Naturally aspirated engine tuning

Naturally aspirated engine tuning is plain simple: (yet so ever challenging!)

A) Think your engine as an air pump

B) Air is always moving from higher pressure to lower

Thus, in order to increase the amount of air your naturally aspirated engine can transfer, you can:

1) Increase the size of an air pump (cc, cid)

2) Increase the effective speed of an air pump (rpm)

3) Optimize the gas flow for higher rpm band (Cylinder heads, valves, cams, headers etc.)

4) Increase the density of air (Cooler air temperature, reduce the pressure losses to minimum)

5) Optimize intake resonances (e.g. by shortening intake runner length, changing plenum size)

Like we learned in the other article, a naturally aspirated engine is as strong as its weakest link. There are no shortcuts.

Optimized air induction system with Ram-air effect on M6x engine. This effect can increase engine load (Mg/Stroke) up to 2,5%. In Addition, there can be up to 10% reduction in engine load (torque), if your engine is sucking hot air from engine compartment.

The Foundation of Naturally Aspirated engine: Displacement

Actually this applies for forced induction engines too. The very base foundation for HP/Torque capability is the engine displacement. Even in turbocharged applications, there is no replacement for displacement. More is better. Always.

RULE: In naturally aspirated engine, an engine displacement will give you torque characteristics for low to mid rpm range. The maximum torque you can achieve is approx. 120nm per litre on NA-engine.

Maximum torque per litre, naturally aspirated engines

80 nm/l: stock 2-valve NA-engines

100nm/l: Best 2-valve NA-engines

100-110 nm/l: Modern, stock 4-valve NA-engines

110-120 nm/l The best stock, and modified 4-valve NA-engines

The character of naturally aspirated engine: Cams

No matter how cool looking “Cool air intake system” your engine has – if you have not cammed your engine – anything else is just a waste of time.

“Why hotter cams 101”: If you seek for more power, you have to stretch the power band towards higher rpm range.

When you rev higher, the following will happen:

A) Less and less time your engine valves stays open (in milliseconds) in relation to rpm.

And;

B) Flowing gasses create more and more inertia, and fluid friction.

Take home points:

Problem A) can be tackled by assembling higher degree cams. This enable valves to stay open longer (in milliseconds) on higher rpm range.

Problem B) Increased overlap paired with good exhaust headers can take advantage of increased gas inertia. Exiting exhaust gasses in the header are creating both positive and negative pressure pulses, which can create low pressure areas, thus creating ‘scavenging effect’. OK, let’s explain this in the other words: While gasses are always looking for a route from higher pressure area to lower, during scavenging effect exhaust gasses have enough kinetic energy to keep moving forward – which in ideal situations – can create draft, thus creating ideal conditions for the exhaust valve to open. This is called scavenging effect. This effect can assist combustion chamber to empty burnt gasses more efficiently, while simultaneously sucking fresh air from induction system. This effect can improve your engine’s Volumetric Efficiency (VE), and produce more torque on upper rpm range.

Scavencing effect – also known as reverse or negative supercharging – is typically combined with inertial, or inertia supercharging, which in short can utilize A) kinetic energy of incoming air, and B) acoustic supercharging (rebouncing resonances ) in between a closing intake valve and intake manifold plenum.

NOTE TO SELF: The best efficiency I have personally reached is 113 nm per litre, measured on highly respectable hub dynanometer with DIN correction. On street, under optimal circumstances with +7 C outside temperature, the log data has shown engine loads that can be transferred as high as 119,4nm per litre. Please note this is NOT torque by DIN standard, only peak calculated torque from maximal engine load, hardly comparable with any other engines than my own.

RULE: In naturally aspirated engine, hotter cams will give you torque characteristics for high rpm range. Cams are the character of your engine. Period.

M6x engine with hollow billet cams. Good cams are prerequisite for producing 110 nm+ per litre engine.

Reducing pressure losses in the intake manifold

Higher intake manifold pressure than atmospheric pressure on naturally aspirated engine is rare sports. This phenomena has occurred to me only couple of times, although I have a lot of data at my disposal. MAP pressure was shown to be 0,1 kPa higher than atmospheric, and it last only approx. 10 milliseconds. Being skeptical, this may be due to a margin of error, nevertheless indicating minimal pressure losses in the air induction path. Location of MAP sensor has always been in its default location in M6x intake manifold. Although that being said, this data does not prove – nor deny – the existence of inertial supercharging, which can happen closer to a intake valve.

