Compression Ratio/Detonation

[CcanDo]

Assuming it is safe to use an initial compression ratio of 8.5 to 1 and 5# of boost for a final of 12 +, on 93 octane, why is not accepted to run 12 or 13 compression, naturally aspirated ?

[tcuda499]

Because the lower compression of a blower motor will run cooler and help limit some detonation. also, Quence factor will reduced requirement for octane. Quence is the distance between the top of the piston and the flat part of the combustion chamber. This design limits the detonation potential of your engine.My opinion is 12.5 for pump gas on a blower motor.

[CcanDo]

Would an inverted dome piston, open duration cam and reduced timing be enough to make it safe ? What RPM would be a baseline point to start reducing timing ? Then, at some point, would introducing better fuel be feasible, allowing for advancing timing ?

[Young Performance]

You won't be able to get 12.5-13:1 comp. ratio with an inverted dome piston.
Also, taking too much timing out will likely increase the possibility of detonation. Higher timing will keep the egt's managable. Timing that is too low will raise the egt's, which will cause detonation.
Eddie

[Griff]

8.5:1 with 5# of boost gives an effective compression ratio of more like 11.4:1
http://www.holley.com/data/TechServi...ech%20Info.pdf

[CcanDo]

Originally Posted by Young Performance

You won't be able to get 12.5-13:1 comp. ratio with an inverted dome piston.
Also, taking too much timing out will likely increase the possibility of detonation. Higher timing will keep the egt's managable. Timing that is too low will raise the egt's, which will cause detonation.
Eddie

What would you use for piston design, bear in mind there is some funky stuff being done with the CNC heads. Also, such as Total Power or someone similar is thought to be working on variable valve timing to go with their dual overhead cam....Maybe there will be some insight at PRI.

We will probably build the motors with superchargers of some flavor. However, we also have two Sterling Supercat engines that came out of US 1 that need to be freshened. Perhaps there is some opportunity to use dual fuel and keep the compression up on those engines. In fact, we've wondered if those engines should be first.

Your help is appreciated.

[CcanDo]

Originally Posted by Griff

8.5:1 with 5# of boost gives an effective compression ratio of more like 11.4:1
http://www.holley.com/data/TechServi...ech%20Info.pdf

Griff, what are your thoughts on making a high compression, dual fuel engine work, safely.

[Griff]

Originally Posted by CcanDo

Griff, what are your thoughts on making a high compression, dual fuel engine work, safely.

I just don't see the need when there are plenty of other proven options out there for supercharging.

[ezstriper]

not to mention in most cases you are going to be running less timing with the blower set-up that you would with the higher compression N/A set-up..Rob

[CcanDo]

There are actually two sets of engines involved, a set of Supercat Sterlings, we have, and a set of supercharged to be built after PRI.

The Sterlings are 12:1 engines and shouldn't run on 93 Ethanal. However, E 85 may work. Unfortunetly, E85 may be hard to find on the water or otherwise. Therefore, w/ fuel injection supporting the present carbueration and electronics, one looks at how feasible 93 in one tank and E85, or other, in the second tank, may be. The engine would run on 93 to a theshold on carb only, then the injection/E85 would turn on.

Moral is, this dual fuel thing is about looking for a method to run a good engine, safely on tomorrows junk fuel that may be at the dock.