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1989 Sport Roof White Pkg 7M-GTE + mods
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Discussion Starter · #1 · (Edited)
My '89 turbo runs on 87 octane gas; I believe the standard blend is up to 10% ethanol. If I behave in my driving I can get around 18 mpg. Basically, I put the cheapest grade of name brand gas in my car, always stopping at some place that has Shell, Exxon, Chevron, etc available. Cheap, but not bargain. I know that gasoline blends are very different today than they were when this car was made. I don't hear the engine knocking so I presume using 87 octane gas isn't hurting it, and there are no stickers anywhere in the car that say "Premium Fuel Only."

Is there anything I need to know about or do for this car specifically with the gas being sold today?

Edit: thanks to madison for pointing out my post mistake.
 

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Im guessing you are bone stock ?

87 octane base fuel is not e85. e85 is 85% alc and 15% gas

I think you mean 15% ethanol fuel (10% is standard where I live but I see other markets to 15%)

the car has knock sensors and is always advancing until it hears knock, then backing off. At 5-6 psi, which is stock, you really have to try hard to have a problem with 87 octane.

some things I would not do with 87 octane....
1. drive in 100 degree outside temp, with AC blasting, accelerating stoplight to stoplight wot
2. part throttle, full boost in 4th or 5th gear at 3000-3500 rpm. most risky area of the factory tune, very aggressive timing an lean fuel because the car is not at wide open throttle.

you can run 93 octane pump up to 15-20 psi, so it makes sense 87 is fine at 5-6 psi. to be honest, I don't drive much and like the extra insurance of octane. on my setup, around 15psi I usually run 4 gal 93 / 1 gal 110 race.
 

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1989 Sport Roof White Pkg 7M-GTE + mods
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Discussion Starter · #3 · (Edited)
I need to update my signature, I think. My car has 264 cams, an aftermarket air intake and exhaust. I replaced whatever turbo it came with with a CT26 OEM so I think that is stock. My mechanic thinks it is making around 275 hp. You are correct; I am not running E85. I will update my post. I am running whatever mostly gas with up to 10% ethanol blend is out there.

I very rarely run over 3000 rpm. I drive in such a way to get it to upshift; once it approaches 3K I lift off the gas slightly to get it to upshift. I try to live in 2300 rpm land as much as possible. My turbo rarely spools up above 2nd gear. The only time I get in the 3000s is when I am driving across Texas at 80+ mph.
 

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^ Thanks Madison. I was struggling with an emotional response to the notion that anyone with more than four functioning synapses would deliberately run a steady diet of 87 octane fucking horse piss in a Supra Turbo, and you covered all the bases eloquently.

For the record, Supra Turbo = 91 octane* minimum especially if it's been modified in any way. Basically any Toyota with a GTE engine in it should be getting 91+ octane. Can you get away with less in some cases? Yes. Is it a good idea or worth the risk to save a few bucks at the pump? No.
Can you run 86 or 87 octane in an emergency, and get away with it if you're running very low boost & are nice to the car? Yes, but really try to avoid doing this if at all possible.


*[(R+M)/2] method, which is the common method of rating octane in North America. Outside of the US, this would roughly be RON 98 or thereabouts.
 

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I need to update my signature, I think. My car has 264 cams, an aftermarket air intake and exhaust. I replaced whatever turbo it came with with a CT26 OEM so I think that is stock. You are correct; I am not running E85. I will update my post. I am running whatever mostly gas with up to 10% ethanol blend is out there.
... The crazy thing, is that since you've got 264* cams installed, and if you're running a stock CT26 at stock boost, those camshafts reduce dynamic compression enough by themselves that it's likely helped save your engine up to this point.
Any idea what your peak boost is with your current configuration? Also, what's the average Density Altitude (DA, aka air density as a measure of elevation) where you're at?
 
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^ Thanks Madison. I was struggling with an emotional response to the notion that anyone with more than four functioning synapses would deliberately run a steady diet of 87 octane fucking horse piss in a Supra Turbo, and you covered all the bases eloquently.

For the record, Supra Turbo = 91 octane* minimum especially if it's been modified in any way. Basically any Toyota with a GTE engine in it should be getting 91+ octane. Can you get away with less in some cases? Yes. Is it a good idea or worth the risk to save a few bucks at the pump? No.
Can you run 86 or 87 octane in an emergency, and get away with it if you're running very low boost & are nice to the car? Yes, but really try to avoid doing this if at all possible.


*[(R+M)/2] method, which is the common method of rating octane in North America. Outside of the US, this would roughly be RON 98 or thereabouts.
lol Im at the total opposite end of the spectrum as OP. like my car is never below 3000 rpm unless im idling at a light.

