Annual Emmisions Test - Help

[Terminal_Crazy]

OK guys just failed the annual emmission test.

Initail tune was way off being based on the wideband and what the car wants.

Limits are
CO % 0.300
HC ppm 200
Lamda 0.97-1.030

Initial test HC was in the 7-800 range lambda was around 1.15


I reflashed with last years bin & with steveo's EEHack (increased timing & Idle speed) managed
CO % 0.00
HC 100-150
Lambda eventually came down to 1.034 so F'in close.

A big part of the issue is the 2x3" tail pipes although covering one up raised the lambda back over 1.11.

I'm pretty certain there are no leaks on the pipes, even the cutout has been blanked off.

What should i play with in the tune. It got better as the o2's heated up so fan temps will be raised.

Any other suggestions please.

Cheers
Mitch

[1project2many]

Your tests appear to show the engine running slightly lean. Does your vehicle use catalytic converters? Could you post all three measured values for the initial test?

[Terminal_Crazy]

Your tests appear to show the engine running slightly lean. Does your vehicle use catalytic converters? Could you post all three measured values for the initial test?

Yes it has a cat.

The current tune has been with a wideband as the car drives so much better. I basically just switched closed loop back on and adjusted the BLM's back.

What's strange is the lambda was way over even though i thought i'd be rich and the HC were 7-800.

initially
CO ?? can't remember but it was the first to pass.
HC 7-800
L 1.11 - 1.14


I switched back to the tune from last year and bump timing up & rpm's to about 1200

That dropped to about
CO not much dropped 0
HC 250 dropped to 132
L 1.11 dropped to 1.04

as I raised the rpm & timing the figures dropped.
As it warmed up the igures dropped some more.
As he covered one of the tail pipes the lambda actually dropped down to about 1.05 ish
best reading on test was 1.04

Thanks
Mitch

[1project2many]

The converter could be thought of as it's own engine. As such it is powered by fuel (HC and CO) in the exhaust as it reacts with any oxygen exiting the engine. With too much or too little of either the "engine" of the cat struggles to run.

Fuel and oxygen start reacting in the combustion chamber and will continue reacting as the gas is pushed into the exhaust manifold and into the exhaust pipe. As the exhaust cools and the amount of inert CO2 increase the reaction slows. When you advance ignition timing you give fuel and air more time to react in the engine before it is forced out the exhaust. The reaction spends more time in the cylinder and around the heated exhaust valve and continues longer. More reaction time means there is less fuel and less O2 being dumped down the pipes. Less fuel and O2 means less for the "engine" that is the converter.

It may seem counterintuitive, but retarding timing some on a system with cats can help clean up tailpipe emissions. While the exhaust from the engine may be "cleaner," having lower O2, CO and HC readings, it also does less to keep the cat warm which can ultimately result in the cat failing to cause the gases to react before they are measured at the tailpipe. The apparent lean reading, generated through WBO2 tuning, also suggests that timing is a bit on the advanced side.

Increasing engine rpm cleans up emissions for several reasons. Among others, the increased volume of exhaust gas carries greater heat energy to the cat which helps the cat to react the remaining combustibles in the exhaust. Increasing idle speed while increasing spark advance is somewhat counterproductive because, although you add more heat, you are reducing the components that the cat reacts and increasing the components which cannot react.

The easiest way I can think of to check the effectiveness of decreasing advance on emissions is to check converter temp before and after the change. If you're seeing temperature around 200 - 325 C (400 - 600F) the cat is barely above the "light off" temperature. If temperature as 650 to 700 C (1200 - 1400F) the cat is working vigourously and tailpipe HC and CO should be fairly low. If you see temperature approaching 1100 C (2000F) the cat is in danger of meltdown.

Ultimately what you are doing is trying to balance engine efficiency with the catalytic converter's ability to burn fuel. For your combination you may have found the point where the engine burns fuel so well the converter is unable to do its job effectively.

[Terminal_Crazy]

Wow, what a brilliant explanation.
That all makes sense and i don't think the cat has ever been that hot.
I will have a play tomorrow and see what results i get.

Thankyou
Mitch

[Terminal_Crazy]

OK
I found a pinhole leak on the cutout Y so filled that with HT silicone for now.
The cutout has a little bypass/bleed hole by the shaft so swapped my blanking plate in before the cutout.
I've blanked one tail pipe with a bean can. The reversions would suck the can in and out of the tail pipe which i think will make the most difference.
on the previous bin CAT temp was around 120.
The car has only been idling today, initially for about 20 mins.

I raised the fan on temps back to stock so it's idling around 105 degrees.
Closed Throttle Timing i dropped back to stock values & raised idle speed.
It's actually quite sweet.

Idle speed 1100
Timing around 27.
MAP has dropped slightly
CAT temps only reach 250 - 340 °C front to back (2-3 times higher than before ), a decent drive will hopefully raise this.
On the last test the car did sit for half an hour after driving there.

I dropped timing to 20° but that didn't seem to affect the cat temp any. 27 seems OK for now.
The Inj PW increased.
37° 1.7x
27° 1.9x
19° 2.1x
so it is using more fuel than before.

I also measured the temp of the tail pipe at around 105° and that also is noticably hotter and doesn't smell.

BLM's were sitting at 132 132

Wideband is averaging 15.1 rather than 15.2 and seems more stable than before. It used to bounce 14.8 -15.8 where now it reads 14.7-15.3


Results looking good so far.
Any other suggestions I can try before retesting?


Thanks
Mitch