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Old 01-11-2001, 03:12 AM   #1
ivbdn
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Post I went from 92 Octane to 87 and...

I smell rotten eggs every now and then. I've got an intake and exhaust.

I used to run 92 since I got the car. But then I learned that it might actually be affecting the car negatively, so I switched...and when I did...the car started to stink. Any help/suggestions/comments would greatly be appreciated.
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Old 01-11-2001, 06:58 AM   #2
Greg555
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ok
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Old 01-11-2001, 08:20 AM   #3
rjones
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The same thing ahppened to me. BUT I thought it had to do with the start of the winter here in the northeast. They put a wierd additive in gas here during the winter to cut emissions (can someone remind me what this is and how it works?)

But you are in LA so maybe it really is the octane switch and not the winter additives.
*shrug* My seems to stink less now. Maybe the cats have to get used to the new octane.
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Old 01-11-2001, 08:39 AM   #4
Kevin Thomas
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Lightbulb

Try resetting your ECU and see what happens. Your ECU has to get used to the new octane *Advancing timing and other tidbits*.

Maybe you passed gas because your car is performing worse (Shi* yourself). J/K

[This message has been edited by Kevin Thomas (edited January 11, 2001).]
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Old 01-11-2001, 08:59 AM   #5
UCmego
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How would it affect the car negatively? I just got my MY01 RS and I am only running 92 in it. When people of other makes of cars go to the dragstrip, they usually buy race gas to make the car perform even better...so how could 92 hurt the car. I don't think that is correct information.
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Old 01-11-2001, 09:03 AM   #6
Damon
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i agree. there is no possible way that a higher octaine gas is hurting your performance. higher octaine gas burns better, and has a higher temp for combustion, therefore it would make the car run better.
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Old 01-11-2001, 09:10 AM   #7
donjuan
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ivbdn--I'm just speaking from experience with other cars in the past, but the rotten-egg smell is usually a dead cat. (catalyst, not roadkill)
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Old 01-11-2001, 09:22 AM   #8
motorob
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It's a sulphur byproduct that occurs in the cat with certain formulations and brands of gasoline. Saab had a Service Bulletin on it a year or two ago. It has to do with how efficient modern catalysts are, and with gasolines reformulated for cleaner air. I don't know if Subaru has any service info on the problem. But it can REALLY stink, I've smelled a couple of Saab 9000's and 9-5's with the problem. It's harmless though..

Oh, and this is an old topic on this board (and in other places), but the consensus on the part of non-boy racers and engineers (and the manufacturers) is that all the octane you need is enough to inhibit ping. Anymore is a waste of your money (sound of gas companies laughing all the way to the bank....)

[This message has been edited by motorob (edited January 11, 2001).]
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Old 01-11-2001, 10:20 AM   #9
roninscar
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There was something else I read a while ago, which indicated that your performance would decrease ever so slightly with 92-93 octane premium over 87 octane. Had to do with the increased volatility of the lower octane gas. That being said, I still feel that premium (like Amoco, I like being able to see it in the pump handle with the little balls swirling around) is a cleaner gas, if that makes any sense. I think I saw this somewhere on the SE-R net, back in my nx2000 days.

And you do not want to run 104 octane race gas in your regular car, that is only for really nasty, high compression or high boost applications.
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Old 01-11-2001, 02:04 PM   #10
SnapperHead
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The reason why running higher octane gas in your stock RS isn't a good idea is because at higher octanes your engine needs to spark hotter in order to ignite the gas. More power allows you to ignite the higher octanes. If you are running a stock RS, running 92 octane would be degrading to your performance because you would not be able to ignite it properly. Thats why at higher HP's you need to run higher octane, the higher resistance to igniting.
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Old 01-11-2001, 03:35 PM   #11
Saw Jai
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what Snapper head said...plus I think it'll lower ur mpg...cuz ur engine isn't burning all the fuel that its getting...so the unburnt gas goes to waste...
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Old 01-11-2001, 04:22 PM   #12
Die Civic
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I must agree with Saw Jai, even though his sn means "Naive Boy" :P Saw Jai, Lay ho chun wah?
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Old 01-11-2001, 10:46 PM   #13
Patrick Olsen
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Read these threads: http://www.i-club.com/ubb-files/Foru...ML/003082.html and http://www.i-club.com/ubb-files/Foru...ML/002434.html . That second degenerates a bit into cam specs, but there is some good info about octane, compression ratios, power output, etc in each of those threads.

UCmego - As roninscar pointed out, the 104+ octane race gas is used by guys at the strip because they're setting their cars up for max power. So, they've probably jacked the timing up (something we can't do on our distributorless Subarus), and there's a good chance they're running high compression with aggressive cams.

Damon - Higher octane gas burns better based on what? Yes, higher octane gas is more resistant to pre-ignition (aka detonation, aka pinging), but that has nothing to do with how it actually burns. And I could be wrong, but I also don't think that the increased resistance to detonation means that higher octane gas burns at a higher temp. If there is a difference, I'm sure it's minimal, and would not result in any appreciable difference in how the car ran.

SnapperHead - It's late, and I need to go to bed, so I'll try to remember to come back to this tomorrow. Basically, I think your logic is kinda backwards (or maybe I'm just misunderstanding you - after all, it is late, and I need to go to bed ).

