It’s not just about the BHP
Although increasing the BHP of your vehicles engine is an important factor, if not the most important factor in increasing the top speed & acceleration of your vehicle, it’s not the only parameter that we work on. Where this power is delivered in terms of engine revs is also important.
Consider this: What is the difference between saying that a car is ‘quick‘ and a car is ‘fast‘ ?
This is the way that we look at this question, ‘quick’ = Acceleration | ‘fast’ = Top Speed
What gives a vehicle improved Acceleration?
The short answer is Torque. In layman’s terms torque is the pulling power delivered by an engine at an engine speed (rev’s ). If we draw a graph of measured torque at different engine revolution speed’s ( revolutions per minute RPM ) what we get is sometimes referred to as the ‘Torque Curve’.
By remapping the engine ECU we can adjust the engines torque curve by moving it to a higher range of RPM, flatten it slightly to extend the peak or adjust the ecu map to adjust the engines torque curve in a multitude of ways that are ideal for you and your vehicle.
Moving the engines torque curve to a higher band of engine rev’s has the effect of improving the throttle response time.
What gives a vehicle improved Top Speed?
The short answer is BHP. Break Horse Power (BHP) is not the power output of the engine, it is the amount of power / energy left after the initial engine power (HP) has been transmitted through such as the gear box and drive shafts etc. Both HP and BHP generally have a direct correlation to engine RPM, but does tend to drop off at higher RPM due to the mechanical limitation of valve timing.
Turbo & Turbo Lag
Turbo lag can be really bad on some vehicles and once again is normally due to how the engine is tuned. There are may ways to reduce or remove turbo lag, here is a simple explanation of how this can be achieved via remapping the engines ECU.
In simplistic terms consider the turbo as a device that boosts the air pressure that is fed into air/fuel intake manifold of an engine. This will get more air & fuel into the cylinder during the critical time that the cylinder intake valves are open and thus resulting in more engine power (HP).
The turbo which is a air compressor is driven by an impeller which in turn is driven by the pressure of the exhaust gases being expelled from the engine. This impeller on the exhaust side of the turbo will not start to work correctly until the exhaust gases have reached a minimum pressure, this pressure having a direct correlation to engine RPM. The lag is normally caused by the time delay of the exhaust gases reaching the required minimum pressure which will be reached at a certain engine RPM.
By moving the torque curve higher into the range of engine RPM, we reduce the amount of work the engine needs to do to increase its RPM at lower RPM ranges. By remapping to move the torque curve and thereby increase the rate at which the engine RPM increases in the lower RPM range we effectively reduce or remove turbo lag.
Other Factors Effecting Acceleration & Top Speed
While the engine is the power plant of your vehicle there are many other factors that will effect the acceleration & top speed of a vehicle. Above we mention that engine power output / horse power (HP) is the power that is produced by the engine, but it is the power that is delivered to the driving wheels, known as break horse power (BHP) that will ultimately dictates speed & acceleration. BPH is always less than HP due to the mechanical losses of gear box, drive shafts and items such as wheel bearings etc. From this point on the BHP is the power that is used to drive your vehicle forward and any resistance to this motion must also be considered. Such as flat tyres and resistance to air flow will also effect the speed and acceleration of your vehicle.