shortyboy

Mike@Lindsey, any updates on this product?

Adonay

Was this cancelled

ptuomov

Can you or someone else elaborate on exactly how much space in each direction is needed with a bellmouth that is slightly raised from the floor?

67King

Imagine an ice cream cone. If it is 1 unit in diameter, then imagine teh scoop of ice cream sitting on the top of it being 1.5 units in diameter. That is what you need. You can trig out where exactly it needs to be, as far as how far into the cone the scoop sits. More room won't hurt, but less will.

ptuomov

I've seen some CFD graphs that show the bellmouth sucking from a broad area on the side and surprisingly small distance from directly on the top.

These I think are from Blair's RET article originally. My instinct says that as long as the walls are at the zero Mach area in the below graphs, then one should be ok. But that's just instinct.

Simple straight pipe end sucks like you describe from the ice cream scoop:



Bellmouth looks a lot flatter:



If you measure from the bellmouth center, then it's maybe 1 D up and 1.5 D to the sides. Of course, if you measure from the floor, then it's about 2.5 D from up and 1.5 D to sides.

I don't know how the graph would change if we would sink the bellmouth to the floor or actually put walls around the whose thing.

67King

CFD trumps rules of thumb just about every time!!!!

xschop

I milled a couple plates to add Hayabusa ITBs to a nissan 4 banger once (NA). Looked pretty cool and woke the engine up. The guy had to weld in tubes between the plates and had trumpets on hand.

Jay Wellwood

Bump - given the recent discussion on ITBs recently...

Paulyy

i guess if you really want ITBs, you'd make them for your application.

Raceboy

It is much easier and cheaper to buy a set of suitable ITB's, also motorcycle ITB's are by far better quality than most aftermarket ones..

V2Rocket

wonder how much of the "gains" from ITBs are from matching all the runners in length so they all tune to a certain (high) rpm, rather than having mixed lengths to broaden the tuning effect...

would you rather make equal length or unequal length runners?

ITB is something i've thought about playing with, i of course have an idea to build a setup for pretty cheap with a near-limitless supply of OEM throttles in either 39 or 50mm sizes, with larger ones available from the aftermarket...into a plenum to run a MAF. but the easiest way to do it that i can come up with would likely result in a slight mismatch of one pair of cylinders in runner length.

Raceboy

Why run MAF when you have installed ITB's? I would understand if you run forced induction and then use existing MAF system, but I personally wouldn't even bother installing MAF when using ITB's. It is just another restriction and just another thing to fail... Plus MAF sensors do not like pulsing air that is present with ITB's and/or wilder cams...

gruhsy

What would you use instead of MAF? Asking cause I don't know

V2Rocket

the common plenum pre-tbs should smooth out pulses, and the MAF would make for easier tuning and idling.
plus, i already have the MAF

the sensor is so narrow that any restriction it may pose would be pretty minimal.

Raceboy

When going through hassle of installing ITB's, going some standalone would be pretty much the only reasonable way. This is purely because there is almost no OEM ECU that has proper control strategy for ITB's. Only ECU's that comes to mind is Nissan RB26DETT, BMW S engines and some others too.

MAF will not make ITB's easier to tune and with standalone using Alpha-N+load compensation (MAP hose connected before throttles) gives the best result.
But, to each their own.