Diesel Power Box

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Well, a diesel always runs lean anyway, since there's no throttle - you only adjust how much fuel you squirt in (in the N/A case). With a petrol engine running at the sort of AFRs that diesels run at you would melt the pistons for sure, but diesels handle it just fine. Thus it is at least plausible that there is enough margin for error in there to exploit to find the gains in both bhp and mpg figures. Whether that is what the "box" really does I have no idea - but conceptually, the possibility shouldn't be pre-emptively dismissed.

And yes, I probably read too many books. :p
 
gordan said:
Well, a diesel always runs lean anyway, since there's no throttle - you only adjust how much fuel you squirt in (in the N/A case). With a petrol engine running at the sort of AFRs that diesels run at you would melt the pistons for sure, but diesels handle it just fine. Thus it is at least plausible that there is enough margin for error in there to exploit to find the gains in both bhp and mpg figures. Whether that is what the "box" really does I have no idea - but conceptually, the possibility shouldn't be pre-emptively dismissed.

And yes, I probably read too many books. :p
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So you control a diesel engines speed by increasing or decreasing the amount of fuel injected. Do you agree? So what happens if your diesel engine is running steadily at 3000 rpm and you reduce the amount of fuel injected?
 
362bkr said:
I am wondering why it was disconnected.:confused:
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owner i bought it from was an older retired chap, and presume it was on there when he got it and he thought no need for it or something and dissconected it and wanted to leave it factory , have no idea, dont really care...all i need to decide is what to do with it myself
 
polsta said:
owner i bought it from was an older retired chap, and presume it was on there when he got it and he thought no need for it or something and dissconected it and wanted to leave it factory , have no idea, dont really care...all i need to decide is what to do with it myself
Click to expand...

Just connect it and see what you get. Then decide.
 
well thats the obvious soloution and do my 50 mile round trip to work a few times and work out mpg

but...in plugging it in, and unplugging- would the engines electronic mpg thing work the same for both and give a fairly accurate reading ?
 
Well all I can tell you about what I've found is that the increase in grunt is to good to miss out on so plug it in and see what you think,I bet you won't unplug it!!! As for the fueling debate I look at it like this, if your in town stop starting a lot you will us more fuel but on the motorway the extra grunt helps it stay locked up in top gear and so giving better mpg... As for the gadget on the dash telling you fibs pay no attention to it...
 
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wammers said:
So you control a diesel engines speed by increasing or decreasing the amount of fuel injected. Do you agree? So what happens if your diesel engine is running steadily at 3000 rpm and you reduce the amount of fuel injected?
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I'm not talking just about reducing the amount of fuel - I am talking about increasing the amount of air (by increasing the boost) without reducing the amount of fuel. For any given amount of fuel, increasing the amount of air should produce more power (at least up to a point). Since under steady state conditions you need a fixed amount of power to move at a constant speed, you could achieve that power with less fuel than before, hence the mpg improvement.
 
In a diesel engine the ONLY way to increase power output (BHP) and the Efficency of generating that power (TORQUE) is to introduce more fuel.

Increasing the amount of inducted air through increasing the boosted charge air will not increase the overall power curve (BHP against TORQUE and vice versa) without increasing the amount of introduced fuel...this is where many teenage tw&ts get it wrong with their turbo'ed Euro tin boxes and then end up melting pistons....

It is a paradox that many seem not to understand, if you lean out a mixture (introduce more charge air) the burn temperature goes up due to the production of excessivley high combustion chamber temperature as the fuel actually helps to reduce the combustion temperature in two main ways, the effect of evapourative cooling (like spraying your face with a fine mist of water) and also it slows the burn speed down making it technically a less energetic burn.

So if you increase boost pressure, you are introducing more air volume, leaning out the mixture and increasing combustion chamber temperature until you melt something.

A clean and efficent burn is ALWAYS a balance of Inducted Charge Air and Fuel, anymore of one will HAVE to be balanced by the other, or else something nasty will happen.

