I'm new to this forum so please excuse what may be a dumb question but I would appreciate some experienced advice. I'm in the process of buying an EVO IV straight from Japan and am worried about the fuel I can run in it. I understand they were meant to run on 100 octance, but feel I will be forced to run on 95 here in Ireland most of the time. Is this dangerous to the engine or is the only drawback reduced power???

Thanks in advance,
Patrick.

 

There's a lot of misconceptions about the 100 Oct in Japan. Yes, it is 100, but by the Japanese Octane rating which makes it a little less than 99 RON, I believe. This doesn't help your problem though, I know the 6 has an anti-knock sensor which retards ignition, don't know about the 4. If it has one, don't worry.

 

If it is tuned for the "100" (99) octane and you run 95...you may get some knocking (detonation) and you will need to adjust the tuning (have someone do it!!!...do not try yourself), possibly with an aftermarket ECU (which will give you much better performance if tuned well, anyway)
If the knock sensor is on there, I agree...no problem, but you would still benefit tons from an ECU. ("computer")

If you really want to know about fuels and additives, etc...


http://www.faqs.org/faqs/autos/gasol...section4-.html

 

Just install a HKS EIDS...

 

The EVO engines are protected by knock sensor that are constantly listening for knock. If the engine was meant for 100 octane fuel, the timing would be set for that octane. Once you start filling the tank with 95 octane, the ECU will pull back the timing a few degrees because of the dentenation that will be picked up by the knock sensor. This safety feature will allow you to fuel your car up with even lower octanes. The drawback is that as you lower octane the timing will be pulled further and further back. You will lose power every time you lower the octane. Another drawback is that if you suddenly add the 100 octane back in, the ECU will not advance the timing back immediately. It will gradually sense that it hears no knock and pick up the timing little by little.

Jeff

 

Does any one know what sensor would pick up this knock and signal ecu to retard the timing? would it be the cam angle sensor or carnk angle sensor? sorry for the noob question

 

Nice 9 year old thread bump. But to answer your question it's the knock sensor which is different from both the Crank and Cam position sensors