Petrol Octane Rating

[L18M]

Hello,

New to the RX7 lounge.
Was reading old info about the FC\'s and what petrol to use.
It seems that in the states they have a lower octane rating that what uk have, around 85 RON to 87 RON for US petrol and 95 RON for UK fuel.

In the info it recommendes to use high octane fuel but does not say which RON to use. i think high octant in the US is about 95 RON ish.

so with that in mind the logic would be that it would be ok to use regular 95 RON fuel from the uk as opposed to the high octane 97 RON to 99 RON you get in uk (btw i found 99 RON in tesco petrol station in oxford)

I believe that the octant (RON) figure does not necesary mean more power but it means the petrol can withstand higher temp b4 detonating thus preventing early detonation.

so with this info. what are peoples thought / facts on using 95 RON (cheaper petrol) instead of high octane 97+ RON?

Personally i have not noticed any difference bearing in mind i only have stage 1 tuning and not a monster under the hood.

[S3TH]

Hi dude, normal in Japan is 99, high is 102. In America they almost always have a different map...

[L18M]

Hi dude, normal in Japan is 99, high is 102. In America they almost always have a different map...

bearing in mind these cars were produced in 1988-1991 or so.. were 99 RON avalible back then?

[elford_tim]

Erm, in the US they use a different way to measure the octane rating (have a look at http://en.wikipedia.org/wiki/Octane_rating) so it does come out \'lower\' than the European ones. That said, I think on average their ratings are still a tad lower compared to what we can get here but not as much as just comparing the numbers suggests...

[Prof]

It\'s fair to say that the cars were designed back when petrol wasn\'t at the octane rating it is now, but given that any turbo charged car will benefit from the additional safety margin you get when running higher octane (since the octane rating is basically a measurement of knock resistance), it\'s not a bad thing to run the cars on 99 RON.

[marx-7]

I live in the netherlands near to the German border where you still can get 91ron. What i have learned from our RX-7 guru in the club is that for a non turbo like my FC, the lower the ron is the better it is. So when i can i get 91 in germany and when not the normal 95 in holland.
 
I understood for turbo\'s it\'s better to gas up with 98ron.
 
is that correct?

[m1tch]

Jap ECUs will be running at 100RON maps, its best to get the higher RON fuel cause they are perfomance cars, the higher octane fuels usually normally have better detergents in them so it clears out some of the rubbish in the engine and lets the engine run more efficently. Also the higher the RON, as prof said, the safer the engine is protected from detonation or knock, either of these in a rotary means a rebuild, so the options are either to run the engine on the best fuel you can get, or face a £3,500+ bill for a rebuild

[L18M]

thanks for the replies.
think i\'ll stick to higher ron then.
tho in some ways i want my engine to blow so then i will have to rebuild n also at the same time be a gd excuse to get it street ported also lol

[Frost]

Just thought i would add to this.
I was reading my old mans copy of practical classics a thew months back and it said in there that regular fuel evaporates at a higher temperature than super.
So lower the RON higher the evaporation point, fuel injections cars arnt affected by this but carbs are but only on a baking hot day.

[m1tch]

thanks for the replies.
think i\'ll stick to higher ron then.
tho in some ways i want my engine to blow so then i will have to rebuild n also at the same time be a gd excuse to get it street ported also lol

Here are the options for rebuilds:

Engine is rebuilt before its blow = Seals changed, engine put back together
Engine is blown and then rebuilt = Seals changed, new rotor housing, new rotor, engine is put back together and a large bill added on

Its best to rebuilt or port the engine before it goes pop, get a compression test done at rotechniks or another rotary specialist to see how long you might have left.

Also make sure you get the oil changed every 6k miles or so with mineral oil and make sure that you warm the engine before driving it, make sure that the water temperature is in the middle of the guage before you boost at all, else you will have a shorter engine life.

[L18M]

gd points.
i had comp test n was reading 6.5 - 7
but they told me that it does not give much indication how long the engine will last.

any ideas..? they were quite even though

Here are the options for rebuilds:

Engine is rebuilt before its blow = Seals changed, engine put back together
Engine is blown and then rebuilt = Seals changed, new rotor housing, new rotor, engine is put back together and a large bill added on

Its best to rebuilt or port the engine before it goes pop, get a compression test done at rotechniks or another rotary specialist to see how long you might have left.

Also make sure you get the oil changed every 6k miles or so with mineral oil and make sure that you warm the engine before driving it, make sure that the water temperature is in the middle of the guage before you boost at all, else you will have a shorter engine life.

[pdtaylor18]

Some engines can be as low as 6\'s all round and still last for a few more years.
Most Rx7 engines are blown when an import which is mapped for 100 Ron is then modified and thrashed on pitiful 95 Ron UK fuel.  
It is always best to run on the highest octane you can get or if not try some octane booster for safe measures but depends on whether your car is mapped for UK fuel or not, ie JDM or UK car.

[L18M]

thanks for the gd response. always learn something new.
the rex had a N370 ecu so i guess its for higher ron. this went faulty as it didnt spark the rear rotor so i had a uk spec edu pluged in n it works kinda fine apart from the lack of power below around 3k revs.

Some engines can be as low as 6\'s all round and still last for a few more years.
Most Rx7 engines are blown when an import which is mapped for 100 Ron is then modified and thrashed on pitiful 95 Ron UK fuel.  
It is always best to run on the highest octane you can get or if not try some octane booster for safe measures but depends on whether your car is mapped for UK fuel or not, ie JDM or UK car.