farmtruc

[mopower440]

Between these 2 tunes, what would be more power: a single 89 octane tune OR a dual 89-91 octane tune? I have a 91 tune now, if I. Stepped down to a 89/91 dual tune, how much power and torque would I lose?

[Erica@NP]

Between these 2 tunes, what would be more power: a single 89 octane tune OR a dual 89-91 octane tune? I have a 91 tune now, if I. Stepped down to a 89/91 dual tune, how much power and torque would I lose?

With the 89 oct tune you will lose about 7 or so HP to the wheels. If you did the dual tune it would have both the high and low octane tables tuned slightly different so depending on the grade of fuel you decided to run your ecm would adjust.

[mopower440]

Alan, will you explain to me why a single octane tune is better than a dual? Currently i have a 91 octane tune from you. I was thinking of changing it to a 89/91 dual tune because 91 is so much higher here than 89. So, why would the SINGLE 91 octane tune do better than a DUAL 89/91 tune as long as i am running 91 octane with the dual tune? I can understand it not being as good if i run the 89 octane fuel, but if i use 91, like when im towing, why wouldnt the dual 89/91, do the same as the 91 single? Just want to understand. cant you make the 91 table of the dual tune the same as the 91 table of the single tune? Let me know asap because you are doing a retune for me because of a battery light and i told Erica to do a 89/91 this time but i want to be sure first so awaiting your explanation so i understand..lol.I sent you a pm also.Thanks for yours and Ericas help with all this.
Thanks
chad

[kerrige]

Two tables exist. Low and high. Timing is better in the high table. It is more aggressive resulting in more power. If you have a single Oct tune both are the same. With a dual tune the low timing makes as Erica said roughly 7hp less. If your truck happens to think you have 89 if will have 7hp less. Even if you have 91 in the tank the pcm may think you have 89 and you will make less power. The single while using 91 all the time you make all the power all the time. With the dual tune it will and can change and make less power at times.

[mopower440]

Two tables exist. Low and high. Timing is better in the high table. It is more aggressive resulting in more power. If you have a single Oct tune both are the same. With a dual tune the low timing makes as Erica said roughly 7hp less. If your truck happens to think you have 89 if will have 7hp less. Even if you have 91 in the tank the pcm may think you have 89 and you will make less power. The single while using 91 all the time you make all the power all the time. With the dual tune it will and can change and make less power at times.

Understandable. But as long as it does have good gas and doesn't detect any knock, will the dual tune run on the 91 table and put out the same power as the single 91 tune?

[Erica@NP]

Understandable. But as long as it does have good gas and doesn't detect any knock, will the dual tune run on the 91 table and put out the same power as the single 91 tune?

That is correct.

[mopower440]

That is correct.

Hmmm, ok, Allen acted like it still would not perform as good as the single tune even with good gas and no knock, that's why I didn't know

[kerrige]

Understandable. But as long as it does have good gas and doesn't detect any knock, will the dual tune run on the 91 table and put out the same power as the single 91 tune?

Yes however any false knock can send it into low octane.

[mopower440]

Yes however any false knock can send it into low octane.

I see. That makes sense. If I have a straight 91 tune and it detects false knock, what does it do?

[GMCwantsLS1]

I see. That makes sense. If I have a straight 91 tune and it detects false knock, what does it do?

It will reduce timing during that knock event but will remain on the same timing tables. That is what is best about single tune, it will still correct for spark knock on the fly but still try to add as much timing as possible.