The CSF Evo X, Building a Time Attack Worthy 4B11 Engine Part 1

The big end of the Carrilo rod feature a lipped cap.  This increases the contact area between the cap and the rod which greatly increases big end integrity under stress caused by tension loads.  This feature really helps in stroked engines which have a higher tensile load due to the higher pistons speed caused by increasing the stroke.

The ribbed cap at the end of the rod reduces big end distortion under load.  This increases the overall strength of the rod and helps with bearing life. Carrilo makes their own rod bolts and we have the optional Multiphase TM alloy bolts which have an ultimate tensile strength of 285,000 psi.  This is up from the typical 200,000 psi of the more common ARP 2000 bolts found in many performance rods. Since the bolts are the weak link in a connecting rod you can’t have them strong enough for this sort of high boost application.

For a piston we chose a custom JE forged part that has the piston pin moved up 4mm to accommodate our 94mm stroke. We are also running 0.5mm oversize so we can control the piston to wall clearance.  Our block had some wear when measuring so we want to start with a fresh bore. Since we are running ethanol as a fuel, we upped the compression ratio to a pretty high for a turbo engine 10:1.  This will help power, particularly the off boost low-end, and will help spool the turbo faster.

The JE piston is made from 2618 low silicone alloy using JE’s FSR strut piston forging.  This is a tough and ductile alloy that can withstand the high cylinder pressure this engine will see.  Traditionally 2618 alloy expands a lot with heat and needs a bigger piston to wall clearance.  This makes for an engine that rattles a lot, especially when cold. However, JE’s advanced piston design capabilities have made piston skirt contours that match the piston’s expansion over its thermal gradient and thus can run much tighter piston to wall clearances than previously thought possible with 2618. The FSR forging uses a slipper reduced skit for lighter weight and less friction and has struts that tie the entire dome into the pin boss for strength.  This way you can have slipper skirts and a short piston pin with a compact pin boss for less weight but the struts keep things stiff and strong by tying everything together.

Our piston has optional hard anodizing in the groove area and the dome. Hard anodizing is a very hard ceramic like layer of aluminum oxide electro converted on the surface of the part. It greatly improves the wear life and anti galling aspects of the ring grooves.  Ring groove clearance is a critical aspect of ring sealing, especially under high cylinder pressure and RPM.  For rings we used JE’s low tension 1.1mm compression rings and oil rings. Our piston has lateral gas ports to help with ring sealing. We also ordered our pistons with optional tuff skirt dry film lubricant coating on the skirts and with a thick wall DLC coated piston pin in anticipation of high cylinder pressures.

Because of our factory applied piston coatings, we could not WPC treat our pistons.  We did WPC the piston rings and the rods.  We also used WPC’s cryo treating service on just about the entire engine.