2.4l Opel 8V CIH Competition Engine

Rolling Road testing of this Engine

Thursday 4/1/2001 at Emerald Cams

After initial trial runs and setting up, the cam timing was adjusted to give max inlet v/v lift at 102° ATDC.  Max power is 191BHP (at flywheel) at 5750RPM, max torque is 177lbft (240NM) at 5415RPM.  Max power at wheels is 158BHP.

The guys at Emerald said that the new thermostat was much better, as the coolant temperature never exceeded 84°C during the power runs carried out.

Power runs were tried with the ITG foam air filter removed.  However, this only increased the max power to 192BHP, and had no effect below 5000 RPM.

I am still somewhat disappointed with these results.  Adjusting the cam to give max v/v lift at 100° ATDC may have given slightly increased power figures, but this was not done.

This engine should have been capable of developing at least 200BHP at the flywheel.  Compared to engines of its type, with similar specifications, this engine performs well at mid range, and has quite a wide power band due to the good mid range, but is poor at the top end.  Although the RPM at which max power (191BHP) is developed is quite low, it should be noted that the engine is giving in excess of 185BHP from 5400 to 6300 RPM.  Although the RPM at which the engine develops max torque (177lbft or 240NM) is very high, the engine is developing in excess of 175lbft (237NM) from 4650 to 5750 RPM, and exceeds 140lbft (190NM) from 2400 to 6450 RPM (RPM limiter is set at 6500 RPM).

Monday 8/1/2001 at Motoscope

As a comparison for the figures from the Emerald Cams rolling road, against previous power runs on the Motoscope rolling road, we got a figure of 155BHP, at the wheels, for the engine in its present configuration.  This is the same figure as we got in December 2000, with the cam set for max inlet v/v lift at 102° ATDC.  In December, we had attained 165BHP, at the wheels, with the cam set for max inlet v/v lift at 100°C ATDC.

Further Work

1.    Further adjustment of the cam to get the extra 10BHP, will require another trip to Emerald Cams.  At this time this is not possible, as fuel costs alone is nearly £200 for the Manta and my tow car.

2.    A compression check shows that static compression has been calculated incorrectly, and is actually nearer 10:1, rather than the 11:1 that we had originally aimed for.  In fact, Emerald suggest that the engine should be run with a static compression of 11.5:1, which is quite possible using Super Unleaded petrol (97 RON).

3.    Emerald have suggested that I increase the length of the throttle body ram pipes by about 15mm, which would increase the inlet tract length to its optimum.  This should be expected to increase engine torque, but should not require any changes to the engine management set-up.

4.    It was also suggested that any means that could be introduced to reduce the inlet air temperature by 5 to 10°C would have a positive effect.  This is because the inlet air temperature during testing was very high.  Above about 50°C, fuelling and timing are altered by the engine management to take account of the lower air density above this temperature.

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Last updated: Tuesday, 03 December 2002.