Hey guys, i just looked up what octane is recommended for these trucks, and it said 87 octane. What the hell's up with that?? I thought it was 91 or 92. Anyone using 87?? If so, does it ping at all or make any noise? I probably will never use 89, let alone 87, i figure this nice of a truck with the performance it puts out deserves some good gas. Thanks for the replies.

 

Sounds as if you didn't read your SVT supplement for your manual It's 91 minimum.

BfB

 

87 sounds low to me too but Ford Specs state an 8.4:1 Compression Ration which would do just fine with 87 or even lower Octane fuel.

http://www.svt.ford.com/flash/bottom1lightning01.html

 

Go ahead and try 87 octane and put the pedal to the metaland watch your engine let go.

Forced induction(Superchargers, Tubros) require a lower compression ratio.

If you "O" ring the heads and have some killer heads, pistons etc. best of the best parts you should be able to up the compression some.

And yes the 'Ls REQUIRE higher octane.

 

jarmstro,

Yep, I looked into it a little more and it does require premium fuel.

Thanks.

 

Okay, here's the scoop.
At the factory, all Ls PCMs are calibrated for 87 Octane, even though your manual and the dash board etc.. say 91. For d figures that a few people think they know better and will spend 32K on a truck and then try to cheap out on $2.50 a tankful on the gas, so they failsafe it.

the good news is, your dealer can recalibrate it to whatever octane you want. The bad news is they won't, unless, you go in and tell them A) that they can, most have no idea they can, and most won't because they figure they may assume some liability if they change the factory settings,
so, to get them to do it, you nned to compalin about pinging undser load. there is a TSB for that, they can change it and everyone is happy.

Now, before someone goes and has it set for 110 octane, know this, setting it for a higher fule than you use is just as bad as it being set for something you don't use lower. IE if you have it set for 110, be prepared to pay $5 a gallon at the airport for EVERY TANK, have it set for 91, 92 or 93 (whatever you use) 'cause that's where it's gonna run best.

Hope this helps,

G

 

That is so not true, right???, and I really hope a tuner like PSP or JL tunes in here.

BfB

(there, that's better...hehe, yeah, it did sound as if I "knew" that wasn't true and then stated I didn't by asking for a tuner's advice)

 

'Ragno:

Whenever the topic of "octane ratings" rears its ugly head, here I am. Poorly, if at all, understood topic by the public-at-large, and one that really gets me annoyed, usually.

I'll try to be gentle and polite, but "your mileage may vary", as they say.

First of all, if you believe that low-octane gas will be just fine in you 'Bolt, based on something you read off a spec sheet on the internet, then by all means go for it. In fact, mix in a little kerosene and drop the octane rating to around 82 or so - it should be just fine with that low, low 8.4:1 compression. Funny how the Lightning makes such incredible power with such a LOW compression, isn't it? Perhaps the folks at SVT are in tight with the BMEP (brake mean effective pressure) gods, or something, in order to stretch the well-understood physical laws to their limits like that.

All right, before you return your engine to the "ore state", as my man Kurt Vonnegut once put it, let me fill you in on the compression thing. Really, compression is just an analog for "peak cylinder pressure", which would occur at TDC (top dead center) if you killed the spark to the cylinder. As the pressure rises (and consequentially, heat), all of the fuel molecules are banged around and into each other with more and more energy, possibly to the point where they just can't STAND it any longer and they AUTOIGNITE! This is knocking/pinging. A fuel's octane rating is simply its resistance to autoignition (knock) as measured in a standard test engine. NOTHING ELSE!

The higher the fuel's octane rating, the more severe pressure/heat conditions it can withstand before autoigniting (knocking/pinging). Now let's wrap this all up as it pertains to the Lightning.

Keep in mind that this is all about pressure (and heat) in the cylinder. We're going to have to make a few simplifications to make this discussion workable (and not degenerate it into a graduate-level thermodynamics class, which I have incidentally suffered through). Let's assume that the ideal gas law applies, and that somehow we have an isothermic condition within the cylinder (we can somehow instantly soak up all of the heat of compression). Thus simplified, basically the product of volume and pressure will be a constant. Halve the volume, double the pressure. Cut the volume by a factor of 8.4 (as is the case with the 'Bolt), multiply the pressure by 8.4. Really, this isn't a bad assumption.

Anyhow, the atmosphere around us is at around 14.7 PSIA. Compress it 8.4:1 in the cylinder, and you have around 123 PSIA. Hovever, with our supercharger, we are developing some amount of boost over atmospheric pressure. Let's work the case for the advertised 8 PSI of boost. You would then be compressing the air/fuel mixture in the cylinder, starting at (14.8 + 8 = 22.8 PSIA) 8.4 times, giving a peak cylinder pressure of almost 192 PSIA. This would be the equivalent of 13:1 compression in a naturally aspirated vehicle, and is the obvious reason for the "91 minimum" octane requirement. If you're generating 13 PSI of boost through modifications (pulley and intake), you're looking at something like 16:1. Better run the "good stuff".

In actuality, the "effective compression" numbers aren't quite that severe, as the cooling effect of the intercooler will help to reduce the ratio a bit. It would quite difficult indeed to run at an equivalent 16:1 on any sort of pump gas.

Anyway, does this make sense? It's about the pressure in the cylinder, and the supercharger boost increases the "effective compression ratio" substantially.

Makes you wonder about tooling around with a dry intercooler circuit and the 'charger engaged, doesn't it?

 

BfB: I wouldnt just patently dismiss Factory_Tech's claim, but you are right, I would like some tuner input on this.

 

It seems like everyone has a point. Everyone has information to back up what they're saying. I think someone should give SVT a jingle and ask them. If anything, they'd be the ones that would know for sure.

 

Yo, Silver-Y2K-SVT:

Please address the earlier assertion that you can have a factory tech change the onboard computer to be calibrated to, say, 92 octane instead of the factory default of 87. What sayest thou to this?

 

'Bolt:

There is indeed a provision in the "bowels of the computer" to set some sort of "octane setting". This is in the same place where you can compensate for the gearing and a few other pameters.

One of the Georgia contingent reported on this a while ago (last summer).

I'm not sure what effect adjusting this parameter has - I suspect very little. Some have had it adjusted, with presumably no effect (or we would have heard about it, I suspect). I went to my dealer in a panic with the thread in hand and they practically laughed me out of the place. I'm not sure what to think of that - they are, for the most part, idiots - however, the internet is also about the WORST place to do "technical research" (don't get me started on the topic of "internet research").

I also am REALLY interested to hear what the tuners have to say about this, if anything. I'll be watching this thread like a hawk. I suspect that they have figured out EXACTLY what this parameter controls.

 

I am not sitting in my '99 Lightning right now, but does it not specify using premium gasoline in the instrument cluster in the dash?

 

Yes.

This whole topic is a moot point if you run a chip.

 

DB:

How's that? Depending on the tuner and your needs/desires, you could get a slow, low-power chip that would allow your 'Bolt to run on charcoal lighter (100% blower bypass, 30 or 40 degrees of ignition retard) or, on the other hand, require straight toluene (or propane) at 130 octane (very lean fuel curves, massive ignition advance).

How does getting a chip make octane requirements a "moot point"? I would venture that is becomes a MUCH bigger issue with any "typical" chip that folks on this board have or are considering (which make power by leaning out the mixture and advancing the ignition).