Yeah i agree, they wouldn't be as good on a sohc, I don't think they have tried it out on a pre ba yet, but still, there would be a considerable gain.

I just found out that Herrods has undertaken development of underdrives for the sixes. That 200rwkw barrier should get alot easier to crack if these go into production.

there has been a bit of talk on under drive pulleys on the sohc six for a while now. Good to see its comming along.

To bad they're going to be Herrod - ie. 300% name surcharge.

If the nizpro intake gives a 25kw increase how does it affect the power over the hole rev range.

Considering the factory intake is a daul runner and promotes best runner lengths for the rev range I would tend to think average power readings over the hole rev range would be less.

As for turbo applications it would be a different senerio.

what factory torque rang does the 99 I6 have ? .....curiousity and how does it differ for u guys with +180

On the Nizpro forum they have two dyno graphs (these are from the engine dyno) displaying the increase the plenum gives on a NA ba 6. The first one shows the power of the car at 254kw with cams, exhaust and edit and the second one with plenum fitted showed that power lifted to 276kw.

Now in answer to your question, i overlayed both dyno graphs to see where the increase took place. From 2300rpm to 4500rpm the plenum gave an extra 5 to 10kw across that range. From 4500rpm upwards the increases are signifcant. An extra 15kw at 5000rpm, 20kw at 6000rpm and 25kw at 6350rpm.
Torque is also up by 20nm between 2500rpm and 3000rpm and in the top half of the rev range there is a whopping 40nm gain from 5800rpm up.
So from what the graph presents (il try to post it up later) power and torque should be up right across the range.

thanks for the input. i take you you as well i would be interested to see what the over lay would be like on completly stock engines, both SOHC and DOHC

so on a ported single ohc engine the gains would have to be pretty decent .
even if it gave atleast 20rwk to a modded engine there'd have to be a few guy's capable of breaking the 200rwk.
so has anyone tried one on a single ohc engine yet ?i'd gladly let my car be the guinypig for them to try it out on.

for half the cost would be interested in me building something similar???
test engines are alway welcome.

if all works out good there would be an alternative for amost half as muck for every one

how much would the plenum cost just buy itself?
the nizpro one

The gains would be good but the thing is how are you going to get the air to it. The plenum was designed to draw in air from behind the headlight and pre BA falcons don't have an opening. Does anyone know if you can get around this?

Also by getting the plenum you might have to get a ba throttle body aswell. It costs 1850 fitted for the plenum.

Tickford_6 it would be good to see the comparison on a stock engine however i dont think it wil have much of an impact. Don't forget the plenum shines mainly over 6000rpm. On that particular motor the revlimit was increased to 6500rpm by using the edit. On a stock pre ba falcon with a limit of 5500rpm i would only think that you would gain between 10 to 12rwkw max.

the plenum, unless it's special on the inside, looks like just a big bit of pipe. Others on here have done custom plenum mods before with good gains.