Exhaust brake
- Thread starter dibs
- Start date
Help Support Nissan Navara Forum:
Yep, it only works in overdrive and lever in 'D' position. Similar for the torque converter lockup.
I was going to write a new thread about this but thankfully I searched first and found this one.
I notice Tweak'e says the exhaust brakes don't create a lot of heat, but I've done some research into the two types of engine brakes available and the exhaust brake would seem to create some - maybe not a lot, but maybe enough to tip the engine over the edge since they already run so bloody hot.
As for Jake brakes - forget them, you need to change the engine. A Jake (Jacobs) Brake works by opening the exhaust valve for most of the INTAKE up-stroke so that air doesn't get compressed. What's left is a vacuum - and it's powerful. It's also the reason for the loud rattling sound you hear in trucks as they slow down. Because you need to change the valve timing it'll mean a fair bit of work on the head - not sure it's worth it. They're illegal, in NSW (so I've read) and may be in other states too. They're also (I understand) not a great deal better than the exhaust brake.
Exhaust brakes use the opposite method. They're a valve in the exhaust that turns the engine into a compressor. For our Navara engines, these would be fairly easy to fit - they'd bolt onto the back of the turbo and a remodelled dump pipe would bolt onto the back of the exhaust brake. What we don't know is if the exhaust manifold and turbocharger can withstand the pressure created by the exhaust brake. I don't know the answer to this.
Has anyone investigated the idea? What about incorporating the brake into a replacement dump pipe?
The issues are heat generation and exhaust manifold strength. Could it be done?
I notice Tweak'e says the exhaust brakes don't create a lot of heat, but I've done some research into the two types of engine brakes available and the exhaust brake would seem to create some - maybe not a lot, but maybe enough to tip the engine over the edge since they already run so bloody hot.
As for Jake brakes - forget them, you need to change the engine. A Jake (Jacobs) Brake works by opening the exhaust valve for most of the INTAKE up-stroke so that air doesn't get compressed. What's left is a vacuum - and it's powerful. It's also the reason for the loud rattling sound you hear in trucks as they slow down. Because you need to change the valve timing it'll mean a fair bit of work on the head - not sure it's worth it. They're illegal, in NSW (so I've read) and may be in other states too. They're also (I understand) not a great deal better than the exhaust brake.
Exhaust brakes use the opposite method. They're a valve in the exhaust that turns the engine into a compressor. For our Navara engines, these would be fairly easy to fit - they'd bolt onto the back of the turbo and a remodelled dump pipe would bolt onto the back of the exhaust brake. What we don't know is if the exhaust manifold and turbocharger can withstand the pressure created by the exhaust brake. I don't know the answer to this.
Has anyone investigated the idea? What about incorporating the brake into a replacement dump pipe?
The issues are heat generation and exhaust manifold strength. Could it be done?
did i ?
any time you create back pressure you will trap some heat. however when brake is on, the fuel is off. so there is little heat anyway.
you don't have to fit them in the dump pipe. just downstream somewhere convenient will be fine. the further way from the manifold the more lag you get before it works, it takes a bit of time for the pipe to fill and pressurize. so don't fit it right at the end but many are a few feet away from the turbo.
the big problem is usually the egr system. block that off and it will be ok.
other trap is the exhaust brake not open enough or not bypass valve in it. that can cause rapid rise in exhaust pressure and can stall the turbo.
K
Krankin
Guest
My apologies, it was Dion.
I think the fewer joins that have to withstand the pressure the better (longer) it will last. That means somewhere as part of the dump pipe, I guess. I was reading somewhere that the exhaust brake doesn't stop the fuel from being injected - it basically puts in enough fuel to idle and that adds to the pressure. It will also add to the heat.
My concern with that of course is that our little 2.5s run very close to the thermal limit of the motor as it is, and raising the temp further is likely going to reduce the longevity of the motor.
If the exhaust brake requires blocking the EGR (and I do understand why, of course) then how do the trucks with exhaust brakes pass their emission controls - or, being classed as heavy vehicles, are they exempted from reduced NOx emissions?
It's not so much that you're "creating" heat, more that the heat that is already pouring out of your exhaust valves isn't being carried out the exhaust the way it once was. Idle fuelling is very little, and the computer-controlled diesels probably just about cut the injectors on coast anyway. The tuning is for an EGT limit under full boost, full fuel; they'll never reach anywhere near that limit without full throttle fuelling. So since the wiring of the exhaust brake doesn't allow for a closed event with any throttle input, you'll never create the high-heat conditions.
But an easy way to put your mind at ease is to have an EGT gauge fitted.
In a factory application, EGR butterfly would just close with the exhaust brake closing I'd have thought.
But an easy way to put your mind at ease is to have an EGT gauge fitted.
In a factory application, EGR butterfly would just close with the exhaust brake closing I'd have thought.
