I have seen this done quite a few times and it has been in alot of magazines but is it worth the effort to do it. The closest shop to me that has a mandrel bender is roughly a 7 hour drive so that is out of the question.

I am talking of course about making bends for your intake, IC, and even some cooling bits out of a strait piece of pipe by cutting it at varying angles. The reason i ask is because I am going to be fabbing up my new fmic and have been looking at a few options, I can either buy a premade kit(kinda lame but cost effective) I can buy som U bends in the sizes I need and cut and weld the all the pieces together to make it work, or I can buy the dia i need and makes some bends out of it, I know its not very time friendly or cost effective but I think it would be a good project to keep me busy.

MY question for this awesome new subforum is how do you figure up all the different angles that need to be cut. Trial and error?, or is there a better way. I am going to be making my piping setup out of aluminum so I would like to not make mistake after mistake to get just one bend done lol.

For those wondering WTF I am talking about

 

Pie cuts.

 

Math Sir

 

The thing is, those flow terribly compared to proper bends. If you are careful with your welding to avoid excess penetration and can get inside and grind them smooth then it's probably tolerable. But a far better solution is to buy pre-cast els and cut them to the angle you need.

You can get "ornamental" stainless and aluminum els from most tubing suppliers. They are in tubing sizes and are thin walled.

They look like this:

 

they do that for real tight radius bends...........personally, I would spend the money on a donut. That's what I had to use on my 5" downpipe

http://www.deezperformance.com/CatalogDonuts.pdf

 

I bought (embarassed to say) a piping kit from E-bizzle. I was able to pic the sizes and bends that I wanted and then I started cutting & welding from there. The material was 2mm thick and had the most flimsy chrome coating on it that i had ever seen which was actually a good thing. The material welded just fine which was what I was concerned about. I thought about going through Burns Stainless or some other well known and ridiculously expensive supplier but decided in the end that the cost wasn't worth a zero addition benefit. Check out some of the piping kits, the are so SO much better than pie cuts or non mandrel bent ****. The only time I would do pie cuts like that would be on a cooling system. Certainly not an exhaust or an intake.

 

Wow those prices beat the hell out of the local suppliers around here a mild steel ubend was $35 for a 2 1/4 which is the size I am using for my IC piping.

 

I used the pie cuts for ultra tight radius bends when I couldn't find a tight mandrel bend. The pie cuts don't flow as well. When I did it, I just chose a pie angle that I liked and made a bunch of them on my chop saw (I used 10 degrees). Then, I pieced it together until it fit. The actual assembly and cutting of the pie cuts took no time, but the welding took forever. When all said and done, it was 13 feet of welding!!

 

Nice. Looks like it'd flow well. I think the trick to "pie cuts" is to use small sections. More welding, but I bet the flow gain is worth it. And damnit.......it just looks sweet when done properly! Given the price of 5" aluminum mandrel bends, it's my plan for the GT42 intake!

 

only use them when you cannot find a prebent tube with the correct diameter or bend radius. in this case we needed a 6in intake so straight tubing was only option.

 

Looks good! I don't think there's much of a flow loss, especially when using lower degree pie cuts (the more you have, the less loss you have). Reading through my Fluid Mechanics text book, you can get a cheated 45* bend (they call it a miter bend - just cut both pipes at a 22.5* angle and weld together to make a 45* bend) to outflow a mandrel with the use of fins inside the flow path to help direct the air around the corner. Perhaps if you're worried about flow loss going into the turbo (which is something to be considered), then placing a few fins on the inside walls will solve the problem.

 

Any chance you could elaborate on the usage of "fins" inside the pipe, I've got to make an intake pipe exactly like this in the near future. Not quite a miter bender but a tight pie cut anyways, and anything I can do to make it flow better would be great.