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Unread 07-23-2013, 08:22 PM   #1
Wasatchwk2
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Wk Grade of Gas

I know, I did read the sticky. It says the 5.7 is tuned for 89 and can run fine on 87, however, I was reviewing the manual and it says recommended for optimum preformance to use 91 octane.

So I was just wondering what everyone is using for their 5.7? I was planning on filling up with 87, I just wanted to be certian that this will not effect the engine in anyway.

Thank You,

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Unread 07-23-2013, 11:03 PM   #2
philculp
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I always put non-ethanol premium in. But the manual just says 89 or higher for optimum. The srt8 recommends 91 or higher for optimum.
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Unread 07-24-2013, 04:13 AM   #3
moonguy
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I always run 89 octane with my 5.7. The manual doesn't have 89 octane recommended for no reason. I also find it runs better also.
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Unread 07-24-2013, 07:33 AM   #4
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There is such a wide variety of fuel that premium one brand runs worse that regular of another.

Try to find the least ethanol content and use gas stations that do a lot of business, as the gas is fresher and has less chance to absorb moister.

The 5.7 can run nicely on 87 but if it detects any kind of pre-detonation event, it pulls massive amounts of timing to protect the engine. That seriously degrades performance and mileage for a short period of time... unless it happens more often.

The "hemi" head provide pretty good performance, but the wave front of 89 octane is petter for it.

There are so many production variances that one engine will run just fine on 87, while others will not.

My personal experience in ~40,000 miles is that I see fewer drivability quirks running good quality 89 octane. But not all 89 octane is the same. There are may here that are happy with 87 octane.

You may want to run 91 every once in awhile just for the cleaning additives.
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Unread 07-24-2013, 09:12 AM   #5
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Click on the link below to watch a 20 min video. CBC did a documentary on which gas is better. According to this video, 87 is good for most engines even if they say premium is required. Like Coldcase said, go to a good gas station to ensure you get what you pay for.

We have always put regular gas in my wife's Acura even though premium is recommended. She has close to 200,000 KMs and so far no problems.

http://www.cbc.ca/marketplace/episod...mpfiction.html
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Unread 07-24-2013, 09:48 AM   #6
Kev M
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Quote:
Originally Posted by ColdCase View Post
There is such a wide variety of fuel that You may want to run 91 every once in awhile just for the cleaning additives.
I've been told by multiple sources (some working on the chemistry side of the oil industry, specifically for Sunoco) over the years that this is a fallacy.

First reference I could find using google was:

http://chemistry.about.com/od/chemis...ine-to-buy.htm

Quote:
Gasoline Factors That Matter
The quality of gasoline and the additive package usually affect the rate of engine wear more than the octane rating. Basically what this means is that it matters more where you buy your gas than which grade you purchase.

Regular Unleaded Gasoline
The recommended gasoline for most cars is regular 87 octane. One common misconception is that higher octane gasoline contains more cleaning additives than lower octane gas. All octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against engine deposit build-up. In fact, using a gasoline with too high of an octane rating may cause damage to the emissions system.
Here's another good reference:

http://autorepair.about.com/od/engin...hoctanegas.htm

Quote:
Will Higher Octane Gasoline Clean Your Engine Better?
As a rule, high-octane gasoline does not outperform regular octane in preventing engine deposits from forming, in removing them, or in cleaning your car's engine. In fact, the U.S. Environmental Protection Agency requires that all octane grades of all brands of gasoline contain engine cleaning detergent additives to protect against the build-up of harmful levels of engine deposits during the expected life of your car.
Run the recommended octane to maximize power.

But don't run it under some mis-impression that it is "better" for your motor or fuel system.


EDIT - Boyvan - good link! saving that...
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Unread 07-24-2013, 09:57 AM   #7
StaticFX
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run 87. higher octane is for power only.

if you hear a "pinging" from the engine - then up the octane to the next level. Its rare though that you really need it.. (I had a 68 camaro that HAD to have high octane..)
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Unread 07-24-2013, 10:11 AM   #8
Wasatchwk2
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This is awsome information, thank you. So I now know the 89 is recommended but here in Utah we have 85, 87 and 91. I have read in other forums as well and they were mentioning that the higher elevation states have the lower grade because it does better with the higher altitude. And again thank you all for the information. I put 87 in last night and will listen for any pinging.
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Unread 07-24-2013, 10:19 AM   #9
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Air is less dense at high elevations. For normally aspirated cars this is going to reduce the amount of compression pressure that the fuel is subjected too because there is a smaller air/fuel charge in the first place. This means you will have less of a chance of compression ignition, which is one of the factors that higher octane is used to prevent.

Ergo, you can usually run a lower octane at altitude (which is why they usually have lower grades available than they do at sea level).
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Unread 07-24-2013, 12:55 PM   #10
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Quote:
Originally Posted by StaticFX View Post
run 87. higher octane is for power only.

if you hear a "pinging" from the engine - then up the octane to the next level. Its rare though that you really need it.. (I had a 68 camaro that HAD to have high octane..)
Thats old school, went out in the 90s. I had a '70 340 duster that would not run at all, let alone ping, on low octane fuel.

