First off, great site, great resource.

If I read Shiv's reports correctly, it seems like the stock Evo 8 has real issues with higher-RPM knocking when running on 91 octane gas. I don't know much about dyno loads and all that but my understanding has always been that knock, over time, is going to be trouble.

Is this a real concern? Will the car adjust itself to the gas I'm running eventually and neutralize knocking problems? If and when that happens, what kind of power compromise will it mean?

Thanks guys

- EZ

 

if 93 is unavailable in your area could a mix of octane booster work? Or maybe go out and find some racing fuel and mix your own 93.

 

All indications at this point are that the ECU can and will pull enough timing to compensate for the 91 octane and offer sufficient protection to your engine. The consequence though is a significant drop in performance over 5k rpm and associated peak power losses. 93 octane will make it feel like a different car over 5k. Check out some of the tuners' sites on the left coast where 91 is the norm to see what they are saying.

 

Reading the owner's manual, it actually goes so far as to say that the engine was designed to work with 98 octane (!!!).

The semi-good news is that I found an area gas station that sells 100 octane: for those of you in the SF Bay Area, it's the 76 station at the corner of Almaden Expwy. and Foxworthy Ave. in San Jose. It is semi-good news because it's a good 20 miles away from where I live and because 100 octane costs twice as much.

 

Doesn't anyone in California and the "low octane" states think this is odd ? I mean selling a vehicle that needs a minimum of 93-94 "Road Octane" ( (RON+MON)/2 ) when the best you can get normally is 91 "Road Octane". Surely the stipulation of 98 RON is an unreasonable requirement for such low octane states, and there should be a side bar or something explaining it ?

 

Here in California, we can only get 91 Pump Octane wich is about 95 RON. Does this mean I am already voiding my warranty by loading only 91 Octane. Looks like I will need to get racing fuel concentrates for every fill. I have used this on my MR2 Turbo and boosted 19 lbs and no knocks. Here is a link.

http://www.torcoracefuels.com/ACCEL%201.htm

 

If you can blend 100 racing with 91 pump to get 93+ in the tank. I'm lucky enough to live close to a station that sells 100 and do that. We really get the shaft in California. Not only do we only have 91 we also pay 2 dollars or more per gallon for it these days.

 

Thanx for info I knew we had different rating system but didn' quite know what difference was....we also have 100 rating gas as well (Japan rating) a sidenote.. question for the guys in US.....
I,m starting to see more and more US products over here and was curious about the Octane boost products. Any good? Is worth the money?? I was thinking about trying some made by NOS (race only formula) Has anybody here tried this product before??

 

I don't see why your car wouldn't run prefectly ok with 91 octane. The car wouldn't be US legal if the car wasn't capable of running 91 octane. That is the US standard if i cna recall.

 

Shiv told me that these cars pull back timing way before knock occurs....apparently there is a big safety margin built in

 

I do not think that NOS Race only formula will help you any. It will only race octane rating by 7-10 points. For example, 91 octane will be 91.7 which is a 7 points increase.

 

Wow only 7 pts. Thanx for the advice and saving me few bucks...er, yen PEACE

 

As for my car which has Vishnu Stage O plus downpipe and high flow cat. there is no knock or problem or drivability issue whatsoever. Its totally like a stock car only somewhat faster.

Given a little time - from what I see going on around Vishnu's shop, (I live nearby) many of the problems attributable to Calif. 91 octane fuel will get sorted out. There are clearly other ways to deal with much of the octane problem besides just going to different gas. In time, it will be very engouraging how much we can get out of the Evo on 91 octane. Of course this will involve doing things which will void the warranty. And all this takes time to put into place when dealing with the factory ecu. The upgrade path will not be conventional; i.e. not what you see everyone talking about in these forums. Look for some interesting mods that are not even being discussed at this time.

Patience pays!