Gasoline Octane

[riot]

I just bought a 1992 240sx SE.  The guy never told me what kind of gas he put in it and I noticed on the gas door it said "user premium for maximum performance".  I decided that since I probably wont be worrying about "performance" on this motor I'll just use 87.  I've been using 87 ever since (had the car for a month)...and it feels exactly the same.

Now...is it me or is this motor naturally SLOW.  Maybe its because I'm not using premium or maybe its because Im used to a high revving honda...but I feel that this motor is fucking insanely slow.  After 5,000 rpms it just totally levels out and doesnt accelerate anymore.  Like I stated in another thread...it feels like the clutch slips from 5k to redline...but I've been told "thats just how KAs are".  

Comments?

[sykikchimp]

octane does matter somewhat..  but I think there must be something wrong with your car..  My car accelerates Real hard at about 5400 rpm.  feels almost like v-tec kicking in.. I would perform a good tune-up on it.  Will probably help more than you think.

[boosteds14]

like with my car, if i run less then 93 octane at 15psi i will have detonation.

i usually run 94 octane for about up to 18psi.
110 octane for high boost like 25psi

[transient]

I've been noticing a little bit of knock at 87 octane, so I just filled up with 89, and it seems to be doing better. I've got intake and exhaust, are you modded at all? Mine ran fine on 87 when it was stock.

[riot]

The KA is BONE stock...and that is how it will stay until I swap.  I deffinitely don't plan on anything at all.  I purchased the car from an 80 year old man who has had it for 10 years.  He kept really good care of it and had all of the paper work.  He had most regular maintenance done, etc.

I still think that I am just too use to a high revving honda motor. &nbsp; <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/huh.gif" border="0" valign="absmiddle" alt=':huh:'>

-ryan

[MorganS13]

i drive my car back to back with my sisters 98 Civic EX and honestly my car feels like a beast compared to that thing... above 4k to about 6k my car has an almost V-tec like power surge, its not as noticable since i got a tuneup but its definitely still there. &nbsp;i think u need to get your engine checked out or a tune-up, it can do wonders &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'>

[riot]

yeah, I'm guessing I'm due for an oil change and deffinetly a new filter as it looks to be very dirty. &nbsp;What else could I do? &nbsp;Fuel filter...? &nbsp;Anything else?

-ryan

[wherezmytofu]

octane is only and only for detonation perposes...the ka24de have higher compression sop u need higher octane....same for turbo...ther eis no extra hp from gas alone &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/cool.gif" border="0" valign="absmiddle" alt=':cool:'>

[Yosho]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (riot @ June 12 2002,2:41)</td></tr><tr><td id="QUOTE">yeah, I'm guessing I'm due for an oil change and deffinetly a new filter as it looks to be very dirty. What else could I do? Fuel filter...? Anything else?

-ryan</td></tr></table><span id='postcolor'>
Plugs, Wires, Cap, and Rotor. &nbsp;Sounds like you might not be getting a full burn in the higher RPM range. &nbsp;Try those in addition to the oil change and fuel filter.

As far as octane... yes it's important, but probably not why you think. &nbsp;Higher Octane is actually less explosive than lower octane gas. &nbsp;The higher the octane the more additives are used to retard the ignition point. &nbsp;The reason why higher performance motors need higher octane gas is so they don't have premature detonation. &nbsp;Think of it this way... we all know how an engine works right? &nbsp;Fuel and air are compressed and then ignited by a spark. &nbsp;If you use too low of an octane gas, that mixture will ignite too soon... that's the knocking sound you hear. &nbsp;Now, your ECU will automatically retard the timing to a certain degree to compensate for this... but your still loosing power and it usually can't compensate enough (again, that pinging/knocking sound). &nbsp;

High octane is critical on any type of FI engine as it's having to mix even more fuel and air. &nbsp;This is why in Japan they're able to get such high performance out of the FI engines.

[HippoSleek]

Anyone know if the knock sensor program in the ECU maintains retarded timing after repeated knocking?

What I'm getting at is that sometimes a motor learn to accept running like sh!t. &nbsp;If that becomes part of closed loop operation, it requires an ECU reset to regain the benefits.

