DD 8V71T specs. What components went into turning 435 hp to 462 hp in later years?

[Shearerlegal]

I have 8v71TI's spec'd at 435 HP. I found a later model DD brochure for the same engines (7082-3300, 7082-7300) spec'd out at 462 HP. Does anyone know what components Detroit changed to make the extra horsepower in the later version 8v71TI? Both early and late versions list the same N90 injectors. Thanks in advance.

Scott

[jim rosenthal]

Interesting question, because you would think that they would put larger injectors in, to get more hp. Maybe they raised the compression or turned up the boost? It's difficult to understand how you could make more power without adding more fuel consumption.

[Avenger]

More RPM?

[Photolomy]

I was wondering where the 430HP spec comes from. Is that at 2500 RPM?

[oscarvan]

More RPM?

Yep.

Only way to get more fuel out of the same injector is more injections per/time.....

Probably (and I'm guessing) needs more cooling and lubrication.

[Avenger]

Uh, no.

The injector only pumps just so much per firing cycle. More cycles doesn't change how much fuel the piston sees.

I was referring to horsepower being a function of RPM and that the same engine can make more horsepower simply by increasing it's rated RPM.

[Captain Ralph]

The next HP step for my 675/650HP 12V71TIs is injectors and turbos. Then 750/720HP.

HP takes air and fuel, the only way to gain this from the Penski play book is turbo and injectors. The real big HP leap requires cooler air; TI to TA then both.

There were some piston changes to lower the starting compression ratio from the natural to turbo versions. Also changing the blower speed ratio. Other than these, the Penski block is all the same.

More HP equals lower engine life, but I doubt that many of us really pull much of the available HP out of our engines anyway.

For the 12V71T, there are 6 Penski HP tunes; 675/650, 750/720, 800/775, 850/825, 870/840 and 900/870HP.

Before the questions start coming in, the first number 675 is the flywheel HP, the second number 650 is Shaft HP. Most factory package ratings were shaft HP. The sales folk like the bigger numbers so they sell my engine as a 675HP model.

In the OP, you may be taking about the same engine/tune, just different HP ratings before and after the clutch & gear.

[oscarvan]

Uh, no.

The injector only pumps just so much per firing cycle. More cycles doesn't change how much fuel the piston sees.

I was referring to horsepower being a function of RPM and that the same engine can make more horsepower simply by increasing it's rated RPM.

That's what I was saying. We are agreeing.

[Captain Ralph]

Uh, no.

The injector only pumps just so much per firing cycle. More cycles doesn't change how much fuel the piston sees.

I was referring to horsepower being a function of RPM and that the same engine can make more horsepower simply by increasing it's rated RPM.

Only to a point,, rite before it blows up.

[madhatter1]

A great example of this is Cummins 6BT's. I have 260HP @2600. They go up to 315 @2800. Then 355 @ 3000. But all make similar torque across the range. Yes mine are slightly low torque but I can swing bigger props that the higher RPM engines. So great cruise speed. The 315 in a 36 gives about the same numbers as my 34 gets with only a slightly higher fuel burn. Only so much realistic HP capacity for a given displacement. Cubic HP is important in boats traveling uphill everywhere they go.