Plazmaman Plenem Vs Greddy

[2rismo]

Just to confirm , did someone mention you can use the std R33 throttle cable with this plenum ?

Also one for Mercury , I don't suppose its possible to use the GTt runners and PM plenum on an R33 ?

Would there be any gain or just lots of grief for no real purpose .

Lastly , WHAT is the size of the R33 std throttle plate ? PM site shows a 66mm throttlebody as their smallest offering so whats the difference between this and the std R33 25DET throttle plate size ?

Cheers Adrian .

VR Commodore 5L cable

[TiTAN]

not much love for the greddy in here.

[PM-R33]

Stock throttle cable is fine.

[Johnny Johnny]

Lastly , WHAT is the size of the R33 std throttle plate ? PM site shows a 66mm throttlebody as their smallest offering so whats the difference between this and the std R33 25DET throttle plate size ?

Cheers Adrian .

Standard throttle plate is a touch under 63mm.

[Johnny Johnny]

I'm currently looking at a new intake manifold/plenum for my '93 GTS25T, and am probably going down the route of a custom built one. The Plazmaman one is certainly better for my purposes (DD and HPDE - road circuit), as it keeps the longer runners. What's the entry to the runners look like from the inside of the plenum? I've never been able to find a picture of inside the plenum to see if they use flared entries. If someone with a unit off the car and with no TB on it could snap a shot of the internals, I'd appreciate it!

I'm still concerned about 2 design issues of this plenum:

1. Air still needs to make a tight 90* bend into the runners from the plenum. This is going to affect both air speed and turbulence within the plenum.

2. Though offsetting the TB helps, air distribution will not be equal across all runners. Without doing some comprehensive CFD modelling, it looks like air will either focus on runners #3 & 4 (where TB is "aimed") or #6 (common problem for any type of log-style plenum with TB at one end).

The approach I'm possibly taking with mine is to use a dual-chamber design that feeds air into the main plenum equally across the length of the chamber, and parallel to the runner inlets. If anyone is interested, I've started my design/build thread here:

Custom RB25DET intake manifold/plenum

BTW - I'm not a business and this is not a "commercial" response to this thread. Just doing this on my own!

[discopotato03]

Yes an interesting , I take Vizard to be David Vizard and I like his experience (thousands of hours flow bench testing) based ideas on most engine design things .

You may find it interesting to dust off Corky Bells Maximum Boost , it has a chapter on inlet manifold design .

From memory he reckons the radius of entry into the runners should be equal to the diameter of the runner .

Also according to him there should be three times the diameter of the runner clear as in no other runners bell mouth within this "3d" area .

As for the shape of PMs plenum . As soon as I saw it I thought that's along the lines of a Nissan FJ20 plenum only with six runners instead of four .

With the DR30 Skyline type FJ20 inlet manifold the throttlebody also "aims" if you like the airstream along a curved back wall of the plenum rather that straight across the six inlet holes .

I think the fact that you are getting individual pressure drops as each cylinders inlet valves open means the challenge is to be able to feed each one adequately and as equally as possible .

I also reckon that there is something to be gained by using two three cylinder plenums obviously with their own throttlebody , this is common on V6 engines but possibly hard to package on an inline 6 .

The I6 firing (and induction) order 153624 means that as it goes through its 6 cycles their is alternate drawing through each group (front 3/back 3) so maybe something to be gained .

If you look at the Z32 VG30 four cam engine you can see that Nissan went to a bit of trouble to keep the runners reasonably long and the two plenums of reasonable volume .

Yeah I reckon two plenums and two throttlebodies gets you to halfway between what a single vs the RB26s six throttles achieve throttle response and cylinder filling wise .

One thing I have noticed missing on all these plenums is a staged twin throttle plate arrangement where the primary one opens to a point and then the second one , often larger , goes from closed to full open over say the second half of the accelerator pedals travel .

That may be the way to give good low speed (car and engine) driveability and still be able to open a large passage to try to keep up high rev volumetric efficiency .

I guess the hard bit is always going to be getting good breathing characteristics in a non supercharged state and with turbo engines typically lower CR and relatively soft cam profiles . I think the go is to have very low restriction yet with runners long enough to give some ram effect into the cylinders at low revs . The transition to the runners and the runners themselves is probably more important that the plenum volume but it and the throttle/s obviously need to be able to feed as well as possible in a pre boosted state .

Possibly this is why Simon Gisgus (sp ?) of Nispro used to say that the best way was to build the best NA engine possible and turbocharge that .

Corky adds that the turbocharger just goes on to add more air when its spinning fast enough .

Food for thought ?

Cheers A .

[Granthem]

Reppin' Plazmaman

[Johnny Johnny]

Yes an interesting , I take Vizard to be David Vizard and I like his experience (thousands of hours flow bench testing) based ideas on most engine design things .

You may find it interesting to dust off Corky Bells Maximum Boost , it has a chapter on inlet manifold design.

Vizard = David Vizard (Vizard the Wizard :-)

I've got Bell's book as well, in addition to a bunch of others (Smokey Yunick in particular. Might have developed everything on American iron, but the theory still applies).

I also reckon that there is something to be gained by using two three cylinder plenums obviously with their own throttlebody , this is common on V6 engines but possibly hard to package on an inline 6. The I6 firing (and induction) order 153624 means that as it goes through its 6 cycles their is alternate drawing through each group (front 3/back 3) so maybe something to be gained.

