M3 Lightweight Air Duct Help

[sirhodjibob]

Hey guys,

I'm rebuilding the air ducting on my my 99 M3 and need some guidance. The factory plastic center piece was missing, so I replaced it with the aluminum air duct off the lightweight (part # 51712268673) as I intend to run the OE splitter set up. Where I'm struggling is the lower radiator duct. I ordered part #17112227690 but it does not appear to fit. Even if it did fit it seems like it would be extremely flimsy. Did the lightweight use a different piece or did not have one it all?

I am running the Z3M S54 Behr radiator so that may be an issue. AC/Aux fan have been deleted. I have also ordered new pork chops & splash shields.

[blckstrm]

I think you're seeing the problem that's pushed so many of us to aftermarket solutions - the factory setup isn't super robust. I blew mine out at high speed, and I've heard of many others doing the same.

[sirhodjibob]

I think you're seeing the problem that's pushed so many of us to aftermarket solutions - the factory setup isn't super robust. I blew mine out at high speed, and I've heard of many others doing the same.

I can certainly appreciate that. The aluminum duct off the lightweight though does seem to be a nice improvement over the normal plastic one though.

I guess the question I need to answer is did the Lightweight come from the factory with a lower radiator duct?

[Braymond141]

According to the ETK, 17112227690 is an installed part on the Lightweight. There are mistakes in their system so I wouldn't rule out that part being excluded.

That aluminum tray was not made for the Lightweight (very few parts were). It comes from the M3 GT. The GT uses an oil cooler so the ducting is different. Basically I'm going to go with the US part you are trying to install is not used on the Lightweight or it is modified to fit. Either remove it, modify it, or buy the Euro oil cooler setup. Option C is the best.

You can look up these details yourself on realoem.
EA40016 - M3 GT
EH07222 - M3 Lightweight

[sirhodjibob]

According to the ETK, 17112227690 is an installed part on the Lightweight. There are mistakes in their system so I wouldn't rule out that part being excluded.

That aluminum tray was not made for the Lightweight (very few parts were). It comes from the M3 GT. The GT uses an oil cooler so the ducting is different. Basically I'm going to go with the US part you are trying to install is not used on the Lightweight or it is modified to fit. Either remove it, modify it, or buy the Euro oil cooler setup. Option C is the best.

You can look up these details yourself on realoem.
EA40016 - M3 GT
EH07222 - M3 Lightweight

Thanks Braymond, that would make sense. I hadn't considered the GT! I definitely need something there, otherwise air will just pass right underneath the radiator. Alright, let's assume option C. Where I get confused is there are 2 separate diagrams for air ducting, resulting in 2 different part numbers:

51712253303 #9
17212227344 #11

Do you know if I need both of these? I feel like just a simple picture of a Lightweight or a GT with the front bumper cover removed would answer 90% of my questions, but I can't find one anywhere.

I did come across the picture from a Z3M with an S54 radiator/oil cooler. Different chassis/part number for sure, but it looks like it has a piece BEHIND the radiator which blows my mind. Looks similar to 17212227344 so maybe I do need both? I know this is getting deep into the weeds here...

[sirhodjibob]

M3 GT underside. HMMMM
2013-04-29-14.54.10.jpg

[blckstrm]

M3 GT underside. HMMMM
2013-04-29-14.54.10.jpg

Hmm. I'd just recently read about that skid plate I see there.

My understanding was it was a skid plate / x-brace type of thing - not really for aero. And I can't get a feel for where it connects on the rear side.

