After much deliberation, reviewing countless threads across multiple forums, and mapping out every step of what was involved with swapping turbos, I just couldn’t overcome the scenario of going through all the labor of replacing my twin turbos with another set of twin turbos only to discover a failure or wastegate rattle shortly down the road. The GC Lites I had in my possession prior may have ended up not failing, but there were multiple confirmed cases of defective turbines within that lineup with no real clarification on what happened. That personally shook my confidence in the whole situation the second go around. A failure of that magnitude after investing the time and money of tackling that type of install would be heartbreaking, and not something I was willing to risk if at all possible. Even if the turbos were warrantied, the labor involved would be incredible, and if they’d failed once, what’s to say they wouldn’t again?
Looking past the twin turbos themselves, silicone inlets and outlets were both areas of concern of mine. The thought of the miserable install associated with 2” driver’s side inlets plus the worry of manifold heat melting the silicone outlets were the straw that broke the camel’s back. Since back when I owned my 535i, I had ambitions of adding a top mount single turbo to an N54 equipped E82, and it was time to make that happen. A twin scroll bottom mount seemed like a nice alternative to going all out top mount, but o2 sensors seemed to be even more at risk and I’d still have difficult reaching the turbo if anything ever needed addressed. Plus when I was shopping, there hadn’t been much long term feedback on any of the newer kits.
After getting in touch with a few different vendors, I eventually settled on a top mount single kit from ACF featuring a Precision 6062 Ball Bearing Gen2 turbocharger (with a polished compressor as the only option). I decided to forego the ceramic coating and recirculated dump pipes to keep costs in check, and because I prefer open dumps and planned on using DEI exhaust wrap anyways. Ultimately I went with ACF because a) I liked the ACF manifold design & downpipe sizes the best out of all the top mount kits, b) it seemed to include more robust components more than the Docrace alternative, and c) was slightly more affordable than others with a ball bearing option coming in at less than $5,000. The 6062 configuration with ACF’s proven twin scroll manifold should provide super-quick spool and as much power as my fuel system can throw at it. Plus if things go awry with the turbo, it’s right up top and easily serviceable. Of course single turbos come with their own set of heat problems, but hopefully I can counteract that with carefulness.
Once my mind was made up, Anthony & Payam quickly answered the few remaining questions I had, gave me a two week lead time, and I made payment soon after. ACF has been subject to criticism with how quickly they can get a kit in your hands, but I wasn’t in a huge hurry and had made up my mind to put my faith in Anthony’s ability to deliver. So how accurate was that two week lead time? From the time I made payment to the time it was put in the mail was 21 days. I’m on the other side of the country from Anthony, so including shipping it took a total of 28 days from payment until I had everything in hand and it was well worth it. I’ll let the pictures and video do the talking, but the craftsmanship is truly impressive to see in person.
In the meantime, I had a lot of other areas that I wanted to address and parts I needed to order. First and foremost, was my clutch and flywheel combo. I had managed to take my 135i over the one hundred thousand mile mark (fifty thousand of that tuned on E85 at close to 20psi) and my stock DMFW and clutch were still holding up just fine. Back when I had new hybrids in hand, I had planned on a new DMFW + 335is/550i clutch to keep things simple with a stock feel, but ultimately it was destined to die a quick life at my intended single turbo power levels. I hated the idea of the increased noise and NVH of a SMFW, but hated the idea of misfires even more, so cue up the trusted MFactory Steel SMFW. I was however, curious about the performance advantages of installing a lightweight flywheel and how it affected feel when rev matching. If it was better than the heavy DMFW in that regards, I could come around to enjoy the SMFW idea quickly. The Spec Stage 2+ clutch seemed to be the best bet for a daily driven car around the 550TQ mark, and would last longer than the slightly stronger 3+. Unfortunately, jumping to any of the Spec + options, meant it was a much more expensive setup, but a necessary one. Add in flywheel bolts, pressure plate screws, a brass clutch fork pivot pin, an OEM clutch alignment tool and a service kit with new fluids/plugs, and I was looking at another $1450 on top of the ST kit to transfer all the new power efficiently.
I already had MHD on hand to try and combat the SMFW rattle, so I could raise the idle to counteract this somewhat. In fact, I’d been experimenting with my stock clutch/flywheel by raising the idle to 950RPM for a few months prior. A lot of people are hesitant to do this for some reason, but besides the slightly louder idle decibels, on a 6MT, the car idles smoother and engages the clutch easier as the RPMs aren’t dipping so low. This should in theory make the Spec 2+ easier to engage while eliminating the majority of the unwanted noise.
