The intake manifold on the B21FT engine seems to be a little flat with small plenum and small runners. The throttlebody is positioned in such way that the incoming air has to turn 90deg. to flow through the intake. These features reduce airflow and performance of the engine.
The solution to that problem is an EFI intake manifold from a B23 or B230 engine. Such intake manifold has a larger plenum and equal lenght runners. There is no sharp turns that the incoming air has to flow through. More efficient airflow, more power and better economy - it is simple.
It is almost a bolt on conversion.
One of the problems is plugging the EFI holes. (Look at the pictures below).
The other problem is a TPS. The microswitch inside the TPS has to be rewired to serve the constant idle speed circuit on B21FT.
As far as parts needed, I have used the following:
- '90 intake manifold (740Turbo) including the support bracket.
- '86 throttle-body and TPS (740 Turbo).
- '86 (740turbo) intercooler to intake manifold tubing.
- combination of hoses out of a 740T and 240T to fit the constant idle speed motor.
As a recommendation, I would say go for it !
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