71 chevy

iTrader: (18)

I wanted the formed one because its available in stainless,and cheaper, but I noticed they are both 5 inches but you can cut approx two inches off the welded one without reducing the diameter.the formed one looks like it gets small real quick if you cut it

coneeng

If you are cutting the collector shorter from the outlet end the diameter actually gets larger since it is a conical shape. Unfortunately on a 2-1 collector the outlet begins to oval when you cut it shorter since the collector is not square like it would be on a 4-1 collector.

If your cut the collector shorter on the inlet side on a conically formed collector then you reduce the inlet tubing diameter.

A bend/cut/weld collector can cut down from the outlet but to a lesser extent depending on the bend angle since at some point you will run into the individual tubes and greatly reduce the merge point. The less the bend angle the less it can be cut before running out of merge (I had to draw that on a piece of paper to be sure!). The inlet side can only be cut so much until you remove the expanded slip segment. It can only be re-expanded if there is remaining straight section before the bend.

71 chevy

iTrader: (18)

hi, I would suggest you put the information about the slip fit on your website and ask your dealers to do the same. as I said, I wanted to buy the coneeng piece, as it could be got in chrome and its less expensive than the welded merge, but the one thing that stopped me was that it was not a slip fit.
http://www.stevesnovasite.com/forums...4&postcount=52
now I find out it is that would have changed things. a slip fit can make life a lot easier when fitting and I think this is information that should be out there clearly stated.

also, I think that the less the bend angle, the MORE it can be cut before it runs out of inlet pipe. can you explain your position more clearly?



finally, it would be AWESOME if you guys would design a merge for us turbo guys. I think a dual 2.5"inlet to t4 outlet, with a 3" or less total lengh,slip fit ends in stainless steel would be a hot seller.

coneeng

Well I typed up a detailed response but took too long and got logged out! Hopefully I will remember everything!

Our collectors were primarily designed as a weld-on collector but can be used as a slip-on with some additional fabrication work. You move up to the next larger primary diameter for the collector base. Then use 18g tubing to weld into the collector thereby creating the slip fit. However, I don’t normally recommend this process on a turbo collector since they will not seal perfectly. If I needed flexibility for fitment I would prefer to find a way to use v-band clamps either upstream and/or downstream if possible. And fashioning these slips works better on a 4-1 than on a 2-1 since on a 2-1 the tubes are not always in close proximity on a 2-1 but it is a requirement on our collector.

Most folks don’t utilize the tuning capability of a slip-on collector (adding or subtracting length and diameter based on conditions) and find more drawbacks (leaking, cost, carbon stains) with a slip-on than they find advantages. So we have chosen to work on weld-on collectors. There are a lot of slip-ons on the market but as far as we know, we are the only fully sealing weld-on merge collector.

Here’s my thinking on the why area decreases when cutting down the bent/cut/weld (bcw) merge collector, especially a 2-1. As you shorten the collector from the outlet end you get closer to the tube junction (merge). At some point you will reach it and then the lower you cut the greater merge section is exposed and the less free AREA you have available (the obstruction in the center gets larger the farther down you go), regardless of whether you have more outside diameter freed up. The greater the bend angle, the farther apart the primary tubes and the shallower the distance between the merge and the collector outlet, therefore the less it can be cut down before the outlet becomes occluded.

As to the final collector you mentioned, it would be very problematic to build. As a bcw collector, the radius of the bend in relation to the tube diameter would be tiny and very difficult to bend. And if the overall length of the collector were that short you couldn’t get any straight tube in order to fab the slip segment. But I will qualify my opinion by saying that I am not an expert in that style of collector and I could be mistaken.

As far as building that dimension in our style of collector, the angle of the cone (the starting point of the collector) is too steep at the short of a length and would not roll. I really don't see a production solution, if you need something at that dimension you're pretty much looking at one-off hand fabrication.

Also the length of the merge is very short and would probably result in a substantial amount of backpressure in the collector. Even though backpressure is not as big on an issue with a turbo, it does impede velocity and velocity is critical!

bad6as

iTrader: (17)

so your saying not sut cut it down as it gives it more room to "merge" so more merge area the better the flow?

coneeng

Not exactly. In a perfect world everything would magically work from the scientific/engineering side into the real world we actually have to live in.

Every exhaust system is a series of compromises. You are often forced to do something even if it isn't the best absolute answer. That said, I was giving you some pros and cons of the different choices you mentioned. By choosing one of those options can cause additional conflicts in another area. Only you can decide which really works for you.

For instance, gaining the flexibility of the slip-on collector can lead to pressure leaks. Cutting the collector down too far can lead to obstructions within the collector. Whether it is too much for your application, that's where header building moves from a science into an art since each application can be significantly different.