playing around with Octane levels on a stock KA

[Ricks15]

If you have a completly stock KA and if you start mixing certain octane levels will you currupt you're cars computer??? For example if you feed it 87octane gas for work and then by the end of the week youre going to go to screw around at the canyons or at the drag strip you put in 91 octane for those hi performace driving, then when you're going to put back the cheap 87 gas will you get any problems while doing this switching fo gas octane levels???? Because thats what I have been doing and my car has alot of problems when I drive it.

[breakindrifts]

No you wont mess up the car's ecu from mixing octanes.

[Ricks15]

well my car has been acting up latley when I make that transition from 87 to 91 then back 87 octane?

[NemeGuero]

you really don't need a higher octane for a stock internal, naturally aspirated KA. The higher octane is to prevent detonation, but its unlikely you will do that without beating the crap out of your KA with no regard for red lines.

[zero.counter]

You can cause some problems with the O2 sensors when using extremely higher than normal octane levels.
Say for instance, shell octane 93, then adding some of that octane booster from NOS brand, which can raise octane levels from 1 to 4 points. Some of the cheaper O2 sensors have issues (universal ones) at least.

[ranisron]

on a stock KA higher octane doesn't make much of a difference (hence switching around won't cause any problems). Some of us here are quite anal putting higher octane gas into the 240sx since on your gas door it says "premium gas for performance". This whole debate can go on for ever... so... it's all up to you.

I haven't touched 87 octane for a LONG time - I'd say put at least 89 octane for good performance/reliability even though our cars are made to run 87 octane - afterall the difference in money you spent on gas is NOT that significant.

[crioten]

i dont want to state this as a fact, but people have seen people state that a 91 octane will get better mpg than 89 or 87 octane gas. and they have done the calculations showing that they come REALLY close when averaging the cost per mile...

something to think about

[EchoOfSilence]

if your engine is in good condition, 87 octane is fine. my friend with a freshly rebuilt sohc is beating the crap out it, and no problems.

if it's old however, you probably have quite a bit of carbon deposits on your pistons, but usually not enough to change your compression ratio that much.

and your engine problems are not related to your switching of octanes. it's all in your mind. your engine's fucking up for other reasons

[aznpoopy]

iirc sohc is supposed to use lower octane

they only started recommending premium on dohc ka24de's

take this as you will, because i don't remember where the hell i heard/read this from.

[pr240sx]

I was using 87 before going KAT.
At that time, I got better MPG with 87 than 89 or 91.
Now I am experimenting (and probably blowup my engine) going back to at least 89. Adding more fuel and retarding more timing.
My goal, run my KAT on 87 (and again, probably blew my engine) doing 8 psi of boost.
As of now, I am running 89 at 8 psi with the BTM with no problems thougt.

[nrg]

there's no reason to go beyond the recommanded octane rating. the reason is that your stock KA has the right stroke/compression and timing to burn 87. putting anything higher will do nothing for your stock setup.

now for cars that need premium octane, if the owner were to put lower octane. the ecu will know and retard the timing a bit. which the engine will not create the most power of its potential.

Originally Posted by zero.counter

You can cause some problems with the O2 sensors when using extremely higher than normal octane levels.
Say for instance, shell octane 93, then adding some of that octane booster from NOS brand, which can raise octane levels from 1 to 4 points. Some of the cheaper O2 sensors have issues (universal ones) at least.

leaded gaslone is what damage O2 sensors, not octane rating. =)

[Nismo180]

On a technicality you'll get more out of the lower octane, reason being lower octane gas burns a little faster, the retarded flame front speeds are half the reason higher octane works better in detenation prone events. Any tests you have read that state your motor will work better on higher octane were probably not performed in the most scientific of matters, the only "production" motors I know that can run on crap(comparatively) and get better performance off the good stuff are modern fuel injected bike motors. Most have 91 octane maps, but the ECU will detect higher octane fuel and run more timing etc. Your ECU doesn't do that. Get 87 and keep your money out of the gas companies pockets.

[xamS14]

now what if u are running 16 BTDC on your timing, instead of 20 BTDC (fatory). should i be putting 89 or 91 octane?

[96240sxSE]

Going from 20 BTDC to 16 BTDC is retarding the timing, which means that you can use LOWER octane fuel. It also kills power on an N/A motor, since there isn't any boost to replace the lost timing. Hence, there is no reason to retard timing on a stock motor ( unless you have problems handling all that "power").

[skatanic28]

the existence of 2 seperate timing maps in the stock ecu programming leads me to believe that you will get slightly less performance using 87 octane if detonation problems are detected. if someone had a techtom/multichecker like device, this would be a fairly easy thing to check.

[ranisron]

well, let me put it this way.

There's one Marathon gas station 15 miles away from my place that sells 93 octane for 10+ cents more than 87 octane (comparing to the usual 10c increase from 87-89 and another 10 cents increase from 89-93). Which one do I use? 93 octane. Gas in Martinsville is 10 cents cheaper than Bloomington, IN anyway.

It doesn't harm the car nor my pocket as long as I drive my car like a grandma during the day. BTW, I advanced my timing, too... so 89 at least.