MustangGT0405

I agree with CK and JagKing.

The chart is apples to oranges due to whats mentioned above, but as CK stated he knew that. The real point is that the higher boost you want to run with pump gas the more you have to lower the engine compression.

Someday I hope to install a forged SB and run 14psi on pump gas. The SB will have pistons that give me approx 8.5 - 1 compression. I will then have it professionally tuned for 93 octane. Notice I didnt make a power prediction. I will be happy with whatever that combo provides.

So from my understanding from this thread here is the simple answer.


Increase Boost / Decrease Compression

HaneyMotorsport.Com

There are a bunch of variables that come into play.It is really all about cylinder pressure......why some guys are blowing up WithOut having any knock. As stated, the rods are the weak link in the 3V.

You will always make more power with a higher static compression....for both n/a and boosted. Of course it will depend on what fuel you use.

Casey

modaddict

Yep - you guys are right on the money. It wasn't a chart for our cars - I wish I could find one...lol

It was merely a reference. My main concern is the way the knock sensors and tuning works is to account for detonation when it happens. Knock sensors pull timing when detonation is detected, so some detonation is still happening before it's being dealt with. Granted - this may be minimal, but then again - it may not and my philosophy is any detonation is BAD.

The guys saying they are running around with x amount of power saying they don't have detonation - my question to them is - how do you know? Your computer may be pulling the timing when it detects detonation you don't know about so just because you don't notice it - doesn't mean it's not happening.

I could be way off - but this is my thinking anyway...

I would just like to have some definitive facts like the chart that relates to our cars. That would be awesome but I couldn't find anything anywhere. I know there are a lot of variables but I'm sure the data could be compiled somehow.

jaguarking11

Fuel has allot to do with it.

For example, if e85 were freely available in every state carrying the same price as gasoline, I would build an engine diferently. To keep the response high I would increase compression to 12:1 and run only 6-8lb of boost, that should net the same hp as 10 - 14lb of boost on a stock engine.

However this being the world that it is, I don't see e85 becoming more than a temporary alternative.

CataclysmGT

I said it before, you can datalog knock sensors.

matyellott

Agreed

modaddict

True but that's only good for the time of the actual datalog, right? So, unless you logged your sensors every time you drove the car, you'd be hardpressed to say for sure you weren't getting any detonation. Pretty expansive gamble IMO. (if you're running high boost with low octane I mean)

CataclysmGT

Again, there are lots of factory cars running 10+ psi......
If you datalog in the highest heat condition possible, and experience no knock.......its doubtful you will ever see it under any other condition, save bad fuel. Bad fuel can ruin an N/A motor.......

Phya

The whole point is to avoid detonation. If you're not getting any detonation running 10+psi on pump gas, then great. If you avidly want to deny that running a higher octane to make up for it is not a productive idea then by all means, go for it.

I guess..would you run 87 octane on any FI induction system if you have higher octane available in your area? I wouldn't.