I've just read something in the latest Total Vauxhall mag. I've been thinking and it ain't something i do often. The plenum chamber is going to restrict the airflow throught to the throttle body and beyond by quite a bit. Why not just get rid of it and fabricate a funnel that curves nicely into the throttle body (I'm thinking of a c20xe).
Does anyone think this could/would work??? I'm thinking of trying it but don't want to start unless its gonna be worth it.
The intake manifold.
Making your own manifold is possible but very hard. If you find the restriction lies within the manifold, refer to acoustical engineering books to find the data you need to tune the plenum&runners.
This guy made my own manifold with 36mm runners.
To check if your runners are too small measure the bore and refer to any book on webers or such to find the _minimum_ bore you need for enough airflow at given displacement/revs. Also check that the ports in the head are big enough. The easy cure for too small runners is to fit multiple throttles that go into a manifold intended for sidedraught carbs. You still need to check the ports
My initial test would be to use the air intake pipe from my sri. Its flexible but ridged so it would slightly affect the results. I would then use something such as the rubber connection that currently exists between the AFM and Plenum Chamber to try and make a connection with the TB. Do you think there would be a benefit???
My idea did come from the Regal Kit but i don't se the point in keeping my induction and adding TB's. You might as well just get proper TB's and get the proper power.
He made it up as he was fitting the engine into a corsa so obviously couldn't use the plenum chamber. So he crafted a plate to sit on the throttle body. The plate is shaped to match the throttle body too, made out of stainless steel i believe. BTW, the corsa makes 167bhp without being chipped, but has some of that special Franczak fiddling done to it.