can I prevent coking with WMO?

[Brad S.]

Brownoiler, do you think that a little warmer air would aid in less soot???
I know power might be decreased, but I would take that for less soot or coking..

 

[The_Master]

Blownoiler,

If you guys want a cleaner burn you can wind down the amount of fuel injected for any particular boost pressure at the expense of a small drop in power.

There is no way to change the fuel/air mixture (use less fuel at a particular boost pressure). These are un-throttled motors. They always flow as much air as possible. You add fuel to make more power. Less fuel produces less power. We don't have any control over fuel/air mixture until the turbo starts opening the waste gate.

Newer diesels have variable geometry turbos and other tricks and may have the ability to increase the airflow at a given power setting without changing the fuel, but on all the older trucks, we don't have that option.

The only part of the entire system that we can readily control is the timing of the injection event. Sure, you can change cams and mod the motor to do things that it was not meant to do, but as far as a stock motor, all we can do is adjust timing.

This is why we think about changing some other things that we can control, like fuel heaters, and water injection.

Brad, I do think that intake temperature is important. That is why many people report better success in the summer vs. winter. Again, this has a lot to do with the vaporization of the fuel mixture. It seems that some of the Ford IDI folks don't has as much of a problem as the direct-injected guys burning alt fuels... That seems to be because of the more complete vaporization that is accomplished in those motors (at the expense of some loss of efficiency).

 

[Brad S.]

Brad, I do think that intake temperature is important. That is why many people report better success in the summer vs. winter. Again, this has a lot to do with the vaporization of the fuel mixture. It seems that some of the Ford IDI folks don't has as much of a problem as the direct-injected guys burning alt fuels... That seems to be because of the more complete vaporization that is accomplished in those motors (at the expense of some loss of efficiency).

Thanks for the confirmation on the incoming air temp vs. power or loss of power.
I think that "warmer" fuel helps in two areas, viscosity & "burn rate".
Since most alt fuels contain a high amount of some kind of waste oil it takes "longer" to burn.
Think we've all read here on the OB about advancing timing and how it helps when burning wmo.

A person could set up our IDI's to pull in warmer air, then after certain amount of time check the injector tips, then clean the tips, then run wmo like normal with "colder" air incoming, then check the injector tips again.
(I might try this once I'm up and running again)

 

[Blownoiler]

Brownoiler, do you think that a little warmer air would aid in less soot???
I know power might be decreased, but I would take that for less soot or coking..

Actually it's "Blown oiler", but maybe "brownoiler" better describes used veg oil users!
I'm not familiar with your particular engine, but if you observe tailpipe smoke levels during a cold snap then it becomes obvious that the intake air can be too cold for complete combustion. On a cold morning (0* C) (32*F) last winter my engine would smoke until nearly fully warmed up (around 5 minutes), then the smoke would disappear. This is an IDI engine running U.C.O.. My friends later model direct injection engine also smoked for the first minute or 2 of operation on the same cold morning, and that runs on 100% diesel fuel. The problem with using an underhood source for a warm air intake is e.g.t.s under full throttle/high load conditions, but that's why we run a gauge. I can easily adjust the fuel delivery on my engine as it uses a rotary pump with an adjustable fuel screw, and also a boost compensator which is simple to recalibrate. If I bleed some of the boost pressure from the turbo to boost compensator line then the compensator delivers less fuel for the same amount of boost, which means less smoke along with less power. The IDI's pintle injectors help a lot too, they don't block up at all in my experience.
Edit: An underhood air intake pipe also takes advantage of the higher air pressure that exists under the hood when the vehicle is moving, so the turbo doesn't have to work as hard to flow the same air volume into the engines intake, so creates less backpressure on the turbine side. Sucking underhood air also reduces drag, or wind resistance which translates to a small gain in aerodynamic efficiency. An intake pipe (from the air cleaner canister to the open air) can be designed to take advantage of the Helmholtz effect, another efficiency gain, by trying different lengths to match the pulse to a certain rev range(usually cruise revs)

 

[Brad S.]

