Commander316

this is what i like to hear... the tune is out of the question until warranty goes out and i get the truck paid off though..

TuxBlackEB

I see what you mean, too. Makes me wonder if I should also try the 87 tune in a couple of weeks and see how it compares. Looking more closely at the graphs now, if you take away that brief spike, the 87 tune outperforms the 91 tune during the majority of the torque curve. I like your analysis.

sluggo1

Isn't there also an 89 octane tune that they offer? Thought they had 87, 89, 91, 93 and tow tune...would be curious to see how 89 plays into this debate

engineermike

A high initial peak and slope downward is actually an ideal torque curve. It gives you more torque for any given hp, and will outperform a flat torque curve in any situation. Where problems come in is with "holes" or valleys in the curve, like a 2-stroke dirt bike might have. The 91 octane curve appears to have this at 3700 rpm, but I tend to believe that it's a dyno anomoly or tuning oversight, as there is no technical reason 87 and 93 tunes wouldn't do that but 91 would.

TuxBlackEB

That makes since. I noticed that the baseline run with the 91 graph seemed to follow a similar torque curve with the exception of the spike, and was not as flat as the curve from the 87 tune's baseline run. Also, it seemed that the 87 made more torque throughout the powerband than the 91, which didn't seem right. I suspect also that it had something to do with the Dyno. Maybe Livernois can do a new pull with the 91 and post the graph.

Out here in sunny CA, the highest octane available at most gas stations is 91. After seeing the graph, I was leaning toward trying out the 87 tune, but your explanation made a good argument for the 91 tune. The best part about Livernois is that it's free to bounce between the tunes, so this is a happy dilemma.

Buck

How does it give you more torque for any given horsepower when its consistently losing torque as the rpms rise? I'll take a tune that holds its torque longer and delivers it smoother anyday. The 93 isn't bad. But I still like the 87 curve better.
In the school that I came up in a nice smooth flat torque curve that held as long as possible was always preferred and what tuners strived for.
If the valley in the 91 torque curve is a tuning oversight then that's still an issue and I would still prefer the 87 tune over it based on the graphs. The 87 graph is still the best looking graph to me. A little less power yes...but looks to be a more refined tune.

Buck

I'm not impressed with the 91 torque curve AT ALL when compared to the other two. The nice thing is that you can try both without any added cost and see which one you like most. I'm in the same boat as you....no 93 at the stations here. High elevation. We have 85, 87, 89 and 91 octanes.To get 93 or higher you have to go to a specialty shop/station.
From my analysis I would lean towards the 87 for day to day (plus its cheaper) But I'd give the 91 a try to see how it ran.

engineermike

It's a mathematical certainty! If two engines make an equal, say, 400 hp at 5000 rpm, then they will also make an identical 420 ft-lb at 5000 rpm. If one has a perfectly flat torque curve, as you guys desire, it will also have 420 ft-lb of peak torque. If the other has, say, 840 ft-lb at 2000 rpm, then its torque curve will slope all the way down from 840 ft-lb @ 2000 rpm to 420 ft-lb @ 5000 rpm. This will create a very steep slope down, but will win in a drag race and towing in every situation, and it's what I'd prefer.

With the Livernois 93 tune, not only does it beat the 87 tune by 45 ft-lb down low, it wins by 18 hp up top. Any time your gains are greater at low rpm than high rpm, the curve has a steeper slope down. Many would argue that in a truck, the low end gains are more beneficial than top end, and the 93 tune does just that.

Buck

I don't need a 2+3=5 math lesson.
I understand what you are saying however you are over exaggerating the numbers to make your point. In your scenario its obvious that something that makes way more torque then gradually drops off to make the same torque at 5000 rpms as another tune is going to be superior. My point is that this 93 tune is not superior enough to make your point as solid as you think. The claimed 45 ft-lb advantage lasts for a grand total of 300 rpms...hardly substantial. The rest of the time it has a 10-15 (maybe 20 in spots) ft-lbs advantage. Its not as superior as it looks. The low end gain over the 87 (+45 ft-lbs) is not consistent...I want consistent linear torque. I don't give two ****s about drag racing a truck. I want a tune thats smooth, consistent and linear. The 87 tune does that better. I'm not saying the 87 tune is more powerful than the 93 tune. I'm just saying the 87 tune looks to be a better tune IMO. Maybe more time could be spent on the 93 tune to refine it? I don't know.
I've been around the dyno tuning game for a while with my ATV and I've seen run after run where ATVs with less HP are able to win drag races over other bikes due to the way its tuned and how the torque is put to the wheels. Its not always about the bigger numbers.
Yes, a curve that has more torque than another curve is what it is....more powerful...But...Numbers aside, to say a torque curve that gradually drops as the rpms rise is better than a torque curve that holds smooth and steady throughout the rpm range is ridiculous.

engineermike

Pick any peak torque number you want over 420 and the point is still valid.

So, you want them to "refine" the 93 tune by reducing the peak torque by 20 ft-lb and then you would be happy because the gains would be more "consistent"?

That usually happens when the one with less hp has more low-end torque.

As long as the peak hp is the same or better, a gradually dropping torque curve will always be better.