Fuel starvation and some strategies on how to prevent it

Fuel starvation is probably one of our biggest enemies. With a simple fuel pump upgrade, running beneath 1/2 of a tank, making over 350whp with no other resources, it’s a near guarantee to happen, at least briefly.

When air is picked up, while the injection time is met, the fuel just isn’t in the line, available to be injected, so the injector injects whatever is in the line. If there are bubbles, it usually wont be pure air, if it doesn’t misfire altogether, it’s enough to yield a combustion, just typically a much leaner one than intended.

Depending on the scale and frequency of these air-ingestion events and other factors, this can lead to nasty detonation events and parts failures.

So what can we do!? Obviously, a surge tank. Surge tanks are made to solve this. A surge tank is a second, smaller tank that keeps the pump fully submerged, even if fuel level is modest and even if the primary intank pump picks up some air. As long as the surge tank is mostly full, it drastically reduces the chances of sending air to the rail. But there are options before getting this far in also.

For the e46, BMW made a special solution for the M3 that drops into all nonMs.

e46 M3 fuel baffle

pn 16112229656

This will certainly help a bit. It holds return fuel more directly over the pickup.

Then there’s a hydramat. The hydramat is a special sock. It somehow will give fuel preference over air- though honestly I have no clue how it does that. Most importantly is that it does. So if it’s in contact with a relatively small amount of fuel, it can do a very good job of not pulling up air. We carry these for traditional mounting for a e36/e46 fuel pump hanger.

None of these solutions preclude each other. Throwing the kitchen sink at it is a solution. At every step, if air can be prevented from entering the fuel lines, it’s always a win. So even with a surge tank, a hydramat and M3 baffle still help.

Pressure testing makes everyone happier

pressure tester cap

Updated: Nov 22, 2021

This might be on the level of psychological advice: get a pressure testing setup.

It’s very hard to catch some leaks without testing. Nearly impossible sometimes.

But a thorough pressure test solves this.

Sometimes a rail isn’t holding the injectors square enough to the manifold (refer to my other blog entry on fuel rail options if you run into this), sometimes there’s a hairline split in a coupling or a pipe or the manifold or the maf. This stuff happens. Sometimes it happens with brand new parts. It’s not your fault. Hopefully you have a nice warranty.

With enough leaks, the logs will never look great. The log will be worse with worse leaks. And small leaks may even sneak by unnoticed.

A finished tune incorporating a leak into the tune will only degrade with repair.

Pressure testing can be accomplished in many ways. My go-to option is silicone intakes’s schrader valve capping system.

compression testing cap with schrader valve

compression testing cap with schrader valve

Cap everything. Cap your exhaust. Cap your wastegate (if you have one). Cap breather lines.

Cap everything there is to be capped.

The next hurdle is pressurized air. A traditional air compressor is best. Any size will do. Remember to turn it off so it doesn’t fire up while you’re trying to listen for leaks. You can make do with tire inflators and tires, but it’s rough.

While all leaks have varying levels of problems they present, the most important area for tuning is between the maf and the intake valves. Exhaust and premaf intake leaks can create problems too and this tool and exercise should be used to maintain a leak-free system.

The only people that have no leaks are those that test.

Flashing a ms4x tune

BRT flasher

So you have your OBD2 interface cable, and a flasher.

What now!?

-The first step is to install the flasher and the cable’s drivers.

-Let’s test it. If you open the flasher with nothing connected to your computer, you’ll notice the red letters in the bottom left “looking for cable”. If you plug in the cable and wait several seconds and that message changes to “cable connected”, we’re in good shape. If it does not, please refer to the bottom of the page for troubleshooting.

This image has an empty alt attribute; its file name is file.jpg

-Plug the obd2 cable into your car and put the key in second position.

-Hit “Identify”. This should display the model and vin of your dme. Perform a full read by hitting the “Read Full”. Let the flasher name the file.