I'd say a tune up may be in order (and you are definately going to have to get used to power ENDING at 5500, not beginning), but I would try running a couple tanks of premium, then resetting the ECU and see if the knock sensor ECU program is involved. &nbsp;Can't hurt.

[riot]

Well, I changed my oil and air filter yesterday. &nbsp;No need for the fuel filter...it was just swapped 10k miles ago along with other regular maintenance. &nbsp;I only was able to drain 2 qts and the oil was somewhat thick. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/crazy.gif" border="0" valign="absmiddle" alt=':crazy:'> &nbsp; I replaced it with 4 qts of 10w30 Castrol GTX. &nbsp;A new FRAM air and oil filter was added as well. &nbsp;The old air filter was fucking NASTY!

The car feels decent...Im sure its just all in my head...like I said...Im not used to low end torque...Im used to hop end hp...its a different ball game. <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/eh.gif" border="0" valign="absmiddle" alt=':eh:'> &nbsp;I'm sure I'll get used to it in good time! &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/lookaround.gif" border="0" valign="absmiddle" alt=':look:'>

-ryan

[pete north]

Hippo,

Yes the ECU retards timing after knocking.

If you wack your block with the handle of a screwdriver while the car is running you will actually be able to hear it retard itself.

I'd say the premium is worth it. Not only do you get better performance and usually better mileage, its better for your engine and fuel system because of the low parrafinic compound content (parrafins are refined out in higher grades of fuel).

[camppain]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (HippoSleek @ June 14 2002,04:17)</td></tr><tr><td id="QUOTE">Anyone know if the knock sensor program in the ECU maintains retarded timing after repeated knocking?

What I'm getting at is that sometimes a motor learn to accept running like sh!t. If that becomes part of closed loop operation, it requires an ECU reset to regain the benefits.

I'd say a tune up may be in order (and you are definately going to have to get used to power ENDING at 5500, not beginning), but I would try running a couple tanks of premium, then resetting the ECU and see if the knock sensor ECU program is involved. Can't hurt.</td></tr></table><span id='postcolor'>
and for some reason nissan decided that if your knock sensor goes bad or senss something wrong it wont trip a dtc. so thats something you find out if yuour checking on another code.

and yosho is pretty correct in how he explained higher octane is needed.

also if you advance your timing you will definately need higer octane due to your spark firing sooner(not a word)

[transient]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (riot @ June 14 2002,10:45)</td></tr><tr><td id="QUOTE">A new FRAM air and oil filter was added as well.</td></tr></table><span id='postcolor'>
Just for future reference, it's a good idea to stay away from Fram. They make some of the crappiest filters you can buy, but keep their sales up with a massive marketing campain. Get Mobil-1 oil filters, and if you don't want to get an intake, save up for a K&N drop-in filter. It's worth it because you won't have to replace your filter every 3000 miles. You'll end up saving money in the long run.

[riot]

FRAM is a reasonably priced filter (for both air and oil). I was considering a K&N drop in flat filter, but man...I don't need that, I am NOT going to be performing any kinds of performance modifications to this motor. And as far as oil filters go...I know MANY people who use FRAM and they don't complain one bit.

Until I see some hard evidence of a lot of people having problems with FRAM filters,...I think Im going to stick with it. &nbsp;But I am very open to proof otherwise.

And for the record, the car does feel MUCH better with the new air filter and oil change. I think it may have free'd up a few ponies that the old clogged filter was supressing.

good times!

-ryan

[KAMRAN]

i also have a stock KA..

what octane gas should i run? right now im runing 94 octane (highest we can get here) because i herd that the manual says 93... and 94 is better than 92... so... what do u guys suggest?

[240 2NR]

Please read the other forums before making a comment like "94 is better than 91." &nbsp;If your were running a boosted SR it would be, but a stock KA24DE calls for 91. &nbsp;Unless you advance the timing to compensate you are wasting your money by buying 94 if you think it's "better". &nbsp;Octane rating is a measure of the fuel's resistance to burn, higher number, slower burn. &nbsp;The fact that premium gas may be more expensive, more refined, or cleaner is not a direct result of having a higher octane number and it does not mean it is going to be better for your car. &nbsp;Now should you raise compression, add a turbo, or advance your timing, or not have 91, 92, or 93 available, then 94 would be a wise choice. &nbsp;I'm forced to use 93 since the next lowest grade is 89 in my area. &nbsp;

As a side note, Japanese gas is measured using a different formula. &nbsp;If it were done like it is in the States, it would only be a point or two higher and not 100. &nbsp;It is better, but not by much.

