Overall Advantages Of Aftermarket Rb25 Inlet Manifold ?

[discopotato03]

Of late I've been working on , around , my RB25s inlet manifold and TB inlet pipe and its all a right royal PITA .

Coils and plugs are hard to get to and fixing the turbos water return hose behind the head was something else .

Life has to be so much easier with some alternative to the standard inlet manifold .

Obviously most people who make a change want the throttlebody pointing vaguely in the same direction as a GTRs plenum inlet does so they can use a cross flow intercooler again GTR style .

The choice seems to be the GReady or Plazmamans and I'm curious to know if both give equal access to water plumbing etc .

Also I'm curious to know if they are an automatic defect should unwelcome eyes get a look under the lid .

I am told that if you use the factory through the inner guard tube gadget from the same series GTR there is no loss of strength in that area .

The easiest is probably the GReady style inlet and it possibly gives the impression of being more standardish to look at anyway .

A .

[KiwiRS4T]

I have a Greddy copy. It certainly improves access to the coils and plugs but annoyingly it is not as straight as the RB26 one and so takes up a lot of room. Also between that and my M/C stopper there is not enough room to relocate my oil filter so I have just gone for the cooler only. It is still a pain to change the filter.

[discopotato03]

I was hoping that things in and around the Greddy would be easier to get at and the water plumbing nightmare easier to deal with .

Can you explain what you mean by not as straight as the GTR system .

A .

[75coupe]

I have a RIPS intake plenum and whilst i can fit the greddy oil filter relocation plate in the place it was made to be the iac & aac lines under the plenum (i relocated them to under the plenum rips puts them on top and probably for good reason) are a maze of tubing its pretty tight under there...

But its done now and yeah it looks neater, the intercooler piping is shorter, the hot side is hot and the cold side is cool and i can change the plugs easier...

[WMDC35]

i have greddy style, as mentioned above, makes it nice & tidy on top but underneath is worse then the stocker

[KiwiRS4T]

Here's a pic of my engine bay with the Greddy copy FF plenum. You will see that the place where the throttlebody bolts on is at a much sharper angle than the RB26 one.

[discopotato03]

I either forgot RIPs did one or didn't know . Must search to see how they are .

Plazmas ones are supposed to be exy but whats access like under those ? They use the std lower section of the factory manifold don't they .

A .

[Hanaldo]

Access to the oil filter with the Plazmaman is horrible. Impossible to get to from the top, can only get it from underneath. And if your car is as low as mine, you'll hate it haha. Even checking the oil level is a bit of a bitch now, be prepared to lose skin on your knuckles getting the dipstick out! Also forget about ever adjusting the IAC valve again. Not sure how bad it is on the standard 25 design, but if it's anything like the Neo then it is actually literally impossible.

To sum it up, the only real definite advantages are looks and ease of access to the spark plugs and coils. Everything else is made a fair bit more difficult, so it kind of cancels out. That said, if I could go back I would still do it again. The looks are a pretty big advantage

Edited October 28, 2012 by Hanaldo

[89CAL]

The Oil filter is not so bad to get to with the Greddy/Greddy Copy plenums. The water piping underneath (if its the stuff I'm thinking of) is a real pain, but I have never had to deal with it since I put the plenum on

It would probably be better if you could do the plenum off the car and make it all neat under there but because mine was in car and I needed to get it back on the road ASAP I didn't get to do it as neatly as I'd have liked

It's definatly alot easier to get to coilpacks etc, which if we are honest, is going to happen alot more then playing with the water piping under the plenum (Hopefully anyway )

I'm happy with the ease of acces at the top of the engine now, It looks a bit odd if you have the bonnet up and stand back from the car a bit because there is so much gap under the strut brace

There the best photos I could find, if they help at all

Edited October 28, 2012 by 89CAL

[FineLine]

25/30 fixes the gap under the strut brace,

[sky017]

+1 worth doing . much cleaner and easier to service . as long as its done properly you shouldnt ever need to get on the underside of the manifold .

[discopotato03]

Well from what I can see I'm beginning to think they create as many problems as they solve for a pure roadie . I just fixed that mongrel turbo return water line behind the head (drivers side) and I can olny imagine what it would be like to spring a leak under a Gready or Plazma setup . Probably not going to fix it by the side of the road and if your Skylines like mine its an effort to get at the sump plug let alone coolant hoses .

