Dave Walker of Emerald M3D on Modifying Cylinder Heads for Performance

Summary

In this video, Dave Walker from Emerald M3D discusses cylinder heads, specifically a supercharged Mini's first-generation BMW R50/R52/R53. He explains the engine's collaboration with Chrysler, its 1.6L capacity, and the challenges of forced induction. Dave demonstrates the importance of porting and polishing for gas flow, using a flow bench to measure air flow and valve lift. He emphasizes the value of quantifiable data over opinions, highlighting the process of head development and the quest for improved engine performance.

Takeaways

• 🚗 The conversation is about cylinder heads from a first-generation BMW R50, R52, R53 Mini Supercharged engine.
• 🔍 The engine is a collaboration between BMW and Chrysler, used in the Cooper S from 2001 to 2006.
• 🏎 The engine has a 1.6-liter capacity with a supercharger, originally designed as a naturally aspirated engine.
• 🛠️ Porting and polishing cylinder heads can improve their appearance but does not necessarily increase power.
• 🔍 The shape of the port is more important than the shine for performance improvements.
• 🔧 The script discusses the process of smoothing out casting imperfections in the cylinder head.
• 📊 A flow bench is used to measure the air flow through the cylinder head, providing quantifiable data rather than relying on opinions.
• 📉 The script explains how the flow of air stops increasing after a certain valve lift, which is important for camshaft design.
• 🔬 The use of a flow bench helps to determine the optimal valve lift for maximum flow, avoiding unnecessary mechanical stress.
• 🔩 The script mentions the importance of aligning the cylinder head correctly on the flow bench to ensure accurate measurements.
• ⚙️ The conversation also touches on the historical development of flow bench technology and its evolution from manometers to electronic sensors.

Q & A

What type of engine is being discussed in the script?

The engine being discussed is a first-generation BMW R50, R52, R53 Mini Supercharged engine.

What is the engine's capacity and what modifications were made to it?

The engine's capacity is 1.6 liters and it was originally designed as an aspirated engine. Later modifications included adding a supercharger.

What is the purpose of the supercharger in the engine?

The supercharger is used to force more air into the engine, which can increase the engine's power output.

What is the significance of the cylinder head in an engine?

The cylinder head houses the valves and plays a crucial role in the engine's performance by controlling the intake and exhaust of gases.

How does porting and polishing affect the engine's performance?

Porting and polishing can improve the shape of the cylinder head's intake and exhaust ports, potentially increasing airflow and engine performance. However, polishing alone does not increase power output.

What is a flow bench and how is it used?

A flow bench is a device used to measure the airflow through an engine's cylinder head. It helps to quantify the effect of modifications such as porting and polishing.

What is the importance of valve lift in terms of airflow?

Valve lift determines how much the valve opens, affecting the amount of air and exhaust gases that can flow in and out of the cylinder. However, there is a point where increasing lift does not increase airflow.

Why might an exhaust valve be lifted more than necessary?

An exhaust valve might be lifted more than necessary to reduce the stress on the valve train and to make the valve spring's job easier by reducing the abrupt stop at full lift.

What is the typical exhaust flow percentage in relation to inlet flow?

The exhaust flow is typically around 70% of the inlet flow, although some heads can reach up to 80%.

How does the position of the cylinder head on the flow bench affect the results?

The position of the cylinder head on the flow bench must be aligned correctly to ensure accurate measurements. Misalignment can lead to artificially higher flow readings.

What is the purpose of the manometers and probes used in the flow bench?

Manometers and probes are used to measure the pressure drop across the cylinder head and to probe the airflow within the ports, helping to identify areas of restriction or inefficiency.

Outlines

00:00

🔧 Cylinder Head Discussion

Dave Walker from Emerald M3D discusses cylinder heads, specifically a supercharged Mini engine from the first generation BMW R50, R52, R53 series. The conversation covers the engine's collaboration between BMW and Chrysler, its 1.6-liter capacity, and the addition of a supercharger to the originally aspirated design. Dave explains that while polishing the head may make it look better, it doesn't necessarily increase power. The discussion then dives into the importance of the head's shape over its appearance, mentioning the removal of a valve and the presence of a lump in the casting. Dave also talks about the use of a flow bench to test and measure the airflow through the engine's ports, emphasizing the need for quantifiable data over opinions.

