SNAIL

PerI · Posted: Wed Jul 06, 2011 9:40 am Post subject: Exhaust for Ami Super

Hi,

My Ami Super has a few holes in the exhaust system, and of course in the expensive (if it's possible to get it) part near gearbox.

What would be a good alternative to original exhaust? I'm not looking for very noisy ones, but if someone has a good setup, I'm interested in knowing which components are used.

Sincerly,
Per
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'71 2cv 6 · '74 Ami Super Berline · '70 Ami 6 Service (project) · 2(3) AZU projects · 2cv since '93 · C5 v6.24 · GPicasso 2.0 hdi · 307cc

MrDyane · Snailer Joined: 05 Jul 2009 Posts: 39 Location: SF

I had to replace my own when I changed 5-speed gearbox to my car. I think the best way to do it is to buy corners and pipe enough and use TIG-welding. In that way you can make good 2-1 pipe with smooth flow. I have one silencer where normal 2cv has it and one big in the back. Not anymore so loud, more like low nice sound.

Cool

Jasu · Dropped Joined: 30 Sep 2007 Posts: 211 Location: Finland

MrDyane · Snailer Joined: 05 Jul 2009 Posts: 39 Location: SF

Yep. This is a good example of "Don´t do it like I did, do it like I say you should do it". That one I made with MIG-welding and it shows Sad

The 2-1 part shouldn`t be done like that and I`m planning to change it when I do the rest of the exhaust system. The reason for exit pipe looks is the 5-speed gearbox and steering shafts, those needed some space.

Anyway even with that piping system I got more low rpm torque and better rewing.

wolfgang möhler · Posted: Fri Nov 18, 2011 8:40 pm Post subject:

Hi,

I guess the required piping would go like this:

I used the original headers, but unscrewed them, cut the stupid 180°-turn away and installed them exchanged left-to-right. Then it was easy to find a way with some old pipes from scratch and a really smooth Y-element 2:1. On the passenger's side, as it went out there to avoid heatr near the master-brake-cylinder, I installed two silencers I found on an Audi Quattro, I guess. It's years ago and I think, it's your choice to get the best sound out of it.

Regards and enjoy!
Wolfgang
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MrDyane · Snailer Joined: 05 Jul 2009 Posts: 39 Location: SF

One major thing when doing these exhaust pipes is to do it symmetrical. That last one is already better than the original but not symmetrical. The two front cylinders should also have longer "free" piping before getting together with the back ones. The space is really tight but anyway it is possible to do. Main connection to the exit pipe should be done somewhere under or behind the gearbox to get the same length for the both sides.

wolfgang möhler · Posted: Sun Nov 20, 2011 9:20 pm Post subject:

Hi Mr. Dyane,

you're quite right. In these days I had those ideas, too. On the other side, I was really pissed from six years daily driving with the original banana under the gear-box. That ensemble I showed in the pics was a real improvement. With the curved pipes on the right I somehow managed to get a similar resistance as I have on the right with only one wide curve in the pipes.
This setup reduced my oil-temperature in top-speed-runs about 15° and I recieved a quicker response to throttle-kicks. I lost some of the heating's energy without the 180° pipe inside the cooling-housing. But I don't mind about such minor topics.

Regards Wolfgang
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I'm going down to Bopland.

MrDyane · Snailer Joined: 05 Jul 2009 Posts: 39 Location: SF

Hi Wolfgang and other readers

Have you tested the flow somehow? With GS/GSA engine that start of piping is important because there is a need for space because of the next cylinders explosion. I describe it with imaginary "slow motion picture": Think about one explosion for example in the front cylinder, now the pressure goes to the pipe, then the next air and gasoline load explodes in the next cylinder and gives the same pressure to the exhaust pipe. At this point you have to think where the first explosion wave is going? If that is at the same point from where the next one is coming out, there becomes a vortex which is slowing down both of those...not good...Especialy for the low RPM torque. This is hard to explain without real pictures or video but I hope you got the idea. Anyway, when the length is right then the frequency will be optimal and in this case the first explosion will help the next one by "sucking" the second one out... Its like cars in a tunel: When somebody is slowing down there comes wave back and forth but when everybody is going at the same speed and with same distance the flow is good Wink

If somebody thinks that here is some crazy professor writing bullshit, I recommend to check out some rally cars intake and exhaust piping and you will see the same deal what I have been trying to say in here. Ofcourse those are totally different deal compared to a road car but with these same principles you can improve fuel economy and so on...

Have people been thinking why for example GSA 1.3 liter engine is so underpowered compared to the size of the engine? (HP / Liters) Its probably because of the old French tax-system. It was cheap to have low HP but of course nice to have lot of torque. That's basicly the GSA 1.3 liter engine in a nuttshell! Because of all this the GSA engine is a good starting point for a lot more powerfull engine and with these piping issues you can make a difference. Cool

wolfgang möhler · Posted: Mon Nov 21, 2011 9:55 pm Post subject:

Hi there,

for sure, I know these theories very well. Had some discussions 'bout that in the early 1990ies with my engine-professor. After a while, he must have found out, that our class wasn't that much in theoretics. All of us were workin on different makes but all were into that trial-error-thing. So he gave it up and introduced us into his own hand-crafted example: Fiat Uno with a self-adapted blower and water-injection. Unfortunately, I forgot everything about this in all the years. Nowadays I would need that.
So pls excuse, but I cannot help with any basics on the piping. It was just half eyeball-engineering and half luck.

Regards

Wolfgang
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I'm going down to Bopland.

MrDyane · Snailer Joined: 05 Jul 2009 Posts: 39 Location: SF

Hi

I didn´t try to be any rude, it just seemed that at Snail there is people who is doing and thinking these piping issues and it would be nice to have long long discusions about how those are working and so on. Theory is always just a theory and in many cases the final and best solution comes from experimenting and experiences. My own system is still under construction and suffering lack of time and money so it´s bad to hit any real results on the table. I only know two of these systems (in 2cv supers) in Finland and both have been successful compared to the original system.