-Send us this file and await your file should be ready overnight. Or within a few mins at a given time if scheduled.

-To write the new full file (256k, 512k), go to the “write” tab, select “Write Full” and select the file we sent you. And wait a few minutes.

-To write a partial (24k, 32k or 64k), select “write tune”.

-After flashing

Go to the “Clear” tab and hit the “Clear DTCs” button to clear codes and “All Adapts” to reset all adaptions after each flash.

-key drill

-Stay away from the gas pedal for all of this.

-After the flash and adaptions are reset, turn the car off for ten seconds,

-turn the car to second position.

You should then hear a click from the intake manifold, this is your throttle body cycling and establishing learned values, it’s a good confirmation of healthy function.

-After you hear the click, wait another 5 seconds.

-turn the car off and wait a few seconds

Then crank


-When connecting a cable to windows, it should alert that the device needs drivers. This alert can be useful: when it asks for a driver location, bring it to the drivers folder in the flasher folder.

This can also be done manually by finding the cable in the device manager. Plugging it in and unplugging it should make it clear which device it is.

-If the cable isn’t being recognized by the computer, the problem is likely to be in either the cable or the usb port of the computer.


innovate wideband

Updated: Jan 11

AEM or Innovate!?

It’s one of the oldest questions we get asked.

We think the SCG1 is probably the best deal on the market for a boost gauge/boost controller and wideband solution. It’s better that it’s all together. The failsafe is really cool.

But maybe you have a super sweet boost controller and you don’t want something like the SCG1 for boost control? the PSB-1 offers the same failsafes, no boost control.



  • Does not need a fresh air calibration
  • cheap
  • relatively reliable
  • much more flexible wiring


  • requires serial connector
  • sometimes die over nothing


This image has an empty alt attribute; its file name is 5404dc_44778ed8eb5d4a16b934b08e2ef606dc~mv2.webp


  • can be a scg1 and have failsafes, be one gauge with other stuff
  • fresh air calibration should make it more accurate
  • also cheap
  • the nicest wiring, albeit it stiff and sometimes hard to reasonably tuck
  • comes with serial port


  • sometimes die over nothing
  • need calibration every so often
This image has an empty alt attribute; its file name is 5404dc_2757eb2ff48c4f329a145b01d3761ce7~mv2.webp

Given the similar life expectancy, I have a hard time coming up with a solid suggestion of one or the other. We’ve used them both with great success. And we’ve had disappointing failures with both brands. Though some clients and some cars have no issues with either wideband for many thousands of miles. Pick what fits your budget. We would probably choose the SCG-1 for a lot of situations. But the AEM is also very practical, accurate and easy to use. What about all the others? Ok, so there are countless makers of widebands. All of our personal projects and the vast majority of our experiences and customers have been with one of the above products. But all we really need for our process is a serial line out. APSX d1 and d2, Ecotrons “Accurate lambda meter”, 14Point7 NAW_7s (model out of production? maybe others?), MFR stealth gauge, Phidget interfacekit, PLX SM-AFR, Tech Edge, some TXS stuff, and zeitronix zt-2 are all technically supported by romraider. Some require costly cables or sometimes another module to get the simple serial signal out, but these all have some avenue to function that was, at least once, in production.


Vent gauge pod mounts are very popular right now. Not unlike the rest of the instrument cluster, one must be able to safely see some things while driving hard to make the most of the car and to monitor it reasonably. To shift right at redline, you have to see the tach. During tuning, monitoring the wideband is extremely important, so choosing a place where it can be read during driving, without having to look away from the asphalt ahead, is key. To note, no one with a vent-mounted wideband has ever recounted their logged mixtures with any accuracy, please find a better solution. ATI gauge pods. Rally road gauge pods. Cheap $10 amazon gauge pods that go on the dash. Please think about safety with this portion of the build. Obsession with cleanliness is the enemy of success here.

