Custom Fighters - Custom Streetfighter Motorcycle Forum banner
1 - 16 of 16 Posts

·
Fuck it, let's do it live
Joined
·
4,007 Posts
Discussion Starter · #1 ·
So on researching stuff for the potential addition of a turbo to the Busa build, it's become obvious that I'll need a plenum (I think). It seems this takes the place of the airbox and creates a large volume area for the constant supply of turbo air to reach the inconsistent demand of each of the cylinders.
For the record, my only experience with turbo anything is playing with 7.3 Powerstroke engines... which seems vastly different to this.
From what I gather lokoing at pictures online, and I could be entirely wrong, it looks like there's a heater core type device inside the plenum, with water ran through it cooled by a radiator out front. This appears to do the job of an intercooler on a car, cooling the post-turbo air. This seems pretty inefficient, having two radiators instead of one (an intercooler).
So why couldn't I just run an intercooler instead of the plenum radiator? Am I looking at this wrong or missing something?
Also, some of the aftermarket plenums say stuff about injector options... where does that fit in with this?
 

·
Is my bike ok?
Joined
·
15,052 Posts
It takes two heat exchangers to accomplish the task of intercooling.

The plenum radiator you mention absorbs the heat from the turbo'd air and exchanges that heat in to the water inside that radiator. Then, the water inside that radiator gets pushed to the other radiator where outside airflow can cool the water that is inside. Then the process starts all over again. But this is a water-to-air type system you are describing. It might seem inefficient or redundant, but it's not.

For an air-to-air system, yeah, just plumb your turbo'd air through a radiator out front before plumbing to your carb enclosure.

However, are you sure you need to intercool what you're building in the first place? Unless your turbo discharge ( leading to the carbs) is extremely short, or in a cramped area, you may get all the cooling you need through the plumbing itself. Also depends on how much boost you'll be running. Low boost generally= low temperatures.
 

·
Fuck it, let's do it live
Joined
·
4,007 Posts
Discussion Starter · #3 ·
No, I'm not sure at all. It just seems like every turbo Busa I see online has one.
I'd be looking at maybe 7-10psi if I had to guess. If there were no plenum or intercooler, I suppose I'd route it as directly as possible to a custom or modified stock airbox.
 

·
Cmon' Kitty!
Joined
·
777 Posts
Poor man's intercooler is to run a pipe to the back then forward again.
 

·
Fuck it, let's do it live
Joined
·
4,007 Posts
Discussion Starter · #5 ·
Might it be possible to use a factory radiator as an intercooler with a little modification?
 

·
Remi's Dad
Joined
·
17,593 Posts
nope. i would say with enough mods you might BUT at that point just build a custom intercooler. You can run premium and a slight ignition retard to prevent detonation until you can/want to afford a nice intercooler.

Turbo+cheapskate= more money/time in the long run
 

·
Remi's Dad
Joined
·
17,593 Posts
No, I'm not sure at all. It just seems like every turbo Busa I see online has one.
I'd be looking at maybe 7-10psi if I had to guess. If there were no plenum or intercooler, I suppose I'd route it as directly as possible to a custom or modified stock airbox.
Without a plenum the halves of the stock air box would lift and it wouldn't be efficient. A plenum should have as much volume as space allows. I have a PDF of some formula 1 racers explaining what plenum design does and what works and what doesn't. I'll find it.


Key points: mucho volume and gradual change of direction if possible (less turbulence and dead air)
 

·
Fuck it, let's do it live
Joined
·
4,007 Posts
Discussion Starter · #8 ·
nope. i would say with enough mods you might BUT at that point just build a custom intercooler. You can run premium and a slight ignition retard to prevent detonation until you can/want to afford a nice intercooler.

Turbo+cheapskate= more money/time in the long run
I was hoping you would chime in, I was actually gonna message you tomorrow. From your comments in other threads you sound like you know your stuff.
It's more about the DIY factor than about cost for me (I'm a cheapass and will save pennies wherever I can, but if I have to drop a few hundred on something... whatever, as long as it's worth it). I can/have access to MIG and TIG, various CAD software and CNC machines, I can do composites, and so on... really anything but wood. I suck at making things out of wood. So I really prefer to make something than to buy it. I figure if it's something I know well, I can probably do it better (or at least good enough for my application) and if it's something I don't know then it's a great opportunity to learn.
As for the radiator idea... that came about from looking at intercoolers on eBay. They're all flat for cages and I would need one that's curved like the factory radiator, which led to the thought of "hell, why not just use exactly that."

Without a plenum the halves of the stock air box would lift and it wouldn't be efficient. A plenum should have as much volume as space allows. I have a PDF of some formula 1 racers explaining what plenum design does and what works and what doesn't. I'll find it.


Key points: mucho volume and gradual change of direction if possible (less turbulence and dead air)
I'd be interested in that PDF if you can find it... thanks!

So I understand I need a plenum, as it's basically the turbo version of an airbox (right?).
What I'm still unclear on is cooling the compressed air... can I use a simple intercooler or do I need an air-to-water setup in the plenum housing, and why?
 

·
Remi's Dad
Joined
·
17,593 Posts
can't find the PDF i downloaded it for a free on my last laptop. It's an old hard back converted to online.
"The Scientific Design of Exhaust and Intake Systems" by Smith and Morrison


To answer your "why do i need an intercooler"

-lowers heat (duh) hot dense air makes less power (simple explanation)

-high cylinder temps without an intercooler can cause detonation is most cases.

With moderate boost you may be able to skirt by, BUT an intercooled setup will ultimately be safer, make more power, and make your setup last longer
 

·
Fuck it, let's do it live
Joined
·
4,007 Posts
Discussion Starter · #11 ·
All good, I'll see if I can't find it on Google.

I understand that part, that cool air is denser etc. I also understand what high temperature and pressure do to gasses from a physics standpoint, if that's even applicable at this level.
What I'm wondering is why use the (more) complex and heavier air-to-water system in the plenum over a normal intercooler upstream from a (hollow) plenum? It seems like every aftermarket kit I see goes the former route, so there has to be a good reason.
 

·
Fuck it, let's do it live
Joined
·
4,007 Posts
Discussion Starter · #12 ·
So it sounds like there's a sweet spot in intercooler flow then... what defines it? What's too big, and what's too small?
 

·
Fuck it, let's do it live
Joined
·
4,007 Posts
Discussion Starter · #14 ·
Well, $800 is over the tipping point for being worth the end result for me.
What about doing the air-to-water setup inside the plenum, using a heater core off a small car as the cooler and a factory radiator cut in half horizontally to cool the water?
 

·
Fuck it, let's do it live
Joined
·
4,007 Posts
Discussion Starter · #15 ·
Or... homebrewing an intercooler with a few rows of aluminum square tube in a zig-zag shape with some heatsink fins between them?
 

·
Premium Member
Joined
·
683 Posts
Do bikes ever run water/methanol injection setups? They are pretty popular in the automotive world at least for drag racing.

It seems like that would be the simplest and maybe cheapest way to cool the intake charge although I have no idea how much would be needed for a full tank of gas. That might be problematic if you want to ride the bike any distance.
 
1 - 16 of 16 Posts
Top