Sc Question

dwayne

Banned
Most of the gas stations here have stoped selling 93 oct gas,we have 89 oct and 87 oct,Can you run the SC on 89 oct,Mine is factory stock,no mods,as most of you know the SC is stored with a full tank of 93 with staibful.I had hand controls put on my S10,but got the bug to bring out the SC again.Can you run 89 oct in the SC without damaging the engine.the engine only has 9,000.00 miles,not a rebuild.
 
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im not positive but i think the owners manual states at least 91+!!! I dont know what adverse effects would be on your engine
 
The SC engine has a "knock" sensor. That is that thing that sticks out of the block just above and in front of the starter. It is my understanding that with the knock sensor you can run 87 or 89 octane but performance will decrease since the knock sensor tells the PCM the level of knock and, subsequently, the PCM retards ignition timing so the engine will not suffer damage. I never have run 87 or 89 octane in the SC so maybe some else can chime in with their experiences.

ED
 
when i was real broke i ran 87 for a year with no problems. even now when i don't have money i will run 87 or 89. the only thing i have seen is performance will sufer from the pulled timeing.
 
I would not run it unless you are ready to put more money into fixing your engine.

The main problem you will have is detonation, regardless of the knock sensor. That sensor can only do so much before the spark knock gets out of hand. If you run lower than 91 blown head gaskets (or worse) can result.

Since you say you have no choice right now, just keep out of the throttle and stay off the boost.

As far as the gas stations not selling premium fuel, the owners should be burned at the stake for not selling it.;) But thats fine I guess, that just means more customers at other gas stations other places.:D
 
If you need to run less than 91 octane...pull the octane plug that is located near the EEC test port. Pulling the plug retards timing 4 degrees and that should be enough to prevent detonation.

octane.jpg


David
 
stay out of the boost and there should be no problem,

sc's have low compression but under boost its staggeringly high
 
Why not pour in a bottle of octane booster when you get gas.....:confused:

I accidently put 87 in Black Betty one time.....:eek:

Her engine rattled like it was going to fall apart.....

I gave her a bottle of octane booster and she was fine after that.....
 
Really? (Dave N.) That would be too simple, thats why I ask.:confused:

Yes....it's that simple. For even greater economy, wire the bypass valve to stay open at all times (prevents you from building any boost) and you can burn 87 octane without removing the octane plug.

David
 
Yes....it's that simple. For even greater economy, wire the bypass valve to stay open at all times (prevents you from building any boost) and you can burn 87 octane without removing the octane plug.

David
Now thats my kind of fix.. ;)

I've been running 87 octane in 2 of my 3 cars with the octane plug pulled. For daily driving, I've noticed no difference in how it runs, nor have I heard an clatter.

However, I would not recommend running anything less than 91 w/o pulling the plug. When I've run 89 w/o pulling the plug, the ping was very bad!
 
Due to high altitude I've heard that it doesn't make a big diff on the octane. Is this true? 5280 ft above sea level (Denver, CO)

I ask because when I got my first 3.8SC (the red cougar) I didn't know to put in premium and I drove everywhere on 85. I didn't hear pings or feel performance issues. In the three I've had total, 93 vs 85 doesn't seem to make a big difference, maybe it would at sea level, I dunno.
 
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Even at the track?

Well, noooo, but then I haven't raced it since put the new motor in it. I run only brand name 93 in the racer. I've raced the CTS with 89 in it and run 87 for daily driving.
 
The octane plug is a temp thing just in case you have to run less than 91. I would not recommend driving the car for long like that.

I got a parts car awhile back and the last owner didn't know any better and ran the car with 87 for about a year. You should have seen the carbon I scraped off the top of the pistons and the cumbustion chambers. I think because of our low compression ratio, 87 and 89 don't burn properly because the entire tune is geared to the slower burn rates of the higher octane fuel.

I'm going to venture to guess your going to eat up the cats and the o2 sensors pretty quick because of the fuel not being burnt properly. I guess you could get a tune done that would make the car more efficient on 87 but then I'd also run a larger pulley on the blower so you don't get so much boost.

Of course now that folks is saying its "ok" we're going to see a rash of blown motors.

Frit
 
Well now I don't think you can blame the 89 oct for the tranny failure.:D But, it's amazing how so many things can go so wrong all at the same time.
 
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