There has been some discussion over the Astra VXR turbo charger unit and its benefits. Earlier this year, we were lucky to get hold of a unit and we have recently completed some tests with this fitted to a Z20LET Astra Coupe. The purpose of the test was to see how the VXR turbo compared to the Turbo Dynamics Stage 2 unit.
We have included the Power and Torque graphs along with an acceleration graph. This graph shows us what the power delivery does on the road in terms of acceleration from 40 mph to max speed of 127.5 mph (in 4th gear).
The production unit looks much the same as the standard Z20LET, ZLEL and ZLER turbo. On our unit the actuator was a prototype unit, however this was changed to a 1 bar actuator to directly compare it with actuator fitted to the TD unit.
Both cars were fitted with a complete Milltek exhaust along with the Milltek sports cat that has the rear flange at 62mm internal diameter, up over the standard 52mm ID. They both had uprated intercooling / boost cooling set ups so the air temps that were recorded were also consistent. Finally both cars used an identical version of our Stage 3 software.
The first thing that was evident was that the VXR unit produced its peak torque sooner, also the torque was flatter across the rev range, dissecting the Turbo Dynamics power curve that was sometimes higher or lower on power. These results suggest the TD unit has a larger “AR” ratio building its boost later it would also seem that the TD unit is capable of much more power but is hampered by the restrictive exhaust manifold casting, leading to this, albeit minor, power oscillation as the internal pulses change the restriction in the manifold.
To form some kind of conclusion it’s clear that they do things in a different way but overall there is very little between them. It's very much give and take with them trading punches all the way through the run. This is especially evident when you look at the acceleration times. On other cars with a similar spec fitted with the TD unit we have seen small variations in power and torque but the profile of the delivery is always much the same. In the same way, on the many runs we did with the VXR unit, they varied a little on power or torque but the general profile remained the same. The VXR unit did not hit the same peak torque as the TD turbo (although on one run we did see 290lbs ft), but VXR unit did hit peak torque earlier and went on the make a bit more power. In the VXR unit’s favour, the manifold section has been recast in a higher specification of material to prevent cracking. Good news if you have been on the wrong side of this failure.
The final and major plus is that the unit is rumoured to have a retail price of £585.12, whilst the standard ZLET, ZLEL & ZLER unit has a retail of £867.15! As long as Vauxhall don’t revise this, then it’s the performance bargain of the year. It’s just a pity that there is no stock available at the moment. But watch this space for more information as it becomes available.
And here are the graphs...........
Power Curve: Red=VXR 278.8 bhp Blue=TD 275.9 bhp
Torque Curve: Red=VXR 281.1 lb ft Blue=TD 292.5 lb ft
Acceleration: Red=VXR 127.5 MPH 15.6 seconds Blue= TD 127.5 MPH 15.9 seconds
Forward orders are now being taken by Courtenay Sport for this turbo unit. Ideal as an alternative to the existing hybrid turbo units for those wanting to run Stage 3 remap.
This turbo will require an uprated actuator and bracket to allow maximum overboost and peak boost to be acheived with the Stage 3 remap.
Uprated actuator and stainless steel bracket £120.00
Courtenay Sport Limited
10c Folgate Road
Telephone:+44 (0) 1692 404313
Fax:+44 (0) 1692 404069