93 Octane kills engine performance?
Thread Starter
Racer
Joined: Jul 2003
Posts: 455
Likes: 0
From: Buffalo New York
93 Octane kills engine performance?
Specs: '77 L48, 882 heads, original cam, headers, dual exhaust, no smog, rebuilt Q-ject, recurve kit with silver Mr. Gasket springs, timing set to 36 at 3000 rpm's with the vaccum advance disconnected and 48 total with it connected. Timing was 14 at idle.
Problem: I set the timming with the engine running on 87 octane fuel. The car was running great although my gas milage was terrible 12-14 miles per gallon. I tried switching to 93 octane and ran into serious detonation problems. I retarded the timing so that I am now at 8 initial and and I peak out at 24 at 2800 rpms. The detonation is gone, but the performance is aweful.
I have 3/4 of a tank of gas left, I quess I should be happy that my car likes 87 better than 93, but Help!!! I want to get the best possible performance 87 or 93...
Chris
Problem: I set the timming with the engine running on 87 octane fuel. The car was running great although my gas milage was terrible 12-14 miles per gallon. I tried switching to 93 octane and ran into serious detonation problems. I retarded the timing so that I am now at 8 initial and and I peak out at 24 at 2800 rpms. The detonation is gone, but the performance is aweful.
I have 3/4 of a tank of gas left, I quess I should be happy that my car likes 87 better than 93, but Help!!! I want to get the best possible performance 87 or 93...
Chris
Drifting
Joined: May 2001
Posts: 1,651
Likes: 13
From: Holly MI
I can't think of any reason a higher octane fuel would cause problems; it just doesn't make sense. I don't want to scare you, but have you checked the compression? I thought I had run into a bad tank of gas until I checked compression and realized I had blown a head gasket. Also, what else changed between the tank of 87 and 93? Did you fill up with 93 from a station that gets a lot of traffic through it?
I just read a good write up on octane in the C5 ZO6 section. Here is the link to the thread. It's post 18 I believe.
http://forums.corvetteforum.com/show....php?t=1187875
Ken
I just read a good write up on octane in the C5 ZO6 section. Here is the link to the thread. It's post 18 I believe.
http://forums.corvetteforum.com/show....php?t=1187875
Ken
Thread Starter
Racer
Joined: Jul 2003
Posts: 455
Likes: 0
From: Buffalo New York
Originally Posted by bb69
I can't think of any reason a higher octane fuel would cause problems; it just doesn't make sense. I don't want to scare you, but have you checked the compression? I thought I had run into a bad tank of gas until I checked compression and realized I had blown a head gasket. Also, what else changed between the tank of 87 and 93? Did you fill up with 93 from a station that gets a lot of traffic through it?
I just read a good write up on octane in the C5 ZO6 section. Here is the link to the thread. It's post 18 I believe.
http://forums.corvetteforum.com/show....php?t=1187875
Ken
I just read a good write up on octane in the C5 ZO6 section. Here is the link to the thread. It's post 18 I believe.
http://forums.corvetteforum.com/show....php?t=1187875
Ken
Advanced
Joined: Oct 2004
Posts: 64
Likes: 0
From: MI
Disconnect the ignition wire so it wont start, take the hose off the carb connect it to a glass container and have someone crank it so you can pump some of that fuel into the container to look at it. Last time something happened like that to me, I had pumped in a bunch of water from that stations crappy fuel tanks. Never went back there for fuel again. My truck ran the same way you are describing. Poured in 3 cans of heet to absorb the water and it helped but and didnt start running good til I was able to add lots of fresh fuel.
Racer
Joined: Jun 2005
Posts: 409
Likes: 13
From: Lavonia Georgia
Originally Posted by jeffro1234
Disconnect the ignition wire so it wont start, take the hose off the carb connect it to a glass container and have someone crank it so you can pump some of that fuel into the container to look at it. Last time something happened like that to me, I had pumped in a bunch of water from that stations crappy fuel tanks. Never went back there for fuel again. My truck ran the same way you are describing. Poured in 3 cans of heet to absorb the water and it helped but and didnt start running good til I was able to add lots of fresh fuel.