I hit 6000 rpm every. single. time. I. drive. it.
no exceptions. 99.9% of my time driving is spent in a prius. I get in the supra for one reason -- to hear my turbo scream and rip some pulls to redline. to each their own I guess.
 

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I need to update my signature, I think. My car has 264 cams, an aftermarket air intake and exhaust. I replaced whatever turbo it came with with a CT26 OEM so I think that is stock. My mechanic thinks it is making around 275 hp. You are correct; I am not running E85. I will update my post. I am running whatever mostly gas with up to 10% ethanol blend is out there.

I very rarely run over 3000 rpm. I drive in such a way to get it to upshift; once it approaches 3K I lift off the gas slightly to get it to upshift. I try to live in 2300 rpm land as much as possible. My turbo rarely spools up above 2nd gear. The only time I get in the 3000s is when I am driving across Texas at 80+ mph.

What good is all the fame if you ain't fuckin' the models?
I see you drivin' a sportscar, ain't hittin' the throttle
And I be down, and do a hundred, top down and goggles
Get off the freeway, exit 106 and parked it
Ash tray, flipped it, time to spark it
Gucci collar for dolla
 

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1989 Sport Roof White Pkg 7M-GTE + mods
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Discussion Starter · #8 ·
If I could trade my 7M-GTE drivetrain for a 7M-GE I would do it. I have no need to go fast. I bought this car for open road cruising 500 miles a week. I would have preferred a stock vehicle but this is how it came. The body and interior are in great shape so I had to take the engine it came with.
 

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Either way, you're going to put the right fuel in it from now on, right?
 

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I have 7m GE.. the only fuel I need to run is 87 correct ? Or can I use non ethanol? I also thought about running mid grade even though I am all stock..
 

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Discussion Starter · #11 ·
Ok. I just drove the 55 miles to get home. I have a digital manifold pressure gauge in the car. Twice it got to 4 psi as I accelerated from a stop but dropped immediately when it shifted up. I rarely let it rev enough to even hear the turbo spool up. Driving 65 I pressed the gas all the way to see what it would do and it topped out at 8 psi. Most of the time it was reading -10 to -8 inHg.
 

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Discussion Starter · #13 ·
Either way, you're going to put the right fuel in it from now on, right?
Given my pedestrian driving, unless the TSRM says differently I am using 87.

Regarding density altitude, my house is 50 feet above sea level. My office is 13. I can be standing in the ocean 45 minutes drive from my house.
 

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@fintable...
Depending in you area, if prices follow

87 = 3.09
92 = 3.59

That is $10 dollars per tank delta (yes estimating 20 gallons and not the real 16 gallons on refuel).

Or better yet, that is;
1.75 x starbucks
2.25 x happy meals
1.2x dbl 1/4 pounder with cheese meal at mcds or most any fast food joint
5 9x 20oz soda at the gas statiion

The bad news for you, the oxygenated fuel will hinder mpg just by the sheer nature of having oxygenation in the form of Ethanol

Also the further bad news is that you are a battery replacement away from the stock tccs forgetting all the learned knock values.

The manual was written in the 80's. Oxygenated fuels were not in the pumps yet.

Just pony up the cash for 91/92.
 

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Discussion Starter · #15 ·
I drive 500 miles per week and have to fill once on Sunday and once during the week. I will do some A/B testing and see. I drive to maximize mpg, doing things like drafting behind an 18 wheeler. I’ll do a couple weeks worth of each and report back.
On another note, down here Buc-ee’s has ethanol free gas. I will see if I can get that and also do a $/mile comparison.
 

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I know for my MR2 turbo, premium fuel is required, so I use that. I don't have the owner's manual for my non-turbo Supra in front of me, but if I recall correctly, it recommends premium for optimal performance, and because it's not just some beater Camry I don't give a crap about and is something I want optimal performance from, I go with what the manual recommends.
 

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@sinistar_xx use premium fuel in the non turbo? will the shop manual tell you what to use as well ? because i have that in front of me now
 

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With what we know of the TCCS thanks to @3p141592654 and the massive undertaking of decompiling the stock TCCS.

In the MA70 Turbo. the TCCS will always push timing until knock then pull back and record where it found the knock threshold and store it. If the battery is disconnected it has to relearn that. If it stores the knock values based on 87 vs 91. The total power output will be LOWER since it is taking timing away which means less power at a certain throttle input. (3p, correct any sloppy info)

Lower power output means less MPG (regardless of fuel).

So technically, you want fill car up with the highest octane you can afford, disconnect & reconnect battery and let the TCCS learn the knock value using 91 octane. That will allow the car to run the most efficient ignition values available to it.
 
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