Testing the Octane theory

[Horton]

My boat has a 6 liter Ilmor MPI engine. I expect the difference between 87 octane fuel and 91 octane fuel to be negligible with my boat. Perhaps it will be the same magnitude as the difference between ropes or ZO settings.

 

So I do not have to literally drain the 91 out of the tank for the test I ran the tank down as far as I dared, and then added 5 gallons of 87. I then pulled 4 rides and then added another 5 gallons of 87. I currently have one more can of 87 to add when the tank it again pretty low. After running 15 gallons of 87 through the boat I will then fill it with 91.

 

The question is will I feel a difference that first ride with the 91? I do not know if I will feel a difference. My guess is maybe a little bit.

 

What I am hoping is that someone who runs at least mid 38 and has one of the three 6.2 DI engines (PCM, Malibu or Ilmor) will do the same experiment. I suspect that with those boats the difference will may be way more noticeable. I do not have one of those boats so I can do the experiment myself.

 

All you guys with 5.7s can rest easy. This is not about you.

 

[Kwoody51]

You should have had @rico fill it up with different octane so it would have been a true blind test :)

 

Seriously though will be interesting to see what you find out/ feel if anything.

[MichaelGoodman]

@Kwoody51 if he did that he might fall at the 5 ball each pass.

[LeonL]

@Horton it's my understanding that it may take some time (maybe a couple of hours run time) for the ECM to adjust back to full performance for the increased octane fuel. It won't be immediate. So I've heard.

[Horton]

@LeonL I think that may be true with some engines. In the case of the Ilmor in my ProStar I believe the change happens almost immediately. That is what MasterCraft r&d staff told me.

[RAWSki]

Too bad you are in Cali with only 91 vs 93 availability. Our E Rec fuel is generally rated at 90 but I have seen others that are lower.

[rockdog]

@Kwoody51 is right @horton it needs to be a blind test. You already have a preconceived idea of the outcome so you'll be looking for it. Not a solid test.

[Horton]

@rockdog it takes a number of cans of gas to flush out one version of the fuel and replace it with another version of the fuel. so it's really hard to do A/B testing.

 

I do a lot of this kind of crap with skis. If the first ride with 91 feels the same you pretty much got to trust me that with my boat it feels the same. Potentially my first ride with 91 will be behind @Rico's ProStar that is identical to mine. That way it will be pure 91. As stated above I expect with the Ilmor 6.0 the difference will be unforeseeable or negligible

 

I'm really hoping that somebody sees this and tries to the same thing with one of the direction injection 6.2 motors. I'm super curious the result with those motors.

[bigtex2011]

I will try it in my 6.2 malibu. I'm going to "try" to keep an open mind. As I said before, this is not a drag race so I don't think it will matter much. My guess is it matters more to the super Type A personality.

 

 

[Bruce_Butterfield]

My $ is on the placebo effect.

[Horton]

@bigtex2011 You're good enough skier that if there is a real difference in throttle response you'll feel it.

 

again what I did was I ran my tank as low as I dared and then put in a can of low octane. I then pulled about four rides which burns about five gallons and then I put in another can of low octane. The idea is to do that three times to get rid of as much high octane as possible. Ski behind it as you go through the process of running through the 15 gallons of low octane.

 

Then fill the tank with high octane, pull a few rides of tricks or a tube rides or some crap to clear out the system and then you ski and see if you can feel a difference.

 

If the difference is not substantial then octane really doesn't matter for that engine.

[ISP6ball]

I feel like there are potentially a lot of variables that could give you a false experience of the octane theory aside from the placebo effect.

 

It's probably still worth giving it the ol college try, but...

 

In between octane changes did you:

-Go to bed after too many bourbons

-Eat ice cream as your dinner

-Have a well balanced diet

-Wake up happy

-Wake up grumpy

-Toss and turn throughout the night

-Sleep 10 hours

-Wake up with the 'old man' aches

-Wake up with a great cup of coffee and a sunrise

-Not get the morning dump in

-Get an ear full from the spouse before walking out the door

-Stub your toe on the dock

-See an alligator swimming on the other side of the lake

-Find out you don't have to pay taxes anymore :smile:

 

I guess you get the point....

 

[The_MS]

This better not screw up the ? test

[Horton]

@ISP6ball is the difference is that small than we have the answer.

[ski6jones]

Have someone buy you 4 cans of each 87 and 91 and bring them to your dock. Keep them segregated and run your test. That way you won't know which fuel you're skiing with. Only the person who bought the gas will know. Tell what you feel then reveal the gas type. Blind test.

