engine braking

Does engine braking use more fuel because of higher rpm causing a greater vaccume pressure in the lines of a diesel 2H.

[Lookfar]

Nope,
The engine braking is caused by the high compression of the diesel engine. There is no throttle butterfly, the air induction is wide open. The throttle is connected to the injector pump only, and it is the amount of fuel that is being delivered that controls the engine speed.

This being the case, these engines do not generate sufficient vacuum to reliably operate the brake booster, so a vacuum pump is usally attached to the rear of the alternator

is engine braking better to use than using foot braking. Does it damage the motor? ???

[Orbit]

engine breaking won't damage your engine...unless you select a gear that will push it into the red.

A combination of both is bestl.

[mudpiggy]

Mate if you have ever experienced brake fade where the person before you have been too heavy on the brakes you will understand that compression braking is essential in our vehicles..........and no it won't damage your engine unless like already stated if you make it rev it tits off frequently.....

[Orbit]

haha classic example of that!
going down the tumut "escarpment"
followed a automatic monaro down, i drive it pretty regularly so no the road pretty well, and it's a 2nd and 3rd gear descent the whole way only needing ot tap the breaks every so often to keep controll and what not. this guy accelerated though each straight bit hit the breaks hard around each corner the whole way down...i stayed about 50m from him more or less the whole way coasting along, no aggresive driving just nice and sensible...i could smell pad burn about 1/3 the way down he had to have massive fade....we stopped at the bottom to have lunch and so did he wheni walked past his car you could smell the breaks and see where he had melted the pad :o
if only he realised what that gear slect lever was about he might have had more luck. lol i jus think he needed to learn to drive better lol

[CatMan]

Typically when diesels go into 'overun' the flyweights in the governor don't have to balance a compressed throttle spring & therefore put the pump into zero fuel delivery, so basically in overun the fuel to the injectors is shutoff, which is why the engine braking is so good as it is the compression that retards the vehicle. Just think how much better it would be with a jake brake. Rob.

[mudpiggy]

I wonder if an exhaust brake would be like my first car which was a nissan pulsar.........it had a similar brake system where if i turned the aircon onto full it would take so much power from the engine it would almost stop on the spot........... ;D...........hahaha

[disco_nex]

had to be a N12 pulsar! If it was, mine was the same, wasnt work turning it on, only good as what you said!

[plcains]

Brakes pads are cheaper to replace than gearboxes ;)

[Peter ST_R]

is engine braking better to use than using foot braking. Does it damage the motor? ???


If you are locking the wheels up at high speed then yeah, your will damage your motor and the rest of your vehicle's drivetrain.

Crawling down a steep hill in 1st-4L with foot off the brake as prescribed is a classic example of engine breaking that will not damage your vehicle.

It's like all things, the harder you drive it the quicker you break it.

[HJ60]

Nope,
The engine braking is caused by the high compression of the diesel engine. There is no throttle butterfly, the air induction is wide open. The throttle is connected to the injector pump only, and it is the amount of fuel that is being delivered that controls the engine speed.

This being the case, these engines do not generate sufficient vacuum to reliably operate the brake booster, so a vacuum pump is usally attached to the rear of the alternator


I take it you have never had or worked on a Toyota 2H engine before, as these engines do have a butterfly which the throttle cable is conected to.

The anoumt of fuel requiered by the engine is determined by the govenor in the injector pump.

[dogbreath_48]

[quote author=stu050 link=board=7;threadid=20564;start=0#msg317555 date=1153571161]

The anoumt of fuel requiered by the engine is determined by the govenor in the injector pump.

Also determined by the pressure difference across the butterfly, i believe.

I can't get my head around any theory to explain it, but my 2H troopy always gets stinky (smells rich) when i'm on the overrun for long periods with the throttle closed/near closed. I suppose it sould well be using more fuel - i might be better off the the throttle as far open as i can get it without fuelling. It doesn't get visibly smokey so i don't think it's too much of a worry.

-Stu :)