Rev bouncing/bad launch
09-25-2011, 12:24 AM
#1
Thread Starter
Join Date: Sep 2011
Location: NJ
Posts: 23
Rev bouncing/bad launch
Today, I unfortunately let my friend launch my car from a traffic light. He spent a good 5 seconds bouncing off the rev limiter and I heard a whipping or snapping sound come from the car. Kinda sounded like the exhaust.
1.) how much damage did this dude do to my car?
2.) what noise was I hearing?
1.) how much damage did this dude do to my car?
2.) what noise was I hearing?
09-25-2011, 09:00 AM
#2
4th Gear Member
Join Date: Sep 2009
Location: NC
Posts: 1,481
Why even let a douche like that drive your car??? What the hell was he doing banging the rev limiter like that?
Does the car drive and sound OK now? Purpose of the rev limiter is to prevent damage from over-reving the motor.
Does the car drive and sound OK now? Purpose of the rev limiter is to prevent damage from over-reving the motor.
09-25-2011, 11:02 AM
#4
Thread Starter
Join Date: Sep 2011
Location: NJ
Posts: 23
The car sounds and drives fine. I just worry about losing compression in the engine. Nothings acting unusual. Shifter feels a little loose, but that's about it. A frien told me the sound I heard from the exhaust was the spark being cut off and so the valvetrain doesn't get damaged
09-25-2011, 11:21 AM
#6
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
You are worrying about nothing, as Trueblue' said the rev-limiter is there to prevent damage to the engine.
Your friend who told you about the "spark being cut off" was incorrect, on our cars the rev-limiter works by the PCM's intelligently shutting off the fuel injectors--it shuts each off in firing order sequence after it has completed the current injection cycle.
On an EFI engine that is the best way to do it because there is no possibility of lean mix detonation (at the next firing the cylinder is just full of compressed air) or raw fuel build up (if the spark were shut down and the injectors kept pumping)...
One last comment for your future consideration--there are only two other people in the world allowed to drive my car--my wife and my brother, and my brother only because he's 58 now...
Your friend who told you about the "spark being cut off" was incorrect, on our cars the rev-limiter works by the PCM's intelligently shutting off the fuel injectors--it shuts each off in firing order sequence after it has completed the current injection cycle.
On an EFI engine that is the best way to do it because there is no possibility of lean mix detonation (at the next firing the cylinder is just full of compressed air) or raw fuel build up (if the spark were shut down and the injectors kept pumping)...
One last comment for your future consideration--there are only two other people in the world allowed to drive my car--my wife and my brother, and my brother only because he's 58 now...
09-25-2011, 12:04 PM
#7
Thread Starter
Join Date: Sep 2011
Location: NJ
Posts: 23
You are worrying about nothing, as Trueblue' said the rev-limiter is there to prevent damage to the engine.
Your friend who told you about the "spark being cut off" was incorrect, on our cars the rev-limiter works by the PCM's intelligently shutting off the fuel injectors--it shuts each off in firing order sequence after it has completed the current injection cycle.
On an EFI engine that is the best way to do it because there is no possibility of lean mix detonation (at the next firing the cylinder is just full of compressed air) or raw fuel build up (if the spark were shut down and the injectors kept pumping)...
One last comment for your future consideration--there are only two other people in the world allowed to drive my car--my wife and my brother, and my
brother only because he's 58 now...
Your friend who told you about the "spark being cut off" was incorrect, on our cars the rev-limiter works by the PCM's intelligently shutting off the fuel injectors--it shuts each off in firing order sequence after it has completed the current injection cycle.
On an EFI engine that is the best way to do it because there is no possibility of lean mix detonation (at the next firing the cylinder is just full of compressed air) or raw fuel build up (if the spark were shut down and the injectors kept pumping)...
One last comment for your future consideration--there are only two other people in the world allowed to drive my car--my wife and my brother, and my
brother only because he's 58 now...
And yeah, nobody else will ever touch my car
09-25-2011, 12:20 PM
#8
TECH SAVANT
Join Date: Dec 2006
Location: Saint Augustine, FL
Posts: 10,938
The rev-limiter would protect the engine in that situation, however it is there to protect from unintentional over-revving, not as a built-in toy for entertainment purposes. Repeated (or any) "Revving" of an engine is generally harmful as the internal components will be interacting, at high speeds, under stresses and strains much different than those experienced under load.
It is never good for any reciprocating machine to be operated at high speeds with no or greatly reduced load--or for that matter greatly increased load.
09-25-2011, 12:31 PM
#9
Thread Starter
Join Date: Sep 2011
Location: NJ
Posts: 23
You can, but only a fool would do so deliberately?
The rev-limiter would protect the engine in that situation, however it is there to protect from unintentional over-revving, not as a built-in toy for entertainment purposes. Repeated (or any) "Revving" of an engine is generally harmful as the internal components will be interacting, at high speeds, under stresses and strains much different than those experienced under load.
It is never good for any reciprocating machine to be operated at high speeds with no or greatly reduced load--or for that matter greatly increased load.
The rev-limiter would protect the engine in that situation, however it is there to protect from unintentional over-revving, not as a built-in toy for entertainment purposes. Repeated (or any) "Revving" of an engine is generally harmful as the internal components will be interacting, at high speeds, under stresses and strains much different than those experienced under load.
It is never good for any reciprocating machine to be operated at high speeds with no or greatly reduced load--or for that matter greatly increased load.