I know nothing about exhausts. Ive never had to mess with them.

I wanna HEAR my engine, so I'm building a exhaust.

I have a design that has backpressure, but no collector.

Is a system with matched length the best type of system, as shown in the figure?

And Is the use of a collector correctly used?

Hope its not too crude.

You are walking on ground that seems simple, but is the most scientific in the entire engine combo. It is always considered least by builders, when it is the second most important part of the combo!!

Without proper exhaust you have nothing, all the work and money that went into the intake and mechanical aspects can be totally wasted- what goes in must come back out, or at least about 80% of it! If this doesn't happen the engine will run rich, be untunable, run hot and not make any power. Exhaust selection should be made FIRST before chosing cam or heads!!

It looks like you plan a 4-2-1 system by the drawing, those are the most sdifficult to do because you have both primary and secondary lengths and diameters to worry about as well as collector lengths, tapers and goilets to consider. With a 4-1 system you have ONE collector, with a 4-2-1 system you have two collectors and collectors are an integral link in the chain!

if you do this right, as equally lengthed as possible you will quickly see why a Tangerine 4-2-1 arrangement is so expensive. If you goof up you won't know till you drive it and the engine runs uncontrollably rich.

See this page on my site, its from an exhaust shootout I did in 2005, all with production units for our conversion engines. Look at the power differences, over 20HP on the same engine with two different, similarly priced exhaust systems.
http://www.aircooledtechnology.com/r_d_exhaust.htm

Thats how much it matters.

Don't base an exhaust on sound or looks primarily, doing so is certain demise from the day the first tube is bent.

Well....

To be honest with you.
Your basic design will work.
And you will be able to HEAR your engine as you show no muffler.

And unlees you get the primary's and secondary lenghts correct and use the appropriate collectors and muffler system.

You may well loose HP over a stock system.

I realize your drawing was rudimentary and doesn't show the real details of your thoughts.

So I suggest you make a better drawing to show us some detail. And that I will make comment on directly.

Note: My thinking is that the your 4 into 2 into 1 system is a good thought. Much like the newer Tangerine system.
http://www.tangerineracing.com/Super_Header.htm

Now my OPINION about teener headers (And I am far from an expert)

The following is based on a 1.7 to a 2.5 engine under a 150HP

Using at least 1.5 ID Tubing.on the primary's and 2.00 or 2.25 on the secondary's
and finishing with 2.5 to 3.0 on the final collector to muffler.

You primarys and secondary's cumulatively should be about 30-32 inches long or a bit longer. And NOT shorter than that. This excludes final collector length. and does include your first 2 into 1 collector length.
A longer final collector 8 inches+ is better than a short collector. It may be easier to buy stub pipes than make them. (If you use them at all)
You can buy them already made from george narbell at europeon header.
Or have Thomas EDM you a set of flanges and make your own stubb pipes.

Or have Tiger at A1 set you up. (Google A1 Muffler in Santa Ana, Ca.)

remember that stub pipes need a tweak in them as they go pst the pushrod tube.

Unless you machine up custom pushrod tubes that are machined in a rectangle at the point where the stub goes past them. (It works by the way)

If ya need any reading materials on header design. take a look at the following.

1) http://www.stahlheaders.com/documents.htm
2) http://www.burnsstainless.com
3) http://www.stans-headers.com/faq.htm (ask Stan any question. he rocks)

And you may want to search up "Headers" over at the STF forums and see what ya learn. (Theres a lot to learn there if ya search)

http://www.shoptalkforums.com/viewforum.php?f=1 (Tunas Forum)
AND
http://www.shoptalkforums.com/viewforum.php?f=47 (Jakes Forum)

There have been several good header building discussions on this forum also.

Bottom line... Hell go for it. You will learn a ton doing this and the worst that can happen is you will learn a bunch of new stuff.

I do have a question for you... If ya just want your engine exhaust louder. All ya need to do is put a loud muffler on whatever exhaust you already have.
Thats CHEAP..!!!

If you are looking to advance your performance. You have got a bit "O" homework to do. IMHO...

Take a look at Jakes site and read about the header tests he perfomed.
You will find it enlightning. (I did)

Regards, And have a great time learning..!!!!!

Clayton

Crap.. you beat me too it again Jake...!!!!!!!!

Go back to sleep so i can pretend I know something... (wink)

You must type faster than me by a factor ten or sumpin.

Clayton

Get up earlier... @2 Am your time I already had my hands dirty... This will be another 22 hour day!

We both have the same disease you know....

Cept you figured out how to make it work.

