Thats good.
If I could have done the same thing with the Nissan I may have kept it.
But to suffer a loss in milage and power? I sold it.
I could accept less power if I was able to run the cheaper fuel. But the Nissan lost power and the milage would drop from 23mpg to around 17.

 

Just to add more to the octane confusion-

The 2008 Toyota Tundra PU and the Sequoia SUV with the 5.7L engine are factory speced to run on 87 octane.

The 2008 Lexus lx 570 SUV with presumeably the same 5.7l engine runs on 93, and has the same HP and torque figures.

Anyone know about the GM/Chevy/Caddy variants? I know the Caddy recommends 93.

Is it a status/marketing thing? Is that all it really comes down to?

I run a premium line ride, therefore I need to use premium fuel to get my premium ride to perform to the potential I paid a premium for?

 

I got a chance to talk to the Toyota reps and drive a couple of 5.7's hooked to 10k in the Black Hills last summer. And I also asked the regular fuel question.
He pointed out to me that the manual says 87 or higher. So I asked him if this truck needed premium fuel. He said yes it does, for the best performance under working conditions.
The bottom line was this. Toyota did not want to sell a full size truck that had to have premium fuel. So run what you want apparently.
So if you run regular, you experience a decrease in performance. Just like my Xterra. And just like in the FJC.

 

I might be wrong on the LX 570 gas requirement. It may be the same as the Tundra and Sequoia since the engine is the same. The 00-07 Land cruisers and corresponding Lexus lx460 did recommend premium, though.

Along similar lines, the 2008 Denali SUV with the 6.2l Variable Valve Timing engine produces 380HP and 417ftlbs torque. I seem to recall seeing 87 octane on its' gas filler.

The 08 Denali PU truck, with the same engine, produces 403 HP and 417 ftlbs of torque. These Denali PU engine HP numbers are the same as those quoted for the Cadillac 6.2l engine. Last time I checked, Caddy recomends using Premium fuel. I don't know, but I bet that Denali PU recommends premium to get those numbers, just like the Caddy. GM might figure the Denali PU buyer, like a Caddy buyer, won't care about the price difference between 93 and 87, but the Denali SUV buyer would.

This leads me to believe that the GM 6.2L VVT engine does derive a 23HP benefit solely from using 93 octane fuel. Therefore, it should not be unreasonable to expect the same possible gain in the Ford V10, using 93 octane fuel.

So, is the GM engine smarter than the Ford?

The bigger question- Does adding 23-30 HP really make a noticeable difference with a 350 HP+ engine? What about MPG's?

 

Ford has a strategy in a few vehicles(the Mustang Bullitt for one) that's spark adaptive based on knock sensor input. That's probably what the GMs are doing to get that to work properly. There are similar gains to those you're seeing in the GM listed above in a large displacment engine like a 6.8L by going to 93 octane fuel..But you MUST have the PCM calibrated for 93 octane. The OEM superduty tunes DO NOT-DO NOT have any kind of variable adaptive spark strategy,and to my knowledge,it is not possible in the strategy that the PCM is calibrated with. Now-a tune setup for 93 octane with the correct spark table values will work fine,but you cannot just swap back to 87 without changing those spark tables via a reflash or reprogram of the PCM-the knock sensor(s) IS(ARE) NOT reliable spark tuning tool(s)-they're simply a fail-safe to prevent catastrophic engine damage due to detonation.
VVT has alot to do with the power produced by an engine-do you have the values for what RPMs those GM's respectively make their peak power at? I'll bet they're each rated for the different power levels at different RPM's. By simply retarding or advancing cam timing by a few degrees-you can shift the power peak a bit and also affect the total peak value as well.
Yes,you will feel a 30 hp gain in a 350+hp engine,and no it is 100% true that it will use more fuel.
JL

 

hmmm i have the Banks power up kit in mine and regularly run 87. Would it be beneficial to switch to 92? As far as I know the Banks setup is not adjustable for fuel, but I don't know what they recommend to run either.

 

Compression ratio also plays a very big part in whether or not an engine is going to see a reasonable gain when switching to 93, and tuning for it.

Lower compression engines just don't gain as much as higher compression engines will. To fairly compare the V-10 to some of those others mentioned you need to check the specs on them. A 10:1 or higher motor will benefit way more, than a 9:1 motor will.

 

O.K..Langton - that's IT ! I have HAD it with your insults. We are going to settle this like MEN. My honor is at stake. A dual ! STROBE LIGHTS AT FIFTY PACES !

Seriously, Johnny - it just occured to me how we can figure out whether there is a significant enough spark advance on our V-10's to take advantage of using premium fuel.

Next time we use our Excursion (I cant afford to feed the damn thing unless we HAVE to - as when we engage in HEAVY towing our boat or "toys" around).

What I will do, is make some marks on the vibration damper (or perhaps there are still timing marks on those things like in the old days..? Dont know - havnt looked yet). Anyway, I will set up my strobe to get a "base reference" . Then I will use the strobe light to find how much it advances as engine speed goes up, first with a tank of 87, then with a tank of "premium".

Unless you have a better idea, I think that should give us at least a rough idea if there is any significant difference in spark advance, giving us a ROUGH idea of how much further, if any, the on-board knock sensor system can advance our spark.

 

Lunch Update on the GM 6.2L VVT engine-

According to the Denali salesman, premium fuel is NOT required or recommended in either the 380 hp Yukon and is not recommended or required for the 403hp Denali PU truck.

