Quick question, what's the highest octane gas the stock ECU is designed to handle on the R56 MCS?

IIRC in some areas around the country they run gas as high as 98 octane (only 91 here in Cali with a few 100 octane pumps), I was wondering, can the car handle 100 octane w/o an ECU flash?

Just curious, thanks!

 

Quick answer: No.

 

Not to mention its difficult to find true unleaded over 98octane.

What's the application? Modding so that you always need above 91? Track day? Unless there's a reason you *need* a higher octane you're like just throwing extra money into the pump.

 

Why do you want it?

Higher Octane does not yeild higher power, it simply empties your wallet faster.

Unless you suffer pre-ignition, higher octane will do nothing for your performance. If you do suffer pre-ignition I'd wonder why...higher octane might make it go away but you should know where the issue came from. Is the ignition timing off or did you raise the compression. Have you boosted the supercharge SO much that you now suffer from pre-ignition? I've not heard of that with the commonly applied pullys used in GEN1 and don't know of a way to do it at all on a GEN2 turbo....

Remember higher octane fuel is actually HARDER to burn. It is required as compression increases because high compression creates so much heat that the fuel will ignite b4 the spark happens, yeilding knock. Higher octane keeps the fuel from pre-igniting b4 spark happens. Race engines running very high boost - and big american engines from the 60's era - run high compression and need the high octane. Our 69' Pontiac 400 cubic inch ran seriously high compression from stock and needed the expensive stuff. Not long after that came unleaded gas and compression went way down....in the name of economy. In those days when you could no longer get the recommended octane you either bought additives or backed off the timing to give the spark earlier and get rid of the knock...

 

As I understand it, the 98 Octane the engine was designed for is the European method of measuring this, that's different than the US way of measuring it. The equivalent in the US is 93 octane (or maybe 95).

Also the engine won't have any trouble with the extra octane will it? It just won't make any use of the extra capabilities.

 

Up to a certain point yes. Because the gas is harder to burn less fuel is burned each ignition cycle. This unburned fuel has to go somewhere and that's out the exhaust pipe. This could lead to carbon/gunk buildup in the exhaust system and more fuel in the oil.

Bottom line, unless the car is designed to run higher octane there really is no point.

The MINI is designed to run around 91 but can detune for lower. Around my neck of the woods Premium is 93 and I don't think anyone has seen any problems.

 

I have and do run a mix of 98 unleaded and 93 unleaded at the track and the ECU has actually raised me 1 psi of boost... 17.5psi. When I run straight 93 it only has a max boost of 15.5-16.5psi.... The only reason I started running 98 was because it was the only fuel without that 10% or less ethenol b.s. That was causing me to miss fire from 4k-5k RPM under full boost. As soon as I started running the mix of 98 unleaded race fuel all misfires went away and I started to run 1 psi higher on peak boost!! Stock ECU.

 

youre mini is not tuned for 98+. waste of $.

 

From what I have seen, the GEN2 is likely similar in programming to the GEN1. I have performed extensive data logging on the GEN1 ECU, and it will respond to higher octane fuel. Once the ECU hears a certain threshold of knock, sometimes inaudible to you in the car, it will pull timing. Sometimes this happens down low in the RPM band and the car will never recover to the upper timing maps by the time you hit redline. My bone stock 05 JCW would pull timing almost always. You could never reach the highest timing maps in the ECU unless you were using higher octane(than 91 in Cali) or other means. Most ECUs are similar in this way that there is some headroom in the timing maps for advancement.

As I said, I have not yet data logged the GEN2 ECU, but unless you are logging all of the OBD parameters and some other items on the engine you don't know what it is really doing. Now that I have somewhat figured out the programming of the GEN1 ECU, I can run upto 8 degrees more timing over what I was seeing stock even in 110 degree heat.

 

+1 what he said

 

I ran 100octane(unleaded obviously) before i got my Unichip retuned for that specific octane, and it definitely made more power and ran better and smoother, like what i get now all the time from my w/m injection.

 

Good question indeed.

