complications in building headers

[vikram.]

hello friends
i have been building headers,and now making for our car,but there are some issues i'd like to share with you guys before proceeding..
the problems are
a. mandrel bends
I have tried CNC bend, Mandrel bend, Hot sand bends.
What ever route you take there is going to be a shrinkage in the diameter of the pipe. This no matter how small is unacceptable to me.
SO what is the solution or how do professional race teams solve this problem. This brings us to point two.
They use bends. You can get bends in any various sizes either MS or SS. 45 / 90 / 180 etc. With and without seams

b. The problem with bends is you only get them in fixed sizes i.e. 1", 1.5" 1.75" etc.
Now your saying whats wrong with this ? Whats wrong with this is that unless by pure luck the optimum diameter of the primary and secondary match. You are not using an optimum diameter. I know to some people this is not a big issue a little bit this way or that really doesn't matter.


thanks

[vikram.]

hello friends
i have been building headers,and now making for our car,but there are some issues i'd like to share with you guys before proceeding..
the problems are
a. mandrel bends
I have tried CNC bend, Mandrel bend, Hot sand bends.
What ever route you take there is going to be a shrinkage in the diameter of the pipe. This no matter how small is unacceptable to me.
SO what is the solution or how do professional race teams solve this problem. This brings us to point two.
They use bends. You can get bends in any various sizes either MS or SS. 45 / 90 / 180 etc. With and without seams

b. The problem with bends is you only get them in fixed sizes i.e. 1", 1.5" 1.75" etc.
Now your saying whats wrong with this ? Whats wrong with this is that unless by pure luck the optimum diameter of the primary and secondary match. You are not using an optimum diameter. I know to some people this is not a big issue a little bit this way or that really doesn't matter.


thanks

[exFSAE]

If manufacturing variation / changes are "unacceptable no matter how small" you're going to have a tough time in the real world.

[Joe17]

sounds like you live in a world of solidworks, where everything can be made perfect

[vikram.]

comon dude,i m tuning engines for 6yrs now from high school,designing exhaust is like daily work,what i asked over here is not a problem its what that happens in real world,fact and its like evolution,there is this problem which happens..

[vikram.]

okay possible suggestion-
a. We use sheet metal to cut and design the complete system. Considering the temps are going to be at around 750c. How thick a gauge would work.
b. We figure out who makes pipes and we ask them to do some custom bends and diameters in the size we want. Just like we do on the two stroke chambers. http://fsae.com/groupee_common/emoticons/icon_smile.gif

[Zac]

If proper tube size and quality of bends are THAT big of a concern for you, you could always go for a custom cast exhaust manifold...

...or maybe you should just stick to standard tube sizes in order to get something done on time and on budget.

[vikram.]

custom cast is not a good idea i suppose ....
the main fundamental is to figure out how much to crimp without adversely effecting flow would take some serious procesing power.
Its not as simple as crimp a bend and it will make more power. I wouldnt know how much to crimp it.
Too little or too much will do harm.

By using the right sized pipe you have better control over the gas velocity.

Simple question do any of the ground braking really fast engines in any race series use this ? NO

Ps: There are other tricks to prevent the flow reversion and speed up flow ..wont tell now

Right now solving the dia size or finding somebody to do custom dia pipe and seamless bends for me is more critical.

[exFSAE]

Well in any event I highly doubt you're calculating any true "optimum" diameter that your headers need. Any "optimum" point in real engineering is a fantasy IMO, particularly at the FSAE level.

Figure out what diameters you THINK you want, pick the closest standard size, and go with it.. just like everyone does.

[vikram.]

lets see,precision is what was required...will be contacting some professional. lets see how it goes.

[Mbirt]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by vikram kumar:
What ever route you take there is going to be a shrinkage in the diameter of the pipe. This no matter how small is unacceptable to me.
SO what is the solution or how do professional race teams solve this problem. </div></BLOCKQUOTE>

Professional race teams are designing a dynamic system in which the intake ramming, exhaust scavenging, camshaft profile, etc. all work together to produce a desired torque curve. One of the given subsystems of the overall package is not designed in a fantasy land where it is not affected by the other components. They test above and below their "optimum" parameters to determine what works best in combination with the rest of the system.

To compensate for the infinitesimal backpressure contribution of having to "settle" for mandrel bends, you should get ahold of the super muffler Nishant from IIT Delhi has been designing for the last 17 months.

