Engine

The engine is the center of the internal combustion powertrain system. All other components of the greater system exist to service the engine in different ways. This means the engine is sensitive to design changes made across the entire powertrain. As of 2022, the FSAE rules require an internal combustion engine with a displacement of 710cc or less. Available OEM motors within this displacement limit are largely sourced from motorcycles and snowmobiles. The purpose of an internal combustion engine is to convert the chemical energy in gasoline or ethanol into mechanical energy used to propel the car. The engine is one of the most complicated and often heaviest single parts of any vehicle.

Please take a look at the outline in the discussion section before making changes to this page

Theoretical

Main page: Otto Cycle

Structure

Wikipedia does a very detailed explanation on general engine layout. This article will focus on motorcycle-style engines w.r.t. fsae competitions.

Engine configuration is a case where the 80/20 rule really applies: the last bit of effort really doesn't get you too much. The bike engines are supersport engines and already configured to perform at a high level (albeit with a bike transmission and unrestricted intake). Removing first gear and some of the higher gears and using a dedicated racing clutch are probably the lowest hanging fruits with regards to the actual engine itself. A custom oil pan is likely essential for many engines due to packaging but a custom wet sump will lack any moving parts.

The structure and operation of motorcycle engines differs from typical car engines in a few key places: size, layout, redline bb. Engines used in these competitions are all under 150 lbs with 600cc 4 cyl coming in at about 125-140hp, depending on brand or custom parts. Single cylinder engines typically weigh in the neighborhood of 70-90 pounds. These engines are almost exclusively overhead cam layout.

structure: cams, ports, valves, cylinder, piston, conrods/crank, oil and wp, case and covers. crossflow cylinder discussion? Yamaha yzf that have intake in front and exhaust in the rear - contrast to every other engine

I dont know anything about snowmobile engines so someone else is gonna have to do that.

Engine Control

Main page: Engine control

Most modern engines are controlled by an engine control module (ECM) that determines when to inject the fuel and when to ignite the charge using various sensors and an engine tune.

Goals

Reliability

If the engine finishes endurance, it was reliable. (to some teams, to others, maybe they need one engine to last many years due to budget constraints or the fact that they're running an aprillia and there's only two in the US)

Michael Royce in Learn & Compete states that “[reliability] must be the number one technical objective of the team”.

Engine to engine comparisons are difficult, and the literature is sparse at best. Most available engine specific reliability reports are anecdotal. However, brand comparisons are both easier and more widely available. Consumer Reports performed such a comprehensive study on motorcycle reliability.

The reliability study is focused on how often the bikes would need to have repairs within the first four years of purchase. The three big Japanese motorcycle companies, Yamaha, Suzuki, and Honda, are the only three with under 15% of the bikes with repairs needed. Yamaha leads the brands with 11% compared to the 12% for Honda and Suzuki each. It is important to consider that this study included the bike as a whole, and that for all of the studied motorcycles“mechanical engine problems were relatively rare, with only 3 percent having trouble with the cylinder head or valvetrain, or with the crankcase, crankshaft, or pistons. Similarly, only 3 percent needed transmission repairs, although 7 percent had clutch problems.” LA Times [citation needed] researching this study reported an interview stating "European bikes are engineered for character and sex appeal, and Japanese bikes are engineered for reliability,". This sentiment can be found echoed in the FSAE online forums.

Another aspect of reliability is parts and tools availability. If something breaks, how easy is it to get hold of spare parts quickly in order to fix the engine? Do you need special tools to service the engine, and can you buy, borrow or manufacture these?

Power/Torque

An obvious goal of an engine is to produce enough power to accomplish your designed team goals. How much is enough? What RPM should we make peak power? Torque? To all of these questions, it depends heavily upon your team's design philosophy. All could be relatively determined from a rudimentary laptime simulation, but will need to be confirmed via testing.
Also worth noting theory on how to determine ideal peak power position (histogram of engine speeds, peak torque at roughly that speed. Can also loosely perform an "integral" by multiplying engine speed occurrences with the power output at that point as when the integral is maximized, the most power was put down to the track)

I imagine there is a lot more to expand upon here - Novotny

Examples of teams design philosophy:

• we have a novice driver - we want our torque curve to be wide and flat
• we run a CVT and the engine will hold at a specific RPM during all events and we only want torque at that spot at the expense of all else
• we are a first year team and we dont know what we are doing so we are just going for peak torque everywhere
• we have the torque curve in the shape we want so we are just tuning for peak torque everywhere
• we are running with huge boost and need to run with an AFR of 9 or else we'll be building a bomb
• we can't get our engine to idle, so we're spending the whole year tuning at 1.5K RPM and didn't get around to anything else
• our driver is a 4th year masters student who has 8 years of FS driving and can put the engine wherever he wants, we are giving him peak torque at 9650 RPM because thats what gives him the fasted lap times during testing

Torque and power are determined by testing the engine on a dynomometer (need page for dynos).