Sorry about the Brown from Blown, thats my brain reading to fast with something thats not there.

Thats interesting about your experience with colder temps.
Before I did anything with alt fuels, did a lot of reading about others and some problems with cold temps.
So I put a 3rd tank in, I start on regular diesel, then switch over to wmo. Sometimes during really cold weather I wouldn't switch over to wmo, too afraid of having problems when its below zero.
Very interesting about the underhood intake stuff, thanks for that info, keep it comig...

One thought I had about all of this type of intake air temps etc, I would experiment during summertime temps, with winter temps(in the upper midwest, US) a person could pull in air from under the hood and be safe, IMHO

 

[Blownoiler]

Sorry about the Brown from Blown, thats my brain reading to fast with something thats not there.

haha, nobiggie!

Thats interesting about your experience with colder temps.
Before I did anything with alt fuels, did a lot of reading about others and some problems with cold temps.
So I put a 3rd tank in, I start on regular diesel, then switch over to wmo. Sometimes during really cold weather I wouldn't switch over to wmo, too afraid of having problems when its below zero.
Very interesting about the underhood intake stuff, thanks for that info, keep it comig...

One thought I had about all of this type of intake air temps etc, I would experiment during summertime temps, with winter temps(in the upper midwest, US) a person could pull in air from under the hood and be safe, IMHO

Maybe running 2 pipes into the air cleaner canister could be good, one pipe drawing in cold air, and the other warm underbonnet air, both close to the same length to preserve the Helmholtz effect. It's good to shoot for low or no smoke from the tailpipe, as unburnt or partially burnt fuel tends to collect in the ring pack, effectively glueing the rings into the grooves, which leads to low compression etc. 2 ways to avoid fast tar buildup has to do with driving style, 1/ make sure that the engine doesn't idle for long periods, and 2/ work the engine hard if possible, as high revs and high boost conditions tend to help keep deposits from forming and from sticking to engine parts.

 

[idiabuse]

My truck only smokes after using wmo only for a few hundred miles then it smokes at idle and generally too much smoke, I add Diesel Kleen and the smoke will clear and it will have a clean idle and low smoke while accelerating moderately.

 

[The_Master]

The 12Valve Cummins I run is a direct injected motor that does not have glow plugs. Alternatively for cold starts, Cummins used something called a grid heater which is mounted in the intake manifold. It is basically a big resistive coil that draws power from the electrical system and only cycles on cold starts. This effectively warms the intake air and allows combustion to take place cleanly. I have almost never had prolonged smoke (more than a couple seconds) on startup because of this.

So yes, I believe warmer air (to a point) is a good things for our diesels and will definitely help the fuel to burn properly.

Blownoiler, with regards to your boost compensator, that is basically a device that retards the amount of fuel deliver at a particular boost pressure to allow the turbo to spool correctly.

Let's think about what is happening, if you hold your foot steady with the truck in gear under load, (let's say: 1,500RPM, 10PSI) and the waste gate on the turbo is shut off, meaning the turbo is making maximum boost for the given power setting). If you increase boost feedback to the boost compensator, you are going to cause the pump to back-off on the fuel delivered. This will cause a loss of power and a decrease in the amount of boost and therefore airflow and the motor will find equilibrium at a new lower power setting, but you will not have effected the fuel/air mixture. The ONLY reason for the boost compensator is during the increasing of power. At a constant established power setting, the boost compensator can not affect the fuel/air mixture.

Boost Compensator, or Air-Fuel Controllers are used to retard the fuel for two main reasons: meet current Smog/Pollution requirements, and facilitate the quick spooling turbo (just enough, but not too much fuel for a given airflow rate).

The only way to change the air-fuel mixture of a diesel motor while you are under a constant load is to increase the airflow (less restrictive intake/more aggressive turbo, less restrictive exhaust, etc) or possibly change the timing of the ignition event to lead to more energy available at the turbine side of the turbo and thereby increase boost, or change the valves/valve/timing to cause the motor to breath better.