Log data showing minimal pressure loss, temporarily even above atmospheric pressure.

M60 Tuning: performance upgrade for hydraulic valve lifters

Search no more. You found the information in regard to performance upgrade for BMW M60 hydraulic lifters. They are also known as flat tappets, hydraulic tappets or just simply – lifters – they are all meaning the same – a hydraulic element which is in between your engine’s camshaft and valve, adjusting the valve clearance by utilizing hydraulic pressure. They are called flat tappets for a reason: the top of the lifter is flat, and while its moving up and down in relation to an engine speed, it is also rotating around its axis. Inadequate manufacturing quality (When using cheap Chinese parts) and the requirement for flat tappet rotation can create major challenges during a first startup, if lifter(s) will fail to rotate. This can lead to permanent cylinder head and camshaft damage.

Use appropriate cam lube during the assembly. Immediately after the startup, keep the revs continuously above the 3000 pm territory. This will ensure that new flat tappets can start to rotate along its axis. Do not let your engine to idle for the first 20 minutes! Higher rpm during a break-in period will provide both A) higher oil pressure for lifters and B) higher rotating force through camshafts

Engine comparison: M60 vs. M62 engine

M60 engine design is from early 1990’s. This means the engine was utilizing 35mm valve lifters used in both M50 and M42 engines. On M62, the factory wanted to reduce:

A) Rotating masses,

B) Increase the total efficiency of the engine,

C) Make the engine more quiet and sophisticated,

D) Reduce manufacturing costs

Thus the reason, why the factory ended up upgrading flat tappets on M62 to smaller diameter of 33mm. From the perspective of performance tuning, some of M62 modifications are not welcomed in terms of top rpm reliability, like the infamous change from “stronger-than-a-tank” duplex timing chain to a fragile single version. OK, let’s get back to lifters.

According to bmwfans.info, M60 hydraulic valve lifters weigh 78 grams,

While M62 flat tappets weigh only 52 grams, according the same source.

Please note: that is over 26 grams weigh reduction per valve-spring package! When you multiply that by 32, you can see, how the factory managed to save 832 grams from the flat tappets only!

Benefits of utilizing the lighter valve train on M60 engine

Because heavier M60 flat tappets require more stiffer valve springs, M60 engines have dual valve springs, while M62 has single ones. In terms of performance tuning, this can be either disadvantage, or advantage. The upside is: if you can find a way to reduce the overall weight of moving masses from M60 valve-spring package – without affecting the spring rates, you can get your valve train to sustain higher rpm range. And this is especially advantageous if you are after naturally aspirated performance tuning.

Our calculations show, that by reducing 20 grams from the valve-spring package – while utilizing both M60 stock valve springs – your M60 engine can sustain revs up to 8400 rpm. Ladies and gentlemen: it is on S65 territory!

Do I have to change my cylinder heads to M62?

No. You do not have to change your cylinder heads to M62, if you own M60 engine. Actually, the reality is the other way around: you may be interested in creating so called hybrid or frankenmotor with M62 bottom end matched to M60 cylinderheads – this will provide you prerequisites (Prerequisites only, thus most frankenmotor projects I have seen have failed to utilize this untapped potential) to build a high compression performance engine.

If you already have M62 engine, the advantage of hybrid motor is the upgrade to more robust duplex timing chain. The end result is pretty neat way to combine the best features from both engine families. Only downside is the heavier M60 valve lifters.

How to fix the issue of heavy flat tappets on M60 engine?

This modification is applicable if you are:

A) After performance upgrades,

B) Not worried about engine sophistication nor quietness,

C) Chasing for reliability on 7000rpm + category

You may have heard stories about fitting VW lifters to M42 318is engine, but you are lacking the proof of concept, right? Afterall, both M42 and M60 are using the same flat tappets.

Here is the proof of concept: I have successfully drove the M60 engine with VW tappets over 12 000 kilometers. Yes, they are not the most quiet, but they can take up the beating. My rev limiter was initially set to 7800 rpm. Afterwards, it was lowered to 7600 rpm. That is essentially the effective shift point in lower gears.

