Question about Compression-haters....CARS BABY

[TechnoKid]

Originally posted by: KokomoGST
the compression ratio doesn't change when you engine brake... in fact, the compression ratio on 99.999999% of cars NEVER changes.

There are some race engine naturally aspirated engines, like the Hondas and Neons in sport compact all motor drag classes that run over 12:1. A lot of high performance road cars now run 10:1, even 11:1 compression ratios.

Formula One runs like 16:1 compression :Q

 

[Iron Woode]

Originally posted by: TechnoKid

Originally posted by: KokomoGST
the compression ratio doesn't change when you engine brake... in fact, the compression ratio on 99.999999% of cars NEVER changes.

There are some race engine naturally aspirated engines, like the Hondas and Neons in sport compact all motor drag classes that run over 12:1. A lot of high performance road cars now run 10:1, even 11:1 compression ratios.

Formula One runs like 16:1 compression :Q

Back in the good old days we could actually buy a real car that could be driven every day that came with 12:1 or higher compression. 108 octane gas was just a Sunoco station away.

 

[Pacfanweb]

To answer the original question, you can use the engine to slow the vehicle you're talking about all you want, Goosemaster. Period.

 

[Ronstang]

Originally posted by: Pacfanweb
To answer the original question, you can use the engine to slow the vehicle you're talking about all you want, Goosemaster. Period.

Yep.....these kids just don't get it do they? Ricers have flooded the world with automobile misimformation.

 

[Mill]

Just STFU Goosemaster... Jesus.

 

[notfred]

I'm just confused now. How the hell did compression ratios get associated with engine braking?

 

[IamElectro]

Engine braking is achieved when the pistons have to overcome the high vacuum created in the intake or push against a restriction in the exhaust in order to fall. Because a gas engine has a plate that blocks the entry of air into the intake manifold when the engine is decelarating, the pistons will have to fight the vacuum created in the intake in order to rise and fall. Compresion does not increase it stays the same.

 

[Goosemaster]

Originally posted by: IamElectro
Engine braking is achieved when the pistons have to overcome the high vacuum created in the intake or push against a restriction in the exhaust in order to fall. Because a gas engine has a plate that blocks the entry of air into the intake manifold when the engine is decelarating, the pistons will have to fight the vacuum created in the intake in order to rise and fall. Compresion does not increase it stays the same.

Thanks. Very interesting stuff....guess my dad was wrong.

 

[Iron Woode]

Originally posted by: IamElectro
Engine braking is achieved when the pistons have to overcome the high vacuum created in the intake or push against a restriction in the exhaust in order to fall. Because a gas engine has a plate that blocks the entry of air into the intake manifold when the engine is decelarating, the pistons will have to fight the vacuum created in the intake in order to rise and fall. Compresion does not increase it stays the same.

I am sure I speak for a lot of gearheads when I say, WTF?

Who told you this? You need to read about basic engine functions.

The only thing you said that makes sense is that compression doesn't change.

 

[ndee]

Rodeo has nothing to do with a car duuuuuuuuuuude. Gear your self!

 

[GroundZero]

Originally posted by: DougK62
Engine braking does not add any more compression to the engine - that's absurd.

correct, your compression is determined by your rings and their amount of blowby, cylinder size, and stroke
it would put more stress on the bearings as they would rev higher, possible out of their rated range if the tranny is shifted into too low of a gear. about the only way to achieve higher compression in a motor would be to reduce the exhaust flow. say by plugging the exhaust and creating massive backpressure into the cylinder

(spelling correction)

 

[Iron Woode]

Originally posted by: GroundZero

Originally posted by: DougK62
Engine braking does not add any more compression to the engine - that's absurd.

correct, your compression is determined by your rings and their amount of blowby, cylinder size, and stroke
it would put more stress on the bearings as they would rev higher, possible out of their rated range if the tranny is shifted into too low of a gear. about the only way to achieve higher compression in a motor would be to reduce the exhaust flow. say by plugging the exhaust and creating massive backpressure into the cylinder

(spelling correction)

WTF?

Compression (very simply put) is determined by the ratio of volume of the cylinder at bottom dead centre and top dead centre.

Bearings rev higher? They don't rev.

Restricting exhaust has zero effect on compression. Compression is a mechanical function. All that would happen is you would blow up your exhaust manifolds or pipes/mufflers.