High Octane? - Nissan Forum
QR25 2.5L Engine Engine Discussion: 2002+ Sentra SE-R and SpecV

 
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post #1 of 11 Old Mar 4th, 2003, 11:53 AM Thread Starter
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Question High Octane?

Why is it that the Spec Vs factory recommended fuel is high octane (92 octane or higher) but the Altima with the same engine the factory only recommends regular 87 octane? Is it because of different transmissions or engine tuning? Engine tuning is the same on both cars right? 175hp 180lb torque right? Or is it just a marketing gimmick? You know, Altima buyers get better fuel effeciency, Spec V buyers get more power. I ask because I am going broke from paying $1.90 per gallon for premium. If I can save money buying regular without engine knocking, well then, I will. Thanks. Peace.

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post #2 of 11 Old Mar 4th, 2003, 09:43 PM
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I'm not sure but i think the spec v has a different compression ratio
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post #3 of 11 Old Mar 5th, 2003, 08:12 AM Thread Starter
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Question

If they had different compression ratios, wouldn't that affect the power output? They are rated the same. I think I'm going to try regular and see how it runs. Thanks.
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post #4 of 11 Old Mar 5th, 2003, 10:11 PM
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If it costs $1.90 for Premium, then how much less is Regular?

We are paying about $2.00 a gallon for Regular (87 octane) here in San Diego!

Thank goodness the old GA16DE doesn't seem to care about octane rating.

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post #5 of 11 Old Mar 5th, 2003, 10:22 PM
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Regular where I am is around $1.59...Sucks to be where you are.

Stay to the right and there will be more left.

http://members.cardomain.com/slvrspecv
http://www.b15nj.net/
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post #6 of 11 Old Mar 5th, 2003, 10:25 PM
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Well, with a 30cent difference, that's about 3 bucks a fill-up...i can see where your coming from. comes out to about 300 dollar difference or so a year.

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post #7 of 11 Old Mar 6th, 2003, 12:00 AM
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it has to do with the ignition timing. The QR25 in the spec v (as far as i know is rated 10hp better) has a more advanced timing.

-- 2002 SE-R Spec V
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post #8 of 11 Old Mar 6th, 2003, 12:03 AM
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FYI, gas milage will be seriously effected if you switch because there will be knocking in the engine and the car will retard the timing, thus putting more gas in the combustion chambers to prevent detination. Use the octaine level recomended in your manual. Also the diffrent octaines leave distinct traces in the motor, its possible that Nissan would void your warrenty if you blew your motor on low octaine. Like i said the ECU will compensate so blowing the motor shouldnt happen, but gas milage will go to shit.

-- 2002 SE-R Spec V
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post #9 of 11 Old Mar 6th, 2003, 12:09 AM
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That's the case with the KA24DE engine in the 240SX versus the engine in the Hardbody truck...timing and intake/exhaust system...I read a post before that someone stated that the 240SX required premium gasoline, whereas the truck could use regular unleaded gasoline. Same engine, different specs.

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post #10 of 11 Old Mar 6th, 2003, 08:08 AM Thread Starter
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I see what everyone is saying, but the two engines are rated at the same power output. If ignition timing is a couple of degrees less btdc (or in other words a little retarded like me) in the Altima that would effect the power output right? I don't know, I guess I will use premium just for the sake of warranty. Thanks all.
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post #11 of 11 Old Mar 6th, 2003, 08:49 AM
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Quote:
Originally posted by BlackoutSpecV
FYI, gas milage will be seriously effected if you switch because there will be knocking in the engine and the car will retard the timing, thus putting more gas in the combustion chambers to prevent detination.
There MAY be knocking but it won't necessarily happen. My mileage has stayed the same also using regular. The user manual 'recommends' the use of higher grade fuels. It doesn't state it is 'required' anywhere (At least not in the 2003 Spec manual). Also, knock only retards the timing, additional fuel is not added. The dealer won't know unless you tell them and it won't matter anyway as the manual or fuel filler door doesn't state that premium fuel is required. If it isn't required, they can't void your warranty for not using it.
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  Nissan Forum > Sentra, Pulsar, NX, B14 200SX > QR25 2.5L Engine

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