Street Car Peak Power Where Is Best

[Bsa]

I'm fabing a plenum up for myself. It's going onto a rb25 and iv never made one for a 25 before. Done a few for rb20 but the 25 seems to be totally different in design. If it turns out to work really well ill make up a few.This is a serious question i don't want stupid answers as I'll be using this info to build the plenum. I'll explain later after I see what people have to say cheers everyone

Edited December 1, 2011 by Bsa

[stocker]

building a plenum is easy thing to do but to get it right is a whole different story................best to buy one like a greddy or if you got the cash get a hypertune item worth every cent bit bias as i have one........................i played with inlets so many times its not funny had 5 different set-ups in the end up using a late model magna provided the best results you bsee the 2nd link........ mate scott at insight me and him did alot of r&d on them for my la lancer with 2.6t sigma motor heres one of the twin throttle body inlet i got fab'd up with full custom spun ram tubes from jnt,ford t/b.s etc.........

best to stick with stock with larger throttle body or spend the big bucks on a inlet thats had r&d and proven its self.......sorry if sound rude but been done that path...........theres a maths to building inlets they why car companies invested big $$$$$$$$$$ into r&d

custom twin thrott;le body inlet

http://rides.webshot...103472179sJBhjJ

this mod'd factory item with the thrttle body relocted was the best out of the lot

http://rides.webshot...578631407aLIaHl

Edited December 1, 2011 by stocker

[GTSBoy]

Bsa,

Do you really think you have that much control over it?

Edited December 1, 2011 by GTSBoy

[Bsa]

Done tones of research and have learned all the mathamatics behind desining one. the plasma man plenum don't do much other then store more air then stock. The reason for more response is the fact the air doesn't turn back on itself so when the valve closes the air that wasn't consumed pulses back up the runner causing turbulence. So removing the bend allows the air to pulse back into the chamber faster causing less turbulence so quicker response very simple really. So plenum size is the next thing smaller smaller the plenum gives more resonce due to increased velocity. larger the plenum means more air up top more power but less midrange. The stock runners are designed for midrange but also high rpm well untill stock limiter. My old boy is a mathematical genius seriously can work out anything so he is helping on the design. I forget to mention I will be utilizing the bottom runners so no mods are really required just need to get flow to the runners equal

Edited December 1, 2011 by Bsa

[zebra]

So you want a small plenum with the standard runners?

Use the standard plenum

and there is more than just mathematics behind it...do you have access to fluid dynamics software etc?

[GTR_JOEY]

Obviously most of the time ur revs are goin to be below 4000 rpm,

I voted 4000 to 7500 cause that's where I'll want my power will be

It's not realistic to have decent power under 4 for my set up and I'd rather not rev the ass out of it

Just my justification for my choice

[Bsa]

Did you only half read what I wrote. I understand the stock manifold is capable of the job I need but lets face it looks like shit. Forward facing looks so much neater and it improves pedal feel and maybe a bit more torque y not. Mathematics is the major factor in design your dreaming if its not. And yes a have access to getting it flow tested and all that which will be done

Edited December 1, 2011 by Bsa

[zebra]

mathematics for runner length and plenum volume yes, but that wont tell you if the distribution is even.

By getting it flow tested, how many prototypes are you going to make and test before it is right? (you will need to test on the dyno too)

I learnt a long time ago to leave all that stuff to the companies that pour $$$$$$$$$$$ into R&D on these things

[GTSBoy]

Unless you change the runner lengths you will not move the peak torque or power points pretty much anywhere at all. The resonances in question have to do with the tuned length of the runners and little else. If you have a big plenum volume, you will make a little more power. You will also have a better chance of not getting poor distribution, but that's only from giving the air more room to move at a lower velocity. A little plenum will make less power and you will stand a better chance of getting poor distribution because of constricting the flow and forcing high velocities past the first couple/few runners. A big plenum will give soggier throttle response. A little plenum will give sharper throttle response. But even those differences are small - there's a limit both to how small you can make it and how big you can make it and still fit in everything you need. That size range doesn't cover a lot of difference in response or total power. Curvature or otherwise of the runners will likewise have such a little effect on anything that you would be hard pressed to tell the difference there either. I seriously think that you are fooling yourself if you think you have any chance of affecting much other than flow distribution between runners.

