Coc or nox of nissan skyline

[joshuaho96]

3 hours ago, MBS206 said:

Many many moons ago, I was chatting with Andy Wyatt, about his auto ignition tuning. One of the HUGE things he said to me, when tuning for power, right where you hit peak ignition timing for your max torque, dramatically increases NOx emissions. He was finding in testing, particularly on engines you could advance timing beyond peak torque, that backing the ignition timing off a couple of degrees only made for a small drop in torque (compared to if you keep backing it off further the same amount of degrees) but dramatically reduced NOx emissions.

I'd say targetting for 14.7, and he's even mentioned in some scenarios going slightly leaner, and pulling a few degrees of IGN timing will help pass for emissions quite a lot. However, who tunes an RB for emissions

It's surprising you say this because talking to someone who headed Toyota's CARB certification efforts and was now working for Mercedes doing similar things he said he never had a case where he found that it was necessary to reduce ignition timing for that reason. Knock limits yes, but never because of in-cylinder emissions profile. I'm guessing between EGR and the number of TWCs modern cars stack in series it's not really a problem.

37 minutes ago, MBS206 said:

100% agree.

Best bet on an RB will be NEO, but even it will be a long way off.

Emissions is one of the big reasons car manufacturers went to DBW and constantly variable cams. When cruising, open the throttle right up, but reduce dynamic compression so low, that it's basically an unrestricted air pump moving very little air.

I really doubt the NEO is that big a difference. You get what, EV6 injectors, coil on plug, a cold start valve that works off coolant temp instead of basically fixed time constant valve, and... I really can't think of anything else. Not like Toyota where they shipped first gen GDI in the 2JZ-FSE. 

2 hours ago, GTSBoy said:

Yes. All of this.

But even when you get the NOx as low as you can go on an RB, it will no doubt still be way too high. Same with CO and HCs. The tech and the tuning time just isn't there.

Something I didn't realize is that Japan didn't revise their emissions standards for light duty passenger cars between 1978 and 2000. I'm guessing there's a bit of phase-in, but that explains why 2002 killed a bunch of JDM sports cars off all at once. FD3S, A80, S15, Z32, R34, Z15A GTO all died off for that reason. And explains how all these cars got away with no EGR or much of anything other than a TWC and charcoal canister for the longest time.

[MBS206]

1 hour ago, joshuaho96 said:

It's surprising you say this because talking to someone who headed Toyota's CARB certification efforts and was now working for Mercedes doing similar things he said he never had a case where he found that it was necessary to reduce ignition timing for that reason. Knock limits yes, but never because of in-cylinder emissions profile. I'm guessing between EGR and the number of TWCs modern cars stack in series it's not really a problem.

I really doubt the NEO is that big a difference. You get what, EV6 injectors, coil on plug, a cold start valve that works off coolant temp instead of basically fixed time constant valve, and... I really can't think of anything else. Not like Toyota where they shipped first gen GDI in the 2JZ-FSE. 

Something I didn't realize is that Japan didn't revise their emissions standards for light duty passenger cars between 1978 and 2000. I'm guessing there's a bit of phase-in, but that explains why 2002 killed a bunch of JDM sports cars off all at once. FD3S, A80, S15, Z32, R34, Z15A GTO all died off for that reason. And explains how all these cars got away with no EGR or much of anything other than a TWC and charcoal canister for the longest time.

At peak pressure for peak torque, you reach the pressures and temps that produce more NOx. Hit google up. When tuning to reduce COx, timing dramatically increases NOx. It's science.

 

As for changes, there was changes to the inlet plenum/runners to alter air speed for emissions purposes. On the DE model, it has the two different inlet runners that the ECU can swap between too.

[GTSBoy]

Hence why I said earlier that I don't think the turbo Neos ever would have actually qualified as an LEV. I suspect the only actual LEVs that came out of Nissan were the NA Neos.

Still call them all Neos. They all stil have the Neo-ness. Just that they don't all qualify as as LEVs.

