How to lower the engines compression ratio

obi_waynne

Administrator
Staff member
Moderator
Points
1,157
Location
Deal, Kent UK
Car
A3 1.4 TFSI 150 COD
Reducing the compression ratio is required if you want to run a high boost supercharged engine. High compression NASP engines are quite efficient but when adding forced induction you want to lower the compression ratio. The compression ratio has a dramatic effect on an engines performance and the problem of knock, (where the air fuel mix prematurely ignites) is controlled to a large degree by the compression ratio.

Continue reading... or post your comments below on this article.
 
To low CR in a turbo car makes it sluggish off boost but can cope with higher boost levels.
My car has 8.7-1 static CR and if's fine off boost.
IMO it comes down to tune/mapping with any turboed car AND the quality of fuel used regardless of CR

What is "high " boost I have 20 psi and the Yanks call that low as they seem to use 25-40 lbs in DD cars ?
 
Thicker head gasket is the first thing that comes to mind. Polishing the cumbustion chambers also will remove a small amount of metal and enlarge them. You can recess the valves a bit also. Stuff like that can move the compression around up to a point (ratio point).
 
The best way is to get proper low compression pistons and having a low squish/quench area by keeping the piston to head clearance no more than 1mm, helps to reduce detonation. Also making sure that any sharp edges are reduced in head and pistons.
 

Similar threads


Please watch this on my YouTube channel & Subscribe.


Back
Top