Mild 6.9 buildup(planning phase) comments?

[Diesel JD]

So we've had a lot of talk here about an extreme IDI build....what I've been rolling around in my head probably isn't going to happen in the next few months unless I'm forced into it but I'd like to throw out the mod list for the collective and see what everyone thinks. Here's what I'm suggesting and my HP goals would be to be equal or better than a bone stock 94-97 PSD.
1) Custom pistons with around an 18 or 18.5:1 CR to make room for
2) A better turbo that can push 20-25 psiG without being out of its efficiency range...don't know what turbo that is yet
3) head and intake studs, exhaust manifold studs too if need be
4) Port and Polish heads just like icanfixall
5) a hot DB2 or DB2/4 hybrid
6) Moose injectors
7) Whole rotating assembly balanced as best as possible

I would be proud of that thing and happy with whatever it did on the dyno I think. Now I know the custom pistons would be expensive but I can live with that. I want to be able to bolt them to 7.3 IDIT rods but with the 6.9 thicker cylinder walls. They don't make these I don't think. I know there are concerns about cold starting but if I were to have these pistons created would I have to worry about them coming too fr above the deck or not far enough...other stuff like that? Of course I'd be getting a Typ4 cam and maybe upgrading the valve springs. Any thoughts or criticisms?

 

[dyoung14]

my 6.9 when i had it putting the most out would out pull my stepdads powerstroke with the straightpipe and shimmed FPR, and mine is N/A his powerstroke when its running right will pull the mountian at 60 MPH with 4.10 gears and zf5, my IDI if i crank the timing and max the fuel back out i can pull it at 70 MPH with my 3.55 gears and t-19, so please aim a little higher on your horserpower numbers, its not hard to beat the powerstrokes whimpy 215 hp stock, if your IDI dont run with one and you got a turbo then you have something wrong

 

[Rot Box]

Sounds like a fun build When I was hell bent on building a low compression 6.5 I found that Heath (http://www.heathdiesel.com/) recommends not going that route as the DS-4 and DB-2 loose their efficiency in doing so. I'm far from an expert and I know they are not the same motor but its something I would look into.

 

[FordGuy100]

my 6.9 when i had it putting the most out would out pull my stepdads powerstroke with the straightpipe and shimmed FPR, and mine is N/A his powerstroke when its running right will pull the mountian at 60 MPH with 4.10 gears and zf5, my IDI if i crank the timing and max the fuel back out i can pull it at 70 MPH with my 3.55 gears and t-19, so please aim a little higher on your horserpower numbers, its not hard to beat the powerstrokes whimpy 215 hp stock, if your IDI dont run with one and you got a turbo then you have something wrong

Yeah but my every ody wants to run way advanced timig plus fuel. That us a recipe for disaster I would think.

What made the early 6.9's have lower compression?

 

[Diesel JD]

I don't like the idea of advancing the timing much beyond my current fairly aggressive settings. I have mine close to 0* with the luminosity method which is probably about 9.5-10.5 with the pulse method. That is plenty much timing as far as I can tell. I wonder why the DB2/DB4 combo would lose efficiency? I would want the DB4 as much for the higher injection pressure as for the added power potential. Certainly it's not too much for our nozzles based on the pressures posted on abull's thread. They can handle 6700 psi right, even though they typically only see 2000. Moose misters could really take adavantage of higher injection pressures(I'm guessing) and more pressure should mean better atomization and better fuel efficiency. I don't care for the DS4 pump, it just doesn't seem all that great and I don't care for the electric add-ons. As far as what made the A model 6.9s lower compression I'm not really sure what it was. I thought it was the heads that were different. Pretty sure it was changed for emissions reasons.

 

[typ4]

Trading higher boost for lower compression is not a good plan IMO.
There are several ways to build a turbo engine,
low comp- high boost
mid comp- mid boost
high comp- low boost. this makes the best low end torque.

More to follow. Wife is taking me to the beach for dinner.

 

[icanfixall]

Balancing everything will even out the power strokes made by each cylinder. Decking the block will cause all the pistons to be the same amount up out of the cylinders. CC'ing the precup chambers in the heads will add to the even power strokes created. Trueing up the main webs will cut down on the misalignment that causes internal drag on the crank bearings. Having all the cylinders align honed square with the crank will cut down some of the piston and ring drag... All this trueing up the rotating parts of the motor cut down on drag which increases horse power to the wheels.... In the old days this was called blueprinting. It is still a word used in some shops but very few... Most garage builders with just install parts and expect hp gains without doing anything else...