Valcore

mine also knocks on 87, 89.

on 93, you would never guess this engine is 17 years old

pillsbury

just like outhers have stated unless you are running 10or higher compressin high octaine will not help yuo . If you have a turbo or supercharger ( the kb has a sticker on them saying to run high octaine) then you need to run the high octaine fuel

nitrous_bob

sure you'll feel a difference, it will be slower

unless you add timing to take advantage of higher octane, the higher combustability of the gas will make your car slower.

adding octane allows you increase timing which can make more power....but in turn REQUIRES you to add more timing to make the same power.

only reason to add octane is if your pinging at too low of rpm, or making crazy boost and worried about running too lean

kartracer55

octane booster = rice.... 1 point = .1 octane... they make you think its a 10 octane boost but its not.

If you dont have cats just pick up a gallon of 110 race gas and dump it into a tank of 94... you see a a bit of improvements, but keep in mind, its leaded, so dont run it if you have cats

Jim

Pure5.0

you should not have knock with 87 or 89 octane. I would put some fuel (engine cleaner) into your tank one time to help it out. If you get knock with regular gas then you might have build up in your comb chambers leading to a higher compression...and with the addded effect of stock timing (if that is what you have) then you very well could have knock.

That is why you probably feel a difference with 93 octane or octane booster...because of the power loss due to the knocking...but i think your head is putting out more of a improvment than there really is. Mind tricks created by your mind.

But as far as you are concerned...you should not have knock. I run 93 octane only because I have 14* timing and that is premature to what it can go before knock. I can go past 20* before I hear knocking at idle.

red347

VP Racing Fuels has MS103 which is an unleaded fuel. As an example of how much of a difference there is between octane from a power perspective, we have a customer who races his 03 Mach 1 on open track days. The car is fairly heavily modified. Exhaust, intake, X-Cal w/ 3 tunes, etc. After Dyno tuning the 92 octane tune delivered 322.4 rwhp and 325.5 ft/lbs of torque. The MS 103 octane delivered 328.0 rwhp and 331.4 ft/lbs of torque. So a gain of 6 HP for an extra $5.00 per gallon. Here is a link to his car.
http://home.fastspecialties.com/inde...=detail&id=142

Ron

vfast

what higher octange does is allow a more complete burn over the entire piston with the right compression instead of hot spots which is the ping you hear.....my guess you have alot of carbon on the pistons and a wore timing chain....I use ,89 in my near stock 1989 lx..and 93 in my s/c '90 no ping

red347

I don't believe that flame travel or "eveness" has much to do with the "knock". The octane rating of gasoline tells you how much the fuel can be compressed before it spontaneously ignites. When gas ignites by "compression" rather than because of the spark from the spark plug, it causes knocking in the engine. Knocking can damage an engine, so it is not something you want to have happening. Lower-octane gas (like "regular" 87-octane gasoline) can handle the least amount of compression before igniting
Very similar to "pre-ignition" but not quite the same.

The knock every one hears is the mixture starting ignition while the piston is still traveling up on the compression stroke. Under the right conditions (like under too much boost or with N2O, something has to give. Either a hole in a piston, bent rod, or a blown head gasket or worse.

Ron

Tims 88GT

red347 thanks so much you helped me out, in my dads truck the plugs turned red now i know why.