DB/DS Fuel Rate Discussion
Quote:
For future reference, at what boost levels should the Arp studs be used?
There is no useful upper boost level for a 6.2/6.5 where studs become a better alternative than new TTY bolts - assuming you install the heads correctly using the gaskets, sealants and procedures recommended by The Diesel Page.
We know that the Stanadyne DB/DS series of rotary fuel injection pumps are limited in fuel delivery due to the volumetric design of the internal pumping plungers. There are finite limits to the amount of fuel the DB2 fuel injection pump can deliver.
As a way of explaining why this is important, we know that the first gen LB7 Duramax, with its high-pressure common rail fuel injection system, was factory rated at 300 HP/3100 RPM with the 91.7 mm2 (per 1000 strokes) fuel delivery and 18-psi boost pressure. Here's a photo of the emissions ID plate from the LB7 Duramax that is installed in my Lil Red truck. In it, you can see the fuel rate and other data points.
https://www.thedieselpageforums.com/...8&d=1604362898
Even the highest fuel-rate marine 6.2/6.5 DB2 isn't able to deliver that amount of fuel at higher engine rpms where maximum horsepower is typically produced (HP = (Torque × RPM)/5252). In fact, most DB mechanical and DS electronic fuel injection pumps have a fuel rate curve that peaks in the low 2000s (somewhere in the 70 mm2 range), meaning that as engine speed increases beyond that point, fuel delivery decreases. So... 15-psi boost pressure is about all that is necessary for even a performance 6.5L TurboDiesel. I used TTY head bolts on just such an engine for nearly 300,000 miles. https://www.thedieselpage.com/finale.htm
Now... if you're planning to add propane (a fuel) and nitrous, then perhaps studs might become relevant at some point. I once witnessed a dyno run at a diesel event I covered where a 6.5 was using maxed-out DS electronic programming, along with propane, nitrous and water/methanol injection. I stood way-way back... Not sure what the owner was trying to prove with that one.
And, John Kennedy used his own programming and other mods in an LB7 Duramax (and its original TTY head bolts) to produce in excess of 700 horsepower.
