BMW E30 Turbo Guide
Anyone that owns a BMW E30 knows that the factory M20B25 2.5L, M20B27 2.7L, and M42 4-cylinder engines leave a lot to be desired in the horsepower department. While the factory engine options are certainly unbearable to get a 2600 lb BMW E30 going under its own weight, you won’t be winning any stilt races.
That is where forced induction comes into play. Like many other BMWs from the 80s, 90s, and early 2000s, turbocharging is a go-to solution to get some increasingly ponies under the hood. Playing into that remoter are the unsurmountable engines offered in US-Spec E30s which can all withstand a pearly value increasingly horsepower than their factory output. A well-sorted BMW E30 turbo is capable of producing up to 300 horsepower without any serious internal upgrades or modifications.
In this guide, we'll imbricate the nuts of throwing together a well-constructed E30 turbo setup. Additionally, we'll recommend a couple of premade E30 turbo kits as well. While we do imbricate the main components required for an E30 turbo build, this guide is meant to serve as a rough starting point for your research.
E30 Turbo Engine Considerations
When it comes to E30 turbo builds, the engine in your respective model is the most important factor. While all of the engines offered in US-Spec BMW E30s are respectable in their own right, some E30 engines are largest than others to turbocharge. To alimony things a bit simpler, we’ll only be tent the primary three engines that came in US-Spec E30s including the BMW M20B25, BMW M20B27, and BMW M42 4-Cylinder. The M20B25 came in E30 325i and 325is models, the M20B27 came in E30 325e and 325es models, and the M42 came in E30 318i and 318is models. Early model E30 318is used the older M10B18 engine, but in this guide, we’ll be focused on late-model 318is.
Out of the three engines and models to segregate from, the M20B25-powered 325i/is and the M42-powered 318i/is are the weightier candidates for forced induction. While it is possible to turbocharge an M20B27, spare modifications and ramified engine management solutions are required.
M20B25
As we stated above, the BMW M20B25 is one of, if not the weightier E30 engines to turbocharge. As with many other BMW 6-cylinders, the M20 is extremely reliable, strong, and resilient as long as it is maintained and tuned properly. One of the reasons that the M20B25 is such a good candidate for forced induction is its relatively low pinch ratio. The BMW M20B25’s 9.7:1 pinch ratio is notably lower than both the M20B27 - with a CR of 10.3:1 - and M42 - with a CR of 10.0:1. This is good for forced induction, as there is less strain put on the internal components of the engine with a lower ratio.
It is often said that the M20 marrow end can withstand power figures tropical to the 400 horsepower mark with stock internals. Obviously, the viability of reliably running a 400-horsepower M20B25 for an extended period of time ultimately boils lanugo to the engine’s condition and the quality of your tune.
M20B27
Despite stuff flipside engine in the M20 6-cylinder family, the M20B27 engine is not a good option to turbocharge out of the gate. There are a few reasons for this. Ultimately, the M20B27 was built as an economy-focused engine designed for improved gas mileage over performance. As a result, many of the internal components aren’t as optimized as the M20B25. The M20B27 features a restrictive “200” cylinder throne with smaller ports, a tamer camshaft, and softer valve springs. As a result, the M20B27 can only rev to 4,500 RPM, which is the main limiting factor for turbocharging a B27. With such a low redline, uplift can’t be built fast unbearable for it to be worth it in the long run.
With that stuff said, there is a worldwide and relatively simple remedy to this issue. Since the M20B27 cylinder throne is the main limitation, some enthusiasts swap heads with an M20B25. The marrow end of both engines is nearly identical, making a throne swap easy and effective. An “885” cylinder throne swap onto an M20B27 will increase ostracism to 2.8L while raising the redline and decreasing the pinch ratio dramatically. Some E30 enthusiasts say that this setup is unquestionably the most platonic engine wattle for a turbo E30.
In 1987, M20B27 engines came from the factory with an upgraded Motronic 1.3 fuel injection system and an 885-cylinder throne from the M20B25. These rare engines, often tabbed “Super-ETA” engines, are very well equipped for forced induction, as BMW did all of the nonflexible work at the factory.
BMW M42 4-Cylinder
As the only 4-cylinder on this list, the BMW M42 engine stands out for a few reasons. The main reason is that the M42 is unquestionably a fantastic candidate for boost. It is moreover the lightest engine offered in late-model US-Spec E30s, making it a good option for those looking to maximize weight savings for a track environment. Additionally, the M42 comes from the factory with a forged crankshaft and rods, making it uncommonly strong.
