1UZ and IM240 Emissions Test for Engineering

[marc280]

So I've been building a Nissan 280zx with a 1UZ for a while now (I know it is a Nissan body for you Nissan haters out there, but 1UZ is good right ) and it is in the process of getting engineered. I used all of the stock emissions gear that came with the engine (from a 92 Soarer) with the only change being I moved the cats back a bit from the engine so I could fit them under the car while still maintaining ground clearance. Unfortunately because of this the guy doing the engineering cert said it needs an emissions test.

I had the test done yesterday, but unfortunately it failed due to NOx being too high. I also had the problem that the car wouldn't start just before the test (perfect timing) and I traced it back to a dodgey relay, although in the process of finding out that the relay was the problem I blew the fuse from the alt to the battery (battery is in the boot) so it wasn't charging. So now I'm not sure if the low battery voltage was effecting the emissions or if it was always going to fail.

I've attached the scans of the test results and you can see from the first test that the cats being further back isn't helping as the emission are much better on the second run after they are hot.

Any idea's on how much battery voltage would effect emissions? If it was just a little richer on the second run it looks like the second run would have been a pass....

[George]

a scanner is your best friend. make sure all o2 sensors are fresh and operational, and fuel trim is within +-5%. as long as they are, battery voltage won't affect the emissions.

btw, NOx usually has something to do with ignition advance, be sure to check it too

[marc280]

yeah that is where I'm planning to start, I need to check if the ECU is throwing any codes any make sure nothing strange is going on and then also check the AFR's

Does anyone know what effect E10 will have compared to PULP? I've heard of people being able to pass emissions easily with E85 (and a retune) so I'm guessing E10 would help??

[dumbass]

What cats did u use
Nearly all aftermarket cats won't pass emission tests
U need good factory ones

U can get aftermarket ones to pass sometimes
They need to be euro 4/5 compliant and about 400 bucks each
They need to have a 400 cell count

[marc280]

I used the standard Soarer ones, as I thought similarly that most 'high flow' aftermarket cats aren't usually too concerned with emissions and the factory ones should be pretty good. I don't know exactly how many kms the donor engine has on it and I'm guessing that the performance of cats does get worse with age, so perhaps the results would get better if I used some newer cats. I found this autospeed article which makes me think that some new aftermarket cats might not actually be that bad....

http://autospeed.com/cms/title_Dirty...0/article.html

Also did a bit of searching and found very conflicting information how emissions are effected by using E10 compared to normal petrol. In the paper shown in the link below it discusses emissions and generally THC and CO are reduced with ethanol fuels, however NOx emissions don't seem to have a clear trend....

http://www.engr.ucr.edu/~heejung/pub...12-ethanol.pdf

Found one other paper that was really good (I've lost the link but will try to find it again) and it compared normal petrol to E10 on a range of different cars at different temperatures and it also showed no clear result on NOx. But from what I can see older cars with less advanced emissions gear generally seem to have increased NOx with E10 and the researchers seem to put this down to the cars running leaner and the computers not compensating as much as what newer cars do, which would make sense. So considering that the Soarer ECU is from 92 I'm going to take a punt and say that it probably doesn't adjust the mixtures as much as some newer cars would especially seeing as it just has single wire O2 sensors.

I've just got a techedge wideband, so the next job it to get that installed and then see what the AFR's are doing.

[petergoudie]

High NOx can mean the combustion temperature is too hot. The first thing I looked at on the test results was the fuel usage. This could indicate it's too lean. You did not say if you were running the stock computer.

Also, is there any chance you could get the car hot before the test just in case it was a cat issue. Volvo put electric heaters in some of their cats so they would heat up quicker.

Below I've cut & pasteed three items from the internet.

"When combustion temperatures exceed 2500 degree F., atmospheric nitrogen begins to react with oxygen during combustion. The result is various compounds called nitrogen oxides (NOX), which play a major role in urban air pollution. To reduce the formation of NOX, combustion temperatures must be kept below the NOX threshold. This is done by recirculating a small amount of exhaust through the "exhaust gas recirculation," or EGR. valve.

The EGR valve controls a small passageway between the intake and exhaust manifolds. When the valve opens, intake vacuum draws exhaust through the valve. This dilutes the incoming air/fuel mixture and has a quenching effect on combustion temperatures which keeps NOX within acceptable limits. As an added benefit, it also reduces the engine’s octane requirements which lessens the danger of detonation (spark knock). "


"High NOX is caused by high cylinder temperatures and a bad catalytic converter. I see that you have a new converter. It is important that the EGR valve is working properly because it works by cooling the cylinder temperature. If the spark plugs are the wrong heat range, it could cause high NOX. Also if the vehicle is running too hot, it can also cause it.