VW hydraulic lifters to BMW M60 engine

The VW valve lifters in question are manufactured by Febi Bilsein. They can be any brand you prefer. I ordered mine from autodoc.de – not the best service, but affordable prices.

The part number is 07060,

outer diameter 35 mm

Height: 26mm.

Weight: 56 grams

Happy E30V8 revving!

What ECU is the best?

A bit provocative question – and far too broad – in order to give you any simple answers. Basically, the most suitable ECU for your build is the one that suits the most for your preferences, which may vary a lot. Consider an ECU as an investment, where putting more money will get you both more features and quality in return. It is a return of investment. If you will break your engine due to lack of experience towards ECUs, their capability for warning limits and limp modes – it doesn’t matter – if you saved one or two thousand by selecting a cheap ECU in the first place.

The rule of thumb: If you are first timer, you will almost certainly buy a low quality ECU, regardless of all info provided on this blog article. If you are more experienced tuner, you most certainly recognize the importance of knock sensors, data logging, warning limits, extra connectivity and support, which more expensive ECUs will provide for you.

Let’s start with a common aftermarket ECU features. At first hand, these may seem minor issues on your list, but when time goes by, they will grow ever more important:

Checklist when buying an aftermarket ECU:

  1. Configurability of basic parameters (e.g. injector data)
  2. Ability to control IDLE QUALITY with hotter cams
  3. Ease of use and connectivity (e.g. stability, speed, future support)
  4. Longevity of both firmware and program support
  5. Quality and number of support in your country
  6. Number of extra inputs and outputs
  7. Number of knock sensors
  8. VE table configuration (a quite basic nowadays, thankfully)
  9. CAN support
  10. Full sequential support
  11. Warning limits
  12. High quality, wide band closed loop (For handling exceptions and monitoring)
  13. Ability to control up to x number of variable cams for your build
  14. Quality of data logging features: storing, reading and analyzing of data

One good example – actually a bad one – is Miller Warchip. They started with promising livechip feature for 1990’s bimmers, but when years passed on, company struggled to provide necessary support, leading to bad customer experience. If you still want to use Warchip, you are only good with legacy OS with legacy Java on Windows XP. ECU’s support for future upgrades is critical, thus you may have your build for decades. A financially stable company can provide you the best support for software upgrades in future.

How about tuning OEM ECUs? They can be divided into four main categories:

  1. Reprogrammable ECUs
  2. ECUs with add on ‘piggybacks’
  3. ECUs with livechip
  4. ECUs with switchable chip

The newer your OEM ECU, the easier it is to tune. What comes to M6x engines – they are type 2-4 ECUs. Most of us do prefer M60 OBD1 wiring harness and ECU, due to their simplicity for E30 swap. Thus ECU standards were under heavy development in 1990’s, you can face strange oddities in M6x ECU, like frequent EWS updates, or a sudden transition from OBD1 to OBD2. Generally speaking, ’99 model year is the milestone, when M6x engines were fully OBD2 compatible through KCAN interface. Luckily though, most M6x versions support live data logging through program called testo.exe, which I have explained here.

There is some evidence for BOSCH DME 3.3 ECUs having issues on both BMW M60 and Audi S6 engines on ’94 model year ECUs. Some of these, even with fully functioning live or custom chips can face strange oddities, if your build meets one or more criteria:

  • Your engine’s power range is extended to 7000-8000 and/or:
  • You are using bigger injectors, and/or:
  • Your stock MAF is not flowing enough, and/or:
  • You are using hotter cams -> a stock ECU cannot maintain idle -> an engine is stalling at traffic lights

Thus OEM M6x ECUs are somewhat limited for serious builds, it is advisable to turn your eyes on aftermarket ECUs. A bit surprisingly, OEM ECU can handle supercharging better, than building a hot street NA engine.

The problem most first timers lack to understand when selecting an ECU:

  1. ECU’s ability to control idle quality with hotter cams
  2. ECUS’s ability in normal driving conditions: cold start, cruise speed, stopping at traffic lights without stalling
  3. ECU’s ability to prevent a total disaster of your build: Setting up warning limits and limp modes

A list of warning limits any engine builder shall employ in order to trigger a limp mode:

  1. Continuous Oil pressure (OP) and temperature (OT) monitoring
  2. Continuous Fuel pressure (FP) monitoring
  3. Engine coolant temperature (CT) monitoring

In addition, following features must be monitored too:

  1. Knock detection for ignition compensation
  2. Warning limits for boost control (through MAC-valve)

Remember: the easiest part of your engine tune is to setup Wide Open Throttle (WOT) area of the map. It is the graph with nice looking power curve of your build. In reality, the most time consuming part is setting up an idle, cold start and driving quality for cruising conditions. And this is what you pay for.

