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Old 06-05-2004, 02:32 AM   #1
not2smart
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who has custom intake plem??

afternoon every1......

i would like to know if any1 here has a front facing intake plem or a custom made job for there 25det and are willing to let (us) have a look at it as i wish to make my own but not sure if i should do the whole top intake out of s/st or just cut and weld the standard 1??
so any picture's would be great as it's just to get a fair idea of what other people have done.
thank you
jay.

ps....is there a noticable performance upgrade having it done other then it tidying up the engine bay?
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Old 06-17-2004, 03:35 PM   #2
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Re: who has custom intake plem??

front facing is worst. It does not distrubte the air evenly.
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Old 06-18-2004, 02:14 AM   #3
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Re: who has custom intake plem??

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Old 06-19-2004, 04:57 PM   #4
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Expect no big gains from a different intake manifold. certainly not when you're using a turbo. You could use it to increase torque at low revs but you need quite some space for that.

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Old 06-19-2004, 09:09 PM   #5
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Re: who has custom intake plem??

Quote:
Originally Posted by Derby
Expect no big gains from a different intake manifold. certainly not when you're using a turbo. You could use it to increase torque at low revs but you need quite some space for that.

Derby
Really?

R33 GTS25t.
Mods:

T41B Turbo, front mount, 650cc injectors, Bosch 044 fuel pump, Nismo raising rate fuel pressure reg, 1.2 bar - 240rwkw. (321hp)

Greedy intake plenum add same everything else including throttle body - 266 rwkw (356hp)
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Old 06-20-2004, 12:35 AM   #6
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Yes, intakes make a huge difference.
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Old 06-20-2004, 02:28 PM   #7
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From the graphs i have seen (made with Gt power suite) a different intake doesn't change a thing. For NA engines it can make nice power gains but for turbo's...no

And razor 35 hp at what rpm. it can make a difference if you change the whole intake manifold from filter to valve. But a plenum change makes not much of a difference. (or the stock intake is just one huge mistake on intake technique)

I've run some simulations, i did quite some research on intakes and pulses and i'm not impressed by the advantages in combo with a turbo.

Derby

By the way there is some difference between a plenum and an intake. The plenum is the 'reservoir' which the engine can take air out (bigger plenum mkaes it look like the engine can breathe like it breathes without any filter or other obstruction.). The intake is the whole package. Kleks (or what the you call it.) can make some difference.
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Old 06-20-2004, 04:50 PM   #8
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I have seen as much as 50hp change from one intake to another, in Supercharger, and Turboed applications. Yes, they can and do make a difference. But, it also depends on what you are starting with.
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Old 06-20-2004, 06:07 PM   #9
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Re: who has custom intake plem??

Quote:
Originally Posted by SkylineUSA
I have seen as much as 50hp change from one intake to another, in Supercharger, and Turboed applications. Yes, they can and do make a difference. But, it also depends on what you are starting with.
Yeah what you start with. and it also depends on the end power. thus percentages. 50 hp on 900 hp isn't much of a difference. I'm talking about small engines (1.4-2.0 litres)

Pulses (is what we talk about mainly) are dampered(sorry for my bad english) in combination with pressure. The best i've seen is a pressure rise of 0.05 bar. (1.4l Turbo with a special designed/custom made intake.) problem was the engine went completly dead at 2300rpm.

Other then stock intakes are usefull if someone with knowlegde has worked on it.

Derby
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Old 06-20-2004, 11:54 PM   #10
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Re: who has custom intake plem??

I was reffering to engines with less than half of that power, but I am also talking about V8s.

Your speaking from what you know, and I am speaking from a totally different type of knowledge. Yes, you can change intakes on a turboed engine with less than 400hp, and you can see a rise of 50 hp depending on the intake.
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Old 06-21-2004, 01:37 AM   #11
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Re: who has custom intake plem??

Derby its very, very manufactor and engine spefic as to what sort of gains can be seen by an inlet manifold change on a forced induction engine.


Nissan has a reputation as a builder of very strong engines. Its quite clear that most of thier R&D work has gone into engine strength and lots of boost to over come weakness's in the flow capablities of the head and manifolds.
Also remember that the RB series of engines (whats being discussed in this thread) are based heavily on an engine orginaly designed in the 50s by Mercedes.
Its intake design has been little changed since the 80s, and it was done at a time when Nissan did not have a lot of spare money to spend on refining an intake. What they had worked, extremly well, they didn't need to improve on it.

However as it happens technology and industry knowledge has improved a lot since 1988, and there are now aftermarket manifolds that are signifcantly better than the orginal, and will yield quite noticable gains.
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Old 06-21-2004, 06:24 AM   #12
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all right i'll give up.

