has anyone rune the s52 through pipemax?

[pbonsalb]

If you go any bigger than about 1.75 inch or metric equivalent on the primaries coming out of the head, there is not room to get nuts on the studs. RMS made headers with 1.75 primaries -- I ran them for a while mated to a euro Supersprint mid and rear. I think kromer kraft offered a stepped header that went from 1.75 to 2.00 but am not certain.

[JEC928]

From my limited knowledge of exhaust gas dynamics, wouldn't a sudden large diameter increase after the head's exhaust port be a detrimental flow characteristic?

#IneedPipemaxToo

[pbonsalb]

Stepped is ideal for that reason. Preserves or enhances torque. But the only stepped E36 header I know of is the NLA kromer kraft.

[JEC928]

After some googling and reading tech articles, it seems the consensus is that the stepped header design broadens torque curve and prevents reversion.

I read a couple decent articles from the 'Murican carb'd V8 world, and a couple engineering pieces that were dense AF, but this 4-banger article had way more interesting graphs and layman's level terminology:
http://www.team-integra.net/forum/bl...ine-power.html

/thread hijack, please carry on OP.

[digger]

In my mind it’s cheaper, easier and better to make a stepped header yet you don’t see it being common….. go figure.

If a gas is going in the correct direction at high speed it has a lot of kinetic energy (proportional to V^2) and if you suddenly get a finite reversion pressure pulse. The reversion pulse has to slow the already moving gas down to zero and accelerate it in the reverse direction for there to be actual reversion in the cylinder. So any given reversion pulse is not going to cause as much reversion if the pipe size is small off the head because the kinetic energy of the flow reduces its effect.

If you run a small pipe from the header pretty much everyone knows that you get high pumping losses. Most don’t pick up on the fact that 12” of 1.5” tube offers less pumping loses than 24” of 1.5”. So you get the best of both worlds with a stepped header high velocity off the head but then stepping to a larger size downstream reduces pumping losses compared to running the small diameter all the way. A stepped header kind of looks like and acts like a tapered pipe which are common on 2 strokes…For sure the slight step also offers some anti reversion properties.

In the same way a venturi merge can be extremely small in a 3 into 1 merge almost as small as the primary because there is very little length of small diameter in a venturi. If the headers are grouped 1-2-3 and 4-5-6 the firing is 240* separation so the cylinders are almost completely separated.

For example I know burns will want to step up the collector outlet from say 2” to 2.25” with a venturi merge (don’t know what choke they don’t tell you until you pay for it), the merge protects the bottom end torque allowing you to use a larger collector size downstream to make more power because long lengths of the same diameter pipe do causes losses. they say using a venturi merge allows you to protect the bottom end so you can also use slightly shorter primaries which have more power potential.

For street engine configuration IMO BMW had it right on the euro S54B32 and S50b32 the collector length being in tune at low rpm and the primaries at high rpm giving a nice flat torque curve. Being intune just means you have a nice suction (low pressure in exhaust port) to lower the cylinder pressure and remove residuals which also happens to draw the inlet charge through during overlap despite the piston actually moving upwards. you have no chance of getting any sort of good VE if the exhaust doesn't scavenge well.

You can use the same approach as BMW but refine it for the higher amount of mass you have, different rpms you are turning with your modified engine, keep it small diameter off the head stepped up to reduce pumping losses, Better transition off the head and more gradual bends, venturi merges, refined primary and collector lengths, cats that don’t offer as much restriction, freer flowing mufflers. you need to use some science. you dont want to spend a whole bunch of money on randoms things but there are plenty of modelling tools, pipemax give some info, ENGMOD4T allows you to look at pressure traces to see what different sizes,lengths, tapers do and how the cam timing affects it all. also burns can do some calcs for you.

You can gain mid to high rpm power with a shorter collector but there is always a tradeoff as at low rpm below 4000 rpm you get a heap of reversion which might not matter to you if its a race engine.