05:01

📏 Flow Bench Mechanics

The discussion continues with Dave explaining the mechanics of a flow bench, which is used to measure the airflow through an engine's cylinder. He describes the process of using manometers to measure airflow, mentioning that the harder you 'suck' or the greater the depression, the more air flows. Dave details how the flow bench operates, using a constant depression of 10 inches to measure airflow, and how he uses a computer program to convert the readings. He also shares historical context, noting that in the past, heads were modified and tested by eye, but now there are more precise methods. Dave also explains the importance of measuring airflow at standard settings and after modifications to see improvements. He mentions the use of a manometer to probe airflow within the port and the value of this data in optimizing engine performance.

10:01

🔩 Practical Porting and Grinding

In this segment, Dave talks about the practical aspects of porting and grinding cylinder heads. He shares a tip for using plasticine to test airflow changes on a flow bench, suggesting that if making the port smaller doesn't decrease airflow, then making it larger won't improve it either. Dave reflects on his experience with hand tools during his apprenticeship, mentioning a task to file a piece of steel to an exacting tolerance. The conversation concludes with Dave discussing the use of the flow bench to determine the optimal valve lift for maximum airflow, emphasizing that there's no point in lifting the valve higher than necessary unless for mechanical reasons. He hints at ongoing engine development and the anticipation of testing the modified head on an engine to measure its performance gains.

Keywords

💡Cylinder Heads

Cylinder heads are a crucial component of an internal combustion engine. They house the valves that control the flow of air and fuel into the combustion chamber and the exhaust gases out. In the script, the discussion revolves around the design and modification of cylinder heads, particularly for a BMW engine, to enhance performance. The hosts discuss the original design of the heads and how modifications for supercharging can affect their efficiency.

💡Supercharged

Supercharging is a method of forcing more air into the engine's combustion chamber than it would naturally draw, which allows for more fuel to be burned and thus increases engine power. The script mentions a mini supercharged engine, indicating that the original design was aspirated, and the supercharger was added later, which could potentially compromise the design as it was not originally intended for forced induction.

💡Porting and Polishing

Porting involves modifying the shape and size of the intake and exhaust ports in the cylinder head to improve airflow. Polishing refers to the smoothing of these ports. The script clarifies that while polishing may make parts look better, it does not necessarily increase power. The shape of the port, however, is critical for optimal gas flow, which directly impacts engine performance.

💡Flow Bench

A flow bench is a device used to measure the airflow through an engine's intake and exhaust systems. It's essential for quantifying the effects of modifications like porting and polishing. In the script, the flow bench is described as a 'giant vacuum cleaner' that simulates the cylinder and measures how much air flows through the head at various valve lifts.

💡Valve Lift

Valve lift refers to the distance a valve travels from its closed position to its fully open position. The script discusses how excessive valve lift can be unnecessary if it does not contribute to better flow, and it may be done for mechanical reasons, such as reducing stress on the valve train.

💡Manometers

Manometers are instruments used to measure pressure differences. In the context of the script, manometers are used on the flow bench to measure the vacuum pressure created by airflow through the engine's ports, which is directly related to the volume of air that can be drawn into the engine.

💡CFM (Cubic Feet per Minute)

CFM is a unit of measurement for volumetric flow rate, indicating how much air is moved through the engine's ports in a minute. The script uses CFM as a benchmark to compare the performance of standard and modified cylinder heads, with higher CFM readings indicating better airflow.

💡Camshafts

Camshafts are mechanical devices that control the opening and closing of the engine's valves. The script hints at a future discussion about camshafts and their role in engine performance, particularly in relation to valve lift and timing.

💡Inlet and Exhaust Flow

Inlet flow refers to the amount of air entering the engine, while exhaust flow is the amount of exhaust gases being expelled. The script discusses the relationship between inlet and exhaust flow, noting that exhaust flow is typically around 70% of inlet flow, and that improving exhaust flow does not always translate to increased power.

