Detonation on premium?

[Thourun]

At what PSI does detonation usually happen on regular 93 pump gass in a car with 8/1 pistons?

[KC Ron Carter]

Many other factors to consider.

Timing advance or retard, intercooler, air fuel ratio, and last but not least is carbon buildup.

Normally 6 PSI with out fear and 9 psi with controls.

Later,

[-Jayson-]

its all about compression. YOu can have an engine thats NA but has a high compression and if the compression is to high it will detonate on 93 octane. Forced induction increase compression, thats why you need higher octane. So the amount of boost to create detonation is different on each engine. Some engines have a low stock compression while others are high. If the stock compression is high to start with, it prolly wont take much boost to create detonation on 93 octane.

[Evil Result]

Of course you have the ME4-12 which has 9-1 compression with 20 psi of boost.

I heard it stated in a video about the car.

[Thourun]

Ahh I know but how high can a VR4 boost with it's 8:1 compression pistons considering fuel supply problems, cooling problems, physical tollerance problems, and hotspots are not issues? I'm just wondering how high one can boost on 8:1 compression withought using higher octaine.

[02GrandCaravan]

Originally Posted by -Jayson-

its all about compression. YOu can have an engine thats NA but has a high compression and if the compression is to high it will detonate on 93 octane. Forced induction increase compression, thats why you need higher octane. So the amount of boost to create detonation is different on each engine. Some engines have a low stock compression while others are high. If the stock compression is high to start with, it prolly wont take much boost to create detonation on 93 octane.

Keeping this in mind - I have 9.5:1 stock compression in my 97 Saturn SL2. I've been running 93 octane gas for 5 tanks fill ups and on the dyno with the Powerdyne BD-600 pushing about 6 psi I had some detonation between 5600 - 6k rpms.

Is my stock compression a factor in this or would this be a "adding more fuel" fix. Here is a dyno chart that includes the A/F. About 55 - 5600 rpms you can see the line starting to creep back up so I'm wondering if it's just fuel:

[nissanfanatic]

Consider engine temperature, timing retard, A/F ratio, intercooler efficiency, and spark plug heat range. Look into timing retard systems, fuel controllers and upgraded intercoolers. Believe it or not, you could benefit more from a larger turbo at a lower psi than you are running now. Theres really no set number. It varies with each car.

[JekylandHyde]

As stated there are way too many factors beyond just octane and boost pressure to know when/where detonation will begin.

A stock turbo MR2 could safely run 15 psi without detonation on 93 oct.

If detonation is a concern, I would highly suggest water injection.
I would never run a boosted car without it again.

[Zgringo]

As Mr.J&K said, I'd never run a boosted car without water/alky injection.
I'd like to add one more little side note being gas is getting so costly. Ever think of running TOLUENE mixed with gas to raise the octane level?

http://www.easyperformance.com/Octan...rd_Content.htm
http://performanceolds307.tripod.com/id9.html

Albert