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M52TU Turbo Swapped MX5 (No that's not a joke or a typo)
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Discussion Starter · #21 · (Edited)
Ok this is more for my benefit than anyone else's but I thought I'd throw together a sort of To-Do list of what needs to be done still on the car

TO-DO

Finish exhaust design

Finish wastegate piping and feed back into exhaust

Fully weld exhaust and wastegate

Wrap wastegate and exhaust

Finish welding on manifold

Make turbo oil feed line

Finish turbo oil return and weld fitting into oil pan

Make turbo water lines

Make upper radiator mounts


Finish mock up of engine coolant hoses and lines for heater core

Make coolant reservoir/header tank/expansion tank.

Make fuel lines

Install Fuel Pump

Finish lower section of core support


Make Intercooler piping

Modify clutch pedal assembly to fit BMW master cylinder

Make new clutch line

Finish welding diff mounts

Make mock up axle/driveshaft


Get custom axle/driveshafts made

Get prop shaft shortened

Paint new steel in engine bay & chassis legs

Paint/Powder coat modified subframes

Paint/Powder coat gearbox cross member

De-Power steering rack/Weld pinion

Replace outer tie rod ends on steering rack

Wire up engine with BMW harness and modify to work with existing Mazda harness

Change all fluids/Service engine, gearbox and diff

Install ABS sensor in front wheel hub to use for speedo

Wire up SGI-100BT to correct tacho signal and generate speedo signal for OEM gauge cluster

I'll no doubt have things to add to this when I remember them and I'll cross them off as I go along and this is in no particular order.
 

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M52TU Turbo Swapped MX5 (No that's not a joke or a typo)
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Discussion Starter · #22 ·
So no new progress this evening as was working on my brothers Mini again (turns out the clutch fork had sheered off along the weld line, first time I've ever seen that). Whilst that was happening I found that the 7/16 UNF adapter I had for the turbo was not the right one. After some research I'm now 99% sure I've found and ordered the right one which will hopefully arrive early next week. I think the correct fitting is a 7/16-24 UNeF fitting which turns out is a standard option on Garrett GT28 and GT30 turbos so It probably makes sense.

My car is now back on the lift so hopefully tomorrow and over the weekend I can make some more progress.
 

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M52TU Turbo Swapped MX5 (No that's not a joke or a typo)
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Discussion Starter · #23 ·
On Friday evening I decided to make some changes to the Fore/Aft angle of the engine in order to improve clearances around the drive line and on top off the engine. When I installed the engine I was aiming for exactly -3.0 Degrees (lower at the back) but in the end I ended up about 0.5 degrees of this at at 3.5 degrees. I can't exactly remember If I settled on this angle or If it moved whilst making the gearbox mount but I decided to change it.

After some testing and tweaking I found that changing the engine angle up by 0.7-0.8 moved the rear of the gearbox up by 23mm and changed the prop shaft angle up enough that meant the diff would sit a lot high in the rear. It also meant that I no longer had any clearance issues with the bonnet so I went ahead with this change. It does obviously mean that I'll need to make a new gearbox mount, centre bearing mount and modify the rear subframe to get the diff to sit higher.

Well on Friday night I worked until about 1:00AM and got the new gearbox mount smashed out, It holds the gearbox in the new position but it also allows a lot more room for the exhaust to get past which was previously a bit of an issue as the exhaust was the lowest point on the car. The current Gearbox mount is still only a prototype as It requires 2 people to get it in and out of the car so I'm gonna re-think that at some point.

On Saturday I started work on the prop shaft centre bearing mount and again with the new angle it means I can mount the bearing the correct way around and don't need to put it at an angle. However whilst I was shaping part of the new mount on the grinder I had a bit of a mishap with the big belt grinder. Long story short, I was applying too much pressure and the part dug in and fired across the room leaving my hand to make contact with the belt. Nothing too serious but have some very deep abrasions on my knuckles but it did put an end to my weekend working on the car as I couldn't move fingers after they'd swollen up.