You CAN increase the density of the Charge Air by cooling it more through a more efficent intercooler, which will have the effect of introducing the same amount of burnable air but at a reduced volume, thus the required amount of fuel will be reduced as the ratio of inducted air (VOLUME - as measured by the MAF) will be less but retains the same calorific value (amount of energy that can be extracted from it).

Just my twopeneth.....
 
Saint.V8 said:
Increasing the amount of inducted air through increasing the boosted charge air will not increase the overall power curve (BHP against TORQUE and vice versa) without increasing the amount of introduced fuel...this is where many teenage tw&ts get it wrong with their turbo'ed Euro tin boxes and then end up melting pistons....

It is a paradox that many seem not to understand, if you lean out a mixture (introduce more charge air) the burn temperature goes up due to the production of excessivley high combustion chamber temperature as the fuel actually helps to reduce the combustion temperature in two main ways, the effect of evapourative cooling (like spraying your face with a fine mist of water) and also it slows the burn speed down making it technically a less energetic burn.

So if you increase boost pressure, you are introducing more air volume, leaning out the mixture and increasing combustion chamber temperature until you melt something.

A clean and efficent burn is ALWAYS a balance of Inducted Charge Air and Fuel, anymore of one will HAVE to be balanced by the other, or else something nasty will happen.
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What you are describing is true for petrol engines, but it doesn't quite translate directly for diesels. Diesels always run lean, the less throttle, the leaner it is. Except at full throttle, diesels run at AFRs that would melt pistons on petrol engines.
 
Errrrrr....I think you will find that it is correct for all forms of combustion engine.

Diesel engines don't run 'Lean'.

Diesel Oil has a higher calorific value than Petrol, i.e it creates more energy when it burns, thus why you can use less diesel for a given amount of air hence why diesels are more fuel efficent.

Yes the Air to Fuel ratio is different and as such that specific ratio would render a petrol engine useless, but a diesel fuelled engine DOES NOT run lean, it runs at the correct ratio to sustain a clean and efficent burn based on the characterisitics of the fuel.

Please do not try to school me on the theories of Thermodynamics or Propulsive Technology when you have no idea who I am or what my day job is.
 
gordan said:
I'm not talking just about reducing the amount of fuel - I am talking about increasing the amount of air (by increasing the boost) without reducing the amount of fuel. For any given amount of fuel, increasing the amount of air should produce more power (at least up to a point). Since under steady state conditions you need a fixed amount of power to move at a constant speed, you could achieve that power with less fuel than before, hence the mpg improvement.
Click to expand...

If you increase the amount of air you also have to increase the amount of fuel to maintain the mixture ratio. Why do you think turbo/supercharged engines use more fuel than normally asperated engines. Basically if you have an engine running at say 3000 rpm drawing air in at ambient pressure, fuel is introduced to maintain the best mixture ratio, around 14 to 1. If you have a turbo charged engine running at the same speed blowing at 14.7 psi you double the amount of air in the cylinder. Therefore you need twice the amount of fuel to maintain the mixture ratio. Theoretically you also get twice the power. With your famous electric waste gate if the engine is running light at 3000 rpm (cruising) it may not need full boost to maintain speed so fuel is being wasted. The ECU would sense this and open the waste gate. Reducing the boost pressure and therefore the amount of fuel needed to maintain mixture ratio. If at any time more power was needed, say on an hill the waste gate would close and give more boost more fuel more power to maintain speed. Simples.
 
I am pretty sure the Wammer knows this...but the waste gate (it is actually a by-pass plate - it reduces the amount of exhaust gas to reach the Turbine in order to slow it down rather tan dump excess charge air pressure - this mode of operation is often called constant boost Turbo Charging) on the Turbo fitted to the M51 is Mechanical, operated using a diaphram and set pressure spring connected to the compressor outlet.

Hence it will always try to maintain charge air at around 1atm (14.7psi - 1barg).
 