M5x Oil Pump Nut solutions

failed oil pump sprocket

The Achilles heel of the m5x is its oil pump nut. It’s somewhat common that any m5x engine when driven on track or beat mercilessly on the street will likely run into this issue. To be very blunt, this issue being that oil pump nut backing off or shaft failure.

There’s a handful of solutions to dealing with this.

  • wire tie
  • welding
  • tensioners
  • using new parts
  • shaft upgrades
  • wire tied pump

parkin pump and audi tensioner

It’s not uncommon to see a combination of these to more seriously combat failure.

Welding to the shaft or even adding too much heat too close to the shaft can end in failure. But done correctly, it’s a very effective solution.

This image has an empty alt attribute; its file name is failedsprocket.jpeg

Wire has been linked with some failures, but for the most part, people who use it report back success. Wire tie technique is a factor.

With a tightened stock nut, there’s often a bit of play, does that play help prevent the shaft from failure if the chain jumps? We don’t know. Do tensioners that retract actually help? They’re often used in tandem with other solutions, so it’s hard to say under which conditions it helps and under which it doesn’t. It doesn’t hurt.

GSR originally developed the 4 bolt pump solution and is still the most widely regarded m52tu/m54 solution. The Parkin solution is very similar, but uses less hardware and has seen failure. If the watermark left anything to the imagination, it can be found at bimmerworld.

Achilles and VAC offer a single bolt shaft upgrade that is objectively decent, but probably the most work for the end user to instal, requiring pressing the impeller onto the shaft. Achilles has added wire tie to their solution. When I experimented with the VAC solution a decade ago, they recommended loctite to go with this reverse-thread solution.

As these parts have become up to thirty years old, at time of writing, chains are prone to stretch and pretty much all the hardware that comes in contact is prone to wear. During a deeper rebuild, where the timing cover comes off, it makes sense to replace the chains, the crank hub, tensioners and guides. This effectively prevents a lot of issues regarding pump drive failure.

It’s important to remember that these pumps are not all directly interchangeable. Single vanos pumps use a smaller pulley and a different oil outlet hole location on the block than double vanos nonm pumps.

s54 pumps have been retrofitted to work in both setups, though they are more directly interchangeable with with single vanos pumps. Single vanos pumps are usually the s54 choice when going to a sump setup away from stock.

RomRaider logger setup for MS4X


So you’ve dowloaded RomRaider. Here’s what you need to do next:

Start by removing all versions of Java (this uninstaller might do it all) and perform a restart. Then install only the x86 (32 bit) version.

Oracle Java Downloads Page

After a restart and installation of romraider, hopefully romraider is running.

  1. Open up RR logger
  2. Go to the Settings menu at the top
  3. Logger definition location…
  4. Select the logger definition .xml file you received
  5. Then open up the Settings menu again
  6. Select logging protocol options
  7. Select DS2 K-Line
  8. Connect the cable to your car and laptop
  9. You should now have a list of dme-specific parameters that you can select
  10. Select parameters and save those selections as a Profile for future use

List of items to log for turbo tuning (except accelerator position on ms41 (please select these in this order):

  • coolant temp
  • accelerator position
  • engine speed
  • ignition angle
  • engine load
  • injection time
  • lambda integrator bank 1
  • TPS
  • knock sensor volts bank 1
  • knock sensor volts bank 2
  • oil temp
  • iat
  • wideband

Our bottom mount kit for e46

be racing tuning turbo kit

Recently we built a turbo kit for a zhp e46, the primary spec was to keep AC.

Some secondary goals were to improve on common issues in kit design, utilizing this manifold or others that are similar:

  • no charge pipe under the subframe
  • no charge pipe tucked under the exhaust manifold
  • 3″ turbo inlet pipe
  • functional gravity drain

I think these were reasonable goals, though neither of us had built a SPA-based kit before, we’ve been able to achieve these things or have seen them accomplished on the eurosport, aa, and some tubular manifolds. Every bend causes pumping losses and we did our best to reduce the number and severity of the bends necessary to complete the above goals.

