PDA

View Full Version : the right Octane



Huaraches
03-05-2013, 08:32 AM
I dont have an owners manual for my 1990 GT so i dont know what is the right octane to be pumping. i dont know about the compression ratios and stuff like that. all i knoe is that pumping 91 oct on my GT doesnt help with MPG and performance either. i pump 89 oct my car seems to run fine with that octane rating. ive personally havent pumped 87oct so i dont know if it actually runs better and gets better mpg with that octane rating.

Doowstados
03-05-2013, 08:38 AM
The GT and GT-S models use 87. The Alltrac uses whatever premium you have in your area.

Huaraches
03-05-2013, 04:47 PM
so is their any benefits in me using 89 over 87 ? or does 87 have better benefits than 89?

BabyBear
03-05-2013, 06:30 PM
so is their any benefits in me using 89 over 87 ? or does 87 have better benefits than 89?

Its more about altitude and region. In Utah we only get up to 91 for premium instead of 93 and our lowgrade is 85, but at our elevation it doesn't really matter so much that its lower. The 5SFE runs on the regular unleaded, so 85-87, whatever the low grade is. You wont see any benefits at all for running higher octane in your car unless its tuned for it. Only thing it will do is cause you to spend an extra few dollars per fill up putting it in.

underscore
03-05-2013, 06:43 PM
91 and even 89 are overkill for a 5S. I ran 89 for a couple tanks and it seemed to clear some stuff out cause it felt a little bit smoother, but then I dropped back down to 87 and it felt the same. Bear in mind putting in too high of an octane can actually rob power.

Huaraches
03-05-2013, 07:09 PM
Ok so if the 5s-fe is ment to run in lower grade Oct does it still risk its chances of getting an engine knock ? I pump good gas shell Or mobil so i would like to believe their 87 is better than arco and up There with 76 and chevron . If its performance is affected by higher Oct I imagine it also affects mpg. And all that has to do with the compresión of the motor?

Doowstados
03-05-2013, 08:00 PM
Running 87 will not damage your engine or increase wear. Also, the whole "this gas is better than that gas" is a myth. Some gas just has additives in it that you are seriously over paying for. Goto the cheapest gas station you can find and pump 87. Every oil change, dump a bottle of injector cleaner into your tank. It'll be a lot more effective at keeping your engine clean than using the other gas (and a lot cheaper).

4thgenceli
03-05-2013, 08:08 PM
My '87 GTS I had would ping on 87 octane and 91 octane. She liked 89 Octane. My wife's car runs like crap on 89 or 91 octane. She likes 87 octane from Shell only. Jasmine really likes the 91 octane from Shell as well.

underscore
03-05-2013, 09:58 PM
Shell made shit gas in the early 2000's and killed everyones fuel pumps, I've never forgiven them for that one. Aside from that I gas up anywhere.

For the 5S mine has 320k kms on it and I'm pretty sure it's been served nothing but 87 it's while life, it runs fine. If the manufacturer specs 87 octane, that means the engine is safe to run 87 octane all day long no problem.

Huaraches
03-05-2013, 10:21 PM
Ok i will try some 87 next time and see how the car starts to run.

I didnt knoe about that incident with shell did ppl get monkey back Or something? Shell and mobil are basically the same company right ?

4thgenceli
03-05-2013, 10:23 PM
Yes I agree they did. Since about 2008 I've been using them almost exclusively.

underscore
03-06-2013, 12:40 AM
yeah if you showed them receipts or something they paid for new fuel pumps. My mom's van, my grandpa's Jeep, his brothers Jeep, and my first car (before I bought it) all had their pumps killed (the car that became mine only had a 2 year old pump in it) and replaced by Shell.

Huaraches
03-06-2013, 12:58 AM
Ok well Ive been pumping since a year and Ive been ok as far as the fuel pump goes

underscore
03-06-2013, 01:28 AM
I highly doubt they have any problems now, they just left a bad taste in my mouth.

KoreanJoey
03-06-2013, 08:06 AM
Not ARCO.

Huaraches
03-06-2013, 09:08 AM
so just to know how it funtions higher octane is for cars with higher compresion ratio and reg octane is for lower compresion cars or how those that motor science work ?

