Help request - NOx doubled in dyno inspection

Hi,

This is the same situation I had the last time I went for inspection... Nox on my 91 BMW 318i failed. Only this time, it has doubled from the accepted level! My car an E30 318i with the M42 1.8L engine was designed without an EGR or any other sort of NOx control, except, i suppose for the catalyst in the cat converter.

Background: For reference, in 2003, my emissions (dyno test) were as follows: NOx 1114 (standard is 1134) HC 97 (standard is 146) CO% 0.33 (standard is 0.82) CO2% 14.1 O2% 0.2

Failure in 2005: NOx 1167 HC 96 CO% 0.35 CO2% 15.3 O2% 0.3

Replaced cat converter, reading that passed in 2005: NOx 1074 HC 133 CO% 0.34 CO% 14.8 O% 0.2

My failure today: NOx: 2126 (DOUBLED!!!!) HC:161 CO%:0.54 CO2%:14.1

As a reference, my 98 Chevy truck (owned since new) had these results on its last dyno test (currently exempted because its an OBDII vehicle, so these are a little old, but done on the same system): NOx 16 HC 7 CO% 0.01 CO2% 15.2 O2% 0

Spark plugs are very clean and correctly gapped, etc., I even ran the new Amsoil PI through the tank just before to ensure that CCs, etc. were cleaned out. No dice.

I do have a dinan chip, Ill be removing it as of right now, to hopefully be able to pass... The car runs great and gets me good fuel economy, Id hate to have to spend $500 on senseless repairs to get a waiver, just because this car never came with an EGR from the factory (by design).

UGH!

Any thoughts or comments would be most appreciated. I have heard that ingnition coils (this car has a distributorless system) going bad can cause funny problems like this. Any thoughts???

Thanks,

JMH

Reply to
JMH
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Nox is a direct function of cylinder temps, this is affected by timing, engine temps, fuel mixture, compression ratio, and of course the cat is the final clean up component. A older high mileage vehicle could always be at risk for this issue, try retarding the timing slightly, maybe run carbon cleaner thru the intake, no magic bullet here.

Reply to
maxwedge

Was the replacement cat an oem unit or aftermarket?

Reply to
Steve Austin

It was an aftermarket, no name no less...

If needs be, Ill need to spend some $$$ to get my emissions waiver ($450 must be spent). I hate throwing parts at perfectly operating cars, but if that is what must be done, then Ill likely obtain a DEC (unless someone suggests another brand or to go OE only) cat setup for my car (the aftermarket was simply cut and welded in), as Im sure a $250 cat converter is not of the highest quality.

Thanks!

JMH

Reply to
JMH

When did the chip go in?

Reply to
Steve Austin

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