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ryan_george 08-06-2009 06:26 PM

My E30 M20 turbo writeup (lots of pics)
This project has been in the back of mind for a few years now, and at the end of last summer I pulled the trigger and started to collect all the necessary bits and pieces to build a solid E30 M20B25 turbo. With so much documentation and experience out there it wasn’t that difficult to figure out what I wanted and how to get it. I want this write-up to be an overview of the whole project, and I’ll describe what I think are important points. If there are any questions, just ask! This is my first attempt at a turbo, so there were definitely some good learning experiences here for me.

The victim for this undertaking is an ’86 325, with an existing M20B25 swap and CatCam 283 (which was installed a few years ago).

The goals of this project are:
- ~300+ whp
- ~1 bar boost
- Driveable through town
- Easily serviceable
- Reliable (?)
- Less than $3000 (total)

This car is a secondary vehicle, so I was able to pull it off the road and have it in a non-running state for as long as necessary.

Let’s start off with an overview of the components:
- Holset HX35w turbo
- Megasquirt 2 + extra
- 42lb Lucas injectors
- Homebuilt turbo manifold adapter
- Homebuilt full 3” mandrel-bent exhaust
- 25x12x3” Ebay intercooler + plumbing (2.5”)
- Tial 38mm wastegate
- Single Magnaflow muffler
- Dual Bosch diverter valves
- ARP head studs, stock cylinder head gasket
- Homebuilt MBC

The poor, unsuspecting bronzit:

Since a major factor with this project is cost, the obvious answer for engine management is a Megasquirt ECU. I decided to go with the MSII with the extra code to have the “best-of-the-worst” hardware/software to work with. They are pretty straight-forward to assemble and use. Patience is important to reduce the amount of debugging you’ll need to go through in the likely event that problems arise.

Starting with the assembly of the MS:

Assembled MS with auxiliary Glen’s Garage pwm/ignition board

Modifications to the stock wiring harness:

The injectors are 42lb/hr, made by Lucas/Delphi. They are a standard size, so they fit into the stock manifold and fuel rail, with the same connectors.
42lb Lucas/Delphi injectors:

The ARP studs were another easy choice, being the most widely used and reasonably priced. The head gasket was replaced not too long ago, so I trusted it and didn’t want to go through the additional hassle of pulling the head to install the studs. I’ve heard of several people using the stock gasket without issues, so this was what I decided to go with. I loosened off all the stock bolts gradually and evenly, and then pulled them one by one and replaced them with the studs, then followed the torque spec for installation.
ARP studs:

Installed without removing the head and using the stock gasket:

Beginning of the turbo manifold adapter. I bought an extra set of stock manifolds so I could use two of the same (seemed to be easier plumbing). The material is SCH40 mild steel (heavy as hell). I made all of the flanges myself to help minimize costs. The manifold only required a total of 4 bends and some straight section. It’s a fully divided manifold to mate up to the T3 flange I made.


Preliminary mock-up of manifold:

Seems to be a pretty straight shot:

ryan_george 08-06-2009 06:26 PM

Positioning in the engine bay:

Fully welded:

With turbo:

It’s close!

Run-of-the-mill Tial 38mm wastegate:

Muffler (single 3” in/out):

Some of the exhaust piping. 3” mandrel-bent, and it’s galvanized (for corrosion protection). It’s easy to weld, but you just need to be careful of the galvanized coating (inhaling the fumes can make you really sick).

Down-pipe fabrication. A 6” long flexpipe is used to isolate the exhaust from the turbo+manifold:

In the engine bay:

ryan_george 08-06-2009 06:27 PM

Muffler mock-up:

Exhaust/muffler welding:

V-band flanges I made:

Consists of male/female halves to aid with centering and sealing:

Manifold modifications for wastegate plumbing:

Sketchy setup for facing a badly warped turbo flange (about 25 thou out of plane):

Pressure testing the manifold (up to 30psi). Aluminum plates with rubber gaskets to seal it off. Used a quick-disconnect air fitting to plumb into the shop’s air supply, and also mounted a pressure gauge to see if it leaks. Divided wastegate plumbing installed:

ryan_george 08-06-2009 06:27 PM

WG dump tube routing. Didn’t have any bent tube so I had to make my own “bends”:

Downpipe exit. Runs up right beside the CAB and is pretty tight to the body:

Rest of exhaust. It was tucked as close to the body as possible for ground clearance purposes. I used all of the stock mounting points for hanging it, and had it run down the centerline of the car to use the existing heat-shielding. Very simple and I’m very pleased with how it turned out.

ryan_george 08-06-2009 06:28 PM

Intercooler and plumbing (Ebay brand). Nicely packaged and it all seems to work:

Intercooler mock-up. I wanted to run the in/out tubes beneath the headlights to make plumbing as simple (and straight) as possible. The 2.5” tube is very tight between the frame and headlight buckets.

Had to notch some of the lower rad-support for clearance. None of the frame rails were modified. I also cut out a bit of the valence to increase airflow to the upper parts of the IC.

Intercooler and oil cooler mounted. I used a simple 3/4” square tube for support. The oil cooler is also mounted to tabs on this tube. The IC is supported at the bottom by small tabs welded to the chassis.