Moreover, according to the Caddy salesman, the 403hp Escalade does not recommend or require premium fuel either.

Just to make sure, I checked the gas filler on all three vehicles. None said premium only.

Interestingly, the Denali(Caddy Escalade) 6.2L vvt PU HP ratings are 403 HP at 5700 rpm and 417 ftlbs at 4300. The Denali 6.2L vvt Yukon is 380 HP at 5500 rpm and 417 ft lbs at 4400 rpms. Sounds like just a numbers game to me. I suppose GM could have dialed in a rev limiter on the Denali Yukon to make the Caddy Escalade look better.

According to Motortrend, the 0-60 times were essentially the same between the 380HP Denali and the 403hp Escalade. EPA gas mileage ratings are the same for both at 12 and 18.

According to the 2008 Ford Superduty brochure, the 5.4 L V8 has Variable Cam timing. The V10 does not. The V10 has silent chain, for what its worth.

Question- For those engines out there that do require 93, what happens if you run a tank of 87 and then move back to 93 for the next tank? Does the system revert back to normal or does it stay at the reduced timing level induced by the lower 87 octane fuel?

 

FWIW, don't believe anything a car salesman tells you. In my experience they don't know squat about what there selling. Go by what the manufactuer states in the manual.

The 5.4l V8 3V also has a higher compression ratio than the V10 on top of the VVT. If memory serves me right the 5.4l 3V has a CR of 9.8:1. I've read that the 5.4l 3V just barely runs on 87 with that fairly high CR.

 

DFK,

I agree, but having driven premium requiring vehicles for the last 7 years, it is my experience that those that require it, say it on the gas filler area to avoid confusion. That is why I not only asked the salesfolks, but also checked the gas fillers. Moreover, having had to fill up with premium over the last 7 years, knowing where gas prices are heading, I am very interested in this topic.

I did not ask to view the owner's manual however. I did check all three vehicles' brochures and none said anything about premium fuel requirements.

The Ford 5.4L V8 does have a 9.8 to 1 compression ratio vs 9.3 to 1 for the V10.

The Toyota 5.7L V8 has an even higher 10.2 to 1 ratio, but yet still rated for 87 octane.

Edmunds has the GM 6.2L V8 in the Denali PU at 10.5 to 1 compression ratio.

 

Here's the spark tables in all white are stock from Ford and are setup for 87 octane regular unleaded. The orange highlighted tables are the tables for running 93 octane.
borderline_knock_table is the max spark you'll see-most times it's less than that due to spark modifiers for air temp,coolant temp,etc,etc.
knock_sensor_advance_limit is the max amount of spark allowed to be added based on knock sensor input-no matter what the condition-and after some timers expire.
JL

 

No. But there are exceptions.

For instance, if your vehicle is pinging under normal circumstances with 87 octane, AND the knock sensor is working correctly (which is up for debate based on many people's ping reports). If, by chance, you load the thing enough, get it hot enough, and get it to ping with 87 octane, you will lose power when the PCM backs off the timing. For how long? I don't know. Maybe Johnny knows.

But there are REAL WORLD instances where you would get pinging with 87 octane, the knock sensor does it's job, and it backs off.

Now, if you were running a higher octane at that time, it wouldn't ping, and the PCM wouldn't back off, and you'd have more power than you would if you were running 87 octane.

As for the driveability things with higher octane, I can tell you this, doing it many times with Ford modulars, they do suffer a small amount of throttle response at or near idle. Cold-start performance is worse, you name it.

It just feels like the engine is running "colder" overall ... Again, a real-world experience.

You could know everything there is to know, but if you can't play nice with others, there's no need for you to be here.

--

Something in the discussion about compression ratios of the various engines stuck out... The higher compression ratios are on engines with VVT, because they can handle it without pinging.

The 3-valve V10 doesn't have VVT.

If they were to do it, and raise the compression, it would squeeze out a few more ft/lbs without having to go past 87 octane.

Do it! It probably won't prove anything, I don't expect it to change, especially at idle and low loads.

 

Johnny - thanks for taking the time to do that impressive research. But you are right. I AM stupid ! I cant figure out what those tables are demonstrating. YOu seem to know quite a bit about the computer controls on our spark advance. Perhaps you can explain this to me ( since my experiment may prove there are differences in the advance curves depending on the fuel, but even if it does, it will probablly be hard to tell how much. Soooo

Can you explain this to me - let's assume the knock sensor is working properly, and the other inputs are within specs (meaning no over-heating). Now let's assume the knock sensor is not reporting ANY ping. HOW MUCH SPARK ADVANCE IS THE SYSTEM CAPABLE OF IN DEGREES BTDC ?

 

What RPM? What load? What ACT? What ECT? What MPH? Time running since start? What slected gear? Time since last knock detected?
If all of these are zeroed out and have no timers to fulfil-the table above shows a MAX allowed increase of 2 degrees.
The difference from 87 to 93 octane spark tables are an average of around 8 degrees.
So,to put it simply..The spark advancce allowed by the OEM PCM is nowhere near what one needs to justify or to benefit from using 93 octane fuel with a stock PCM program. There will be no mileage gains, nor willl there be any power gains, unless you're knocking so badly that the sensor's input has the PCM pulling timing with the fuel you're currently using(which would not be up to the standards of 87 octane if it's doing that).
JL