If you have high mileage on an older car, it is sometimes hard to pass the NOX. You could try putting a 180 degree thermostat in. By making the car run cooler it should help the NOX but it may hurt the hydrocarbons. You'd have to try it to know if it helped. You can also try wiring the fan so it runs all the time during the test. This might do the trick."

"10) Oxides of Nitrogen readings. Oxides of nitrogen (NOx), including nitric oxide (NO) and nitrous oxide (NO2), are formed if the combustion temperatures within the combustion chamber exceed some 2,500 degrees F. This can occur when the engine is under load. When excessive temperature conditions exist, the greatest amount of NOx is typically produced at the stoichiometric point (AFR 14.7 or Lambda of 1.0) as the engine is under a light load. If the combustion process within an engine is burning fuel at or near stoichiometric point, NOx levels on acceleration will typically read significantly higher than those measured at cruise and during deceleration. Typically, the NOx readings at idle will be 0 PPM.

11) High NOx Readings. Circumstances that can lead to abnormally high NOx emissions are:

* Malfunctioning EGR valve

* Lean fuel mixture (AFR above 14.7, Lambda above 1.0)

* Improper spark advance

* Thermostatic air heater stuck in the heated air position

* Missing or damaged cold air duct

* Combustion chamber deposits

* Malfunctioning catalytic converter

* Catalytic converter intervention and NOx concentrations
High NOx readings at the tailpipe are an clear indication that there is a problem in at least one part of the system, but an NOx reading that appears within "normal" ranges or is only modestly elevated is not necessarily a reliable indicator of proper or even acceptable system performance. NOx readings at or near "normal" are possible, and not uncommon. From a malfunctioning engine equipped with a properly functioning catalytic converter. In such circumstances, truly elevated pre-catalytic converter NOx levels will be masked by the catalytic converter and the potential for an NOx problem must be further evaluated in the context of other readings of abnormal gas concentrations and AFR / Lambda readings."

[petergoudie]

More NOx info on net:

We at Discount Converter sometimes get calls from customers who have been told they need a new converter because their vehicle has tested showing HIGH NOx readings. A catalytic converter WILL NOT by itself reduce HIGH NOx emissions. If you are having high NOx readings with your vehicle please read the article below...might just answer your questions why?

NOx can be formed by many component failures and system malfunctions - anything that allows the combustion chamber temperature to exceed 2300 degrees Fahrenheit. For example, if the cooling system is utilizing pure water, it will absorb combustion heat and obtain its boiling point rapidly, leaving an air pocket around the combustion chamber. The air pocket will become a hot spot allowing for the combustion chamber temperature to rise. Equally bad is 100% antifreeze, which forms a blanket around the combustion chamber, keeping heat in and allowing the combustion chamber temperature to rise.

Rust surrounding the cooling jacket surface will create the same blanket around the combustion chamber. Poor flow through the radiator, as a result of a blockage or poor circulation, or a partially closed thermostat or limited flow from the water pump, will prevent the high temperatures from escaping through the cooling system. This temperature increase will cause preignition, allowing the oxygen to prematurely oxidize the hydrogen, reducing the available air and fuel during spark ignition. As a result, oxygen will be limited to complete the oxidation of the hydrogen and formation of carbon and oxygen into carbon dioxide will be limited. In this case the gas meter will read high HC, low CO, low 02, low C02, and high NOx.

As the piston rises during the compression stroke, the opposite force of compression in the upward direction and the downward force created as a result of preignition will cause the piston to rock, slapping the piston skirt against the cylinder wall, causing a knock. As a result of an engine knock, we should see the scanner knock reading indicate yes, with a command to retard ignition timing. The secondary ignition scope should have a higher than normal firing line. With excessive preignition, the early flame front comes in contact with the spark ignition flame front. This will result in high HC, low CO, high 02, low C02, and high NOx. The horsepower of the engine will suffer as well.

A lean condition as a result of a false signal from the oxygen sensor, an out-of-calibration MAP sensor, plugged injector, low fuel pressure, low fuel pump volume, or a vacuum leak will cause NOx as well. Under these conditions the oxygen will oxidize the hydrogen and the carbon, creating extreme combustion chamber temperature. This acts much like a cutting torch used to oxidize the carbon atom of the metal. As the temperature climbs the nitrogen atoms will separate and form with the oxygen atoms to create NOx. As the oxygen is used to form NOx, the oxygen will be used up, causing a lot of hydrocarbons to be unused.

