Been a while since I started a new thread, but I need some opinions on my intake plenum adapter I designed. This plenum will be used to mount a stock 2nd gen NA throttle body to my Jay-Tech intake manifold which mounts a carb. I have attached a screenshot of the 3d model I made in Autodesk Inventor 10. I figure the plenum should work well, but I could be wrong. This is in preparation of going fuel injection using a megasquirt computer and a stock S4 turbo on the car.

To sum up the system overall, it will be a megasquirt standalone running the fuel injection, stockish ignition system with distributor locked, S4 turbo with ported waste gate, custom plenum to mount stock 2nd gen NA throttle body, primary injectors mounted in stock position in center iron (S4 13B used here, most likely 550cc turbo injectors), custom mods to intake manifold to mount secondary injectors (again 550cc turbo injectors). The biggest question I have besides the plenum working well would be about fuel pressure. Would a 45psi holley external FI pump be enough pressure or should I upgrade to the larger 70psi one.

 

If you are going MS, why not use a 2nd Gen Leading and Trailing coils with a CAS?
Better performance since you are using a ECU anyway.
Your plenum adapter idea is a good way for 12a folks to upgrade to EFI and still use the same 12a intake manifold and just add a spacer plate with weld on injector bungs inplace of the carb.

 

Looking good. Do you have a source to make the part? have you designed for fabricated or composite?

-billy

 

This will be a one off custom made part from sheet metal most likely. There are things like this already made by at least one company that I know of, mabey more, but those are all expensive parts. I figure I should be able to make this for about $30 if I cut everything myself from raw metal. The biggest thing is the 90* itself, not the flanges. There are 2 ways I can do it. Rounded edges like in the pic above, or I can go with squared off edges like in the pic I attached here. The rounded edges will obviously give better flow, but I don't think there will be any real bad effects from using squared off edges. The reason I question which design I should use is the ease of fabrication. To fab up the sheet metal for the first design would take a lot of time to make the rounded edges, the squared edges don't take nearly as much work to make, basically 4 pieces of sheet metal as compared to at least 8 formed pieces for the other one.

As for using the stock ignition over a 2nd gen CAS and coils, the megasquirt version I want to use doesn't have the ignition control in it, and to get the ignition control to work properly would take some work. Its easier to just use the fuel only version of megasquirt and a stock ignition with a TT box on a 2nd gen leading coil with stock trailing ignition. Injectors are either going to be the 2nd gen turbo ones or the 680's from a GSL-SE. 4 of those should definately give me plenty of fuel.

BTW, this is in no way a professional design. Its just a basic 3d model from 3 sketches, 1 of each flange and the basic plenum design. So basically its 3 parts, the 2 flanges and the plenum itself. Everything was designed to scale though from exact measurements from an actual throttle body and manifold.

 

I was just thinking about this, instead of using stock injector bungs in the center iron, I could get an aluminum separated 4 barrel carb spacer and weld in 4 bung into that, 1 for each barrel. That would be easier than welding bungs into the intake manifold, but it does present some other problems with custom fuel rails and whatnot. Something to think about.

 

That is where my question came from. The rounded edges would make fab a bit more a a nightmare. Cool sound like you have it covered. I would love to see the outcome.

I can't locate my Corky Bell book at the moment but IIRC flow is not as much concern when in a boosted application.

-billy

 

Thanks billy. I've been thinking this one out a bit at least. I based my design on a couple production models I've seen. Overall it should turn out pretty good.

As far as flow, as far as I know its not as important in a boosted application. Forcing the air in under pressure negates some of the flow caracteristics that would be present in non-boosted applications.

 

If you're already using the Jay-Tech - then you're halfway there. A 2nd Gen TB is going to be a bottleneck for big power.

My new Engine uses a Jay-Tech and This throttlebody.

 

That looks expensive.

 

i have a friend here in savannah that has that tb on a turboed franken-motor... it is awsume!!! i think the tb is mounted on a rb intake currently, but will soon be on a jaytech...

btw i would sure like to have one of those jayteck intakes if someone has one laying around they want to part with...

 

I'd love to go with one of those throttle bodies, but I can't get by the price, especially since I plan on making no more than 300hp, if that with a stock S4 turbo. I think the stock S4 NA throttle body should work fine with a little bit of porting and general cleaning up. That coupled with a nice FMIC and various other pieces should net me about 250hp at 10-12psi I think. Its an S4 NA 6 port motor btw.