Rocket-Doc

iTrader: (11)

To the guru's... How would I balance multiple TBI's on an intake? Would I have to use thumb screws to adjust the idle throttle positions? I ask this since it would only be possible to hook up one IAC? I'm guessing that I would have to measure the vac. at the base of the TBI unit's, and get them to equal out?

Thanks...

Tbi-MAX

im no guru, but i would splice the wires to control both IAC, and get a MAP reading from the base of the intake like you state.... but this is just what i would do off the top of my head.. someone with more experience will chime in soon...

you may also want to lookup the EBL, as i think it controls multiple injectors, and maybe iac..

how are you tuning your dual TBI?

BMmonteSS

There is really no need to "balance" TBI like you had to do with the old multi carb setups. The ECM will inject the proper amount of fuel no matter which TB is opened up more at idle as long as they are both open. At anything past idle it won't matter at all.

Rocket-Doc

iTrader: (11)

Tbi-max, you can't splice like that.

BMonteSS, what about the A/F at idle, (lets sayt there are 2 TBI's) if the butterfly's are not at the same spot as the rear. you will be running a different A/F @ idle (for the corresponding cylinders). Granted it might try to try and balance that by adjusting the rear, but that will not help the "front cylinders". I was thinking that if I could @ idle measure the vac, could get a equal baseline, so all cylinders would be equal.

Granted you wouldn't have to balance the TBI's usually, but that is if they are hooked up will all sensors working, and they won't.

Fast355

iTrader: (2)

Actually the Crossfire setup ran TWO IAC units wired in parallel. That is how I setup a dual TBI 305 is in parallel. It worked well.

Tbi-MAX

i know a thing or 2 about wiring, and i don't see anything wrong with wiring it in parallel.. both will be commanded at the same time, and both will do what is commanded.. im sure the pcm sends a strong enuff voltage/signal to power both..

don'tseries them, but parallel them..

Rocket-Doc

iTrader: (11)

Crap your right, for some reason I was thinking TPS, not IAC. I guess my question is... take the IAC's out of the equation. What is going to guarantee me that the flow through a closed TBI is going to be the same as the other? IE... if one TBI unit does not close exactly like the other one, the A/F for that section of the manifold will not be like the others...

The reason I am asking is I'm trying to fabricate up a Tripower TBI setup. That is why I was asking about the baseline. I need to make sure at idle, that they are flowing all the same. example... just using genaric numbers

TBI #1..........TBI #2..........TBI#3
...20................28................18 not equal flow
...15................15................15 + equal IAC adjustment
----------------------------------------------------------------
...35................43................33 STILL FLOW NOT EQUAL ACROSS BANKS, CAUSING HP ISSUES

Ronny

iTrader: (1)

You may want to look up crossfire forum on the procedure to balance TB's... I used a simple vac gauge on each TB. Also I have used on MCYC applications an Edelbrock devise that measure vac with beads in a glass tube that shows amount of vacuum. Years back i had a slick series of (24 inch high) tubes with mercury in them that was extemely accurrate for multiple carbs. As was stated if they are feeding a common plenum it is not all that critical.

Olav

Use a balancing instrument for motorbikes. You have to balance then. When I was working with bikes, Honda,Suzuki,Thriumph and Ducati. We ALWAYS balanced them on their main/ big service. My own bike a Thriumph Daytona 955cc must be balanced every 24000km. If not it runs bad and idles like a 2 stroke engine... You can use vacum gauges or buy a cheap instrument that you hook uo to the intake (under the throttle blades).

I have this one:http://www.carbtune.com/

icarus402001

Look for a differential water manometer. That will be your instrument of choice.