E46 330i Manifold Swap
September 2, 2019: this is a work in progress....
E46 manifold swaps are not common. Internet experts say there is no gain. But they say nothing about any losses so what downside can there be? I believe the internal design of the 330i manifold gives better flow at upper RPM. I think BMW wanted the 330i to be a real performance sedan but didn't want the smaller 325i to feel slow at low RPM so they tuned the 325i for better mid-range torque and the 330i for better top end output. There has to be a reason E46 325i race cars used the 330i manifold.
I shift over 4,000 RPM every time I drive. I'm in that upper range where the 325i manifold falls flat but the 330i manifold is just waking up. So I believe this swap will benefit me. Like I said above, there really can't be a downside.
The 330i has several key differences - the DISA valve and throttle body are both larger. Both are compatible with the 325i wiring and other hard parts like brackets. Everything else can be swapped from the original 325i manifold or ordered new. At the same time as the manifold swap, I'm also installing an M56 valve cover so I'll be doing away with the complex M54 crankcase vent (CCV).
Somehow I forgot that the M56 engine uses a 330i-spec manifold. The M56 DISA valve is the same as the 330i. The manifold is a different part number specific to the M56 but I think that has to do with the CCV Distribution Piece only having one port. I capped off the second port on the 330i with a 14mm cap. The throttle body is specific for M56 too (not sure what the difference is).
With the M56 valve cover I'm going to end up with nearly a whole M56-spec engine. There are other M56 differences but I am less enthusiastic now about the manifold swap making more power at upper RPM. I'll have to wait and see... In my mind, no difference is not a loss.
UPDATE: the 330i manifold feels fantastic.
Why paint it silver? It's rare to see anything painted in the E46 engine bay. There is so much black plastic and I don't think anyone personalizes the engine bay as much as other cars (E30 or N54 for example). I end up painting almost everything I remove/install so of course I considered painting this manifold. I decided on silver because BMW intake manifolds were originally unpainted silver aluminum. So I'm resto-modding this look like a vintage BMW part. The valve cover will either be wrinkle black or body-colored Silver Grey.
I had assembled almost all of my parts for this job when my starter failed. How fortunate! The manifold needs to be removed to access the starter so I was well prepared.
Overall the manifold swap went very well! I didn't break any bolts or hardware and I had everything I needed for the replacement. The starter, on the other hand, took a lot longer thanks to a stripped bolt. If you've read any of the multiple DIY posts on the manifold you have all you need to know. I have just two additional tips:
1. Watch this video on disconnecting the fuel line:
2. There are 4 coolant hoses you should buy, assemble off the car, and install as 2 complete pieces. Also, plan to drain the coolant and get messy.
The only 330i parts I needed were the throttle body seal, lower throttle body boot, plastic boot connector. If you pull the DISA valve you will need a replacement sealing ring.
The 325i upper throttle body boot was able to stretch and fit over the 330i plastic boot connector. This is essential as the 330i HFM on the airbox is not compatible with the 325i software. The plastic connector is an intermediate piece connecting the upper and lower rubber boots. The 325i is a little small but was able to pry it onto the connector with a little Simple Green as lube.
Everything bolted right on! It was quite easy to re-assemble. The only difficulty was keeping the wiring out of the way.
A word of caution: with the fuel rail disconnected and fuel drained, it takes a lot of cranking to re-presurrize the fuel system and start the car. I don't know a way around this except maybe adding some fuel back to the fuel rail just before reinstalling it. With fresh seals and reseated on the rail the injectors happily click away, which sounds bad but is normal.
All important verdict. Was it a success or not worth it? After a month of driving I have to say this was absolutely worth it. But I can't say what has made the best improvement. Was it the manifold design and larger DISA? Was my 325i DISA broken (I haven't checked yet). Are my fuel injectors working better with new seals and re-seated on the rail? Does a better CCV give more performance? Does the larger 330i throttle body flow so much better?
Hard to say what made the engine run better. It has more punch over 3,500 RPM. In the 3,500-4,800 range it is noticeably quicker even when rolling gently into the throttle. At heavy load (60% or more throttle) it is faster overall. It did not gain much of anything on the highway in 5th gear, which I was really hoping for. There may be a slight loss in low end torque, right off idle but it's hardly worth mentioning.
