Diesel Dynamics pump kit first impression

[jbolt]

Kit arrived yesterday so I put it in this afternoon. As you can see from the picture below the DD pin has a compound taper vs. the straight taper of the stock pin. The spring supplied with the kit is softer than the stock spring.



My current setting of the star wheel is one full turn up from the lowest setting and the smoke screw is still factory stock but it is 1-2 turns away from being fully backed out. The nylon spacer is not used with the DD pin.



Test drive:



Idle- zero smoke. This is a nice improvement to the PODs. I will play with the smoke screw some to see where the smoke comes on.



Low boost acceleration from a stop- I get more blueish white smoke than stock eccentric at 70%. It needs about 4psi of boost to clear up. It does not have the same feel as the stock eccentric. The stock eccentric set at 70% was providing more fuel at zero boost than the DD pin so I'm getting a little more lag but the softer DD spring brings on the fueling a little faster. I can still spin the tires if I want to.



Highway speed- The DD pin really shined at highway speed. For part of the testing different settings I have been driving the same route and using the cruise control. The DD pin and softer spring make for quick throttle response. The route I'm driving is hilly and the speedometer needle never leaves the setting where as my factory setup had a lead-lag of 2-3 mph. Throttle pulls strong through 80mph. No smoke at WOT or Hard acceleration at speed



Boost & EGTs are about the same but I am hearing the turbo sucking more if I back off the throttle quickly.



Jay

 

[Case500D]

Good to hear

Hi Jay,



Good to hear you like your new pin. Mine is still on the way. I am interested to know if the low fuel rate can be improved with the star wheel and smoke screw to help reduce the turbo lag at an idle. Any chance of a milage test yet? Do you think the pin could be put in a lathe a couple of thousanths could be turned or polished off the bottom of the pin to increase the idle fuel just a bit? Thanks for the pictures too.



Jeremy

 

[BushWakr - RIP]

Jay, excellent detailed photo, thanks alot. .



Bob.

 

[Philip]

It must be nice to work on your truck all year round. :{



It will be spring before I get to try my fuel pin.

 

[BushWakr - RIP]

Jay, from the look of your picture, the contour of the cone is uniform all the way around. . is that correct?

I've wondered if an altered cone, like this one, or a stock one, could be modified to have an 'advanced/retarded' contour like our stock one. Ideally it would also be compound countor. Case500D is actually hinting at what I was thinking.

It would be nice to fine tune the contour so that you could go lean for the colder wetter winter months like we have, and then richen it up for the summer racing season.



Maybe I need to take my stock one down to a machine shop and see what they say. .

Keep reporting your findings, I'm really interested in this along with the other guys...



Bob.

 

[formula]

Originally posted by jbolt



Boost & EGTs are about the same but I am hearing the turbo sucking more if I back off the throttle quickly.



Jay

Jay,

The sound you're hearing is not sucking, it's the air blowing back out of the turbo. This is called "surge" or "bark" and it is not a good thing to subject the turbo to if you can avoid it.



Here's a quote from this thread :



"The actual engineering name is turbocharger compressor surge. The centrifugal compressor impeller on a turbocharger is a dynamic, not a positive displacement compressor. This means that it compresses air by accelerating the incoming air to a high velocity, then converting velocity energy to pressure energy. In simple terms, the only thing keeping the air from flowing backwards from the turbo compressor discharge (a high pressure area) to the turbo compressor inlet (a low pressure area) is that the turbo impeller is "stacking" more air into the discharge at that particular moment.



Ignoring the wastegate for the moment, at full throttle the engine is pumping hot exhaust gas into the exhaust manifold. The turbine section of the turbocharger converts the energy in this high pressure, hot exhaust gas into shaft horsepower which is used to drive the turbocharger's compressor impeller. The turbocharger will theoretically continue to accelerate until the drive horsepower equals the horsepower consumed by the compressor, less frictional losses.



When you suddenly let off the accelerator, the injection pump stops injecting fuel into the engine's cylinders. The exhaust temperature and pressure, relatively speaking, drop like a rock. This deprives the turbocharger's turbine section of drive horsepower. The turbocharger compressor, meanwhile, doesn't know anything has happened and is still compressing air like mad (its horsepower consumption hasn't dropped). Since the drive horsepower has dropped, the turbocharger rotor will decelerate. This deceleration decreases the "head" (discharge pressure minus inlet pressure) produced by the impeller. Since the head produced by the impeller is less than the actual compressor discharge pressure minus the compressor inlet pressure, the high pressure air in the intake system will flow from the discharge to the inlet side of the turbocharger compressor (reverse flow) until the pressure differential across the impeller is less than the impeller's head capacity. At that point, the impeller starts compressing air again.



We still have no drive horsepower with the throttle closed, however. This means the turbocharger rotor is still decelerating and the compressor impeller head continues to drop. Therefore, soon after the impeller begins compressing air again, the head will drop and airflow will reverse once again. This reversal of airflow is the "whoomp" or "bark" that you hear.



Each time the compressor airflow reverses, it unloads the compressor impeller blades and shaft. When the impeller starts compressing again, it loads the compressor impeller blades and shaft. The turbo will continue this surging as it walks its way down the surge line on its performance map as it decelerates.



This unloading and loading can, over time, produce cyclic fatigue failures in either the impeller blades or shaft - whichever is the weak link in the turbocharger's design.



Please note - at no time does the turbocharger rotor reverse its rotation. There's too much rotational inertia in the system for that to happen. "



Good to hear your results of the new control cone. I won't be installing mine for at least a couple of weeks due to a friendly little injector pump leak



Sean

 

[formula]

Bob,

Yes, the profile of the new control cone is uniform about its circumference.