[NeilM]

I have the metal LTW air duct (installed along with the GT adjustable splitter). Mine, P/N 51 71 2 268 673, came with what appear to be the plastic sides from the stock US plastic duct riveted to the sides. Note that in the second pic below that part number sticker is visible. In RealOEM it comes up as for the M3 LTW. Since it's not the same as the corresponding Euro part, I'm guessing that this was a hand assembled hybrid put together just for the LTW. (The mounting point reinforcements are mine.) Here's a vendor link to that P/N: https://www.ecstuning.com/b-genuine-...t/51712268673/

You'll also need the US stock flat plastic baffle that slips into the visible mounting grooves on either side. (Edit: you could obviously improvise this part if you don't have the original.) The baffle is necessary to prevent air from bypassing the radiator if you don't have the Euro oil cooler, which would be mounted under the radiator. The Euro cooler is nice for street use, but undersized for the track. It's also a bit vulnerable to off-track excursions in that under-radiator location.




Because I have retained the auxiliary electric fan and the A/C condenser, some of the details aren't visible, but here's the metal air duct installed on the car:




Edit: In the following photo you can see a couple of rivets under where the baffle must be. At this far remove (dates from 2007) I don't recall doing it, but I must have installed some kind of bracket to secure/reinforce the center span of the removable baffle.




And a view from the other side:



You can see that the rubber side sealing pieces fit normally. The last two photos were taken as part of my oil cooler install, so these are the only shots I have that really show the metal air duct.

A little story to go with: I may have been one of the first to lose the notorious stock plastic air duct. I owned a 1992 (non-VANOS) E36 325i, so right after the E36 M3 was introduced to the US market in 1995, a buddy from work and I decided to go and test drive this new M3 at lunchtime. It was a very hot day when I drove it out to a newly completed, and largely undiscovered, stretch of 4-lane highway I knew of, and I recall pointing out to my friend that the external temperature display and the speedo were both reading 100! Right at that moment there was a horrendous dragging/scraping noise from under the front of the car. I figured I'd run over some kind of road debris and pulled over on to the shoulder. Looking under the car I could see some kind of fairly large mass, so I reached under and dragged it out. Oh crap, a big plastic thing that must have been a part of the car! I stuffed all the bits into the trunk, and once we were back at the dealer explained what had happened. Fortunately they didn't seem too concerned.

The next year I bought my own 96 M3, and a year or two later the same thing happened on my car while I was on the highway in Canada on the way to the Mont Tremblant track. Once I got home I figured out what was going on, replaced the parts, and reinforced the mounting points with sheet metal as shown above. Same for the plastic wheel arch liners.

Neil
96 M3

Note edits.

[NeilM]

M3 GT underside. HMMMM
2013-04-29-14.54.10.jpg

I'd be astounded if that skid plate were a factory part.

Neil

[Braymond141]

I have the metal LTW air duct (installed along with the GT adjustable splitter). Mine, P/N 51 71 2 268 673, came with what appear to be the plastic sides from the stock US plastic duct riveted to the sides. Note that in the second pic below that part number sticker is visible. In RealOEM it comes up as for the M3 LTW. Since it's not the same as the corresponding Euro part, I'm guessing that this was a hand assembled hybrid put together just for the LTW. (The mounting point reinforcements are mine.) Here's a vendor link to that P/N: https://www.ecstuning.com/b-genuine-...t/51712268673/

You'll also need the US stock flat plastic baffle that slips into the visible mounting grooves on either side. (Edit: you could obviously improvise this part if you don't have the original.) The baffle is necessary to prevent air from bypassing the radiator if you don't have the Euro oil cooler, which would be mounted under the radiator. The Euro cooler is nice for street use, but undersized for the track. It's also a bit vulnerable to off-track excursions in that under-radiator location.




Because I have retained the auxiliary electric fan and the A/C condenser, some of the details aren't visible, but here's the metal air duct installed on the car:




Edit: In the following photo you can see a couple of rivets under where the baffle must be. At this far remove (dates from 2007) I don't recall doing it, but I must have installed some kind of bracket to secure/reinforce the center span of the removable baffle.




And a view from the other side:



You can see that the rubber side sealing pieces fit normally. The last two photos were taken as part of my oil cooler install, so these are the only shots I have that really show the metal air duct.

