89 Octane works

[Armada]

One of our members, Juma, did a lot of testing regarding octane and timing in the Endurance engine. Here is the thread:

testing timing advance

Given the equipment he was using, it seems pretty clear that our ECU's absolutely do allow timing to continue to advance until knock is detected. With premium fuel, he proved that the timing did continue to advance. That means more power at high rpm or when towing a load.

You can also do a search. String together words like "octane" "timing" and "power" and see what comes up. There is a ton of work already done.

My anecdotal experience is that it takes a couple tanks for the effect of the premium to kick in. I have not dynoed the truck on a chassis dyno, but have a G-Tech Pro Competion. That device does seem to show a slight increase in maximum power and torque, but it is within the range of error based on differences in temperature, atmospheric conditions and operator error in making the runs. It's probably 10 hp and maybe about the same amount of ft./lbs. of torque.

This is also very consistent with the rating of the Infiniti QX-56, which is 315 bhp with the very same engine. There is no evidence that the Infiniti has anything different in the engine, ECU, its mapping, its intake or its exhaust. The only difference is that Nissan recommends 91 octane or higher fuel.

It seems logical and the evidence collected on the other threads here seems to confirm that, indeed, you can get 10 more horses with 91 or better fuel.

Now, having said that, if you don't redline the engine when you shift, or you are not towing a heavy load, this will never be seen and will be a waste of money.

But, if you want to hook up with a Ram Hemi or take your truck to the strip for any reason, there is probably a reason to start running premium and give it time for the ecu to acknowledge the octane increase and let the timing advance.

BTW, ten horses probably will not amount to even one tenth improvement in either 0-60 or in the quarter mile, but might make a difference in a race where inches matter.

[Half Shovel]

I would bet there is some difference between the Infinity motor and the Titan motor. Might be a different cam, with a little more peak HP and less low end torque. Might be a slightly different programming in the ECU, might be a slightly different intake.

In my mind, it does make sense for Nissan to spend a few bucks to differentiate the Infinity product from the Nissan product. I would think that would be a good thing when marketing a vehicle that costs a LOT more than the virtually identical Nissan product. Ya gotta give 'em SOMETHING to brag about.

just my opinion.

HS

[lizardking]

I agree with HS, Infiniti would have done something different with the engine and I believe if you search you will find what they did different.. There was something posted about it a few months back.

[Titan Power]

I'm willing to bet there is nothing different then the recommended octane, and the plasic ornament on the engine cover. A while back someone incorrectly stated that the Infiniti had a higher compression ratio. It does not, 9.8 to 1, same as the Titan/Armada...

[url=http://www.infiniti.com/content/model/ModelSpecifications/0,,75031,00.html]

Also notice that there is not a trade off of torque for HP, it is up a few ft.lbs. also. Since the compression ratio was not raised, then there should be no "need" for higher octane fuel. The higher octane is to allow for more timing advance, pure and simple.

The only thing I am unsure of is why there is a different torque rating for the Armada and the Titan. There may be a slight change to account for this difference, either in tuning or cam profile, but I doubt it. Even so, my arguement still stands that the Armada and QX56 share the exact same engine. Here are the ratings for all three...

Titan 305hp@4900rpm / 379ft.lbs.@3600rpm
Armada 305hp@4900rpm / 385ft.lbs.@3600rpm
QX56 315hp@4900rpm/ 390ft.lbs.@3600rpm

All peaks are at the same rpms, which makes cam or intake tuning changes less likely. Of course, we all know the engine is underrated, and those numbers are artificial. The differences may be due more to marketing then engineering, and comparisons could be meaningless.

Jason K.