EG33 build for high boost stage 3 supercharger

[longassname]

The stage 3 supercharger system comes set up to run well on a stock svx engine but we can rebuild the EG33 engine to optimize it to run higher ratios of atmoshperic pressure on street gas. Namely, we need new pistons. In this post I'll be laying out the details of the Eg33 combustion chamber along with photos and explaining the details of what makes a good piston for forced induction.

There has been very little information made public about the EG33 engine's combustion chamber to date and what little information has been publicly available thus far has been confusing. The threads talking about pistons for the EG33 thus far have focussed on whether the 2.2L turbo pistons will work or not and what the compression ratio with them would be. Trying to compare the #'s estimated for the pistons with the #'s estimated for the head they just didn't add up. This turns out to be because the SVX uses a thicker head gasket and the pistons extend "out of the hole." Because the SVX pistons extend "out of the hole" and the ej22 pistons do not we can forget about using them in the svx as they would very negatively effect the performance of the squish area. I'll explain more about squish later on.


The SVX combustion is relatively large. 11cc larger than that of the Ej22 engines which have the same bore, stroke, and thus per cyllinder displacement as the EG33. Here are a couple of photos from both angles.



Before getting things messy I made a rubbing of the squish area on the head to be used in designing the matching squish area on the pistons that we will be having made. To do this I put a piece of paper over the combustion chamber and then put the head gasket over the paper and lined it up. I then used my finger to drag carbon from the edge of the head gasket to make the rubbing. I then traced the outline and put in measurements taken with a pair of calipers directly on the metal. The squish area is the area inside of the bore of the head gasket but outside of the combustion chamber. When the piston comes up to top dead center it squishes some of air fuel charge inside of this area and creates turbulence which mixes the fuel charge with the air charge inside of the combustion chamber--a feature which is important to the efficiency of combustion. You want to shape the top of the piston to create a matching squish area to the head. At top dead center the piston should be as close to the head as tolerances for expansion, piston rock, and carbon build up will allow. This prevents the air fuel charge inside of the squish area from igniting keeping the edges of the piston cool to prevent detonation and failure while maximizing the heat generated in the center of the piston early on to create the most power. Squish area is very important.




I'm continueing with this write up but splitting it up so that I don't get any errors while posting. Please don't post anything in the middle of my write up while I'm continueing to type the next post.