Astra H VXR Sprint

Late 2013, and in the quest for even more useable power on track, the next step was to add a high flow inlet manifold (more in a later post) and a set of H-Beam steel rods with ARP rod bolts. The steel rods are being added for strength and safety (in case of an over-rev) and to take advantage of the extra power available at the top end afforded by the already fitted K06 turbocharger and the soon to be fitted Inlet Manifold. The steel rods will allow the engine to rev to around 7,500 rpm. The factory fitted pistons are a Mahle forged piston and are very strong for a factory piston capable at up to 500bhp so more than adequate for this track day application.

The H-Beam steel rods were taken to my local engine machine shop (who do a lot of motorsport engine prep) and have been balanced end to end to within 0.5 grams. Once returned it was time to fit them.

The engine was opened up; airbox removed, turbo removed, inlet manifold removed, cambelt removed, rocker cover off, camshafts and lifters out then the head was removed and placed on the workbench. At the bottom end the sump and upper sump carrier were removed, the baffle plate, oil pickup and bridge came out and then the big ends could be removed and the pistons and factory rods could be lifted out from the top, ensuring the bearing caps and rods were dot punched to identify them and keep them together should the engine ever go back to standard.

The news was good when everything came apart. The engine has had regular oil changes and the bores are in excellent condition (which to be honest was what was expected), not showing the mileage it has covered (which is currently a shade over 87,000 miles) and with the original hone marks in the bores still visible and the pistons are also in excellent order. The cams are also showing no signs of wear.

Once removed the factory pistons and rods were also taken to the workbench where the OE rods were swapped over for the steel rods and the piston rings were checked and repositioned to ensure they were in the correct orientation. At the same time all 16 of the Valve ten Oil Seals, some of which were leaking on the exhaust side, were replaced and when the exhaust side stem seals were replaced 8 valve stem oil seal retainers were also fitted. These help prevent the stem seals from lifting off and leaking in future.

Whilst apart the cylinder head, cam shafts, oil pick up pipe, oil pan carrier, sump pan, baffle plate and bridge were all put into the Safety Kleen tank and thoroughly cleaned prior to being refitted.

The pistons and rods were then refitted into each bore with new Mahle big end bearings and the big end bearing caps fitted and then secured with the ARP rod bolts, torqued up to 55 lb/ft with ARP Assembly Lube. The engine was then put back together with new gaskets, seals and new head bolts and timed up ready to go.

Winter rework will soon be underway, to further improve the car, although it is extremely capable at 300bhp when last run up on the rolling road. The factory inlet manifold is pretty restrictive so on track the car relies quite a lot on the spread of torque the car offers, especially mid-range because peak power is around 5,600 rpm and much above 6,250rpm the engine power really drops off.

A little more power at the end of the straights is always useful to get past cars that on occasion (quite often as I have found out) don’t lift down the straight, despite the fact you have spend most of the previous corners ‘pushing’ them.

So the plan; make the best use of the fitted K06 turbo, fit a higher flowing inlet manifold to give more power and torque above 4,000 rpm, and still produce good power at 6,000 rpm where the current set up really starts to drop off significantly and continue to produce good power at 7,000-7,500 rpm (ideally somewhere around 315-320bhp).

Added to this will be changes to the engine oil cooler, the addition of a gearbox oil cooler, oil temperature (engine and gearbox) and boost gauges plus a replacement set of Pagid RS29 front pads (they are just about due for change having covered 2,000 miles!) and a new set of wheels and tyres.

Added to the car to help further reduce any exhaust system  movement are these PowerFlex uprated polyurethane exhaust mounts. Stiffer with much less give holds the exhaust more solidly with less movement. Ideal for track use where the tailpipe can move and touch the rear diffuser, often melting it in places where it touches.

The Piper 3″ system uses 6 of these mounts.

Powerflex Exhaust Hanger

Having previously (in 2012) filled the original gearbox side engine mount with sikaflex to stiffen it and reduce movement due to the lack of an uprated gearbox mount, Powerflex brought out (in early 2013) a polyurethane gearbox mount insert having been asked to manufacture it by Courtenay Sport. This insert reduces the movement in the factory mount and the black insert shown here is the race/track spec stiffest mount manufactured out of 95 Shore A material. Since Powerflex sent me an insert to try out, a new OE side mount and the uprated insert have been fitted to the car.

OE Gearbox Engine Mount with Uprated Polyurethane Insert

This mount makes a massive improvement in reducing flex in the factory mount and really compliments the other Vibra Technics mounts well.

Courtesy of Pro Alloy Motorsport, I have a gearbox breather tank to add to the gearbox. Fitting one allows about an extra half litre of gearbox oil to be run in the gearbox, allowing for better lubrication and a larger volume of oil will dissipate more heat.

First the batter, and battery tray have to be removed. This give access to the top of the gearbox. The fill plug is removed and replaced with the supplied fitting to convert the fill plug into a breather point. Here it is fitted into the top of the gearbox. The second breather point can be seen top left of the picture:

8mm Fitting for Gearbox Breather

The breather tank is to be bolted to the bulkhead, so an M6 jack nut was installed into the bulkhead and tightened securely:

M6 Jack Nut Mounting

A hole was then made in the bulkhead sound deadening with a soldering iron to allow the bolt to pass through and into the captive nut:

Mounting Hole Through Sound Deadening

Both lengths of hose (one 10mm and one 8mm) were then measured and cut and then fitted to the two breather points with hose clips and then onto the breather tank on the bulkhead:

Gearbox Breather Points

And here is the breather tank bolted to the bulkhead:

Black Breather Tank Fitted