Overall, a HUGE SUCCESS!
Read MoreE46 manifold swaps are not common. Internet experts say there is no gain. But they say nothing about any losses so what downside can there be? I believe the internal design of the 330i manifold gives better flow at upper RPM. I think BMW wanted the 330i to be a real performance sedan but didn't want the smaller 325i to feel slow at low RPM so they tuned the 325i for better mid-range torque and the 330i for better top end output. There has to be a reason E46 325i race cars used the 330i manifold.
I shift over 4,000 RPM every time I drive. I'm in that upper range where the 325i manifold falls flat but the 330i manifold is just waking up. So I believe this swap will benefit me. Like I said above, there really can't be a downside.
The 330i has several key differences - the DISA valve and throttle body are both larger. Both are compatible with the 325i wiring and other hard parts like brackets. Everything else can be swapped from the original 325i manifold or ordered new. At the same time as the manifold swap, I'm also installing an M56 valve cover so I'll be doing away with the complex M54 crankcase vent (CCV).
Somehow I forgot that the M56 engine uses a 330i-spec manifold. The M56 DISA valve is the same as the 330i. The manifold is a different part number specific to the M56 but I think that has to do with the CCV Distribution Piece only having one port. I capped off the second port on the 330i with a 14mm cap. The throttle body is specific for M56 too (not sure what the difference is).
With the M56 valve cover I'm going to end up with nearly a whole M56-spec engine. There are other M56 differences but I am less enthusiastic now about the manifold swap making more power at upper RPM. I'll have to wait and see... In my mind, no difference is not a loss.
UPDATE: the 330i manifold feels fantastic.
Why paint it silver? It's rare to see anything painted in the E46 engine bay. There is so much black plastic and I don't think anyone personalizes the engine bay as much as other cars (E30 or N54 for example). I end up painting almost everything I remove/install so of course I considered painting this manifold. I decided on silver because BMW intake manifolds were originally unpainted silver aluminum. So I'm resto-modding this look like a vintage BMW part. The valve cover will either be wrinkle black or body-colored Silver Grey.
I had assembled almost all of my parts for this job when my starter failed. How fortunate! The manifold needs to be removed to access the starter so I was well prepared.
Overall the manifold swap went very well! I didn't break any bolts or hardware and I had everything I needed for the replacement. The starter, on the other hand, took a lot longer thanks to a stripped bolt. If you've read any of the multiple DIY posts on the manifold you have all you need to know. I have just two additional tips:
1. Watch this video on disconnecting the fuel line:
2. There are 4 coolant hoses you should buy, assemble off the car, and install as 2 complete pieces. Also, plan to drain the coolant and get messy.
The only 330i parts I needed were the throttle body seal, lower throttle body boot, plastic boot connector. If you pull the DISA valve you will need a replacement sealing ring.
The 325i upper throttle body boot was able to stretch and fit over the 330i plastic boot connector. This is essential as the 330i HFM on the airbox is not compatible with the 325i software. The plastic connector is an intermediate piece connecting the upper and lower rubber boots. The 325i is a little small but was able to pry it onto the connector with a little Simple Green as lube.
Everything bolted right on! It was quite easy to re-assemble. The only difficulty was keeping the wiring out of the way.
A word of caution: with the fuel rail disconnected and fuel drained, it takes a lot of cranking to re-presurrize the fuel system and start the car. I don't know a way around this except maybe adding some fuel back to the fuel rail just before reinstalling it. With fresh seals and reseated on the rail the injectors happily click away, which sounds bad but is normal.
All important verdict. Was it a success or not worth it? After a month of driving I have to say this was absolutely worth it. But I can't say what has made the best improvement. Was it the manifold design and larger DISA? Was my 325i DISA broken (I haven't checked yet). Are my fuel injectors working better with new seals and re-seated on the rail? Does a better CCV give more performance? Does the larger 330i throttle body flow so much better?
Hard to say what made the engine run better. It has more punch over 3,500 RPM. In the 3,500-4,800 range it is noticeably quicker even when rolling gently into the throttle. At heavy load (60% or more throttle) it is faster overall. It did not gain much of anything on the highway in 5th gear, which I was really hoping for. There may be a slight loss in low end torque, right off idle but it's hardly worth mentioning.
Overall, a HUGE SUCCESS!