The R53 ran an ignition timing program that basically kept advancing the timing until knock would occur. It would then pull a few degrees, and push advanced again until knock occured. This cycle would keep the timing pushed as far advanced as the engine setup would allow. If you were running a 19% pulley with a crappy intercooler on a hot day, you'd get significant timing retardation from having lots of knock. If that was the case, adding 100 octane, or even 104 octane unleaded would allow the engine to run full advance [per the ECU table] without knocking. This would give significant power advantage over lower octane fuel.

The R53's strategy is common for port-injection boosted setups, however I have yet to see any data that correlates that sort of strategy to the R56 MCS engine. TGDI [turbo gas direct injection] has such significantly better chemical quench and burn speed [from significantly better atomization, being quasi-homogeneous] that timing maps are massively different from port-injection engines. As such, all other operating conditions similar [like dynamic compression ratio, AFR, and temps], a TGDI engine won't benefit from markedly higher gasoline octane.

For example; a common R53 may have a 15% pulley, CAI, and cat-back exhaust. Under most conditions, it'll be operating in knock-retard mode with 93 octane fuel at the racetrack. This will end up being somewhere around 28° BTDC at 7k RPM. With 100 octane unleaded, that timing may bump up to 35° BTDC [just an approximation, don't nail me down for these exact figures, just going off memory here]. Now, an R56 MCS JCW Stage 1 will be running similar boost [about 14PSIg], however will be running ~9° BTDC timing advance at 6500 RPM. That's a huge difference in timing! This isn't cause for concern, but it does demonstrate exactly how revolutionarily quick the TGDI combusts compared to PFI. What's more, there's no sign of knock, so I'd imagine there's no knock retardation. Adding more timing to the TGDI may cause backfiring, but that's just speculation. I'll admit I don't have enough tuning experience with TGDI to say what is ideal, I'm just pointing out how different they are. From what I've datalogged to date, it appears more than 93 octane with 14PSIg is unnecessary with the R56 MCS.

Cheers,
Ryan

 

Ryan,

It sounds like you have more direct data that I but some of the discussions I've had with the guys across the pond lead me to believe there should be significant room for timing advance. That is unless the ECU is substantially locked into very, very safe amounts of timing.
My understanding is the (DI)ECU operates 180 degrees out from what we would consider normal. On the 53, and most cars, the ECU meters the amount of air you needed to make a certain amount of power, then sprays the appropriate amount of fuel. In the DI engines, a certain amount of air is entered, sometimes excess air, similar to a diesel, then the exact amount of fuel is sprayed for the amount of power desired. In part throttle application AFR's as high as 20 can be seen, from what I'm told. Under full throttle application, the AFR's will come down to levels we are used to seeing on most cars. Of course those high AFR's generate a massive amount of heat.
Some of these feats are accomplished by multiple sprays of fuel per injection cycle. (Next week I'm going to try to get some traces with a scope to log this.) These multiple sprays can help even out the air-fuel mixture and help prevent pre-ignition in the cylinder. The ECU can even spray fuel after the spark has initiated combustion in the chamber.
The end result of all this is that with all this heat and and controlling the excess air the car would seem to be screaming out for more octane to help fast part throttle transients, if not full throttle blasts. My guess would be there are still at least different timing maps for coolant temps and the IAT's the engine is seeing.

Then again, I could be wrong about all of this. I'll have to see what the data reveals.

 

For anyone interested, here is a cliff-notes version of the operating theory of the DI engine. It gets a bit more involved, but a very good read.

http://autospeed.com/cms/A_107830/article.html

 

Yes it can. Why wouldn't it the car is also sold in the EU where in most countries the only option is 90 octane or 100 octane. The only thing I'm not sure is if it can handle the German's 120 octane.

 

I can see there's a pretty wide range of opinion on this subject...

Does anyone have before and after dyno numbers?

 

As soon as I test the new water/alcohol kit for the 56 I'm sure the numbers will hit the board.

Straight octane I have nothing.

 

I'll be posting by dyno numbers from water/meth.