Compression Ratio/Detonation Control

[CcanDo]

Base line for 93 octane, supercharged, 5# boost, 8.5 compression initial, is said to create 12 to 12.5 final compression, safely. However, the rule of thumb seems that 12 to 1, non supercharged is not safe. Why not? If the answer is only timing, then where/when does concern start, at some number on timing, RPM, fuel to air or all the above? In other words, elecronics shouldn't be able to control and issue commands to safely operate a 12 or 13 to 1 NA engine ???

[1997bird]

What is your quench area? What type of engine are you running this on? Are you running this project on EFI or is it carb'd?

[Awesome Bill]

Super chargers or turbos can get away with 12/1 final but that is not static. Starting with 8.5:1 then ending up @ 12:1 is a safe tune up. Pump gas is not as bad as you might think. The problem is when you start @ 10:1 and end up @ 14:1. Boosting is 5 times safer because with added fuel, the charge does not heat up and then goes off by itself with pre ignition or detonation. There is a difference. We have seen many 12 and 13 1 compression boosted engines run safely with pump gas. Over that you will have to have a cooler air charge and some electronics. Too much timing always is what caused engine problems. I tend to stay 4° retarded from peak power for street cars.

To answer your question about static 12:1 verses boosted, pump gas and 36° timing with anything over 11:1 static you better have your combustion chamber, exhaust ports all working well. Pump gas works very good to that point naturally aspirted. After that it can be done but you have to be careful. I will always take boosted compression over static becasue air is power, fuel is introduced to burn the O2. Thus the reason boosted will always make more power than naturally aspirated @ best Pro Stock Conditions!

[bajabob]

billso on the timing .naturally aspirted 540 ,pro1 heads comp all most 10 to 1 . 36dg. is ok .how do you know how much more you can time your motor?