peak hp question

[rudefyet]

as i strive to learn everything i need to know to make the perfect engine...i just realize i'm missing something

 

as for increasing the rpms at which peak hp is reached...what kinds of mods can make you reach peak hp at higher rpms

 

also...my biggest question is there like a reasonable increase in rpms that can be acheived...say 4800 to 5500...likean ideal peak hp rpm that can be done with most engines...or is it more like the skys the limit...

 

hopefully someone understands what i'm getting at here

 

EDIT: just thought up an example...say i have a SI 3800

 

3.8 bore x 3.4 stroke...peak hp at 4800....now would ebing about to increase the rpms at which peak hp is reach by 700rpms be a resonable task...if not what kind of increase is reasonable percentage or rpm wise...also how can that goal be achived (what needs to be done)...last how will that affect the rpms at which peak tq is reached?

[BIGBULS]

Well, an "ideal" peak rpm for power would really depend on the car's redline and where your tranny (if it's an auto) shifts at.

 

For instance, the newest round of Jaguars with the 4.2L DOHC V8 (SC) and the 6 speed auto look great on paper.............except the engine makes peak power at 6100rpm (reline is 6200), but the tranny shifts at 5750rpm for 1-2 and 5900-6K thereafter.............so you actually can NOT acess all of it's power.

 

Gay huh?

 

 

 

For you, I'd think that the 4800rpm power peak is pretty decent, especially if your tranny is shifting at, or just shy of the 5500rpm redline.

 

 

The other consideration with peak power (aside from matching your power curve to your gearing and PCM), is if you want a top speed car. For instance, my old SE-R would pull to just over 130mph, sitting at @6500rpm indicated (~6350rpm actual)............RIGHT on it's power peak.........thus using ALL available power. GM FWD autos though, tend to be geared so long that they actually reach top speed in 3rd gear (when ungoverned)......normally PAST peak power.........but they are SO far from the power peak in 4th, that an upshift would do no good........

 

Make sense?

 

 

 

 

As for moving the power peak around, a cam is really the only way to effectively do this, and AFAIK there are no Series I cams out there. But you can do some things to help it out.............a UDP for instance will generally shift the powerband upwards slightly, where exhausts often help more in the midrange.........

 

Either way, without good powertrain management (in other words, shiftpoints), these gains aren't going to be as helpful.