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**squirrel** · August 30, 2009, 04:17 PM

Re: Exhaust tubing: "Cheating the bend"

Now that you told us, you can't do it. If no one knew, it would have been alright.

**CTX-SLPR** · August 30, 2009, 04:20 PM

Re: Exhaust tubing: "Cheating the bend"

I'm wondering about how much of a performance loss it would be, if ya'll just look at me like I'm splitting hairs... I'm going to clamp the thing in the vice and take the cutoff wheel to it!

**seanm** · August 30, 2009, 05:18 PM

Re: Exhaust tubing: "Cheating the bend"

Doubt it will be problem on anything short of an all out effort. I assume the turbo outlet is 3". The turbine outlet on the turbo in my car is 5" and Precision Turbo told me it could be stepped down to 4.5" with in a couple of feet without a loss in power.

**Caveman** · August 30, 2009, 07:32 PM

Re: Exhaust tubing: "Cheating the bend"

Don't cut all the way through... pie cut it with several slices that go 90% of the way through the tube... then just bend the tube to the curve you need, and weld the slices up.

If its coming from a tube thats straight, just do the same thing an inch or so up from where you're attaching the new tube... that'll get it pointed in the right direction.

As far as how much you're going to lose if you do it with a straight angle cut on the end of the tube, it really depends on how much angle you're introducing into the exhaust flow. A very slight angle is negligible, but the sharper it gets, the more it kills exhaust velocity.

Does that sucker have the 465 Wildcat motor?

**CTX-SLPR** · August 30, 2009, 08:05 PM

Re: Exhaust tubing: "Cheating the bend"

It used to have a 465 Wildcat in it but now it has a 4.1L Buick V6 in it with a full T-type EFI and turbo system in it. I'm building the down pipe and right now I have a stock intercooled turbo on it with a .63 Garret housing. Going to a bigger unit but still a "bolt on" intercooled T-type turbo later so 3in is the largest tubing that will fit.

I'm cheating a 90deg bend section a bit tighter is I guess what I'm doing. Its a 4.5in radius 3in tube so I guess after 6ft of mandrel bends (sweeping 180 and a 45 bend) and straight tube it's not going to make a big difference. Probably something like a 15deg angle on the cut.

**BlackoutSteve** · August 31, 2009, 02:40 AM

Re: Exhaust tubing: "Cheating the bend"

How about using two 90 degree bends and joining them.. from Burns Stainless?
The CLR (CenterLineRadius) on their sort-leg 3" 90s are only 3". That's pretty damn tight. :o

304 SS http://www.burnsstainless.com/cgi-bi...-300-30-16-304

321 SS http://www.burnsstainless.com/cgi-bi...-300-30-16-321

I assume you are using stainless on a turbo application.. Yeah?

**SuperBuickGuy** · August 31, 2009, 05:33 AM

Re: Exhaust tubing: "Cheating the bend"

15 degree - probably not, but is that 15 degrees more then 90 degrees (for 105 degree bend)? every 90 degree bend is like adding 10 feet of linear pipe.... 15 degrees? I don't know if it would make a difference... probably the dimple you made would create more backpressure then the slight additional bend.
Another point someone made to me when I did my exhaust, the further you get from the motor, the cooler the exhaust is and the less volume the exhaust needs - he analogized to the idea of running open headers in a large, industrial building... yes, there is some pressure change because the space is enclosed, however, in the overall scheme of things, it doesn't really make a difference given the volume of space the exhaust is going into.
and lastly, on my Buick I have dual 3" exhaust through the mufflers, then 2.5 over the axle.... I dynoed the motor before and after the addition of the 2.5" exhaust pipes and saw zero difference.

**CTX-SLPR** · August 31, 2009, 05:45 AM

Re: Exhaust tubing: "Cheating the bend"

Originally posted by BlackoutSteve

How about using two 90 degree bends and joining them.. from Burns Stainless?
The CLR (CenterLineRadius) on their sort-leg 3" 90s are only 3". That's pretty damn tight. :o

304 SS http://www.burnsstainless.com/cgi-bi...-300-30-16-304

321 SS http://www.burnsstainless.com/cgi-bi...-300-30-16-321

I assume you are using stainless on a turbo application.. Yeah?

Mild steel currently. Too much expense for something that I'm not even sure is pemenant due to things like the rearaxle design and such. I do have a stash of 3in mandrel stainless for when I'm happy with the design of the system. Largest reason for the mild steel is the cost of oval tubing I need for going over the rear axle.

Got to get to work, will post more on it there.

**CTX-SLPR** · August 31, 2009, 08:17 AM

Re: Exhaust tubing: "Cheating the bend"

Ok, here's what I'm doing. The pipe goes under the frame rail of the X-frame right behind the front tire. I have the downpipe running pretty close to the frame to leave me room to mount the wastegate to the cross over tube down there. It needs to make a 90 deb bend under the rail then another 90 in a different plane to start running along the rail. In practice the bends cut by a chop saw aren't perfect and I've ended up with the pipe turned slightly and barely out of alignment. The solution I see is to cut the 90 back slightly since it now slightly curves up instead of just straight out, and then cheat a bit so that the attached 90 in a different plane now lies closer to the frame rail and higher off the ground.
The downpipe makes a huge 180deg bend about 2in after the turbo, it's really gentle though on a 4.5in radius and has a 4in straight section in the middle. it then has another short section of straight then a 45 deg to bend it down and then around 2ft of straight pipe before another set of 2 90's in 2 planes. I'm really begining to think I'm splitting hairs here and making it fit will be far more benificial than trying to not cheat the bend and having it hange down more.

**squirrel** · August 31, 2009, 09:37 AM

Re: Exhaust tubing: "Cheating the bend"

You're gonna need pictures, I can't keep all that straight in my head

**CTX-SLPR** · August 31, 2009, 04:25 PM

Re: Exhaust tubing: "Cheating the bend"

Ok, here we go

First off, here are the 2 engines. Green tired Nailhead and the black and silver new Turbo6

What the Turbo6 looks like in the engine bay, its amazingly tight in there

Alright now to the downpipe:
Up top

Down the tube to the frame rail past the O2 sensor

Around the frame

And were it currently ends

Here is what I want to do

something like that relation, maybe a bit shallower

**seanm** · September 1, 2009, 09:52 AM

Re: Exhaust tubing: "Cheating the bend"

Not a problem, IMO. You could expand the end of the straight section and it would allow some room to cheat the angle also.

**CTX-SLPR** · September 1, 2009, 10:10 AM

Re: Exhaust tubing: "Cheating the bend"

Which straight section? There already is a joint halfway down the leg past the frame since I'm probably going to lock the relationship between the tube that goes under the frame to the rail so it doesn't rattle. Also I want to be able to disassemble the exhaust in pieces. The current section will end at the back end of the resonator in the middle of the 'X' and then there will be a section back over the axle and then the tail pipe unit with an F-body 3in inlet dual 2.5in outlet muffler and stainless tail pipes.

**min301** · September 1, 2009, 10:17 AM

Re: Exhaust tubing: "Cheating the bend"

How about running some 3" stainless flex joints,
they are available in different sizes, and lengths.

That would allow the rearward section of exhaust
to be solidly mounted(w/ rubber biscuits), and allow
the front section to move.

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Exhaust tubing: "Cheating the bend"

Exhaust tubing: "Cheating the bend"

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