Technical throttle bodies for FIRE engine

[Brooky]

hayabusa TB's are way too big IIRC they are something like 40-44mm

 

[arc]

info on various TB sizes can be found here;

http://www.msefi.com/viewtopic.php?f=29&t=6627

busa's are 46mm

 

[Slosei]

I know of two seis that use hyabusa throttle bodies cant tell ya how and whats done to them cos i dont know as such but they sure as hell do work wonders and with all good work like that it dont come cheap hence why i love the sound of a cento revin up to 9k rpm evan though it stops just after 8k rpm and speedo keeps moving lol
iirc it has more torque at bottom end over a standard p75
with work so well done the cars also have his name on them
besides my car lol i got the sticker cos he likes me lol

 

[craigb244]

Guys I dont know if anyone has mentioned this yet... but... have you noticed more and more 4 stroke scooters on the road. these are usualy between 49-124cc and "should" have pretty small TB. of corse you will need to find 4 of them but theres also more good news.... theres lots of chines copys been made so I would find a seller of these scooters and ask them.

 

[Brooky]

info on various TB sizes can be found here;

http://www.msefi.com/viewtopic.php?f=29&t=6627

busa's are 46mm

pffft, well thats not much cop, the bike mine came off, its section is empty ahwell, i know all i need to know about them

 

[randomizered]

pffft, well thats not much cop, the bike mine came off, its section is empty ahwell, i know all i need to know about them

The details are what people have contibuted hint hint

 

[MattMk1]

You lot really know your stuff! Never realised how much knowledge there was in this section.

One thing I'm confused about, is over fueling. Surely 4xITBs will give far too much fuel and you will end up with explosion far too aggressive for the walls to take or end up not being able to feed enough air to them to get a decent explosion?

Or am I being stupid and missing something *really* obvious?

 

[Brooky]

ECU will control how much fuel goes in, its no different to standard mpi fueling

 

[gazzaman2k]

You lot really know your stuff! Never realised how much knowledge there was in this section.

yes we know our stuff in the cento section we are real car enthuasts, mostly chav's and teenagers who like Halfords drive puntos (no offence :yuck

i just like little cars that can go well

 

[MattMk1]

ECU will control how much fuel goes in, its no different to standard mpi fueling

I don't get how you could do it off a standard ECU though. What about the sensors on the original TB.. would you just have one set or a set on each? What about the throttle cable?

yes we know our stuff in the cento section we are real car enthuasts, mostly chav's and teenagers who like Halfords drive puntos (no offence )

No, you are quite right there old chap.

*sparks up pipe and puts on slippers*

 

[Brooky]

well you dont use a standard ECU, it'll never control them.

throttle cable,make one fit out of the existing one.

 

[craigb244]

I highly doubt you could get it to run (or at least anywhere near how well it could) on a standard ECU.

On a motercycle the TBs are usualy in a line with a shaft with the valve discs on going thru all 4. the cam that the cable is on is normaly in the middle (2 tb on each side of it)

If you needed to fit a MAP I would run a tube from each manifold (after the TB) all connected together with one MAP. this *should* also have the advantage of been a ballance pipe keeping the engine at a smoother idle.

too right gazza man... cinqs are a new-age mini imho

 

[Slosei]

I doubt if Wolf Racing actually found those figures themselves (I mean, by rigorous empirical study)! Interesting that the figures don't differentiate between 2 valve and 4 valve engines, undersquare/oversquare engines, etc.

Nevertheless, those are not a bad starting point (but neither was my 29mm figure, lifted from Bell's book).

The point Stone Newt makes is a good one -- many many years ago CCC ran a comparison between a plenum chamber singleTB set up and a carb per cylinder set up on a racing pinto engine. With carb per cylinder, the engine lost out everywhere below 7k.

i am thinking he ment them figures by how much air can pass though a certain size throttle could be wrong
iirc 150cfm will pass through a 40mm throttle which equates to 100bhp someone check those numbers
Zak

 

[Slosei]

And a 33mm throttle will flow 103cfm

 

[Brooky]

you dont need a map sensor if your using AlphaN

 

[arseofbox]

And a 33mm throttle will flow 103cfm

I did calculate 4x38mm's could easily flow adequately for where I wanted to place the powerband on the T/C - I think thats ~ 450cfm, but cant find my book.

One thing that you need to be really aware of when selecting TBs is pressure increase across the orifice (maximum flow velocity at minimum area is Mach 1 ~350m/s @ ISA SLS conditions I think, but you really want to be between 75m/s and 120m/s else the fuel just wont cope with it).

But the runner diameter (ideally same as TB dia, tapering to port dia over long run), combined with the volume of the system is one of a number of different things that affects where the powerband sits - too wide and the band will be too high, too small and youre likely to restrict the system's breathing.

Read up on the subject - loads of info's avaialble in Advanced Engine Technology (Heinz Heisler) and most of A.G.Bell's books, but Id suggest that small diameter (32mm) is the way forward unless youre playing with a high-revving engine

 

[arseofbox]

I doubt if Wolf Racing actually found those figures themselves (I mean, by rigorous empirical study)! Interesting that the figures don't differentiate between 2 valve and 4 valve engines, undersquare/oversquare engines, etc.

Sounds about right...Im perpetually amazed with what goes on empirically and holds water (legally!)

 

[Slosei]

Learn something new everyday
couldnt be arsed to copy and past from guy crofts site

 

[Renrut]

Looking at that page the CBR600 throttles look to be a fairly good match ~ 100 bhp bike and 37mm throttles. :yum:

So bit of room at the top end and probably a decent match for lower engine speeds.

 

[craigb244]

probably the best youll find (short of getting hold of 4 of the tiny TBs used on newer chines 125 single bikes)

it will still be like a switch. gotta remember that it might be a 100hp (your target output) BUT the bike revs to numbers a car engine can only ever dream of.
also... 37mm is much bigger then the intake ports on the head. youll be a full throttle before you reach "full throttle"