[Biginboca]

An issue has come up that I’m working on addressing and looking for input.

So I kept getting lean codes at idle after going back to stock airbox. Much less often like once every other week now but it’s still there. Carb spray confirmed a leak around the bottom of where the N54 runners meet the head. I changed intake manifold gaskets 3 times and still leaking. In speaking with Bob he said BPC found the same thing on their turbo build and there seems to be a manifold fitment issue.

So it seems that although the n54 and n52 manifolds use the same gasket part number and bolt pattern they are not perfectly interchangeable. N54 has more square ports and n52 more ovalled, plus the locations of where the runners meet the head is slightly different.

So I did some digging in google images and scaled them the same and this is what I found. The N54 manifold sits higher on the head than the n52.

N54 on top and N52 on bottom:



To make the N54 manifold fit perfectly it would need to be lowered a bit on the mounts. I haven’t measured exactly yet but it seems like around 1/16”-1/8” would do it looking at that pic.

The solution that comes to my mind is to make offset sleeve inserts for the mounting holes. (Sleeves with the through holes off center.) Those metal sleeves slide in and out and Bob said they had some success running without the sleeves in the manifold holes and shifting their manifold downwards as they mounted it.

I’m wondering if anyone else has addressed this issue and also if anyone has any other ideas in regards to solving it?

[Biginboca]

For what it’s worth here’s a pic of a n54 on top and n52 on bottom. If you look closely at the bottom manifold mounting bolts relationship to the bottom of the intake ports it’s easy to see how the ports are at different heights. The n54 has the bolts well below the bottom of the ports and the n52 has them centered in line with the bottom of the ports:

[BudVlad]

I have no issues with N54 manifold no codes and idle is stable. Max output with aFe headers was 292 PS, with Supersprint headers 297 PS. Obviously no problem. The reason is probably that the inlets on N53 head are same as on N54 head.

[Biginboca]

Originally Posted by BudVlad

I have no issues with N54 manifold no codes and idle is stable. Max output with aFe headers was 292 PS, with Supersprint headers 297 PS. Obviously no problem. The reason is probably that the inlets on N53 head are same as on N54 head.

What’s surprising for me is my idle is stable also, and the car runs great. If I didn’t get these 2A1A codes popping up I’d have never known there was an issue.

[Biginboca]

Thinking about this some more I realized that if I’m getting into a manifold fix that I need to fabricate then I might as well make whatever changes to the manifold that would optimize it. It’s been said before that the n54 isn’t optimized for max power on the n52, it just happens to work better for the top end.

So the question is... What would be ideal? I was thinking I can easily shorten the N54 runners even more and then graft the n52 mounting plate onto a n54. Really can’t say where I’m going with this now.

Doing some digging I’ve found there’s a custom metal manifold on eBay for n52, and I’m honestly not sure why it’s even made. I’m guessing in Europe some guys are supercharging n52’s and adding some extra injectors or something?



That manifold moves the TB to the front and is a metal manifold. I could easily cut the runners short on that to be more like a n54 and just reweld it.... but I definitely don’t want to spend that on a manifold and don’t see any reason to.

I’m thinking I can easily DIY mod the oem plastic ones. Plastic is so easy to work with and now there’s plastic welding. N52 and N54 plastic take off manifolds are a dime a dozen under $100.

[Noir]

"Talked with Bob this morning and we did find that on the N54 intake that you will also need to press out the inserts where the bolts go though to the head, they dont allow the intake to fit flush so it will leak some. " - SA @ BPC

[Biginboca]

Originally Posted by Noir

"Talked with Bob this morning and we did find that on the N54 intake that you will also need to press out the inserts where the bolts go though to the head, they dont allow the intake to fit flush so it will leak some. " - SA @ BPC

Thanks for sharing that, it’s pretty much what Bob had told me also...

I ordered a pair of intake manifolds today off eBay (n54 and n52). I should have kept my old ones doh!

I’m going to play around with finding a mounting solution and also am considering making a hybrid manifold with slightly shorter than n54 runners.

There is a manifold made for the lsx motor that lets you pick your runners from each of 3 different lengths. It’s modular and you can swap runners at will depending on your usage and how you want to make power. Here’s a pic of the the 3 runners and a dyno with the 3 different lengths installed:





My thinking is maybe just go a touch shorter than n54 for my car because my build is all about favoring the top end and max hp. The dynos I’ve seen so far with n54 manifolds all have a little leveling/drop off starting around 7k. I’m wondering if that peak power can be pushed a little higher with a shorter runner...