Haven’t finished tuning it as the stock clutch predictably let go. Will update this post with better picture as we gather them.

If seriously interested, please send us an email regarding this kit.


TiAL gate

There’s a lot to think about with wastegates. Here’s a collection of some observations and thoughts about available options.

Size: so these things come in a lot of different sizes. Typically, the smaller the gate, the faster it is to react and the easier it is to control boost. A lot of setups can get away with a 38mm wastegate. The setups that run very large turbos without a lot of boost need more gate. Manifolds with more questionable gate routing also typically need more gate (sometimes in number of gates) to achieve boost targets.

Turbosmart gate
Turbosmart gate
precision gate
Precision gate

Mounting, 2-bolt, v-band, 3-bolt or 4 bolt. Why are there so many variants!? I don’t know. I think some of these (3 and 4 bolt) are legacy and JDM manufacturers love making that stuff. 2 bolt and v-band make up the bulk of what people use in the real world. Some v-bands are low-quality and have various issues. If using bolts, use nice hardware with copper lock nuts, otherwise this is likely to rattle out.

So knockoff wastegates are very cheap. Nice ones aren’t. The knock off TiAL and Turbosmart mostly function effectively, but they aren’t perfect.

Cheap gates typically have the issue of all their hardware rattling out. The fast moving stuff does fall all the way out, but all of it seems to loosen up. Rebuilding the whole thing with red loctite is a functional option. Buying a product that isn’t the outcome of some blatant copyright infringement also works.

TiAL, Turbosmart and Precision wastegates don’t rattle apart. These are some of the biggest players in the game. Precision’s entry is a bit of a late entrant. But it works, doesn’t rattle apart. I’m sure there are some other good wastegates that hold together without loctite, but don’t expect them to be cheap.

TiAL aircooled gate
TiAL aircooled gate
Turbosmart electronic gates
Turbosmart electronic gates

There are some exciting gates on the market too, Turbosmart and TiAL have some uniqe gates compared to the tradition of the form factor seen in the three gates above. The TiAL aircooled gate is awesome. But it’s substantially taller than a their standard 38mm vband gate. Keep in mind fitment constraints if considering something like this.

The Turbosmart electronic gates are also very exciting. Keep in mind these need a controller capable of dealing with them.

Gates that skip full mention bc there’s something wrong with them in price: HKS, Greddy. Turbonetics gate is a rebranded Precision. Synapse uses an alternative to a traditional diaphragm and there are mixed results with boost control outcomes.

boost-connect fittings
Synapse Boost-Connect high-temp kit

Just as important as the wastegate are the lines attached to it. Wastegate line failures typically lead to overboosting, sometimes by massive figures, and all the failures that can come from that. Aside from just keeping your wastegate lines away from heat, one very effective strategy is to use the air-brake based pushlock system that Synapse appropriates for their ‘Boost-Connect’ product line. They have an entire section dedicated to heat-capable products which are perfect for using for boost control.

Turbo M5x: Top or bottom mount?

PPF bottom mount

A brief conversation about the available options

Mid-mount is dead, RIP midmount. A handful of fabricators used to create this wonderful configuration. It was typically difficult to install, but once installed it provided a number of benefits:

midmount turbo manifold
midmount turbo manifold

easy to drain, easy downpipe, and most of the other typical bottom-mount benefits (temp, weight, invisibility, ac, etc) without any of the top-mount problems. It’s really a very high-mounted bottom-mount. One catch is that they sometimes required totally custom motor mounts.

On to stuff that’s still in production: Top mounts and bottom mounts.