Power Limiting Factors

Restrictor

Restrictor power limit derivation

Piston Speed Limit

The competition limits the engine speeds allowed.

a. Automotive / Motorcycle engines 914.4 m/min (3,000 ft/min)
b. Industrial Engines 731.5 m/min (2,400 ft/min)
The calculated speed will be rounded to the nearest 500 rpm.

Efficiency

high speed low drag babey

Engine Modifications

• To fill in, see note in editing for discussion points

Simulation

otto cycle

matlab sims for freshmen?

1D engine sims

Ricardo WAVE or GT-Power are commonly used. At the 1D level, simulations are good for understanding trends, but not necessarily getting a precise power number. These trends can help identify what changes to the system will have positive or negative impacts and to what extent they will change the output. Specific problems arise in the 1D models for the highly 3D behavior air achieves through the restrictor and plenum. The strength really lies in getting an engineering understanding of how to design an intake and exhaust for a given torque curve e.g. runner length, exhaust collector strategy (4-2-1 or a 4-1 exhaust), and plenum size.

3D flame propogation sims in advanced research labs

Just use a dynamometer or WAVE. 3D combustion CFD is really nasty and without experiments to support your model it is suspect.

Oil System

Main page: Oil

Mounting System

Vibration Reduction

Best Practices

Engines can be incredibly robust to working conditions as long as they have air, compression, fuel, and spark. That being said, there are many places where a little love and care will reap huge benefits.

Many of the systems inside the engine operate on small tolerances. These tolerances mean it's wise to care for your engine, if you want it to last. Often, you can operate an engine outside of many of these tolerances, but you will lose performance and often risk severe damage to the components if not catastrophic failure.

When purchasing an engine, it is good practice to tear it down and inspect all parts for tolerance. If the engine is used, this is exponentially more important, as you will need to check for wear as well. Many teams (in the US) purchase used engines from motorcycle crashes, which can cause subtle damage to the internals, even if none is present on the outside of the engine.

Servicing

It will be well worth the investment to buy a service manual for the engine, or find a pdf online to print, and put together in a binder. If putting the pages in a binder, using plastic sleeves will protect the pages from oil damage. If using a book... be careful.

• Buying a used engine
• Teardown
• Valvetrain
  • Take the chance to measure your cams if you can for accurate simulations.
  • Correct lashing
  • Valve seating
• Head
  • check flatness, possibly deck
• Block
  • Clean surface
  • Check flatness, possibly deck
  • Check cylinder roundness, if too far out of spec you'll lose a significant amount of power. would not recommend boring to oversize, as the competition is size restricted, and aftermarket parts will add up cost very quickly
  • Hone cylinders if changing rings, or if too shiny
• Pistons
  • Clean faces
  • check rod bearings for wear
  • Check rings, likely good idea to replace if any blow-by on piston
• Crankcase
  • Check for metal bits lol
• Get a new set of gaskets (MLS head gasket can likely be reused depending on condition)
• Get a new set of all TTY bolts

How/when to service.

How to diagnose issues.

Why combustion is more romantic than electric.

Common Engines

I think bc the cbr, r6, and a few of the 450s are so common, we can use this to list what we have done to optimize for FSAE use.

Example: gear removal, EWP, custom valving, suggested idles, mounting tips, weights/mass, stock water pump flow rates, oil recomendations, intake mounting recs. exhaust mounting recs, heat generation, wiring, injectors

Honda CBR 600RR

• remove first gear, breaks traction with any reasonable FDR
• max heat dissipation of ~10kW needed from cooling system (utoronto 2007)
• remove the thermostat control to keep temps down (this is something I am skeptical of. The thermal mass of the engine and cooling circuit is high enough that you won't get into trouble running the OEM thermostat if the cooling system operates correctly, and the engine is happier when it is at temperature. This is a relatively minor modification so running a lap with and without could be a decent test)
  

Yamaha R6

Yamaha WR/YZ450

• WPI runs WiSECO high compression piston

see all engines here