octane question

[cwapface]

i borrowed my dad's integra to scout out houses in portland today and he took the supra out to run errands. I filled his up with 87 because it loves the cheap stuff, and i get back to find out that he filled up the supra with 87. I think he put in about 2/3 of a tank...i drove it and hit boost for a couple seconds and it seemed fine, should i take it easy and just guzzle the the tank or what? I am stock everything, intake, and shimmed wastegate to around 7psi....help, i don't want to blow my motor!

 

[Jeff Lange]

As long as you aren't pinging, there's no problem. My car ran fine on 87 octane up to 7psi without pinging ever.

 

[LamaRossa]

As long as you aren't pinging, there's no problem. My car ran fine on 87 octane up to 7psi without pinging ever.

i ran 15psi daily 87 oct for about 3 years no prob if it blew it would have already

Lamarossa

 

[SupraMario]

all fuels are government regulated in other words, they must be safe for ANY street legal car. my car runs on 87, my moms tahoe runs on 87, dads silverado runs on 87. and i live in BFE, the back country were supposedly we have crappy gas. 93 octane is really about 89, because by the time the gas reaches the station the octane lvl has dropped a couple of points. so when you buy 87, your really getting like 86 or 85 depending on how long it has been sitting around. i wouldnt worry, when i put 93 in my car i see no deference.
LET THE FLAMING Begin

 

[mdr40z]

just dont boost real hard on this tankful

 

[s turbo 87]

7 psi is hardly higher than stock. Doesnt the owners manual call for a minimum of 87 oct anyways? I could be wrong, but at 7 psi I think it should be fine.
Someone please correct me if I'm wrong.

 

[glntom]

Just take it easy on it for the first 1/3-1/2 tank and top it off with 93 octane, which should bring up you octane to around 90 and ease your mind.

 

[Jeff Lange]

7 psi is hardly higher than stock. Doesnt the owners manual call for a minimum of 87 oct anyways? I could be wrong, but at 7 psi I think it should be fine.
Someone please correct me if I'm wrong.

You're not wrong, 7psi is within the stock boost range specs, and 87 is the minimum required. (I think Toyota changed it to a suggested 89 octane on 89+ models, can't remember for sure).

 

[bluemax]

As Jeff said, if you don't get knocking, it shouldn't be a problem.
The car probably really needs 91+ oct as a recommended factory fuel. But in the early days when fuel prices started to climb, and after the gas rationing, no manufacturer wanted to recommend anything other than 87 oct. But these days when the new cars are 10+:1 compression, high octane requirements is just standard practice for performance cars.

I run my car at stock boost in hot dry California summer without problems any problems. The ignition curve must be pretty conservative. Or maybe the knock sensor feedback really helps.

 

[aye mate]

I run 87 on 12psi and no pinging at all.

 

[shaeff]

i wouldnt worry, when i put 93 in my car i see no deference.

thats because you have an N/A.

but really though, my N/A loved 87 octane, my turbo HATES it.

-shaeff

 

[chevyeater]

all fuels are government regulated in other words, they must be safe for ANY street legal car. my car runs on 87, my moms tahoe runs on 87, dads silverado runs on 87....

Try telling that to all of the early Cadillac Northstar owners that put 87 in and melted a piston or 8.

Different engines require different octane, simple as that. Most average vehicles are tuned to run perfect on the 87 swill. Turbocharged engines aren't average.

 

[TONY!]

A have a weak memory of hearing that you can ping without knowing it.
So can you always tell if you are pinging? Will you always hear it?

My questions are aren't if you have the radio on. I mean if you are in a quiet setting (with roof, no radio), will you still always be able to hear all pinging that may occur?

EDIT: to add below

...Different engines require different octane, simple as that. Most average vehicles are tuned to run perfect on the 87 swill. Turbocharged engines aren't average.

I think I read that in a magazine too.

 

[CTsupra]

Tony, not too sure, but I have heard what sounds like copper BB's being dropped on a thin metal sheet, from having bad gas. I had my targa off, radio off and was doing 35mph in 4th gear with a quiet hks 75mm exhaust. It wasn't really that loud, but noticeable to both my friend and I.


edit: you guys are nuts, but gl to ya. I run NOTHING BUT 93 or 94.

 

[doom26464]

I fill up with nothing but pure sweet premuim and I'm only running at 7psi.

I wouldn't worry about it that much.

 

[SupraMario]

thats because you have an N/A.

but really though, my N/A loved 87 octane, my turbo HATES it.

-shaeff

thats weird.
but beleiveable.

Try telling that to all of the early Cadillac Northstar owners that put 87 in and melted a piston or 8.

Different engines require different octane, simple as that. Most average vehicles are tuned to run perfect on the 87 swill. Turbocharged engines aren't average.

i was stating what they i read in SCC mag, it was a 3 page write up on octane
and they basically said that there really isnt a difference, but i do recall "Different engines require different octane, simple as that." something like this being said. now i didnt say that ^^ that was false i just stated that, your car should run on 87.

 

[shaeff]

thats weird.
but beleiveable.

well, in theory, you should run the LOWEST octante possible without pinging. higher octane gas is harder to burn, and burns more slowly. if you can seriously moniter pinging and whatnot, your car will run better on lower octane gas because it burns more quickly.

many people think of high octane gas as like 'race fuel' of sorts. its really not. it all depends on the motor. putting 93 in a car that is built to run well on 87 is doing nothing but draining your wallet.

well, this is my understanding anyway. someone feel free to correct me. i know chevyeater knows quite a bit about gas, perhaps he'll offer some assistence?

-shaeff

 

[SupraMario]

well, in theory, you should run the LOWEST octante possible without pinging. higher octane gas is harder to burn, and burns more slowly. if you can seriously moniter pinging and whatnot, your car will run better on lower octane gas because it burns more quickly.

many people think of high octane gas as like 'race fuel' of sorts. its really not. it all depends on the motor. putting 93 in a car that is built to run well on 87 is doing nothing but draining your wallet.

well, this is my understanding anyway. someone feel free to correct me. i know chevyeater knows quite a bit about gas, perhaps he'll offer some assistence?

-shaeff

hmm thats sounds right.
:thumbup:

 

[lagged]

to put it simply, fuel with a higher octane rating is harder to ignite. the AF mixture in the combustion chamber is compressed, heating the mix. eventually the spark plug will fire and the mixture will be ignited, producing the eventual power that will drive your rear wheels.

what can happen however, is pre ignition (detonation, pinging, what have you). the AF mix can ignite without a spark, if it is compressed enough. when this will happen i suppose is determined by the "flamability" of the AF mix it self.

in other words, running 87 (very very basically, more flamable) is MORE likely to be ignited by compression alone. high compression motors need higher octane, to prevent the mixture from PREigniting. same goes for turbocharged motors, the AF mix is being pressurized in the combustion chamber, creating an AF mix that is more likely to combust by compression before the spark plug fires.

and as shaeff said: "this is my understanding anyway. someone feel free to correct me. "

 

[bluemax]

I believe Lagged said it.
It should also be noted that octane rating is not really what you might be getting at the pump. Fuel manufacturers test the fuel for octane rating then depending on the test, they rate the fuel. Arco regular fuel has a higher octane test than what they rate it as. It tests very close to mid grade rating.
And preignition I am told always occurs. Just not consistantly. That's why if you use high octane fuel you can get better performance, even though you don't notice pinging. The higher octane fuel doesn't have more energy than lower octane fuel, as diesel fuel does. It just does not ignite as easily so you have less spontaneous combustion and better overall performance.