BabyBear
03-06-2013, 06:55 PM
The octane rating is basically a number that shows how much energy it takes to ignite the fuel, and how likely it is to burn in a controlled manner. The higher the octane, the less likely it is its going to self ignite. When you have a high compression engine, or a boosted engine, the compression in the combustion chamber is a lot higher than in a non boosted, or lower compression engine and lower octane fuel is a LOT more likely to self ignite in a boosted or high compression motor. Another thing you can do with higher octane fuel is run more advanced ignition timing, which in turn can make more power due to it being a more efficient burn in the combustion chamber. With your car though, 85-87 shouldn't have any issues. How Tim had ping on 91 octane is beyond me. He must have been getting bad gas or something. If your engine isn't pinging on 85 or 87, whichever your regular unlead is where you live, you don't need to worry about running higher octane. Higher octane gas also doesn't mean it has more energy or anything in it either, its just about how stable it burns.

Huaraches
03-06-2013, 07:42 PM
oh i see it's seems more clear now. so if i were to advance my timing with 89 fuel (91 is too much these days lol) will it benifit or will i lose more mpg then gaining power

BabyBear
03-06-2013, 08:13 PM
Not sure you'd benefit very much from doing that. If you do, it'd be marginal. I wouldn't run any higher octane than necessary until you've done mods to require higher than regular unleaded.

Huaraches
03-06-2013, 11:53 PM
Only upgrades are stage 2 clutch and alumminum flywheel. No power upgrqdes

Murgatroy
03-07-2013, 12:33 AM
I ran cheap regular gas in Chaos for fifteen years with advanced timing.

Unless you have a 3SGTE in your car, YOUR CAR WAS DESIGNED FOR REGULAR. If you want to run premium in it, go for it, not hurting anything other than you wallet.




If you modify the internals in order to gain higher compression, you will have to up the octane. There are less than a dozen folks on the site that have done this. If you have not added a turbo, shaved your head, decked your block, put flat top pistons in your engine, ETC... you are still fine with regular fuel.

Huaraches
03-07-2013, 01:32 AM
i see cool thanks :)

as for those upgrades go is the cheapest one getting the head shaved ?

Murgatroy
03-07-2013, 02:24 AM
Sure, but there is no real gain in just shaving your head. You might gain half a point compression. Make it feel a little quicker. But without a lot of expensive work, you won't get much.

MrWOT
03-07-2013, 02:31 AM
You actually lose power going up in octane unless you tune for it. The O2 sensor will lean the mixture.

KoreanJoey
03-07-2013, 08:22 AM
With a later model ECU with automatic spark advance and a knock sensor you might see some gains. However, the 5th generation celica ECUs were not that smart.

Galcobar
03-07-2013, 09:26 AM
From what I understand, the money you could spend on higher octane fuel wouldn't buy you as much of a performance improvement as the same money spent on better tires or lower-weight wheels.

grimmythereaper
03-07-2013, 02:27 PM
since this thread has started i switched to 93 from 87 and while the power gains are few the motor feels "happier"

underscore
03-07-2013, 06:28 PM
^ On what motor? Running 93 in a car that only needs 87 is nothing but a waste of money. You might clear some stuff out with the first tank, but after that you're achieving nothing.

grimmythereaper
03-07-2013, 06:51 PM
^5sfe.

Huaraches
03-07-2013, 10:18 PM
Other than compression What about giving it more air. Because a buddy told me that using a mk3 supra butterfly will gain more throttle response but u need to bore it (our throttle body )....oh cool i havent pumped gas yet so next time ill pump 87 and see how it runs although its still going to have 89 for more than half the tank

KoreanJoey
03-07-2013, 11:02 PM
Your buddy is high. The main restriction with the 5S is in the cams. Doesn't matter how big of a butterfly you put on it.

Huaraches
03-08-2013, 03:01 AM
Lol well that wasnt for compresion. It was for more air response ect.

KoreanJoey
03-08-2013, 09:18 AM
Again, won't get more air response because the restriction is in the cam.

KoreanJoey
03-08-2013, 09:19 AM
If anything you might get less response because you're airflow velocity will be lower.