Well Yesterday I was able to do some work on the car and as my hand is still pretty stiff I decided that now was a good time to run the water lines and have a look at the turbo oil feed. The water lines are simple enough as I'm just using barbed banjo's on the turbo with rubber hose. Now most M52 guys seem to run the water lines from the lines that normally run to the throttle body as coolant though the throttle body isn't required. Well the problem is that on the M52TU (technical Update) engine BMW decided to remove the coolant to the throttle body so I don't have that option. It seems that the M52TU and M54 guys fall into one of 2 camps when turboing there engines, either they don't bother with water lines and then bitch about how there turbo burnt itself out and mystically gave up after 7000 miles or they run a feed from the lower rad hose and then drain to the block drain plug.

I opted for the later option and had order all of the fittings last week so as they arrived yesterday I got started. It's pretty damn tight around the turbo but everything fits without making contact and everything is far enough away from the manifold and downpipe that I'm not worried about them melting.

as for the oil feed, I'd originally bought a 90 degree fitting in case I needed to use the banjo on top of the turbo but as I have now got the correct adapter I don't need the angles fitting. In fact there just isn't room to use so I need to order a straight fitting for the turbo and then I can finish the oil feed line.

I didn't take any pictures yesterday as there was nothing exciting, Hopefully this week I'll get round to finishing the prop mount and moving the diff.
 

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Discussion Starter · #24 ·
I had some time in the workshop this evening so I decided to cross a few things off my list. I'd kinda been putting off finishing the lower core support section as I wasn't entirely sure how I was going to do it and then randomly It came to me whilst I was sat at home; I'd also been putting it off as I couldn't be bothered to get the tube bender setup. I ended up having no choice but to get the bender out and this was the outcome:

07fb17_4cbf3e0257e94dfd9a30880c6f5a55bf~


07fb17_b293ecf25221444eb060d0270e47d948~
07fb17_f97a12c963194593b98311780f035002~


I'll probably tweak it slightly and change the sharp 90 degrees bit that links the 2 parallel bars for a nice curved piece now that I have the tube bender setup. So the short side of the double ended cup thingy welds to the side of the chassis leg and has a captive nut on the inside of it so that the longer part can bolt to it making the whole lower frame removable.

After that was sorted I decided to finish up the turbo oil feed line as the straight fitting I ordered arrived this morning. With the straight fitting on the turbo everything fits nicely so that's another thing off the list.

Next up I worked on getting the downpipe to fit again with the new engine position, with all the extra space I was able to move the flex joint up to sit alongside the gearbox.

07fb17_525799c1c6f547f6afaf8cad1c9bee5e~


07fb17_99bcb3163bd44bcda06ab6160e07aac5~


I'm back in the workshop tomorrow so I'll carry on with the exhaust and may start moving the diff if I have time
 

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M52TU Turbo Swapped MX5 (No that's not a joke or a typo)
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Discussion Starter · #25 ·
I started Saturday by finishing the new prop centre bearing mount so that I could work out how much I need to move the diff. When I first mounted the diff I had angle the propshaft up by 1 degree in order for it not to be scrapping the floor. This time I figured I'd try and keep everything nice and parallel to reduce the risk of driveline vibration.

Well with the Prop firmly mounted into the car I broke out the laser and did some maths and measuring to work out that I needed to move the diff up by 60mm. I couldn't be bothered to try and cut the subframe up whilst it was still in the car and as I have a spare in the workshop I decided to use that instead. After having a look at the subframe and taking some measurements I decided that to get the diff high enough I'd have to cut about 80% of the rear bar out so figured I'd just cut the entire thing out and replace it with new steel.

First thing first though I needed to brace the subframe so that it didn't Taco out of shape as soon as it was cut and then I cut a big old chunk out of it.

