rear mount wastegate location
TECH Resident
Joined: Oct 2009
Posts: 793
Likes: 0
From: Michigan
I'll speculate about the difference in WG reference line locations..... 
There often is a pressure differential between the compressor housing and the intake manifold. Usually all you have to do is just mess around with WG spring and/or boost controller to give you the pressure in the intake manifold that you are looking for. The actual pressure in the compressor housing is immaterial.
I think guys probably think that in a rear mount setup there is a lot more pressure differential than there is in a front mount system because of the long charge pipe run to the front of the car. If you look at the actual volume of the charge pipe on a lot of the rear mount setups versus some of the common front mounts I think you'll be surprised to see how big the difference isn't.
The thing is that seems to be really important is to keep exhaust velocity high all the way to the turbo in a rear-mount setup. Reading Phil99vette's thread on crossover size and doing a lot of exhaust velocity calculations has been very enlightening. I'm trying to learn about a lot of these things too since I'm hoping to build my first rear-mount setup this spring/summer.
There often is a pressure differential between the compressor housing and the intake manifold. Usually all you have to do is just mess around with WG spring and/or boost controller to give you the pressure in the intake manifold that you are looking for. The actual pressure in the compressor housing is immaterial.
I think guys probably think that in a rear mount setup there is a lot more pressure differential than there is in a front mount system because of the long charge pipe run to the front of the car. If you look at the actual volume of the charge pipe on a lot of the rear mount setups versus some of the common front mounts I think you'll be surprised to see how big the difference isn't.
The thing is that seems to be really important is to keep exhaust velocity high all the way to the turbo in a rear-mount setup. Reading Phil99vette's thread on crossover size and doing a lot of exhaust velocity calculations has been very enlightening. I'm trying to learn about a lot of these things too since I'm hoping to build my first rear-mount setup this spring/summer.
TECH Resident
Joined: Oct 2009
Posts: 793
Likes: 0
From: Michigan
Another bit of speculation on the original point of the thread...
I was thinking that the idea of the wastegate right after the merge of the two banks would be perfect because it would allow for a really small exhaust pipe to be used, which would enhance spool. And then when the exhaust volume goes up due to boost, the wastegate at the head of that long small pipe would be dumping a lot of exhaust gas volume prior to making the long run through the small diameter exhaust pipe, and thus limiting the amount of back pressure through that small pipe.
At this point I really don't know if there is any sense in this, but I can say that after reading Phil's crossover pipe thread and doing the calculations, I would be running a pretty tiny pipe to the back of the car if I had the WG at the front of that pipe...
Thoughts?
I was thinking that the idea of the wastegate right after the merge of the two banks would be perfect because it would allow for a really small exhaust pipe to be used, which would enhance spool. And then when the exhaust volume goes up due to boost, the wastegate at the head of that long small pipe would be dumping a lot of exhaust gas volume prior to making the long run through the small diameter exhaust pipe, and thus limiting the amount of back pressure through that small pipe.
At this point I really don't know if there is any sense in this, but I can say that after reading Phil's crossover pipe thread and doing the calculations, I would be running a pretty tiny pipe to the back of the car if I had the WG at the front of that pipe...
Thoughts?