One of the M42’s main drawbacks from a turbo perspective is its upper pinch ratio. With a 10.0:1 pinch ratio, the M42 is pushing the limits of what is often deemed unscratched for forced induction. As a result, many E30 318i owners opt to run low-compression pistons or a low-compression throne gasket. The ultimate goal should be to have 8.6:1 or lower pinch which will make uplift much safer and increasingly reliable. Other E30 turbo owners moreover well-wisher for the use of E85 on turbo M42 builds, as it limits the risk of detonation.
How Much Power Can A Turbo E30 Handle?
Ultimately, the value of power that a turbo E30 can handle boils lanugo to the engine that you chose for your build, the value of supporting modifications washed-up to the E30, and the tune. If we are talking well-nigh stock turbo E30 performance, peak horsepower figures between M20-powered models and M42 E30s are remarkably similar. Both the M20 and M42 engines are extremely capable and strong out of the gate.
It is often said that the M20B25 can hold virtually 400 horsepower surpassing any internal upgrades are needed. Since the M20B27 shares the same marrow end as the B25, its limit is the same. With that stuff said, you won’t be worldly-wise to make that value of power from an M20B27 unless you swap on an “885” cylinder head.
Like the M20, the 4-cylinder BMW M42 is moreover an extremely strong engine from the factory. Due to the fact that the M42 has a forged crankshaft and forged rods, it can withstand a pearly value of abuse. Most turbo E30 enthusiasts requirement that the upper limits of the M42 are similar to the limits of a factory M20, somewhere virtually the 400 horsepower mark.
Obviously, these horsepower figures are only reachable and sustainable with a quality tune and other supporting modifications. We’ll imbricate that in increasingly detail in the sections to come.
E30 Turbo Parts and Components
There are substantially two routes when it comes to turbocharging an E30; you can either purchase a premade kit or collect all of the necessary components individually. While there isn’t a right or wrong wordplay in terms of how you go well-nigh it, piecing together your own kit will requite you increasingly flexibility in terms of the parts that you use which can ultimately result in largest quality. While there are some decent E30 turbo kits out there, you’ll unchangingly have increasingly tenancy and say in how your build turns out with a custom build.
In the pursuit sections, we’ll outline the majority of major components that you’ll need to piece together your own E30 turbo kit. While we’ll hit on the big items that you’ll need, it is possible that you’ll need spare components not listed here. This is meant as a good starting checklist for a 300-horsepower turbo E30 build.
Turbo E30 Engine Management / Wideband O2 Sensor
One of the most crucial components for any turbo build, including a turbo E30 build, is engine management. Luckily, there are a ton of standalone options out there as far as E30 engine management is concerned. Undoubtedly the most popular E30 turbo engine management system is the MegaSquirt PNP engine management system which not only comes with everything that you need to properly tune your turbo E30, but it is moreover the EMS with the most support on E30 turbo forums. The MegaSquirt can be installed in virtually an hour and replaces the factory DME entirely.
The E30 MegaSquirt is designed specifically for turbo applications, with features such as 12x12 Air fuel ratio target tables for use with a wideband O2 sensor, 4-bar MAP sensor, overboost protection, and a sealed loop uplift controller all ready to go right out of the box.
In order to tune your turbo E30 properly, you’ll moreover need a wideband O2 sensor to not only measure and tune air/fuel ratios, but moreover to trammels for potential issues once a tune is installed. AEM sells a wideband for the E30 which is very popular in the E30 polity and reads air/fuel mixtures with utmost accuracy.
BMW E30 Turbo Manifold and Exhaust
There’s quite a bit of hardware to alimony track of when it comes to a BMW E30 turbo build. One of the most important parts of the unshortened E30 turbo system is the E30 turbo manifold and frazzle components that follow. The E30 turbo manifold is one of the most crucial components of the unshortened build, as it can determine important characteristics well-nigh how your turbo will spool and react.
E30 turbo manifolds come in many variegated shapes and sizes, from aftermarket log manifolds to tubular turbo manifolds with varying runner lengths. Ultimately, you’ll need to consider your E30’s engine, the value of space in your engine bay, and the size of turbo that you intend on using. This CXRacing 304 stainless steel E30 turbo manifold is a solid option for those looking to use a T3/T4 turbo for their E30 turbo build.
In wing to the E30 turbo manifold, you’ll moreover need a quality downpipe and custom frazzle to manipulate of frazzle gas effectively. You’ll have to find an E30 turbo downpipe that works with the E30 turbo manifold of your choice. If there isn’t a premade downpipe option that works with your turbo manifold, you’ll have to order a custom downpipe. The same can be said for the rest of your turbo E30’s frazzle system. Most people end up fabricating an frazzle for their turbo E30, as turbo setups can vary significantly from one person to another. While the fewer restrictions the better, you’ll need to weld in a catalytic converter if you are planning to pass emissions in your turbo BMW E30.