07fb17_bd93b6dbe0c246178e3ed0309af624f3~
07fb17_3d2fbd10cb7d45488c5c56d185d72685~


Unfortunately I got a bit carried away and didn't really take any pictures but long story short, I bent some tube, plasma cut some plate, ground some rust, welded some steel and sprayed some paint and I ended up with this

07fb17_8cb612f2d40e4a1385663e28bd42aa57~


07fb17_01326b5da6c84a749ef248c0b560a224~


I didn't get chance to chuck the diff back in as the paint was still wet but hopefully tomorrow I can chuck the diff in and chuck it into the car. I'll probably make a brace to go across the underside to replace the crusty old OEM one as well.
 

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Discussion Starter · #26 ·
So this is probably not the Ideal place for a technical discussion but didn't want to a whole new post for something so minor. So someone recently suggested adding a mini sump to the bottom of the turbo to help with any oil foaming. I wanted to get people thoughts on whether it was worthwhile or if I should just send it and see what happens (I'm happy with both options). I know that guys that run scavenge pumps often do this on their turbos.

so should I add a shallow mini sump to the bottom of the turbo to help oil drainage or just crack on without and send it?
 

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Discussion Starter · #27 ·
To clarify what I was talking about I threw something together in fusion (obviously the edges would get seam welded):

The idea is that the hole on the top will have an AN fitting (or barb) to run a vent probably back to a catch can and then the angled hole on the bottom will take an AN fitting (or barb) to drain somewhere into the oil pan



The benefit is that is may help with any oil foaming issues and it may help with routing the oil drain.

The downside is that I've got to design and fabricate it and there's no guarantee that it will work so could be a huge waste of time.
 

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Discussion Starter · #28 ·
Ok so over the past few days I've been wrestling with diffs and subframes. First up I threw the diff in the modified subframe and all looked good except it looked like it maybe sat a bit too high in the subframe. My concern was the axles contacting the subframe at full compression but I couldn't be sure without throwing it all in the car.



So I went about taking the whole rear subframe and suspension out of the car and it didn't want to play nicely. The 2 Bolts on the subframe came out nice and easy without much of a fight but the 4 studs would not move. I broke them loose with the breaker bar and then tried the impact to get them off but nothing, so I switched to the air impact and still nothing. I drowned them in WD-40 and still nothing, so I applied some heat... a lot of heat... with an oxy-propane torch and after getting them nice and toasty and burning all the crap off threads I was able to spin them off with the air impact. After that I unbolted the arms from the subframe and took the entire suspension assembly off as a single piece and moved it over to the modified subframe.



at full compression the axle did actually clear the subframe... just. So I moved on and bolted it all back into the car without any real drama's initially. I realised though that the flange at the front of the diff was making contact with the metal heat shield thing under the fuel tank. I took some further measurements and decided that I could drop the diff down by 20mm and still be comfortably in the 1-3degrees needed to keep the propshaft joints happy. I pulled it back out modified the mounts and put it back in for a test fit:





The angle of the photo makes it look tighter than it really is but it fits. All in all the diff is 40mm higher than when I originally mounted it and there is still enough room to get the exhaust round it so I'm happy. I need to drop it all out again and finish welding the new mounts so I'll probably do that tonight. Once that is all done I can take final measurements for the prop shaft and get that sent off and I can make the mock up axle to send off. Once that's done everything mechanical is kind of out of the way!

Further along in my project plan I will be overhauling all of the suspension in this car so I think at that point I'll likely make new tubular subframes to replace the modified ones (front and back)
 

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Discussion Starter · #29 ·
So the new axle adapter plates arrived today. I had these made from S355J2 which is a medium tensile steel with good Impact and shock resistant properties even at massively sub zero temperatures meaning it should up nicely as part of the drivetrain. I now need to tap all of the outer ring of holes so that the axle can bolt up to them.

