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Hey, I finished my swap back in like july or aug and just recently found out (like just after my last fil up) that I should've been using 93 octane or better instead of regular 87 like I have been. Now my engine sounds like crap all the time. My gas light just came on today and i intend on filling it with 93 tonight and for now on, but do you think I have caused any damage to the internals of my engine?! I know knocking is bad, and sometimes my engine sounds like it's got a woodpecker in it, lol.

Typically it is not great to run it like that. However the knocking is what can do damage. How long have you been running it like that?

(and btw: 91 octane is fine, all of the K-series engines have a warning about 90 octane or above [though I regularly use 89 if the price for higher is too mich])

i really don't think the gas octane rating is the reason your engine is sounding like cr@p - especially in a normally aspirated mass production engine. octane ratings are recommendations and any production line engine should run just fine on 87 octane..

if what roundtop is saying is true - that all k-series engine have a warning about running on a higher octane gasoline (less chance for detonation but a slower flame rate) then your use of 87 octane instead of a 90+ would have been a good decision, not a bad one.

i would rule out HLAs, timing belt tensioner/bearings, and other legacy problems with K engines before jumping to the conclusion that a slightly reduced octane rating hurt your engine..

an easy way to tell if your engine IS knocking is to find a nice hill and drive up it in 4th or 5th, and floor it while the RPMs are way below the power band (but not so low that the engine starts to shudder). you will hear and feel it knock if that's the problem.

The KLZE's do require a high octane. K8's ,87 is fine. If the motor always sounds like sh1t then I doubt that the high octane will cure that. On the other hand it should clear up any knocking your hearing during accelerating.
If the knocking doesn't go away with the high test then something more serious could be wrong.

Andy P. 93 GS

Ok. I've been running the 87 octane since my swap. I've read on here that true j-spec engines (which I have) were designed to run on 100RON in Japan, which is equivalent to like 95 octane, and that using the lower octane fuel would cause combustion from compression not from the spark itself, which therefore would cause knocking (not to tell you all what you already prolly know, just trying to reason my deductions). The engine has only been run since the swap so like 4 mos or so, give or take a week, and was serviced and stuff (new belts and checked and tightened the tensioners) in aug. So i would hope that it wouldn't be them! My fluid levels are fine (but prolly time to change the oil now anyway). The neutral switch still isn't hooked up, cuz I've had no time to play with it. Oh and my idle had been funny after my engine flooded about a month ago (i think the gas i put in it the night before was too watery tho). ok enough rambling, hopefully with all this info can give a more fine tuned reply.

PS: It is a KLZE.

i'm still not convinced that you'd get detonation or knocking in a normally aspirated 9.2:1 compression engine with 87 octane gas unless there were other *serious* issues with the engine.

i could see some *minor* performance or emission issues - and MAYBE some knocking when running WOT at low rpms under a heavy load (up a hill or towing something)...

i'm not suggesting either that you have a serious issue with the engine.. i just don't think that a slight difference in octane ratings is the cause of your poorly running/sounding engine.

Hmm. Ok, so I might as well just send it off to my mech and see if he can't diagnose it. Hope he's ready, nowadays most mech's i've come across use the car's cel codes and pc stuff to diagnose but with the jap ecu there's no cel. lol, oh well. But it couldn't hurt anything but my pocket to put the higher octane in right?

KLZE's have 10.1:1 compression ratio unlike the american counterparts. I'd stick with the premium.
Good luck with the mechanic.
Andy P. 93 GS

Originally posted by andy:
KLZE's have 10.1:1 compression ratio

10:1 not 10.1:1

thanks andy.

Originally posted by DJester187:
Hmm. Ok, so I might as well just send it off to my mech and see if he can't diagnose it. Hope he's ready, nowadays most mech's i've come across use the car's cel codes and pc stuff to diagnose but with the jap ecu there's no cel. lol, oh well. But it couldn't hurt anything but my pocket to put the higher octane in right?

If he has the PC he won't need the CEL - the codes will still be there to read. Actually all you need is a LED.

Ok, filled her up with 93 octane and noticed a much better pick up especially in 1st and 2nd (they don't top out as fast as before), and then engine went from sounding like a helicopter to a lawn mower (figuratively speaking). The idle is still funky, it usually sits high, like 1, 1.5 but will drop to like 4.5 when ever i'm at an idle for like 10 sec or more, and i think the knock sensor may be bad cuz when i put my ear down to the engine, just above the knock sensor, it sounds like tapping/clicking sound. kinda unsettling.