Huaraches
03-08-2013, 05:50 PM
How is it lower if throttle body is opened more ? The cams for the 5s-fe don't really exist anymore right ?

KoreanJoey
03-08-2013, 10:21 PM
Higher volume, lower velocity. Try blowing through a paper roll tube vs a straw. Straw is less volume but higher velocity.

KoreanJoey
03-08-2013, 10:21 PM
The cams for the 5s-fe don't really exist anymore right ?

http://www.deltacam.com/

They'll do a weld and regrind to whatever spec you want.

Huaraches
03-08-2013, 11:44 PM
Higher volume, lower velocity. Try blowing through a paper roll tube vs a straw. Straw is less volume but higher velocity.

SO does that make intake pipe usless if u upgrade to 3" pipping .? Since its lower velocity?

KoreanJoey
03-09-2013, 12:36 AM
Probably. Main upgrade in the intake system would be a proper filter. Actually, thinking back I think the 5SFE had the stupid accordion intake, upgrading to a larger size probably won't help you but changing to a smooth intake and a better filter would help.

Huaraches
03-09-2013, 01:06 AM
Probably. Main upgrade in the intake system would be a proper filter. Actually, thinking back I think the 5SFE had the stupid accordion intake, upgrading to a larger size probably won't help you but changing to a smooth intake and a better filter would help.

Yeah it has a retarded wrinkle in the middle of the pipe and the this tumor thing sticking out on the side witch I think makes it more restrictive

grimmythereaper
03-09-2013, 01:58 AM
Lol the tumor thing is a silencer.

Huaraches
03-09-2013, 03:05 AM
Lol the tumor thing is a silencer.

lol yeah i know so if i restricts the air too right?

KoreanJoey
03-09-2013, 03:32 AM
I don't know if the silencer does any harm. But yes, right now, the intake is probably the biggest restriction on that side of the motor. After that, cams. Don't disregard the exhaust side though. Everything works together, start addressing the restrictions and move on from there.

grimmythereaper
03-09-2013, 04:08 AM
lol yeah i know so if i restricts the air too right?

i wouldnt think so, it just redirect the air in a circle, then into the throttle, i would say thats why u can hear the air at full throttle bc it bypasses the silencer

Huaraches
03-09-2013, 05:08 AM
so has anyone gotten a different Pipe for the intake that will work properly .I have a diff one. but from What I learned today its prob worthless ITs one of the autozone flexible Pipes im saying not very smooth and ITs 3" so probably better of with the stock one its just that I changed it because it showed signs of cracking in the middle .

KoreanJoey
03-09-2013, 08:27 AM
Get a piece of mandrel bent tube. Might hit up an exhaust shop.

Doowstados
03-09-2013, 09:36 AM
Does the creases in the stock tube really make that much of a difference to make it worth all the trouble of bending a pipe? I feel like unless you have some other, more serious mods (bored/stroked/cams/turbo etc) that the work you're putting into the intake isn't going to do anything noticeable, maybe give you some more noise.

I ran a short ram and a crappy custom CAI for awhile and ended up switching back because I felt like I actually lost a little power and I didn't like the noise on my weekend 2 hour commute. The stock airbox is actually pretty nice, IMHO.

KoreanJoey
03-09-2013, 04:17 PM
Honestly, I'm not sure. Depends on how restrictive it is. I've never ran a dyno w/ and w/o so I couldn't tell you for sure.

The 5S isn't a performance motor, not without serious modification so I really don't know where all the restrictions are.

Huaraches
03-09-2013, 05:14 PM
Well it might not make a difference. But with a less restrictive intake im sure one can get better mpg with the right octane witch im going to do today and pump some 87. And switching back to stock intake Pipe .

Murgatroy
03-09-2013, 05:37 PM
I liked the sound of the short open intake. The air sucking was awesome. It was worth that alone. I still remember that from all those years ago. It was a nice little howl when you got on it.

Luni
03-09-2013, 11:15 PM
MrTurrari knows where all of the restrictions are.

He says theyre in the intake manifold and head (cams, valves etc)

PiroGt
03-10-2013, 06:35 AM
I liked the sound of the short open intake. The air sucking was awesome. It was worth that alone. I still remember that from all those years ago. It was a nice little howl when you got on it.

