Compression Ratio vs Octane?
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davidpingu
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Have a look at the compression ratio of the fd2. These run higher compression and are perfectly fine on UK fuel. Why or how that is the case I don't really know but it works.
beppe786
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if i had a choice i would put an extra thick head gasket on lower the compression so i could run more boost safely12T said:Not completely true. You can have a high compression ratio on supercharged cars also diesels run high compression most of them are boosted now days
Back to the subject can i run 13:1cr 98/99 octane or would 12.5:1cr be the safest for our fuel rating?
Shortstuff
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I have heard many rumours we are getting 103 Octane fuel at Shell Garages in the UK soon? Therefore you could go higher?
davidpingu
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Pretty sure shell is 99 now too Beppe.
You can't really use diesel compression as an example either as it's apples and pears. Combustion process for a diesel is completely different and due to the fuel being much less volatile it has to be compressed further.
There must be some margin in it for the k20 in the FD2 to be higher. I haven't heard of any FD2 owners suffering from pre det nor has anyone running a dc5 on 95 octane so there is some degree of tolerance obviously. I just don't think anyone has really experimented as it's an expensive way of gaining a little more response. Spoon rebuilt k20s run higher compression again, check out the spoon FD2 block on nengun. As far as I know, nobody has run it in the UK.
There are probably adjustments that could be made via Kpro to further capitalise on higher compression too as I think I read that advancing timing slightly can reduce pre det associated with running more compression. That's as much as I know though. The reason is most consider it as being little gain for the money you'd throw in to it.
You can't really use diesel compression as an example either as it's apples and pears. Combustion process for a diesel is completely different and due to the fuel being much less volatile it has to be compressed further.
There must be some margin in it for the k20 in the FD2 to be higher. I haven't heard of any FD2 owners suffering from pre det nor has anyone running a dc5 on 95 octane so there is some degree of tolerance obviously. I just don't think anyone has really experimented as it's an expensive way of gaining a little more response. Spoon rebuilt k20s run higher compression again, check out the spoon FD2 block on nengun. As far as I know, nobody has run it in the UK.
There are probably adjustments that could be made via Kpro to further capitalise on higher compression too as I think I read that advancing timing slightly can reduce pre det associated with running more compression. That's as much as I know though. The reason is most consider it as being little gain for the money you'd throw in to it.
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Don't forget if you change thickness of head gasket you will reduce compression 
As for shell octane. The government are going to enforce the use of ethanol based fuel now which has a higher octane rating so the 103 your referring to will be an E rated fuel. I think E85 is around RON105
Tesco momentum 99 is E10 so 10% ethanol which is how they raise from 95 to 99
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As for shell octane. The government are going to enforce the use of ethanol based fuel now which has a higher octane rating so the 103 your referring to will be an E rated fuel. I think E85 is around RON105
Tesco momentum 99 is E10 so 10% ethanol which is how they raise from 95 to 99
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integraleo
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Standard ecu on dc5 and dc2 will retard timing if knock is detected which will reduce power but not cause any damage.same will apply to fd2 which is why no one is complaining of any issues. They just won't make factory figures on a dyno with lower rated fuel.
Rom
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As Dave said, forget diesel as a comparison.
They rev lower, because all the parts are heavier. This is needed to handle the compression, and pressure / force.
Diesels have run upwards of 20:1 for years.
They work so differently. They can run higher ratios, as fuel is added after the comprresion cycle, this is why they dont pre det. The fuel is added to an already compressed cylinder, at pressures up to, and around 1800 bar. This highly atomised fuel, combusts when it mixes with the compressed (hot thats what ignites it) cylinder. They also have multiple injections per cycle normally. Pilot 1, Pilot 2, then main injection of fuel.
They also have 'swirl pots' 'bowls' whatever you want to call them, in the top of the pistons, another reason they have to be much stronger.
Anyway, ill stop boring everyone now
They rev lower, because all the parts are heavier. This is needed to handle the compression, and pressure / force.
Diesels have run upwards of 20:1 for years.
They work so differently. They can run higher ratios, as fuel is added after the comprresion cycle, this is why they dont pre det. The fuel is added to an already compressed cylinder, at pressures up to, and around 1800 bar. This highly atomised fuel, combusts when it mixes with the compressed (hot thats what ignites it) cylinder. They also have multiple injections per cycle normally. Pilot 1, Pilot 2, then main injection of fuel.
They also have 'swirl pots' 'bowls' whatever you want to call them, in the top of the pistons, another reason they have to be much stronger.
Anyway, ill stop boring everyone now
pulpmelon_r
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Why? What is your goal?12T said:
Static compression alone wont tell you if you will see pre-ignition detonation on a given octane fuel.
Crazylegs
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On my old 16v non vtec crx you could advance the timing on the D series block a tad to give slightly improved performance. I didn't do it as I was concerned about it detonating but supposedly it could be done as the D series 1.6 was a low compression engine, hence why it was good for boosting. I don't know if I've got that right, you could either advance or retard the ignition somewhat, one of the two. Not that this has any relation to this subject ha ha!
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Rom
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Whats the goal ?
A stroker kit is a lot different to pistons. If your keeping same displacement, pistons would be stronger allowing boost, and can also alter comp ratio. Theres little reason to change them unless your boring the cylinder, or boosting, or building a race engine.
A stroker kit will increase the displacement more than boring would. But would come with pistons anyway.
As momma always says....aint no replacement for displacement!
A stroker kit is a lot different to pistons. If your keeping same displacement, pistons would be stronger allowing boost, and can also alter comp ratio. Theres little reason to change them unless your boring the cylinder, or boosting, or building a race engine.
A stroker kit will increase the displacement more than boring would. But would come with pistons anyway.
As momma always says....aint no replacement for displacement!
pulpmelon_r
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OK12T said:
I'm just going to assume its a NASP daily use road car, you have no plans for racing and that you are using pump fuel for this reason.
In which case 12.5:1 static CR