I can sort of understand why people used to attempt to remodel the std upper section because at least you can unbolt the thing from the top if all else fails .

Actually thinking about it maybe Oyay , or however he spells it , could consider a different version of his plenum that has long bolts accessable from the top . Crush tubes through the thing may not look sexy but at least rusting bolts/studs wouldn't flake into your engine and again you can get at the fasteners easly to pull it off for service work .

One of my golden rules is that I never do mods that make servicing difficult to impossible . Really the only difficult part in getting at the coils and plugs is getting that damned cover out from under the crossover pipe . As we know its those two small steel pipes and how they mount to the cross pipe that causes all the grief .

Just to cover all the bases how difficult is it to get at the snake pit under a GTRs inlet manifold ? I don't intend to adapt this system to my 25s head but it would be good to know anyway .

You can thank Nissan for making the flange patterns different because they clearly did it to stop us doing the logical thing .

Probably the most complete legal way if you want a fresh engine that isn't the original is to bust the bank and build up an RB26 or maybe a 26 head on an R32 RB25 block to avoid the front water hole issue . Dunno if the various roads authorities are smart enough to tell by block numbers if you had a 32 25 block in an R33/34 GTST/GTT .

A .

Edited October 28, 2012 by discopotato03

[89CAL]

I dont think any of them are terribly easy to play with the coolant plumbing under the plenums

Honestly though, what are you doing that you think your going to need to play under there. I've had mine in for probably 3 years or near enough to it now, and not had a single problem at all. It's saved me hours on servicing though

[GTSBoy]

I don't know why people who want/need to pull coils out don't just pull the crossover pipe first. I do it every single time I need to work there and it adds about 5 minutes to the job.

[89CAL]

I don't know why people who want/need to pull coils out don't just pull the crossover pipe first. I do it every single time I need to work there and it adds about 5 minutes to the job.

I used to do this, I got the plenum as part of a deal so thats the main reason I have one. It does make it alot easier but. Just have to pull the breather pipe and ignitor off now

[hypergear]

They looks good from top.

Performance wise I've had few customer installing aftermarket inlet manifolds.

2x made no difference in power but gained lag,

1x made tinny bit of more power with better response,

1x made less power with more lag.

The majority of people I deals with are within 250~350rwkws margin. I'm not sure at what HP range they start to take effects, but Personally I don't think they are worth getting.

[rob82]

They looks good from top.

Performance wise I've had few customer installing aftermarket inlet manifolds.

2x made no difference in power but gained lag,

1x made tinny bit of more power with better response,

1x made less power with more lag.

The majority of people I deals with are within 250~350rwkws margin. I'm not sure at what HP range they start to take effects, but Personally I don't think they are worth getting.

Yep seen the same results. The STD plenum length is just spot on for an engine developing power below 7000rpm. You may start to see gains with the shorter runners above that but as far as torque and response go stay with the STD plenum and get over removing the cross over when doing the plugs.

[Dan_J]

They looks good from top.

Performance wise I've had few customer installing aftermarket inlet manifolds.

2x made no difference in power but gained lag,

1x made tinny bit of more power with better response,

1x made less power with more lag.

The majority of people I deals with are within 250~350rwkws margin. I'm not sure at what HP range they start to take effects, but Personally I don't think they are worth getting.

those results vary a bit, was the middle customer running stock bottom intake runners with a FFP bolted on top ?

anyone have results, response/ lag wise, with a 2 part FFP ?

Edited October 29, 2012 by Dan_J

[hypergear]

Yes, that was a plazmaman item. By doing so he's also shortened his cooler piping, that could possibly be the response gain.

[discopotato03]

Hmm , do you think by any chance that the Neo RB25DET inlet manifold and plenum section has any advantage over the R33 RB 25 pair ?

It sounds like the lower section has longer runners and that the plenum was different possibly for packing reasons in an R34 bay ?

I know there are differences with the R34s secondary TC throttle but not sure if the R33 TB can be substituted . Also isn't the IAC housing different , not sure if its electrically different .

Possibly a lot to hope for but factory engineering can be hard to beat sometimes from a later slightly higher performance version of a given engine .

A .