This toggle is not magic, you will not pass a true emissions test with catless downpipes with or without it. That person was a fluke and somehow got lucky (if true). As I stated above, this function is actually intended to improve catalyst efficiency (when used with OEM downpipe)
Readiness - Catalyst
- Thread starter carabuser
- Start date
UK and some EU emissions tests are based on tailpipe emissions and don't consider monitors at all. My own cars both pass the local testing requirements here just by using the secondary cats alone.
The reason I noticed the oscillating afr was because of this testing. I was trying to tweak the tune to run leaner and give me a better chance of passing the CO2 limits and I noticed the target lambda from the DME was all over. The idea of the oscillation is that it should average out between both banks but I believe the overall effect is an increase in both unburned fuel and an increase in NOx so fixing this should help genuinely reduce emissions.
It definitely runs on the richer side on idle oscillates between 13.9 to 15.1 confirmed by quite a few users...
When your car is back on the road just send the bin over and I'll apply the same changes I made to my INA0S cars to stop it. I might give you 3 different bin files each with a different fix to see which one fixes it exactly in your circumstance.
Before this becomes a fix that Jake can add into MHD it needs plenty of people testing it.
Raising the min cat temperature requirement (c_temp_cat_min_lam_adj_act) helped out my fluctuations on my MSD80 whenever I target 1 lambda at idle.
For anyone that runs higher than 1 lambda at idle, raising the cat temperature req is not necessary as you'll be operating (idling) above the max lambda requirement anyway.
I did 3 tests
Test 1:
Target AFR: 16
Fluctuation of 15.9-16
1% dips to 15.8
Test 2: By far largest delta in fuel
Target AFR: 14.671
Fluctuation of 14.2-14.8
1% dips to 13.8
Test 3: c_temp_cat_min_lam_adj_act adjusted and nothing else
Target AFR: 14.671
Fluctuation of 14.4-14.7
1% peaks of 14.8
My "smoothest" idle was achieved by targeting an AFR of 16.0
For anyone that runs higher than 1 lambda at idle, raising the cat temperature req is not necessary as you'll be operating (idling) above the max lambda requirement anyway.
I did 3 tests
Test 1:
Target AFR: 16
Fluctuation of 15.9-16
1% dips to 15.8
Test 2: By far largest delta in fuel
Target AFR: 14.671
Fluctuation of 14.2-14.8
1% dips to 13.8
Test 3: c_temp_cat_min_lam_adj_act adjusted and nothing else
Target AFR: 14.671
Fluctuation of 14.4-14.7
1% peaks of 14.8
My "smoothest" idle was achieved by targeting an AFR of 16.0
@KClemente Nice, I didn't think about raising my AFR so much because my first intent was to smoothen my AFR for my failed emission test (high CO) and at the tailpipe test a lambda higher than 1.03 (AFR 15.14) is a fail.
I also thought that this 13.8-15 oscillation function took over AFR target values, so in my head we had to fix the idle/low load oscillation prior touching AFR tables, it seems it's not the case according to your tests.
Here my two logs for comparaison (stock AFR target 14.67) :
BEFORE
AFTER
Night and day, even if a bit of oscillation is inevitable I think.
Otherwide and if it could help other people, my tailpipe sniffer emissions passed successfully yesterday, I think it's a combinaison of three things :
- Oscillation fix (those pulsating dips in the 13.8 aren't good for CO emissions)
- low load AFR to 14.900 (equals to a lambda value between 1.01 & 1.02, I wanted to be borderline of the limit of 1.03 to reduce CO)
- E30 blend (to reduce CO too)
I also thought that this 13.8-15 oscillation function took over AFR target values, so in my head we had to fix the idle/low load oscillation prior touching AFR tables, it seems it's not the case according to your tests.
Here my two logs for comparaison (stock AFR target 14.67) :
BEFORE
AFTER
Night and day, even if a bit of oscillation is inevitable I think.