The two most common top mount designs are the cheapest ones: The CX and the RSI and its twin, the knockoff RSI. Other options include PPF, k64, mint, doc race, ftwl, Cory Misko, vi engineering, Kangaroos team and certainly some others that were either forgotten or unknown. These are mostly stainless cast elbow construction- which is the handmade standard for high performance turbo manifolds. The PPF is unfortunately really limited to those with access to a diesel 20′ transmission. They make a lovely set of parts to go with that conversion. The Kangaroos team manifold is the first cast iron top mount for this platform.

RSI knock-off
RSI knock-off

Top mount pros:

  • looks cool
  • drains oil like a champ
  • can typically run any turbo the manifold can support

Top mount cons:

  • cooks valve cover gaskets
  • cooks hood paint
  • complicated downpipe
  • complicated/impossible filter
  • unpleasant heat locus

Bottom mounts are very much worth considering. They allow for AC without struggle. Center of weight of the kit is much lower and further back. It concentrates heat more or less where the cats are factory-mounted (a spot compliant with a lot of heat), not where the valve cover or hood are. Bottom mounts typically can’t house much more than an H-cover (4″/3″) and that’s not all manifolds. But that’s already pretty huge.

Bottom mount pros:

  • Keeps the heat low and back like a stock exhaust system
  • nearly invisible
  • good weight distribution

Bottom mount cons:

  • aftermarket or custom motor mount arm necessary
  • invisible
Chinese cast bottom-mount
Chinese cast bottom-mount
steedspeed m5x manifold
steedspeed m5x manifold

SPA makes the most beloved current production cast manifold for the m5x. The AA has been out of production for a while but is still available second-hand. The Steedspeed from CES is cast-like. It’s also a great deal. PPF also makes beautiful tubular bottom mounts that fit our factory 30′ slant. The cheap chinese ebay cast bottom mount has had a lot of reported issues from warping to manufacturing issues that prevent easy installation. The cheap ebay tubular bottom-mount doesn’t deserve this many lette…

Let your budget and tastes guide you.


Thoughts on turbo sizing for a BMW inline 6

e46 nonM turbo kit

So what’s the right size turbo? What turbo should I get for my m5x?

This is such an open-ended question. It depends on so much.

cx turbo
Chinese 3582

Racing’s e36/e46 gt3582 .63 ar t3 turbo. If given a displacement range of 2.0-3.2L, they did a great job. Honestly, not sure what it does on a 2.0 or 2.2L m5x, but it’s not wildly laggy on b25 variants, and spools almost too quickly on an s52.

Let’s start with CX Racing’s e36/e46 gt3582 .63 ar t3 turbo. If given a displacement range of 2.0-3.2L, they did a great job. Honestly, not sure what it does on a 2.0 or 2.2L m5x, but it’s not wildly laggy on b25 variants, and spools almost too quickly on an s52.

That’s a tight turbine housing on that gt35, it’s great for fast spool, not going to make as much top end as some other options, but will spool faster.

Everything with turbo sizing is a line with two ends. Most options offering more power will induce later spool. If the gt35 from cx is too laggy for someone’s taste for a

Chinese 6662

Everything with turbo sizing is a line with two ends. Most options offering more power will induce later spool. If the gt35 from cx is too laggy for someone’s taste for a given setup, going from that 61mm turbo to something like a gt3076 (57mm turbo), given the same turbine will spool significantly earlier. But if seeking more top end, a larger spec like a gt3586 (67mm) or gt4088 (71mm) will induce later spool points, but will make more top end and induce less upper rpm torque loss.

Some companies offer stainless turbine housings, these are a great option for top mount setups. Cast iron housings rust. Relying on a turbo blanket for dressup is a poor plan (don’t look at our home page, it’s aesthetic). The turbo blanket will hold a lot of the heat of the turbine housing in a much larger package.

Arashi 3584 w stainless housing

Conclusion: Turbo sizing is deeply dependent on personal preferences, goals and evolving tastes. Don’t focus too much with getting it right the first time. Chinese turbos typically make similar power and spool just like their authentic cousins. They are a great way of figuring out what you want without having to spend much money.