Turbo
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Boost Mods using air bleed:
Category: Engine Control
The wastegates are mechanically set to 10 PSI on all 2.3 EFI turbos.
A boost bleed line is already installed on the cars equipped with BCS (boost Control Solenoids). It is the solenoid on the fender, in-line with hoses that BYPASS some of the pressure signal AWAY from the wastegate.
The boost solenoid only OPENS the valve when commanded by the EEC. The conditions must be right for MORE boost, not less. Automatic XRs never activate the solenoid.
I was tinkering with the wastegate bleed and I found that an insulated butt splice, for connecting wires together, made a perfectly sized bleed orifice and hose connector. The yellow butt splice for 12 gauge electrical wiring, available at many department stores, Wal Mart, KMart etc., that I installed, gave me exactly 14 PSI at full throttle. It also allowed significantly more boost at less than half throttle This was on an automatic XR4ti.
To modify,
Also, I used rubber fuel line to replace the stock hoses, and worm drive clamps. The hose lengths were about as long as stock going over to the solenoid. I left the solenoid connected to it's wiring to prevent any possible confusion for the EEC-IV.
Now the car will pull 10 PSI at around 1/3rd throttle. The driveability is much better, and there's rarely a need to floor it in normal driving. My car didn't ping, or pull back the timing, at this boost level with 93 octane gas.
The "butt splice" is an electrical connector that you crimp the ends of two wires together with. A 12 gauge wire fits in each end. It is yellow. Buy one and put it in-line. It's way easier than adjusting a valve. As to orifice size, it's slightly larger than a 12 gauge wire. Cheaper too.
On 85 amd up turbo models, the T on the compressor housing has an orifice sized to only allow about 15-18 PSI of boost, even with the bypass hose routed straight from the T to the wastegate. To get more, you will need to drill out the orifice. Proceed slowly, a small increase in size makes a big difference in boost level. Go too far nad you will need to install a valve inline to limit it.
On 84 SVOs, the orifice is big, and you can get tons o' boost. Harder to regulate.