 

If @bigtex2011 does this test the big spray will reveal the answer.

[slow]

Placebo effect

[LeonL]

I would think that if you have the luxury of having 2 identical boats you would just ski with one on 87 and the other on 91, back to back.

[Horton]

@LeonL likely I will use identical boats. Ski last set w/87 then go ski the 91. I will have been skiing with the 87 for about 8 rides before moving back to the 91. After that many rides with the 87 if there is much difference with the 91 it should be obvious.

 

Those of you who are screaming for more scientific method are welcome to recreate the experiment yourselves. I'm doing the most practical version for myself.

 

[6balls]

Have not been able to tell any difference in any of the 500 plus HP cars I've owned in the last 10 years. I save the money and put in the 87. Maybe a few tenths at the track, but that could have been the speed I scrubbed in turn 2.

[Hucklefin]

I think the biggest issue with the octane debate is the level of misinformation about fuel in general on public forums, facebook, reddit, etc. Everyone seems to turn into a chemist as soon as octane starts being discussed. I can't help myself from laughing at what so many people think they know about it. I'm not an expert myself, but I know enough about it to tell easily when a person is completely full of it.

[skierjp]

@6balls I agree. In all the Corvettes I’ve owned it takes over 50 horsepower to actually feel any difference. No way a difference in Octane will equate to 50 hp!

In Florida we have 87,89,91,93 and 94 Octane. California highest octane is 91?

[Horton]

@skierjp can you feel bad driving?

[JackQ]

All ECU's make correct to knocking if experienced by lower octane fuel, if you have sufficient cylinder pressure to cause knocking (not likely to occur in slalom) within a few crank revolutions (less than 10-15m/s) I think you will find more correlation to the moon phases than octane.

[Jody_Seal]

@Horton This some funny sheet man!!

 

 

When we did this test I had a 5 gal remote fuel tank rigged up all inclusive with a return line. In line fuel flow meters

 

 

Ran back to back tests with reg 87, mid grade 89 and premium e free 91.

We used fuel ordered as select test fuel from a high level producer.

 

End of story there was no decernable difference at general skiing speeds.

Now where we seen Performance gains was at wot and the boat went faster by nearly a mph on ethanol free 91....

 

Slalom sustained rpms were monitored with a data acquisition break out box and fed into a laptop with a in-house acquisition program.

 

 

 

We also had a load measuring device in line of the

prop shaft. That gave a better reference to how much torque was generated and if there were any gains or loses between fuel blends.

Yes we also did some performance testing with winter blend fuels as well as utilizing this system for propeller testing.

 

I guess what i am saying Mr. Horton your method of testing is very unscientific and your test skiers have preconceived outcome do to what you tell them. ..

 

 

We also did vapor pressure testing with winter blends vs summer blends

[skierjp]

@Horton ???

[Horton]

@Jody_Seal here's what I know. guys that run at least six balls more than I do claim it makes a difference. I'm doing an impromptu admittedly not incredibly scientific test to see if I can feel any difference. as I stated at the beginning of the thread I don't think I'm going to perceive the difference but I've also been led to believe that the engine that I'm testing with is potentially the least critical. hopefully somebody will be inspired to do something more scientific.

 

I don't recall you ever publishing the results of the testing that you did. please tell us more. also do you think that as we span the years from carbureted all the way to direct inject is octane more or less important as the years go on?

[jjackkrash]

@Jody_Seal I am curious which engine did you run tests? The PCM 6.2L?

[oldjeep]

If you want a good test - top speed with 91 octane, top speed with 87. Assuming your pond is big enough to hit top speed.

[Jody_Seal]

@jjackkrash

No these tests were prior 6.2 prior 2016.

Engines we tested gt-40, python 502, 6 liters and Excalibur..

 

@Horton testing was done correct craft/nautique boats over a number of years. They won't divulge nor would they "publish" their findings.

Truly interesting as the engineer at the time was very much with true scientific testing procedures. Our test skiers were not even told what kind of tests they were skiing for..

 

@Horton get your self a diacom setup.... it has all the necessary components to run the tests you want to run. It will show fuel flow it will show rpm gains and you can graph and run 19 second scans.

It will show fuel injector pulse information. It will show voltage at all the sensors as well as the potentiometer.

If you want to do this kind of testing and report or "publish" your findings you will have more credibility then seat of the pants bull shit point you are trying now. Your also going to want to get and set up a 5 gal remote fuel situation where you can verify what your testing.

