Engine/Transmission (1998.5 - 2002) 98.5 HP question

[czahnle]

Hi Gang,



As you know the 98. 5 came as a 235 HP manual shift or a 215 HP Auto trans. My question is where did they make the extra 20 HP? The reason I ask is I changed my VP44 and now wonder if part of the HP increase was in the pump. In issue 47 on page 44 it lists two CPL numbers for the 49 state manual trans engine. I have been looking in the back issues for reference to the CPL numbers but have not found them yet.



Does someone know where the 20 HP came from? Is there only one VP44 for the 98. 5 engine?



Thanks



Chris

 

[klaybus]

HP Ratings

I always thought the HP diffference was from the auto trans robbing power that the manual transmission didn't... .

Now you got me wondering



Clay

 

[tunod_68]

The computer. I can't remember what it is called specifically. however, it is located behind the starter on the block.

 

[klaybus]

Ecm

Engine Control Module?

 

[tunod_68]

bingo. I believe it was the ECM ... actually saw it on Shade Tree Mechanic several years ago

 

[Lordsman]

I'm with Klaybus, it's the torque converter that uses up additional HP.

 

[Gary - K7GLD]

"I'm with Klaybus, it's the torque converter that uses up additional HP. "



BZZZZZT! WRONG!



Manufacturer HP ratings are given for FLYWHEEL HP - NOT rear wheel HP - so any drivetrain power losses are NOT part of advertised power figures...

 

[FFL8N]

I know the injectors are different. I believe this is where the power comes from. If you check the aftermarket injector sites, you will see a larger increase in hp from the same injecotor in an auto vs a manual because of this reason.

 

[Jetpilot]

The injectors for the manuals and autos are the same... ... .



Doug

 

[czahnle]

Hi Jetpilot,

Is there only one VP44 pump for the 98. 5 ?



Chris, SEL pilot

 

[klaybus]

HP Ratings

My bad... . I stand corrected!

 

[ntillm01]

My 2001 has the same 235 hp rating and it's an automatic. The ECM was programmed specifically to keep the hp and torque down where the transmission would live a longer life in earlier years. Later, the trans guys gave the ok to allow the full 235 hp to the automatics. At the same time, they offered the 305 HO engine for manual transmission only. I don't know if that was an ECM program bump or something else. Memory (as bad as it is) tells me the HO engines got a different VP44 too.

 

[czahnle]

Thank you ntillm, i will rest easier now knowing there is only one VP44 for my 98. 5



Chris

 

[ntillm01]

Thank you ntillm, i will rest easier now knowing there is only one VP44 for my 98. 5



Chris

Ummmm... I don't know that I said exactly that. It is my understanding that the ECM software is the major part of the power differences. It only makes sense that the VP44 would be the same, at least within the same model year. At least they should be very, very similar. There are way better folks out here that know all of the pump/injector combinations on this forum that can correct me if I'm wrong.

 

[Gary - K7GLD]

As *I* understand it, the ONLY reason in later trucks having MORE than a single VP-44 available, is due to different demands created with the HO (high output) version in later M. Y. trucks - dunno exactly when the first HO's hit the market, but assume prior 24 valve trucks all used the same injection pump?

 

[ntillm01]

dont you lose some power from driving the torque converter in the automatic? that would be my guess but i could be wrong

Yes, you do. It's been that way since the beginning of time (or at least automatics). You also use up hp driving the fluid pump that makes the clutches apply too. You don't have that in a manual trans. So for a given engine hp/torque, you will always have less available wheel torque with the automatic than the manual. That's one of the advantages to a manual trans.



But, what is advertised is the flywheel hp/tq (as stated earlier in this thread), as measured without a transmission at all. That's the hp/tq were talking about here.