The approach I'm thinking of taking is to force the incoming air from the throttle body through a long channel that is almost the entire length of the plenum, so that all parts of the plenum (and therefore runner inlets) get the same volume of air at the same velocity. I think that is key.

One thing I have noticed missing on all these plenums is a staged twin throttle plate arrangement where the primary one opens to a point and then the second one , often larger , goes from closed to full open over say the second half of the accelerator pedals travel. That may be the way to give good low speed (car and engine) driveability and still be able to open a large passage to try to keep up high rev volumetric efficiency.

I like your way of thinking. I might look into how those are designed and see how it might be integrated into the overall design.

[darrinspencer]

Reppin' Plazmaman

How do these go height wise with a rb30 bottom end?

Do they foul the bonnet, plus they run pretty close the strut brace

About to ditch my greddy copy install and use one of these

Rb25 Neo with future rb30 bottom end in mind

[PM-R33]

I have been told by Plazmaman that they can be "made to fit" without hitting the bonnet with a 30 bottom end. What that actually means I do not know as I didn't really ask. However if your serious about it just give them a call and ask what you have to do.

I thought the same thing, that surely it would hit the bonnet on the front.

Edited April 15, 2010 by PM-R33

[MercuryMotorsport]

We made custom lowered engine mounts to get it to fit. Was much better than spacing down the subframe.

[darrinspencer]

We made custom lowered engine mounts to get it to fit. Was much better than spacing down the subframe.

What model car?

My layout is a bit different being a Stagea with r34 gtr front.

How did you go fitting one to a R34 Rb25 NEO?

Throttle body hit the fuse box?

[MercuryMotorsport]

We made the mounts for a R32 GTST with RB25/30. Sat the sump just above the cross member and it just clears the bonnet.

Not sure about the fuse box as we have only had a neo engine in the VC commodore, so everything was custom. If it did hit, we would just move it out the way.

[darrinspencer]

I have spoken with Plazmaman a few times in the last couple of days. Looks like I might get one sent up in a "just tacked together" state for trial fitting, then send it back to get finish with any mods needed.

[D_Stirls]

Vizard = David Vizard (Vizard the Wizard :-)

I've got Bell's book as well, in addition to a bunch of others (Smokey Yunick in particular. Might have developed everything on American iron, but the theory still applies).

The approach I'm thinking of taking is to force the incoming air from the throttle body through a long channel that is almost the entire length of the plenum, so that all parts of the plenum (and therefore runner inlets) get the same volume of air at the same velocity. I think that is key.

I like your way of thinking. I might look into how those are designed and see how it might be integrated into the overall design.

are you talking about something along the lines of this?

[Johnny Johnny]

are you talking about something along the lines of this?

Yes, with a long slot in between the first and second plenums (and longer runners).

Here's a closer design:

In this design, the vertical slats help to smooth and direct the flow of air.

[Roy]

(trust me, I turned my back on a lucrative Engineering career to follow my passion of jap perf cars).

Lucrative...damn i wish i knew where to find one

Any experience of the Plazmaman inlet manifolds on RB20s? I am running a 6boost manifold with TD06-20G (with 8cm housing) making 260rwkws at 19psi. How best would you describe the change in engine performance characteristics? Mine is sitting in the boot of the car and this thread has just about convinced me to get it installed. Also very interested to hear your thoughts on whether its worthwhil ebumping up the throttle body size when you go aftermarket plenum.

I am just in the process of changing from the std Greddy exhaust manifold to the 6boost. I am hoping the combination of the 6boost manifold and plenum may be enough to allow me bump up the exhaust housing size to 10cm. At the moment the engine simply stops making power at 20psi, so seems the little 8cm is choking its top end...lol its all a big trade off with only 2l

But ideally it would be nice to be able to run 22psi and make 280-290rwkws, and hopefully not lose too much in the spool with the bigger housing.

[Roy]

In this design, the vertical slats help to smooth and direct the flow of air.

Just a question, do you really want to be smoothing the airflow? You want turbulent flow so that when its on its way down the runners its still bouncing around in an excited state and when the injectors squirt away you are getting good mixing. Its all rpm dependant...but...as a rule

[jarrod83]

The plazmaman is a very well designed plenum for midrange power, i have one on my forged 25/30 with a gt35r 0.82 turbo and i actually make more power than my standard rb25 with its standard turbo across the entire revv range, the only point it even gets slightly close is at 2700RPM, before and especially after that it just gets blown away and manages full boost very close to 3500 rpm... There is definitely a lot of pros for the plenum, my only problem with it is that its extremely hard to work around the intake side of the engine bay when changing anything like the oil filter.. it takes up alot of space.. but id definately still pick it over a greddy plenum

also the standard throttle body narrows down very close to 60mm, the plazmamans nice shiny tb is 72mm which is roughly 44% bigger.. has anyone managed to fit in a strut brace over a 25/30 in a r33 engine bay without having to lower the cross member? (i know it would depend on the brace)

[2rismo]

Just a question, do you really want to be smoothing the airflow? You want turbulent flow so that when its on its way down the runners its still bouncing around in an excited state and when the injectors squirt away you are getting good mixing. Its all rpm dependant...but...as a rule

I doubt you'd be able to do so to a point where air in the intake is anything but turbulent, mate.