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Saint.V8 said:
I am pretty sure the Wammer knows this...but the waste gate (it is actually a by-pass plate - it reduces the amount of exhaust gas to reach the Turbine in order to slow it down rather tan dump excess charge air pressure - this mode of operation is often called constant boost Turbo Charging) on the Turbo fitted to the M51 is Mechanical, operated using a diaphram and set pressure spring connected to the compressor outlet.

Hence it will always try to maintain charge air at around 1atm (14.7psi - 1barg).
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So did you swallow or right the book on how engines work then?
 
lol....not quite.

I am a Design Engineer for a company that produces Hi-Bypass Gas Turbine and Jet Engine components.

My Degree was in Aeronautical and Aerospace Design Engineering, so I spent a lot of time reading lengthy and, at times, boring books and research papers....

I am just a Design Engineer, it is my job to get the things the Big Brains upstairs dream up to work...!!!
 
Saint.V8 said:
lol....not quite.

I am a Design Engineer for a company that produces Hi-Bypass Gas Turbine and Jet Engine components.

My Degree was in Aeronautical and Aerospace Design Engineering, so I spent a lot of time reading lengthy and, at times, boring books and research papers....

I am just a Design Engineer, it is my job to get the things the Big Brains upstairs dream up to work...!!!
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I didn't think you were just cutting and pasting from other pages (that's what I do now and then)
 
Saint.V8 said:
I am pretty sure the Wammer knows this...but the waste gate (it is actually a by-pass plate - it reduces the amount of exhaust gas to reach the Turbine in order to slow it down rather tan dump excess charge air pressure - this mode of operation is often called constant boost Turbo Charging) on the Turbo fitted to the M51 is Mechanical, operated using a diaphram and set pressure spring connected to the compressor outlet.

Hence it will always try to maintain charge air at around 1atm (14.7psi - 1barg).
Click to expand...

Yep the electric waste gate can control the speed and therefore output pressure of the turbo by reducing or increasing the gas to the turbo turbine blades. It can allow boost incrimentally up or down to suit load requirements. A mechanical waste gate as in the M51 cannot do this it is either on or off. A dump valve which some may confuse with this, is a totally different unit. Only really useful on high performance turbo engines. At high RPM on max boost if the throttle is shut quickly the high pressure air bounces back through the turbo stalling the blades. To prevent this, the depression caused in the manifold by closing the throttle, is used to open the dump valve, which as it's name suggests dumps excess high pressure air out of the system. Allowing the turbo to continue to spin.
 
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Great explaination of the different ways of controlling Boost pressure and Charge Air from the Wammer....a truly knowledgable fellow.

At college, we had a chap who fitted a ruddy great turbo and dump valve on his Renoult 5 Turbo....when that dump valve opened, it was like a shotgun going off....the level of Boost he was running was immense, but he had down it properly....the level of boost was monitored by an ECU that would adjust fuelling to compensate....he also had hardened piston crowns and con rods to take the extra pounding....it was reported (although never substantiated - through fear I reckon) he could in effect run any boost level he desired (due to the variable fuelling ECU) up to a point when the engine would disintigrate but this could be done without affecting combustion temperature or detonation.....
 
wammers said:
Yep the electric waste gate can control the speed and therefore output pressure of the turbo by reducing or increasing the gas to the turbo turbine blades. It can allow boost incrimentally up or down to suit load requirements. A mechanical waste gate as in the M51 cannot do this it is either on or off. A dump valve which some may confuse with this, is a totally different unit. Only really useful on high performance turbo engines. At high RPM on max boost if the throttle is shut quickly the high pressure air bounces back through the turbo stalling the blades. To prevent this, the depression caused in the manifold by closing the throttle, is used to open the dump valve, which as it's name suggests dumps excess high pressure air out of the system. Allowing the turbo to continue to spin.
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Indeed. A dump valve on a diesel engine would be a bit pointless, though, since there is no throttle - diesels always effectively run at WOT.
 
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