That makes a lot of sense, but that also means the EGR valve and its pipe around the front of our engines would have to withstand the extra pressure as well.
On our cars that pipe isn't big and doesn't look too solid. In fact, there's a section that looks like it's designed to absorb vibration, manufactured a little like a concertina. There's no way that would handle the pressure, so the EGR pipe would need to be replaced with something a lot sturdier, or blocked near the turbocharger. A sturdier pipe would not absorb the vibration, so whatever issues THAT was resolving would raise their ugly heads again.
I'd read somewhere that our diesels should nearly cut fuel while engine braking and the D40 auto has an engine-brake mode which kicks down a couple of gears. I watched my fuel rail pressure while inducing an engine braking and found the fuel rail pressure is still up around 4,000kPa which is the normal idle rail pressure.
My concern with the heat is that if we're adding only 20C to the thing, but we're only riding 10C below the tolerance level of the alloy, then we're into the danger zone. Hearing people say that their EGT gauge is hitting way over 700C (I've read some say well over 800C) doesn't boost my confidence any!
On our cars that pipe isn't big and doesn't look too solid. In fact, there's a section that looks like it's designed to absorb vibration, manufactured a little like a concertina. There's no way that would handle the pressure, so the EGR pipe would need to be replaced with something a lot sturdier, or blocked near the turbocharger. A sturdier pipe would not absorb the vibration, so whatever issues THAT was resolving would raise their ugly heads again.
I'd read somewhere that our diesels should nearly cut fuel while engine braking and the D40 auto has an engine-brake mode which kicks down a couple of gears. I watched my fuel rail pressure while inducing an engine braking and found the fuel rail pressure is still up around 4,000kPa which is the normal idle rail pressure.
My concern with the heat is that if we're adding only 20C to the thing, but we're only riding 10C below the tolerance level of the alloy, then we're into the danger zone. Hearing people say that their EGT gauge is hitting way over 700C (I've read some say well over 800C) doesn't boost my confidence any!
D
Dave
Guest
[YT]http://www.youtube.com/watch?v=Hpi4K14yw80[/YT]
Whats wrong with the sound ?
This Series 60 Detroit sounds good to me.
A lot of people on here have blocked their EGR. I don't think anybody would miss it if it was blocked.
What does your injector duty cycle read under those conditions?
Those times when they are reaching those exhaust temperatures are when there is max fuel and max boost, though, which is not when you're engine braking. So even if you are retaining exhaust heat, you'll still be well below any limit. It'd be good if someone with an EGT gauge and a YD25 could watch the temperature over a long downhill stretch. Then you'd have a baseline.
K
Krankin
Guest
Grrrrrrrrr
I'm trying to sleep...cant you mongrels read the bloody signs...."Avoid using engine brakes!"
K
Krankin
Guest
I really dont think our "factory" engines are tuned for running on the brink of component failure...
D40.....but then again.
no I'm not.
D40.....but then again.
no I'm not.
gunning1987
Member
[YT]http://www.youtube.com/watch?v=z3bLqjPBlx8[/YT]
C16 sound so much better
C16 sound so much better
K
Krankin
Guest
I cant put on here a vid of what sound I reckon is heaps better than those stupid 'jacobs',
but i may get banned.....
you's will have to look it up yourselves.....redtube.com
but i may get banned.....
you's will have to look it up yourselves.....redtube.com
K
Krankin
Guest
Anyways, back on topic...........
Last edited by a moderator:
That's very true, myself included. I was thinking about the situation where one might try to keep the emission control system legal, but true enough, I won't miss it!
That's a figure I can't get out of my software. I can get fuel flow rate but that will also include what's heading back to the tank, I'd imagine.
Engine load under those conditions does read 0%, but the LHPK figure calculated is positive (non-zero) which makes me think that there's going to be at least a small amount of fuel being squeezed in.
I've got to build and install my EGR gauge one day. I need an electrically insulated holder for the probe in the exhaust and then I'm off and running.
I keep going back to hills like the Great Dividing Range climb just to the west of here. It's a very steep climb with about 100m of modest peak followed by a steep descent. My little turbo would be glowing red-hot topping that rise, it's a bastard of a hill and worse it's single lane in both directions.
I do take your point though - once you're off the juice, the engine does start cooling again rather quickly. I watch my coolant temp when I'm climbing that same hill pass 107C and just over the top it's already heading back to 100C and it's back at low 90s by the first bend on the downhill side.
K
Krankin
Guest
Sure was. Temps don't go much over 96-97 when I'm not towing.
That's why I'm interested in an exhaust brake too. When going down hills, all 8 wheels are braking constantly and heating up. After some hills, all I can smell outside are hot brakes.
That's why I'm interested in an exhaust brake too. When going down hills, all 8 wheels are braking constantly and heating up. After some hills, all I can smell outside are hot brakes.