 

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Happily expanding the To Do list since 1997
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This is amazing work. The hub and axle that won't even separate in a large press is giving me flashbacks. On the oil scavenging issue, how much drop in height have you got to play with below the turbo to the expected oil level in the sump? It looks pretty tight. PS Hope your knuckles are okay.
 

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Discussion Starter · #32 ·
This is looking very interesting.

Sorry if I missed it, but is there any particular reason you went for this engine? Or just 'because'?
I don't think I ever said why I decided on this engine to be honest. it's a combination of things but also a just because thing. So I'd always wanted to cram something bigger into an MX5 an originally I'd looked into a 1UZ and decided against it due to the lack of bolt on manual gearbox options, I also looked at the old BMW x5 V8 but ruled it out for the same reason. I've always loved inline 6 engines and I've already done RB swaps in things in the past so wanted to do something different (also they are heavy), I didn't want to go down the JZ route as they are over priced, over rated and also heavy. So I decided to look at other options, originally I wanted to swap in an N54 from an e92 but between them being mad expensive and overly complicated with all the direct injection crap I'd kind of ruled it out and given up on the idea. Then randomly one day ebay popped up a suggestion for an M52TU, so I did a bunch of research and decided that it might be an option at some point. Then a few weeks later I was dinner with my parents and my mum randomly asked if I had anything else planned for the car, I briefly explained it and she convinced me to do it 😂 so I like to tell people that this whole project is her fault

P.S sorry for the rambling story
 

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Discussion Starter · #33 ·
This is amazing work. The hub and axle that won't even separate in a large press is giving me flashbacks. On the oil scavenging issue, how much drop in height have you got to play with below the turbo to the expected oil level in the sump? It looks pretty tight. PS Hope your knuckles are okay.
The hub and axle debacle still gets to me every time I see them sat there! So the oil pan is rear sump and the rest of the pan is less than 20mm deep so I'm assuming that the oil level will be in the sump section somewhere. There is probably less than 3 inches of drop to make the return line meet the oil pan, If I wasn't being tight (and didn't have concerns about that longevity of electric oil scavenge pumps) I would use an oil scavenge pump.

Yeah they have healed nicely and I now most of the mobility back again which is nice😃
 

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I don't think I ever said why I decided on this engine to be honest. it's a combination of things but also a just because thing. So I'd always wanted to cram something bigger into an MX5 an originally I'd looked into a 1UZ and decided against it due to the lack of bolt on manual gearbox options, I also looked at the old BMW x5 V8 but ruled it out for the same reason. I've always loved inline 6 engines and I've already done RB swaps in things in the past so wanted to do something different (also they are heavy), I didn't want to go down the JZ route as they are over priced, over rated and also heavy. So I decided to look at other options, originally I wanted to swap in an N54 from an e92 but between them being mad expensive and overly complicated with all the direct injection crap I'd kind of ruled it out and given up on the idea. Then randomly one day ebay popped up a suggestion for an M52TU, so I did a bunch of research and decided that it might be an option at some point. Then a few weeks later I was dinner with my parents and my mum randomly asked if I had anything else planned for the car, I briefly explained it and she convinced me to do it 😂 so I like to tell people that this whole project is her fault

P.S sorry for the rambling story
I have just put my m135i up for sale with the N55 - and i have always thought it would be a lovely swap, but assumed an inline 6 might be a bit tight.
Engine was the best bit of the car - we are moving to the US in a few weeks and I like it so much I am thinking about repalcing it with the E82 135 over there (The F20 hatch doesn't exist there unfortunately otherwise I think i woudl have taken mine with me)
Think you would need to be very lucky to find a written off one to grab the drivetrain from - but likely to be expensive. Also, being a bit newer electrics may be more comlicated.
While a V8 in an mx5 is hilarious, it feels like over kill. I've always thought a 6 pot is the sweetspot for the size of the car.

Watching with interest...
 

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Banish a little rust a day people
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Some serious fab work going into this, looking good.
 