💡Hydraulic Followers and Rockers

Hydraulic followers, also known as hydraulic lifters, and rockers are components of the valve train that facilitate smooth valve operation. The script mentions these components as part of the engine's design, suggesting that they contribute to the engine's overall performance and reliability.

💡Mechanical Reasons

Mechanical reasons pertain to the physical aspects and constraints of an engine's operation, such as the need to protect valve gears or reduce wear. In the script, it's mentioned that valve lift may be increased for mechanical reasons, such as to reduce stress on the valve train, even if it doesn't directly improve airflow.

Highlights

Discussion about cylinder heads with Dave Walker from Emerald M3D.

Introduction of a first-generation BMW R50 R52 R53 engine.

Engine capacity is 1.6 liters with a supercharger.

The head was originally designed for a naturally aspirated engine.

Porting and polishing do not inherently increase power.

The importance of valve shape over polishing for gas flow.

Valve machining issues and how they can be smoothed out.

The negligible gain from smoothing out machining marks.

Explanation of how a flow bench works.

The relationship between valve lift and flow.

The role of camshaft design in valve lift.

The discovery that misaligned heads can affect flow.

Old-fashioned flow bench versus modern electronic sensors.

The process of measuring airflow with a flow bench.

The historical context of airflow measurement in engines.

The impact of exhaust valve opening on gas flow.

The practical tip of using plasticine to test airflow restrictions.

The anecdote about filing a piece of steel to exacting tolerances.

The use of manometers to probe airflow within ports.

The importance of measuring airflow to determine valve lift.

The practical application of flow bench data to engine performance.

The anticipation of testing the modified head on an engine.

