Do not worry about messing something up.

The best learned lessons usually involve something being broken.
The cost to repair the broken device dictates how long you remember the lesson.

The more expensive the lesson, the better you learn it and the longer you remember it.

 

I have been down this road this road and some agree with me and others do not.....

To have an engine built like Dave's is going to cost you more than the $4,500.00 he spent but let's just say you can.
Add a Turbo another $2,000.00
Pyro, exhaust, belts, hoses and other goodies will eat the other $500.00

$7,000.00 and you have a very nice engine....I priced it out [to have one built] it was closer to $9,000.00

The diesel shops I talked to wondered why I wanted the 6.9 instead of a sleeved 7.3....I explained Dave's expereince with sleeved 7.3's and the looked at me and said well it's your money. The conversation then continued to Cummins vs 6.9/7.3 IDI and how much supperior the Cummins is....and for the money I'd be better off putting in a Cummins!

Now everyones situation is different....if you can rebuild an engine, well Dave's IDI may be the way to go as for myself, I can not rebuild an engine so for the money and reliability, I'm going with the Cummins.

 

Actually there is a new turbo in the 4500 dollar figure, but it did not include any of the plumbing so the price was under 2000 dollars.

 

Hey Dave, I was just wondering, why is it manditory to drop compression in order to run higher boost pressure? Is it possible to run high CR and boost?

 

Consider a Power Stroke with 18 to 1 compression ratio running 30 PSI boost.
Effective compression ratio after boost is 54.7 to 1.

Now we take a 6.9 with 22.5 to 1 compression.
21 pounds of boost is 54 .6 to 1 compression ratio.

7.3 IDI 21.5 to 1
Add 22.5 pounds of boost for a ratio of 54.4 to 1.

The Power Stroke was designed to be turbocharged from day one.
The IDI was retrofited with a turbo after it was designed as a NA motor.

Dropping the compression ratio helps keep the cylinder pressures under control while allowing more boost pressure which in turn means more air in the cylinder.
It also eases the pressure on the head gasket and head bolts from extreme cylinder pressures.

By dropping my compression to 20.25 to 1 and using head studs I am able to run 25 PSI boost and am only slightly above a Power Stroke final compression ratio.
It will go higher than that though with no adverse effects.

Well maybe it did have some small effects when I blew the intake gaskets out of it as well as the exhaust manifold gaskets, but he head gaskets were fine.

All I can say is "Them damn Dodges do try to put up a fight sometimes".
I will be the first to admit I can't out pull all of them running around here, but I can drop their jaws with my old Ford.
They never expect it to bite back when they bite into it.

Funny thing is, it only takes a little black smoke to make them want to bite and old 86 Ford that should be a NA diesel.
If I had a camera ready I could post some priceless pictures of their faces as it goes the other way for them.

 

Ok, so the final CR should be around 55:1, but what I don't understand is why an engine can't be run at a higher final CR. I guess better head gaskets would be needed, but are there any stuctural or phisical reasons that would make higher final CR possible?

 

55 to 1 is twice the final compression ratio the engine was designed to run.
Head bolts can not clamp the head gasket tight enough to keep it in place.
Head studs do have better clamping force, but they have limits.

You can exceed 55 to 1 for a final compression ratio, but it will not be reliable and you may have to walk home.

You can fork out more cash and go to O ringed heads which will let you increase the boost again, but then you will also be talking the cost of the O rings and a second turbo to make boost numbers that big along with even bigger IP fuel settings and an intercooler.

The potential is there, you are only limited by your wallet thickness.

 

Gotchya, so the block, heads and pistons aren't the real problem, its what holds them all together. I guess the only reason we dont have engines that already have O ringed heads is the machining cost. Neat idea though.