[joshuaho96]

12 hours ago, MBS206 said:

At peak pressure for peak torque, you reach the pressures and temps that produce more NOx. Hit google up. When tuning to reduce COx, timing dramatically increases NOx. It's science.

 

As for changes, there was changes to the inlet plenum/runners to alter air speed for emissions purposes. On the DE model, it has the two different inlet runners that the ECU can swap between too.

Right, but that's in-cylinder, there's the interaction between that and the TWC which complicates things. Pulling out timing to reduce NOx is a strategy I saw in transitional emissions vehicles like stuff from 1974 or so. The two inlet runner system is interesting but I'm not sure it makes a huge difference as far as emissions goes, is it a tumble valve? I've seen stuff like that even in cars from the late 80s. 

[MBS206]

41 minutes ago, joshuaho96 said:

Right, but that's in-cylinder, there's the interaction between that and the TWC which complicates things. Pulling out timing to reduce NOx is a strategy I saw in transitional emissions vehicles like stuff from 1974 or so. The two inlet runner system is interesting but I'm not sure it makes a huge difference as far as emissions goes, is it a tumble valve? I've seen stuff like that even in cars from the late 80s. 

Two inlet runners changes the engines characteristics requiring less fuel to make torque at different points in the rev range.

The smaller diameter inlet runners on the DET increases air flow speed, which improves atomisation of fuel, particularly in low load/idle for better burn, and in specific areas of the engine, (areas you would use when driving normally) increases the efficiency.

All of those items change how efficient the engine is at different speeds. The changes on the neo help slightly to improve emissions where it matters.

The overall improvements won't be the likes of going from an engine built in the 70s to an engine built in the 2000s, it's just a small step. But still leaves it the RB with the best chance of improvement.

 

As for your comment about the whole using a cat to not need to worry about those gases. Two things, no system is 100% perfect. It won't eliminate everything. So reduce the quantity you put into it, you still reduce the output. Two, make that system do less work, and it's likely to survive a little bit longer. Funnily enough to, one trick employed to get cats up to temp, AND to drastically reduce emissions before they get up to temp, is to reduce ignition timing.

[joshuaho96]

3 hours ago, MBS206 said:

Two inlet runners changes the engines characteristics requiring less fuel to make torque at different points in the rev range.

The smaller diameter inlet runners on the DET increases air flow speed, which improves atomisation of fuel, particularly in low load/idle for better burn, and in specific areas of the engine, (areas you would use when driving normally) increases the efficiency.

All of those items change how efficient the engine is at different speeds. The changes on the neo help slightly to improve emissions where it matters.

The overall improvements won't be the likes of going from an engine built in the 70s to an engine built in the 2000s, it's just a small step. But still leaves it the RB with the best chance of improvement.

 

As for your comment about the whole using a cat to not need to worry about those gases. Two things, no system is 100% perfect. It won't eliminate everything. So reduce the quantity you put into it, you still reduce the output. Two, make that system do less work, and it's likely to survive a little bit longer. Funnily enough to, one trick employed to get cats up to temp, AND to drastically reduce emissions before they get up to temp, is to reduce ignition timing.

Yeah I've personally seen the RB26 pull 30 degrees of ignition timing out of the base timing map if the ECU detects a cold start, it nearly starts misfiring because of it around 2000 rpm and it feels like the engine has no power. I'm just surprised that modern OEM control strategies are actually trading off efficiency for in-cylinder emissions. I would expect something like aggressive EGR dilution + tumble generation valve use to improve EGR tolerance to reduce in-cylinder NOx + HC from crevice volume while also reducing throttling loss vs pulling out some timing if not knock-limited.

[MBS206]

2 hours ago, joshuaho96 said:

Yeah I've personally seen the RB26 pull 30 degrees of ignition timing out of the base timing map if the ECU detects a cold start, it nearly starts misfiring because of it around 2000 rpm and it feels like the engine has no power. I'm just surprised that modern OEM control strategies are actually trading off efficiency for in-cylinder emissions. I would expect something like aggressive EGR dilution + tumble generation valve use to improve EGR tolerance to reduce in-cylinder NOx + HC from crevice volume while also reducing throttling loss vs pulling out some timing if not knock-limited.