Transcripts

all my life I've always wanted to

measure I'm not interested in

opinions hi it's will at practical

performance car and we're here with Dave

Walker emerald m3d and we're going to

talk about cylinder heads what have you

got here what's this head from um this

is off a mini supercharged that's the

first generation first first generation

BMW R50 r52 R53 right uh the 52 was

convertible otherwise a heads are all

the same but this is a a BMW engine is

it uh it was a a collaboration between

BMW and Chrysler it was on the Cooper S

from I think

2001 up to 2006 right and what capacity

is the engine then uh 1.6 right so it's

quite a small engine yeah Deton for I

think 45 supercharger but I mean heads

the head um it was originally I believe

designed just as an aspirated head oh so

without the supercharger without

supercharger and then when they decided

to do the Cooper S I think they decided

to go superchar that makes sense yeah

well does that compromise the design of

the head as far as it forc induction

yeah I think it does um this is not one

of the best heads I've ever seen right

um yeah but today if we're just talking

about porting and polishing and gas flow

various terms uh um there is no gas uh

we we we're changing the shape the

polishing is just a cells thing if it's

not shiny you can't set it so the

polishing doesn't gain you any power no

it doesn't gain you any power the thing

that matters is the shape right so um

I've taken some valves out this one's

particularly bad on it there's quite a

lump in there isn't it there's there's a

big step yeah and is that just left from

the casting that's just left from the

machine in the cting is there and it's

machined down to that depth M um oh then

they just stop and then it just stops so

then you just so you got a big step and

it looks horrendous but I can tell you

now because I've already done the work

um you can smooth all that out and I've

got um I've got a port here if you look

in there where I've taken all the step

and everything out and I gain almost

nothing really cuz that you think

looking at the

standard massive restriction and that

looks lovely yeah but the game looks

much faster though oh yeah yeah yeah but

it's not and it will be it will look

much faster if I polish it would yeah it

would and it's easier to sell yeah but

it makes no difference it was I W say it

was a waste of time cuz it doesn't take

no well you wouldn't know that's why we

have the flow bench so if I can just

explain how um flow bench works um when

you first get a flow bench the first

thing you discover is that a big hole

flows more air than a small hole really

yeah yeah amazing is it how expensive of

flow Benes cuz I I reckon I could have

guessed that well yeah exactly yeah uh

the the the trick is that to get the

shape that gives you the best flow for

the given M size and that depends on how

high you're lifting the valve if you

look at this one here this uh exhaust

valve um it's way over lifted on most of

the cams that you get for these engines

because the flow stops about 250,000 so

why do they bother opening it further um

it's to do with the uh design of the cam

and giving the spring an easier life cuz

if you fire that open to 2 stop dead it

wants to carry on right just from in

yeah from inertia and it will just float

off the end of the cam right so you can

only accelerate them so fast the other

problem you can get the these are an

exceptionally good in that respect cuz

they've got a roller follower but if

you've got a conventional follower where

the cam lobe is rubbing against the

follower if it accelerates too fast it

squeezes all the oil out between the cam

and the follower and they wear out right

that was the classic problem with a pin

I thought you might mention that

Dreadful things yeah so you don't need

big lift uh on the

Cs especially on this head so if we go

over to the flow bench right let's do

that then so now now we've moved over to

the flow bench um Talk us through this

if you could right basically this is

just like a giant vacuum cleaner and

we've simulated the B size here so we've

got a tube under there that represents a

cylinder B oh so that's a similar size

to The Bard will be on this it is if I

lift that up you can see the adapter in

there oh yeah the B size and I've got

those two studs so that the head lines

up exactly square with the bar that's

really important because uh some engines

like t4s um if you move the head across

to one side so it's not Central you

actually get more flow through yeah and

the guy who discovered that Peter

Burgess good man he discovered it

because he put the head on and he'd got

a flow game and he hadn't done anything

right uh but it's cuz it wasn't lined up

right so now everyone knows that tweet

but he was the original um guy who did

it I always like to give credit where

credit is due absolutely yeah so this is

a very oldfashioned flow

bench um it's about 30 years old right

same as me um yeah I was going to say

looking and um so this is all done on

manometers nowadays if you get a flow

bench if you're going to have electronic

sensors in there you don't need any of

this stuff right but I use it so little

now it's only like a hobby thing there I

don't do heads for a living anymore no

so um I'm I know it I'm quite happy with

it and the way it works is obviously the

harder you uh suck or the greater the

depression for the technically minded

the more air flow you you flow so you

need a constant and the constant on this

one is always 10 in of um depression

right so you have to have somewhere

holding the valves open and I made this

with have two do gauges so that I can

open the valves uh the same amount and

then take a flow reading right now this

monometer is very short some machines

that would be going all the way down the

floor in the old days in the 50s um but

superflow came up with this idea that

that represents not to 100% of each hole

oh right so you just bung the holes up

you just bung the holes up so at low if

I

just up at low flow you leave all the

buns in like that it's just a into that

small hole it's only coming it's only

measuring a percentage of that so you

set that say I always I'm I'm th on on

lift for some reason so I set it at

50,000 of an inch lift start the thing

up adjust the depression until I've got

10 in take a reading and then I've got a

little computer program that KL did for

me uh to convert it but you can just

