HOW TO: AE101 ABV Bypass mod (two images, 312KB)

[pidge]

Warning! Acronyms galore! Just look at the piccies for the short explanation on how too. Read the text for the long winded one...

I finally bothered to have a go at this to see if it made any difference on a stock AE101 4AGZE - Seat-of-the-pants dyno says no, but it does peak at about 9.5 psi of boost. I may not have a peak boost reading for a before becase I either didn't try hard enough to see if it would boost over 8psi, or it does just boost to 8psi. The 9.5psi is somewhere at the top end - I'm not sure exactly where, becuase I was more interested in watching where I was going at the time with the occasional glance at the boost gauge to check.

Any way, this is what you should see under the bonnet of a AE101 with a stock late model 4AGZE ( '91 - '95):



This is looking from the RHS of the car. The three vacuum tubes that are behind the throttle inlet pipe are (from left to right):

1.vacuum feed to Inlet Bypass Valve diaphram (IBVD)
2. vacuum feed from supercharger gear casing (I think!) (this is used to purge the SC gear casing of boost / vacuum, controlled by another VSV)
3. vacuum feed from Inlet Manifold (IM)

The vacuum feed to IBVD line is normally switched through a vacuum solenoid valve (VSV) to a feed from the Supercharger Inlet Manifold (SIM). If the VSV is opened, vacuum is applied to the IBVD, which opens the IBV, allowing the boost in the IM to recirculate back into the SIM. The ECU controls the VSV to keep the boost at 8psi.

The IM vacuum line goes to a VSV (vacuum solenoid valve) and then back to the Fuel Rail pressure regulator. This IM Vacuum line is the one that the IBVD vacuum line needs to be connected to force the Inlet bypass valve to stay closed, by having boost on the diaphram instead of vacuum.

You will need an appropriately sized vacuum line T ($6.75 or so from Ri^hepco) and two short pieces of vacuum line.

See the second piccy to see what to do:



One of the short pieces is used to block off the metal vaccum line to the IBVD. The other is used to go from the T-piece to the metal vaccum line to the VSV from the IM. The vacuum lines to the IBVS and from the IM attach to the other two ends of the T.


edit - edit title (whoops!)

[FLAWLES]

aaaaaarrrr the abv mod

i have thereoys on this
one theroy is
it dosnt really work that well

second it only works sometimes"dont no y " but when it does its hold the freek on

[pidge]

It's only needed when you've put an overdrive pulley on - otherwise you just get 8psi of boost, but it gets there faster.

The late 4AGZE had a smaller SC pulley, which is supposed to give 10psi or so - but the ECU controls that back down to 8psi using the ABV VSV.

[beeker]

thx guys