[Bsa]

That's y iv taken aspects from all the leaders. Tell me how many tests have been done on a 300 dollar eBay special fck all it works so people buy it. I can do all the work myself won't cost much as my mate will flow test it for me and I get the alloy for cost. I'll make as many as I need to get it right

[zebra]

Unless you change the runner lengths you will not move the peak torque or power points pretty much anywhere at all. The resonances in question have to do with the tuned length of the runners and little else. If you have a big plenum volume, you will make a little more power. You will also have a better chance of not getting poor distribution, but that's only from giving the air more room to move at a lower velocity. A little plenum will make less power and you will stand a better chance of getting poor distribution because of constricting the flow and forcing high velocities past the first couple/few runners. A big plenum will give soggier throttle response. A little plenum will give sharper throttle response. But even those differences are small - there's a limit both to how small you can make it and how big you can make it and still fit in everything you need. That size range doesn't cover a lot of difference in response or total power. Curvature or otherwise of the runners will likewise have such a little effect on anything that you would be hard pressed to tell the difference there either. I seriously think that you are fooling yourself if you think you have any chance of affecting much other than flow distribution between runners.

This x 100

plus, any thing regarding manifold design for Atmo engines, tear it up and burn it, because it means precisely shit in a forced induction application.

Providing everything flows well enough not to restrict airflow than runner length wont affect power, just response.

ie a long runner intake will get the engine breathing heavier at low revs, hence getting the turbo on song sooner.

Which unless you are purely doing it for looks the standard plenum is the way to go.

iirc you are going for a GT30 or T67, not big enough in my books to warrant spending shit loads of money on a fancy plenum, if you want every possible ounce of power out of the turbo than yes custom plenum with ram tubes and centre feed large volume plenum etc etc + lots of head work + custom cams + f**king about with injector placement.

you are obviously capable of some decent fab skills, why not try a Greddy plenum and make up some spacers to play with the runner lengths?

[Bsa]

I understand I won't make a huge difference but anything is a gain if it creates better flow also. But at the end of the day most people buy them cos they look better most people don't care what it does as long as it looks good and adds better response they are happy

[Bsa]

If I fail then I will. I made one for my 20 cut the flange off shortened the runner by 20 mm and put the plenum I made on car was more responsive and seemed slightly more torquey I'm not after every bit of power I'm just interested if a simple thing can aid. Also if I can do it myself I will I hate buying things I'm capable of even if it ends up cheaper. I dont see why you guys are sitting there telling me to not bother one day you could buy one. hks didn't just pop out of no where one bloke decided he could do it better and now it's global I'm not saying I could get to that point but if I can do it better then some then I will and have extra cash at the end of the week because of it everything starts out just a idea

[stocker]

the alloy bits and pieces will cost jack all but the flow testing,dyno time,gas for welder,getting custom velocity stacks or bellmouth it will cost more then you think to build a quaiilty manifold

hypertune do a rb25 inlet.............save on all the time fabicating and all the head stress

http://www.hypertune.net/index.php?option=com_content&view=article&id=88&Itemid=84

[Bsa]

No one is getting me I can make all my own bit and prices. just material costs. I don't mean to be rude but all I'm asking is for people's preferences for a street car not tell me I'm stupid for having a go

[DVS JEZ]

It depends on where ur turbo and cam setup will be making power/torque aswell. Best to match it all together.

Oh and dyno testing is no problem. Ill draw up a mortgage agreement now so we can start. Your gonna make me rich

[zebra]

Well 2 of the choices will involve larger cams, 5000-8500 is huge cams

[Bsa]

Haha I I'm sure I will jez but If it works then I might get lucky. Back to back runs will be happening with both plenums. It's not like I'm doing the impossible

[The Bogan]

I picked 3 to 65, for the street you want early responce I feel, mine isnt coming on till 4.5 which is fine on the track were you can keep it on song but for the street mine isnt ideal, a stock SS with get me of the line and unlike the track on the street I cannot then blow by him when I hit 3rd, unless your a knob like the young blokes around here who think the road is their own private race track.

No offence Im just adding a little vent.

[DVS JEZ]

Haha I I'm sure I will jez but If it works then I might get lucky. Back to back runs will be happening with both plenums. It's not like I'm doing the impossible

Yep. Keep ur current piping so u can test against the stock plenum too.

What throttle body u gonna run