If your interested in flying out to the redneck riveria we have a 17 200 we can temp fit out for these tests.

You might want to have a handful of propellers.

Consistency in your testing is crucial..

Hope that helps.

 

 

[jjackkrash]

@Jody_Seal the reason I ask is that more than one person has told me that in some of the PCM 6.2L DI engines they can aggressively derate the HP with 87 more so than one might expect (and more so than would be explained by octane changes in general). I would personally not expect any significant HP change to the 6.0L.

 

I have never tested mine and didn't intend to, but now I am a little curious. Probably not curious enough to get off my ass and test however.

[Jody_Seal]

@jjackkrash

Pretty easy to find out. Hook it up to diacom or Ecom and go run tests. Both of those systems are capable to show any derate at or under the conditions you setup. At least get a handle on Hortons or whomever theory ..

[JackQ]

The critical parameter is to monitor spark advance under load, and if you can knock sensor activity. Premium fuel has no more energy to 87, only reduces the tenancy to detonation (knock) under high cylinder pressure. So IF (not likely) high load conditions (high cylinder pressure) the ECU detects the knocking and reduces spark advance until the detonation ceases, then increases, monitors for knock, are repeats every 10 m/s or so. Only when spark advanced is reduced is there ANY possibility of losing HP. If you observer throttle position in the course you will see that high loads are not occurring. You all are nuts

[Bruce_Butterfield]

Ahh, but the wild card - and I suspect the real culprit - is how the boat manufacturers "tweak" the ZO parameters for each boat/engine combination. That's where the black magic is.

 

For example, boat mfg A has a 6.2l 450Hp with ZO tuned to add x amount of fuel/air when it senses a drop in speed, vs a 6.2l that "really" has 400Hp with lower octane fuel still adding that amount of fuel/air. Is it different? Maybe. Noticable to the elite level skiers? Questionable.

 

If there is a difference - and I'm still very skeptical - the issue is with the ZO programing, not the octane that is the problem.

 

JMHO

 

For slalom skiers, bring back the 5.7. For the jumpers, lets pullout the stops and let Jody and DW build up a supercharged beast the big boys really want:)

 

Yep, this sport has gone fully anal retantive.

[bigtex2011]

@Bruce_Butterfield i miss the 5.7.

@ski6jones haha. my clydesdale type figure is good for something I guess

@Horton how do you even know when a Mastercraft is close to empty. did you use a broom handle. Half the time the gas gauge doesn't work. :)

gotcha on the list

[chrislandy]

run the test with a different skier than yourself, tell them and make all the motions that you've changed the fuel, but use the same... see what they say ;)

[Jody_Seal]

I would have to agree with Bruce as there are many speed control variants out there. Un like perfect pass where some of the gains were adjustable and were engine models and induction systems varied.

Basically we now have one induction system on the di engines and one induction system for 6.0.

Zero of gains are boat manufacturer installed however there are many individuals out in the field that have access to Ecom development software as well as zero off programing capabilities. A couple of these guys are not to proud to make personal changes to boats they will have to ski behind in competition.

 

@chrislandy you are spot on with the placebo testing. When utilizing skiers in boat performance testing information to them is very minimal.

Accounting of disposable materials must be (gasoline) maintained.

Documentation must be precise.

Repetition is a must.

 

@Bruce_Butterfield many wild cards in this testing game .

Water depth, wind Conditions , raw water cooling temp. boat weight with crew, humidity and ambient air Temps under

engine box Temps. Propeller consistency. Engine hours,( really don't want to test on a less then 50 hour boat or at least after complete engine break

in)

 

 

 

So one can see BS seat of the pants testing holds no water!!

[DW]

Testing for minor effects in a well controlled lab environment can be challenging, testing for minor effects out in an uncontrolled environment is really difficult and takes a lot of effort and discipline. In this case there are actually two uncontrolled environments that create a lot of white noise, the air and the water, not to mention two humans (driver/skier). Lots of variables to account for running this particular test as noted.

Several comments on the effect at WOT, given WOT is never part of the operating condition for this test it is irrelevant. Transient throttle reactions are what the test is trying to decipher.

[Jody_Seal]

@DW WOT Is always necessary for end analysis.

Can't calculate complete performance curves and sensor thresholds with out it. I would think with trying to identify derate with one of the scan tools available one could identify derate and or its affects on skiers.

And publish it!!

