Greddy/Trust Plenum

[Yakuza]

Where can I buy them ?

How much are they ?

thanks !

[dan_the_man]

http://www.takakaira.co.jp/asp/template.as...PQqMnNnikJlhoKj

[Steve]

www.greenline.jp or http://www.nengun.siteblast.com/gallery.as...ge=7&shopperid=

Depends on the yen, but expect around $1100 ish

[Jimbo2000]

what sort of gains would you find?

[Jimbo2000]

or is it more a responsiveness mod (sp)

[GTS-t VSPEC]

Jimbo, Alot of gaind in my book. The response, the mid-range power, and even the top end doesn't drop off as early:D

[Ronin 09]

waiting for one from greenline oh the pain of waiting...

GTS-t VSPEC, do you know the bolt pattern for the throttle? My mechanic works at Honda and we're trying to figure out of a Honda Legend 90mm throttle will fit without an adapter plate

[benm]

Im still not quite sure what these things do...

Will they have any benefits over the stock plenum if you only have a stock ecu and stock turbo ?

[Steve]

Main benefit is from a flow point (less bends than stock) and you are shortening the pipework if you have a FMIC.

Stock cooler, forget it.

If you are going for big hp, further flow advantages with a larger throttle body.

Stock ecu, spend the money on upgrading that first.

[T0nyGTSt]

You lose a metric meter of cooler piping.

On a GT-R, I dunno.

But on a GTS there must be some physical and 'in the pants' difference since you lose so much piping.

T.

[GTS-t VSPEC]

Ronin, Sorry don't know the bolt pattern, but and adapter plate is easy made.

[Sydneykid]

Hi guys, as I have said before, I believe spending money on an aftermarket plenum is a waste, you will get a better result spending your hard earned on other things. I would never even consider changing from the standard plenum until I have a power target that requires upgrading the internals of the engine.

I have seen two RB25DET's during last month make 280 and 290 rwkw with the standard plenum and throttle body. That's just about the accepted limit (around 450 bhp) of the standard RB25DET internals. These two are not in any way unique.

I have never seen any evidence that any aftermarket plenum will improve on the power output or response of internally standard RB's. On the other hand I have seen plenty of evidence of many aftermarket plenums that actually cost power. I have also seen plenty that upset the airflow so badly that the mixtures are all over the place and individual cylinder detonation is prevalent. This is an engine tuners worst nightmare.

That's my 20 cents worth.

[Steve]

Sydneykid, have you ever driven a before/after with a trust plenum. Car pushing 200-250rwks? Just out of interest?

I just dont see how losing all that pipework could hurt. As for power with stock plenum and throttle body, there are guys running sub 10sec 1/4s with RB30 engines with RB30 heads, doesnt mean they wouldnt benefit from an RB25 head, so the point is sort of mute. There are guys running well over 300rwkw with stock plenum and tb, boost will overcome alot, doesnt mean it wouldnt be better to do it another way.

[Sydneykid]

Hi Steve, I haven't had a car with a standard plenum on it then ONLY added a Trust plenum. There is always other stuff going on at the same time. I have however taken a Trust plenum off a car and replaced it with a standard plenum and it made more power. Down low, off boost, mid range, top end, it made more everywhere.

The underlying problem was airflow distribution, with the Trust plenum it had to be tuned too rich for good power on 1,2,3 and 4 because it was lean on 5 and 6. If I tuned it for max power A/F ratios it would have detonated on 6 a lot and a little on 5.

Common Steve, you know I'm a low boost, hi airflow person. You are not going to run enough boost in a high power application to overcome airflow restrictions without doing "internal mods". This was a no "internal mods" thread and my posts followed that principle.

You are right about losing pipework being better for response, it's a worthwhile target. The important thing here is the volume of air in the pipework, not the length of the pipework. I have just recently compared the volume of our pipework for the standard RB20 plenum and inlet with the volume of the pipework for the RB26 plenum. I just filled them up with water and measured the volume (off the car of course). The intercooler is the same, just the pipework is changed.

We use the 120 degree bend at the throttle body style of pipework in 63 mm to match the standard plenum. For the RB26 plenum we have to use 80 mm pipework as that is the size of the inlet on the plenum. The shorter length of 80 mm pipework was not enough to over come the effect of the 17 mm larger diameter pipe and it held 0.5 litre more water (=air).

So the response, due to the volume of air in the pipework, will be slightly less using an RB26 plenum compared to an RB20 plenum. There would be no reason to expect that the Trust plenum would give any different a result.

Hope that clarifies my position.

[B-Man]

I have a huge dilema with this:

I had a front facing plenum on my standard motor (GCG turbo, EMS ECU, fuel pump, injectors, cooler, etc) - and my motor went pooof - It could have been anything that caused the motor to go. The suspician is ringlands - Haven't had the head off - I tested the compression as follows:

Cylinder 1 - 127 PSI

Cylinder 2 - 55 PSI

Cylinder 3 - 150 PSI

Cylinder 4 - 40 PSI

Cylinder 5 - 50 PSI

Cylinder 6 - 50 PSI

(Cyl 1 is at the front of the car right ?)

This was a dry test.

Seems that what Sydneykid is saying 'might' have happened in my car - I'm pretty sure you can't adjust the fuel on individual cylinders with the EMS so this would not have been done.

I'm stuck with the front facing plenum at the moment and to revert back to the factory one, I would need to source one as my current one is a cut and shunt job. Then I would need to get the cooler pipework redone.