It's all about reducing the overall output. Reduce the source of it, you have wayyyy less to deal with in every other step and trick you play with.

It's why something like a modern vehicle, so VW, Audi etc, there's thousands of tables for the ECU to calculate what it should be doing with the engine.

 

Why would you NOT reduce emissions the most effective way possible, when it has very minimal tradeoff, AND manufacturers are always struggling to meet the current standards.

[joshuaho96]

1 hour ago, MBS206 said:

It's all about reducing the overall output. Reduce the source of it, you have wayyyy less to deal with in every other step and trick you play with.

It's why something like a modern vehicle, so VW, Audi etc, there's thousands of tables for the ECU to calculate what it should be doing with the engine.

 

Why would you NOT reduce emissions the most effective way possible, when it has very minimal tradeoff, AND manufacturers are always struggling to meet the current standards.

Regardless, it doesn't seem wise especially on RBs to actually chase MBT. Timing scatter is the big one on stock CAS, even if that's fixed overshoot is worse than undershoot. 

[GTSBoy]

4 hours ago, joshuaho96 said:

Yeah I've personally seen the RB26 pull 30 degrees of ignition timing out of the base timing map if the ECU detects a cold start, it nearly starts misfiring because of it around 2000 rpm and it feels like the engine has no power.

I don't think that's what you're seeing. Something else doing that. The only time I've seen it get so retarded is when it's trying to control idle (in which case we're not talking about mapped timing tagets anyway) and when there is an extreme coolant temperature sensor fault.

The RB26 ECU is essentially the same as the 20 ECU and I knew that ging inside out. There is no facility for it to retard that heavily on cold start. The OEMs never used to do it back then. I mean, shit, the catalyst is abotu 3 miles down the exhaust anyway. Early light-off was just a twinkle in some EPA arsehole's eye back then, not a regular engine control strategy.

[joshuaho96]

53 minutes ago, GTSBoy said:

I don't think that's what you're seeing. Something else doing that. The only time I've seen it get so retarded is when it's trying to control idle (in which case we're not talking about mapped timing tagets anyway) and when there is an extreme coolant temperature sensor fault.

The RB26 ECU is essentially the same as the 20 ECU and I knew that ging inside out. There is no facility for it to retard that heavily on cold start. The OEMs never used to do it back then. I mean, shit, the catalyst is abotu 3 miles down the exhaust anyway. Early light-off was just a twinkle in some EPA arsehole's eye back then, not a regular engine control strategy.

Dunno what to tell you, when I look at it on Consult I can see this warmup timing map kicking in around 40C coolant temp and it sticks around for a while: 

At part throttle on the normal base timing map it peaks around ~43 degrees of timing or something like that, this warmup timing map drops it to like 12-15 degrees. 

Edited March 15 by joshuaho96

[soviet_merlin]

On 13/03/2025 at 2:25 PM, Murray_Calavera said:

I wasn't trying to game the system when I had this test done, the tune was as I drive it every day. 

Where did you get the test done? What did it cost? Can you just book an appointment? And I presume it's independent so failing would not mean suddenly having an unregisterable car?

I would like to make some exhaust changes on my car and would love to get before and after results to see how much of a difference it makes. If it's in Botany even better as that is pretty much local.

[Murray_Calavera]

13 minutes ago, soviet_merlin said:

Where did you get the test done?

At the Botany heavy vehicle inspection centre. At the time there were only 2 locations that did IM240 testing for free, the other location was at Penrith.

I did a quick google, seems like the Botany and Penrith inspection centre is closed now though

22 minutes ago, soviet_merlin said:

What did it cost?

About an hour of my time. 

23 minutes ago, soviet_merlin said:

Can you just book an appointment?

At the time you could. They are closed now  

26 minutes ago, soviet_merlin said:

And I presume it's independent so failing would not mean suddenly having an unregisterable car?

