[shnaggs]

Originally Posted by DWR

I think you are right.
For that matter, maybe even a threaded plug, staked on the threads.

Not sure if I'm spreaken your guy's deutch, but do you mean making a plug for the IWG hole?

[HeatherM35d]

Originally Posted by shnaggs

Not sure if I'm spreaken your guy's deutch, but do you mean making a plug for the IWG hole?

No, rather a deadman rod to keep the wastegate closed in the regular actuator location.

[shnaggs]

Now I spreaken ze duetch!!!

[DWR]

Originally Posted by shnaggs

Not sure if I'm spreaken your guy's deutch, but do you mean making a plug for the IWG hole?

Yes, that is what I meant. Not saying it is a better idea, just fewer parts.

[DWR]

Trying not to jack other threads, I am responding to posts regarding pre turbine exhaust configurations here.

Here's some work I did a while ago to understand what performance improvement, if any, could be gained be changing the exhaust manifold. The engine being simulated is a stock 335d.

In the first graph, the primary exhaust pipe diameter and length on an equal length manifold are being varied.

Second graph is showing the exhaust port pressure and velocity by crank degrees for the short and long pipe length. You can see the resonances in the pipe, which helps explain why the small, long pipe in the 1st chart has 2 peaks.

We can also see that impulse tuning, i.e. high velocity spikes can be beneficial if they are timed correctly. Exhaust gases are rapidly exiting at BDC, which is good. However, elsewhere in the cycle the longer pipe has advantages. At the finish line where the exhaust valve is closing near TDC, the longer pipe has lower pressure and lower negative velocity. This means less residual exhaust gas will be left in the combustion chamber.

With more gas flow at high HP, the situation will change somewhat, specifically at higher rpm where velocities can get too high for smaller pipe sizes

[DWR]

BTW, 6 cylinder engines respond best to wave/resonance tuning, if they can be split into separate 3 cylinders groups with timing phased 240 crank degrees apart. That's when you get a split turbine with a snake's nest of pipes. The problem with those manifolds can be tremendous heat loss - lots of surface area.

I like fabricated cast iron for turbo applications. It is tough and it has a unique property virually no one takes advantage of. In the world of metal, rust is a good insulator. Yep, put those new manifolds in a salt bath, let 'em rust up a little, then clean up the mating surfaces (I know some of you are saying this guy is crazy. This is not an advanced mod!). Sounds crazy, but it works if you can't afford a ceramic coating - which does look a lot nicer.

[HeatherM35d]

Originally Posted by DWR

BTW, 6 cylinder engines respond best to wave/resonance tuning, if they can be split into separate 3 cylinders groups with timing phased 240 crank degrees apart. That's when you get a split turbine with a snake's nest of pipes. The problem with those manifolds can be tremendous heat loss - lots of surface area.

I like fabricated cast iron for turbo applications. It is tough and it has a unique property virually no one takes advantage of. In the world of metal, rust is a good insulator. Yep, put those new manifolds in a salt bath, let 'em rust up a little, then clean up the mating surfaces (I know some of you are saying this guy is crazy. This is not an advanced mod!). Sounds crazy, but it works if you can't afford a ceramic coating - which does look a lot nicer.

Hey I remember from diesel school,(over a decade ago) in welding class they taught us that something like 1/8" of rust has the same insulating properties as something like 1/2"+ of steel.. I can't remember the exact numbers but i was amazed.. It's the air pockets and layers correct? How's this manifold look

[tuikku]

.
Wrong thread

[tuikku]

Originally Posted by HeatherM35d

Hey I remember from diesel school,(over a decade ago) in welding class they taught us that something like 1/8" of rust has the same insulating properties as something like 1/2"+ of steel.. I can't remember the exact numbers but i was amazed.. It's the air pockets and layers correct? How's this manifold look

It seems to me that the air is forced to somewhere where it does not want to go.

[Charged]

Yes, cummins exhaust is good, yes you can get 1300hp with single turbo, and yes you can get 1700hp with two turbos.
Were talking BMW engines here with about +500hp engines

[HeatherM35d]

Originally Posted by tuikku

It seems to me that the air is forced to somewhere where it does not want to go.

I don't even know what you're talking about

[HeatherM35d]

Originally Posted by Charged

Yes, cummins exhaust is good, yes you can get 1300hp with single turbo, and yes you can get 1700hp with two turbos.
Were talking BMW engines here with about +500hp engines

It's all the same concepts.. Compounded turbos and rusty exhaust manifolds, you didn't mention anything about Mercedes diesel being brought up 10 times on a BMW forum?

[NC335d]

Originally Posted by HeatherM35d

It's all the same concepts.. Compounded turbos and rusty exhaust manifolds, you didn't mention anything about Mercedes diesel being brought up 10 times on a BMW forum?

I see a 2 man circle jerk happening in Finland right now. Unfortunately, Heather darling, it looks like you weren't invited. Best to let them big bois do their thang.

[petey_highboost]

Guys. I've got a mercedes diesel

[DWR]

OK, back to serious matters ...

I probably should have given more explanation to the 2nd chart.

We often just think about the pressure differential across the turbine as the driving force. However, a well designed manifold can change that. The energy transferred to the turbine is a combination of pressure and velocity. Usually, in that order of magnitude. If the velocity of the exhaust gas is high enough it can transfer significant momentum to the turbine. It is called kinetic energy and it is proportional the the velocity squared. Meaning if you double the velocity, the energy is quadrupled. On the other hand, potential energy, in the form of pressure is linear. Double pressure differential, double the energy. The two forms of energy are different.



