Why 93 Octane in a GDI engine if it isn’t called for?

[Tdog02]

This brings up a lot of questions. What is considered high compression now days? All these modern engines are using variable valve timing. So if you are 10:1 compression or higher and your engine control module can adjust for it, why not run 91/93 all the time? It will add timing and increase your output. I see no waste of money in this simple power adder.

Maybe some of the engines we are seeing problems with (timing chains, etc...) are because the low octane fuel is causing retardation below the threshold of the ECU. It bottoms out and can't adjust enough.

 

[TiGeo]

right...Shell regular gasoline meets or exceeds Top Tier standards but Shell V-Power Nitro Premium exceeds their regular unleaded gasoline...what is hard to understand about that???

I wouldn't use Premium unleaded fuel if my car wasn't designed (or changed) to take advantage of it...car computers do not "detect" higher octane and tune for that...if your car doesn't need it (higher octane), your car won't take advantage of it to use it...

Bill

ehh...not quite. Here are two logs from my VW Atlas....one on 87 (which it is rated to be able to run) and one on 93. Both winter blends and both in similar conditions/same road/WOT pull. You'll note less timing correction on 93...that's power my friend so even a car not rated for 93 *can* gain a benefit in the top of the range w/r to power IF you log it AND you see timing correction on 87. Modern ECUs will push timing basiclaly until the knock sensors say stop, so, if you are getting some KR on 87 you'll gain a benefit running 93 but how much...not worth the price of admission IMHO. I run 87 in that Atlas with the 3.6 VR6. In the mountains or towing? I'd run

93.

 

[TiGeo]

LSPI is basically small displacement turbo engines with autos being lugged (low RPM/high demand) b/c of the overly eco-focused trans tunes upshifting too soon. I understand higher-Ca oils can contribute IF you are under those conditions.

 

[TiGeo]

This brings up a lot of questions. What is considered high compression now days? All these modern engines are using variable valve timing. So if you are 10:1 compression or higher and your engine control module can adjust for it, why not run 91/93 all the time? It will add timing and increase your output. I see no waste of money in this simple power adder.

Maybe some of the engines we are seeing problems with (timing chains, etc...) are because the low octane fuel is causing retardation below the threshold of the ECU. It bottoms out and can't adjust enough.

Because unless you are taking advantage of tha tpower, the slight bump in mpgs will never beat the math on premium costing sometimes almost $1/gallon. If you are just driving normally, why waste the money on something most people can't even feel?

 

[odie]

Have been using mostly Top Tier 89 w/E10 for both cars . May go to the Top Tier 87 w/E10 .



Refers to TOP TIER and non Top Tier gas .



Oils formulated for D.I. and deposits . L.S.P.I. ( Low Speed Pre Ignition ) also mentioned . Not promoting their products , applies to other oil manufacturers as well .

 

[nicholas]

right...Shell regular gasoline meets or exceeds Top Tier standards but Shell V-Power Nitro Premium exceeds their regular unleaded gasoline...what is hard to understand about that???

I wouldn't use Premium unleaded fuel if my car wasn't designed (or changed) to take advantage of it...car computers do not "detect" higher octane and tune for that...if your car doesn't need it (higher octane), your car won't take advantage of it to use it...

Bill

Not true.
The ecu will try to advance timing as much as the fuel will allow.
Especially true in very hot weather.

I have had numerous cars where the engine timing was more advanced with high octane 91 vs 87.

This was verified many times via scan tool and live data.

All 5 of them recommended 87 or higher.

Except our new kia.
The manual says the fuel required is 87 AKI but also recommendeds 91 octane.
The 12.3:1 compression ratio might have something to do with that.

 

[silversport]

that's contrary to what I've read elsewhere that spark knock sensors etc contribute...your engine will use the octane it is designed to use and is in the computer mapping, etc...using higher octane will not allow your engine to advance timing (unless it was designed to do that) and there is usually no way the engine or computers "know" you increased the octane other than what was designed into the computer and or using knock sensors etc...unless your particular car is designed to do that such as with your KIA example or like the new Mazda CX-9...

Bill

 

[TiGeo]

that's contrary to what I've read elsewhere that spark knock sensors etc contribute...your engine will use the octane it is designed to use and is in the computer mapping, etc...using higher octane will not allow your engine to advance timing (unless it was designed to do that) and there is usually no way the engine or computers "know" you increased the octane other than what was designed into the computer and or using knock sensors etc...unless your particular car is designed to do that such as with your KIA example or like the new Mazda CX-9...

Bill

IF you aren't seeing knock on 87 that is correct.

