** Come and see this along with many more cars on our stand @ PVS2010 **
The latest 400+bhp Astra to come out of the Regals workshop is somewhat of a special car. A Mk4 Astra GSI with the full Regals RSS works making a full on 450bhp.
The power is fully useable and pulls cleanly throughout the rev range, making this one of the best 400+bhp Astra’s around. A well cared for and properly tuned engine running a reliable 450bhp, so how did we do it ?
Without wanting to let all our secrets out of the bag we started with the standard LET engine and modified it extensively to produce the reliability our customers demand. A closed deck block with the balancer shaft removed was the beginning. The internals were reworked with an 8% lighter gas nitride reinforced crankshaft, which was also fully balanced. The big end bearings and main shells were upgraded to our own RSS specification, and the rods and pistons all upgraded to RSS specification to withstand a potential 2 bar boost pressure if required.
The Head was reworked with an RSS inlet camshaft and heavy duty valve springs, along with improved exhaust seat platforms. Finally the top end rework was completed with an EDS top hat and short runner manifold coupled with our RSS thermal gasket and 630cc injectors. To feed the monster we were creating a 220ltr/hr in tank fuel pump along with an adjustable fuel pressure regulator were added to ensure the Shell V-Power flowed constantly.
Obviously we also need something special to boost the beast, we went straight for our RSS specification turbo, a GT28.71r with a GT30 compressor wheel. Hung off, and braced we may add, a ceramic coated RSS tubular manifold this makes for an impressive sight. To complement the turbo we upgraded to a 3 bar map sensor and RSS boost control solenoid along with the RSS CDTI airbox system and Dbilas high flow airpipe.
The engine bay that holds 450bhp !!!
As you can imagine the air has to go through a special intercooler to keep the temperatures down. An all aluminium bar and plate intercooler, with cast end tanks and a 60mm inlet and outlet pipe was bolted up front. It has been fully tested to 3bar pressure and with its super efficient bar and plate design shows no effect on the OE cooling radiator and only a 15degree over ambient inlet temperature. To aid with the cooling and to lose some weight the OE Air conditioning condenser and compressor have been removed. To ensure everything is 100% reliable, a remote mocal oil cooler has been installed in the lower bumper. 13 rows and utilising custom banjo fittings which also retain the OE oil to water cooling, this is one of the first cars to utilise such a solution.
As you can imagine the transmission is now being asked to perform a difficult job with 2 times as much power to put down. We retained the original F23 gearbox but have modified it slightly with a Quaife LSD with Millers racing fluid, and an RSS light weight flywheel and RSS clutch. The rest of the chassis modifications consist of a KONI coilover kit with an AP racing big brake kit.
The all important RR graph