101 octane?

[tellreded]

Lucas oils has an illegal 7 octane level booster. That plus Petro Canada 94 would give me 101 octane. So my question is would this blow up my car? It's got just under 50000 kms on the engine, 144000 on the rest. I feel like it's be kinda dumb, but I wanna see what kind of speed I could get out of 101 octane.

[gjm120]

I don't think much more. The N52 (like many motors) effectively adjusts compression ratio by altering ignition timing. I think the N52 is 11:1 and won't go above that as that is the piston upstroke limit.

Also kind of doubt 7 pt boost without TEL.

awaiting corrections.....

[02Pilot]

Compression ratio is fixed by crankshaft stroke, deck height, and combustion chamber dimensions. The DME alters ignition timing based on pre-ignition as detected by knock sensors; pre-ignition, or knocking, is impacted by the octane rating of the fuel.

Octane is frequently misunderstood. It is only a measure of the resistance of the fuel to pre-ignition, i.e., higher octane fuels are more resistant to ignition. This allows higher compression and cylinder temps to be utilized to increase specific output. All things being equal, octane by itself has no impact on power.

[MightyMouseTech]

Originally Posted by gjm120

I don't think much more. The N52 (like many motors) effectively adjusts compression ratio by altering ignition timing. I think the N52 is 11:1 and won't go above that as that is the piston upstroke limit.

Also kind of doubt 7 pt boost without TEL.

awaiting corrections.....

Uh, you can't change the compression ratio.

As for OP, it won't make the slightest difference except removing cash from your wallet.

[gjm120]

I said effectively changes compression ratio with ignition timing, ie not firing at TDC

[MightyMouseTech]

Originally Posted by gjm120

I said effectively changes compression ratio with ignition timing, ie not firing at TDC

No engine ever fires at TDC.

[gjm120]

Originally Posted by MightyMouseTech

No engine ever fires at TDC.

Ok - so fires further advanced or retarded from TDC. Is that correct now?

[02Pilot]

Originally Posted by gjm120

Ok - so fires further advanced or retarded from TDC. Is that correct now?

The compression ratio is fixed. It is not altered, effectively or otherwise. Altering ignition timing changes when the fuel-air mixture is ignited and thus the amount of force imparted on the piston on the downstroke.

To the OP, the simple way to see what - if anything - it's doing is to dump it in and monitor the total timing advance while running at WOT, obviously after doing a control run without it. Any other method is speculative and pointless.

[gjm120]

Originally Posted by 02Pilot

The compression ratio is fixed. It is not altered, effectively or otherwise. Altering ignition timing changes when the fuel-air mixture is ignited and thus the amount of force imparted on the piston on the downstroke.

To the OP, the simple way to see what - if anything - it's doing is to dump it in and monitor the total timing advance while running at WOT, obviously after doing a control run without it. Any other method is speculative and pointless.

Lower octane fuel causes the knock sensor to retard ignition. This causes more of the combustion to happen on the down stroke (when the combustion chamber is larger). To me this is effectively changing compression ratio. Maybe just semantics.

Not trying to be a pain, just want to understand. Once long ago I learned how to test octane on both a research and motor index engines. And I think ,back then at least, you adjusted the combustion chamber mechanically after running the reference fuel iso-octane.

[02Pilot]

OK, let's be clear about this. It may seem like semantics, but it's not. There are two types of compression ratios: static and dynamic. Static is the basic one that most people refer to, and is simply the calculated ratio between minimum and maximum cylinder volume. Dynamic compression is calculated from when the intake valves close rather than the bottom of the stroke, and may vary if the engine in question has variable cam timing.

Ignition timing has nothing to do with it. Compression is about the volume of the cylinder and how much the gases in it are squeezed. When they are ignited, or indeed if they are ignited at all, is immaterial.

[gjm120]

Originally Posted by 02Pilot

OK, let's be clear about this. It may seem like semantics, but it's not. There are two types of compression ratios: static and dynamic. Static is the basic one that most people refer to, and is simply the calculated ratio between minimum and maximum cylinder volume. Dynamic compression is calculated from when the intake valves close rather than the bottom of the stroke, and may vary if the engine in question has variable cam timing.

Ignition timing has nothing to do with it. Compression is about the volume of the cylinder and how much the gases in it are squeezed. When they are ignited, or indeed if they are ignited at all, is immaterial.

Understand what you're saying and thanks for the explanation.

Maybe if instead of "effectively" I said it makes the engine "sort of act like" it has a lower compression ratio

[desertman123]

Originally Posted by MightyMouseTech

Uh, you can't change the compression ratio.

As for OP, it won't make the slightest difference except removing cash from your wallet.

Tell that to Infiniti.

Also just advance your ignition timing until you hear knock, then back it off 1°

[The Wind Breezes]

Long story short you would need to tune the car to see even marginal gains. The ECU won't make more power with race fuel thru "adaptation" it's tuned so conservatively it won't even take full advantage of 93 octane...though not like there's much on the table there lol. Also, use a real race fuel like VP or sunoco if you want high octane but don't run leaded it will foul your cat fast and your o2 sensors a little more slowly. Also, you bought the wrong car if you want to go fast (or more likely, your PARENTS did), because the N54 / N55 135 are now a dime a dozen, not really any more maintenance intensive than the N52 especially in the case of the N55 and they make tons more power both stock and with a easy reflash. Just saying, since you brought up this idea of wanting to go faster by means of a pretty ghetto method.

Originally Posted by desertman123

Also just advance your ignition timing until you hear knock, then back it off 1°

Something I'm sure the OP will get right to doing, lol.

[MightyMouseTech]

Originally Posted by desertman123

Tell that to Infiniti.

Also just advance your ignition timing until you hear knock, then back it off 1°

Well, SAAB did it first.