[vikram.]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Mbirt:


Professional race teams are designing a dynamic system in which the intake ramming, exhaust scavenging, camshaft profile, etc. all work together to produce a desired torque curve. One of the given subsystems of the overall package is not designed in a fantasy land where it is not affected by the other components. </div></BLOCKQUOTE>

wow,like i don't know that, read the post properly mate,hopefully if i am good enough to tune a engine and fabricate my exhaust acc to you,i must have these things in mind,what i am talking here is fabrication to attain perfect bend.

i dont think you'l understand the word perfection and stop being ignorant.

[manifold]

hey
How about serpent type headers with flattened bends? By all reports this type of Micron header smooths out gas flow
let me explain a bit it refine the pressure wave action and gas particle flow reduces energy losses and increase scavenge action
the extremely high speed gas particle flow of your exhaust as it leaves the exhaust port, and picture it entering the first bend in the exhaust header. By centrifugal force, all the gas is "pushed" to outside of the bend in the pipe, causing a vacuum, or "reversion", on the inside bend of the pipe in this same location. Much the same as watching a fast flowing river entering a bend, you can see the water working its way back "up river" at the inside of the bend, which is what is called negative flow.

as explained by the manufacturer

[Price]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Any "optimum" point in real engineering is a fantasy IMO, particularly at the FSAE level.

Figure out what diameters you THINK you want, pick the closest standard size, and go with it.. just like everyone does. </div></BLOCKQUOTE>

This, and the original post remind me of two things: how much I dislike the word optimum outside of a purely academic setting, and how calculations and computer models are only estimations of what occurs in real life.

[manifold]

'optimum' word has created a fury ....

[Xeilos]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">i dont think you'l understand the word perfection and stop being ignorant. </div></BLOCKQUOTE>

I am sorry but I have to respond to this comment. On a side note, I hope this poster is not serious and is instead a troll.

Sir, I do not think you undertand the word reality. It's where we live, wake up.

I would suggest you stop, think, thank the kind people for their help and accept that one man's perfect is another man's imperfect. Very similar to women IMHO.

[vikram.]

that phase was just just for the remark what MDIRT gave about that other indian guy.....i mainly thing its all nationality problem out here...everyone want's to just push you down,does'nt matter who you are..
sorry if that was cold

[Charlie]

I suggest you determine what the primary and secondary tube sizes performance sensitivity is, before exerting so much energy to make it 'perfect'

Figure out what you lose by going from your 'optimum' primary and secondary sizing, to something that is readily available.

You will likely find that the effort needed to make a tube that is 1/16" smaller is not going to net any measurable gain in performance.

This coming from someone that has professional experience (not that it makes my opinion better, but you keep mentioning it)... I would never seek the accuracy you are unless I had substantial evidence that it was worth the time and expense.

[vikram.]

@charlie
i agree with you, the point is i made many headers in past with normal setup,what i gained from my experience and guidance is that i am missing on something and as you told the difference might be minimum.i think its worth the effort and expenses and time atleast for me coz many dimensions will come out of this theory..

thanks for the input

[RANeff]

Psh who needs an exhaust. just dump straight out of the ports!

[exFSAE]

I dunno Charlie, this guy sounds pretty legit. After all, he's got 6 years experience from HS as a master engine tuner. We could probably all learn a lot from all.

[StevenWebb]

buy some pipe slighlty bigger than "optimum", then bend it yourself so there is enough shrinkage in the pipe so that it becomes optimum diameter in the bends, then get a fat person to sit on all the straight sections?

[EHog]

I guess we'll see you in Michigan if you ever find a way to get that exhaust made! In the mean time, we'll keep using our custom "not quite perfect" burns stainless exhaust.

As we say, "It gets the smoke out past the bumper."

[vikram.]

@exfsae everyone can learn anything from anyone,we are never complete.
Ehog i'l sure find a way out mate..

[VFR750R]

Vikram, as Charlie alluded to, the engine isn't nearly as sensitive to primary diameter as you think it is.

Since nobody here has actual data to support or refute your claim, you could build some exhausts with available diameters as close to your 'optimum' as possible but otherwise the same. In the end you'll find the 'real' optimum anyways instead of relying solely on simulation.

