mnr vortx f20c

as some of you may know,my s2000 engined kit car is due for its test this friday and has been in for mapping at daytuner in harrogate. my power map with spoon n1 was around 180 rwhp but my exhaust had a crack in the collector so maybe a few more to be had.
but with my IVA (kit car test) map with the cat on they could not get my emissions down what so ever. lamba was spot on,hydrocarbons spot on but co2 was high and no matter what they did they could not improve it. even replaced the cat with another proven one to make sure it was ok.but still no good.even with a totally programmeable ecu (dta s60)
i am not a mechanic by any means but if i remember correctly (as i fit the engine over 2 years ago)all i have done is bypassed the coolant heater circuit, removed ac pump and fitted new belt, blanked off the egr valve and removed the air pump and blanked off an air valve?
any ideas what could be the cause? asd my test is friday,and is £450 which i have paid and non refundable. cheers

Si2k

Sounds like you are burning too much fuel at idle. How are you controlling the idle ?

Si2k

Also any cracks won't be helping.

mnr vortx f20c

i may sound daft but how do you mean controllibng the idle? the dta s60 ecu seems to be sorting stuff out.

hazzaman

Wouldn't the crack allow air to be drawn in which would cause the secondary o2 sensor to give a false reading, possibly making the ecu over compensate?

mnr vortx f20c

only 1 x o2 sensor on the kit car, in the exhaust collector

B0ZWELL

? do you mean CO?

CO2 should be high as thats what the cat does, turns CO into CO2.

what was the Oxygen reading? this will give a clue to if there is a missfire/air leak etc.

Lanbda 1.000 usually shows that the mixture is correct and it's the cat not doing its job properly but you say youv'e tried another. does altering the ignition timing at idle make enough difference?. is the mixture adjustable or done completly by the Lambda sensor? does it have a high flow cat that needs a lot of warming up?

first things first though is to make sure there are absolutly no air leaks at all in the exhaust system.

Si2k

Are you controlling the idle valve or using ignition to control the idle.

Its possible you are burning too much fuel due to too much ignition retard, hence a high CO2 number.
Fuel + O2 = CO2 and water in perfect combustion.

The fuel could burning ok but releasing power in the exhuast rather than engine hence the engine isnt idling at 3000rpm.

Air leak would have a similar effect on the situation if its hosing in fuel but the air leak is bringing in oxygen making both the ECU and emissions reader think you are at lambda 1 (In reality the engine is rich, but then i would expect excessive HC)