There was also the issue of single turbo kits and their tendency of killing standard o2 sensors prematurely because of the increased pressure and heat. $425 to avoid these headaches with the ADV o2 sensors. More boost required a 3.5 BAR TMAP + BMS adapter, another $125. My standard 7” upgraded FMIC from VRSF would no longer keep IATs in check during the hot South Carolina summers, so add in the humongous Phoenix Race FMIC, another $500.
It only made sense to do bunch of maintenance items at the same time since I’d be dropping the subframe and have access to some items I wouldn’t normally have access to (and hadn’t done already). These would include: OEM engine mounts (I opted to not go with the 335is or 034 Motorsport versions and just stick with stock), an oil pan gasket & bolts, downpipe gasket & bolts, rear main seal, a rear shaft seal for my differential that has been seeping some fluid, oil level sensor o-ring, a fresh set of NGK 95770 plugs and Delphi coils, Motul 5W40 and a Mann filter, a budget walnut blast setup, BMW coolant and new aluminum water pump bolts. Another $860.
Add in an engine support bar, a few specialty tools, the aluminum BMW Performance strut brace for bling that I bought for a decent price on eBay, supplies to heat wrap the ACF top mount kit hot side components properly and my total money spent on going single turbo tallied to more than $9,100 without any custom tuning and performing all the labor myself. The price of going single turbo the right way IS NOT for the faint of heart by any means. I was once told between cheap, fast, and reliable, you can only have two. I chose the two latter options. Here’s my total cost breakdown below, every single penny:
ACF 6062BB Top Mount Single Turbo Kit with polished compressor housing - $5000.00 ACF
ADV o2 Sensors - $425.00 CHRIS
Phoenix Race FMIC - $499.01 N54TUNING
3.5 BAR TMAP Sensor - $89.39 ECS
TMAP Adapter - $32.50 BMS
Downpipe Gaskets - $25.90 ECS
Stainless Tie Wraps - $16.67 AMAZON
DEI Exhaust Wrap - $44.88 AMAZON
6 FT of DEI Heat Protection Sleeving - $52.58 AMAZON
DOCRace Single Turbo Heat Shield - $120.00 DOCRACE
Exhaust Manifold Studs x16 - $15.84 ECS
Exhaust Manifold Nuts x 11 - $38.50 ECS
Exhaust Gaskets - $23.94 ECS
Intake Gaskets - $15.95 ECS
Throttle Body Gasket - $9.89 ECS
335D Intake Duct - $39.68 ECS
Replacement Coolant Pipe & Oil Supply O-rings - $33.51 ECS
MFactory Steel SMFW - $515.36 ECS
Spec Clutch 2+ = $809.10 TOPGEAR
Manual Transmission Service Kit - $42.58 ECS
Clutch Alignment Tool - $25.58 ECS
ECS Clutch Fork Pivot Pin - $34.95 ECS
Pressure Plate Screws - $11.28 ECS
Aluminum Bolt Set for Bellhousing - $10.95 ECS
8 Flywheel Bolts - $22.40 ECS
OEM Flywheel Lock Tool - $53.89 FCPEuro
OEM Engine Mounts & Bolts - $174.98 ECS
Oil Change Kit - $74.44 ECS
Delphi OEM Coils - $278.52 ECS
NGK 95770 - $79.13 AMAZON
BimmerHelp Blasting Attachment & Wand - $68.50 BIMMERHELP
Harbor Freight Walnut Blasting Supplies - $78.78 HARBOR FREIGHT
Amazon Engine Support Bar - $56.99 AMAZON
BMW Coolant/Water Pump Bolts - $35.62 ECS
Rear Crankshaft Seal - $34.61 ECS
Oil Pan Bolt Set - $29.12 ECS
Oil Pan Gasket - $41.21 ECS
Rear Shaft Seal - $12.25 ECS
Oil Level Sensor O-Ring - $6.39 ECS
Redline Power Steering Fluid - $11.49 ECS
OEM BMW Performance Aluminum Strut Brace - $150.00 EBAY
TOTAL = $9,141.36
To put that in perspective, I could probably buy a 335i in decent condition for that kind of coin. That also means on top of the $5,000 cost of the complete single turbo kit, it took over $4,100 in accompanying mods to get everything else up to par in my eyes, and I already had a decent amount of those components necessary to go single turbo installed prior to all of this like the JB4 + MHD, stage 2 LPFP, upgraded charge pipe, Tial BOV with upgraded vacuum source, Index 12 injectors, etc. I can probably net close to $1,500 from selling my existing twin turbo setup parts to help offset costs somewhat, but is still an enormous investment. So what does dropping over nine thousand dollars on your N54 equipped ride get you? A lot, actually.
