Cam, cats, tuning, and stink. Need opinions
03-06-2015, 11:06 AM
#1
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Cam, cats, tuning, and stink. Need opinions Alright guys.
I have a 227/234 113+2 cam
Ive had it about a year and the stink with longtubes was driving me insane. I almost just sold the car because of it. So I put cats on. Unfortunately, because of my borla headers, I was very limited on where I could put the cats so they are kinda far back which takes them longer to heat up. Putting cats in helped but it still stinks. My cam only has 4 degrees of overlap so its not that big.
So why the hell does it still stink so bad? I have a wideband in my car and my AFR's are always right around 14.7
Is there anything in the tune that could be adjusted to correct this?
Im at my wits end. Ive been wanting to go with a bigger cam but not if its going to get even worse.
I have a 227/234 113+2 cam
Ive had it about a year and the stink with longtubes was driving me insane. I almost just sold the car because of it. So I put cats on. Unfortunately, because of my borla headers, I was very limited on where I could put the cats so they are kinda far back which takes them longer to heat up. Putting cats in helped but it still stinks. My cam only has 4 degrees of overlap so its not that big.
So why the hell does it still stink so bad? I have a wideband in my car and my AFR's are always right around 14.7
Is there anything in the tune that could be adjusted to correct this?
Im at my wits end. Ive been wanting to go with a bigger cam but not if its going to get even worse.
03-06-2015, 11:18 AM
#2
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Are you saying the stink is "rich fuel" smell?
I run a cam with 10* overlap, an idle A/F (open loop) around 13.5 and don't have any rich fuel smell.
The Wideband only reads one bank; the other bank might be running pig rich due to a bad injector.
Do you have HPT or other scanner to read the stock O2 sensors?
If you are running near 14.7, the stock O2 sensor should both be oscillating around .5 volts.
(Personally I now run two wideband sensors, one in each bank, and it has already helped me diagnose problems. I realize that is overkill for most people.)
I run a cam with 10* overlap, an idle A/F (open loop) around 13.5 and don't have any rich fuel smell.
The Wideband only reads one bank; the other bank might be running pig rich due to a bad injector.
Do you have HPT or other scanner to read the stock O2 sensors?
If you are running near 14.7, the stock O2 sensor should both be oscillating around .5 volts.
(Personally I now run two wideband sensors, one in each bank, and it has already helped me diagnose problems. I realize that is overkill for most people.)
03-06-2015, 11:38 AM
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Yes Fuel smell. Putting in the cats helped take the edge off but still every time I come to a traffic light I can smell it. I also installed brand new o2's about two weeks ago just in case and I also can monitor the o2's with the torque app and both of them oscilate quickly and seem to be functioning the way they should. The cam I was going to go with also has 10 degrees of overlap but Im scared to go bigger now if its just going to get worse. I know that my tuner changed the injector timing a little but Do you move injector timing forward or back? and how much?
03-06-2015, 01:01 PM
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Good that you thought to check both O2 sensors.
Injector timing is super complex; few tuners will touch it. Here is hours of reading on the subject:
http://www.hptuners.com/forum/showth...ereencing-what
I don't know if really bad injector timing could give you fuel smell, but I would go back to stock values and see if that helps.
Injector timing is super complex; few tuners will touch it. Here is hours of reading on the subject:
http://www.hptuners.com/forum/showth...ereencing-what
I don't know if really bad injector timing could give you fuel smell, but I would go back to stock values and see if that helps.
03-06-2015, 01:22 PM
#6
I've found that these 3 things in the tune have helped tremendously with the fuel smell of a cammed car:
upping the idle speed
lowering idle timing
delaying end of injector timing
The link that mrvedit posted is a good one for the last part, but the other 2 also helped. Not much you can do beyond that besides changing up the exhaust to a more efficient set of cats. I was able to just about eliminate the smell with my 2.5* of overlap, so you should be able to also with those tips.
upping the idle speed
lowering idle timing
delaying end of injector timing
The link that mrvedit posted is a good one for the last part, but the other 2 also helped. Not much you can do beyond that besides changing up the exhaust to a more efficient set of cats. I was able to just about eliminate the smell with my 2.5* of overlap, so you should be able to also with those tips.
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03-06-2015, 05:21 PM
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they are kinda far back unfortunately.
I don't have that great of pictures but ill try and explain.
I have borla longtubes that only come in an offroad option and its 2 3/4 size pipe so its an uncommon size. The Xpipe is right after the collectors so my only choice was to get rid of the Xpipe completely or put it after the X
I don't have that great of pictures but ill try and explain.
I have borla longtubes that only come in an offroad option and its 2 3/4 size pipe so its an uncommon size. The Xpipe is right after the collectors so my only choice was to get rid of the Xpipe completely or put it after the X
03-06-2015, 05:55 PM
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When I talked to an exhaust shop, they said that I shouldn't have to worry about them getting plugged but that it would just take longer to light.
Maybe I should run it hard and get them really hot and see how the idle smell is after that. Maybe during the summer they will be better.
03-06-2015, 07:16 PM
#13
I have tuned vettes with cats there and that looked really similar to those. The couple I saw off the car you could look right through them, they pretty much are for passing visual inspection. None of them functioned good enough to make the pcm happy and think it had working cats.
03-06-2015, 08:37 PM
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I learned this one semi recently, this made the most difference for me. My car has less smell and the smell it has is more like an old carbed muscle car smell. Also idle is way more stable when turning the steering wheel, turning on AC etc. The idle underspeed table can actually do its job!
Any exhaust leaks will obviously make it smell worse.
Any exhaust leaks will obviously make it smell worse.
03-07-2015, 08:35 AM
#15
I learned this one semi recently, this made the most difference for me. My car has less smell and the smell it has is more like an old carbed muscle car smell. Also idle is way more stable when turning the steering wheel, turning on AC etc. The idle underspeed table can actually do its job!
Any exhaust leaks will obviously make it smell worse.
Any exhaust leaks will obviously make it smell worse.
03-09-2015, 01:57 PM
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I have tuned vettes with cats there and that looked really similar to those. The couple I saw off the car you could look right through them, they pretty much are for passing visual inspection. None of them functioned good enough to make the pcm happy and think it had working cats.