Twystd1

Clayton

I think the Tangerine header is a very good design...

I'll see if I can do some homework and get together some options, i'll let you know what comes out of this.

b

Britt,

The firing order of the T4 is 1-4-3-2. Your sketch shows primaries from 1 and 2 joined and 3 and 4 joined. To get a balanced flow you want balanced exhaust pulses, which means for a 4-2-1 system you should have primaries from 1 and 3 joined and 4 and 2 joined.

Check photos of the Tangerine systems or a Bursch extractor, all examples of 4-2-1 systems.

Good point, something I had overlooked.

b

I've been curious about this as well. With the 32" length for the primaries and secondaries how does the ratio of primary length vs seconday affect performance. Would it matter if the primary was 10" long and the seconday 22" or visa(sp?) versa.

I have but a simple question.

Why use collectors at all? Can't you use 4 seperate tubes and NO collectors (ala stock heat exchangers with 4 small mufflers)? I know 2 would be longer than the others, but is there a problem with independant exhausts? Are collectors required?

Don't dragsters that try to get maximum horsepower run seperate open exhausts?

dont you gain something in scavenging by pairing up cyl's?

NOT to piss in your cheerios, but there is a lot to both the engineering and fab of headers, and this is something best left up to the experienced. by all means, learn if you want to -- but expect it to take much more time, effort, education and energy than you can reasonably get from even a great site like this. by the time you've mandrel bent 40 test tubes, you could have bought a few tangerine headers. the fact is, with the three aftermarket headers on the market for 914/4s, 914ers have good options.

John brought up the question of why we need to have collectors at all.

WELL..... Top fuel dragsters are at about the 8000 HP mark now days.

Thats about 1000 HP per cylinder.

Plus they get lousy fuel mileage.

Bout 20 gallons......per mile. (really)

The way they are built and the fuel they use have no need for a collector style exhaust. They need no back pressure or resonance tuning at that kind of power output.

And they don't use gasoline. So they are a very different breed of engine combination. (Bout 90% nitromethane and a splash of alcohol)

If you look at all the Race gas or pump gas race cars. They all have collectors in their exhaust system.

I "THINK" that Top Fuel and Blown Alcohol are the only race engines that don't have collectors in their engine exhaust package.

By the way.. This is a great thread....

Over at Jakes site there is a EXHAUST ONLY area that Chris Foley Admins... You may want to go over there and ask some more question. Also STF is another resource.

Let us know how it goes........

C

Back when Blake was building an E Poduction 1800CC ty 4 I was reading about exhausts and bought the Pete Weber ( now Tangerine) system. I read a dyno report that said that 4-2-1 system gave 5 HP at 5000 RPM on a stock 2.0L With no added stress to the engine . Good enough for me.

Those dragsters are being fed by Superchargers fit for engines 3X their size and living off of Nitromethane...

There are no comparisons that can be made between those engines and the engines that we are working with.

EVERY attempt I have ever seen to get rid of collectors with these engines has been a catastrophic nightmare of no power and shitty tuning...

I have seen 30+ HP lost when a collector was removed for a "Dual" set up. Thats why you need a collector.

Exhaust with these engines are everything, without proper exhaust, power capability is greatly reduced. Come stand by me for 20 minutes and I'll prove this to you...

Oh, no need in 3 weeks we'll be able to broadcast dyno runs LIVE via the net and you'll be able to see 4 views from the control room and dyno cell, and we can test two engines simultaneously! All you have to do is subscribe- info coming soon.

Geez guys, don't get all bent out of shape when I ask a question, I'm not trying to .

Ok, so everyone agrees that collectors are needed/required.

I'll assume that it has something to do with pulsewaves generated by the exhaust valves. And fluid flow dynamics.

Then, along the same line of thought, should the INTAKE side also be tuned for similar but opposite pulses generated on that side of the equation (much like Varioram intake manifolds)? Wouldn't this benefit the engine/power output in a similar way?

Could a variable exhaust be designed based on engine requirements?



Again, I'm not trying to stir shit, I'm just asking...

ZYes, the intake side of things can be an open door IF you have an adequate exhaust and a capable combination of engine internals..

We have observed an 18HP increase on a 180 HP engine with a 3" shorter intake, then another 3.5 HP and 200 added RPm when an optimized velocity stack was used in conjunction with the intake..

Intake tuning can only occur once the exhaust is known to be effective.

So that would mean that the Porsche exhausts on the Varioram cars are already effective. Ok.

Thanks.

We'll be developing components for those engines in the months to come- I'll let you know about this time in 2008.
Speculation isn't what I specialize in.