Before I began to totally tear the car apart for the extraordinary amount of work I was about to embark on, I thought it would be beneficial to have some baseline readings. Just a few weeks earlier I’d discovered that there was small performance shop just a few miles away equipped with a Dynojet. It only made sense to make an appointment and get some baseline numbers on the stock twins.
It only took getting into boost once before we realized we needed to add a few extra straps.
These two runs were on E40 fuel on the E85 BMS BEF on map 7. My poor, tired, and smoking turbos were targeting around 19.7psi for both runs, but were only managing to hit around 17psi and tapering off to around 14psi near redline. As instructed by Terry over on N54Tech, these runs were done in 4th gear from 2,000 to 7,000 RPM. Smoothing is set to 5. I did notice where correction was set to SAE, instead of the STD Terry suggested.
Run 1 was the run I spun the tires, run 2 resulted in 395HP & 406TQ, run 3 resulted in 393HP & 407TQ.
I drove the car straight back to the garage where the single turbo conversion and got to work. I already had all the new parts to go in, as well as all the tools I’d need, neatly laid out. I started with a wide open space so I could sprawl out a bit.
Using the impressive Esco jacks I recently picked up, I was able to get the car high up off the ground, since I’d be spending plenty of time underneath it over the next few weeks. And because I wanted to use a creeper, so some extra clearance was needed.
Back in the summer of 2016 as the 135i was about to turn over 60,000 miles, I was forced to replace the aging Michelin Pilot Sport tires that I bought the car with. Because I drive my car so much, longevity was just as important as performance for me. I spent a few days digging through TireRack reviews before deciding on the 235/265 Hankook Ventus V12 evo2 combo with a 320 treadwear rating. Over the next 18 months and 42,500 miles, I put these tires through the ringer as they took on daily driving duties in every condition imaginable: 100+ degree summers, torrential downpours, 10 degree winters, snow-covered side roads, spirited driving through mountain twisties, and multiple 400+ HP/TQ pulls on dry pavement. Usually when tires last this long, they don’t do much for performance, but Hankook was able to find a very nice happy medium with these. Maybe it’s a testament to my suspension, wheel/tire setup, alignment, and driving style, but the wear pattern on the front and rears were pretty even across the board. The fronts probably had 10,000 miles left of life in them.
My only complaint would be when running lower pressures, these did seem to flatspot when left sitting for a few days that would take a few minutes of driving to clear up. Near the end of the life of the tires, the old TPMS also began to show up as inactive from time to time and the impending warning code was driving me crazy. When it came time to start searching for replacements, and new TPMS sensors, I was very tempted to just repurchase another set of the V12 evo2s, but another tire claiming an even better 340 treadwear rating and garnering a lot of praise online ultimately won me over: the Firestone Firehawk Indy 500s. I ordered the same 235/365 sizes as before, and as they always do, Tire Rack had them in my possession within a few days. Luckily I was able to stretch the life of my previous Hankooks out until this single turbo teardown, so I can have the old tires taken off and the new ones mounted/balanced in the meantime. I also prefer to take off the wheels myself, and mount them back to the vehicle myself once the new rubber is installed. The more I can reduce the amount of times someone other than me wrenches on my car, the better, especially with stuff I don’t want terribly over-torqued or scratched up. I can’t wait to stop staring at these and actually get them mounted up.
Since I knew I was going to be installing the massive Phoenix Race FMIC that requires a lot of cutting of the plastic front shroud, off came the front bumper. Now I had a full view of the existing 7” VRSF FMIC I’d been running for the past year or so.
Out came all the lower splash guards, plastic intake ducting out, and radiator fan so I could gain access to the t-bolt clamps on the FMIC.
After loosening the t-bolt clamps and removing the two aluminum screws holding the FMIC in place, it dropped out easily. Now I was ready to start unbolting some of the components in the engine bay to gain full access to the intake valves as a walnut blast was the first order of business.
The Mishimoto OCC hooked up to the RB external PCV in order to remove the front inlet, charge pipe and air filters.
Strut bars, BMS OCC, throttle body and all associated intake piping removed.
Vacuum canisters gone, front MMP inlet out.
