So after much porting work with fuel injected VW A1 sytle intake manifolds and various air flow tests it was time to how these ported intake manifolds performed on the dyno.
You can find more about the porting and testing process on the A1 porting and testing page found here on the scientific rabbit. NOTE: A1 Fuel Injected VW cars at 1978 -1984 Rabbit, Jetta, Scirocco, Caddy, Cabrolet, Rabbit GTI, Jetta GLI The Dyno tests were done by a fellow vwvortex user , I offered a ported intake manifold to VW Rabbit owner in exchange for a full chassis dyno done to the car before they installed the manifold and then after the installation. Then Share the results with the community.
The rules of this exchange were simple :
As Noted in Greg Raven's "VW Performance Handbook" the intake manifold is the biggest single intake restriction of the engine setup.
For the test car setup and results read on.. The test car is a VW Rabbit with a 84 GTI motor. The GTI motor engine code is JH, it has a solid lifter 8 valve head, with big valves. 40 mm intake valves and 36(or 38 ?) mm exhaust valves. The car owners website is not entirely up to date, but you get the idea.
This particular motor has a few modifications already;
Dyno Charts combined for easy comparison
Further intake testing and development has lead to a VW MK1 golf / rabbit scirocco (76 - 84) 8 valve ported intake manifold that can flow %25 more air than stock. Granted going from a 10% more air low to %25 is like 3 X the amount of work. But the end result is a manifold that looks stock and also meets SCCA GP - FP racing specs.
Notice the welding.. the badge of honor For simplicity sake I'll refer to the ported intake manifolds in stages.
Stage I = 10% more flow than stock, gasket port matched, balanced flow, for Street all motor applications
Stage 3 = 25% more flow than stock, gasket port matched, balanced flow, for Racing and Boosted applications.
So the question now is how well does the intake manifold work on the engine, was the extra work worth it?
Results from SCCA GP Racing engine setup
Chuck Mathis Racing was looking for some more Go in their winning SCCA GP class rabbit '07 and it seems that a race engine could make use of the extra air flow. So why not test the stage 3 intake on a race car? I ended up sending Chuck the ported intake from my engine to test since I wasn't using it due to a engine rebuild. Below you'll find the image of the dyno chart with two runs. Blue lines on the graph show last years racing setup, red lines show the scientific rabbit stage 3 run results. Unfortunately the ports on my manifold didn't exactly match the race head. But those are good results anyway! Chuck liked how well the intake setup worked that he has requested a stage 3 ported intake manifold that matches the ports on the race head. The Stage III intake manifold was used in the 2007 National runoffs. Congratulations Mathis Racing for a excellent second place!
Additional Testing: A Rabbit owner with a supercharger was looking to brake the 200 Wheel HP barrier a short while ago. I suggested a Stage III intake to increase flow and make the most of the boost being run. The Basics of the supercharged VW Rabbit: 2.0 ABA block EuroSpec head with stock size valves Megasquirt Lysholm twinscrew supercharger high boost, light weight pulleys, Performance cam ,Stage III ported intake manifold. and Lots of tuning Here is the dyno from the latest tuning session: (needless to say this is a powerful combination!)