I rebuilt a 200 block last months and I first started it last week and today I've installed a boost pressure gauge and a wideband lambda to check how it runs.

The car is on stock injectors, turbo and ecu. Only differences are 92,5mm wossners, WRC head gasket, long studs and a little more CR due to head and block machining

On cold start, it show me around an AFR of 16:1.

when hot, it has an idle of around 15,5-16:1, on cruise light pedal near the same. When pressing a little more to atmospheric pressure but without boost it goes to 14,5-15:1 and then when boost come it downs to 13-14:1

Boost spike is 0,9bar and then it goes to 0,6 aprox.


is the first time I own a cosworth but I found it very lean. I was hoping to see around 11,5-12:1 on boost.

what do you think?