Diesel turbo questions.

Just have some quick questions about turbos. Since ive been here I have learned the virtues of turbos and have gleamed much information on this wonderfull object of much desire. My question is how to make more boost. Some of you have this wonderfull device called a "boost controller", and I am wondering if one of you could tell me how to work and if it could be put onto a stock diesel turbo.

The boost is controlled by a wastegate or in the case with newer diesels, variable nozzle area is often used. Older dieselengines usually used fixed geometry and no boost controlling devices, in that case you must reconfigure the turbocharger/engine.

A diesel engine also won't get any power increase from an increase in boost as the amount of fuel injected isn't related to airflow. To increase the power of a diesel engine the practical way is often to increase fuel, then increase the boost until the engine stops smoking.

Werd. Also why increasing boost can also increase fuel economy. Only diesels can increase airflow and see an increase in MPG.lol

But maximum power is usually limited by EGT. So intercoolers are sometimes a good idea as well as WI or AI.

Maximum power is more limited by exhaust emissions than exhaust temperature as there are more heat resistant turbine materials availible.

Using intercoolers increase the efficiency of the dieselengine.

Gasoline engines show a decrease in specific fuel consumption when their boost increase, or at least until they must go rich/retard ignition timing. But in the case of gasoline engines it's due to the higher output in relation to the constant friction losses in the engine where in the case of a diesel it's mainly due to the leaner mixture (better combustion).

To get any decrease in fuel consumption of a turbocharged gasoline engine one must go for a smaller engine with a similar power output.

Maximum power is more limited by exhaust emissions than exhaust temperature...

Would you explain that in more detail?

TIA

When the air/fuel mixture in a diesel engine gets rich particle emissions and fuel consumption tend to increase. This means that long before you have reached the temperature limit on the turbocharger materials currently availible you would fail to meet the emission demands on diesel engines.

The boost is controlled by a wastegate or in the case with newer diesels, variable nozzle area is often used. Older dieselengines usually used fixed geometry and no boost controlling devices, in that case you must reconfigure the turbocharger/engine.

A diesel engine also won't get any power increase from an increase in boost as the amount of fuel injected isn't related to airflow. To increase the power of a diesel engine the practical way is often to increase fuel, then increase the boost until the engine stops smoking.

The latest and greatest Deisels have VVT.


all the new body style F-series that have the 7.3 powerstroke are wastegated, as well as most caterpiller engines.


But yea unlike gasoline engines, where if you add more boost and not add fuel, you will go lean and deatonate which creates a shit ton of heat and breaks stuff. On a Diesel, you don't really have an Air/Fuel mixture, when the diesel is on it's intake stroke, all it does is intake air, then it compresses it. Then instead of a spark plug firing, fuel is injected.

Soooo it is pretty much impossible to pre deatonate a diesel engine unless your injectioin timing is way off, or if you have a leaky injector. Therefore if you "lean out" a diesel engine, all you do is add more air and maintain your fuel and accually get colder EGT's. Making for bad emissions, slow laggy turbo, and less HP.

On a diesel, power is fuel.

I am a technician for Caterpillar at their Peoria Proving Grounds. When I first started classes and learned about deisel engines, I was ammazed at how different a compression ingnighted engine was. Sometimes it was hard to grasp some concepts because I had gasoline engine engraved in my mind.

Alrite everyone! I've got an Escort 1.8 Turbo Diesel and I want to boost the turbo above stock settings using a manual boost controller and boost gauge to monitor it. Apart from increasing the amount of fuel going in is there anything else i need to do?

Also, what would be the maximum boost I'd be able to get out of it? i mean how do you know without blowing up your turbo? Are there any signs?

Cheers,
Jamie

Alrite everyone! I've got an Escort 1.8 Turbo Diesel and I want to boost the turbo above stock settings using a manual boost controller and boost gauge to monitor it. Apart from increasing the amount of fuel going in is there anything else i need to do?

Also, what would be the maximum boost I'd be able to get out of it? i mean how do you know without blowing up your turbo? Are there any signs?

Cheers,
Jamie

This for the original poster also,

A set-up that does not have a boost control at all can only be lowered with a boost control, not increased. I don't know if this applies to either case.

with diesels increasin boost increases tewmperature and leans out the combusion. his allows he diesel to burn better and can ive more power. you don need o increase the fuel oin o et more power but addin fuel will ive you even more ains.

you dont really need to do anythin else but an exhaust gas temperature auge is a ood hin to have in case he exhaust es too hot and melts your turbocharer.

sorry for the bad spelling, im on a public computer at my hotel in germany and the keyboard doesnt work very well.

