I have noticed that if I am unable to get Optimax and fill up on a tank of super and then later refill with Optimax I get a misfire. This only happened at 1500 - 2000 revs and lasted for the whole tank. I can cure it by either putting another load of super in or just wait for it to go away.

 

Was it a shite tank of Optimax or is it the engine(ecu) reacting to the change in petrol ? It's been suggested to me that so few people use Optimax that the petrol can be "old".

 

Just wondered if anyone else had noticed this ?

Well I knows the previous owner just used super unleaded on my 300zx. I have been using optimax ever since. My car also semi misfires like a kind of stuttering at low revs. Sometimes this creeps up to the high revs too. I thought it was my PTU or temp sensor, but I have changed both of these and I'm still getting the problem. If I recall the problem started about a week after I put octane booster in my car.

 

I may try super unleaded for my next couple of tanks and see what happens.

dazuti, is your zed an import? if is worth checking to see if your still running Japanese spec plugs, if you are change to UK spec plugs will most likely sort it.

 

Jeff TT

What plugs did you put in mine Jeff ?

Had the 60k service back in November.

What's the difference Jeff ?

 

 

Originally posted by Jeff TT

dazuti, is your zed an import? if is worth checking to see if your still running Japanese spec plugs, if you are change to UK spec plugs will most likely sort it.

 

Jeff TT

It actually started after I'd had new plugs put in. They're HKS ones are were a temp rating lower than the last ones.

 

When the tanks next empty I'll stick in some Optimax and see if it happens again.

 

Jeff, It is an import..

well my first time postin here goes.

 

I use optimax all the time anything else and the engine pings.

but then fuel here could be a little different.

 

optimax is our highest rated fuel at 98 octane.

all other fuels are standard 92 octane too low for the z

 

(thats in australia btw)

Originally posted by Zdownunder

well my first time postin here goes.

 

I use optimax all the time anything else and the engine pings.

but then fuel here could be a little different.

 

optimax is our highest rated fuel at 98 octane.

all other fuels are standard 92 octane too low for the z

 

(thats in australia btw)

 

 

 

It's the same here mate!

 

By the way, how much is it over there?

Originally posted by x-biker

It's the same here mate!

 

By the way, how much is it over there?

 

Well not quite, std unleaded is 95 octane (I think) so the situation here isn't quite so bad. But you don't wanna get started on other countries fuel prices ! ;)

Originally posted by dazuti

It actually started after I'd had new plugs put in. They're HKS ones are were a temp rating lower than the last ones.

 

When the tanks next empty I'll stick in some Optimax and see if it happens again.

 

Jeff, It is an import..

so then has it actually dawned on you that it might be the plugs?

Yes, plugs was my initial thought as they'd been changed. It's just weird then that it's fine on super and not on Optimax..

 

I guess a few more experiments are required !

OK. Here are the results....

 

The HKS Spark plugs that were installed when serviced are colder than my old ones. Only when the engine is cold do I seem to get a slight misfire. I've now found a couple of other references about colder plugs and this happening by searching the forum.

 

The funny thing is that this only happens when Optimax is in the tank. Go figure.

 

The cooler plug were fitted to offer better protection at high boost (the garage who fitted them are prepared to exhange them if I want). Any thoughts...

I still want to know what the difference is between UK and Jap plugs ???

 

Jeff ?

Me too.

 

Mines an import, so what should I replace my sparkers with?

(I'll do a search before the forum police pounce) :D

Originally posted by AndyP

Well not quite, std unleaded is 95 octane (I think) so the situation here isn't quite so bad. But you don't wanna get started on other countries fuel prices ! ;)

 

 

Yup, std unleaded is 95 RON, super unleaded is 97 and Optimax is 98.

Whoops,

 

Just ran a full tank of Optimax away tonight buzzing around Kent. No problems at all.

 

Don't you just love a Zed...

Did you change anything in the end ?

Nothing changed !

However, it might be to do with the fuel pump. It sounds noisier than normal and I had a wierd "buzzing" noise the other day.

Hey Dazuti, if you fit cooler plugs then cylinder temps dont rise as high as they should,

this lowers exhaust temp, which lowers turbine speed, which lowers

boost pressure.

 

Hears a question to all, why is that Lpg has an Octane rateing of approx 104 (110 outside UK) yet has a calorific value of 15-20% less than petrol and produces 15% less power??!! But is slightly better for turbo engines as it runs hotter(see above) and because of higher Octane value engine does not knock(pink) so easily therefore able to take more boost!.Give's with one & take's with the other!