Jump to content
SAU Community

  

110 members have voted

You do not have permission to vote in this poll, or see the poll results. Please sign in or register to vote in this poll.

Recommended Posts

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 by Bsa
Link to comment
https://www.sau.com.au/forums/topic/384598-street-car-peak-power-where-is-best/
Share on other sites

  • Replies 89
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Posted Images

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 by stocker

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 by Bsa

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

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 by Bsa

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

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.

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

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?

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

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

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

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

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 :P

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.:cheers:

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

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now



  • Similar Content

  • Latest Posts

    • Was there ever a model of the Stagea m35 that didnt have a badge on the grill? I thought I saw that somewhere, some aero edition or something? I cant find it again? davemoto
    • Its a 2002 vr-x four VQ25DET, silver. Coil overs, lowered, polished alloys and sport exhaust. Bit of a project, was sitting in a shed for a while but runs and drives great.
    • I wasn’t able to replicate the sound anymore. It was a one time sound so maybe it was just coincidence but it was like small pebbles being dropped in a coke can.   should I try cleaning the MAF? It could be it’s functioning but dirty? I don’t know.
    • Update 4: Hi all. The car drives again! Haven't driven for long, only to store it in the garage again, but the test drive was successful. The coolant and oil leaks seem to be fixed for now. Temps on the engine were also very good, while moving I never even saw 80C water during the approx. 30 minute drive. Ate up all the coolant in the reservoir though so will have to fill that even more when I go to the car next time. One thing that pisses me off is that the RPM gauge is still f**ked, I even resoldered the board twice and used copper paste on the silly screws that are used as connections. Next time I take it out I'll take apart the board and fit new components, I'll see if I can get a replacement IC for it.  I have an appointment set for 22nd of September for the engine tune to 370hp. Alignment also still needs to be done. My hope is that I can get all the legal stuff over with by the end of this season. Anyone of you have advice regarding intercoolers? Currently there is an APEXI core fitted, one of those weird hybrid ones, 600x270x76. I don't think it's bad but it's not new and now I still have the chance to change it now to legally include it in the paperwork. Only issue is that the only options that would arrive in time are a HKS Type R intercooler or generic Ebay spec intercoolers comparable to a JustJap one. Ideally I'd order a Plazmaman but it takes over a month to receive which would mean making the car legal has to wait until next season. Would love to hear some input on this. Same story for my injectors, the previous owner was a nunce and put ID 1050x on the engine. They work but are obviously not ideal at "normal" power levels. But I don't see a reason to change them unless the tuner says it's necessary. I read online before buying a different exhaust that the top secret style rear diffusers won't fit due to the size of the rear resonators. My buddy and I made it work by slightly "adjusting the shape" of the mounting bracket and making some spacers out of 3d print for the mounting bolts. Fits like a charm. Just putting this here in case someone has this problem. Even the hefty HKS Silent Hi Power rear can fits without hitting anything.
    • Well they got my money but they are not getting my gearbox ! 
×
×
  • Create New...