Designing an exhaust system 1

[MStiller]

As I mentioned in a previous thread, I'm in charge of designing the exhaust system for the vehicle my company is building. Are there any kits available that you can buy that make designing a custom header/exhaust system easier, or is it just a matter of going to home depot and buying a whole bunch of pvc?

 

[reidh]

I have never seen an exhaust system made of PVC, or with any standard plumbing fittings for that matter.

I would start with a software program such as Flowmaster (not the same company that makes after market exhaust systems) to start the design process, of course after all of your requirements have been defined.

-Reidh

 

[patprimmer]

You can work out an exhaust layout for fit with PVC pipe, but steel or copper pipe makes more realistic prototypes. You can even test run the copper ones for a while. It is expensive, but easy to work.

A lot depends on how you intend making the final product.

The methods are:-

A pipe bender, but these cause some crush or restriction at the bends.

Sand pack then heat and bend the pipes. Nice job but requires a very skilled craftsman and is hard to reproduce.

Various mandrel bends and straight sections cut and welded. These can be semi automated for larger scale production, but they still require good skills. They give the best end result if the cuts and fit are precise and the welds good.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[MStiller]

Maybe I should have explained a bit better. I know you wouldnt use PVC for the actual exhaust, I'm just talking about for a mockup to make sure we route the exhaust tubes in the right places. The actual exhaust will be made of stainless or titanium

 

[GregLocock]

We skip plastic and go straight to steel pipe, but ours are usually done on CAD anyway

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[sbmar]

I do not know if this link will help, but possibly you may glean a bit form it. We have beed designing and building marine exhaust systems for well over 20 years and have learned a bit our self that we like to share...

http://sbmar.com/Articles/Exhaust_Introduction.cfm

Good readin', I hope....


Tony



Tony Athens

http://www.sbmar.com

 

[MikeHalloran]

PVC drain pipe makes excellent prototypes for marine exhaust systems.

I've also seen them made of stovepipe, paper, plywood, sticks glued together... and of course the remains of the pipe that failed or didn't fit right or didn't work right.




Mike Halloran
Pembroke Pines, FL, USA

 

[IceStationZebra]

I know that several of the hot rod header manufacturers sell "bends" cheap, which are mistakes that you buy by the box and cut to make your custom header. Many of them also sell precut flanges, but this would only apply to popular car engines. ISZ

 

[GregLocock]

That sounds like a very sensible approach.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[MStiller]

Thank you all for the assistance. I think we're going to try PVC, just because we have a really REALLY cramped engine compartment, and doing it from scratch in CAD would probably end up taking us more time than doing it with PVC and then modeling it.

 

[Bribyk]

If it's a tight header you're designing, there's a good hands-on method I've recently come across.

Use 3/8" copper tubing with one end fastened to a wood exhaust flange mockup, and a tube bender (use radius of final pipe bends and mark your bend start/end points with a Sharpie) to rough in your system. Then cut round wood (or similar) discs to the outer diameter of your pipe size. Slide the discs over the length of your bent tubing to check for interference between pipes and surrounding components.

Measure your straight sections and bends and cut your pipe to those lengths and angles. Get some hose clamps that will fit around your pipe and punch 3 or 4 holes in the clamp's band. Fit the cut piping together using the hose clamps at each joint. When you've got everything to line up and fitted, tack weld the joint seams through the holes you made in hose clamp bands. Pull off, final weld, test fit and adjust where necessary.

I can't say I've personally used this method but I've made a few sets of headers in tight spaces without it and this is the best non-CAD method I've ever come across.

 

[Ataloss]

If you're going to be designing a lot of tubular exhaust manifold systems, you may want to look at this:

http://www.icengineworks.com/

It's kind of like Lego for headers.

It costs quite a bit for guy designing a manifold for his hot rod in his garage at home, but for a business it looks like a pretty good deal, assuming they regularly design custom exhaust manifolds. It costs about $1300 for the basic 1.75" OD V8 kit.

Bob

 

[samplesecond]

Ideally you design the system on a solid modeling program-but if you are looking for a low buck approach,something to consider is the centerline radius of the 'pvc' mock up plumbing, and how that would (or most likely WOULDNT) correspond to readily available tooling die sets and pipe diameters...if the space is as tight as you suggest it is, then accurately modeling the design is of priority.

As stationzebra recommended-buy cheap mild steel tubing ubends-cut and tack them together-its the best/fastest/cheapest way to throw together

Or you can always go to exhaust design/manufacturing companies for assistance such as Saridea Autosport Gruppe

http://www.Saridea.com

or Milltek Sport

http://www.millteksport.com

 

[MStiller]

we would like to do it in solidworks, because yes, that is the cheapest, but it seems like it would be a much more difficult method of doing it, as while we're all proficient at solidworks, i dont think we're quite that good (or at least I'm not). Plus, we havent completely finalized all of the engine compartment components, so having a physical model of the exhaust in our firewall forward mockup would probably be advantageous. Those exhaust legos look pretty good, but considering we only need to design a single system, they probably arent worth the money for us.

 

[Bribyk]

Solidworks is excellent for designing equal-length headers or exhaust components. You can pick identical bends and straight lengths and place/rotate in 3D until you get everything to meet up properly, kinda like the cut, tack and re-tack method but with less waste. You can usually get away with only 1 or 2 different bend angles and/or radii, making it easy to replicate afterwards.

I don't know if this can be done in other software but my colleage that used this Solidworks method figured it out on his own pretty quickly. Of course, you need an accurate model of the surrounding components though...

 

[IceStationZebra]

Another method that I have seen is to use lengths of flexible radiator hose for the initial layout. I can't remember how they stayed "bent" - but it could be a couple of stiff wires clamped to the hose. Not the most elegant, but I would try this before I go with PVC.

ISZ