TPS and IAT. The TPS is the typical unit from the E36 and others. Part number: 13 63 1 726 591
The IAT is a standard GM unit, bought from DIYautotune. I wanted to mount the IAT as close as possible to the engine, without having to deal with welding into the charge piping. This was an obvious solution. Drill + tap (and also machined it down a bit):

ryan_george 08-06-2009 06:28 PM

Had to rework the TPS adapter afterwards due to interference with the manifold:

The intake plumbing was fairly straight forward, using a minimal amount of tubes/couplings.
Bought a big, honkin’ 3”-4” adapter for the compressor inlet. Used an existing 3” K&N intake I had lying around for the pre-turbo part of it. Also built a shield around the filter to prevent road debris, but still allow adequate airflow and drainage in the event that water starts pooling there.

Had to notch some of the headlight bucket for it to fit properly. I was able to run the 2.5” tube under the headlights, although it’s a bit tight. 3” would be very difficult.

Some welded tubes to make life a bit easier/cleaner. You can see one of the flanges welded on for the DV.

ryan_george 08-06-2009 06:29 PM

General shots of the intake system.

The oil system on this car was a bit of a hassle, but I was able to get through it all. I wanted to use the stock oil cooler housing (with thermostat) and not have to deal with relocating it (more plumbing, more mess, more chance for something to leak). I made an inline adapter that goes between the cooler housing and the oil filter. It has ports for the turbo oil feed and an oil pressure sender. I also tapped the housing bolt for an oil temperature sensor.

ryan_george 08-06-2009 06:29 PM

The unfortunate part about that piece is that the threads on both ends need to be different, which makes life a bit more complicated.
The oil cooler is B&M unit purchased through Summit. When installing the AN-to-NPT fittings onto the cooler you need to use LOTS of Teflon tape. I had to remove the fittings at one point, and the fittings galled the tapped holes in the cooler and stripped out most of the threads. It has been patched with JB weld and is still holding (thankfully).

For the turbo drain, I milled a flat section on the side of the oil pan and drilled through for a 90 degree bulkhead fitting. Nuts were used on both sides and good quality RTV used for sealing.

I also installed a new oil pump while the pan was off (and the old one was VERY rough).

For removing and installing the oil pan, I needed to lift the engine a bit for clearance issues. I don’t own an engine lift, so I built my own device for lifting the engine. It straddles the engine bay and sits on the frame rails. A large threaded rod with a fastener on one end is attached to the engine lift point at the front, and then it is lifted by turning the nut on the threaded rod. Worked pretty well, although it was still a bit of a pain putting everything back together under there…

ryan_george 08-06-2009 06:30 PM

The plumbing for the oil cooler and drain was fairly straight forward. Just connect the dots.

I bought some necessary gauges for monitoring the oil system and boost pressure. Oil pressure, oil temperature, and boost. All VDO Vision gauges. There’s also an additional wideband AFR gauge from Innovate. I cut a hole in the center console where the radio and OBC were located (shouldn’t be needing those anymore…), and replaced it with an aluminum sheet with holes for all the gauges.

A new MAP distribution block that will feed the ECU, FPR, WG, DVs, and boost gauge.

Taking hints from some high-end turbo engines, I wanted to build some bracing for the turbo to reduce the stress on the manifold. This is what I’m trying to copy:

ryan_george 08-06-2009 06:30 PM

Mine is bolted to the valve cover with 3 of the studs, and extends over the down pipe and bolts to the turbine outlet flange with 2 rod ends (of opposite thread) to create a turnbuckle system for tensioning.

The final touch on the exhaust system was having all of the manifold components and downpipe ceramic coated. For people in the GTA, my buddy gives good rates for ceramic and powder coating. Company name is Afterburner Performance Coatings. PM me for details….
Bling bling!

I built a simple heat shield for the turbine out of sheet aluminum. In an attempt to save what little paint I have left on the hood…

Everything all packed up in the front. Wish I had a bit more obvious airflow to the IC, but we’ll see how it works for now.

ryan_george 08-06-2009 06:31 PM


How to describe the car: This thing is nuts. (as many of you already experience daily). I’ve never been in something with this much ass-kicking torque before. It’s a new experience and I’m hooked…
The MS tuning is still a work in progress, but it’s coming along reasonably smoothly. The car can spin the wheels on a roll in 2nd, but unfortunately the clutch starts slipping in 3rd (duh….). I can reach full boost (1 bar) by 4500rpm. I’ve got a new Stage 4 clutch in the mail from South Bend and will update when that gets installed. Once my fueling is sorted out, I’ll spend a few hours on a dyno to get the ignition maps finalized (and get some whp numbers!).
Videos will also start showing up once this car is “legal” and insured.
There will also be some updates to this as new things progress (ie. Clutch, new differential, updated cooling system, brakes, etc….)

BMW BMXer 08-06-2009 08:40 PM

Holy shit dude.

Way to keep quiet then come out with the ****ing heat. Nice build.

Bullet Ride 08-06-2009 10:30 PM

Super clean build!
Did you end up staying under $3000?

Axxe 08-06-2009 10:38 PM

Nice build!

ryan_george 08-06-2009 11:21 PM

I didn't want to post an "in-progress" build thread, because sometimes progress was slow.... Figure I could get it all done in one shot.

I didn't make it under my $3000 budget. It was a lot closer to $4000, which isn't bad I suppose.

Insurance has just been sorted out, gotta get the car safetied on Monday, install the new clutch that's waiting for me, and then we're done! (for now...)

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