As for the concept of the under-hood air pressure helping, you need to do a serious analysis to check and see if the under hood air is actually any higher pressure. It may very well be lower air pressure. As counterintuitive as it seems, the air exiting the engine compartment under the vehicle may actually produce an air-vacuum under the hood. This will change depending on the design of the engine compartment and other factors, such as vehicle lift, etc. Just don't make assumptions without checking your particular situation.

 

[The_Master]

FYI with my motor 5.9 Cummins 12Valve, if I have good clean injectors I can burn 100% 80/20 (80%WMO, 20%RUG) without any smoking, even at idle.

The problem arises after about 800-1000miles of burning the mixture and I begin to get white/grey smoke at idle. I have proven that I can pull my injectors, clean the tips of carbon, replace the injectors and instantly have the previous no-smoke condition.

The problem is I drive a lot, and this would require me to pull injectors once a week to maintain a clean burn. That is not acceptable IMHO.

 

[Blownoiler]

The 12Valve Cummins I run is a direct injected motor that does not have glow plugs. Alternatively for cold starts, Cummins used something called a grid heater which is mounted in the intake manifold. It is basically a big resistive coil that draws power from the electrical system and only cycles on cold starts. This effectively warms the intake air and allows combustion to take place cleanly. I have almost never had prolonged smoke (more than a couple seconds) on startup because of this.

I am familiar with the grid heaters fitted over the years to various makes/models, I might price a few to see if I can afford to set one up on my vehicle. How many amps would the typical grid heater draw?

So yes, I believe warmer air (to a point) is a good things for our diesels and will definitely help the fuel to burn properly.

Agreed!

Blownoiler, with regards to your boost compensator, that is basically a device that retards the amount of fuel deliver at a particular boost pressure to allow the turbo to spool correctly.

That isn't how the bosch designed rotary pump works Mr themaster, the pressure activated boost compensator adds fuel as the boost pressure rises. I can disconnect the turbo to compensator hose and still get full boost, but no extra power. The diaphragm on the compensator can be turned to give either more or less fuel for the same boost level, and the spring under the diaphragm is also adjustable for tension so one can delay the onset of adding fuel under boost, or quicken up the enrichment...until visible smoke becomes a problem. These particular turbo-diesels (Isuzu 4jg2) spool the turbo while coasting down hills on no throttle. 3000 revs coasting = around 3 pounds of boost in the intake due to the small turbine size. Revving the engine at standstill gets the boost gauge up to 9 pounds, a bit different to your Cummins setup no doubt! Here is a link showing the internal workings of the rotary pump- http://www.autospeed.com/cms/article.html?&A=109345

Let's think about what is happening, if you hold your foot steady with the truck in gear under load, (let's say: 1,500RPM, 10PSI) and the waste gate on the turbo is shut off, meaning the turbo is making maximum boost for the given power setting). If you increase boost feedback to the boost compensator, you are going to cause the pump to back-off on the fuel delivered. This will cause a loss of power and a decrease in the amount of boost and therefore airflow and the motor will find equilibrium at a new lower power setting, but you will not have effected the fuel/air mixture. The ONLY reason for the boost compensator is during the increasing of power. At a constant established power setting, the boost compensator can not affect the fuel/air mixture.

Boost Compensator, or Air-Fuel Controllers are used to retard the fuel for two main reasons: meet current Smog/Pollution requirements, and facilitate the quick spooling turbo (just enough, but not too much fuel for a given airflow rate).

This may be relevant for your engine The-master, I don't have any knowledge of the Cummins line-up.

As for the concept of the under-hood air pressure helping, you need to do a serious analysis to check and see if the under hood air is actually any higher pressure. It may very well be lower air pressure. As counterintuitive as it seems, the air exiting the engine compartment under the vehicle may actually produce an air-vacuum under the hood. This will change depending on the design of the engine compartment and other factors, such as vehicle lift, etc. Just don't make assumptions without checking your particular situation.

