The graph shows three torque curves. The red one is the official data for the 2L 16v engine. The black line is the test data for my 2L 8v with Jetex exhaust system + K&N filter and modified air box. It was tested at the Power Station in Cheltenham. The middle line was recorded on the rollers at the MIG rolling road day held at Regal Autosport in Southampton.

The two sets of rolling road data are very close up to 5300rpm. This suggests that both dynos are similarly calibrated. Unfortunately it also suggests that the manifold hasn't done what it said on the packet. Past 5300rpm however, things look up. The torque curve doesn't drop off any more. Instead it keeps going, increasing very slightly, until the last credible data point it gives 130lb-ft and 145BHP. Past this point the dyno printout curve dived rapidly suggesting some sort of measurement or test error. The operators seemed keen to get all of the cars through as quickly as possible, so no questions were asked.

So the vexing question is: where's my missing torque? I plan to have the car rolling roaded at a local tuners and the fuelling checked. It could be that there is a massive flat spot running from 3000 to 5000rpm due to a weak fuel air ratio. If that is the case then the good news will be extra mid range torque.

I fed the new data into my accleration calculator but the difference in each acceleration bracket was pretty minimal. Performance comparison with 2L 16v Astra. The 0-60 time was predicted as 8.2s, a slight improvement on the specification of about 8.4s. It is faster by about 0.2-0.3s on the 0-90 dash (16.8s predicted) and 0.3-0.5s on the 0-100mph (20.3s predicted). The 1/4 mile time was predicted as about 16.1s with a finish speed of 88mph. These sort of results just show how a 145BHP car is not necessarily much faster than a 133BHP car. It all depends on the torque spread, gear ratios, car weight and drag.