petrol

[anthony]

what octane rating should i run in my rx7 type r? i was going to put in optimax only but would i need an octane booster at all combined?

what fuel do you guys run on ?

[nikp]

If it\'s an import that has not been mapped, then the jap cars are run on 100 RON fuel. This means that no fuel in the uk will be sufficient, and an octane booster will be required. Your best bet is Optimax with an octane booster put in there. It is possible to run it on just the optimax, but you will be in more danger of detonation.

[anthony]

anyone suggest any octane boosters that they have used?
Would i be better off just using the 99ron from tescos? or would it still be worth using octane booster?

how much does it cost for it to be rechipped for uk fuel?

[nikp]

To get it mapped for uk fuel, you\'ll have to get yourself a mappable ecu, like the Apexi (roughly £550) and then get it mapped (roughly £250-300). starting to look pricey now, aint it! But a mapping session will probably release more bhp too!

[anthony]

i think i\'ll fill up with optimax + octane booster and when the stations sell the new optimax premium (100ron) i wont even need to worry about the octane booster

rather than getting a new ecu

thanks for your replys tho

[james01uk]

buy the ecu anyway you wont believe the power difference ;-)

serious extra bhp
i got 293@wheels with apexi ecu and zorst

well worth the cash plus better for the car as you can get a commander and monitor what its doing ;-)

[gsb876]

Although currently you feel its cheaper to run octane booster its important that for longer life of the rotary you do get it mapped to run in this country.

Otherwise what might have been cheaper will end up costing more.

Gurj

[Bobfish]

ive got a jap car and it runs fine on optimax, although i havent monitored knock levels.

The car is a 1992 with 70k and running pretty much 6.0 compression on all 6 faces of both rotors.

Coolant seals gone though!

[tiger18]

This is really intresting,, when i first put my rx7 on the road i run it for months on normal unleaded (lol),, car seemed to drive fine (although im not one to give my car too much punishment),,, i didnt know that japanese fuel was 100RON,,,, that means i was really risking the life of my engine (shhhhiiittt,,, cost me £2500 to build),,,, For the last four months ive been running on esso super unleaded ,,(i think the octane rating on that is 96/97),,,, car seems to be ok,,,,but i think ill give that optimax a try,,,,can any experts shed any light on octane  rating and engine running.?

[nikp]

Normal super is 97 RON, and optimax is 98 RON - pretty close to what the japanese run.

[andrewrx7]

You could also have a read through the other thread that is running:

here

It has some interesting comments.

[andrewrx7]

can any experts shed any light on octane  rating and engine running.?

I\'m not an expert, but basically the octane rating is a level of resistance to detonation - the higher the value, the more resistant the fuel is to pre-ignition. It allows the fuel to burn in a controlled manner rather than too early and exploding. The shock from uncontrolled ignition can be very damaging to the seals.
This becomes more important when pushing the car - it is under far greater stress than if you just pottle around under light throttle. From what I understand, if detonation is detected, the ecu alters the timing to help prevent it - the car also generates less power if this happens. Therefore, if you use a higher octane fuel, the chances of detonation occuring is less, and the car can run more efficiently - the car may also feel that little bit smoother and have a touch more grunt at the top end.
I\'ve also come across comments, that say power is not necessarily linked to octane rating. A lower octane fuel may have a different hydrocarbon compostion, and yield more power than a high octane fuel. But, back to the comment above, it may provide more power, but in a controlled environment in the engine, you revert back to the detonation + timing issues.

Does that make sense?? Hope so! :yes

[anthony]

Although currently you feel its cheaper to run octane booster its important that for longer life of the rotary you do get it mapped to run in this country.

Otherwise what might have been cheaper will end up costing more.

Gurj

i can see what you mean, if you were running the car on track days and the like constantly, you are probably more prone to damaging the engine, but i wouldnt of thought a 98 rated fuel with octane booster on a 100ron designed set up would cause that much of a problem unless  it was constantly under heavy load.
£650 is nearly half way towards another engine rebuild
maybe if a second hand apexi comes up all mapped and everything it might be worth concidering for sure

[asp]

maybe if a second hand apexi comes up all mapped and everything it might be worth concidering for sure

but its not mapped to ur car then

[Bobfish]

I\'m not an expert, but basically the octane rating is a level of resistance to detonation - the higher the value, the more resistant the fuel is to pre-ignition. It allows the fuel to burn in a controlled manner rather than too early and exploding. The shock from uncontrolled ignition can be very damaging to the seals.
This becomes more important when pushing the car - it is under far greater stress than if you just pottle around under light throttle. From what I understand, if detonation is detected, the ecu alters the timing to help prevent it - the car also generates less power if this happens. Therefore, if you use a higher octane fuel, the chances of detonation occuring is less, and the car can run more efficiently - the car may also feel that little bit smoother and have a touch more grunt at the top end.
I\'ve also come across comments, that say power is not necessarily linked to octane rating. A lower octane fuel may have a different hydrocarbon compostion, and yield more power than a high octane fuel. But, back to the comment above, it may provide more power, but in a controlled environment in the engine, you revert back to the detonation + timing issues.

Does that make sense?? Hope so! :yes

This is pretty much spot on, although the stock ECU is very limited with what it can do with regards to "detecting" detonation.  The only thing that can detect det is a knock sensor.

Higher octane fuel provides less energy when burnt than a lower octane fuel. The ONLY reason your car may feel faster with higer octane fuel is beause the car runs a better ignition map. Lower octane fuel burns faster, so provides more energy. It also provides detonation however.

Hydrocarbon composition has nothing to do with the energy released by fuel, RON is a rating of how explosive the fuel is, period.

If your interested, this is measured by burning a given fuel in an engine with constant RPM, ignition timing etc and measuring the knock level.  They then blend another fuel of iso-octane (100 RON rating) and heptane (0 RON) and when they reach the same amount of knocking in the given conditions, the percentage of iso-octane to heptane gives the octane rating of the fuel.