991.2 Carrera Cobb Tuning issue
02-03-2019, 05:01 PM
#61
Hmmm..... what kind of fuel do you use? Two ways I can think of to kill cats: contaminated fuel(lead), or too much heat. If you were just doing street driving, I would find it hard to believe it was heat. A quick pull here and there shouldn't really got too toasty. Sustained full throttle on a road course could kill a cat quickly if the EGTs are too high.
very strange indeed. No leaded fuel. Always use 93 oct Mobil every time. Car has never been on the track. I’m not sure what could cause this. Maybe a bad load of fuel?
02-03-2019, 06:43 PM
#62
http://www.bobsmuffler.com/reasons_f...er_failure.htm
I looked at the datalogs you posted and it's certainly not too much fuel (dumping fuel into the exhaust) as your A/F was definitely close to stoich. That could pose a 'too much heat' problem from being relatively lean if you spending a lot of continuous time at full throttle such as on a road course. But a pull here and there, even a quarter mile, I don't think is long enough to create sufficient heat to damage the cat. So..... maybe too much oil? I've seen a couple pictures of the turbo inlets on the 991.2s with lots of oil in them. So maybe sucking in too much oil through the turbos and it's going out the exhaust and clogging the cat? Vektor Performance is working on an air-oil separator to address the issue of oil getting sucked into the turbos through the PVC system. But anyway, that's just a hypothesis on a potential cause. If you can get some detailed pictures of the stock cats, it may help identify the failure mode.
02-03-2019, 07:00 PM
#63
Rennlist Member
Are those logs WOT?
I see it going rich up top. Cats causing a restriction makes sense; impeded combustion as the back pressure builds up.
Glad to hear this is worked out! Might go visit AMS now and get mine done as well. Perfect excuse for bypasses lol.
I see it going rich up top. Cats causing a restriction makes sense; impeded combustion as the back pressure builds up.
Glad to hear this is worked out! Might go visit AMS now and get mine done as well. Perfect excuse for bypasses lol.
02-03-2019, 07:56 PM
#64
Log 1 goes rich, with A/F dropping to around 13.3 which does look normal for this car. Stock tune I take it. Log 3 has a lot of part throttle with one a short segment of WOT from the looks of it. Assuming 81% pedal position is WOT.
02-04-2019, 01:20 AM
#65
Thank you for the info on catalytic converters, good read!
log 1 is stage 1 93 oct and log 2 is stage 0 both at WOT
I believe I posted a few photos of all the oil inside the passenger side turbo housing so it could have definitely been an oil clogged cat.
heres a few photos of the cats...
log 1 is stage 1 93 oct and log 2 is stage 0 both at WOT
I believe I posted a few photos of all the oil inside the passenger side turbo housing so it could have definitely been an oil clogged cat.
heres a few photos of the cats...
02-04-2019, 10:53 AM
#67
Rennlist Member
Log 1 is the tune file it appears from Ryan's comments. The I'm seeing the AFRs go rich gradually and then level off as the engine speed rises. Makes sense; cats are nearing their max flow. That's increasing the back pressure in exhaust, not allowing for complete expulsion of the gasses. Not ideal combustion scenario, so the "sand bagging" effect is expected.
From my experience with turbo cars, Cats always end up being bottle necks. Sports cats help, but still will cause some impeding of flow as you increase the amount of fuel and air being burnt. If you're looking to take advantage of a tune, catless is the way to go. No restriction, free flow.
02-04-2019, 10:55 AM
#68
Three Wheelin'
Catless= Noisy, Smelly, Wont pass Emissions. Also will throw a check engine light without O2 sensors and/or tune to override error.
At some point you have to make concessions on a car that is driven and not raced on a track.
Some people are OK with cat bypass pipes but, the gains aren't worth the trade off to me.
At some point you have to make concessions on a car that is driven and not raced on a track.
Some people are OK with cat bypass pipes but, the gains aren't worth the trade off to me.
02-04-2019, 10:56 AM
#69
Rennlist Member
The cells look alright.
Honestly, I remember a similar situation with my BMW a couple years ago. I was running catless downpipe and stage 2 tune, but needed to pass emissions for registration. I swapped back my stock, catted down pipe to get the emissions system ready for testing. While I had it in, I did some pulls and logs and found the power to be dramatically reduced up top in the rev-range. Lasted about a week before I put the downpipe back in.
Good times...good times...
Honestly, I remember a similar situation with my BMW a couple years ago. I was running catless downpipe and stage 2 tune, but needed to pass emissions for registration. I swapped back my stock, catted down pipe to get the emissions system ready for testing. While I had it in, I did some pulls and logs and found the power to be dramatically reduced up top in the rev-range. Lasted about a week before I put the downpipe back in.
Good times...good times...
02-04-2019, 10:57 AM
#70
Rennlist Member
Actually wait. I have a video of me in Mexico with one of my friends. We had the same setup except I was catted and he was catless. Let me see if I can pull the link.
02-04-2019, 11:08 AM
#71
Rennlist Member
Camera car is catted. Right lane is catless. We are both Stage 2 tune and same cars.
02-04-2019, 01:16 PM
#73
Rennlist Member
400, 400X, 400A, and 400 AX for left
450, 450X, 450A, and 450AX for right
This is on the US spec cars. I'm assuming these CATs correspond to the trims and then PSE or non PSE. My guess would be the 4** and 4**X is for T, C, CS cars. The 4**A and 4**AX for the GTS versions.
02-04-2019, 01:54 PM
#74
Idk about that. Looking at the part numbers for the CATs, there appear to be 3 types of CATs.
400, 400X, 400A, and 400 AX for left
450, 450X, 450A, and 450AX for right
This is on the US spec cars. I'm assuming these CATs correspond to the trims and then PSE or non PSE. My guess would be the 4** and 4**X is for T, C, CS cars. The 4**A and 4**AX for the GTS versions.
400, 400X, 400A, and 400 AX for left
450, 450X, 450A, and 450AX for right
This is on the US spec cars. I'm assuming these CATs correspond to the trims and then PSE or non PSE. My guess would be the 4** and 4**X is for T, C, CS cars. The 4**A and 4**AX for the GTS versions.
02-04-2019, 02:05 PM
#75
Rennlist Member
Just base (aka non-PSE) and PSE. That's the 2 types of constructions (PSE has the valve and the extra plumbing).
The Fabspeed and Soul Cats work with C/T/S/GTS; the type depends on the exhaust installed (Non-pse or PSE).
Going off the part numbers; there's 4 types of CATs. I'd assume that the overall structure is the same, but I'm expecting the internal cell structure of the catalyst differs between the trim/power levels.