106 vs 100 octane

[BSB67]

A cranking compression test won't really tell you much, other than if some cylinders are weak. Won't give dynamic CR which relates to detonation in my understanding. I used to mix aviation gas with pump premium before race gas was readily available. 100 octane AV gas allowed more than 11.5:1 with iron heads.

Cranking pressure is better measure of detonation potential than DCR, IMO. It is a real number verses a theoretical number. They both have variables and there is always a "gray zone" where the specifics of the motor, car and quality of tune will make a difference.

DCR calculators also calculates a cranking pressure, and they are directly proportional. A DCR of 8.0 always derives the same cylinder pressure.

All of those DCR calculators have more variables than a actual cylinder pressure test. There are actually three different formula for calculating DCR. The part that is funny to me is that some DCR calculators use 0.050" cam lift.

At the end of the day, DCR is a theoretical tool applied to do some derived guidlines. In the hands of the right people that understand these details it is useful information.

 

[Johnpat]

You may want to look up Boostane octane
booster.
It doesn't separate when setting in fuel tank
like a lot of other boosters

 

[jamie]

Compression heat may be the biggest factor. There are a million variables to understanding this and it has been a big debate for years.Compression testers will read differently due to temp,cranking speed etc.

Forged pistons are way more forgiving then cast or hypereutectic.Detonate with those and you may find them in the bottom of the pan. If it is 11 to 1 , do a proper cranking compression test,if it is 190 or under (generally speaking) you will be safe with 100.

 

[66Satellite47]

Cranking pressure is better measure of detonation potential than DCR, IMO. It is a real number verses a theoretical number. They both have variables and there is always a "gray zone" where the specifics of the motor, car and quality of tune will make a difference.

DCR calculators also calculates a cranking pressure, and they are directly proportional. A DCR of 8.0 always derives the same cylinder pressure.

All of those DCR calculators have more variables than a actual cylinder pressure test. There are actually three different formula for calculating DCR. The part that is funny to me is that some DCR calculators use 0.050" cam lift.

At the end of the day, DCR is a theoretical tool applied to do some derived guidlines. In the hands of the right people that understand these details it is useful information.

+
Your point about DCR is valid. But cranking pressure is still subject to the big variables of cam grind & temp. The .050 is for consistency in cam profile comparison. Overlap is a major factor IMHO.

 

[1967coronet440]

Good stuff here also

https://www.jegs.com/i/Race-Gas/814...8HelGntsoURfFxIvjIqlu0nfTccHO64RoC-2YQAvD_BwE

 

[biomedtechguy]

Good stuff here also

https://www.jegs.com/i/Race-Gas/814...8HelGntsoURfFxIvjIqlu0nfTccHO64RoC-2YQAvD_BwE

*per GALLON of gasoline