SCT Tuner 87 to 91 octane results - Ranger-Forums - The Ultimate Ford Ranger Resource


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Old 12-29-2014
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SCT Tuner 87 to 91 octane results

I currently have a SCT tuner with an 87 performance tune done by don at lasota racing. I am very happy with the tune and don is great to work with. How much of a performance increase will I be looking at by switching from an 87 to 91 tune? Now that gas prices are dropping I am considering getting another tune from don. Will MPG change at all?

Also, for those that have 91 tunes, is there any 'noticeable' difference? Thanks for the help.
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Old 12-29-2014
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The octane of the fuel, of course, doesn't matter, 87 to 95 have the same energy per gallon.
But with higher octane you can advance timing a little more without getting the pinging.


Your '04 4.0l SOHC should have a Knock sensor, not sure if they left that active or not, if it is working you may notice a difference just by using 91 octane.
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Old 12-30-2014
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I don't know if that was left active by don or not either. Anyone know what kind of real world hp increase I could expect? 2-3 hp?
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Old 12-31-2014
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There would be no HP increase, octane is a heat rating not power.

Your '03 4.0l SOHC has a compression ratio of 9.7:1, which is marginal for 87 octane(9.4:1 is edge of 87), even 89, which is why there is a Knock sensor used, this "allows it" to run on 87/89 with retarded spark timing.
91 octane would be best any time.
Your performance increase would be more advanced spark timing, the Knock sensor doesn't activate so computer can maintain a more aggressive advance.
If you don't have pinging/knocking during acceleration with 87 octane then knock sensor is active, or programmer did some odd spark advance timing.

Unless you had a dyno to use there is no way to say what, if any, HP increase there would be
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Old 12-31-2014
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I can give you some acceleration comparisons with an SCT that was programmed by BAMA many years ago. I don't know how it will compare to your programmer.

To eliminate tire spin and shifting errors I did an acceleration test in third gear from 40 to 70 mph and from 50 to 80 mph. I will just give you the performance gains over the stock program.

With the 87 octane performance program I knocked off 0.7 seconds from 40 to 70 mph and 0.45 seconds improvement from 50 to 80 mph compared to the stock program.

With the 91 octane performance program I also knocked off 0.7 seconds from 40 to 70 mph but improved to 1.2 seconds less from 50 to 80 mph compared to the stock program.

This resulted in no improvement for 40 to 70 mph with the 91 octane performance program compared to the 87 octane performance program. However there was a 0.75 second improvement from 50 to 80 mph with the 91 octane performance program compared to the 87 octane performance program.

That tells me there are some hp improvements at higher rpm with the 91 octane performance program compared to the 87 octane performance program but not so much in the lower and midrange rpm. That leaves me running the 87 octane performance program 99% of the time.

I found there is a little mpg to be gained by running the 91 octane program if I keep my foot out of the go pedal but it is less than 0.5 mpg.
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Old 01-02-2015
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Originally Posted by IN2 FX4 View Post
I can give you some acceleration comparisons with an SCT that was programmed by BAMA many years ago. I don't know how it will compare to your programmer.

To eliminate tire spin and shifting errors I did an acceleration test in third gear from 40 to 70 mph and from 50 to 80 mph. I will just give you the performance gains over the stock program.

With the 87 octane performance program I knocked off 0.7 seconds from 40 to 70 mph and 0.45 seconds improvement from 50 to 80 mph compared to the stock program.

With the 91 octane performance program I also knocked off 0.7 seconds from 40 to 70 mph but improved to 1.2 seconds less from 50 to 80 mph compared to the stock program.

This resulted in no improvement for 40 to 70 mph with the 91 octane performance program compared to the 87 octane performance program. However there was a 0.75 second improvement from 50 to 80 mph with the 91 octane performance program compared to the 87 octane performance program.

That tells me there are some hp improvements at higher rpm with the 91 octane performance program compared to the 87 octane performance program but not so much in the lower and midrange rpm. That leaves me running the 87 octane performance program 99% of the time.

I found there is a little mpg to be gained by running the 91 octane program if I keep my foot out of the go pedal but it is less than 0.5 mpg.
Thanks for the real world numbers, its very helpful. I think I am going to try out a 91 tune, and see how I like it
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Old 01-30-2015
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Well I decided to pull the trigger and get the 91 octange tune from Don Lasota, who is always a pleasure to deal with. I have to say I am impressed and recommend it to anyone.
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Old 04-01-2015
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looking at his website I would pick the 100% stock email tune thats $50 right? Also how did you install it I have no program but can just hook up to computer with printer cable. I have a first gen x3 w/o preloaded tunes.
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Old 04-01-2015
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looking at his website I would pick the 100% stock email tune thats $50 right? Also how did you install it I have no program but can just hook up to computer with printer cable. I have a first gen x3 w/o preloaded tunes.
Yes that is the tune you select, assuming you have a mostly stock engine. He will e-mail you instructions, but basically you go to the SCT website, update your X3 to the newest firmware, download the SCT program, and then Don will e-mail you the tune. You just upload this to the SCT software, then plug in your X3 to your computer to put it on your X3.
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