Big exhaust on your Mercs! PICS
Big exhaust on your Mercs! PICS
Im going to start building my exhaust, what is the biggest exhaust you have managed to fit?
I think ill be using 3.5" all the way from the turbo?
Feel free to post pics on your exhaust systems!
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Cars currently owned:
1993 Mercedes Benz 300TDT W124
1992 Mercedes Benz 500E W124
Hello!
Im going to start building my exhaust, what is the biggest exhaust you have managed to fit?
I think ill be using 3.5" all the way from the turbo?
Feel free to post pics on your exhaust systems!
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Cars currently owned:
1993 Mercedes Benz 300TDT W124
1992 Mercedes Benz 500E W124
![[Image: _medium.jpg]](http://sultzi.kuvat.fi/kuvat/MB+W123+-81/IMG_0239.JPG/_medium.jpg)
![[Image: _medium.jpg]](http://sultzi.kuvat.fi/kuvat/MB+W123+-81/IMG_0241.JPG/_medium.jpg)
https://www.youtube.com/watch?v=zXd7NtqnKHA
1984 300d 132k restormod project in the works
1985 300td 300k $600 off road adventure project
1999 land cruiser 235k, 33" mud tires, off road, towing, hauler
not a picture but very purist sacrilege
https://www.youtube.com/watch?v=zXd7NtqnKHA
1984 300d 132k restormod project in the works
1985 300td 300k $600 off road adventure project
1999 land cruiser 235k, 33" mud tires, off road, towing, hauler
(04-27-2016, 06:45 AM)but equally going too big will slow the gasses as they expand to fill the space !? Exhaust diameter will play a big part in the performance. Its a balance between getting it big enough for the flow.... but equally going too big will slow the gasses as they expand to fill the space.
(04-27-2016, 06:45 AM)but equally going too big will slow the gasses as they expand to fill the space !? Exhaust diameter will play a big part in the performance. Its a balance between getting it big enough for the flow.... but equally going too big will slow the gasses as they expand to fill the space.
Think about it a bit like this.... You can breath out at a certain rate but you have to blow down a pipe. Blowing into an empty bic pen is hard, breathing into a drain pipe means the air is going to be slow out of the other end but breathing out brought something like a large garden hose isn't hard to do and keeps the air speed up.
Hope that makes sense
For best performance the exhaust needs to be matched to the engine. Too small and it can't flow enough. But going too big is also harmful due to exhaust velocity. You want the exhaust gasses to get away as quickly as possible, and by going too large a diameter you're actually slowing them down. It's all to do with what's called the 'ideal gas law'. To keep the energy and heat up in the exhaust you need to keep it moving, and going into too large an exhaust will slow it down and cool it as it expands.
Think about it a bit like this.... You can breath out at a certain rate but you have to blow down a pipe. Blowing into an empty bic pen is hard, breathing into a drain pipe means the air is going to be slow out of the other end but breathing out brought something like a large garden hose isn't hard to do and keeps the air speed up.
Hope that makes sense
raysorenson
04-30-2016, 07:14 AM #12Ross, I would agree if you were talking about pre-turbo exhaust sizing. Manifold tubing can get too big and reduce velocity. But after the turbo, the best exhaust is no exhaust. Corky Bell said the ideal exhaust post-turbo is a bellmouth.
The only place you want higher gas velocity is after the exhaust valve. The higher gas velocity of course helps spool the turbo, but can also suck remaining exhaust gas from the cylinders for better scavenging.
This only works when you have gas pulses. Not with continuous flow. It just doesn't make sense.
The ideal situation would be no gas flow after the turbo (no dp or anything) because this leads to a bigger pressure difference. this is not possible but is it at a minimum with nothing after the turbo.
So I'm wondering why would you want speedy exhaust gasses after the turbo?
The bigger the exhaust, the lower the pressure in the exhaust (after turbo of course). So the pressure difference is higher. Higher pressure difference means more flow. It's not that the higher the gas velocity equals more flow. Higher gas velocity is only achieveable by restricting flow.
The only place you want higher gas velocity is after the exhaust valve. The higher gas velocity of course helps spool the turbo, but can also suck remaining exhaust gas from the cylinders for better scavenging.
This only works when you have gas pulses. Not with continuous flow. It just doesn't make sense.
The ideal situation would be no gas flow after the turbo (no dp or anything) because this leads to a bigger pressure difference. this is not possible but is it at a minimum with nothing after the turbo.
So I'm wondering why would you want speedy exhaust gasses after the turbo?
If the gases can expand into too large an exhaust they become cooler and have less energy, so are harder to shift on out of the exhaust. If the gasses aren't moving quickly after the turbo, then how are the gasses coming out of he turbo going to do so quickly!
I took pieces of the stock DP (turbo flange and flex section) and added 2.5" SS 90° bends. The rest of my exhaust is 2.5" mandrel bent stainless with V-Clamps.
Maybe down the road I will do 3" but even the 2.5" is close to the bulkhead and the front driveshaft.
Not big by any means but the I redid the downpipe on my as the stock MB DP was hitting the bulkhead.
I took pieces of the stock DP (turbo flange and flex section) and added 2.5" SS 90° bends. The rest of my exhaust is 2.5" mandrel bent stainless with V-Clamps.
Maybe down the road I will do 3" but even the 2.5" is close to the bulkhead and the front driveshaft.
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