But i want to know one thing. These gains in power(50 hp) are that 50 din HP's or are that 50 marketings HP's?

No offence,

Derby
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Old 06-21-2004, 12:13 PM   #13
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Re: Re: who has custom intake plem??

Quote:
Originally Posted by Moppie
Derby Also remember that the RB series of engines (whats being discussed in this thread) are based heavily on an engine orginaly designed in the 50s by Mercedes.
Its intake design has been little changed since the 80s, and it was done at a time when Nissan did not have a lot of spare money to spend on refining an intake. What they had worked, extremly well, they didn't need to improve on it.

What makes you say this Moppie? I don't recall the Merc having a DOHC head, "bearingless cam journals", oil pump mounted to the front of the crank, 4 valves per cylinder to mention a few. Saying that is like saying the BA16 is based on the Ford Flat head 4.

Also Nissan did refine the intake since the 80's. It change quite a bit though the R32 and R33 non-GTR intakes are simular they infact are not the same.

Darby unless you know what the non-GTR intakes looked like on the R32, R33 series it is hard to envision an aftermarket plenum would make. The intakes curl upwards back over the top of the head with a single inlet feeding into a rectangular shaped manifold then 6 runners curling downwards to the head. The inlet is dead centre on the long side of the rectangled chamber. If you were to look at the design it is simple in theory but not practical in making efficeint power.
The factory intake on an SR20DET motor is a good example of how an intake plenum should look, though it is still not the best of design.

Looking at a GTR intake plenum it uses 6 throttle bodies instead of one single one found on 99% of cars. This is what the aftermarket ones copied to bolt onto the other RB series motors. Only the GTR was designed for "high performance" not a family sedan nor a sports car, but true supercar status.

I'm short on time this morning but will endevour to explain it a bit deeper when I get home from work tonight.
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Old 06-21-2004, 01:37 PM   #14
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Despite your effort to explain the shape size and form of the intake, i still can't make a picture out of it. (my fault).

Every designer has his own interpretation of a good intake.

The best i've seen is the intake of the BMW V12. I'll look to get some pics.

And what about exhausts. then i mean from valve to catalyst?

I'm looking forward to a more deep explanation, RazorGTR

Derby
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Old 06-22-2004, 02:56 AM   #15
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It took me a while to find decent pictures to post up to show you just pathetic the non-GTR intake manifolds really are.

Here you can see the inlet pipe to the throttle body which then mounts to what is described as the front of the intake "plenum". Notice the rectangular shaped box that feeds the runners. You should also now see which cylinders are going to be fed the best volumes of air based on volumetric calculations/force/pressure. Now this picture is of an N/A GTS but the intake is the same on the base turbo models.



Here is a good picture though I had to blow it up quite a bit of the intake runners split.


What a proper plenum will give you is better distrabution of pressure vs volume. Good inline mainfolds will be larger at the front end and smaller at the back end. This is to prevent more air entering the back cylinders vs less to the front based on pressure/volume.

The GTR Plenum comes close but the back is still too big compared to the inlet hence many top cars go to either the Trust, Top Secret, or Veilside plenum.

A common unknown problem with the RB motors is the non-GTR's always run leaner on the #3 and #4 cylinders, while GTR's are natorious for #6 and sometimes #5 being the leaner ones. This is not theory but reality, as when you check the plugs for leaness or most noticably pistons for detination it always will show up on these cylinders first. Some say it is the fuel rails but if that was so, then all the RB motors would be leaner on the same cylinders.

How much of a difference a plenum would make on other motors, I can't say as honestly I've not studied them as close as i have on the RB motors. I do know that intake manifolds on V8's is critical in getting them to run properly on all 8, this makes the same sence in this case we are discussing. The runners on a 4 bbl intake make or break the manifold, same applies here except it isn't the runners as much as the holding or expansion chamber of the intake. A square or rectangular shaped one will never be as effecient as one that is smoother with a better overall delivery system designed into it. I would venture to say the system Nissan came up with for the non-GTR is more due to the engine configuration more so than a performance orientated design. On the turbo models the small factory intercooler is located in the left front between the inner guard and the bumper at the bottom. The piping goes in and back out in a small area then preceeds back over the mid section of the motor as you can see from the pictures.

Some guys have tried to cut the throttle body mount, patch and weld the factory intake body, then cut and weld the mount onto the front of it to simulate a proper plenum. They do this when the run an aftermarket front mount to avoid coming either back over the top of the fan, or replum it back across the front of the car behind the new front mount to tap into the existing pipe work. I've yet to see any gains from this though some claimed it. To me the air is trying to litterally travel 90degs down the runners, this would make for large amounts of turbulance, while a poper plenum would have the inside guide rails if you will, to guide the air into the plenum runners then into the head.

Hope this helps clarify it a bit more.
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