 

Besides who does not like blasting across the

water At WOT?

35 MPH I always like hearing the gulp of air and the click of the throttle plate at full open when the jump switch closes!!

 

[Vernon Reeve]

A popular youtube car guy that does lots of mechanic videos says to just see what the manual says to use. So what does the manual recommend? High end sport cars need higher octane according to the manual. Normal cars say 87 in the manual. I'm guessing boats are the same. If the manual says 87, you probably won't notice the difference if you put 91 in it. If the manual says 91, you probably will notice the difference if you put 87 in it because it actually needs 91.

[oldjeep]

Heck, my 2012 350ss 5.7 derates with 87 octane. That is why I say try the top speed test. I can hit 48mph with good 91 octane fuel. With 87 it just gets to 43.

[MDB1056]

Why not change 91 to 93? Broader spread. Better test

[Horton]

@MDB1056 can't get it here

[vtmecheng]

Did you test the fuel you got to see what the actual octane percentage is?

[OldboyII]

@JackQ You are right!

Caloric value of the fuel is not the same that detonation resistance (octane No). There is not direct dependance between them.

Moreover (theoretically) high octane fuel could be less powerfull comparing to lower octane.

[Inboardfix]

As is usual w/discussions on BOS the more I read the more I realize how little I know or how little I care to know. What I do know is I have a 6.2 and run 87 octane because I subjectively believe the ECM's compensation for the lower octane will not adversely affect performance to a degree it will be noticed by any skier I pull. It should be noted I doubt either of the Adams will be visiting my site or anyone else who is capable of running 41.

 

Also, I don't really care if using a lower octane at a tournament adversely affects skier's performance slightly as long as all skiers are pulled using the same fuel. Also, who wins is more important to me than the score attained to win.

 

Everything mentioned above is subjective and purely my opinion. It is not my place to tell anyone what fuel to use. Every boat owner should use what they feel is best for their situation. When I'm at the pump it comes down to do I want to pay $2.74 per gallon for 87 or $3.09 for 93. For the reasons stated above I go w/87. To put it in perspective of long term rather than at the pump on any given day, lets say your engine has 1500 hours and you average 4 gallons an hour (may be slightly better or worse depending on your engine and use). 6000 gallons used (1500 hours x 4) @ $2.74= $16440

6000 gallons used @ $3.09- $18540.00

 

So, over a 1500 hour period you spend $2100.00 more to use a high octane fuel. Numbers/totals will be different depending on regional fuel prices but my point is the amount saved using a lower octane fuel may or may not be a big deal. It depends on the skier/boat owner and their status in life financially as well as their individual cost/benefit analysis of using the higher or lower octane fuel.

[jjackkrash]

$2.74! Must be nice. 87 was over 4 bucks last night and they jacked my non-ethanol premium to $5.40.

[Jody_Seal]

I paid $4.21 per gal last week for 93 e-free for my lawn equipment.

I have a 09 with a cat 6.0 usually run midgrade through out the ski season. When it starts getting cold I fill it up with e-free mid or better grade for the layup time.

[Horton]

@Inboardfix @Jody_Seal what I know about the technical aspect of this conversation could fit in a thimble.

 

What I do know is that a few degrees of water temp makes a difference. A few thousandths of an inch of fin adjustment makes a difference. A few mph of head or tail wind makes a difference. One rope or another makes a difference.

 

Can I feel it? I am a little doubtful. I will do the final test today or tomorrow. Do I think skiers who run 39 behind current technology boats can feel the differences. I know a few who say they do. Not just the Adams.

 

Maybe it is all imagined but I am always unhappy when elete skiers claim something is true and all the “experts” definitively say it cannot be true.

 

[Horton]

Well I just got off the phone with my buddy Jeff who does some work for GM. I described the topic as – “a current DI 6.2 is at 3400 RPMs +/- and the ecm asks for another 100 revs. Would the octane impact how fast the 100 revs was delivered.”

 

Jeff called Bud Pennington who until recently worked at Chevy Performance - next gen Corvette development and such. Bud’s answer was unequivocally yes. Octane would impact how fast the motor could deliver another 100 RPM.

 

Can I feel it? That is the question. Can a skier at a longer line length feel it? Extremely doubtful. Can a skier who runs 39 or short feel it? I am inclined to say yes.

 

[skierjp]

@Horton So now what do we do about the 91 California compared to the 93 and 94 in most other states? I personally think the driver has more bearing then anything. Some are soft some are hard. Ropes would be the second most important variable.