E30 External Wastegate and Blow-Off Valve
Regulating pressure within your E30’s turbo system is one of the most crucial aspects of a build in regard to reliability. With too much pressure within the system, you can do serious forfeiture to your turbo and engine. To manage uplift pressure, you’ll need a couple of devices.
The first of which is an external E30 wastegate. The purpose of an E30 wastegate is to regulate the frazzle gasses that spritz through the turbocharger. This ensures that the turbocharger doesn’t produce a detrimental value of boost. E30 wastegates are set to a specific spring rate which limits uplift to that amount. 8 PSI wastegates are worldwide with E30 turbo builds, meaning that without the presence of a uplift controller, the turbo will have a maximum output of 8 PSI.
You’ll moreover need an E30 turbo blow-off valve to regulate the pressure on either side of the throttle body. If you let off the throttle under boost, a rush of compressed air travels through the turbo system and is immediately stopped at the sealed throttle plate. At that point, the pressurized air has nowhere to go besides when to where it came from. The air is forced when into the turbo, which then interferes with the compressor wheel. This is tabbed ‘compressor surge’ and can forfeiture your turbo’s wheel shaft and bearings. Ultimately, if compressor surge is severe and frequent, it can skiver turbo response and overall drivability.
Both an external E30 wastegate and a blow-off valve are essential in towers a reliable turbo E30.
E30 Electronic Uplift Controller & Uplift Gauge
Building off of the components that we have once discussed, an electronic uplift controller and uplift gauge are hair-trigger if you intend on producing increasingly uplift than your wastegate allows. If you segregate to use a MegaSquirt engine management system, it is possible to modify it to be used as a uplift controller. While a wastegate is limited to the uplift pressure required to unshut the wastegate spring, an E30 uplift controller allows spare pressure to trundling through the turbo. That allows you to set uplift pressure to whatever you choose.
To monitor that the correct value of uplift is stuff output by the turbo, you’ll need an E30 uplift gauge. While it is a simple analog dial, a uplift gauge is essential if you are planning on running increasingly uplift than what your wastegate is set for. If you aren’t monitoring your E30’s boost, it could be producing a rabble-rousing value of uplift without you knowing.
E30 Intercooler and Piping
A quality intercooler is one of the most important parts of any turbo build. Without a proper intercooler, you’ll be leaving power, longevity, and reliability on the table. Turbochargers inherently produce a ton of heat. An FMIC's job is to tomfool the air without it leaves the turbocharger surpassing it enters the combustion chamber. Ultimately, heat is the enemy of an efficient engine. Heat reduces combustibility or power, but moreover decreases engine longevity and reliability as upper temperatures over sustained periods of time can warp internals.
A proper E30 intercooler can come in many shapes and sizes. While most turbo E30 builds tend to be very custom, E30 intercoolers are a pretty universal part regardless of your turbo application. Some companies, like CXRacing sell E30 intercooler kits that come with intercooler piping and the intercooler itself. If your E30 turbo setup is in an unorthodox location, it is unlikely that pre-cut intercooler piping will meet your needs. In that case, you’ll have to cut your own piping.
E30 Fueling and Spark
Adding a turbo to your E30 requires some substantial fueling mods. This is due to the fact that the engine needs to recoup for the compressed air coming into the combustion chamber from the turbo. The two most important fueling modifications that you’ll need for your turbo E30 include an upgraded fuel pump, and upgraded injectors.
There’s a wide range of injectors that will work for a turbocharged E30, it truly just depends on your power goals. 450cc, or 42 lb, injectors are a worldwide nomination for turbo M20s. Injectors in the 450cc range will get you into the mid-300 horsepower range. You can moreover use 650cc injectors if you intend on doing increasingly power modifications in the future.
The other part of the fueling equation is the fuel pump. The E30 fuel pump is the lifeblood of the fuel system, as it supplies the injectors with fuel. For that reason, you don’t want to skimp on your fuel pump. The factory fuel pump is rated for virtually 250 horsepower surpassing it becomes a stickup in your turbo build. There are some very worldwide E30 fuel pump options that can sustain big power. One of the most popular options is the Walbro 255lph, which is good for virtually 500 horsepower at the crank.
Unless you are running a massive value of uplift (like 25-30PSI) chances are that you’ll be fine with Ngk BPR7ES spark plugs. If you are worried that those plugs might be too warm, you can unchangingly go a step colder which would moreover work just fine.
Other Turbo E30 Supporting Mods
Once you have your E30’s turbo setup compiled, assembled, and tuned, the nonflexible part is complete. However, there are still some other considerations that you’ll need to take into account. In the grand scheme of things, a summery turbo setup will add anywhere between 30-150 horsepower to a BMW E30. At this point, E30s are nearing 40 years old. The age of the car in wing to the fact that the E30 chassis was never designed for 300 horsepower ways that other aspects of your E30 will need to be refreshed and improved.