A little story to go with: I may have been one of the first to lose the notorious stock plastic air duct. I owned a 1992 (non-VANOS) E36 325i, so right after the E36 M3 was introduced to the US market in 1995, a buddy from work and I decided to go and test drive this new M3 at lunchtime. It was a very hot day when I drove it out to a newly completed, and largely undiscovered, stretch of 4-lane highway I knew of, and I recall pointing out to my friend that the external temperature display and the speedo were both reading 100! Right at that moment there was a horrendous dragging/scraping noise from under the front of the car. I figured I'd run over some kind of road debris and pulled over on to the shoulder. Looking under the car I could see some kind of fairly large mass, so I reached under and dragged it out. Oh crap, a big plastic thing that must have been a part of the car! I stuffed all the bits into the trunk, and once we were back at the dealer explained what had happened. Fortunately they didn't seem too concerned.

The next year I bought my own 96 M3, and a year or two later the same thing happened on my car while I was on the highway in Canada on the way to the Mont Tremblant track. Once I got home I figured out what was going on, replaced the parts, and reinforced the mounting points with sheet metal as shown above. Same for the plastic wheel arch liners.

Neil
96 M3

Note edits.

Neil,

There is no such thing as a "LTW" duct with plastic sides. You're talking about about the GT duct and the plastic sides are standard. These parts are indented for cars with oil coolers. The Lightweight has very few parts specific to it with almost everything coming from better European cars.

51712268673
Air duct

From:
03/01/1995
To:
-
Weight:
1.222 kg
Price:
$232.51

Part 51712268673 was found on the following E36 vehicles:

3' E36, M3, Coupe, S50, AUTO, USA, (BF03) : M Trim, front
3' E36, M3, Coupe, S50, AUTO, USA, (BF03) : Air duct
3' E36, M3, Coupe, S50, MANUAL, EUR, (BF91) : M Trim, front
3' E36, M3, Coupe, S50, MANUAL, EUR, (BF91) : Air duct
3' E36, M3, Coupe, S50, MANUAL, EUR, (BF92) : M Trim, front
3' E36, M3, Coupe, S50, MANUAL, EUR, (BF92) : Air duct
3' E36, M3, Coupe, S50, MANUAL, USA, (BF93) : M Trim, front
3' E36, M3, Coupe, S50, MANUAL, USA, (BF93) : Air duct
3' E36, M3, Coupe, S50, MANUAL, EUR, (BF99) : M Trim, front
3' E36, M3, Coupe, S50, MANUAL, EUR, (BF99) : Air duct
3' E36, M3, Coupe, S50, MANUAL, EUR, (BG91) : Air duct
3' E36, M3, Coupe, S50, MANUAL, EUR, (BG92) : Air duct
3' E36, M3, Coupe, S52, MANUAL, USA, (BG93) : Air duct

We're going to need a Lightweight owner to chime in or someone with experience working with the plastics on this specific area on a Lightweight.

[NeilM]

Neil,

There is no such thing as a "LTW" duct with plastic sides. You're talking about about the GT duct and the plastic sides are standard. These parts are indented for cars with oil coolers. The Lightweight has very few parts specific to it with almost everything coming from better European cars.

I don't doubt that this is technically correct. However RealOEM lists it as that, and vendors sell it as that. The GT from which it was sourced wasn't sold in this market. So from our US market standpoint it's the LTW duct. I'm guessing that its presence on the LTW was due to the GT adjustable splitter. Did the LTW come with an oil cooler? I'm thinking not, but could be wrong. I used to have several friends with LTWs, but they've all cashed out, one way or the other.

I'm curious about that RealOEM list including supposed other US models using this duct. Following those links, all but one actually go to the LTW itself, and the only one that doesn't is for the M trim with the adjustable splitter, which I don't think was ever sold here other than on the LTW.