Alrite everyone! I've got an Escort 1.8 Turbo Diesel and I want to boost the turbo above stock settings using a manual boost controller and boost gauge to monitor it. Apart from increasing the amount of fuel going in is there anything else i need to do?

Also, what would be the maximum boost I'd be able to get out of it? i mean how do you know without blowing up your turbo? Are there any signs?

Cheers,
Jamie

I don't like boost controllers much. I prefer to cut the wastegate actuator rod and put in a threaded section. Then you can wind boost both above and below stock levels without adding something hissing under your bonnet.

The turbo on my diesel truck motor had a wastegate set at the factory to start opening at 20psi and was fully open at 25psi.
I suspected it wasn't working properly so I stuck a bike pump and boost gauge on it.
The engine would only spin it to 19psi so it had never opened. On a truck that was two owners old.

Backing the boost off to 15psi gave the engine a little less midrange torque, but much better high end power as the turbo has much less restriction.
My exhaust pressure gauge tells me the backpressure runs almost exactly double the boost. So the difference between 30 and 38psi backpressure was significant.

If you're going to play with fuel and boost, then get a pyro gauge. They aren't cheap, but they're cheaper than melted pistons. 750 C seems to be the upper limit for exhaust gas temp. I don't run mine past 650.

I don't like boost controllers much. I prefer to cut the wastegate actuator rod and put in a threaded section. Then you can wind boost both above and below stock levels without adding something hissing under your bonnet.

The turbo on my diesel truck motor had a wastegate set at the factory to start opening at 20psi and was fully open at 25psi.
I suspected it wasn't working properly so I stuck a bike pump and boost gauge on it.
The engine would only spin it to 19psi so it had never opened. On a truck that was two owners old.

Backing the boost off to 15psi gave the engine a little less midrange torque, but much better high end power as the turbo has much less restriction.
My exhaust pressure gauge tells me the backpressure runs almost exactly double the boost. So the difference between 30 and 38psi backpressure was significant.

If you're going to play with fuel and boost, then get a pyro gauge. They aren't cheap, but they're cheaper than melted pistons. 750 C seems to be the upper limit for exhaust gas temp. I don't run mine past 650.

I think I can go along with this and reminds me that the turbine on most dsl engines are sized way too small accounting for the back-pressure. A good set-up that will make more power on less boost is when the intake pressure is greater than the exhaust pressure, but is hard to do, especially on a dsl.

I think I can go along with this and reminds me that the turbine on most dsl engines are sized way too small accounting for the back-pressure. A good set-up that will make more power on less boost is when the intake pressure is greater than the exhaust pressure, but is hard to do, especially on a dsl.

I've heard stories of people getting more boost than backpressure. But it'd require the biggest exhaust housing you can run and an extremely hot exhaust. Possible for racing applications, but not much good on the street.

Has anyone else measured boost vs backpressure?

I've heard stories of people getting more boost than backpressure. But it'd require the biggest exhaust housing you can run and an extremely hot exhaust. Possible for racing applications, but not much good on the street.

Has anyone else measured boost vs backpressure?

how the turbo works is off of pressure differential. There must be more flow over the turbine than the compressor is producing....otherwise you have what we like to call "perpetual motion" :screwy:

Although PSI does not equal flow directly, its definitely related.

I've heard stories of people getting more boost than backpressure. But it'd require the biggest exhaust housing you can run and an extremely hot exhaust. Possible for racing applications, but not much good on the street.

Has anyone else measured boost vs backpressure?

I think you are right on about the housing and exhaust. None of my systems ever had more pressure at the intake valves than at the exhaust valves, some Banks systems claimed that they did a long time ago. I wonder if they're in bus any more? I think it is far easier on a gas job than a dsl. I always just increased boost, because there was no max boost rules, :grinyes:

how the turbo works is off of pressure differential. There must be more flow over the turbine than the compressor is producing....otherwise you have what we like to call "perpetual motion" :screwy:

Although PSI does not equal flow directly, its definitely related.

The energy driving a turbine isn't just the pressure, it's also the temperature. The greater temperature differential you can get (i.e. very hot exhaust into turbine, cooler exhaust out) the less pressure differential you need.

It's not a perpetual motion machine until the compressor is doing more work than the turbine is creating.

I've got a spare thermocouple lying around, but I haven't yet measured the temp drop across the turbine.

It's not a perpetual motion machine until the compressor is doing more work than the turbine is creating.


uh....thats exactly what I said.

uh....thats exactly what I said.
You neglected the temperature part. It's entirely possible to have more boost than backpressure if the temps are high enough.

Work is pressure and temperature. Not pressure alone.

You neglected the temperature part. It's entirely possible to have more boost than backpressure if the temps are high enough.

Work is pressure and temperature. Not pressure alone.

flow is flow. As I said, pressure is one portion of the equation