Smog test ahead: Will high octane gas alter smog test results?
#1
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Smog test ahead: Will high octane gas alter smog test results?
Hi All
I am going to get my car smog tested tomorrow and was wondering if any chemists out there could tell me if I should burn off all the remaining race gas ( 100 unleaded ) I have in the tank before the test ... I could also just add to the 1/4 + tank of race gas I have in the tank already ( 91 octane and lower the overall gas to like a 95 octane gas ??)
Anyone who really knows about this stuff, please chime in
Thanks in advance
Regards
Ed
I am going to get my car smog tested tomorrow and was wondering if any chemists out there could tell me if I should burn off all the remaining race gas ( 100 unleaded ) I have in the tank before the test ... I could also just add to the 1/4 + tank of race gas I have in the tank already ( 91 octane and lower the overall gas to like a 95 octane gas ??)
Anyone who really knows about this stuff, please chime in
Thanks in advance
Regards
Ed
#2
Burning Brakes
I'm no chemist but I was always under the impression that race gas atomizes better and burns more completely. No idea how that affects NOx though, NOx will increase as combustion temps go up. I think your best bet is to find a place that will do a pre-test so you can see the results without having to commit to a full test. If the results are bad just burn off the rest of the 100 oct, fill with 91 and re-test.
#3
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Thread Starter
I'm no chemist but I was always under the impression that race gas atomizes better and burns more completely. No idea how that affects NOx though, NOx will increase as combustion temps go up. I think your best bet is to find a place that will do a pre-test so you can see the results without having to commit to a full test. If the results are bad just burn off the rest of the 100 oct, fill with 91 and re-test.
I think I will just burn off the few gallons I have in the tank and fill up with Premium ... I actually thought I would be better off with the, street legal, bought at the pump, higher octane, here in the Peoples Republic of CA ...
Its not worth taking chances
regards
Ed
#4
Burning Brakes
Race gas equals Lower nox and a cooler burn. It will help a lot if the car is still in fuel control and there are no exhaust leaks before the cat. Unleaded of course-
#5
I was always under the impression that higher octane fuel if not required by the engine at idle would result in higher unburnt hydrocarbons. Is your cat in place? If so that would help burn those off at the expense of higher temps in the cat I suspect.
#6
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The system is in closed loop and the numbers were excellent in all areas except for NO
15mph max 570 mine was 725
25mph max 730 mine was 900
QUOTE=nofalls;10143858]I was always under the impression that higher octane fuel if not required by the engine at idle would result in higher unburnt hydrocarbons. Is your cat in place? If so that would help burn those off at the expense of higher temps in the cat I suspect.[/QUOTE]
Yep there is a cat on and its pretty new ( thanks to a friend )
Some say the race fuel shouldn't make a difference
WTF knows ... certainly not me
I am going to add some e85 to the mix and see what happens, Oh and also do a lot of praying
Last edited by Crazy Eddie; 01-14-2013 at 10:56 PM.
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#8
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Thanks
Ed
#9
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I'm not surprised that you didn't pass. I think any more in our area you have to have a pretty fresh cat to make the NOx numbers.
I know you aren't a fan of Reitmeier's, but they did get my 951 to pass.
Try turning on the AC (so both cooling fans come on) and close the hood as much as you can to channel the air. You want the cat hot and the engine as cool as possible.
I know you aren't a fan of Reitmeier's, but they did get my 951 to pass.
Try turning on the AC (so both cooling fans come on) and close the hood as much as you can to channel the air. You want the cat hot and the engine as cool as possible.
#10
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Thread Starter
I'm not surprised that you didn't pass. I think any more in our area you have to have a pretty fresh cat to make the NOx numbers.
I know you aren't a fan of Reitmeier's, but they did get my 951 to pass.
Try turning on the AC (so both cooling fans come on) and close the hood as much as you can to channel the air. You want the cat hot and the engine as cool as possible.
I know you aren't a fan of Reitmeier's, but they did get my 951 to pass.
Try turning on the AC (so both cooling fans come on) and close the hood as much as you can to channel the air. You want the cat hot and the engine as cool as possible.
I borrowed it from a great guy, who we all know ...
That's why I am so surprised or maybe pissed is a better word )
All the numbers were off the charts great except for the NO
The last time I passed, I was very close with the HC (very close) but all else was fine... and that was only a 16 months ago! but that was a stock cat that was 23 yrs old ....
Man I hate this ****.....
I like Jeff, its the shop I had issues with....
#11
Burning Brakes
Are you running a chip? I've seen most chips for these cars will have more timing added in the part-throttle cruise areas. Higher timing will raise NOx. They used to work fine when the smog test was just a sniffer in the tailpipe, but now that smog tests are done on a dyno under load more cars are failing. It also doesn't help that we don't have EGR on our cars.
From what I've read E85 tends to raise NOx, although this test is nearly equivocal. http://www4.ncsu.edu/~frey/conf_pr/Zhai_et_al_2007a.pdf
From what I've read E85 tends to raise NOx, although this test is nearly equivocal. http://www4.ncsu.edu/~frey/conf_pr/Zhai_et_al_2007a.pdf
#12
Rennlist Member
Thread Starter
Are you running a chip? I've seen most chips for these cars will have more timing added in the part-throttle cruise areas. Higher timing will raise NOx. They used to work fine when the smog test was just a sniffer in the tailpipe, but now that smog tests are done on a dyno under load more cars are failing. It also doesn't help that we don't have EGR on our cars.
From what I've read E85 tends to raise NOx, although this test is nearly equivocal. http://www4.ncsu.edu/~frey/conf_pr/Zhai_et_al_2007a.pdf
From what I've read E85 tends to raise NOx, although this test is nearly equivocal. http://www4.ncsu.edu/~frey/conf_pr/Zhai_et_al_2007a.pdf
Not this time
#14
RL Community Team
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Higher combustion temp = higher NO, so maybe you shouldn't heat up the engine like you did. Just drive it normal and bring it up to normal running temp. The whole mantra of getting the car hot before the smog test is because older cats don't work well when cold, but if you have a new cat, it will work pretty well cold, and at normal operating temp it should be working perfectly.
Is your new cat an aftermarket one? If so, is it a CA type? The non-CA types don't contain the catalyst for NO (or so I'm told), which is one reason why they're cheaper.
Is your new cat an aftermarket one? If so, is it a CA type? The non-CA types don't contain the catalyst for NO (or so I'm told), which is one reason why they're cheaper.
#15
Rennlist Member
Thread Starter
Higher combustion temp = higher NO, so maybe you shouldn't heat up the engine like you did. Just drive it normal and bring it up to normal running temp. The whole mantra of getting the car hot before the smog test is because older cats don't work well when cold, but if you have a new cat, it will work pretty well cold, and at normal operating temp it should be working perfectly.
Is your new cat an aftermarket one? If so, is it a CA type? The non-CA types don't contain the catalyst for NO (or so I'm told), which is one reason why they're cheaper.
Is your new cat an aftermarket one? If so, is it a CA type? The non-CA types don't contain the catalyst for NO (or so I'm told), which is one reason why they're cheaper.
I was thinking I heated up the cat enough, but some others say, maybe not ... As ya know its been pretty cold here the last few weeks so I don't know if the car is heating up the same....
I think that some e85 should help bring down the temps ,,, no?
regards
Ed