Thats the reason I have one, just for that sound. As for the tubing, it would most likely be a minimal gain a most. I removed the silencer "tumor" thing and I like to believe I got a better response. Not faster though.

Relevant for intakes: http://www.youtube.com/watch?v=PAIxeQUSg-Q

grimmythereaper
03-11-2013, 12:01 AM
Thats the reason I have one, just for that sound. As for the tubing, it would most likely be a minimal gain a most. I removed the silencer "tumor" thing and I like to believe I got a better response. Not faster though.

Relevant for intakes: http://www.youtube.com/watch?v=PAIxeQUSg-Q

i love the trd lazer episode

l0ch0w
03-11-2013, 09:11 AM
Are you trolling for an excuse to put high octane fuel in your car?

Most N/A power gains are going to be cams, then exhaust, then intakes. But with that requires higher RPM, and a computer change...

Removing the "tumor" thing aka resonator will do nothing except make your intake sound louder and reduce your vehicle weight by 0.1lbs. If you can notice the power gains from that, then you sir have one seriously sensitive butt dyno... Perhaps the extra noise made things seem faster?

Electric turbofan supercharger that plugs into your battery... now thats where some serious gains are...

Huaraches
03-11-2013, 05:16 PM
Are you trolling for an excuse to put high octane fuel in your car?

Most N/A power gains are going to be cams, then exhaust, then intakes. But with that requires higher RPM, and a computer change...

Removing the "tumor" thing aka resonator will do nothing except make your intake sound louder and reduce your vehicle weight by 0.1lbs. If you can notice the power gains from that, then you sir have one seriously sensitive butt dyno... Perhaps the extra noise made things seem faster?

Electric turbofan supercharger that plugs into your battery... now thats where some serious gains are...

lol electric turbo fan?? you mean those ebay products http://www.youtube.com/watch?v=cbGWgvJN1_8 apparently they dont work lol

PiroGt
03-12-2013, 10:59 PM
Um I didn't say that I got power gains buy removing the "tumor" but instead said that I believed to have better response. Something similar to tightening a loose throttle cable. Honestly I think its just perceived gains.

I did have a question regarding gas though. I have noticed something with Arco. When I pump arco, low Octane, I get a really good feeling car happy engine and great gas mileage. But during start ups I get a little cloud of blue smoke. Only happens with arco, low octane. No other gas I pump causes this....any Ideas?

Oh P.S Trd Lazer FTW

KoreanJoey
03-12-2013, 11:25 PM
That smoke on start up is probably due to worn valve stem seals causing oil to pool up on the pistons while it sits. Check your oil consumption between oil changes. Chances are that it's time to change out the valve stem seals.

PiroGt
03-26-2013, 05:28 AM
Humm ill have to look into that. So, im guessing other gas has better lubrication properties?

KoreanJoey
03-26-2013, 12:20 PM
No not really...

PiroGt
03-27-2013, 02:54 AM
See the thing is that it only happens with arco low octane. Any other gas and nothing, so I was guessing other gas lubricates the seals and keeps the oil from pooling. humm...so if its not that any Idea why acro causes this while others don't. Im currently running royal purple 5w-40 if that helps at all. Thanks by the way

KoreanJoey
03-27-2013, 04:21 AM
AFAIK the additive packages aren't really aimed towards lubrication. I'm not exactly sure what's going on with your car. I'd check the ignition timing and make sure it's correct.

underscore
03-27-2013, 04:50 PM
it might be an additive in their gas that is pooling somewhere and causing this.

PiroGt
03-28-2013, 07:31 AM
it might be an additive in their gas that is pooling somewhere and causing this.

That makes a lot of sense. Ill probably still have my main mechanic look at it. It was burning oil, not a lot but still.

KoreanJoey
03-28-2013, 08:26 AM
I'm gonna guess stem seals. Super easy. I'll even cut you a deal. :)

Huaraches
03-28-2013, 10:20 AM
So ive been running 87 now and i gota say with a slightly pressing the gas and keeping it constant i managed to get 30 mpg on my 5s-fe mostly highway, some street and up hill and down hill