Whether higher octane by itself can raise horsepower in a stock car designed for lower octane is always a controversial subject. There are certainly those who swear it does, but I haven't seen a single one ever cough up a before/after dyno chart yet.

It all depends on how adaptive a car's ECU engine tuning is to octane. Engines that are nearer the pinging margins are more likely to have the ECU backing off the tuning when knock is sensed and a few engines are reported to be highly-adapative with the ECU keeping the engine on the verge of pinging all the time. But most probably run a fixed state of tune far enough away from pinging that more octane does nothing.

Car and Driver magazine ran a test a few years ago where they did dyno tests of several different cars running on regular and premium. Most showed no change in power. One did show a change, but the testing was not conclusive.

In general, I'm of the opinion that running extra octane in a car designed for less does nothing but drain your wallet faster. But I'm sure there are exceptions.

- Mark

 

One of them being the Mini turbocharged engine...

The non-believers could do this test, cause it's so easy...
Hook your car to the rollers. Measure your hp first with low octane fuel, then fill up with the super unleaded high octane gas and see for yourself the differences. Stock engine, mildly tuned, heavily tuned, it just doesn't matter. Gains are there regardless.

 

Your car doesn't know what octane it has in it plain and simple. The ECU monitors several sensors (Mass air flow, O2, etc) and uses what if statements in its program that references charts (timing, A/F, etc). It will not magically advance boost pressure or timing past a canned amount. The anti ping sensors is there to safe guard the engine against low octane fuel or conditions that will damage the engine such as over heating the engine that in turns causes ping. Lots of tuner use the ping sensor as a safe guard to run on the edge to get the max performance knowing it will save the engine if they start to detonate.

Your ECU is not a T1000 IA that can adapter and learn, it can't even rich-in up the mixture enough to compensate for a performance exhaust and intake. They are two ways to make more HP with higher octane fuel and that's turn up the boost or advance the timing (or both) and you need a tune to do that! No such thing as magic gas horsepower by itself or every one would be doing it!

 

True, but the claim being made is that even with the recommended 91 AKI fuel, a bone-stock 'S' engine will ping slightly under heavy load, causing the ECU to retard timing (thus limiting the maximum power you can get from the engine). Unless you can show that the engine will never ping with 91 AKI, it's not possible to discount the benefits of using fuel with a higher-than-recommended AKI rating.

That being said, I think it would be wasteful (for a street-driven car) to buy an entire tankful of 100 AKI gas just to maximize power for the short periods of time that the engine is under heavy load. I'd rather see some kind of setup where you have a smaller auxiliary tank with the high-octane stuff, and a pressure-operated valve that would switch the supply from the main tank to the auxiliary tank once boost reached a certain threshold.

 

just search on you tube, i have watched a UK video on it before and the higher the octane the more power they made on a dyno with stock cars.

 

I have a highly modified/tuned 09 JCW. I ran 100 octane for months. It won't make a difference unless you are tuned for it. Don't waste your time. Go straight to water/meth injection. A word of warning. If you play you may pay. Break a piston and it will cost you $5k-$10K.

Ray

 

If its so easy, then surely you've done it. Post up the results.

And BTW, I don't doubt that under some conditions (that can reasonably be assumed to occur now and then in street use), a stock turbo Mini engine which requires premium will make less power when running on regular. This is not the question. The question is whether going beyond the recommended premium (aka, race gas) does anything.

- Mark

 

The factory tune is set up to curb emissions getting as close as possible to the optimum AFR of 14.7/1. This is not enough fuel while the engine is under boost and that's why you ping sometimes with 91 octane (when the engine and outside temps are up). Its the AFR in the factory tune not the fuel (higher octane fuel will alter the AFR by very little and curbing this problem little to none).That's why you can make horsepower with just a tune, you don't need more boost or more octane. Boosted gas engines make the max horsepower around 10.5/1 under boost and under vacuum around 14.4/1-ish and there is no way they could meet emissions with those AFR's so they make compromises in performance.

I own Harley's and being air cooled motor the factory tunes close to 14.7/1 to meet emissions. I would ping on hot days under certain conditions. Air cooled motors like 13.5/1 for max cooling. After I put my new 2-1 exhaust and air cleaner on and tuned it no more ping under the harshest conditions with the same 91 octane fuel I always used.

Stop watching You Tube and read a book or something! :d

 

What you are saying is only partially correct. The ECU tries to keed the AFR at stoich (14.7) when idling or under low load for economy. However, as soon as you go under load or WOT it drops the AFR down to the 11-12 range. The ability to run exactly on stoich for peak efficiency when under low load, and rapidly go richer when under high load is one of the main advantages of the direct injection engine.

Robbo

 

I'm with ThePenl.

Go try it for yourselves. The OP asks a question, gets answered by numerous people well versed in the subject as it applies to the n14 R56 motor, and is refuted by people who are trying to apply "general knowledge".

The amount of self-adjustment in within our ECU is astonishing. In a high compression, relatively high boost, high inlet temp setup like the N14, which is controlled by a highly advanced ECU, you will see gains using 100 octane, its plain and simple. Go try it...

And sure you can get even greater gains with a tune specifically for it, but you will see gain even on stock tune. No its not cost effective to run 100-octane all the time, but the car does run beautifully on it...again go try for yourself.