For one, standard E30 disc brakes aren’t equipped with unbearable stopping power for the wing of a turbo. While stock E30 calipers and rotors are unquestionably pretty capable, it is a good idea to purchase some performance E30 restriction pads and restriction fluid. Swapping brakes from an E36 M6 is flipside worldwide option for those looking for a bit increasingly braking performance.
We transiently mentioned other fueling mods, but they are an extremely important wing to an E30 turbo build if you are shooting for massive horsepower figures. Water/Methanol injection is crucial for over 500 horsepower builds as it protects versus detonation and keeps internal temperatures at a unscratched level. An E85 fuel tousle functions in a similar way and is a good pump gas volitional that will moreover yield a bit increasingly power.
Suspension is flipside important consideration, as factory E30 suspension is likely tired and worn out by now. Components like E30 tenancy arms, bushings, shocks/springs, and wittiness joints should all be checked and replaced.
BMW E30 Turbo Kits
If you don’t want to spend the time and money hunting virtually for all of the individual parts that make up a full E30 turbo setup, there are a few decent E30 turbo kits on the market. As the name suggests, E30 turbo kits come with all of the main components that you’ll need to get going with your E30 turbo setup. While the kits usually come nearly complete, some are missing important components, like an engine management system or intercooler, which you’ll still have to source yourself.
At the end of the day, you are unchangingly going to find higher quality parts and likely receive largest performance from an E30 turbo setup that you build yourself. Since kits are made to be a upkeep option, many of the components included, expressly the turbos themselves, aren’t the highest quality. Not everyone needs a big-dollar E30 turbo setup. If you fall into that camp, a BMW E30 turbo kit might be the option for you. Here are a couple of our suggestions for the weightier E30 turbo kits on the market currently.
1) Kamotors BMW E30 Turbo Kit
Price: $3,899.99
Power: 250-300 whp
Buy Here: 7speedshop.com
First up is the Kamotors turbo system for the BMW E30. This kit is the weightier option for those looking for a solidly built kit on a budget. Compared to many other turbo kits, the Kamotors kit comes with quality components like a stainless steel manifold and TRE PNP 60lb injectors. Despite its comparably low price, this is a very well-constructed and high-quality kit with tons of add-on options.
Included in the Kamotors kit is a no-name T3 8PSI internal wastegate turbocharger with a 2.5” V-band, oil feed and oil phlebotomize fittings and supply lines, a stainless steel manifold, tuition pipes, M20 clamps and couplers, 60lb injectors, IAT sensor, overdue the grille intercooler, and oil filter relocation kit. The kit can moreover be ordered with or without a standalone DME which changes the price by $900.
Ultimately, Kamotors has a very solid reputation in the BMW polity for their turbo kits and other related parts. This E30 turbo kit is rated for 300 horsepower and is a solid option for those looking for a sizable power gain. Of all of the components in the kit, the turbo might be the only piece that you’d want to replace. While no-name kit turbos might work well temporarily, you aren’t likely to get stellar reliability from one.
2) CXRacing BMW E30 Turbo Kit
Price: $2,624.56
Power: 300-500 whp
Buy Here: cxracing.com
Next on our list of E30 turbo kits is the CXRacing Catback BMW E30 turbo kit. While CXRacing is widely known for their upkeep products, there have been good reports well-nigh their turbo kits as well. The CXRacing E30 turbo kit is rated for 300-500 horsepower but that icon is seriously inflated if you are hoping for any kind of reliability. A power goal of virtually 250-300 horsepower is far increasingly achievable. The CXRacing kit was recently revised to full-length a largest E30 turbo manifold diamond with equal-length runners.
Included in the CXRacing kit is everything that you need to get going from a hardware perspective including a manifold downpipe kit, T4 GT35 turbocharger, 44mm 8PSI wastegate, air filter, oil filter sandwich and oil line kit, intercooler, intercooler piping kit, wrack-up off valve, catback, and a set of Vband clamps. The inclusion of a catback frazzle is perhaps the most shocking item on that list. While it is likely a decent option, the low price of the kit makes the true quality of the frazzle somewhat suspicious.
As far as E30 turbo kits go, the CXRacing kit is well-nigh as unseemly as it gets. While price isn’t unchangingly an indicator of how well a kit will perform, it must be said that the CX kit isn’t the king of the hill as far as turbo builds go. It seems that user reports are somewhat varied as well, with some owners saying that their kit failed without a month and others saying that their kit has served them well for years. Ultimately, it boils lanugo to your own individual build and the value of performance that you push out of it.