Think about buying an ECU as an investment. By purchasing high quality parts, you can save big bucks in the long run, possibly avoiding a total disaster of your build.

Building a lightweight BMW M60/M62 engine

Did you know you can save up to 25 kilograms of an engine weight by selecting the lightweight components for your M60/62 build? This reduction can have a crucial effect for your E30 handling. Lighter, the better. Don’t be fooled by excessive weight of modern cars. They still follow the same laws of physics, no matter what marketing department puts us to think. Simply put, all modern BMW’s are too heavy for motorsport. They are not build for motorsport, as was E30 M3 in 1980s. And that is exactly the reason why we are tuning E30s. They are lightweight and offer you a unique driving experience – as if you are a part of a machine – a driving feel any reasonably priced modern car cannot offer for you. There is some lightweight hot hatches, but due to their FWD nature, they are excluded from the equation. Only on the day, when Formula One will switch to FWD, I can admit I was wrong with the amazing driveability, fun and excitiveness of FWDs…

So the weight is you worst enemy, thus your engine must be as light as possible, while providing an instant throttle response and a wide power range. Not so easy task, but doable for full aluminum V8 engine.

Please find below the table about the selection of the lightweight components, and their heavier counterparts:

Selection of lightweight components

Note 1: I excluded lightweight headers from the table, thus stock headers and lightweight custom headers are approx. the same weight, due to 4-1 nature of lightweight headers vs. stock headers with two primary pipes.

Note 2: Example above uses the lightweight hydrobooster from 7 and 8 series instead of a stock brake booster. This will have a double effect for your build:

  • No extra weight is moved forward
  • Hydrobooster is lighter than stock brake booster with a transfer kit

Note 3: Please note you can have further weight savings by:

  • Air condition delete
  • Catalytic converter delete (regulations will vary)
  • Keep windshield washer reservoir empty
  • Change bonnet to carbon fiber (-16kg)

With smart actions for weight saving, you can improve your V8 build’s handling substantially. Of course, there is more aggressive weight distribution tactics, like moving engine backwards, but I consider these too excessive for a street car. You can make your V8 behave like a dream by using the tips mentioned on this blog site. So how fast E30 V8 can be while cornering, if done right, you may ask? Probably faster, than your have the guts to put the pedal to the medal.

Performance tuning 101: Stop the guesswork and start measuring

Did you just click to my blog because you have been wasting hours and hours online, in order to find some crucial metrics for your build ?

My two cents: Stop wasting your time, and start measuring. This is a pretty basic knowledge, if you happen to have an engineering degree. Let’s have an example. You have been thinking if your fuel pump and lines has a sufficient flow for your build. Then you shall do the following:

  1. Attach 14 volts supply to your project cart,
  2. Detach a fuel line from a fuel rail,
  3. Find a bucket with measurement units,
  4. Bypass the fuel pump relay, and feed constant current to the pump,
  5. Measure how much your fuel pump and line will flow gasoline per minute (with 14 volts),
  6. Multiply this by 60,
  7. Done. Now you have the measured information about your fuel pump flow, in liters per hour.

Note: It is important to feed 14 volts to your fuel pump while measuring, thus this will increase the fuel pump flow compared to 12 volts, when your car is turned off.

Now you have the measured data of your fuel pump capacity. How about measuring a fuel consumption per hour in a full throttle then? This is a bit trickier to measure, because you need an access to live or logged data. The parameter we are looking is Engine Load (mg). This number will tell you how much your ECU is putting gasoline trough injectors per stroke.

Example variables for calculating fuel consumption:

  1. Engine load = 826 mg
  2. Revolutions per minute = 5900 rpm
  3. Two revolutions is required for a full power stroke

Calculation:

0,826g *5900rpm / 2 = 2437 grams of gasoline in a minute,

Whereas 1 litre of gasoline weighs 0,75 kilograms,

Thus fuel consumption is 2,437kg / 0,75kg = 3,29 l / minute

Fuel consumption per hour is 3,29 *60min = 197,5 litres per hour.

