To QSB or NOT??

StuckinMud

StuckinMud

Absolutely Clueless....
Joined
May 10, 2006
Messages
204
OK .. First I have smoked the search button.. here and else where.
It seems there has not been a definitive consensus on use of the QSB piston in the cummins 5.9.

Some builders have said that it ultimately yields less power than the emissions & melt prone later 04.5 up design. Others like the QSB for its better thermal attributes.

So power wise why would or would not the QSB piston be the way to go?..Technically !! Assume we are using the properly degreed 7 hole QSB nozzle.

I have not been able to find a real explanation as to why or why not the re-entrant design piston is better or not. Flame propagation?

Lets weigh it out before I drop the coin..
Thanks!
 
The truck will be a summertime dd with severe tire wear issues. Mostly for fun.. occasional towing about 10k lbs.
Will see the drag strip occasionally but many more stop lights. It will play at the sand dunes. Never know maybe even a hook or two. It will NOT live an easy life but will be maintained exceptionally..not beat cold, never over 5k on oil, 2 micron fuel filter blah blah blah.
Besides diesels are not meant to putz around they need to be worked...any amens or hell yea's there??? LOL
Would love 700-900.. I know large range but with me enough is never enough. Hell one day 1k could be nice in a pissing contest..er I mean at a dyno day but may never happen..but know that it will never see nitrous.

It is in a Ford. With the 48re..heavily upgraded. Truck is also getting a frame up..body work paint etc. Likely wont see the road until late next year..well see. but for now I'm addressing the motor fail.

The motor had 85k, just spun a bearing..Crank is done. everything else beautiful.
It was running QSB 480 injectors, studded , 63/68/14 -T4 stainless manifold. 05 Motor so stuck with Smarty but its a transplant so I may may just re-pin and do a newer ECM and EFI Live.
12v Brazil rods on the way.(scratch that..just arrived while typing this!).working on a 12v crank at the moment. Will do arp rod bolts and balance the rotating assembly.I will likely go with a 188/220 for spool and just because I HATE egr (even though its just in cylinder). When it was a 6.0 that only lasted 530 miles from the dealers lot! Valve springs, push rods. The head will get shaved and ports cleaned up just because I hate uneven distribution of airflow. Its all about efficiency and that's what makes a happy motor. It will likely get an s480 stuffed under the 363. Injectors opened up some. Then the little things like threaded freeze plugs 6.7 rail and lines.
Basically I am looking to stuff as many squirrels into the wheel cage as I possibly can with out them all getting pissed off about it.

So as for the pistons- I'm not going forged rods or mono-therms etc. I think this can be built to live at 800 safely all day long. As far as the pistons go I like the double heat treating of the QSB. I like how they will match my motorsport (QSB) injectors. But if its a large trade off in power I'll stick with the 04.5 design.

So what it comes down to for me to decide is some form of empirical data that would support my decision. I am not looking for "the stock pistons will handle that just fine." At this juncture I am looking for the better of the two based on design function. From what I see its an issue of flame propagation between the designs and with what nozzle angles ( I will switch if needed) is best.

In addition I thought since not having found clear answers from searching that a new post would be a good place to entertain the details of the designs and why which one really is the better choice for certain applications, after all everything has its pro's and con's. Lets look at them.
 
To put it simple and quick...

Qsb, 03-04, and 6.7 are all similar and the reentrant bowl. Most common style cummins used for the b series. Considered more reliable, heavier duty in the cr's. Used in all types of builds, including 1000+ hp.

04-07 style is non reentrant, claimed to make more hp vs reentrant in our engines. Design is not as resistant to injector malfunction or failure. Not a bad design, just not as resilient comparatively.

Most people switch over to 03-04 or qsb in an effort to make the engine less prone to cr injector malfunction. In lower hp levels, the power difference is likely negligible. The qsb has additional treating to increase resilience as compared to 03-04 standard piston.
 
TheBigNasty said:
To put it simple and quick...



04-07 style is non reentrant, claimed to make more hp vs reentrant in our engines.

.
Click to expand...

This is where I am trying to go. Has anyone actually dyno'd the difference in the pistons. Usually by the time they go that far into the motor there are other major changes that occur impacting the difference in power levels.
Also what is the margin of the power level between the two?

So if I am shooting for a reliable (I know that word really doesn't apply) 800ish am I better off overcoming that power margin for the extra resistance of failure of the QSB or am I better to try and make that power more easily using the 04.5 up piston?
The goal here is to make the power without it being the potential limit..or in other terms without breaking a sweat or doing it on the ragged edge. Hence the route of trying to be efficient about doing it.
There is a point where its to much to be fun on the street but in a heavier Ford that limit is higher than the dodges. That threshold is where I would like it to be.
 
JSP dyno'd both piston styles in monotherm form. Was not completely apples to apples as there was a slight compression difference between the piston styles. Iirc the difference in power was more likely from the compression ratio difference as it was from the bowl shape difference. This was at 1000hp on fuel.
 
TheBigNasty said:
To put it simple and quick...

Qsb, 03-04, and 6.7 are all similar and the reentrant bowl. Most common style cummins used for the b series. Considered more reliable, heavier duty in the cr's. Used in all types of builds, including 1000+ hp.

04-07 style is non reentrant, claimed to make more hp vs reentrant in our engines. Design is not as resistant to injector malfunction or failure. Not a bad design, just not as resilient comparatively.

Most people switch over to 03-04 or qsb in an effort to make the engine less prone to cr injector malfunction. In lower hp levels, the power difference is likely negligible. The qsb has additional treating to increase resilience as compared to 03-04 standard piston.
Click to expand...


^^^^All good points and spot on info. One more benefit to add the 03-04 IMO burns cleaner on the street versus the 04.5-07. Big plus in my book.

OP. For 800+ hp I would run the 03-04 QSB for what you are wanting to do while burning cleaner on the street. Excellent choice in chargers for street compounds.

Ashley Black stated in a thread awhile back that he has seen around a 100hp difference favoring the 04.5-07 piston with same fueling and air. Difference though he was racing at that time at over 1K+hp not daily driving, weekend warrior and towing 10k loads.

The QSB has no problem going over 1K hp when you decide to push it. I believe it's a great overall choice. $.02

Chris
 
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