 

[nicholas]

that's contrary to what I've read elsewhere that spark knock sensors etc contribute...your engine will use the octane it is designed to use and is in the computer mapping, etc...using higher octane will not allow your engine to advance timing (unless it was designed to do that) and there is usually no way the engine or computers "know" you increased the octane other than what was designed into the computer and or using knock sensors etc...unless your particular car is designed to do that such as with your KIA example or like the new Mazda CX-9...

Bill

Here is a recent example.
Our 2016 mazda 6 required 87....
On very hot days it would pull timing so much at one point I thought I had engine damage.
The power and timing was restored as soon as I switched to 91 octane.
Scan tool verified that timing was restored with 91.
When I called Mazda to ask why they said the ecu is always trying to run the most advanced timing for mpg and power.
In hot weather and high loads 87 simply needed timing retarded.
Being a 13:1 stock compression ratio.....I'm surprised it was not speced to use 91 from the go.

 

[nicholas]

IF you aren't seeing knock on 87 that is correct.

I'm not talking knock here .....just timing being pulled and restored to stock with 91 in certain conditions

 

[BMWTurboDzl]

I’ve read where people look to control intake valve deposits in GDI engines by using 93 octane top tier gas … Unless your GDI engine calls for 93 octane gas - how is this supposed to help?

They're misinformed. IVD buildup is largely dependent upon PCV design and oil consumption.

 

[subyski]

When I called Mazda to ask why they said the ecu is always trying to run the most advanced timing for mpg and power.
In hot weather and high loads 87 simply needed timing retarded.
Being a 13:1 stock compression ratio.....I'm surprised it was not speced to use 91 from the go.

It's likely because most end consumers don't want to pay for premium fuel prices for a "normal" car. Manufacturer's have to tune a vehicle as such and retain mpg.

 

[TiGeo]

I'm not talking knock here .....just timing being pulled and restored to stock with 91 in certain conditions

"timing pulled" = knock retard here. If you are seeing KR be defautl timing isn't as advanced as it can be...I think we are saying the same thing.

 

[nicholas]

"timing pulled" = knock retard here. If you are seeing KR be defautl timing isn't as advanced as it can be...I think we are saying the same thing.

Thinking again....you are correct, my apologies....
I have a nasty flu and a very foggy brain ..

 

[nicholas]

It's likely because most end consumers don't want to pay for premium fuel prices for a "normal" car. Manufacturer's have to tune a vehicle as such and retain mpg.

That's exactly why....
I guess I'm trying to prove that the ecu, in certain cars, can differentiate between 87 and 91.

Our Mazda did this
Our odyssey
Our Santa Fe 2.0t
And our Carnival can also adapt to 91 based off of live obd2 data.

 

[I<3oil]

That's exactly why....
I guess I'm trying to prove that the ecu, in certain cars, can differentiate between 87 and 91.

Our Mazda did this
Our odyssey
Our Santa Fe 2.0t
And our Carnival can also adapt to 91 based off of live obd2 data.

Mazda definitely does and even states in publication:

The additional engine option is an incredibly powerful SKYACTIV®-G 2.5T engine that produces 227 horsepower and 310 lb-ft of torque when 87 octane fuel is used. On the other hand, when 93 octane fuel is used the outputs are 250 horsepower and 320 lb-ft of torque.

 

[Jimmy_Russells]

Every vehicle made in the last 15+ years can "detect" octane. My BMW even has an "average octane" monitor you can see with a scan tool. The ECU is going to run as much timing advance as it possibly can, regardless of the fuel in the tank. Whether you run 87 or 91/93 is going to shift the window of timing it can run. Whether or not a more advanced timing window is of actual real world benefit is dependent on the vehicle. Most modern turbocharged engines will make substantially more power with more octane and/or ethanol content.

 

[nicholas]

Mazda definitely does and even states in publication:

My Mazda 6...was the 2.5 non turbo

 

[twX]

Every vehicle made in the last 15+ years can "detect" octane. My BMW even has an "average octane" monitor you can see with a scan tool. The ECU is going to run as much timing advance as it possibly can, regardless of the fuel in the tank. Whether you run 87 or 91/93 is going to shift the window of timing it can run. Whether or not a more advanced timing window is of actual real world benefit is dependent on the vehicle. Most modern turbocharged engines will make substantially more power with more octane and/or ethanol content.

Ethanol content is an important consideration here. GDI engines effectively get a large octane boost with ethanol. Around here, the choice is between 87 E10 and 91 E0, and there is very little difference in knock resistance between them on my TGDI engine.

I've made custom tunes for each fuel type, and ignition timing is pretty much the same through most of the rpm/load range, the biggest difference being 2 degrees of timing retard required above 5k rpm with the 87 E10. On the stock tune, there was quite a bit of knock on the recommended 91 E0, and virtually no knock on 92 E10.

 

[I<3oil]

My Mazda 6...was the 2.5 non turbo

.......cool?