Out of curiosity I have a 01 and it can only run on 98 RON, I gather with the newer S

 

This is a topic that has been posted about hundreds of times before.

The S2000 ECU will adjust the timing to suit 95 RON but you will get less power.

The following points are very much arguable and the answers you get will depend on the person:
- Whether the power loss is noticeable compared to the losses from changes in atmospheric pressure, humidity, temperature, weight of the car (i.e. fuel, what's in the boot, how much you had to eat) etc.
- Whether the extra money for 98/99 RON is worth it.
- How long it takes for the S2000 ECU to readvance the timing after backing off for 95 RON. If it ever does.

I run whatever super unleaded I can get my hands on at the time. Sainsbury's is the fuel of choice, Tesco have just started doing it, BP charge a fortune and there's no Shell garage locally.

I find that Texaco, Esso etc don't stock super around here.

 

I wouls say run Super if you can find it.

Consistency is the real key, or the ECU will be constantly changing the timing between tanks.

I think the power between 95 and 98 would be just about noticable.

MB

 

Good points, I always stick Optimax in,

I was after the actual differences between the two engines,

The earlier engines say 98RON only, the later engines say 95 or 98 RON,

Why not 95 RON in the the earlier engines? is there a good reason why Honda have said this?

There must be some differences between the two actual engines if the early ones are not 95 RON?

 

I've had 00 and 04 cars. I ran both on 97 when I could get it and 95 if I couldn't. I have noticed no difference between either car on 95. AS DBM says the ECU adjust for it AFAIK it does this on all years.

 

I have run one or two tanks of 95 UL in my S since I had it and I think the difference is barely noticable... it seems slightly less responsive and a little less willing to rev but as I said it's very slight

I had a DC2 Integra Type-R and the difference was like chalk and cheese between 95 and 98...

 

No engine differences AFAIK - the difference will be in the ECU mapping. The engine doesn't really mind what grade of fuel it sees, to an extent - its the ECU that governs the fuelling and ignition timing so that will be the change I would think.

Earlier cars dont say they cant use anything but 98, if you look on the fuel lid it states it will be ok but the ECU (or engine which is incorrect) will adjust and you may notice a performance drop.

They may have removed this to avoid confusion, and probably better marketing wise. May have put some people off thinking they can only use 98!

The ECU uses a knock sensor to detect fuelling changes - hence why things like Mugen ECU's are suicidal in my book (doesnt use knock sensor at all!)

MB

 

I keep seeing this come up but I don't know where from?

Mines an MY99 and it say's, on the filler cap, that I can use 95 if 98 isn't available.

Andy

 

I think it is just a sticker thing, the early ones only had 95 on and most now have 95/98 on.

 

Nope, the knock sensor is used to retard the ignition based off how the ECU interprets the knock signal. The only full fuelling correction is the fuel trim (long and short term) based off the narrowband O2 sensor signal.

The stock ECU map deliberatly has more advance in places than the engine will tolerate under most circumstances without knock. So it's normally pulling some advance. This is done in part at least to help with emissions.

My contrast, the Mugen ECU has ignition mapped to provide the best safe torque at a given rpm. It's very well mapped. Running the Mugen ECU on a UK which has had the right preparation is perfectly safe.

Contrast that with cars bolting on forced induction and relying on the knock sensor pulling enough ignition advance to stop detonation. Since the knock sensor signal can only be used to retard after problems have happened, you always get some degree of detonation. With forced induction the 'some' that happens before the timing is pulled can be far more damaging than that on an N/A engine. I've yet to see any engine damaged by running the Mugen ECU. I have seen several badly damaged by running forced induction while just relying on the knock sensor for ignition control.

Back to the original question. For 02+MY the ECU map and software changed somewhat. Fuel and ignition maps are different, as well as a slighty changed knock strategy.

One thing to always bear in mind. The dynamic compression ratio of the engine (which comes from the cam profile, timing, pistong design, static compression ratio, intake and exhaust manifold design etc) is designed for high octane fuel. While you can map the F20C to run safely on 95Ron fuel (or rely on the appropriate stock ECU to adapt to a degree for it), the engine will never run at it's proper design efficiency.

-Brian.