Master__Shake_

Lovely, another octane debate.

If your sensor is working, running 87, there will be no signs of knock at all unless at WOT. The compression of the 94 LT1 is 10.5:1, correct? It is completely possible to run 89 octane in this motor without any loss in performance, as long as you don't install aftermarket CI heads on it. I wouldn't get anything higher than 91 just because you really don't need it.

Tom Piper

The engines that have "premium recommended" don't have any limitation on 87 octane -- the knock sensors will cut back on the timing, and HP, and there will be no detonation.
There is no problem running 87 octane in a STOCK engine that has "premium recommended."

Since the LT4 says "premium required", it will not cut back enough -- you need high octane.

Tom Piper

tixeon

Is this just a Corvette thing? I have used it in other GM fuel injected vehicles for 20 years with no problems.

schrade

If ya' gotta' run low octane, either have the burn timing retarded in the computer (you'll have to reverse it if you go back to hi-grade),

...

OR, you can jump the AKS so that the timing stays at the default retard setting (which will set a code/light).

seenalot

tixeon, check post #4 in this thread. Jon (FICINJECTORS) is an expert and vendor for injectors so I take what he says as fact. I know GM only recommended their fuel treatment as the only acceptable one for 1988-89 Vettes

http://forums.corvetteforum.com/show...ight=Injectors

hexane

If you do that, you will only be set at base timing with no timing advance when throttle applied. The result, pop, backfire, bang, slow running, glowing exhaust manifold, chitty bang bang chitty chitty bang bang.

Swift_Striker

with my bad tune in my new engine I use a tank a day and at 11:1 CR and no knock sensor hooked up I need premium, quit whining.

GS4-LT1

Yes, I have. I loose 4 miles per gallon when running 87 with E10. With the 15 cent difference between 87 and 91, I come out ahead running 91. Stick with a non ethanol gas whatever octane you choose.

Tom Piper

Ethanol has a higher octane rating than gas, but less BTU content (energy) per a given volume.
Therefore, to do the same amount of work, it takes a greater volume of ethanol and thus less miles per gallon.

Tom Piper

Pseudomind

That's what I was thinking, fill up say four times a month, save $14.00 per month, saving $168.00 in a year, now get some engine work done some place for this amount. I know to each their own, it is your car, but in this day and age, just how far is this savings going to go?

God luck with whatever you decide!

schrade

How is all this???

The only thing I've ever heard of that lights up the exhaust manifold is timing that fires the air fuel with the exhaust valve open.

With spark at 0, or 2 btdc, the ex. valve isn't even close to opening. Nor is the intake valve.

Slight loss of power is all that will be noticed by by-passing the AKS. And the DTC for "timing retarded too long".

Can you explain a little more here??????

hexane

Try running your car with the bypass disconnected. It will feel so bad I guarantee you would not want to drive it more than 50 feet off the driveway. Basically this will "lock" your spark timing to the default base timing with no other advance. You motor could rev up to 4000 rpms, but your timing will still be at default, usually at 6 degrees. If your full throttle your car, it will feel like a slug and probably pop through your throttlebody, possibly ruining a delicate MAF sensor.

Usually your advance at idle is about 20 degrees because the computer adds about 14 degrees on for proper operation. Light to mid, up to full throttle, the computer can add anywhere from 14 - 36 degrees to base timing for proper cylinder pressure to get the car moving.

I'm talking about TPI cars with HEI distributers. Dunno if that applies to LT1s, but I'm sure the concept is similar.

cmontel727

I would stick with the higher octane! I tried to run 87 octane in my 87 and it started to ping under load. Even trying to baby it would, ping on tip in of the throttle. I promptly put some 93 octane in and I'm just starting to get my performance and mileage back.

I think the lowest you can go on octane is 91 in these cars or least for the L-98's. Of course your mileage my vary, just the results of my experiment.

GM Junkie

Just checked the fuel door on my '84 LT-1 - says "unleaded fuel only" - "premium fuel RECCOMENDED" (in english & french ) Been using 87 octane since I bought it last year - 12k miles - no ping - runs smooth. It's my DD - life is good!

lt4obsesses

On average, premium is about 20 cents higher than regular unleaded. If you buy say 15 gallons, that's $3. Go to Starbucks one less time a week and you've paid for the difference. We all really need to stop second guessing the pennies we save on lowering octane and start writing our representatives and insist that the oil companies be held accountable for their gouging of the American People