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VW MK1 stage 1 ported intake manifold

Why the VW MK1(1976-1984) intake manifolds need porting:

  1. As Noted in Greg Raven's "VW Performance Handbook" the intake manifold is the biggest single intake restriction of the engine setup.
  2. The more air each induction cycle can feed the engine the more power it will make.  Stage I porting the intake manifole can feed the engine 10% more air than a stock non ported one.
  3. Equal flow between each runner ensures that each cylinder is receicing the same volume of air. In the air flow tests below you can see that the stock MK1 intake manifolds air flow between runner ports is not consistent. Consistency is important with CIS fueled cars, as the injection system can't tell how much fuel each cylinder needs - it can only tell how much all cylinders needs together. 
  4. Throttle body mount is opened up so larger 52mm throttle body can be installed(Common swap from A2, Audi's,Neuspeed cars)
  5. Dyno test results proven results Stage 1 Dyno Tests Page


VW MK1(1976-1984) Rabbit Scirocco fuel injected air flow test results:

Test Equipment - 5HP manometer
Flow tests were all run on same setup with the same room temperature, and run more than once to verify results. Test results present pressure /flow comparisons between intake manifolds useful for shoing consistent differences in flow between runners under test. To best simulate real world setups a stock throttle body, intake boot and zip tube are used.  Air is fed into the zip tube, differential air pressure is tested at the throttle body.  Each runner is tested individually.  Runners not under test are internally blocked off.

Runner Number   Stock Air Flow Ported Air Flow
1   10” 9”
2   9.5” 9”
3   9.5” 9”
4   10” 9”


Stage 1 Ported VW GTI intake manifold with two plenum vacuum ports

  Stage 1 Ported VW intake manifold

Stage 1 Ported VW intake manifold with one plenum vacuum port

Stage 1 Ported VW intake manifold single port

 Throttle body mound opened up to allow the use of the larger big bore 52mm (neuspeed, A2, Audi) throttle body.

Ported throttle body mount

Stage I (7 HP gain) - For street applications. for best results, G cam or larger, dual outlet manifold or headers recommended. No loss of low end power, good mid-range gains. 10% more flow over stock. 7 HP gains depending of other modifications. Ported to accept 52mm big bore throttle body.

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