Aston Martin DB7 Performance Upgrade
Torque Developments International were commissioned to evaluate the engine performance of the Astin Martin DB7, with a view to enhancing the torque.
We already had a wealth of experience of tuning the Jaguar 6 cylinder 4.0 supercharged engine, so we expected to apply some of our learning to the DB7 which shares some commonality with the XJR.
The test vehicle is a stunning manual transmission example in red, having covered a very modest mileage which the owner had previously installed a high performance exhaust system from the catalytic convertor backwards.
The first stage in the evaluation process was to extract some performance and dynamic data from the standard engine using our Rototest chassis dynamometer and DataQ data aquisition centre.
Our testing indicated the following limitations that need to be addressed:
1. The intake temperatures are too high and are uncontrolled (see data log sheet below showing the increase from 43 degrees at low speed on the first run, to 58 degrees at high speed on the 3rd run).
2. The power and torque drops by 10% over the course of three power runs (see attached performance snapshot – runs 5-7 below).
3. There is an intake restriction before the supercharger (see the green line on the data logging sheet – runs 8 & 9 below).
4. There is a substantial back pressure present in the exhaust system (measured in the down pipe (see data logging sheet – runs 10-11 below)) of almost 1.7 bar (absolute).
5. The air/fuel ratio is very rich.
This is the exhaust back pressure test taken from the down pipes, showing a 1.7 bar (absolute) of back pressure in the exhasut system. That is higher than the supercharger boost pressure!
This is the restriction in the intake system.
This is the intake temperature. Note how the temperatures rise from 43 degrees to 58 degree over only three power runs. Worryingly, the temperatures seem to be uncontrolled and continue to rise the longer that full power is used.
This is the power and torque curves of the standard engine. Note that the power and torque reduces by 10% after only three power runs!
Our testing has revealed that the following critical path should be followed:
- De-restrict the exhaust downpipes and catalytic converter.
- Design and manufacture a large capacity charge cooler pre-radiator.
- Manufacture a less restrictive intake system.
- Re-check the air/fuel ratio after the above solutions have been implemented.
Following the implementation of the above, if the AFR’s are still too rich we will then consider an ECU solution to remedy this. If the exhaust back pressures and intake temperatures come into acceptable limits, we will then consider raising the boost pressure.