What does everyone think about sheet metal intake manifolds? Apparently they're significantly cheaper, and after looking at them, look like they would be just as effective as a cast manifold. Can anyone give me a run-down as far as the pros/cons?

The reason I ask is I'll probably need to fab a custom intake manifold, but don't want to pay to get a one-off casting done.

Blake

 

A carbon fiber intake manifold would be nice...

 

LOL! You're not much help...

Blake

 

Blake- I think that for the most part you are definitely on the right track. If you are doing a one-off manifold it wouldn't be cost efficient for it to be cast. I think that if you have a very good welder you could probably fabricate a good sheet metal intake manifold. I think that cast manifolds are a lot stronger in terms of maybe being able to support the weight of a supercharger and any type of stress that it would induce into the manifold. They also for the most part would have a greater ability to absorb and retain heat. With all that being considered I think that you could design a pretty good sheet metal manifold with sufficient strentgth and heat capacity to do what you want to do. There are really tons of other factors on designing a manifold, but in comparing sheet metal to casting I believe that those are the major differences. I believe that this guy had success with a sheet metal intake when he added a supercharge to a newer model Mroadster. It may help you out.

 

Sorry Blake.
Here is the link :http://www.bimmerforums.com/forum/showthre...25&pagenumber=5

 

Thanks, I'll take a look at the link.

Honestly, the reason I was surprised when looking at these intakes is cause I didn't realize sheet metal can be pretty damn thick. I now realize that a lot more aftermarket intakes are actually made from sheet metal. So judging by the thickness, I don't know if there's gonna be a problem supporting any kind of weight.

Another thing I was wondering is the design of the manifold. I was thinking about keeping the runners the same length, but I was reading out how different plenum capacities can make a difference in power, at least for NA engines. Do factors such as plenum capacity, tapering, etc, make a difference with FI?

Blake

 

This is right up Shawn's alley (Ultimate Lurker). But yes, those factors would make a difference with forced induction, just as they do with normal aspiration.

But I will leave it up to UL to set the record straight here.

 

Wonder if you could cast an intake manifold out of the same stuff that log turbo manifolds are made of ala speedcraft. I would imagine it would be a bit more sturdy

 

I'm not sure what process they use for log turbo manifolds, but if it involves a mold, then it's probably going to be a lot (IE, $1000+). And looking at the manifolds I've seen, I think it could stand it. I'll talk to some people this next week. Now I just need UL to chime in with the basics of intake manifold design.

Also, looking at the JR supercharger setup for Civics, etc, it seems that they have a very small plenum. Seeing as how the supercharger is making positive pressure in the manifold, tuning the manifold wouldn't be near as important as with an NA engine, in which there is negative pressure in the manifold.

Blake

 

If you are talking about a prototype, sheet metal is OK. But I thought you wanted to produce the things. Once you head into production, you'll want a casting since the cost will be cheaper than the labor associated with sheet metal.

The intake should be tuned in FI apps. Everything is more critical in FI as compared to NA.