Now you have the exact, measured data. And we can tell, that your fuel pump shall have at least 200 litre per hour flow capacity + some overhead + reserve for future updates. In this example, 250 l/h pump would be a good choice.

Remember: stop guesswork and start measuring. It can take hours and hours of surfing on the internet, and yet – you have only assumptions – meanwhile you could be measuring e.g. a real capacity of your fuel pump.

My friend gave me a reminder after reading this article: fuel flow is in relation to fuel pressure. There is good charts out there about the correlation, like the one from tanksinc.com. More pressure will decrease a pump flow, so remember to put enough overhead for your calculations.

Stop the guesswork and start measuring. Today.

Performance tuning 101 for a naturally aspirated engine: There is no shortcut

Lately, there has been a trend among experienced tuners to turn their eyes back to naturally aspirated engines, thanks to their ever challenging and unforgiving nature. Their is just something fascinating in a high revving naturally aspirated engine, especially in a V8.

Let’s admit: If you are interested in maximizing horsepower: buy a turbocharger. It is the easiest way to add power to your engine. But if you are like me, you are not interested in max hp. You may be allergic to turbolag, and interested in faster-than-light throttle response, in order to maximize the traction and driveability. Mate, this is the right blog for you. It is not about maximum hoos pauwo. It is about maximizing your fun, while you are driving along 101 on a west coast, or where ever you are enjoying your E30. In these situations, 300 to 400 engine horsepower and steady 400-500 nm of engine torque is much better than a galaxy exploding power curve. On rear wheels with 4th gear it means approx. 1500-1900nm of torque, if you are using a 5 speed ZF S5D310 and 3.15:1 ratio differential. You can consider 2000nm of rear wheel torque the upper safe limit for twisty (and both dry and clean) roads with 225 semi slicks. Just put the fourth gear on, and start enjoying.

The general idea is, that you may seek for more speed, but you may not be able to put any extra torque to rear wheels, or otherwise you may loose traction. This seems to be pretty tricky for folks to understand. It is the torque on rear tires that makes your driving either fun, or scary and difficult. And that’s why an electric car can be very fast on a track: they are providing steady torque, without any interruptions whatsoever. It means they are easy and logical to drive up to the limit. It is the same reason, why modern BMW diesels have even four turbochargers.

If you are living in the U.S, its pretty straightforward to install a LS engine into your E30, and start enjoying. While in Europe, M6x is popular swap due to a high number of potential engine donors available. And that makes it interesting tuning project for E30. With a basic M6x swap, you can get up to 286 hp for your E30. So your motives to build an engine swap may vary where you live at. M6x is very capable engine, and will response into a tune like any other engine.

Why not M5x then? the V8 has both more displacement and valve area than its little sister – making it the better choice for a NA build. There is no replacement for displacement – the V8 is basically a two four pot 16-valve 318is engines in the same. But if you are going to turbocharge your engine, the six pot can be better starting point, thus its much cheaper to rebuild with forced internals. Turbocharging M6x is more expensive, requires high demand from powertrain, and all these will add tens of kilograms of unnecessary weight on a front axle.

If you are about to keep your engine NA – go for V8 – and keep it as light as possible, thus it is one of the keys for good handling. Even among NA M6x builds, you can save up to 27 kilograms from a front axle, only by making smart decisions for your build. But V8 is still so heavy, you may say. Well, it can be either a true or false. A well built M6x swap is equal in weight to a stock E30 325i. I know this, because I’m a guy with two engineering degrees, and being taught to measure, before start making any hypothesis. In full driving condition, including all fluids and 3/4 of gasoline E30 weights 1180kg with M60 engine. It is in the par with the stock E30 325i. It is a bit of a surprise, but M6x cylinder block is lighter, weighing only 28 kilograms, than a good old four pot M10 block. The name of the game is aluminum.

A good reminder if you are first-timer in performance tuning, please repeat with me: A naturally aspirated engine is as strong as its weakest link. So tuning NA engine is like drinking a fine vine: there are no shortcuts in the making. Repeat with me: there is no single shortcut. Not only horsepower figures, but also the quality of your build through lightweight parts has to be taken into account. Many times the information from public bimmer forums is limited what comes to NA M6x performance tuning. You must face it: Tuning a naturally aspirated engine is an expensive task. If you have extra penny to spend for performance tuning, then go for it. If you don’t have, it may be advisable to stick with a stock engine.