 

Yea it tries to stay stoich as long as possible though...it's redic. I don't know if you've seen AFR graphs from a stock tune, but some of them are down right scary. And yes I know its DI...it can run leaner blah blah blah. lol

When you have control over the lambda map in the ECU you can get it to hold absolutely beautiful AFR curves. And the ECU self-adjusts amazingly to meet those AFR targets, based on the lambda sensor readings. I was running 100% methanol with my meth kit...and it would fully trim fuel back to reach my target AFR curve. Try that in any other non-lambda based car...you'll be running crazy rich. I had someone dyno my car when it was on 100% meth and the dyno operator/shop owner was convinced that I had been tuned for meth...but I never was. The amount of self-tuning/adjustment possible in that ECU is incredible.

 

Unless you are cranking the boost way up and seeing detonation on 93 fuel....running higher octane gas (100+) is not going to do a single thing for increasing power.

Octane is simply the stability rating of a fuel under compression (in simple terms). I don't know why some people associate higher octane with more power. Unless you motor "needs" more octane (you are getting detonation).....you will see no more power with higher octane fuel, you will probably see less.

 

Because...some motors need higher octane fuel more than others. Sure the N14 is rated to run on 91 octane...some reportedly run 87 and 89 ::cringe:: Doesn't mean it won't benefit from higher octane. I notice you drive an R53...the results of running 100 octane on an R53 are not nearly as dramatic as running it on an R56, for the reasons I've already explained. 100 octane in my GP does not do nearly as much as it did in my R56, again for the reasons I've already explained. Its low compression, comparatively low boost, and comparatively a lower tech ECU.

I give up in trying to convince people that it helps the N14 motor. Those that are curious....try it, you will like the results.

 

If you ever miss it, I'll trade you my R56 for your GP.

 

I'm just impressed and surprised that so many of you seem to be able to buy higher octane gas. The best I can do is run of the mill 91 octane with 10% corn syrup (ethynol). I think it may have something to do with the strict CA emissions requirements. Just about everything in CA has to do with emissions requirements (or requirements of some kind)!

 

It's been said time and again. The R56 does pretty incredible things. If your ECU is trying to do the best it can with whatever fuel, by increasing timing, lowering AFR, then it will keep pushing those boundaries no matter what fuel you use. That boundary is higher with a higher octane fuel. Yes there is a limit, but the R56 is more than capable with adapting for 100 octane. You don't even need a dyno, you can tell. Stock JCWs will ping in hot weather, mine's been doing it since I bought it, and so does everyone else's down here in Aus. R56s love higher octane

 

You definitely have to go looking for it. I was stationed in California from 2007-2009, and I found a Shell station in the San Jose area that had high-octane unleaded (I think it was either 98 or 100 AKI).

 

Ugly site but great info: http://www.davebarton.com/Unleaded_Racing_Fuel_in_SoCal

 

Ah yes, the infamous "butt dyno". Guaranteed to always show increases in power after any mod, in direct proportion to how much you've spent on it and how much the conventional wisdom is that it is the hot mod.

I've found the best way to make a car feel like it is faster is to wash it. It works every time.

- Mark

 

I am not trying to convince anyone. I have personal experience with what I state in this forum. If you like it or not, these statements are very true. It is up to you to decide if you want to take into account what is being written or not.
Either way, I won't bother.

What I don't like though, is mocking. Please don't do that. It is frustrating and does not add knowledge to this discussion.

Thank you...

 

I was thinking the same thing, open loop and closed loop programs. I have not dealt with the Mini ecu and was not sure if this system was the same as I have dealt with in honda tuner cars using hondata. Sounds just the same though.

 

I apologize for my tone, but stand on my point - the ability of drivers to objectively tell the difference in engine power by the "seat of their pants" is notoriously inaccurate.

- Mark

 

No it's not, your statement is inaccurate, I having worked in the racing/Motorsport industry for 28 years, and some of that time spent, as a professional racing driver, now drive only occasionally, I can tell you that the "butt dyno" or at the very least, "my butt" I can tell what's going on, regarding a change in power, whether this be from a fuel change, or a change in the fuel increment/timing maps, from a self adaptive ECU, or changes made on the fly.

Quite a lot of us "old school" engineer/drivers, drive by the seat of our pants, we feel every change the car makes, when your familiar with your vehicle, this becomes instinctively natural.

 

What you say is correct. I'm in the repair business and I can tell you most OBDII pcm's can make a +/- 30-50% fuel trim adjustment. I'm not overly impressed that the N14 ECU can adjust AFR when one adds meth injection. It's no different then a Ford Explorer PCM adjusting fuel trims for bad intake manifold gaskets. Of course on a direct injected engine there is much greater control because of the 5 wire O2 sensor.

I'm curious how far negative your fuel trims were with the 100 meth?? I'm gonna start making recordings next week.

Ray

 

So by your logic if I feel an increase in power after someone increased the boost pressure, then my own impressions of increased power are incorrect?

The brain is a lot smarter than a dyno bud. If I notice that the time taken to accelerate from 3000-6000rpm has vastly decreased, that's enough to satisfy me that there has been some power increase.

If I want to sell a part and people want to know how much power is made, then a dyno DELTA is all that I'm interested in.

I'm an engineer, and I'm the last person that has to be informed of the importance of data, but your statement that the butt dyno is irrelevant is ridiculous. A racecar driver doesn't say "I want 4 deg camber front, 2 deg rear, and 0 toe all round". The engineer sets the car up, the driver reports back, and changes are made. This is done via the butt dyno.

It all depends on how your butt dyno is calibrated. Mine is well calibrated and unbiased.