Can a forced induction engine actually run safely on 87 octane?

[admzn]

Even my 02 Xterra with the supercharger has knock control, but it is far more basic than the newer cars. It will pull timing/boost if you run any less than 89 octane it seems. And there is a very noticeable difference. They had a known problem with the knock sensors that came with them, they all failed before 50k. So a lot of people were running around on the default "limp home" fuel map and complain about the gas mileage and how it is not worth having.

I have installed a smaller pulley on the blower, so always run 91 now. It only costs about $10~ more per fill up around here.

If and when I purchase a newer turbocharged vehicle I will run the reccomended fuel as I always want the most power out of the cars I drive.

 

[Gene K]

323 ci DOHC V8 Turbo
Conventional EFI
12.0 Compression
2.3x Naturally Aspirated Torque
108 Octane

213 ci DOHC V6 Turbo
Direct Injection
10.0 Compression
1.5x Naturally Aspirated Torque
87 Octane

Street engines can get away with it because they are under-stressed relatively speaking and have so many tools in their box. Modern control systems can reduce cylinder pressure with Ignition Timing, Air Fuel Ratio, Valve Timing, Turbo PSI and Throttle Body Opening (Of course not all ECM use all the tricks).

 

[ammolab]

I found some turbo engines liked mid grade ... and figure it’s both cheaper and fresher than premium

Mid grade is a mix of regular and premium gas...how would it be “fresher“ than either one?

 

[4WD]

Mid grade is a mix of regular and premium gas...how would it be “fresher“ than either one?

Yeah … I know that … but if half of it is the number one seller it’s fresher than the worst seller, premium …

 

[Ws6]

Turbo cars used to always require premium fuel in the past. Now some owners manual specifically state it's okay to run 87 (with some stating that performance will be reduced). Even my WRX's OM states that which really surprised me.

Isn't high compression with low octane a bad idea all around? I thought that was a big reason for the fuel dilution Honda was experiencing in their turbo engines.

How can an EcoBoost 2.7 possibly be spec'd out to run under all operating conditions constantly on 87 octane, with only a minor HP loss, yet not have it be detrimental to its lifespan?

Sure. My cx5 is pushing nearly 17psi with 10.5:1 compression and runs fine on 87. Part of it is that they use cooled EGR so they dont have to dump fuel to cool the charge. Why it gets such awesome real world mpg. Its rated 22/27, and my lifetime over 50k miles is 26.9.

 

[Gene K]

Sure. My cx5 is pushing nearly 17psi with 10.5:1 compression and runs fine on 87. Part of it is that they use cooled EGR so they dont have to dump fuel to cool the charge. Why it gets such awesome real world mpg. Its rated 22/27, and my lifetime over 50k miles is 26.9.

Interesting. I wasn't aware Mazda used a dedicated EGR System. Most modern engines I've dealt with modify the valve timing to introduce inert gases into the combustion process.

 

[Al]

Also turbo vehicles have a lower compression ratio. I use + on my '18Forester XT

 

[Ws6]

Interesting. I wasn't aware Mazda used a dedicated EGR System. Most modern engines I've dealt with modify the valve timing to introduce inert gases into the combustion process.

Mazda did a ton of cool stuff with their system.

https://www.automobilemag.com/news/deep-dive-inside-the-mazda-skyactiv-2-5t-turbo-engine/

 

[Gene K]

Mazda did a ton of cool stuff with their system.

https://www.automobilemag.com/news/deep-dive-inside-the-mazda-skyactiv-2-5t-turbo-engine/

I know they have an engine that switches back and forth from spark to compression fired and runs on gasoline that has either just been or is shortly to be introduced in Europe. Interesting times for the internal combustion engine.

 

[TiGeo]

Also turbo vehicles have a lower compression ratio. I use + on my '18Forester XT

Bingo. VW 1.8 turbo 4 = 10:1, VW 3.6 NA VR6 = 12:1....of course you pressurize the chamber from the turbo so that factors in. If you use the min. octane your engine was designed via the software to run off, it will be fine.. If you want a little less timing pull/more power, run higher octane. Simple.

 

[circuitsmith]

In hot weather, 90+F, I mix regular and premium half and half, and my car, which is spec'd for 87, runs a little better in stop-and-go with AC cranking.
Previous 2006 Toyota Matrix did the same.

 

[SZR48207]

In hot weather, 90+F, I mix regular and premium half and half, and my car, which is spec'd for 87, runs a little better in stop-and-go with AC cranking.
Previous 2006 Toyota Matrix did the same.

Why not just buy mid grade?

 

[2strokeNorthstar]

I bet 99% of turbo Hyundai’s run on 87

 

[TiGeo]

In hot weather, 90+F, I mix regular and premium half and half, and my car, which is spec'd for 87, runs a little better in stop-and-go with AC cranking.
Previous 2006 Toyota Matrix did the same.

I have noted the same in our Focus - hot summer weather + a/c....running 93 seems to help it out. There was a report a while ago showing the same results.

 

[RooflessVW]

Turbo cars used to always require premium fuel in the past.

My 1982 280ZXT required only 87.

 

[Skippy722]

Why not just buy mid grade?

He might be going to half a tank and just switching between the 2, that would put him at ~90 octane for about the same price as 89, unless he can only get 91.

 

[Saabist]

My 1997 Saab 9000 turbo has no problem running on 87 octane regular gas but makes less power than with premium, you can feel the engine being held back as ignition timing and boost are curtailed when you hit the loud pedal. (Usually I just fill with premium.)

 

[walterjay]

My Ford Transit Ecoboost runs great on 87 octane. My Hyundai Tucson 1.6 Turbo does ok on 87 but is a different engine using 89 octane. It just opens up and goes. I have used 93 octane and see no difference in performance over the 89. So I use a steady diet of 89.

 

[antonmnster]

I run 87 in my 335i all the time, especially on road trips where premium is not only dramatically more expensive but questionable quality, since no one ever buys it.

Never had an issue. (I had a tank of premium from Costco lately that lead to some really long cranking times... assuming it was fuel since it's gone away.)

223,000 miles and taking it camping next week in South Dakota.

 

[Gene K]

Incidentally,if anyone cares the limit on gasoline appears to be around 33.0:1 Effective Compression with Gasoline. Once you get to that point more fuel or higher octane doesn't appear to help. It simply turns into a compression ignition engine.

The reason the example I gave earlier has 12.0 Static Compression is it was built for a class that has a turbo size limit.