Crazy Eddie

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

Dave W.

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.

Crazy Eddie

Thanks for your input
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

kev951

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-

nofalls

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.

Crazy Eddie

Yes Well I was a bit concerned about the unleaded race gas so I added about 50 -60% premium and sadly I still failed ..
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

968 GUY

It's best to have the engine and especially the exhaust fully up to temp before going for the test. Driving 10 or so minutes to the facility just wont do it.

Crazy Eddie

I drove it for over 20 -30 mins and then left it idling another 20 mins ... Its been very cold here, so maybe I need to run it on the HW longer .. will do that tomorrow along with the e85
Thanks
Ed

PEvans

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.

Crazy Eddie

Actually, this is a very new after market cat ( just like you have )
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....

Dave W.

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

Crazy Eddie

Yes, its a kit ( chip, turbo, maf, SMT6, etc but I passed with the chip etc last time but as I said it was close on the HC but it passed
Not this time

pr951

A friend recommended to hold the car at higher revs for 2-3 minutes just prior to test (ie 3500 rpm) to heat up the cats.

FRporscheman

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.

Crazy Eddie

Its a new maybe a year old (used for smogging only) after market cat that is CA CARB approved ...
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