Greddy/Trust Plenum

[Steve]

Originally posted by Sydneykid

Hi HJimx, if you can see a colouration difference in the spark plugs then there is alway more than 0.5 A/F ratio difference (oil usage not withstanding).  By moving an RB25DET from 11.5 to 1 to 12 to 1 A/F ratio you pick up 25 to 30 rwkw.  So if you have 1 cylinder at 12 to 1 and 5 at 11.5 to 1, then you are loosing 20 to 25 rwkw.  Remembering that  this is the minimum, a noticeable colouration difference could easily be 1.0 A/F ratio which is closer to 40 rwkw.

Now I have worked on over 20 X RB20/25's and have never seen one that shows any consistent spark plug colouration differences on 3 and 4.  I have seen it on differing cylinders but this is usually traced to lower flowing injectors or other factors.  It certainly is not airflow related with any consistency........

Well we agree on something:) I think the missunderstanding was that this post gave me the impression that you were saying that JimX's plenum was robbing him of between 20-40rwkw.

I dont understand how though ben ellis putting down 290rwkw with stock plenum (and head gasket;)) is relevant, as it has been demonstrated on many occasions that power well in excess of this is possible with the stock plenum. My point was directed at what I perceived to be a criticism of the efficiency of a front facing plenum when it obviously is no less efficient than the stocker.

[BU5TER]

Honestly if the power gain is minimal from a greddy plenum and people stiill want to buy them whats the problem

imo they look great and the time saved in changing spark plugs alone makes them worth it as you don't have that stupid cross over pipe in the road

[BU5TER]

Oh and I'm making well over 300rwkw using one so they can't be that bad

[Sydneykid]

Hi Steve, Ben has changed the head gasket, comp is down to 8.6 to 1. Truely I have seen 10+ GTST's with more than 260 rwkw that have standard inlet systems. I have seen one with 320 rwkw that had a totally standard inlet, so Ben's 290 is not outrageous.

There are more important things to be done first in the pursuit of power, when you have done those, then buy a plenum. But be careful with the airflow distribution.

Crikey Buster how often are you changing your plugs? I find the coils much more of a pain than the inlet pipe. With the 120 degree bend at the throttle body, I only have to remove one clamp, it takes less than 30 seconds, coils aaaaaahhhhhh.....

Were you live 300 rwkw is a breeze, we had the mobile Dynomax there a few weeks ago. The old RB20 made 245 rwkw, that's what minus 3 degrees ambient temperature will do for you. There is always more horsepower in a freezer....... only kidding.

[BU5TER]

Not to often but each time I do they're a joy to get at hahahaha and If we're talking power figures up here I should of said closer to 400rwkw then as the power figure quoted was done in Sydney

[Sydneykid]

So have you done a back to back test of the Greddy with the standard inlet?

[BU5TER]

No sorry, the plenum was on the car when I purchased it

[rb20-calais]

I just bought a plenum from NZ for $450 second hand, their is only 5 of them in the world and they are a very cool looking design. There is no way I would of payed $600+ for it, $450 was about the most I would pay. This identical plenum is on an rb20 (the guy who made the plenums) and it makes over 400bhp @ 12psi (forged internals, etc).

What am I trying to say? I think they are worthwhile for throttle response and to make it easier for me to do my piping but I agree with Sydneykid that $1200 is too much for a plenum unless you have BIG power.

Also there is a guy on www.ozperformance.net forums called jdcustom who fabricated rb20/25 plenums that have tuned runners and retain all stock things for $550 and they look the goods. Maybe they are worth a look as people using similar plenums he makes on rb30et's are getting good power from them.

Babble over and out.

Evan