I got a tank of bad gas from a BP located right on the interstate....big place with lots of traffic. Had exactly the same problems as you describe. This was on the wifes DD which is fuel injected and computer controlled. The computer was unable to adjust any parameter to fix the crappy fuel problem and you won't either. Either drain the tank and have a nice bonfire, or add some fuel dryer and see if it helps. But I don't think you'll see much improvement until you get good fuel back into the carb.
Racer
Joined: Aug 2002
Posts: 289
Likes: 0
From: Albuquerque NM
Has to do with fuel burn rates...maybe a bad egr systems...the car isn't new enough for full electronic controls,,,,hmmm the higher octane could be unstable and burning off to fast in the low compression engine.....yeah there we go....fooobar...ooops snafu!
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Drifting
Joined: May 2001
Posts: 1,651
Likes: 13
From: Holly MI
It may be too late, but call the gas station. They have sensors that tell them how much water is in their holding tanks. I had a problem with my diesel truck not starting after buying a few gallons from a station. I only bought a few gallons because it was pumping so slow I knew something was wrong. The good news is that they said they would pay to have my tank removed and cleaned. The bad news is they said they would only do that if they had water in their tank, which the guy said they didn't. Anyway, he at least looked at the sensor and was willing to talk with me. Maybe, if they show water in their tank they will at least tell you and give you some free gas. Probably a long shot, but might be worth the phone call.
Ken
Ken
Burning Brakes
Joined: Dec 2004
Posts: 1,020
Likes: 1
From: Nederland Texas
Originally Posted by jeffro1234
Disconnect the ignition wire so it wont start, take the hose off the carb connect it to a glass container and have someone crank it so you can pump some of that fuel into the container to look at it. Last time something happened like that to me, I had pumped in a bunch of water from that stations crappy fuel tanks. Never went back there for fuel again. My truck ran the same way you are describing. Poured in 3 cans of heet to absorb the water and it helped but and didnt start running good til I was able to add lots of fresh fuel.
Thread Starter
Racer
Joined: Jul 2003
Posts: 455
Likes: 0
From: Buffalo New York
Just to finish the story...
I pulled the fuel filter I had just put in a few weeks ago and there were water white marks scattered over the filter. I pulled the plugs, which were also put in recently and they were carbonized as if the car was running lean. So, I pumped the gas out of the tank, put in new plugs and a new fuel filter, put in two things of dry gas to soak up whatever water was in the bottom of the tank, got a new tank of gas at a different gas station and the car is running great again...
I went to the gas station and they explained what happened and they said they have had no other complaints and that they weren't going to do anything for me. I didn't push it, but I won't be going back there...
Thanks for the help!!!
Chris
I pulled the fuel filter I had just put in a few weeks ago and there were water white marks scattered over the filter. I pulled the plugs, which were also put in recently and they were carbonized as if the car was running lean. So, I pumped the gas out of the tank, put in new plugs and a new fuel filter, put in two things of dry gas to soak up whatever water was in the bottom of the tank, got a new tank of gas at a different gas station and the car is running great again...
I went to the gas station and they explained what happened and they said they have had no other complaints and that they weren't going to do anything for me. I didn't push it, but I won't be going back there...
Thanks for the help!!!
Chris
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
Hey, go easy on these Mobil dealers. How do you expect them to make the gas go further so they can make a little more $$? A little water in the gas does wonders!
Makes you mad doesn't it when they say, "gee nobody else is complaining, you're the first one".
Bill
Makes you mad doesn't it when they say, "gee nobody else is complaining, you're the first one".
Bill
Melting Slicks
Joined: Aug 2003
Posts: 2,135
Likes: 2
From: Dayton Oh
Not to beat a dead horse but a couple of items. First, if all conditions are equal running a higher octane will not cause detonation. The reverse is not true. Second, I bet if you called the parent company of the service station then you'd get some satisfaction especially if the station admits they had an issue. I bet you'd at least get a free tank of gas. Reason being is that Big Oil does not like the bad publicity.
Instructor
Joined: Jan 2005
Posts: 159
Likes: 0
From: Chardon Ohio
Originally Posted by marshrat99
Reason being is that Big Oil does not like the bad publicity.