Pat Olsen
'97 Legacy 2.5GT sedan
Running on cheap 87 octane and luvin' it!
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Old 01-11-2001, 10:57 PM   #14
spt_impreza
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you should ONLY run the octane level its says in the owners manual.......unless you have knock or detionation. it will hurt the engine

spt
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Old 01-11-2001, 11:13 PM   #15
cj917
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basically was Pat said

higher octane gas needs hotter spark to burn as completely as it would take lower octane gas with stock spark... the spark will still ignite fine, just the gasoline won't burn as efficiently

so unless you are running much higher compression ratio, advance your timing by a lot, turbocharging/supercharging, or whatever means to increase power output that you need to worry about detonation, you do not need to run higher octane gas than what the manufacturer suggests

that said, i don't think running 92-octane would decrease performance enough to be able to be felt by butt-dyno... but like what Saw Jai said, your mpg is likely to go down noticeably compare to running 87-octane

however, i don't know whether the unburned gas somehow stay in the cylinders and eventually clog them up to a point that'll decrease performance, or does it get pushed out into the exhaust? if the former is true, then i can see running higher octane than necessary have a long-term effect
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Old 01-12-2001, 08:21 AM   #16
Gambit
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If anything higher octane actually burns less efficient as lower octane if your car is tuned for low octane gas.
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Old 01-12-2001, 10:13 AM   #17
Bruce Feinberg
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The octane rating of the gas actually indicates the anti-knock characteristics of the gas. The higher the octane rating, the lower the volitility of the gas. Higher octane gas actually burns slower and cooler, lower the occurance of pre ignition. Higher octane is needed in cases of cars with a high compression ratio, or cars tuned with timing more advanced than originally designed. Basically, if your not experiencing pre ignition, using higher octane fuel will give no benefit(it's like wearing bigger sneakers in order to run faster). Personally, I recommend Chevron gas because of the Techron additive they use(sounds like a commercial-but I've actually seen clear results showing this stuff really cleans out carbon from valves/injectors/combustion chambers). I've had service customers declare their cars magically rejuvenated by just switching to Chevron.
Good Luck-Bruce(Subaru of Santa Cruz)
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Old 01-12-2001, 10:22 PM   #18
subywuby
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Question

I was reading the new issue of Subaru Drive magazine yesterday and the article on the new H-6 says "like all other Subaru vehicles, this engine runs on regular fuel, but 91 AKI premium gasoline is recommended for maximum performance." They don't mean that all suby's will run better on premium do they? Assume they are saying this new H-6 can benefit from 91 AKI.

subywubynwby
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Old 01-13-2001, 12:06 AM   #19
STiShawn
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I usually run 92 octane only, never had issues with it. It does help to cool the piston and combustion chamber. I also can tell a difference the few times I have gone down, or up on the octane scale. I can buy 95 octane gas over Illinois, what kick that is.
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Old 01-13-2001, 11:43 AM   #20
meebs
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Hmmm, I wonder if running premium is why i get that little pop between shifts?

Subaru Drive Magazine? Where can i get a subscription to that?

-meebs
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Old 01-13-2001, 01:57 PM   #21
Skirvdawg
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So someone else has that rotten eggs smell here in the north east? When I first moved here to Newport about 2 mos. ago, I noticed a sort of rotten eggs smell; I just assumed it had to do with the route I was driving. I didn't know they added stuff to the gas.

As far as the octane thing goes, Subaru recommends it, and I'm willing to lose .05 Hp for the cost savings over 91 octane.
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Old 01-14-2001, 12:48 AM   #22
JZ oo7
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subaru drive? where do i get that at?

jansen
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Old 01-14-2001, 01:44 AM   #23
Kcz
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meebs, that is exactly why you get that "little pop" the fuel is igniting late. I started to use the mid-grade(89) and it works perfect. No more poping here.
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Old 01-14-2001, 07:07 AM   #24
Bassem
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man, hasn't this topic been beaten to death?

the facts are as follows:
-higher octane contians more additives/unit volume than lower octain. this means that per unit volume, you have less combustible molecules in higher octane gas. this is why your mileage gets worse, because the car needs to use more volume of fuel for every ignition at higher octane to get the same power than from lower octane

-running higher octane gas doesn't hurt your engine, unless the liners are sensitive to the anti-knock additives. depending on the ecu, you can get more power. by that i mean some intelligent ecus will advance timing to take advantage of the higher octane rating and hence make more power. as far as ignition, the mixture will still ignite whenever the spark comes along, so don't even think its an issue.

-some may argue that the additives in higher octane gas will clog or burn poorly. fact is most additives are quite volatile at the ignition temperature, so they will clear the combustion chamber and not leave deposits or clog anything.

-the egg smell is from fuel being burnt in the cat and not in the combustion chamber. specifically the cat right at the exit of the exhaust header, which is right in front of the firewall, and hence its smell can easily carry into the cockpit. the smell means you are running rich. the only way your car can do that is by having ecu meter too much fuel. which means that it has not redjusted to the new fuel yet. unless you reset the ecu, this may take a longer time.

-in genral lower octane gas contains more sulfur. even sunoco advertises this as a reason to buy thier high octane stuff. increase in sulfur content will increase the smell of the rotten eggs.

so, just reset the ecu and see what happens. this will help if the car is running rich. if it still persists, try another gas station. hopefully their gas will be cleaner.

just as an fyi, i ran 89 octane when the car was stock, then switched over to 93/94 right before the turbo install. i also use half a gallon of octane 108 octane booster with every tank.

good luck
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Old 01-15-2001, 02:30 AM   #25
ivbdn
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Thanks to everyone for their advice/comments. Sorry to bring up an old topic.
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