45 replies to this topic

[Blitzkrieg]

Ok, so once I get my new stock carb I can do this mod and literally remove that black box? what about the wires and such going to it?

[1stGenRex]

Ok, so once I get my new stock carb I can do this mod and literally remove that black box? what about the wires and such going to it?

<{POST_SNAPBACK}>

read the entire thread and then search for Devac

[WickedClown]

thanks for the great write up im in the process of attempting to devac my civic seems quite daunting im glad my car was built in japan there is no way near as much vacuum lines as what the americans have
i have been quoting up vacuum plugs to internal job cards at work hehe they will never no i love bmw
after i do the devac i might try that mod however i think a weber set up sounds better we will so how my funds are going

[stevo911_]

could you run the vac advance on the dizzy to the same spot you're attaching the vacuum line on the carb for the carb mod to essentially lock your dizzy advanced, just by vacuum, or would that not work?

[crazi-85crx]

could you run the vac advance on the dizzy to the same spot you're attaching the vacuum line on the carb for the carb mod to essentially lock your dizzy advanced, just by vacuum, or would that not work?

<{POST_SNAPBACK}>

I don't think that would work. You'll need to open it up and tack it in place at full-advance.

[stevo911_]

blast, it was worth throwing out there, just figured with gutting the black box and doing eldo's mod it might be a good place to route it

[Surestick]

could you run the vac advance on the dizzy to the same spot you're attaching the vacuum line on the carb for the carb mod to essentially lock your dizzy advanced, just by vacuum, or would that not work?

Nope.
Here's the reason:
There are two types of vacuum on a carbed car, manifold vacuum & ported vacuum. They are essentialy the opposite of each other.
Manifold vacuum is the air pressure in the intake manifold (downstream of the throttle plate) & is more or less proportional to throttle position (a closed throttle = high manifold vacuum, WOT = low manifold vacuum) this is the vacuum signal that the vacuum advance needs.
Ported vacuum is taken from somewhere in the carb venturies (upstream of the throttle plate) and is proportional to airspeed though the carb throat (which is a function of throttle position & RPM). The higher the airspeed through the carb throat the more vacuum is produced by the venturie. Ported vacuum is used to operate the vacuum secondaries.

[DarkHand]

Manifold vacuum is the air pressure in the intake manifold (downstream of the throttle plate) & is more or less proportional to throttle position (a closed throttle = high manifold vacuum, WOT = low manifold vacuum) this is the vacuum signal that the vacuum advance needs.

You're correct as far as the vacuum descriptions go, but the distributor in fact needs ported vacuum to operate. As RPMs increase, the distributor needs more and more advance. This is done partly by the centrifugal weights in the distributor, and partly by the distributor diaphragm. The more vacuum on the diaphragm, the more advance. Manifold vacuum decreases as RPMs go up as you said, which is the opposite of what the distributor needs. Ported vacuum is needed in order to put more vacuum on the diaphragm as the RPMs increase to provide more advance.

Edited by DarkHand, 05 July 2006 - 12:11 PM.

[justblackwell]

I notice that all you guys keep talking about doing these mods to Canadian carbs. What about doing this mod to a US carb. I already did the devac. I tried to hook mine up the way eldo showed, but i don't think mine is working. It is a CVCC carb also. I am fixing to put a 85 DX engine in though. Will these mods work on it?

[crazi-85crx]

I notice that all you guys keep talking about doing these mods to Canadian carbs.  What about doing this mod to a US carb.  I already did the devac.  I tried to hook mine up the way eldo showed, but i don't think mine is working.  It is a CVCC carb also.  I am fixing to put a 85 DX engine in though.  Will these mods work on it?

<{POST_SNAPBACK}>

Sorry, it doesn't work for the US carbs. However, I remember reading on here something for the US carbs that is similar to this mod... check through the FAQ and Carb section.

edit: check this out http://www.redpepper...anatic/album08/

[1stGenRex]

does anyone now what the black box does?

<{POST_SNAPBACK}>

you get cable for free!

WHAT ARE YOU TALKING ABOUT!?!?!

[crazi-85crx]

The vacuum box on the top left of the firewall.

[1stGenRex]

activates teh VTEC

maybe even i-VTEC

[chedda_j]

holy shit man thanks for the usless info what other black box has been talked about in this thread readman read.

<{POST_SNAPBACK}>

the black box is just an electronically controlled emissions box that....basically does nothing. haha im sorry but im from canada *three hoses*

[jfodor]

i still dont' know what's in that black box. i've opened it up and read the hayes and chiton manuals and there's nothing in those that explains what the 2 pieces in there do.

any one know?