[Supras] Emissions failure

[Jeff Corbat]

I'm quite surprised to hear that the NJ emis. test is conducted at 15MPH. 
That's about as unrepresentative a test as one could devise.  I'm in 
Milwaukee and the WI test procedure is dramatically more difficult.  The 
test conductor is required to cycle the speed from zero to 25 then down to 
zero then up to 60 and then oscillate the speed for several cycles.  In a 
stick, the test speeds seem to be chosen to drop/raise enough to require 
shifting up/down thus causing moments of high engine load.  There is a 
computer monitor which indicates the required vehicle test speed and the 
test driver must follow its instructions closely or the test will reset. 
Our waiver limit is $450 and only work performed by certified emission shops 
counts against a waiver.  Not surprising...the average emission repair bill 
comes out to around $400.

Obviously, vehicles '96+ are simply plugged in.  There is talk of 
decommissioning the dyno centers since they are expensive to maintain.  The 
theory is that there would be emission kiosks where owners could plug their 
cars in periodically and perform a self-test.  Not sure exactly when this 
would happen but I can imagine that most pre-OBDII vehicles will be retired 
in the next five years...certainly within the next ten years.

Jeff
http://www.uwm.edu/~jjcorbat/supra


----- Original Message ----- 
From: <berniek at technicaldevelop.com>
To: "Mike Scharf" <skibum1957 at comcast.net>; <wwt3198 at yahoo.com>
Cc: <Supras at supras.com>
Sent: Friday, August 04, 2006 8:44 PM
Subject: Re: [Supras] Emissions failure


>I live in NJ too, and have found that if you happen to be a little careless 
>in setting the spark timing to late by 10-15 degrees, the HC and CO content 
>decrease.  I have read but not observed that the NOx emissions will 
>increase with too much retard, however.  Are you certain the EGR is working 
>correctly?  Are the valve passages plugged?  The NJ dyno test is conducted 
>at 15 MPH which may or may not open the EGR valve (it is vacuum operated 
>from a port in the throttle body).  If the spark is retarded, more throttle 
>will be required to reach 15 MPH with the load applied, possibly opening 
>the EGR valve to reduce NOx.  EGR reduces the high temperature spike in 
>combusion, which causes fixation of nitrogen to nitrogen oxides.  Years 
>ago, a GM engineer characterized it as "throwing an ice cube into a bowl of 
>hot soup".
>
> I have gotten through inspection with a '92 V6 maxima (mule car for us) 
> with fuel injectors partially clogged to the point where the idle was 
> rough by being "careless".  Recently changed all of the injectors on that 
> car (bitch of a job with the upper intake manifold) and the HC dropped 
> only slightly although the idle and purr of the engine under load are much 
> better.  HC was 84 PPM, CO was very low as was NOx, just a week ago at the 
> Randolph inspection station.  HC is primarily caused by a misfire, while 
> CO is caused by incomplete (rich) combustion.  I changed spark plugs in 
> that car a couple of weeks ago, a very important consideration for HC.
>
> The Supra always passed, and is essentially stock except for mild boost 
> increase and a large but quiet HKS exhaust.  It is out of commission now 
> due to a BHG, and I'm still rebuilding a JDM engine for it.
>
>    Sun used to make a "do it yourself" HC and CO analyzer which I bought 
> from JC Penny maybe 25 years ago.  It works by exhaust gas thermal thermal 
> conductivity using two measuring cells:  One for the raw exhaust gas and a 
> second after an activated charcoal filter to remove HC but not CO (they do 
> not tell you this, but the charcoal needs to be outgassed periodically by 
> removing it and oven heating it at 400-500F).  They use simple analog 
> electronic circuitry to do the subtraction to differentiate CO+HC to 
> separate readings.  One of these might be available on ebay.  It was a 
> couple of hundred dollars, as opposed to $2000-$3000 for infra-red 
> absorption types on the market at the time.  But prices of those on ebay 
> might be low as well.  It pays to experiment in your garage before going 
> to inspection.
>
>    Good luck.
>
>        BernieK
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