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Discussion Starter #1
Is it possible with aluminum heads and proper cam? Our gas is crap here in Phoenix but I have ran across guys claiming they are at as high as 11:1 on our 91 swill.
I've tried 10.5:1 on two very different engines and both pinged on 91 and wouldn't take much total timing.
 

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I’ve found that if you can keep coolant temps 180* or below it helps with pinging on pump gas.
 

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Discussion Starter #3
Not happening in Phoenix heat with AC running. It sucks.
 

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12:1 and 93 pump gas here in mississippi... trick is to get a cam that bleeds off cyl pressure.... now yes you are bleeding away power too... so find the balance..
 

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Is it possible with aluminum heads and proper cam? Our gas is crap here in Phoenix but I have ran across guys claiming they are at as high as 11:1 on our 91 swill.
I've tried 10.5:1 on two very different engines and both pinged on 91 and wouldn't take much total timing.
Just adjust the timing accordingly
 

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I remember "in the ol' days" a buddy built a '65 Mustang and a 289. He was running 13.5:1 compression and simply drove it around on the street for years on 91oct, no issues. Of course the cam was almost .700 lift and had over 310* of duration at .050 but.....

ks
 

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Is it possible with aluminum heads and proper cam? Our gas is crap here in Phoenix but I have ran across guys claiming they are at as high as 11:1 on our 91 swill.
I've tried 10.5:1 on two very different engines and both pinged on 91 and wouldn't take much total timing.
The Coyotes run 11:1 and 12:1 don’t they? Aren’t they “tuned” from the factory to run 91 octane? Apples and oranges I know. But still aluminum heads, 11:1, and daily driven. My ‘17 Titan has 11.2:1 compression and it runs on 87 octane.
Was your 10.5:1 car “tuned,” or you just adjusted the timing at the distributor? Maybe look into a “good tune” that doesn’t run too much timing?
edit
I guess the new vehicles with “high” compression have variable valve timing events don’t they? On the other hand there are cars running 9:1 n/a that add 8 psi which raises compression to something like 14:1 on 91 octane that don’t ping after tuning.
 

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Discussion Starter #8
Boosting an engine effectively raises the compression ratio?
It sounds like raising the cr on an engine and not having the octane to support it is not a win. Backing the timing off negates any assumed gains.
 

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Boosting an engine effectively raises the compression ratio?
It sounds like raising the cr on an engine and not having the octane to support it is not a win. Backing the timing off negates any assumed gains.

Ideally you want 0 deg advance, perfection

so think about why Advancing timing is needed
 

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As long as you are willing to unsubscribe to the "I have to get ALL the HP possible out of my engine" mindset, a tuner can reduce timing in the right spots and add fuel in the right spots and the engine won't rattle itself to death.
 

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Discussion Starter #12
As long as you are willing to unsubscribe to the "I have to get ALL the HP possible out of my engine" mindset, a tuner can reduce timing in the right spots and add fuel in the right spots and the engine won't rattle itself to death.
This is something that I'm trying to grasp. It seems the engine usually detonates under load. It's those situations that timing can be backed off in the timing tables. What happens at cruise or WOT?
 

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This is something that I'm trying to grasp. It seems the engine usually detonates under load. It's those situations that timing can be backed off in the timing tables. What happens at cruise or WOT?

Have you looked at them, its self explanatory

think load

and WOT is a function, you will see it in the functions tab
 

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It is amazing what variable cam timing and 4 knock sensors allow the factory hot rods to run for compression on pump gas. And It is not just the timing curve that is being optimized, but also the transition from port to direct injection and back. Direct injection also allows for varying the injection timing to optimize power. It is rather difficult if not impossible to obtain the same results on a conventional pushrod engine.
 

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yea,,,,,,then you realize you only tuned for like 2% of all street driving
Speaking for myself, living in the DFW metroplex:
All the decent tuners are BUSY. You call to discuss a dyno tune and they can't get you on the rollers for 3 months.
So you get your dyno tune and they are so used to working on 1000+ hp cars that your n/a less than 500 hp car is beneath them, and they hurry to get your car of their dyno.
Then about a week later, when your car is not running right, or the idle is erratic, or the car is pinging, you call to get them to "fine tune"it and they can't get you on the dyno for another 4 months.

We have two guys here that do a fine job of road tuning remotely. They beat local shops all year long.
OR learn to do it yourself.
 
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