The gas analyzer will read high HC, low C0, high 02, low C02, and high NOx. The secondary ignition scope should have a higher than normal firing line, and longer than normal spark duration. The scanner would read zero to low oxygen sensor voltage and a lean condition. As a result of running lean, the additional HC from a richer mixture is not there to absorb the heat. Therefore, the CO molecule needed in the catalytic converter to cause the catalyst to reduce minor levels of NOx to nitrogen and carbon dioxide will not be created. In no way will a catalytic converter reduce excessively high NOx levels.

If the EGR system were not functioning properly, as a result of a plugged or partially plugged passage, inoperative EGR valve, inoperative vacuum control system, or an electronic malfunction, the controlled exhaust flow would not occur. This would allow the combustion temperature to rise. The gas analyzer would see high HC, low CO, low O2, low CO2, and high NOx as result of a faulty EGR.

Carbon build-up on top of the piston or on the cylinder walls may also cause preignition. This would give similar results to the cooling system issue. The carbon build-up could be as a result of running extremely rich for any length of time. Therefore, when repairing high CO emissions failures, always assume that carbon has formed. This type of carbon can even be caused by oil consumption, which will also cool the combustion chamber temperature. Carbon on the throat of the valve will absorb fuel, causing a lean condition and giving a similar result as to the previous lean condition. This type of diagnosis may require a borescope to visually inspect pistons, cylinder bores or valves. To repair this, a chemical top end cleaner may help. If the vehicle is not running rich, the gas analyzer will read high HC, low CO, high O2, low CO2, and high NOx. The reason for the high O2 is that the carbon will assimilate a lean ignition misfire. The scanner would read low oxygen sensor voltage. The secondary ignition scope should have a higher than normal firing line, and a possible appearance of second firing line in the spark line.

A worn or slipping timing belt can certainly increase internal temperatures. If the timing belt or timing chain has excessive slack, the cam timing will be retarded. The camshaft will be behind the crankshaft resulting in the camshaft lobes not opening the valves in the proper relationship to the piston. The intake valves during the intake stroke will open late, causing the air to continue entering the cylinder later than required. As a result, the compression pressure will increase at the top of the compression stroke and temperature will reach its maximum later on into the stroke causing a longer oxidation period which results in extreme combustion temperature. As a result of late intake valve opening, the vacuum will be low, causing the MAP sensor to see a load adding more fuel, causing high CO. The gas analyzer will read high HC, high CO, low O2, low CO2, and high NOx.

If the base timing is advanced too far, the spark plug will ignite the air fuel mixture early, causing the combustion temperature to rise as the compression stroke continues, causing NOx to form. With a very early flame front in the compression stroke, as a result of advanced ignition timing, the temperature created as a result of early oxidation will cause the temperature created during compression to rise extensively.

The exhaust valve seating surface is not just to seal the cylinder airtight, but to provide a means of removing heat from the valve and disbursing it to the cooling system. An exhaust valve that is improperly seated will not transfer heat. As a result, the valve and its seat will rise in temperature, causing preignition. This will result in high HC, low CO, high O2, low CO2, and high NOx.

So as you can see, excessive NOx is caused by high internal temperatures. Unfortunately, there are any number of factors that can increase combustion chamber temperatures past the magic 2300 degrees. Fortunately, with your trusty five gas analyzer and a little reasoning ability, you're in great shape to isolate the problem, replace the faulty components or make adjustments as needed, and send the motorist on their way with a better performing and lower polluting vehicle

[marc280]

Wow that's quite a bit of info! Thanks Peter.

It would seem that there are quite a few things that could cause a high NOx reading.... I'm using the stock computer, so the ecu settings should be ok unless the intake or exhaust changes have been enough to make a difference. The engine doesn't have an EGR valve (and this year model of the engine didn't have them at all it seems) so that isn't available to help.

I think for the next test I'll make sure that the exhaust is nice and hot before it goes into the test cell, so hopefully that eliminate any issues with the cats being cold.

Also the way that I had mounted the O2 sensors may not have been the best as I didn't realise that the O2 sensors should be mounted in a way that any condensation in the exhaust should drip down off the sensor... There is a chance that they may have been damaged as the car has had quite a bit of time idling and short runs as I've been testing things and any condensation could have built up on the sensors as they were mounted just below horizontal. I'm welding in some new bungs in the exhaust so that the new sensors for the wideband will be mounted in a better position and then once that is going I'll check for ecu codes and check the AFR's.

