Building an engine for the street or the track: what’s the difference?

by: Justin Rhoads

I have been doing some reading lately and keep running into this notion that a “street” engine is built completely different than a competition engine. As an engine guy, I did a double take; that’s not the way I see it and if you think about it, it just doesn’t seem natural that there would be a difference.

Let’s start with the basic concept; how does one approach designing an engine package for a particular application? In the post “engine design, art or science” I outlined the process that I go through whenever I look at designing a particular package. I’ll reiterate a few of the main points here; 1^st determine the operational environment, 2^nd make concessions to optimize the engine characteristics for that environment with input from the driver and chassis guys, 3^rd test and refine the package to exploit the advantages produced by the driver/chassis.

So at the end of this process you have the best possible package for what the driver needs, the chassis can use, and the track favors; why can’t we substitute street for the track in this equation? The myth of these styles of engines being completely different and incompatible with one another stems from people not going through the above steps when developing their combination. I hear the term “planning my build” a lot and frankly, it sends a chill down my spine. You do not plan (ie pick parts from a catalog and go to town) until you have gone through the developmental process (the process is the PLAN).

There lies the problem; if you simply stick a well built, high budget drag race engine in a street car the results will be less than stellar (unless this is what the driver and the chassis favor). Not because the engine builder is crap, not because the parts are junk, but because the entire package is not optimal for the application. If the above methodology is utilized anyone can successfully build an engine that meets their needs.

Now I’m sure enthusiasts and engine builders alike are burning up their keyboards with emails stating “what about my clearances”. Your bearing clearances will reflect the viscosity of the oil used by the package, which will be determined by both the stresses imposed by the nature of the application and the oiling systems ability to cope with the required oil. A top level engine builder will not simply state “for a street car I set them up at X”; there will be a method to the madness so to speak.

In the end, the same process of development should go into any engine being built along with the attention to detail; the methodology is the same with only the parts selected being different. The same quality of craftsmen ship of the parts, the same attention to detail during machining and assembly that makes a top level competition engine shine, will lead to a long and happy life on the street.

Engine Design: Art or Science?

by: Justin Rhoads

I hear a lot of opinions on this topic whenever I research products on the Internet. From what I have read most people land somewhere in the middle feeling that it’s a bit of both art and science. Having a little bit of an engineering background I tend to feel that it’s all science; in my opinion, the art is a little hit and miss….

When looking at engine design, building, or root cause analysis I find that everything comes back to science. Whether I’m looking into wave tuning on the intake tract, the engineering mechanics involved with the connecting rod in motion, to the thermal dynamics of what’s happening to the exhaust valve during the race. All of the above are quantified by some very powerful and complex mathematics. For many years an engine builder worked primarily by trial and error; grind on an intake port and then put it on the flow bench. Follow that up with some dyno time….do you think Renault does this with their F1 engine designs?

The answer is no; the same processes and knowledge that allows Lockheed Martin to determine that the F 35 will be able to fly before actually putting models into the wind tunnel apply to motorsports. Top level teams now employ engineers to perform analysis of connecting rod stresses instead of running an engine to determine mean time to failure. This goes far beyond the nuts and bolts aspect of engine building….

The same engineering methodology used to solve complex problems has also found it’s way into motorsports. No longer are engines built to simply have class leading power, the best brake specific fuel consumption, or the lightest rotating mass. Instead the process had evolved into an optimization exersize; the process has brought new considerations into the role of engine design. A 100ft view looks a little like this; 1^st determine the operational environment, 2^nd make concessions to optimize the engine characteristics for that environment with input from the driver and chassis guys, 3^rd test and refine the package to exploit the advantages produced by the driver/chassis.

What one finds when using this method is that the final result is what the application requires, what it needs, not what anyone “feels” is the best. If the application can not benefit from a 6 stage dry sump oiling system it will not have a 6 stage dry sump oiling system; even though that is the ultimate in oil control and a dream for many racers. This discipline ensures that only what is best for the application is used, nothing more, nothing less; keeping cost where they need to be and also cutting out any added features.

Remember, an engine is not a cell phone; if the driver, chassis, and application cannot utilize features of the engine, they should not be used.