M60 stock crankcase ventilation valve problem: its design fault and insufficiency for performance tuning

There are excellent articles out there about faulty Positive Crankcase Ventilation (PCV) systems, like the one on Timm’s BMW E38 Repairs and information page. PCV or Crankcase Ventilation System (CCV) is basically the same valve with a different name, only acronyms may vary.

This article is from the perspective of performance tuning. If you are about to install hotter cams, raise compression or rev limiter, it is important to understand the design flaw in a stock M60 PCV system. The described mods typically increase engine performance, but also put more stress – and blowby – through the engine. These blow-by gases are the reason, why there is a system called Positive Crankcase Ventilation in the first place. Thus, when you increase stress to your engine by increasing both compression and rpm, you will increase the amount of leaking gases to a crankcase. This will put increased demand to PCV system to do its job.

Unfortunately, the stock M60 CCV design is faulty from the factory. It does not matter if you replace the item with a new one – it is not up to its task, more less when you are doing any performance upgrades.

The main havoc for the stock PCV system is the design: all gases and residue will accumulate in the front of cylinder 8 runner. When there is enough sludge, and you accelerate hard at the same time, the cylinder in question will gulp all the residue into the combustion chamber. The result is pretty obvious: the Pope like white smoke is a testimony of compromised combustion chamber process, with excess oil.

M60 intake cover with Positive Crankcase Valve, PCV. Sludge will build up next to a cylinder 8 runner, and eventually find its way to the cylinder like a big gulp. Hence the occasional white smoke, when accelerating hard to a highway.

Installing an oil catch tank

One option is to bypass the stock PCV valve, and install an oil catch tank for residual gases. This can be done by modifying the stock PCV valve, and rerouting gasses to the tank. Other option is to purchase a new rear plate for intake manifold. The oil catch tank was acquired from BjörkMotorsport.

Rerouting a stock PCV valve for external oil catch tank.

Oil catch tank in place.

M60/M62 tuning: An intake manifold upgrade

The factory has provided at least four different intake manifolds for both M60 and M62 engines. If you have studied anything about airflow, its obvious to select the manifold with the best possible velocity stacks for optimizing the engine performance. Velocity stacks – also called as trumpets or horns – can increase maximum airflow approx 2-4 %, but the benefit may be even higher in mid-range torque due to intake resonance. The science behind trumpets is their ability to smooth out incoming air, maximizing airflow to intake runners.

Source: Wikipedia, Velocity stack detail.gif, credit for user Motorhead.
Picture published under GNU Free Documentation License.

Disclaimer: tuning a naturally aspirated engine is as strong as its weakest link. Cams, valves, cylinder head, headers, collector – and most definitely “the hot air intake system” may be hindering down the power and torque in your build. Thus, the benefit of changing the manifold depends on both level and quality of modifications you have made for your car.

Different intake manifold versions:

M60B30 and M62B35 – These are with smaller runners, so we will forget these.

M60B40 model year 1992 – Large runners with the best velocity stacks

M62B44 Nonvanos – Large runners with minor bends at intake runners

B62B44 Vanos – Version with small runners, so we will forget these too

The best option: Ultra rare M60B40 model year 1992 manifold with proper velocity stacks for maximum air flow.
The second best option: M62B44 Nonvanos intake. Note the pipe in the middle for distributing blowby gasses more evenly to all cylinders. You can read more information about Crankcase ventilation design fault from the other blog article.

There are four hypothesis, why BMW quit developing 1992 version of the manifold so soon:

  1. Factory may have wanted the best possible features and grunt for intimidating the press, when the new M60 V8 engine was introduced.
  2. Guys at the department of finance wanted to cut some costs. We know how expensive these engines are to build. Take for example M60 timing gear with duplex chain. The level of design and robustness is closer to a tank.
  3. Velocity stacks are prone to get loose. Simply put – why bother, if you can cope without them, and avoid any warranty issues.
  4. E34 540i may have been too close in terms of performance to E34 M5. Please check the youtube video about the matter.