look on the graph and that'll just give

you a good idea of what's going on and

it's measured in CF CU yeah cubic feet

per minute right want some sort of

numbers go back to the good old days of

the four Pinos a standard head would

flow about 85 CFM on the inlet right and

the big race heads that I used to do

would come out about 120 wow that's

quite different yeah exhaust flow

similar sort of games on the on um

Pinto's exhaust flow was never a problem

I did lots of uh work to improve the

exhaust flow never found any more power

right as a general guide F seem to work

on about 70% of of the inlet flow you'll

find on the exhaust on nearly all their

heads that I used to do um and I've

ported them up to 80% which is what

superf flows say you need and never s

any gam right so if you can get 70%

you're doing okay the thing is with the

exhaust when that valve opens to to let

the exhaust gas out the Pistons only

sometimes not even reach to bottom dead

center so you've got tremendous

combustion pressure still in there yeah

and um I've seen uh footage uh through a

quartz window of the gases and as soon

as that valve opens it's gone right

you're not relying on a piston coming up

interesting that's how I sort of

envisioned it was the Piston was pushing

the exhaust gas out that's not the case

no that's what we we all call it suck

squeeze bang blow but yeah as soon as

that opens the pressure difference it's

gone right and then you um it's another

story we're getting cam shafts on

overlap we'll do that another time we

can do that another time so there's your

flow bench so what you do is 50 get a

reading 100 150 and you will eventually

you you'll have a a curve and so the

whole point of this is that you measure

it when it's standard yeah and then when

you make a modification you put it back

on and see whether you've gained

anything and if so how much is it any

better years ago people used to just

sort of do it by eye you know you could

look at it and go I don't think the air

is going to turn that corner very well

I'll grind a bit out here and there and

the first guy that I know of who

actually tried to measure something was

uh you remember him Bill Biden's name

yes I do smashing POG team

deox but he started out using Walter he

he built a thing there and he had a plug

and he timed with his

stopwatch go through it doesn't it

doesn't cuz Walter doesn't compress I

suppose it maybe it doesn't behav in the

same way as but it was an attempt to

measure thing yeah and like all my life

I've always wanted to measure I'm not

interested in opinions you know if it's

better or it's worse I want to know by

how much and I want something

quantifiable right fair enough yeah

something build on it feels faster

something repeatable feels faster don't

cut it yeah that's basically what you do

and I I got this manometer which um I

made some little um pedo tube probes so

I can put that inside there and probe

the port and see where abouts the air

flow is if there's more at the top the

bottom the left or the right I can probe

that round uh so that gives you an idea

of where idea of where

you and a tip if you if you ever get a

flow bench when you first start a good

tip is um if you think you need to cut

more away say from the bottom of the

pork if you get something in there like

a little bit of plasticine and just

build up the

restrictor if the flow doesn't drop

making it smaller hasn't made it worse

so making it bigger is probably not

going to make it any better but if you

do get a drop then it's worth having to

go sometimes you have to sacrifice a

head it's going to say probably more

than one oh well you get four goes at it

on a four cylinder so true once You'

destroyed one doesn't matter anymore

does it you know you just like get get

carried

away the the actual physical side of the

porting and grinding is that's another

story all together I was just telling

Ben um I think it was you that told me

when you did your apprenticeship one of

the tasks that you were given was to

take a piece of Steel and file it into

an absolute yeah 5 black bar it had to

be half inch what was the toleran 5,000

of an inch 5,000 of an inch yeah I'm

actually pretty good with hand tools

yeah but if you went under they throw it

in the bin and make you start again I

they wouldn't let just make you oh no no

smaller no no have to be right okay well

thanks very much okay um just trying to

think what else I can can tell you about

flow benches it's a as I say it's a t um

if you make that hole massive it's going

to flow more air but it doesn't

necessarily mean to say it's going to go

any better but the the the the one of

the main things I use it for is to find

out how high you need to lift before the

flow stops right cuz there's absolutely

no point in lifting the Val further

unless you're doing it as I said before

for mechanical reasons you know to

protect the Val gear okay great 5 Ines

are

great you can measure things all right

thanks well maybe we could get you to

fire it up yeah I can make some noise

yeah yeah you have to plug it in that's

um I'm working on that one

there you go you want to switch it on as

well Dave hey you want to switch it on

as well is it not on can't see yeah um

right I'll just go stupidly for

LIF try

again that's why that valve is there

catch idiots like me um who are trying

to get a massive flow through that

little diddy diddy hole so yeah full

board take a

reading

about

78% so then you just go here to the

number of B 7 take a reading I won't

tell you what it is because that's what

I've been playing with and I'm keeping

that quiet at the moment okay fair

enough yeah all be revealed at some

point oh yeah yeah yeah I um once I've

finished the head development I'll put

it on the engine with no other change

and see what it's worth this is a single

cam head is yeah right yeah and

hydraulic followers and Rockers it's I

like it okay we'll uh we'll come back

when you're ready to put it on the

engine yeah yeah don't hold your breath

cuz it's a side project okay okay well

thanks Dave um hopefully by the time you

get this head finished and back on the

engine we'll be a to come back and yeah

def see what kind of power game yeah

yeah yeah yeah let's cut through the

nonsense and uh and measure things okay

we'll see you there we'll give you the

power output the talk and we'll have the

flow figers to back out great okay look

forward to it thanks Cheers Cheers