[dwashy]

Originally Posted by Biginboca

Thinking about this some more I realized that if I’m getting into a manifold fix that I need to fabricate then I might as well make whatever changes to the manifold that would optimize it. It’s been said before that the n54 isn’t optimized for max power on the n52, it just happens to work better for the top end.

So the question is... What would be ideal? I was thinking I can easily shorten the N54 runners even more and then graft the n52 mounting plate onto a n54. Really can’t say where I’m going with this now.

Doing some digging I’ve found there’s a custom metal manifold on eBay for n52, and I’m honestly not sure why it’s even made. I’m guessing in Europe some guys are supercharging n52’s and adding some extra injectors or something?



That manifold moves the TB to the front and is a metal manifold. I could easily cut the runners short on that to be more like a n54 and just reweld it.... but I definitely don’t want to spend that on a manifold and don’t see any reason to.

I’m thinking I can easily DIY mod the oem plastic ones. Plastic is so easy to work with and now there’s plastic welding. N52 and N54 plastic take off manifolds are a dime a dozen under $100.

Looks like with that metal manifold the furthest cylinder might be getting starved for oxygen, relative to the runners closest to TB. What differences do you notice having the N54 manifold on? I assume less torque and slightly harder pull above 6800rpm? Just curious, as I've got my 3IM off right now replacing starter and CCV. Always wondered what difference N54 manifold made.

Did you go from non-3IM to the n54 manifold?

EDIT: guessing so, since 328i

[Biginboca]

Originally Posted by dwashy

Looks like with that metal manifold the furthest cylinder might be getting starved for oxygen, relative to the runners closest to TB. What differences do you notice having the N54 manifold on? I assume less torque and slightly harder pull above 6800rpm? Just curious, as I've got my 3IM off right now replacing starter and CCV. Always wondered what difference N54 manifold made.

Did you go from non-3IM to the n54 manifold?

EDIT: guessing so, since 328i

https://www.e90post.com/forums/showthread.php?t=1486800

[W37V]

Originally Posted by Biginboca

Thanks for sharing that, it’s pretty much what Bob had told me also...

I ordered a pair of intake manifolds today off eBay (n54 and n52). I should have kept my old ones doh!

I’m going to play around with finding a mounting solution and also am considering making a hybrid manifold with slightly shorter than n54 runners.

There is a manifold made for the lsx motor that lets you pick your runners from each of 3 different lengths. It’s modular and you can swap runners at will depending on your usage and how you want to make power. Here’s a pic of the the 3 runners and a dyno with the 3 different lengths installed:





My thinking is maybe just go a touch shorter than n54 for my car because my build is all about favoring the top end and max hp. The dynos I’ve seen so far with n54 manifolds all have a little leveling/drop off starting around 7k. I’m wondering if that peak power can be pushed a little higher with a shorter runner...

I wish BPC didn't delete their original thread on turbocharging n52 ( I think it was in that thread).

If I recall correctly, BPC tested all intake manifolds and the best results were achieved with modified n52 single stage manifold. I think the modification was that they cut off almost half of the manifold (removed throttle body completely) and run it like that. IIRC, that how they were able to achieve 8400 rpm redline.

Check out this thread (not sure if you seen it already):
https://www.e90post.com/forums/showthread.php?t=1206386

Taskmaster maybe you remember how they did this.

[Biginboca]

Thanks, I came across that thread yesterday when I was doing some reading. I saw a pic of a 128i in one of the threads with the plenum cut off the normal n52 manifold. It has no TB and no air filters with a MAP tune. It was like 265whp if memory serves me right.

[W37V]

Originally Posted by Biginboca

Thanks, I came across that thread yesterday when I was doing some reading. I saw a pic of a 128i in one of the threads with the plenum cut off the normal n52 manifold. It has no TB and no air filters with a MAP tune. It was like 265whp if memory serves me right.

That sounds about right. All this testing was prior to MILVS. I wish exhaust cam turns out some yields.

[Biginboca]

Originally Posted by W37V

That sounds about right. All this testing was prior to MILVS. I wish exhaust cam turns out some yields.

