Failed SMOG: HC too high at Idle
#1
Old School
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iTrader: (6)
Join Date: Jan 2001
Location: Union City
Posts: 14,983
Car Info: '99 RBP GM6
Failed SMOG: HC too high at Idle
Suggestions?
I have an SAFC which is not being utilized at the moment, do i need to lean out or richen the mix at idle?? how much?
Here are the stats:
RPM C02(%) 02(%) HC(PPM) C0 (%)
Meas Meas Meas max ave Meas max ave Meas
688 14.3 0.6 100 17 203 1.00 0.0 .33
2725 14.4 0.5 130 12 38 1.00 0.10 .24
FAIL
Mods:
CAI
4-1 Headers
1 Cat
Catback
-Gagan
I have an SAFC which is not being utilized at the moment, do i need to lean out or richen the mix at idle?? how much?
Here are the stats:
RPM C02(%) 02(%) HC(PPM) C0 (%)
Meas Meas Meas max ave Meas max ave Meas
688 14.3 0.6 100 17 203 1.00 0.0 .33
2725 14.4 0.5 130 12 38 1.00 0.10 .24
FAIL
Mods:
CAI
4-1 Headers
1 Cat
Catback
-Gagan
#6
Registered User
iTrader: (21)
Join Date: Nov 2002
Location: Santa Clara CA USA
Posts: 1,253
Car Info: 96 Chevy Impala SS, 06 GMC 2500HD (former 02 WRX)
Throw the second cat back in, and lean it out at idle. Normally the "trade off" is that if you lean it out the HC will go down but NOX will go up. Fortunately for you (and all other Subaru owners) is that the idle/2500 test does NOT measure NOX (the dyno roller test does measure it). ECU tweaking can work some miracles in that case
FWIW, this Saturday I smogged my Impala with the stock motor and stock cats (along with "tweaked" ECU) on the dyno rollers. Tailpipe numbers were 9 PPM on HC at both 15 MPH and 25 MPH. Last time I did idle/2500 on it with stock cats (back in 1998) it was under 10 PPM for both RPMs (I think 7 at idle and 2 at 2500?). Those GM cats are pretty good, so good in fact that a buddy of mine up in Massachusetts has failed their idle/2500 test for being TOO clean (as in, car blew so clean thru the tailpipe that the state computer just assumed things were broken with the smog machine ).
When I smogged the (stock) WRX in March before selling it, it was something like 17 PPM at idle...yeah, the "ULEV" was dirtier in PPM than my "big evil V8 musclecar"
FWIW, this Saturday I smogged my Impala with the stock motor and stock cats (along with "tweaked" ECU) on the dyno rollers. Tailpipe numbers were 9 PPM on HC at both 15 MPH and 25 MPH. Last time I did idle/2500 on it with stock cats (back in 1998) it was under 10 PPM for both RPMs (I think 7 at idle and 2 at 2500?). Those GM cats are pretty good, so good in fact that a buddy of mine up in Massachusetts has failed their idle/2500 test for being TOO clean (as in, car blew so clean thru the tailpipe that the state computer just assumed things were broken with the smog machine ).
When I smogged the (stock) WRX in March before selling it, it was something like 17 PPM at idle...yeah, the "ULEV" was dirtier in PPM than my "big evil V8 musclecar"
#7
Old School
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iTrader: (6)
Join Date: Jan 2001
Location: Union City
Posts: 14,983
Car Info: '99 RBP GM6
nope, all good there
Ok. I'm going to play with the SFAC at idle to see if i can raise the EGTs a few hundred degrees and then go test it again.
I need to drop 103 HCs, I wonder how much higher in EGT i need to go.
-Gagan
Throw the second cat back in, and lean it out at idle. Normally the "trade off" is that if you lean it out the HC will go down but NOX will go up. Fortunately for you (and all other Subaru owners) is that the idle/2500 test does NOT measure NOX (the dyno roller test does measure it). ECU tweaking can work some miracles in that case
FWIW, this Saturday I smogged my Impala with the stock motor and stock cats (along with "tweaked" ECU) on the dyno rollers. Tailpipe numbers were 9 PPM on HC at both 15 MPH and 25 MPH. Last time I did idle/2500 on it with stock cats (back in 1998) it was under 10 PPM for both RPMs (I think 7 at idle and 2 at 2500?). Those GM cats are pretty good, so good in fact that a buddy of mine up in Massachusetts has failed their idle/2500 test for being TOO clean (as in, car blew so clean thru the tailpipe that the state computer just assumed things were broken with the smog machine ).
When I smogged the (stock) WRX in March before selling it, it was something like 17 PPM at idle...yeah, the "ULEV" was dirtier in PPM than my "big evil V8 musclecar"
FWIW, this Saturday I smogged my Impala with the stock motor and stock cats (along with "tweaked" ECU) on the dyno rollers. Tailpipe numbers were 9 PPM on HC at both 15 MPH and 25 MPH. Last time I did idle/2500 on it with stock cats (back in 1998) it was under 10 PPM for both RPMs (I think 7 at idle and 2 at 2500?). Those GM cats are pretty good, so good in fact that a buddy of mine up in Massachusetts has failed their idle/2500 test for being TOO clean (as in, car blew so clean thru the tailpipe that the state computer just assumed things were broken with the smog machine ).
When I smogged the (stock) WRX in March before selling it, it was something like 17 PPM at idle...yeah, the "ULEV" was dirtier in PPM than my "big evil V8 musclecar"
I need to drop 103 HCs, I wonder how much higher in EGT i need to go.
-Gagan
#10
Old School
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at about -7% fuel at idle the car starts to stumble slightly. EGTs don't go up really or don't show going up in any significant amount.
raising the fuel to about +10% looks to make the car stumble and die.
Looks like I know what I'll be doing wednesday night
raising the fuel to about +10% looks to make the car stumble and die.
Looks like I know what I'll be doing wednesday night
#11
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Join Date: Nov 2002
Location: Santa Clara CA USA
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Car Info: 96 Chevy Impala SS, 06 GMC 2500HD (former 02 WRX)
EGT will not really change appreciably at idle, so don't use it as a judge.
HC is, simply put, incompletely burned fuel. If you're lean, HC will NOT be high but you will have NOX shoot thru the roof in a hurry.
Try leaning it out -5% at idle and go retest (assuming you have "free" retest). If that doesn't do it, then do the cat swap.
HC is, simply put, incompletely burned fuel. If you're lean, HC will NOT be high but you will have NOX shoot thru the roof in a hurry.
Try leaning it out -5% at idle and go retest (assuming you have "free" retest). If that doesn't do it, then do the cat swap.