It is a good idea to tape a manumeter probe in various positions to check for the best pressure, the concept came from the diesel performance book by Joe Pettit, although he suggests situating the intake pipe out in front of the radiator support panel for cool higher pressure air, obviously for a diesel fuelled engine rather than a heavy oil fuelled motor.

 

[Blownoiler]

My truck only smokes after using wmo only for a few hundred miles then it smokes at idle and generally too much smoke, I add Diesel Kleen and the smoke will clear and it will have a clean idle and low smoke while accelerating moderately.

Does the amount of smoke change from summer conditions compared to winter?

 

[Blownoiler]

FYI with my motor 5.9 Cummins 12Valve, if I have good clean injectors I can burn 100% 80/20 (80%WMO, 20%RUG) without any smoking, even at idle.

The problem arises after about 800-1000miles of burning the mixture and I begin to get white/grey smoke at idle. I have proven that I can pull my injectors, clean the tips of carbon, replace the injectors and instantly have the previous no-smoke condition.

The problem is I drive a lot, and this would require me to pull injectors once a week to maintain a clean burn. That is not acceptable IMHO.

Have you tried improving atomisation of the fuel through higher injector pop pressures?

 

[The_Master]

I am familiar with the grid heaters fitted over the years to various makes/models, I might price a few to see if I can afford to set one up on my vehicle. How many amps would the typical grid heater draw?

I believe they pull somewhere around 220A @12V, but it is cycled, not full-time.
This is an interesting thread discussing the topic:
http://www.thedieselstop.com/forums/f33/dodge-cummins-intake-heater-grid-s-183104/

That isn't how the bosch designed rotary pump works Mr themaster, the pressure activated boost compensator adds fuel as the boost pressure rises. I can disconnect the turbo to compensator hose and still get full boost, but no extra power. The diaphragm on the compensator can be turned to give either more or less fuel for the same boost level, and the spring under the diaphragm is also adjustable for tension so one can delay the onset of adding fuel under boost, or quicken up the enrichment...until visible smoke becomes a problem. These particular turbo-diesels (Isuzu 4jg2) spool the turbo while coasting down hills on no throttle. 3000 revs coasting = around 3 pounds of boost in the intake due to the small turbine size. Revving the engine at standstill gets the boost gauge up to 9 pounds, a bit different to your Cummins setup no doubt! Here is a link showing the internal workings of the rotary pump- http://www.autospeed.com/cms/article.html?&A=109345

This is very interesting and shows that your motor uses a significantly different setup than the Cummins truck motors. It appears that your injection pump does boost fuel enrichment, which is the opposite of the Bosch P7100 pump that my truck uses. Your pump adds fuel according to boost. My AFC inhibits fuel flow until suitable boost is achieved. The net effect is the same, but the regulation methods are opposites. It also appears that your turbo is quite a bit... higher-strung than mine. I have my waste gate capped off. I always run 100% boost.

My apologies. I made some assumptions without knowing your setup.

On my truck, there is no way to increase airflow without increasing RPM or fuel delivery. It appears that you have a little more flexibility.

It is a good idea to tape a manumeter probe in various positions to check for the best pressure, the concept came from the diesel performance book by Joe Pettit, although he suggests situating the intake pipe out in front of the radiator support panel for cool higher pressure air, obviously for a diesel fuelled engine rather than a heavy oil fuelled motor.

I completely agree. A ram-air intakes that use the income velocity of the air to increase the intake pressure, as well as ensuring a cool air supply are definitely good performance improvements. The question becomes when we want warmer air...

 

[The_Master]

Does the amount of smoke change from summer conditions compared to winter?

I do not have sufficient data on that question yet. However, even in winter, if my injectors are clean, there is no smoke. I suppose the real question is, do I have more/faster coking in winter vs. summer, and I suspect the answer to that question is yes.

 

[The_Master]

Have you tried improving atomisation of the fuel through higher injector pop pressures?

I have not tried that yet, but I suspect that my injectors are a little tired, as to my knowledge they probably have over 300kmiles.
On diesel they run fine, so I have not pursued changing them.