You will never hear pinging in a late model engine unless there is something drastically wrong. The engine computer automatically pulls timing before any detonation event. A driver won't hear of feel a thing, but the engine will run sub optimum, if you care.

I tune my off road vehicles as a hobby. The only way to see what the engine is doing is to put a monitor on it and look for tell tale events. The seat of the pants can easily be fooled.

There are numerous experts scattered about the web, many with agendas, some without. Perhaps my comment on high octane was miss understood. I was just trying to say that the only reason to use a high octane premium fuel once in awhile is perhaps for the cleaning additives. But as was noted, even the value of that is suspect.
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Unread 07-24-2013, 05:18 PM   #11
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Cold, I don't know that all modern cars have a knock sensor.

I know for certain that most motorcycles and marine engines don't, so it's still applicable.

Sooo the rule of thumb remains...use the octane recommended by the manufacturer unless you hear knocking, then increase octane level.

But yes, if equipped with a knock sensor you shouldn't hear it. Though if octane is low enough you might throw a code.
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Unread 07-25-2013, 05:53 AM   #12
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Quote:
Originally Posted by Kev M View Post

I know for certain that most motorcycles and marine engines don't, so it's still applicable.
All Fuel injected Harleys since... oh.. at least 2000 have pre-detonation sensors, and all HDs have had FI for a few years now. Thats a lot of motorcycles. My 1995 Ducati does.... just about any bike or vehicle with an engine computer and fuel injection senses pre-detonation in one way or another, usually not the old style knock sensors however. Waiting for the detonation is to late, damage done. There are many vehicles still out there with old style knock sensors, however.

Anyway the WK2 detects pre-detonation and adjust accordingly. You wouldn't know its working. It will throw a code only when the adjustments go out of range.
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Unread 07-25-2013, 06:55 AM   #13
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Quote:
Originally Posted by ColdCase View Post
Thats old school, went out in the 90s. I had a '70 340 duster that would not run at all, let alone ping, on low octane fuel.
ya'know.. now that you mention it, been a loooong time since i have heard that!
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Unread 07-25-2013, 08:44 AM   #14
Kev M
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Originally Posted by ColdCase View Post
All Fuel injected Harleys since... oh.. at least 2000 have pre-detonation sensors, and all HDs have had FI for a few years now. Thats a lot of motorcycles. My 1995 Ducati does.... just about any bike or vehicle with an engine computer and fuel injection senses pre-detonation in one way or another, usually not the old style knock sensors however. Waiting for the detonation is to late, damage done. There are many vehicles still out there with old style knock sensors, however.

Anyway the WK2 detects pre-detonation and adjust accordingly. You wouldn't know its working. It will throw a code only when the adjustments go out of range.
Uhhhhh NOPE, well maybe not a nope, but a bit of a qualified nope, you touched on it toward the end, but your statement is still too broad.

Harley does not use a piezoelectric knock sensor.

They DO, on some of their big twins, use a detonation logic where the ignition coil and ECM have some way of determining if it's going on. Some sort of feedback through the actual secondary ignition circuit (ION sensing, something to do with the ECM determining changes in resistance to the secondary ignition circuit that provide it info on knock).

But that logic is not enabled on EFI Sportsters (2007 to present).

EDIT - looks like you're right about when it appeared on Big Twins - I did some poking around and it looks like it debuted (supposedly first time used on any motorcycle - on the 2001 Softails with the Delphi EFI system)

I'd also have to check the schematic on our Ducati (696) but I can't remember off the top of my head if I've ever heard it ping.

I know most Moto Guzzis haven't used any system sensor based or ION based - as I've gotten all of th ones I've owned to ping (2000, 2006, 2013).

As for the WK2 I don't have a factory manual yet. EDIT I assume it uses a something more like ION sensing then? So IS there a code for prolonged pre-detonation detection/or long term timing retard - something showing the system is constantly active?

No matter - you are correct, that WHEN equipped with logic to deal with knocking it's unlikely the owner will hear it. We just disagree on the scope and breadth of what vehicles are so equipped. EDIT - but I could be wrong on the breadth now that I think about it. I guess if an ION based knock detection system may have become more common it would be harder to notice just from a wiring diagram, I guess you'd at least have to go through the trouble-codes, so you could be right, it could be much more common these days.
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Unread 07-25-2013, 11:07 AM   #15
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I think we have a failure to communicate. You seem to keep wrapping your head around a knock sensor an that was not what I was saying. Knock sensors are old school. While I did not mention knock sensor, I was refering to what is commonly called a predetonation sensor or prediction algorithm.. Nothing like a knock sensor. Harley users a what the call an ion sensor system.... That is also used in many new sportsters. There are sure a lot of big twins out there, most of the bikes I see on the road are HD big twins.....

Bottom line is that, for the WK2, listening for ping and hearing none gives you false information.
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