No it was Government run, the site was attached to the RTA from memory. The guys running it at the time were awesome, if you didn't pass the test, they handed you the results and said make changes to your car/tune and have another go later. You drove in registered, failed, and drove out registered.  

Obviously though if you were defected, sent there, failed. You remained unregistered. 

29 minutes ago, soviet_merlin said:

I would like to make some exhaust changes on my car and would love to get before and after results to see how much of a difference it makes.

From my 5 minutes of research (have a look at the date on my test results) looks like things have changed. So, I can't see any way to get this test done for free now

Seems like you'll need to call around the engineering places doing the Vehicle Safety Compliance Certification Scheme or call around workshops with a dyno and try and get a RG240 test. No idea how expensive that is though or how easy it is to find a place offering it. 

Bit depressing learning about this now. The first car I had engineered in NSW cost me about $250 all up.... So kids these days can't buy houses, looks like getting your car legal and engineered in NSW is another thing on the list of things they can't afford. Great. 

[GTSBoy]

24 minutes ago, Murray_Calavera said:

So kids these days can't buy houses, looks like getting your car legal and engineered in NSW is another thing on the list of things they can't afford. Great. 

Just another barrier put up to stop cars being modified. When we're all driving Chinese sewing machines, you won't want to modify it anyway, and you'll likely already have slashed your wrists and be locked up in a padded room for your own protection.

[soviet_merlin]

On 21/03/2025 at 1:53 PM, Murray_Calavera said:

At the Botany heavy vehicle inspection centre. At the time there were only 2 locations that did IM240 testing for free, the other location was at Penrith.

I did a quick google, seems like the Botany and Penrith inspection centre is closed now though

No it was Government run, the site was attached to the RTA from memory. The guys running it at the time were awesome, if you didn't pass the test, they handed you the results and said make changes to your car/tune and have another go later. You drove in registered, failed, and drove out registered.  

Obviously though if you were defected, sent there, failed. You remained unregistered. 

From my 5 minutes of research (have a look at the date on my test results) looks like things have changed. So, I can't see any way to get this test done for free now

Thanks for actually answering every single point! I noticed the date only after posting. And yes, looks like things have changed a little bit since then.

FWIW, looks like Government Gazette No 253 has the current emissions test procedure. Sounds pretty reasonable altogether. One thing I learned from this is that it's possible to check whether a catalyst does any work by measuring the temperature. Catalyst outlet temp is at least 40°C higher than inlet temps if there is a reaction happening. I'd be curious to check this on mine but don't have a thermometer. Because purely going by smell it can't be doing much.

Personally I'd be okay to pay for the test as long as it's within reason. My main concern would be to lose my rego because it definitely wouldn't pass the test in its current state.

I'll see if I can do a bit more digging and see what's involved in doing this nowadays.

 

On 21/03/2025 at 2:18 PM, GTSBoy said:

Just another barrier put up to stop cars being modified. When we're all driving Chinese sewing machines, you won't want to modify it anyway, and you'll likely already have slashed your wrists and be locked up in a padded room for your own protection.

To be fair I don't think it's stopping many people from doing the modifications anyway. It just puts a barrier up to doing things right  

[MBS206]

The interesting part of tests like IM240 is they measure the exhaust output.

But they never measure the gases going into the engine... Imagine doing the test in a densely populated city with higher CO2 levels around... Instant disadvantage...

[GTSBoy]

19 minutes ago, MBS206 said:

But they never measure the gases going into the engine... Imagine doing the test in a densely populated city with higher CO2 levels around... Instant disadvantage...

I remember a Wheels mag article from, I dunno when....late 80s, early 90s, or something, about a BMW engine which was claimed to be able to produce cleaner tailpipe emissions than the air it was typically breathing in on Autobahns, city streets, etc etc, in a lot of the really filthy (at the time) Euro and US cities.. All courtesy of the engine management and the plentitude of cats they had on it, of course.

Classic marketing spin, naturally, because you sure as shit can't breathe what's coming out the back. But whatever.