I have a JDM H22 with 10.6:1 and I always use 93 octane. However, I live in Florida were it is hot and muggy, and It feels like the knock sensor is backing up timming between 3-4K. Now I have read the hesitation threads and I have done everything but change the knock sensor. (no codes). When I put 104 octane boost in the car the engine runs great. Any suggestions?

 

JDM should be run on the highest octane you can

 

Maybe you need new spark plugs...

 

there are numerous engines here in cali that run 12:1 + compression on 91 octane. you will be fine.

 

maybe you just need a tune up

 

Brand new denso iridiums, msd wires, 6a BTM, rotor and external coil. The only thing I can think of is to change the knock sensor

 

did you double check the gap on the plugs?

 

i have the same problem, or atleast recently, i have new iridiums, gap is correct, timing is good, just a few days ago once i get to about 3k it seems as if its retarding a bit. i used an octane booster to see if it helped and it didnt. but this is the first time ive ran it in the heat.

 

Yeah, they are within spec, and I also had the same problems running the zex plugs. I dont think its the plugs.

 

Maybe it could be ur fuel filter, since its at higher RPM"s it could be a fuel filter or something.

Or i could just be totallly wrong. IM just tryin to throw some possible ideas out there.

 

From everything I've ever read about "octane boosters" that are all BS. A tank of 93 with a bottle of 108 octane boost will be like 93.8 octane, not even a full point increase.

 

I can tell you this much. This weekend up in Gainsville when I took my car on the road course, I put 5 gals of 100 octane in my car (JDM H22A) and it ran as smooth as glass. When I put 93 in on the way home, there was a noticeable increase in engine noise and smoothness. I can also feel the knock sensor compensating for it as well. I'm gonna back my timing down a couple of degrees and see if that helps...

 

98% of the time I would say you are right. However, after reading Super Streets June issue, it shows test on the octane boosters. Most that say "adds 5 points really means you go from 93 to 93.5 like you stated. But testing on the 104 brand they actually saw 3 full points. Also it cleans out injectors and "deposits including those left behind by MMT"

 

to figure out octane after octane boost, figure 9.5 gal of 91 octane, and .5 gal of 100 octane booster, soo.... .95*91 + .05*100 = 86.45 + 5 = 91.45, sub 104 for 100 if its 104 octane booster, or 117 if you can get xylene from a paint supply store...