Another ethanol question for Wayne

[LeeinAlabama]

I have a 300HPDI "2004" it is totally stock. Would it be better to use a mid or high grade w/ out ethanol than the correct low grade w/ ethanol ? Yall don't jump me if this has already been asked, Thanks !

[engineermike]

Without Ethanol is better, by far. If you can get mid or high octane with no Ethanol, you get the best of both worlds.

[BassManGuy]

Question about this: if the engine is made to run with 87 octane, and I start to use 89 or 93 octane in efforts to prevent ethanol running through the engine, will this change in octane affect the engine's performance by running higher octane fuel?

[engineermike]

Nope.

[hyperflow]

Its not really right to say it wont effect performence at all. The motor will be more throttle responsive and have a tad better performence with 87 oct over 91oct. Ethanol aside for peak performence you want to run lowest oct you can get away with without detonation.

[engineermike]

I don't want to get in a pissing match, but I have plenty of data indicating that 87 and 91/93 all make the same power as long as detonation doesn't exist. They both have the same BTU content (Diesel actually has a higher BTU content). The only reason to use 87 is to save money if you don't need the detonation resistance.

[GE Blazer]

Regular gas is a faster burn than premium. This is why you have to use high octane gas when you have higher compression. If I tried to burn regular 87 in mine, it would burn a piston fairly quick. the burn times are not the same.

[spider1]

Mike that may be true but in CARS if it is set up to run 87 then it will in most cases make more hp and get better fuel mileage with the 87 vs the 91. and the reverse is also true. Now talking outboard they are generally set up on the account of compression and timing only with the higher compression and more advanced timing the high the octane is required to stop detonation.

[BassManGuy]

Ok, so if I start putting 89 octane in my 200 HPDI all I will experience is poor gas mileage, less performance, and pay a little more for it. So, there is no real concern of running higher octane and doing harm to a stock engine?

[hyperflow]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by BassManGuy &raquo;</td></tr><tr><td class="quote">Ok, so if I start putting 89 octane in my 200 HPDI all I will experience is poor gas mileage, less performance, and pay a little more for it. So, there is no real concern of running higher octane and doing harm to a stock engine?</td></tr></table>

Its not the oct thats a concern its the ethenol, Also i think the ethanol thing is blown a bit out of perprotion, The amount thats in regular gas isnt to worrie imo. The merc guys have a bit more to worrie about because thoes XS are right on the edge of being lean, hpdi are rish. Thats my 10cents tho.

IMO the diffrence betwin 89 and 87 you will not notice in the dyno butt seat nor in fuel milege. I dont have much experience with outboard motors and diffrent oct but with 2stroke snowmobile racing i got a tone. I know the higher oct you go the slower your snowmobile will accelerate and lose of throttle responce. Fuel millege i couldnt tell yah, we only do 660 feet at a time

[engineermike]

Bassman, you won't lose mileage or performance when switching from 87 to 89.

Again, I don't want to get into a pissing match, so this will be my last post on the subject.

I'm in a pretty good position to know what I'm talking about here.

There is no significant difference in energy density, specific gravity, stoichiometric ratio, or flame front speed between 87 and 89 octane. That means that the same amount of fuel is injected, the same amount is required, the same amount makes it into the cylinder, it's ignited at the same time, the flame travels the same speed, and it releases the same amount of energy. The only difference is the autoignition characteristics, which don't play a part unless you get detonation.

As expected, every scientific test has shown no measureable difference in power or economy between these fuels. Some folks perceive a difference, but it can't be proven with any kind of data.

Now. . . the same argument doesn't hold true for Gasahols, race gas, Nitromethane, or Meth/Eth, because there ARE significant differences in energy density, specific gravity, stoichiometric ratio, and flame front speed.

Mike

[Wayne Worthy]

I'm staying out of this one with my opinion

[hooken203]

You will do no damage by using higher octane fuel. In every vehicle I have ever used I get better fuel economy by using premium fuel. Just try it next time you do a long drive check fuel economy using 87 then fill up with 91 or 92 you will get better MPG. My two stroke outboards have always ran more MPH using premium fuel. The only exception to this is my motorcycle I have seen it on a dyno make more HP on 87 than 92 but the difference is small. I have a waiting challenge on my SHO I am going to run 87 in it and compare it to 92 I will post the numbers and let you know. I am not an ethanol fan but having said that if it doen't sit for long periods I dont think it will cause any harm. Although alot of marine mechanic will blame every engine failure they can on it.

[ClaySlayer]

If you're running a tad too much pitch it can cause detonation so I could see where 91 might make a little difference or in the case of a car/truck if you flog it all the time or are always under load (heavy payload/trailer, or lot of hills) it could make a difference otherwise you're wasting your money unless the computer is flexible enough to recognize you're running higher octane fuel and advance the timing to take advantage of it... My 2-stroke Yammie when propped correctly runs best on 87. My vehicles run better on 89 or 91 but that's because the factory tune was changed by me to take advantage of it so I get more MPG making the additional cost a wash PLUS I have more power/better throttle response.

[LeeinAlabama]

Wayne I was hoping for your comment

[craigs06]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by LeeinAlabama &raquo;</td></tr><tr><td class="quote">Wayne I was hoping for your comment </td></tr></table>

Me as well. Let us have it, Wayne.

[SkipM]

Here's what I have heard for what its worth. Dealing with real gasoline: higher octane burns cooler thus less power if the eng doesnt need the higher octane. Now where it gets tricky: with the oxygenated crap modern fuels the higher octane can actually burn hotter than the lower octane fuel. So any comparisons or tests between fuels can easily be skewed because who knows what you are actually getting, even at the same station week after week.

[ClaySlayer]

just use Marine Sta-Bil or a similar product and enjoy the boat while running the required octane called out in the manual. I too think this is getting blown out of proportion... There is no one correct answer as there are just too many different boat/motor/prop combos out there. If you want, try a tank of each one under similar weather conditions and see what happens...you won't hurt anything as long as you're running the min required octane.

[dalec1]

This is a good subject and I have a question.
I run higher compression heads (maybe to high) and have heard that with the ethanal based fuel I can get away with this because of the alcohol (same as dragsters running alcohol/methane, etc) I have recently found a fuel station about 25 miles for me that sells 87/89/93 octane NON-ethanol fuel. I would love to try the 93 octane that they sell but wonder if it will be to much?
Also, for those of you that want to run non ethanol fuel with non carburated engines it may take a tank or 3 of fuel for you computers to adjust to the new fuel before you start getting the extra performance, same with a car/truck. At least that is what I have read and I do not hold a degree in anything!! LOL

Wayne? Engineer guy? Gear heads?Thoughts?


Modified by dalec1 at 2:52 PM 4/28/2011

[mullamaster]

The biggest variable in all this is whether or not the ECU is "closed loop". The comparison between cars running higher octane and noticing a difference is moot because 99.9% of EFI cars are closed loop. As far as I know the HPDI is open loop.