[petergoudie]

Generally, there are two & three wire O2 sensors. The 3 wire has a heater built in so it heats up fast and starts the computer doing its work earlier. If you have a 2 wire sensor put it close to the engine so it heats up faster.

[marc280]

The sensors I have are only single wire sensors, I don't know why this particular engine only has single wire when other 1UZ's from the same year have four wire, but that is how it came from the factory.

I decided to install two new aftermarket (Magnaflow) cats so that I could get them up close to the engine. I've seen some people that have had good results with them in passing emissions, so hopefully they will work well for me too. After getting the cats installed I seem to have unleashed a whole lot of other problems....

When I first started the car after installing the cats the engine was hunting at idle from about 1000rpm to 2000rpm. I know that the Idle Speed Control Valves can be a bit of a problem with the idle, so I pulled it of to check it and there was a little bit of carbon buildup, but nothing that should stop it from working. While it was out I tested in on the bench by applying 12V to the pins B1 and B2 and then you can cycle around the four pins tapping it to earth to simulate what the computer does. It was all working ok and stepped in and out. I deliberately closed up the gap a little before putting it back in beacuse it was pretty much wide open when I took it out and I'm pretty sure that is what was causing the hunting idle. After reinstalling it the idle is now really low and it still isn't adjusting the idle up or down.

I checked that it is getting battery volts back at the ECU on the four ISC pins and that the computer has a good ground at E1, but the computer doesn't seem to be moving the stepper motor... In the factory manual it says that you should be able to hear it clicking when you turn the engine off and it isn't doing this either.... So at the moment I'm thinking the computer may be stuffed...

After manually adjusting the idle enough to get it to idle I took the car for a drive and now that I have a wideband I could check the mixtures. I found it was running really lean everywhere. At light throttle it was up around 1.7 lambda which obviously isn't good and probably a pretty good explanation for why it didn't do so well in the emissions... When trying to accelerate it was very hesitant until about 3500rpm and then accelerate ok , but still quite lean at about 1.3 lambda.

I tied pulling of the AFM and with it off the car didn't really want to start so I think it is working ok.

So sorry for the long ramble, but after all that does anyone have any ideas on where to start looking! I do have a Haltech E11V2 sitting in the garage just waiting to go on but I wasn't planning on using it yet becuase the engine is pretty stock and I thought the stock computer would easily pass emissions... I'm starting to think I should just get a patch lead and have it tuned...

[dumbass]

alot of late model motors run lean
my 1uz used to run lean up untill about 90 % throttle
then the flood gates would burst open
mixtures would go from around 14 all way down to 10 to 1 right after 90 to 95 % throttle in any rpm and any load
just as soon as tps went full it smashed injectors open

also u should never ever touch stuff like idle screw or any adjustment on the throttleboy
u r just fking things up because the problem is elsewhere so fix the porblem rather than a temp cure
rather than fking with wideband put a bloody scanner onto it and read what ecu is telling the injectors to do
whether is 1 or 4 wire o2s the ecu is matched to whatever it needs so dont worry bout that
my 1 wire o2s never had any issues
also test yr wideband on another car
how do u know thats not faulty
they are very cheap these days and made in china so we all know ho wcrap shit is when it has chinese fingerprints on it

[Sciflyer]

Early UZZ3x Soarers are single wire sensors, I think the change to 4-wire was in 1994.

A guy I know got his supercharged V8 Soarer to pass IM240 and it also took a couple of tries but that was with an Adaptronic. Also needed to run aftermarket cats

and yes lean-ish mixtures at anything less than high load/rpm and then overly rich after that is standard fare for these ECUs.

[SHEPPO3930]

my ca18det didnt pass emissions the first go, but the engineer said to take it for a spin around the block to ensure the cat was "up to temp"... 16psi and 5km of spirited driving i brought it back into the workshop and it was tested again, and passed. moral of the story, make sure the cats are hot!

[CrUZida]

There are easier ways of making the cats hot, just unplug one of the ignitors for 2 minutes, let it run on 4cyl's. The cats will be glowing red in no time.

Marc, based on what you've said about your idle, I don't think you've wired the engine up correctly...
Sort that out before going back.

[CrUZida]

Also, in my experience, these engines will sit smack on 14.7:1 AFR (with good o2 sensors) for almost all conditions at low throttle.
At about 30-40% throttle they'll begin to go richer (13:1ish), and then as you squeeze the throttle they'll go richer again.

What this converts to in lambda I have no idea.