Hi everyone,

As you can see from my signature, my car is a 1999 JDM S2000 (11.7 compression ratio) with Mugen N1 ECU, mugen radiator, radiator cap, thermostat and header.
It also has a Mugen exhaust, a Gruppe M air intake, Spoon throttle body, and a decat.

My problem is this .. there seems to be engine knock/pinking sound on WOT, especially in low-ish RPMs. Especially on uphills, etc.

The fuel is not high in octane in Malta, so I have always added half a 1-litre bottle of Fuchs/Silkolene Pro-Boost Octane booster with every full tank of fuel.

The knock-problem is much worse these last couple of days, I've been wondering why all day .. and now I think I know why. My car has never had a loud throaty noise as standard S2000s do with the air-intake cover removed. So about two days ago I removed one of the two "tumors" which make up the Gruppe-M intake.
It effectively gives the same result as popping the lid off the OEM intake .. you're still filtering the air, but you get much more hot air from inside the engine bay.

I made a search and read several topics. It seems like the Mugen ECU is designed to run LEAN. I'm guessing this is the problem inducing the pinking .. when combined with low-octane fuel.

So my question is this ... is there any way to alter the fuel mixture of the Mugen ECU? Can I "fix" the Mugen ECU to work in my circumstances?

If not, whats the best way to fix this problem?

Thanks

 

What spark plugs are you running? What is your ambient temperature?

 

Try some race gas and see what happens. I bet you are not running high enough octane.


One suggestion:


For less than you are paying now for your octane booster you can get a gallon of Toluene at a paint store. Toluene is a component in gasoline and it will boost octane, it is also component in octane boosters, but you are buying a brand name and not getting the bulk price . However....Toluene is more corrosive to petroluem based products like o-rings and paint. Do not use too much in a tank, and you will not ruin rubber parts, wipe up spills on your paint or it will eat through it. But you can get a gallon for about $12 and add one fourth per tank to the highest octane you can find and see how that does. You can experiment with how much you need to add to get enough octane if you need a little more.



But I would lay off WOT uphill runs until you get it figured out or you can destroy your toy. But I would not even consider running a Mugen ECU with low octane fuel. You are better off getting a Emanage or something you can customize. I thought Mugens were programmed to run on Japanese fuel which is listed as 98 octane (but I thought on a slightly different scale than the US measure) and 91-93 is pretty much what we get here. The mugen advances timing much more than stock along with leaning out the mixture which runs hotter.

 

Thanks for your replies guys;

Re spark plugs, I am using NGK PFR7G-11S, which as far as I know are OEM items. I checked them a year ago, and they were like-new back then. Should I check them again? Or should I change the heat-range? I know nothing about spark-plug tweaking to be honest.

Ambient temperatures at this time of the year are about 15 - 18 degrees celcius .. which is 59 - 65 fahrenheit.

Re Toluene, I never heard of this ... and to be honest, I wonder if its available in Malta .. paint stores should stock this?
Who usually uses it? Car sprayers? Furniture painters?
It would be great if I can get a "cheap" version of the octane booster.

You're right .. I will be very very careful from now on .. and I will put back the air-intake cover, because it seems to be much worse with it off.
But still, the car has always been prone to knock, and I really want to see WHY, and how I can fix it.

 

Yes, the mugen ecu was designed to run with japanese fuel.
Thats why I always add the octane booster.

I used to add 1/3 of a bottle before. Then I noticed some knock at certain situations.
So I started to add 1/2 bottle with every tank. It seemed ok then.

But last Sunday there was a lot of knock. I wondered all day why it was so bad, and then in the evening it dawned on me. I removed a part of the air-intake the day before to get more NOISE .. and this must have been the culprit.
But it shouldn't knock with the air-intake open, right? So there MUST be another problem.

 

You should definitely try going 1 step colder on your spark plugs. I'd try NGK BKR8EIX, and regap them (carefully) to .040" (max). Are you sure your cooling system is working well? If your thermostat is old, maybe you should replace it, and try a more efficient coolant mixture (less antifreeze).

 

Are you sure you don't have a clogged fuel injector? Maybe you should consider sending them to Injector Rehab.

 

Or carbon deposits if the problem is getting worse. I have no idea what kind of detergent additives are used in Malta. Maybe run some techron concentrate.

 

How will I know if the I injectors are clogged ?
Will it help if I use some injector cleaner with an empty tank?

Is that what techron concentrate is?

 

What difference will the 'one step colder' plug do?
I really never researched this topic so I need help!
Will it have any bad side effects?



Re cooling system.. It's funny you should mention this.
A few months ago I replaced the coolant with Fuchs long-life pre-mixed coolant. I emptied the old coolant (I even removed the bolt in the engine block) and filled it with the new coolant. I didn't flush it though.
The thing is.. That since that day, the (cabin) heater does not work so well. It used to go really hot before, but now it just blows warm air.
I did my best to bleed it to the best of my knowledge, but there is no bleed valve in rhd models. The temperature gauge works like normal, and the fan turns on and off as usual.
Is this a 'sign' that there's an airlock?

Should it be affecting knock?