Well my car ran like **** and we found out the timing chain was off by 8 degress retarted (the dots that are supposed to line up were 2 teeth apart). Dont ask how it was like that... Its a long story!!! Anyways, I put in 87 Octane gas and it was performing actually better then ever!!!! I never felt my car with that much power before. Anyways, Rick, the motorsport guy that fixed my car, tols me that if it is running this good with that low octane, then it should run way beter with a higher octane. Upon my next fill up of 91 Octance, I notice that my throttle response isnt as good anymore and the mileage on it is horrible. I then proceeded to put 87 octane on the next fill up and what do ya know!! The power was regained again!!! I dont get it? Isnt it supposed to be the other way around? Also, when the timimng chain was fixed and adjusted to its proper position, there was 87 Octance gas in there. Im thinking that the timing got used to the 87 Octane becuase that is what it first used as its initial gasoline when It started for its first time when the timing was right! Im just guessing that, BUT what can be the possibilty!! Im totally confused!!

 

WOW, you'll save alot on gas...

 

I dont get it though man??? Can you tell me why and give an explanation???

 

I'm no expert but a higher compression engine will require higher octane gas to prevent knock. LT1's have a 10:4:1 compression - I'd say 89 is the lowest you should go.

Probably someone swapped your head gaskets with lower compression ones??

 

timing chain is 8* off?

go with 91 octane and get the motor fixed. If anything, the knock sensor is probably going nuts and pullling enough timing to keep things running at lower octane, but at 91octane you're probably only getting a bit of knock so the car is constintly adjusting for knock, running ok, and as the knock retard dissipates the knock comes back.

Just a guess... but things are NOT good. The timing chain should be 0* because it affects alot more in the LT1 pcm than just ignition events.

Go with 91 or high octane to save your engine, and get the timing fixed. After the fix, make sure you reset your PCM by pulling the PCM fuse (inside fuse panel in dash/driver's door area).

Good luck.

 

No wait!! HOld your horses there! The timing chain is now FIXED! It was throwing off an EGR Crank Position sensor trouble code. We got that fixed and the timing is now perfect. But what I noticed after this is even though I reset my computer, the 87 Octane is running excellent. I then put in 91 and its not so excellent anymore... keep in mind this is AFTER the timimng chain got fixed, before the timing chain was fixed, it ran like complete bull s h i t, and it couldnt make it up the slightest hill on WOT, now the car is running crrazy!

 

LT1 gaskets are already pretty thick, I don't think you could get more than 5cc's more in the combusion chamber with a gasket swap. I doubtr that's enough to drop it to a smoth running 87 octane compression. Besides, if things were fine at 87octane, the 91 would just run smoother.

Sounds like something is wrong with that engine and the PCM is messing with things, but can't compensate at 87 octane (there is a limited range for adjusting knock retard just like there is for fuel delivery).

 

so the 91 octane is fine, but it doesn't feel/sound like the 87 octane did?

Or is the 91 actually stumbling or throwing codes?

 

O hey guys... one more thing.... maybe this is important
I am expereinceing and trouble code with my EGr valve AND o2 sensors at the moment! Im guessing this is the whole secret behind this operation!! Do you think I should get those fixed, and then get my pcm tuned and then stick in 91 or higher octane? What do you think?

 

replace the O2's... no wonder it's running like crap.


Why do you need the PCM tuned? what mods have you done that warrant such tinkering?

and YES, ALWAYS stick to premium in a high-compression engine...especially in the spring and fall (when gas companies are making the switch from winter-formulation to summer-formulation gasoline).

 

Ok so its just those damned o2 sensors and egr valve is what causing the ruckus? Should my car be even MORE powerful then it already is? My car is almost bone stock other than the muffler and intake. I thought tuning it would help the computer use the engine more effieciently, but I guess its just the o2 sensors! Wow, should i experience an even more drastic change in power? And one more thing, can I just get o2 simms instead of the sensors, cuase the last time I bought a sensor it was expensive

 

Just to let you know by the way......... My car had the following probs:

O2 sensors
Timing Chain off by 8 Degrees
Running On 87 Octane
Egr Prob
Oil Pressure Problem

And at that time I was seriously going to just crash my car into a wall, I think it had close to 80HP at the time, becuase it couldnt even make it up the slighest hills and It was running like major crap. I recently got the timing fixed and I felt am INCREDIBLE increase in performance, Im hoping that with the o2 sensors or simms I can feel an ever more increase in power and especially when I put in that 91 Octane with some octane boost!

 

You can NOT O2 sim the front O2's... which are the only ones that would affect your drivability and the PCM.

O2 sims are for 96/97 LT1's (and LS1's) that have 4 O2 sensors. The 2 front ones (1 for each bank) are active feedback, the rear 2 (which are not existant in Pre-96 vehicles) are only to verify the catalytic converter's operation... which is ironic since the O2's fail WAY before the GM converter does. It's almost worth putting O2 sims on a low-milage LT1 and re-connecting/installing new O2's after 300,000 miles or so when the cat is nearing it's life expectancy (although I have heard of them dieing early due to abuse with leaded fuels or such).

 

oh yeah... and octane boost is useless.

When it says it can raise your octane by 3 points...it means from 91 to 91.3 octane. spend you money on 1 gallon of 104 octane race gas will get you farther ahead, and cheaper.

 

I want a set of o2 sesnors (that go out of the manifold) and a set o2 simms that go after the cats. Anyone wanna sell me this?