Moving peak power DOWN the rev range- How to?

[Davey]

I think my car makes it's power too far up the rev range (made 294bhp@6590rpm, before it cut out (due to a dodgy speedo), and the power was still climbing).
This seems like a waste of power to me, if the power curve kept going, it looks like peak power would have been made at over 7000rpm, and i dont personaly like to drive my 12 year old datsun that hard
Also, the torque figure isnt exactly impressive, would have hoped for more like 280 or so, as it is, it made 238@ 5300rpm

Anyone got any idea's as to why, or what i could do to get better power and torque :?:

Spec is- AVCR, running (on the day) approx1-1.05 bar,
Greddy front mount, standard(i presume) fuel pump, iridium plugs, k+N, 70mm straight through exhaust (although not as straight as a mongoose)
Standard (i presume) tubby

http://groups.msn.com/skylinefever/daveyspics.msnw?action=ShowPhoto&PhotoID=859 (bigger picture)

Forgot to say, the figures are from powerstation

 

[skiddusmarkus]

You aren't going to get peak power to move down the revrange beacuase it climbs as the revs rise and is fairly linear.At 6000rpm you'll have roughly twice the power as at 3000rpm.
You can bring the torque further down the revrange by running more boost at lower revs with a boost controller.This is the easiest way,there are others but involve new engine parts and £lots.

 

[AJ4]

Low torque is usually a sign of breathing problems, the inlet air speed is too low because it is restricted in some way. Make sure your airfilter is clean etc.

You can do two main things to improve low end torque ( as well as what skiddus suggested ) but they are not two-minute jobs. The first is to choke down the inlets, ie make the inlet diameter smaller. This makes the inlet air speed higher at low revs and will lift the torque up because the cylinders fill better. Unfortunately it usually kills top end power

The other method is to have an exhaust manifold with longer primaries, which with our setup is practically impossible becasue of the tubbie etc.

Basically the engine is tuned like a filter, it will always peak at one point and all you can do is move the point up and down at different rpms. Remember though that whatever you do before the peak will usually have an effect after the peak, ie it 'rocks' around the maximum. Lift the low end and lose the high end etc.

Sorry, that was absolutely no help whatsoever

 

[turblio]

Cams, nuff said

 

[memski]

I think you really want more torque rather than power down the rev range. The power seems fairly normal but you really need more torque to make the car more driveable.

Some datsuns seem to make good torque, others don't; the state of the engine and turbo would be one area to check over, also might be an idea to check fuel pressure (uprated fuel pump may be an idea).

 

[Davey]

You can bring the torque further down the revrange by running more boost at lower revs with a boost controller

I've since raised the boost to 1.1 upto about 5000/5500, cant remember which, do you reckon i could run more, say 1.2, in the mid range, safely(ish), with stock fuelling :?:
Would the k+N have a detrimental affect on low down torque, i have heard people say that the stock airbox is better for drivability.
How come some people (ie memski) get about 290bhp/280 lb/ft ba****ds!

Cams, nuff said

LOL, care to elaborate m8, thought cams always moved the power up the revs :?: :?

 

[memski]

How come some people (ie memski) get about 290bhp/280 lb/ft bastards!

LOL sorry mate, I don't know either my engine seems to have a high compression figure when I test it so I guess that may have some effect. If it's any consolation, launch control killed my turbo..... ...but I've since replaced it with a bigger one and have shit loads more midrange :lol: Oops sorry trying to help, I've found my apexi filter to be better than the stock airbox - almost as good as a decat straight through exhaust system, expecially when rerouted behind the headlight (starts getting progressively more expensive for less gain here).

 

[Odin]

.

How come some people (ie memski) get about 290bhp/280 lb/ft bastards!

Mine got 311bhp and 304lb's at 1.2 bar on standard turbo :lol:


rob

 

[Nad]

Need to get more air in = bigger bang so get a higher lift cam for more torque.

Nad

 

[J-GTi-R]

My car was doing the same, had a similar power curve and lack of torque (but still made 2 bhp more than you, lol :lol: :lol: ). To improve the torque on mine, my next plan was to fit a Unichip to sort out the fuel map once and for all. I've talked to a few people who run 1-1.1 bar who've then put on a Unichip/Apexi PFC and made huge torque gains from a decent map. V's car is a good exapmle of what a decent map can do, as his Motec is doing wonders for his torque (without it, he'd probably be getting 250 lb/ft).

 

[memski]

A decent map will make the world of difference but the torque figure of 286lbs-ft I got accompanied a 288bhp figure running off the standard ecu slightly richened up via safc at 1bar with just WI and an uprated fuel pump (Interpro rolling road day mag feature ).

 

[Davey]

A decent map will make the world of difference but the torque figure of 286lbs-ft I got accompanied a 288bhp figure running off the standard ecu slightly richened up via safc at 1bar with just WI and an uprated fuel pump (Interpro rolling road day mag feature ).

Thats what i'm talking about, it's all very well getting loads of torque running an aftermarket ecu/more boost, but some cars seem to get good figures without those :?

And J, you only beat me cos my car cut out

So, what about the cam's then, just about every post ive read before says that you get more power, but at the cost of reduced "drivability"
I'm not going to buy a new tubby (unless mine goes bang), but why does a bigger tubby= more torque, even if you run the same boost?,

 

[skiddusmarkus]

Less backpressure from the bigger exhaust turbine and lower inlet temps.

 

[turblio]

Okay cams,
without going in depth and over technical you can advance and retard cams
to move the torque of an engine however moving the torque lower down
the rev range wil also lose some off the top of the range (unless you had variable valve timing nice ) it also follows that you can select various
durations but on the R mild ones seem to work best, my sons R has HKS
cams, and these really suit his level of tune so much that I am going to have the same ones fitted to mine...
Frank