[Yosho]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (camppain @ June 14 2002,10:37)</td></tr><tr><td id="QUOTE">and yosho is pretty correct in how he explained higher octane is needed.</td></tr></table><span id='postcolor'>
There's more going on than that... but that's about the best I could do to simplify it. &nbsp; <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/hehe.gif" border="0" valign="absmiddle" alt=':hehe:'>

[Yosho]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (riot @ June 14 2002,2:59)</td></tr><tr><td id="QUOTE">FRAM is a reasonably priced filter (for both air and oil). I was considering a K&N drop in flat filter, but man...I don't need that, I am NOT going to be performing any kinds of performance modifications to this motor. And as far as oil filters go...I know MANY people who use FRAM and they don't complain one bit.

Until I see some hard evidence of a lot of people having problems with FRAM filters,...I think Im going to stick with it. But I am very open to proof otherwise.

And for the record, the car does feel MUCH better with the new air filter and oil change. I think it may have free'd up a few ponies that the old clogged filter was supressing.

good times!

-ryan</td></tr></table><span id='postcolor'>
Fram filters aren't made that well according to the studies I've read online. &nbsp;There are several out there where they test the flow characteristics of the filters... measuring what size particles are able to pass through the filter. &nbsp;In most of those studies they also cut open unused filters and examine the construction. &nbsp;Fram is always towards the bottom. &nbsp;

The 3 best typically available filters in my area are the Purolator Pure One (not the normal purolator), the Mobil 1, the Bosch, and of course, OEM Nissan filters.

I used to have a bunch of links about this, but lost them last time my computer crashed. &nbsp;Here's a few I quickly found on the web for you to read. &nbsp;I'm sure you can find more if you're still interested...

http://www.frankhunt.com/FRANK....an.html (http://www.frankhunt.com/FRANK/corvette/articles/oilfilterstudy/oilfilterstudy-german.html)

http://www.ntpog.org/reviews/filters/filters.shtml

http://minimopar.net/oilfilterstudy-german.html

[Griffon2k]

I agree with the other guys on this higher octane does not equate necessarily to higher hp, but it does a great job with engine performance. When i first got my s13, i quickly exchanged the air filter for a K&N high flow flat filter, put in some Ngk Iridium IX plugs and wires, changed out the old oil for some good old Mobil 1 5W and added a crucial K&N oil filter. Sure, it may not sound like much, but performance wise the car sure as hell ran a whole lot better, and it will continue to until i finally put in the SR20(still perfecting that in the shop). Riot, I know you may not be interested in doing anything to that engine or plan on keeping it, but I would suggest trying some of the same maintenance mods as i stated above, feel the change in the KA's performance. There is a lot of untapped potential in that engine, and once I pull mine out for the swap, I plan on bulletproofing it, port and polishing it and the turbocharging it just to find out what it can do. Then I plan to plant it into another s13 to see how it can hang with my SR20...Sounds like fun don't it?

[pete north]

Just a small correction, and a bit of an explanation about different fuel grades:

Octane is acutally a measure of a fuel's resistance to auto-ignite under pressure, not it's resistance to burn.

It is true that if you're buying for extra octane it is a waste of money. &nbsp;However, you will get better fuel economy because premium gasoline has a higher heating value. &nbsp;Premium gasolines are indeed much cleaner because they would be made primarily out of reformate and alkylate. &nbsp;Reformate is a very clean hydrocarbon containing aromatic rings (such as toluene). &nbsp;Alkylate contains mostly iso-octane (which burns very cleanly). &nbsp;Regular fuel grades (and mid-grades) blend in a very large amount (usually at least 50%) of cat gas into the final fuel blend. &nbsp;Cat gas is catalytically cracked heavy fuel oil (bad bad bad). &nbsp;Heavy fuel oil is a paraffinic oil and cat gas still contains a small amount of heavy fuel oil since it is impossible (by the laws of thermodynamics) to completely separate these two hydrocarbons (azeotrope on the T vs. X plot). &nbsp;With that said, I run premium for its cleanliness value, not its octane.

OK, I'm done.