5 replies to this topic

[Georgeb91]

Good evening
Was doing a turbo project but have changed my mind so currently got a 1293 block with omega cast 10cc pistons in it. What head cc and compression ratio will I need to run as I'm going to go NA

Thank you in advance

[Dusky]

9.75:1 is a Nice street cr. Depends on the cam.

[Spider]

9.75:1 is a Nice street cr. Depends on the cam.

 

To bang the old drum again,,,,,

 

A Dynamic CR of 8.4:1 of 97+ Octane is perfect for any Cam.

 

While this may appear low, it's not the same a (static) CR. The Static CR with a DCR of 8.4:1 could be anything from 8.4:1 to 13:1 (or higher).

 

There's no guessing when working to DCRs. It's been discussed on the forum at some length. Do a search.

Edited by Moke Spider, 15 October 2017 - 12:21 AM.

[AlexMozza]

My ratio is 10.5:1 in a 1330.

[dotmatrix]

A Dynamic CR of 8.4:1 of 97+ Octane is perfect for any Cam.

 

I realise this doesn't exactly answer the guys question...

 

but isn't 8.4:1 a bit low for dynamic compression? I have always aimed for and been told to aim for 8.5-9.5 :1 in dynamic compression, but I realise 9.5:1 is on the limit. ps. I run shell 99 octane.

[Spider]

8.4:1 DCR in an A Series on 97 RON is safe. You certainly can go up from there but around 8.8:1 DCR is potential handgrenade territory. All you need is some slightly age fuel, a hot day, or anyone of a zillion other thing to introduce knock and it won't make for a happy day.

 

I'm happy and comfortable to suggest / recommend a DCR of 8.4:1, going beyond that won't really increase HP benefits in these engines a worthwhile amount especially when considering the practical risks.

 

Other engines may have different DCR requirements, what I've suggested here applies to the A Series.

Edited by Moke Spider, 16 October 2017 - 06:48 AM.