Sean

 

[jbolt]

Sean- thanks for the clarification on the turbo noise. Who the heck came up with bark? Now the big question is how do you avoid it or get rid of it?





Jeremy- I"m going to leave the DD pin in for my trip up north on Monday to get my transmission work done so I'll get some mileage figures. As far as low boost lag, the smoke screw should help a little but the depth on the profile is nowhere near the stock pin at its max setting. I really like the smoke reduction at idle. The trick is getting the boost up quickly. I'll be curious to see what others think who are running smaller housings or the HX35s.





Bob- pin contours are only limited by the max travel of the guide pin and the length of control cone travel. Has Old Smokey got his pin out yet? I will want to try his when its availble.





Philip-







Jay

 

[formula]

Jay,

I think the term "bark" comes from if the boost is high enough when you chop the throttle then the turbo will make a noise that sounds a bit like a dog bark. When you get your new torque convertor you'll definitely see what I'm talking about. To avoid this condition is simple..... don't chop the throttle quickly, just roll out of it. Another option is to get a new PDR HX35. This will just about eliminate surge altogether The new turbo isn't necessary though, I happened to replace mine because my stock turbo was in rather bad shape.



Sean

 

[Case500D]

After looking at the picture posted some more, I think something along the lines of Bob's idea can easily be done. I know I could threaqd the pin into a plate and chuck the entire addembly up in the lathe. The trick would be to know how far up the pin to cut or polish. I would think you could measure the distance everything travels in the pump with some Persian blue. Just keep track of the actual boost and I bet a distance per pound of boost scale could be developed. You would also have to know where wide open was at and the max boost reached. Say 5 lbs of boost means the metering pin rode up 1/4", then you coould turn the bottom 1/4" of the fuel pin down to the stock size and get the stock feel back up to 5 lbs of boost. Does this make any sense, or am I just nuts? Maybe you better not answer the nuts part Does anyone know if the DD pins are hardened? Just a bit of food for thought.



Jeremy



PS I know I can make the boost gauge move at less than 1300 rpm with my current setup. Should take much to change the pin around a bit.

 

[jbolt]

FYI- I took dimensions of the DD pin and the stock pin. I started CAD drawings of both and will post when done if anyone is interested.



The drawing below shows the min/max guide pin travel of both control cones for comparison.



The stock pin is hardened. I did not check the DD pin.



Jay

 

[jdurham]

That drawing looks almost as good as that last one Philip did...

 

[Philip]

yea right. roflmao

 

[Old Smoky]

jbolt,

I'm not quite ready to release my design. I am continuing to do R&D so I get it just right. I am working with a local machine shop, so it takes time. I expect to have my next design in two weeks. My first design worked well, but I want to make it even better.



Mike

 

[Old Smoky]

How much boost does the DD pin add over the stock pin at the "max" position?



Mike

 

[jbolt]

Mike-



The DD pin does not add any additional boost, Might even be a little less from the stock pin at max. I've only run my stock pin up to 70%.



If you look at the drawings I posted the stock pin at minimum setting has a guide pin throw range from 0. 0"- 0. 130" and a maximum throw range from 0. 054"- 0. 184"



The DD control cone allows a guide pin throw range from 0. 008"- 0. 164"



So the stock pin has the potential to allow more fuel at high boost but it allows more fuel/smoke at low boost.



The DD spring is softer so it has the potential to allow more fuel quicker and at lower boost. I wonder if the DD spring rate was designed around the 21cm or 18. 5cm housing.



How did you measure the maximum travel of the guide pin? Seems to me you would need to know the maximum travel of the reverse lever inside the pump. Did you measure this with the throttle fully depressed? What dimension did you come up with?



Look forward to seeing one of your designs when its done.



Jay

 

[RDBuck]

DD pin

Great posts. Since I've gone to the 12 wastegate I've eliminated smoke at idle and I like the way the truck responds off-idle. What would happen if I used just the softer spring on my stock pin? Would I get more fuel and boost quicker?

 

[Old Smoky]

Jay,

No additional boost? I thought that was the point of the redesigned pin? To measure the travel of the guide pin I did two things. First I tried using calipers that fit into the bore (after a test run without the fuel control plunger). The calipers worked all right, but I wasn't sure how accurate it was. So, I just put some heavy grease on the eccentric of my modified stock pin, took it for a run, and measured the depth at the end of the "whiteness mark" with a depth micrometer. I can’t remember what I came up with; I don't have the papers with me.



What is our goal with this project? I am going for more top-end fueling, with better low-end, but not too much. By this I mean more overall power, but not too much smoke (tunable). What do you guys think?



I apologies to bob if he thinks this should be in the Products/Accessories forum. I am not "soliciting," merely trying to gather information, and learn.



Thanks for the drawings.



Mike

 

[BushWakr - RIP]

Hey Mike,



I appreciate keeping the guidelines in mind, but no worries here... it seems to me this is the initial technical phase and I think it belongs right were it is. .

When your product is ready to go, assuming you maket the design, then it will have to go in products ... .



As for the rest of this thread... ... EXCELLENT !!!

This is a great technical info series and should help all of us in here...



Bob.



ps, I still think Philip's pic was better though ...

 

[boatpuller]

This doesn't sound good, I was hoping that the new pin would add more fuel at the top end without adding smoke on the bottom end. (haven't recieved mine yet)



They said it was good for 50hp over stock, if so how are they getting that without adding more fuel which would raise the boost level?



Maybe I can take a file to the new pin when it gets here to get more fuel at the top end.



Mike,

Sounds like I'll be ordering a new pin from you when you get it figured out.





Caleb