I'm getting the engine rebuilt with forged internals and plan to get 250-300 rwks out of it. I'm changing the EMS to a Power FC, changing the hi-flow injectors to 550 Sards -

What to do about the plenum ? Leave it and tune it rich ? Replace with factory or get a Trust/Greddy one ?

Which ever way I look - there is a limitation !

This time around I want to build/tune for reliability - So taking the most conservative approach is best for me.

What do you guys think ??

[Sydneykid]

Hi B Man, they way we assist the poor distribution is to get the injectors flow tested and put the highest flowing one in #6 and the next highest flowing in #5 etc. Then tune it on the conservative side of rich while checking the exhaust primary pipe temperatures.

Your problem looks like more than just that to me, I would be looking at fuel flow first ie; is the fuel pump big enough to supply the required flow at sufficient pressure above the boost level. This will also confirm that the fuel pressure regulator is OK as well.

If it's an RB25DET for 250 to 300 rwkw, then I would be looking at refitting the standard plenum. It will do the job just fine. If you want further confirmation (other than me) have a look at Ben's HPI R34GTT, it made 292 rwkw with the standard plenum on Croydon's dyno.

Hope that helps

[Ronin 09]

Having said that, sydneykid, have you ever experienced cylinders 3 and 4 running lean using the stock intake manifold? It would look to me that they too will be getting uneven airflow; unless there is internal baffling to redirect air. If anything the uneveness with airflow would be worse with the stock manifold - fluid flow theory tells us that air is much more likely to continue flowing in the direction is is currenly moving, and in a stock manifold situation it would be straight into 3 and 4.

I remember someone posting that they experienced 3 and 4 being a little burnt compared to the other cylinders when they pulled their motor down, whether this was to do with running lean or otherwise they weren't sure. Some sort of evidence either way would be good.

As for the cut and shut of the original plenum, i don't think that this is as good a solution as a proper front facing like a greddy. Reason being is that the internals of the stock manifold should be optimized for the flow coming in from the side, thus by moving to the front it may ruin the flow characteristics. My suggestion thus would be to either change back to a stock plenum, or change to a trust/greddy one. Hope that made some sort of sense.

[Sydneykid]

Hi Ronin, after having spent several hours with Frank Durney (ex Williams F1 Aerodynamicist) on a couple of occasions, I can confidently say "I know nothink" on the subject of fluid dynamics. But what I can say is I have not seen consistent evidence that supports the theory of poor distribution of airlfow to 3 and 4 in a standard RB20/25 manifold. There is a little bit of evidence to suggest that the fuel rail may be a more likely suspect, but even that is not supported by sufficient data.

Personally I lean more towards the fact that they are the centre 2 cylinders and therefore run a little hotter. Nissan designed the water flow charactersitics pretty well I reckon, but the middle cylinders are always more likely.

I definitely agree with the poor flow results from moving the throttle body to the front on a standard RB20/25 manifold, it's a shocker.

Hope that adds some more to the thread

[Steve]

Sydneykid, fair cop on the boost point.

I would agree with you that if you havent done other things first, do them. I have seen flow bench comparisons that show a slight difference between the trust and stock down low and midrange - the trust item lost a few cfm, where it did win was up top.

Have never driven a before/after comparison myself, flow bench testing wouldnt really be able to take into account the reduction of pipwork volume/restriction unfortuneately. I think it is a bit unfair to compare stock RB20 intercooler piping with GTR piping. More accurate if you were to consider how much volume would be lost JUST by reducing the pipework.

Consider though too, would they put a front facing plenum on GTR if the standard one was so superior at the stock GTR target hp level?

Too many people I have spoken too says it doesnt make a huge difference, in power, but they get a crisper throttle response. I cant ignore the voice of many.

[Sydneykid]

Hi Steve, GTR's have individual throttle bodies after the plenum. This is much better for throttle response than a whopping great plenum after a single throttle body.

The problem is the Trust plenum (like the GTR one in my personal experience example) has an 80 mm inlet. Running 63 mm pipework up to a 80 mm throttle body would disrupt the airlfow through the butterfly something fierce. So you have no real choice but to make the pipework from the intercooler to the plenum out of 80 mm diameter pipe. Particularly if the intercooler has an 80 mm outlet. It would no be good for airflow quality to go 80 mm out of the intercooler and then down to 63 mm pipe and then back up to 80 mm at the throttle body.

So what I did was use 63 mm alloy pipe from the turbo to the GTR intercooler, with a step up silicone joiner to the 80 mm intercooler inlet. I then used 80 mm pipe from the intercooler to the GTR plenum. The result was 0.5 litre more air in the pipework (not including the intercooler). I believe anything else would have made the response worse due to disturbed airflow.

On turbo inlet systems flow bench comparisons are a bit nebulous at best. A flow bench sucks up stream and measures the resistance to that suction. In a turbo engine the air is blown (boost) not sucked, so the results are quite different.

The guys I have asked about improved throttle response, all went from the "across the front of the engine and behind the radiator" type of pipework. Or the "across the back of the intercooler" type of pipewoprk.

We found a noticeable improvement by going to the 120 degree at the throttle body style, this eliminated considerable pipe length and 2 X 90 degree bends. Unfortunately I did not measure the difference in volume from that change.

To summarise (and get back on the point of this thread), on an engine with standard internals, I would rather change the pipework to the 120 degree bend at the throttle body than change the plenum to a front throttle body style. You get almost similar improvement in response (due to the lower volume of contained air) without the inherent dissadvantages of aftermarket plenums.

Hope that adds some more to this interesting thread