I'm guessing you've included thermal expansion in your ex pipe length and diameters http://fsae.com/groupee_common/emoticons/icon_wink.gif

[vikram.]

vfr750r ya thats a do or die situation you have to use something http://fsae.com/groupee_common/emoticons/icon_smile.gif

[BMEP]

I think you have a few options here:

Option 1
All you have to do is convince your supplier to make tooling to roll form the optimum OD pipe. It shouldn't be a problem as you only need roughly 2ish meters worth, tell them you are from fsae and they should consider all activities as a sponsorship. Once you get your pipe you should return it because it wasn't perfect.

Option 2
Take your imperfect bent tubing and ream it out with an appropriatly bent reamer.

Option 3
Weld the exhaust valves shut, this design combines the intake runners with the exhaust nice!!!

Option 4
Don't put a bend in the exhaust. If you orientate the engine properly you can run the exhaust straight up, keep adding length until you pass sound requirements.

Option 5
Drill holes through the center of the exhaust valves. Install an electronically controlled one-way valve in the middle of the exhaust valve, vent exhaust through center of the valve. This design is far superior than other ICE designs because you can optimize when the exhaust opens...tits

Hope this helps

[Mbirt]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by vikram kumar:
that phase was just just for the remark what MDIRT gave about that other indian guy.....i mainly thing its all nationality problem out here...everyone want's to just push you down,does'nt matter who you are..
sorry if that was cold </div></BLOCKQUOTE>
I apologize if my post mentioning Nishant sounded racist. Nishant and I have actually been emailing back and forth after conversing in his muffler design thread. He was hung up on finding the "optimum" perforation diameter for the core of his absorption silencer. He's perfectly knowledgeable about Transparency Index and its relationship with perf diameter and muffler performance. The general consensus among experienced FSAE participants was that testing must be done to determine the noise signature of your engine and the effectiveness of a given muffler design. There was no point in wringing his hands over a "perfect" perforation diameter because it simply doesn't exist.

To further convince him of this, I rolled my school's car out of the shop, did a recording at sound test speed with my laptop, and performed a frequency analysis in Audacity. I then sent him my test data showing that the frequencies one would expect to be the loudest... weren't. Last I heard from him they're going to perform the same test at IIT Delhi.

The word "optimum" and its derivatives are strict taboo in the world of FSAE. We're engineers and need to give justification for our designs.

Finally, if your "optimum" runner i.d. is 1.25", is a header of 1.375", .063" wall tube more "optimum" than a header of 1.25", .025" wall tube? This is the kind of question a design judge might shoot you upon hearing the word "optimum".

I'll ignore the name calling and say that it's good to have someone with experience such as yours here, Vikram. I hope we learn much from the knowledge you have to offer us.

[vikram.]

BMEP
nice thoughts .... http://fsae.com/groupee_common/emoticons/icon_smile.gif

[vikram.]

@mbirt no problem mate
actually this problem which i am facing or actually not a problem is not only related to fsae, here i am talking about the problem i faced while designing some other exhausts..thats what i was asking how race engineers get the perfect match in fabrication perspective....leave the design,leave the other parameters..and ya i agree the effect can be minimum

thanks for the inputs.

[Charlie]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by vikram kumar:
i was asking how race engineers get the perfect match in fabrication perspective.... </div></BLOCKQUOTE>

They don't. They compromise.

There are far more effective uses of a race engineer's time.

[Wesley]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by vikram kumar:
that phase was just just for the remark what MDIRT gave about that other indian guy.....i mainly thing its all nationality problem out here...everyone want's to just push you down,does'nt matter who you are..
sorry if that was cold </div></BLOCKQUOTE>

What are you using to choose your diameters? Hand calculations? Best guess estimates? How much HP will a mandrel bend cost you exactly? Is the difference smaller or larger than your uncertainty in the predictions you're making?

Sometimes all it takes is a couple of quick numbers on a napkin to determine what's the most important. What is the order of magnitude of power loss from the difference in "ideal" and real design? If you can predict your pipe diameter needs to an accuracy to 5%, and the difference in flow in a mandrel bent versus perfect pipe is 5%, where is the gain going to manifest?

You can't spec a part with zero tolerance. They don't make measuring devices that can determine that.

[vikram.]

hand calculated then processed in softwares,can't tell you the hp figure here will check it out during dyno testing, what i am considering is due to possible shrinkage there is loss in flow efficiency and definate amount of flow restriction..i have to analyze turbulent, steady-state fluid flow using finite element..dyno testing will be there then i can compare the graph, i asked some profesional teams they don't do any better they use mandrels