Neil

[Braymond141]

I don't doubt that this is technically correct. However RealOEM lists it as that, and vendors sell it as that. The GT from which it was sourced wasn't sold in this market. So from our US market standpoint it's the LTW duct. I'm guessing that its presence on the LTW was due to the GT adjustable splitter. Did the LTW come with an oil cooler? I'm thinking not, but could be wrong. I used to have several friends with LTWs, but they've all cashed out, one way or the other.

I'm curious about that RealOEM mention of supposed other US models using this duct. Have you actually come across any instances? I haven't.

Neil

RealOEM does not list it as "Lightweight". It is listed as Air Duct. Regardless, if a part is special and shared, it only designates packages based on the VIN you entered (and/or by region). The carbon console is the perfect example. If you search on RealOEM with a Lightweight VIN, you see the carbon console and it says "INDIVIDUAL SERIES 95 M3 LIGHT-WEIGHT" PN: 51162261318. 51162261318 is not specific to the Lightweight and if you search for it using a Euro car VIN, it doesn't say "For Lightweight" because that car doesn't exist in that market. BMW does this so the dotard at the parts counter sells you the right part in your region, NOT because the part is necessarily specific to the text written above it. These mistakes lead to guys like PTGLTW spouting all over the internet that people are selling fake Lightweight carbon consoles that came from an M3 GT (THE SAME PART) because he doesn't understand how part numbers work.



The only reason vendors in the US throw "LTW" around is to catch search inquiries.

The Lightweight does not use an oil cooler. The undertray he is using came from a car with an oil cooler. The tray itself is NOT specific to the Lightweight. We need someone to chime in with how it is fit on the US car as RealOEM does not state anything special was used. The issue is 17112227690, not the undertray.

Maybe BMW used the plastic shroud from the oil cooler setup (17212227344 ) just without the oil cooler? Or maybe they just crammed 690 in there.

[pbonsalb]

This guy claims to have a lightweight tray for sale:

https://www.bimmerforums.com/forum/s...parts-for-sale

[Braymond141]

This guy claims to have a lightweight tray for sale:

https://www.bimmerforums.com/forum/s...parts-for-sale

That's the aero piece, not the undertray in question here.

[sirhodjibob]

I'd be astounded if that skid plate were a factory part.

Neil

I believe it is actually. Part #51718209093. As I recall it doesn't work with the factory X brace though, but 51712491567 does

[sirhodjibob]

YOU GUYS

https://youtu.be/N3lC8xM624Q?t=1667

Ok so based on this YouTube video of an E36 M3 GT in Turkey, 51712253303 is the correct air duct that sits on top of 51712268673 if you want to run the factory oil cooler. Still not sure where 17212227344 fits in relation, but based on the pictures below it may line up with the 3 holes at the rear of the air duct. I wonder if the oil cooler itself has some attachment point to hold it too?

17212227344:


51712268673


Still not sure what the E36 M3 Lightweight does though given its lack of oil cooler.

[sirhodjibob]

Did you know there's supposed to be a rubber buffer installed on the X brace? 11811095700. Who knew! The things you find searching Russian bmw forums at 1AM. http://www.uucmotorwerks.com/html_te...ace_buffer.htm

51718156259 may be the part on the Lightweight. I sent a note to EAG to see if they have a picture. If anyone knows does they do.

[Cos270]

Did you know there's supposed to be a rubber buffer installed on the X brace? 11811095700. Who knew! The things you find searching Russian bmw forums at 1AM. http://www.uucmotorwerks.com/html_te...ace_buffer.htm

51718156259 may be the part on the Lightweight. I sent a note to EAG to see if they have a picture. If anyone knows does they do.

A note on the rubber buffer. It will only fit on early versions of the X-brace that has the slot/holes to accept it. I'm paranoid, so of course I bought one before I installed my x-brace, only to find out that my x brace is a later model and will not accept it. If anyone is interested, I'm happy to donate it if you cover the cost of shipping.