Otherwide and if it could help other people, my tailpipe sniffer emissions passed successfully yesterday, I think it's a combinaison of three things :
- Oscillation fix (those pulsating dips in the 13.8 aren't good for CO emissions)
- low load AFR to 14.900 (equals to a lambda value between 1.01 & 1.02, I wanted to be borderline of the limit of 1.03 to reduce CO)
- E30 blend (to reduce CO too)
Tested out C_TEMP_CAT_MIN_LAM_ADJ_ACT to 1772
Stock AFR targets 14.671 in map
Cruise log: Fluctuations are better for sure. I'm not seeing the crazy 13.7-15.1. But should they be better?
https://www.spoolstreet.com/graphs/cruise.14896/?series=13,14,18,21&zoom=-6,645
Idle log: Pretty solid AFR's happy with that!
https://www.spoolstreet.com/graphs/idle.14897/?series=2,13,14,18&zoom=-4,356
Also this a EU version map so no like DTML like US could be worthing mentioning.
Stock AFR targets 14.671 in map
Cruise log: Fluctuations are better for sure. I'm not seeing the crazy 13.7-15.1. But should they be better?
https://www.spoolstreet.com/graphs/cruise.14896/?series=13,14,18,21&zoom=-6,645
Idle log: Pretty solid AFR's happy with that!
https://www.spoolstreet.com/graphs/idle.14897/?series=2,13,14,18&zoom=-4,356
Also this a EU version map so no like DTML like US could be worthing mentioning.
If a toggle to stop idle oscillations might be added to MHD in the future, might I suggest that toggles for other catalyst routines (cat purge, cat monitoring, stimulation, etc) be available as options as well, or all-in-one? I'll always disable these things via tuning personally, but for those using OTS maps or those who hire a tuner.
On a different note, I have notice pretty bad idle fuel consumption. I live in a hot climate, and during Covid I had to sit in my dog's vet parking lot during her visit for an hour. I kept the car running with AC on. The fuel it consumed idling during that hour was higher than I've ever seen in any other car. And sure enough oscillations were happening that whole time. So I believe these routines are definitely having an effect.
I have missed that smooth stable idle since I went catless.
It amazes me how majority of people do not notice the idle smoothness degradation on catless or maybe I pay too much attention to the details!
I have also noticed a bit more soot build up in the exhaust, dps and on O2s tips that might relate to that extra unburned fuel from the toggles...
Yeah that's to be expected from being catless. Everything's perfect for me now after this. Only thing I get now is a single stumble at idle once in a while. Doesn't change anything really but it annoys me regardless! Will eventually replace O2s, sparks, and purge valve as scheduled maintenance soon anyway, we'll see if that fixes it.
I did have few stumbles on cold start on ngk plugs, switched to bosch n55 plugs and its sorted...
Hmm I like the NGKs but I think I might have them gapped too small. I've heard the recommended gaps for tuned are just a little bit conservative and can be a little larger. May try that first.
Not starting a new thread since this question is related to subject.
Does anyone have the info on what was the maximum load (in the load table) where cat readiness can still come on. I remember someone on some forum specifying this but did not find it anymore.
Also great info on the catless rpm fluctuation. I ordered area74 cat sims to see if that cures the issue without other changes. What I noticed when troubleshooted this earlier on my own that the fluctuation goes away at least for a while if every lambda adaptation is reset with inpa.
Does anyone have the info on what was the maximum load (in the load table) where cat readiness can still come on. I remember someone on some forum specifying this but did not find it anymore.
Also great info on the catless rpm fluctuation. I ordered area74 cat sims to see if that cures the issue without other changes. What I noticed when troubleshooted this earlier on my own that the fluctuation goes away at least for a while if every lambda adaptation is reset with inpa.
There's a few tables you could use but this sounds like what you're after:
IP_MAF_MAX_CAT
"max. MAF threshold for catalyst diagnosis activation"
Any chance of MHD implementing this change in the flasher?
I am happy to participate in any testing as I run OTS maps unlike most people here which run custom tunes.
Implement what? We're still trying to work out exactly what the magic bullet is for inhibiting this behaviour.
I've figured out a way to patch the diagnostics out completely for my own vehicles but it can't be done via MHD as it probably falls foul of emissions regs. So if people want a method MHD can implement then they need to get involved and test the tables mentioned in this thread.
Hello
What would be the location where to find this in I8A0S and what is the default value? Anyone tested this?
Patch the diagnostics in such a way that they will not interfere with normal operation or in a way you would get the readiness bits set?
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