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Some are saying the 91 octane tune is better than the 93 octane tune. That doesnt make sense to me, as I though the 93 octane tune is identical to the 91 tune except for advancing the timing some for the higher octane fuel. The end result would be more hp and torque with the 93 octane tune assuming you have 93 octane fuel.

Some are using 93 octane fuel with the 91 octane tune as they are seeing more power.

To quote someone "348rwhp with a standard 93oct cai tune and 357rwhp with a 91 oct cai tune." This was what they found on the dyno.

Any ideas why this might be? Isnt the only difference timing, or is there a problem?

2009 Dodge Challenger R/T

Good question as I am wondering the same thing. I was using the 91 Octane tune but since I can only get 93 Octane I switched and I think the 93 runs better. I hope this can be cleared up as it is a confusing.

JA

Very simple. They're getting knock on the 93 tune, which is causing timing to retard. That knock isn't there on the 91 tune, which allows more timing and more power.

which one would be the better tune to go with?

What Mike said is correct.
There are different qualities of 93 octane fuels, from personal experience i have found Mobil, Sunoco and Amoco/BP to be superior quality fuels.
So it also depends on how good your 93 octane fuel is, poor quality fuels will cause more detonation and thus reduce performance due to the detonation (well actually the pcm thinks it is detonating and removes timing) and timing being pulled so you are most likely running less timing than what would come in the 91 octane tune.
Hopefully that makes some sense.

jara97 wrote:Good question as I am wondering the same thing. I was using the 91 Octane tune but since I can only get 93 Octane I switched and I think the 93 runs better. I hope this can be cleared up as it is a confusing.

JA

That is what I have been reading.

Correct me if I am wrong, but isnt the only difference between the 91 and 93 octane tune, the timing? They are identical in every way, in fact probably just a copy, except with the 93 octane tunes it has the timing increased a couple of degrees?

Yup.

Okay so basically if I read this correct either will not hurt the engine. How do I know if the engine is knocking? It ran good on 91 with 93 fuel since 93 is all you can get here. I changed as I was concerned about running the 91 tune with 93 fuel. 93 seems also to run good and maybe with just a small amount of added power but not quite as smooth at idle.

I am not familiar with how to use the predator to check these things. Main concern is only to run what will be okay for the engine. Vehicle runs very strong with either tune.

james

Here's a simple rule:
On a 91 tune, use 91 or better. On a 93 tune, use 93 or better.

It won't hurt anything to run better octane fuel with a lower octane tune i.e. 93 gas with 91 tune.

In fact, that is why some are getting better numbers, running it this way, because some fuel is just crap no matter what octane rating. (like what Johan and mike were talking about)


Any luck on an 89 tune? I can't get 93 and the 91 around here is terrible.

hmmmm u know what i am noticing. I get knock on 91 and 93 octane and im running shell 93 fuel??? I install the stock tune and it runs fine, as soon as i run either diablo tunes i get a knock like at 40 to 50 mph, that is when i give it some gas???

don't EVER use shell gas!!! that's the problem right there!!

shell is shit fuel man... get rid of it... run that tank out as low as you can, then fill up with 93 octane mobil, exxon, sunoco, amoco or bp....

do NOT use Shell gas - never never never never.... bad shit...

I haven’t had any problems with Shell, but I got a lot of knock using Chevron.

Same with me Hemitx... But still Shell wasn't good enough for me, so I now go with AM/PM gas which is BP... Plus they are usually 5-10 cents cheaper per gallon than everyone else...

I was told that exxon has like 10% ethanol. Would that cause any problems with our cars that are tuned? You know i had been running on shell gas im wondering if that was giving me the knock. hmmmmm

We don’t have BP/Amoco or Sunoco in Dallas so I’ll have to give Exxon a try. All gas here is 10% ethanol.