipe Sutututu]

14.7 AFR

[Kinkstaah]

You would have had to do something special to bomb the test in a S13, given it has much laxer requirements than my R34 (which passed with a cammed V8)

Do you have cams in your RB? It will really f*** with your idle. E85 can help or hurt, depending on what part of the test you came up short in. The testers have a report but I don't know if they supply it if you fail (I got my copy)

[Butters]

Passed it with an RB26 stock cams, big turbo, once on U98 and just recently on E85.

E85 is easier.

Euro 4 cat helps.

Closed loop also helps.