I’ve thought about having dual collector length so running two merges, an H at the 4th harmonic and another X/H/Y at the 2nd. With an electronic flap in the first H you can keep the first H inactive most of the time but at WOT open the flap above a certain rpm, say 3500 rpm/4000 rpm. Finding something compact that can deal with the heat and not get carboned up might be an issue. My particular engine being a crappy 2V/cyl with less than ideal exhaust port (started out as a MM head who don't believe in exhaust tuning lol) keeps making more torque everywhere with the longer collector/secondary pipe length so i've not pursued it. With an new proper head and cam i might design a new set of headers and design it such that i can retrofit a valve or use a block off plate in the meantime.

[tiMASTER]

I want to resurrect this thread!

I also wanted to throw something into the calculation mix... I don't know what the flowmax program is capable of, nor do I know all the variables it takes into consideration for the final calculations.

But, from my R&D days, I know that in addition to the pressure changes with diameters etc., you also have temperature change (dropping as you get further from the head) due to radiant cooling. Then there is the DeLaval principle (CAUTION: Rocket science!) where the heat energy is converted to velocity. But when a pipe is equal diameter, and the gas is cooling as it travels down this pipe, it also slows down. Making the diameter larger makes this worse (in my mind anyway). If it was a DeLaval nozzle for a pipe diameter change, that would increase velocity. (make a rocket nozzle in your exhaust pipe). Downside of the DeLaval is that it is fixed, and therefore optimal for a specific set of conditions. Rockets work great when "optimal"; not so great when parameters are not optimal.

I had a high-revving big block Mopar years ago. It was 3" (per side) head pipe (off the collectors) that went through a flowmaster reducing cone into a 2-1/2 in and out muffler. (no H pipe) The design was directed by what was available at the time, but in hind sight I think it worked well simply because as the gas was cooling and beginning to slow, it hit that cone and then through the muffler and ultimately out the back. So maybe the gas velocity was holding somewhat constant over the exhaust length due to the "restriction". Keeping the velocity constant would presumably keep the scavengeing action high and constant as well.

The decision to delete the H pipe was based on the "added torque" of an H pipe. Um, with 453 inches and the largest cam that wouldn't dent my pistons low end torque was not an issue. That stupid (smog!) motor revved freely to 6500+. I was too scared to rev it higher but it was still pulling like a fleet of freight trains.

On that car the primaries were 1-5/8" (Hooker Super Competition) to 3" collectors; 3" head pipe (probably 30-36"); reducing cone (about 12-14" 3 to 2-1/2); welded to a small block flowmaster 2-1/2 in and out; 2-1/2 back to the rear bumper, maybe another 30-36"?

I have all the receipts from that engine and thought I might build another some day (with better internals) but probably never will....

[cpalella]

e36 Alpina B3 headers. They look quite similar to the euro headers with less severe bends and longer collectors

I am still planning this project.

alpina b3 exhaust manifold 1.jpg

alpina b3 exhaust manifold 2.jpg

[digger]

what are you trying to do?

here are the inputs, if you have a modified engine what mods has it got?

pipemax doesn't tell you one answer because there is no one correct answer unless you give a very specific requirement.



the best way to use it is get a dyno run to calibrate

[cpalella]

what are you trying to do?

here are the inputs, if you have a modified engine what mods has it got?

pipemax doesn't tell you one answer because there is no one correct answer unless you give a very specific requirement

the best way to use it is get a dyno run to calibrate

Basically, I'd like to use some science while building the next exhaust system. Instead of just sticking pieces together, I'd like to figure out where is the best spot to place a y merge, or x pipe, what size/length/shape should the 3-1 collector be, what size/length/shape should the 2-1 merge be, how long/what size should the primaries be etc. I don't have any illusions that I'll pick up a big chunk of HP, I'd just rather put it together with some sort of educated design.

I think the euro headers are a decent starting point, though I'd like to see if I can come up with any improvements. For example, compared to other properly built exhaust systems, the primaries seem a bit short and the 3-1 collectors seem fairly primitive. It doesn't look too tough to cut the 3-1 collectors off, possible neck the primaries up slightly larger and make new/better 3-1 collectors.

[digger]

list the mods. cams, cr, current peak hp rpm and current hp