[Braymond141]

Did you know there's supposed to be a rubber buffer installed on the X brace? 11811095700. Who knew! The things you find searching Russian bmw forums at 1AM. http://www.uucmotorwerks.com/html_te...ace_buffer.htm

51718156259 may be the part on the Lightweight. I sent a note to EAG to see if they have a picture. If anyone knows does they do.

UUC has had the purpose of it listed on their site for decades.

[Hova]

That rubber buffer is often regarded as not needed on here when I first installed my Xbrace. I had newish motor mounts and new tranny mounts, and I noticed that my oil pan made contact with that piece of rubber, so it does offer some help at the limits.

[Cos270]

That rubber buffer is often regarded as not needed on here when I first installed my Xbrace. I had newish motor mounts and new tranny mounts, and I noticed that my oil pan made contact with that piece of rubber, so it does offer some help at the limits.

I threw mine on right before I changed my engine and trans mounts, just to see if the caution was well-advised. Before the mounts were replaced, the brace was about 1/4in away from making contact with the oil pan. After replacing the mounts, I now have a good 3/4 - 1 in of clearance. I don't plan on tracking the car, and I've already refreshed the front suspension (minus the front subframe bushings) so I'm not concerned with the brace hitting the pan. But for those with worn mounts or that plan on tracking their cars, I think its a worthwhile precaution.

[NeilM]

Yeah, I tracked down that rubber bumper thingy years ago when I bought the X-brace.
Of course then it didn't fit mine.

I believe it is actually. Part #51718209093. As I recall it doesn't work with the factory X brace though, but 51712491567 does

Well, I've been astounded before. But it doesn't look nearly over-engineered enough to be a real BMW part.

Neil

[xdarwin13]

Hi everyone,

I'm not an expert here by any means, but wanted to chime in. My old "stockish" LTW had the aluminum under tray, unfortunately I don't have any pictures with the bumper off, but I do have a few where it can be seen:

20160711_161248.jpg

EAG should definitely be able to provide some guidance. My current LTW wasn't sold new until 1997 and was then further modified by PTG in the late 90's. They installed a Euro/Group N stamped S50B30, which it retains today. Unfortunately PTG didn't seem to concern themselves with plastics/cosmetics then, and I was less than thrilled with the way some of the front end plastics fit, so I had EAG completely redo it. We scrounged for new parts as I wanted it perfect and got a few from Europe using the GT as a reference. Having the oil cooler also allows you to run the super cool front baffle (it sits on top of the aluminum tray, in front of the cooler) with this setup, which to me is one of the best parts. During this project, they were able to get it to 99% of the GT setup... we couldn't get to 100% as we were waiting on the Euro intake snorkel (it draws air from the drivers side of the radiator housing and also connects to the drivers side bumper air duct). Well after waiting many months, the snorkel arrived and once installed it will complete the Euro setup. I'd be happy to provide any of the part numbers we used, but want to clarify that any tech questions should be relayed to the EAG team. I've done many projects with them, they are great and did quite a bit of research to come up with the items needed for this setup.

Here is a photo of the new parts prior to going on the car (and old ones coming off), I have some other photos which I can provide if needed:

IMG_20191213_132528.jpg

[sirhodjibob]

Oh wow, I think I've seen your car in one of EAG's youtube videos, if it's the one I'm thinking of with the 6 speed and Moton suspension it's badass! Thank you for these pictures, that pretty much sums up everything you need!

I got in touch with Mike at EAG who was EXTREMELY helpful. I seriously can't thank him enough (you guys here who helped too, thank you).

It looks like 51718135939 is indeed the missing piece (the skinny black piece on the left side of xdarwin13's 2nd picture) that slots between the air duct and the radiator. I think it was only like $12, so I ordered that as well as the air ducting for the oil cooler (51712253303). I ordered 17212227344 as well (it was around $30), still not 100% about that one but I'll give it a go. Also ordered all the Euro underpanels too. I'll post once I get everything put together.

[xdarwin13]

Awesome, happy to help. BTW, Mike is the best! Glad you were able to connect with him.