The question of wind resistance caused by the RazerLift (without any cargo) comes up every now and then. The RazerLift is likely to be kept on the vehicle even when it is not in use so how much of an impact on the fuel consumption can users expect as a result of keeping the RazerLift installed? Without having an actual prototype to work with the next best thing is to utilize Computational Fluid Dynamics (CFD).
The video below shows the CFD simulation in progress.
A friend of mine has a PhD in Computational Fluid Dynamics so it was really exciting when he agreed to estimate the airflow characteristics of the RazerLift. Oh sure, some people might hang out with actors, rock stars and other celebrities but when’s the last time you rubbed shoulders with somebody who is a stone’s throw away from being a rocket scientist? Jealous, anybody?
The impact of the RazerLift (or any external accessory) on fuel consumption will be minimal in the city because a vehicle doesn’t travel fast enough for wind resistance to be a significant contributing factor. On the highway, however, wind resistance becomes a significant component of total power consumption and therefore worth considering. This analysis of the RazerLift predicted that the total impact on fuel flow should be in the range of about 1 L/100km. But even that number should be taken with a grain of salt. The analysis was conducted on the 3D model as it existed at the time of analysis and we have a number of significant improvements in mind that will impact the wind resistance.
And the beauty of airflow induced drag is that if you don’t like the impact on your fuel economy, slow down a bit. In fact, you really don’t have to slow down very much at all. The power consumed by drag is proportional to velocity cubed, so a 5% drop in speed reduces drag-induced power consumption by about 15% (i.e. 0.95 ^ 3). When you consider the total drag of the entire vehicle, merely changing your speed by about 5-10 kph (depending on how lead-footed you are!) should be enough to eliminate the additional drag caused by the RazerLift. That’s a pretty effective way of improving your highway mileage with or without accessories. Consider that a little public service announcement.
And one of the accessories we intend to develop for the RazerLift is a wind deflector, so this whole discussion may end up being somewhat theoretical anyway if people install those on their vehicle.
I have to say that I just love how much engineering is being applied to the RazerLift. Prior to this CFD analysis Tangent did some FEA simulations of vehicle accidents. Results looked really good. By the time we get to testing the prototype we will have done some very substantial engineering analysis of the design so hopefully the hiccups that do surface during testing (because we know they will happen) will be minimal.
And the aforementioned field testing will likely begin before the end of the month.