Over-run is generally the term used to describe when you shift in to a lower gear and the engine is being driven by the wheel speed….I.E. When you shift from 4th to 3rd gear the revs pick up on their own with no throttle input. That is over-run.
What causes engine overrun?
The simplest causes are that the wrong grade of petrol is being used (usually of too low octane ), the spark plugs are faulty or of the wrong grade, the carburettor is badly out of tune, or the ignition timing is faulty.
Is Overrun bad for your car?
On the path
You are blowing incompletely burnt or unburnt petrol through the exhaust system. Misfires can damage cats let alone that volume of fuel and as the cats are part of your car, yes it damages your car.
What is overrun condition?
Overrun, the condition of a vehicle travelling without throttle, see freewheel. Overrunning clutch, see freewheel.
What is overrun in exhaust?
Overrun is when the engine is spinning faster than the amount of throttle can sustain – so either engine braking or the period just after lifting off the throttle before the revs drop.
What is overrun burble?
1 Answer. 1. One cause of pops is unburnt fuel hitting the exhaust manifold – many engines use fuel to cool the cylinder when you lift off, so this sprayed excess then burns as it hits hot metal in the exhaust. The burble on overrun is usually caused by ignition timing being retarded.
Why does my engine still run after I shut it off?
Answer: After the engine is shut off, its temperature rises. This excessive heat and pressure in the combustion chamber is what causes detonation, which ignites the residual fuel-air mixture in there.
Is Afterfire bad for your car?
Backfires and afterfires are worth paying attention to since they can cause engine damage, power loss, and decreased fuel efficiency. There’s a variety of factors that can cause your car to backfire, but the most common ones are having a poor air to fuel ratio, a misfiring spark plug, or good old-fashioned bad timing.
Why do turbo cars pop?
Generally speaking, turbocharged cars can also create these sounds. The popping noises occur when ignition is retarded and unburnt fuel is sent into the exhaust system, where it combusts.
Is burble tune bad for turbos?
It’s just side effects from the tune. As long as you don’t rev and make it bang all the time you should be ok. Now the Tunners that make it do it all the time, that probably won’t make your turbos Happy.
What is the throttle body?
In a traditional spark ignition gasoline engine, the throttle body is the part of the air intake system that controls the amount of air that flows into an engine’s combustion chamber. It consists of a housing unit that contains a throttle plate (butterfly valve) that rotates on a shaft.
What causes a runaway diesel motor?
Diesel engine runaway occurs when a diesel engine ingests a hydrocarbon vapor, or flammable vapor, through the air intake system and uses it as an external fuel source. … If not stopped immediately, it can cause the engine to overspeed, the valves to bounce, and flames can pass through the manifold.
What is injector overrun?
Overrun Fuel Cut (or OFC for short) is a method used by some OEM ECUs to turn off fuel injection under certain conditions – such as rolling down hill with the throttle closed (ie under engine braking.)
What causes backfire on overrun?
An engine backfire occurs whenever the air-fuel mixture in your car combusts somewhere outside the engine’s cylinders. This can cause damage to your car’s exhaust or intake if left unchecked — and it also means that your car’s engine isn’t making as much power as it should, and is wasting lots of fuel.
Is exhaust popping illegal?
No. The sale and installation of an aftermarket exhaust system remains legal in California so long as it does not exceed a sound level of 95-decibels when tested under SAE J1492 and complies with all other exhaust and safety laws and regulations.
Are pop tunes bad for your car?
This kind of tune is absolutely awful and it needs to stop. Not only is it really obnoxious, it can potentially permanently damage your engine either quickly or slowly. In addition to this, that excess fuel turned out to be pretty awful for the longevity of an engine. …