Based on a lot of things I have been reading the exhaust cams done correctly should make a power increase especially on a motor with MILV’s, Headers, and a decent exhaust set up. I think we are getting close to seeing a n52 make 270whp on pump gas which would be outstanding! A lot of the stock S54 dyno’s I’ve seen have been approx 280whp

[Biginboca]

I spent more time looking at manifolds last night. I’m starting to doubt I can do better than the current n54 set up. The runners look pretty short already, and looking at more n54 manifold on n52’s dyno’s there isn’t as much drop off after 7000rpms as I initially suspected.

It looks like the most power to be made through extreme manifold and intake changes over changing from a modded stock airbox with stock n54 wouldn’t even add up to 8 hp. I found the info where BPC tested the set up with open ended runners. Looks like they took a stock N52 manifold and cut off the whole throttle body side so it was just open ended runners into the head, almost like velocity stacks. (no throttle body, and no air filters.)

They got 265whp with basically a manifold delete.

The n54 manifold set up with complete air filter, manifold, throttle body, and a air density tune (maf delete) tested around 258whp on similar set up (same exact dyno and same model car, 128i manual.)

Here’s that open manifold...





But looking at the only dyno I could find those open runners don’t even look like they do as well up top as a n54 manifold. It looks like that set up even though it peaked higher started dropping power after 7000 while n54 manifold dynos kind of table tops after 7k. They don’t drop off hard after 7k like the dyno of that that seemed to show.

So I think I will just adjust the fitment of the n54 manifold and make it line up correctly. With exhaust cams added to current set up I’m pretty sure I can get to 270whp.

That motor which made 265hp on open runners didn’t have the MILV’s and obviously not the exhaust cams. And the one that made 258hp didn’t have those mods either. So I believe I can pass the 265whp level and keep my maf, which I’m not averse to deleting either but I’ll definitely be running an air filter lol

[Phyrexia]

Al, when you gonna pull the motor and put some high compression pistons in there?

[Biginboca]

Originally Posted by Phyrexia

Al, when you gonna pull the motor and put some high compression pistons in there?

I want to do that! I envy the compression of the s54 lol

[Taskmaster]

Originally Posted by Biginboca

Thanks, I came across that thread yesterday when I was doing some reading. I saw a pic of a 128i in one of the threads with the plenum cut off the normal n52 manifold. It has no TB and no air filters with a MAP tune. It was like 265whp if memory serves me right.

Correct.

[Taskmaster]

Originally Posted by Phyrexia

Al, when you gonna pull the motor and put some high compression pistons in there?

Zero gain to be had.

[Biginboca]

Ok finally got around to measuring the 2 manifolds I have on hand...



N52 on top
N54 on bottom

So it looks like from all the measurements I took it the n54 manifold needs to offset downwards about 3.25mm to get the best port alignment on a n52 head.

Now that I have an exact measurement of what we are dealing with I can try to figure out a remedy.

Also the n52 manifold is about 1mm more port opening in the height measurement than the n54 manifold. For width at the widest cross section they are pretty much identical. The overall shape and dimensions of the ports is close enough that if someone wanted they could even do a little dremel porting work to get them extremely close. I may add a little chamfer where the n54 meets the head but I really don’t feel it’s necessary so I might not. Because we are dealing with plastic it would be very easy though.

[Biginboca]

Ok here’s what I came up with after a quick trip to Lowe’s. Found some nylon 1” spacers that after some grinding are a press fit into the oem metal sleeves the manifold mounts use. So I was able to make some offset mounts that press into the manifold.

Also when I was looking at the manifold I found there’s a lot of mismatched seems where the 2 half’s were joined. I spend about 30 mins dremeling and then sanding the manifold seems inside where the throttle body mounts and also there’s a bad seem inside each runner near where it mounts to the head. (The n52 manifold is beautiful inside there are no mismatched seems and it really is made to flow beautifully. The n54 is not nearly as well done as far as how the molding and surfaces are mated.)

[Noir]

I'm thrilled, Big.
if you need help with anything, hmu!

[cwlo]

So it looks like you were able to just press the metal sleeve out of the manifold?

Not sure if it would worth it to fab up new metal sleeves with offset holes. Your approach will probably last long enough, except it might be a pain if the manifold has to be removed and those little nylon pieces fall out. Minor inconvenience though.

I am going to inspect my manifold when I get a chance....I had no indications of any leaking, but will keep an eye on it. Thanks Big