Silly thread for the night: Exhaust brake for petrol cars...

[mullett]

Ok, so we've all seen the exhaust brake work on a truck, I imagine it's simply a soleniod-controlled restriction, which creates huge backpressure in the exhaust, effectively increasing the compression braking capacity of the engine. Soooo...what happens if you do this to a standard petrol motor? Disaster?

Robin.

[slide86]

too much compression in the cylinder causing things to break????

ie ring or piston.

exhaust gas going back through the inlet????

diesel are designed to take heaps of compression, so thats why they can get away with it. but i dunno how much a petrol engine can handle.

just some thoughts/ideas. im no diesel expert

[mullett]

mmm, likewise. The compression would be huge, but I don't think it'd be worse than a detonating mixture of petrol and air...

RM.

[hybridaddy]

A diesel engine has no throttle and flows the same amount of air at any given rpm regardless of how hard your foot is down on the pedal.
It is this airflow that is restricted by the exhaust brake,slowing the engine speed.
Because a petrol engine has its air supply cut off before the cylinder it will not have any engine braking effect by using an exhaust brake.

ps im stuck on 10 rep lol!

[mullett]

You're right, I just had a bit of a look at that. The fuel control is governed, not the air. Hmm. So how about an exhaust restrictor anyways? Although, I guess if there's no air going in (throttle closed), no air comes out anyway, so it'd have no advantage. Hmmm...

RM.

[nick.parker]

Hehe,
So all you need now Robin, is a diesel engine for your AW11 sweeeeet - you'd be the first and could laugh at the other AW11 SC's "Huh, you think you've got torque!"
Imagine the surprise when people hear this loud exhaust brake and turn around and see an MR2, might be the next 'in' thing after loud blow off valves.
Nick.

[roadsailing]

truck brakes are not simply a restriction in the exhaust, google "jake brake" for how they work, when you engine brake it does a "dry" compression stroke, which does not use up much energy.

get some decent brakes!

(although you could compression lockup easier)

[mullett]

Ahah! I always knew you were an ideas man! I'll get one of those china motors, the $500 20hp diesel ones, and boost it! Ownage! Regrind the cam with an angle grinder, port with a dermel, cardboard headgasket, silicone gaskets, dry sump (no oil, can of CRC spraying sideways into the block occasionally)...it'd be wicked!

RM.

Hehe,
So all you need now Robin, is a diesel engine for your AW11 sweeeeet - you'd be the first and could laugh at the other AW11 SC's "Huh, you think you've got torque!"
Imagine the surprise when people hear this loud exhaust brake and turn around and see an MR2, might be the next 'in' thing after loud blow off valves.
Nick.

[EldarO]

Ahah! I always knew you were an ideas man! I'll get one of those china motors, the $500 20hp diesel ones, and boost it! Ownage! Regrind the cam with an angle grinder, port with a dermel, cardboard headgasket, silicone gaskets, dry sump (no oil, can of CRC spraying sideways into the block occasionally)...it'd be wicked!

RM.

have it running off the cam ftw

Eldar.O.

[30psi 4agte]

have it running off the cam ftw

Eldar.O.

nah mate you could dash mount the nozzel and hook up a line to the eng so you could do it while driving

[Hiro]

You're right, I just had a bit of a look at that. The fuel control is governed, not the air.

RM.

Ahhh the joys of direct-injection compression-ignition...so simple and easy to understand. None of this wasted crap called a throttle or carbie, the engine just sucks in air whenever it needs it and the little tiny sprayers do the rest.