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Discussion Starter · #36 ·
It's been a good productive few days, I spent Friday night and most of Saturday working on the clutch pedal assembly. It took a bit of trial and error but I managed to install the BMW master cylinder on to MX5 clutch pedal assembly. Now why go to the trouble to fit a BMW clutch master? Well because of the engine angle there is now an engine where the clutch master would have been and the BMW clutch masters sit inside the footwell of the car. Originally I'd tried to mount the master on the right of the pedal but when I test fitted it, I found that it clashed with the steering column so had to move it to the left side and it ended up working out much better.




The pedal still has a full range of motion and it also fully actuates the clutch master, I'd taken a bunch of measurements from the pedal BMW pedal box to get the angles and offsets correct. So I've got get a line made up that goes from BMW's quick disconnect fitting on the back of the master to a standard M10x1.0 fitting for the clutch slave.

After that I decided to get the fuel system sorted out, so I ran new AN-6 stainless braided Teflon lines for the feed an return and I needed to route them round to the opposite side of the engine bay to avoid the exhaust so they run up into the tunnel and over the top as far away from the exhaust as possible. I may build a steel heat shield to cover them in the tunnel (also to protect them somewhat from anything hitting them). The lines are all held in with rubber lined P-clips so they are nice and tight to the tunnel and nice and secure.

After that was out of the way I decided to get the fuel pump installed. This was nice an straight forward, when I ordered the pump I'd made sure that the dimensions where similar enough to the stock pump that it should just bolt in and it did. The only thing that I had to do was splice the connector so cut and joined the wires (I crimped the wires instead of soldering them as its supposedly better but We'll see) and then cover in electrical tape and fuel resistant heat shrink.



I stupidly didn't order a replacement fuel sock and the one that came with the AEM pump wouldn't have fit so I threw the old one on. I'll have to pull it back out at some point and change it as It's probably the 20+ year old original one.

I've got a fresh cylinder of Argon so I'll probably crack on with welding up the last bits of the subframe and getting the exhaust welded up.
 

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Discussion Starter · #38 ·
"After that I decided to get the fuel system sorted out"

That took me days to sort out, not just one job over a weekend if other jobs. Ffs.
well it’s a lot easier when you run all new lines, also I’d been planning the route well in advance
 

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Discussion Starter · #39 ·
So I didn't really get much time on the car yesterday but I did have enough time to pull the diff back out and spray some paint on the subframe where I had to make changes. I also designed and plasma cut the top radiator brackets so I'll get those finished today most likely. I also measured up for the new clutch line, Originally I'd wanted to make this myself but it seems that the BMW quick disconnect clutch hose fitting is only available as a crimp on fitting. So I did some searching and found a company called BRT Motorsport that does custom lines made to order and they had the BMW fittings in stock (No affiliation or anything just found them on google). I ordered a 1250mm braided line with a BMW fitting one end and a 90degree M10x1.0 swivel fitting the other end. The order total came to about £33 for a fully assembled custom braided line which is less than I've paid for "off the shelf" braided clutch lines in the past. The braided lines you get for BMW's only replace the rubber flex section down by the slave cylinder which is only about 150mm long and costs range from about £30-£60 for just that bit so £33 is a cracking deal!

Hopefully that will arrive later this week and I can cross another thing off of the list and that will be the clutch hydraulics done
 

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Discussion Starter · #40 ·
So I need to order the little circlip that holds the clutch line into the back of the master cylinder, I did some research and found the part number (21521165451) then I searched the part and found that it costs anywhere up to about £20 for a tiny little circlip!

Holy crap, what the hell 😂

Best I could find without ordering from eastern Europe was about £15 (It would have been about £12 from Lithuania or Latvia without any taxes applied). I guess I best get used to stupidly expensive BMW specific parts...

What's even more annoying is when we replaced the gearbox on my brothers mini last week, the new gearbox came with a slave cylinder still attached to it and it had a circlip still in it... Its the exact same part number but I threw the whole thing away without thinking 🤬
 
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