In the chart above, the shorter pre turbine pipe can transfer more than twice the kinetic energy of the longer pipe. The cylinder evacuation is not as efficient with the shorter pipe, but the transient response of the turbo is much improved. There is no free lunch, just decisons in compromise. On a dyno, the long pipe may look like the winner, but driven on the street it may come up in second place.

[Charged]

Originally Posted by HeatherM35d

It's all the same concepts.. Compounded turbos and rusty exhaust manifolds, you didn't mention anything about Mercedes diesel being brought up 10 times on a BMW forum?

Sorry, I like cummins engines as well, like mercedes also.

[DWR]

Many months ago, iaknown and I discussed the onset of detonation with H20/Methanol injection, in mid range rpm full load operation. After a good amount of data logging and research, the cause of the detonation can now be explained.

The first diagram illustrates piezo injector operation,with pilot, main and post injection events. One of the desireable attributes of multiple injections is a softer combustion process that reduces noise. Under full load, only 1 pilot injection exists. After 3,800 rpm, there is only the main injection.



In H20/Methanol, the ignition of methanol is initiated by the presence of burning diesel. Diesel ignition is delayed somewhat after the start of diesel injection. By datalogging the injection events and making an approximation of diesel ignition delay, the ignition point of methanol can be estimated. This can be compared with the spark ignition knock limit of methanol. That limit depends on many factors, including boost pressure and IAT.

The second diagram, shows the pilot and main injection timing and duration at full load,from 2,500 to 4,500 rpm. The ignition of diesel is delayed from earliest injection event. We can see the rise of advanced injection timing, until the pilot injection stops, at which point ignition is due only to the main injection.



Depending on the exact methanol knock level (also dependent upon the amount of methanol injected) and diesel ignition delay, detonation can start between 3,000 and 3,500 rpm. The end of detonation is well defined by the end of pilot injections, at 3,800 rpm.

Interestingly, as the boost pressures increase with the hybrids, another limiting factor comes into play. The autoignition temperture of methanol is @ 870F. Higher boost means the combustion chamber temperature is going to reach that autoignition temperature sooner in crankshaft degrees. If no preventative measures are taken, at some point, methanol autoignites before diesel ignition and before the knock limit.

[TDIwyse]

Excellent, thanks.

Curious as to your thoughts/analysis on how the water percentage affects the methanol ignition delay.

[DWR]

H20 injection is a good way to control heat rise during compression. Given the situation above, the optimal ratio of H20/Methanol is not the same at all rpms and load. In addition, it also looks like a 2 stage H20/Methanol injection system, whether that is accomplished by PMW or solenoids and nozzles has some merit.

[DWR]

Originally Posted by TDIwyse

Curious as to your thoughts/analysis on how the water percentage affects the methanol ignition delay.

Methanol burns much quicker than diesel and is a single phase combustion process. Diesel is two phase, with the first phase being much slower than the second. Delay in methanol ignition is really due to the delay of diesel ignition. Water slows down the combustion speed/heat release of both diesel and methanol. Unfortunately, we would like to speed up diesel in the upper rpms.

There are substitutes for methanol that have higher BTU values, higher autoignition temperature and slower combustion rates. What they don't have is methanol's incredible evaporation rate and cooling effect.

[tuikku]

.
The main thing in main injection is not, when it starts, but when it ends.
The start of main injection is calculated so, that it last and stops ~5-7° after tdc.
"The principle of good combustion"
Very often stock injectors are rated so, that in max power revs, main injection lasts ~1ms.
1ms duration is 24°/4000rpm at crank.
The max injection time at 4000 rpm is ~1,5ms (=36°), longer duration produces practically only smoke and heat stress.
It means that the main injection have to begin ~30°/4000rpm before tdc.

The true amount of injection is the most important single information in the program.
In almost every power function calculation ecu needs injection amount information.
If it is told wrong, nothing works properly any more.
This is not so easy job in BMW program...

[DWR]

Originally Posted by tuikku

.
The main thing in main injection is not, when it starts, but when it ends.
The start of main injection is calculated so, that it last and stops ~5-7° after tdc.
"The principle of good combustion"
Very often stock injectors are rated so, that in max power revs, main injection lasts ~1ms.
1ms duration is 24°/4000rpm at crank.
The max injection time at 4000 rpm is ~1,5ms (=36°), longer duration produces practically only smoke and heat stress.
It means that the main injection have to begin ~30°/4000rpm before tdc.

The true amount of injection is the most important single information in the program.
In almost every power function calculation ecu needs injection amount information.
If it is told wrong, nothing works properly any more.
This is not so easy job in BMW program...

I understand the point you are making. The principle behind the timing of injection is to get the peak combustion pressure to hit @ degrees 13 ATDC (some will disagree a degree or two). It is a function of the mechanics of making power, and is true for diesel, gas, methanol, propane,etc. That's why spreading the injection over many degrees does not turn into work, just stress and heat. That is why piezo injector multi injection will make less power than a one shot solenoid, for the same amount of fuel - everything else being the same.

That's also why multi fuel operation with varying combustion rates is very tricky. In the case of running methanol with diesel, the optimal power point is actually going to be suboptimal timing for either fuel, separately.