is it possible to improve m20 intake? s14 stylee?

[liam012]

bar individual throttle bodys i have always like the idea astheticly of a polished intake plenum the same size as the rocker cover along side it if that makes any sense though i hve always failed to contemplate the techanical obstacles?
i am presuming the oem intake can be improved upon just because most things can but i was against throttle bodys due to loss of torque and mpg despite sexy rude sounds. i have since learned it is not always the case i guess something like an s14 intake system would be nice allright. and i have megasquirt ready to install too
I was wondering if you could cut the standard intake so only the 1" of it that bolts to the block is left and to that you could add some form of throttle bodies and around all that could be a pluenum?
I really dont know much aboutthis sort of thing especialy the calculation of optimum throttle body sizes etc.
Any body else thought about this or know of any good solutions
my aim is to improve torque more so than bhp but at the moment i dont even know if its feasible.

[liam012]

i am only getting the ball rolling here to inspire a few "hell no, man you cant do that because..." replie but how about something based on the below principle? what is the rule of thumb? that all intake runners must have equall length from beginiing to end so some will stick into the chamber more? also if i kept enough of the original intake i could maintain the injector positions. I appreciate to those who know about this stuff this may sound stupid but its something i've had rolling around my head for a while so would like to know if its even worth looking into!

[Turbo-Brown]

If you were to cut the mani down to a set of stubs and just attach throttles to those, you most certainly would lose torque.

If you design your system right so that the lengths of the inlet runners are either the same as the originals (longer or shorter depending on engine spec) you should gain torque and therefore power everywhere

It is most definately worth looking into dude!

[liam012]

this is where i am lost
what dictates length and diameter of the runners (and where the butterfly is)?
is there any website that has those funky calculators or second place a good article!
what is generally the case longer runner = more or less torque
does volume come into play?
ie: 1cm diameter by 10cm length is more or less efficient than a runner with less volume but a longer length?
i feel dizzy!
time for google - i suppose if i can at least find out what oem runner length and diameter is that would be a start...

[Demlotcrew]

I cant see how you would loose lbft and mpg. Anything that optimises the inlet track will not only gain power but also improve the economy of the engine.

I got 36mpg all the way to Germany with my S14 (mixed speed/load driving)

Show me a M20 with the same power getting those figures.

Andrew

[liam012]

yes i said in my first post that i had it wrong andrew which is why i want to work on something simmilar,
thing is i know very little about how to design the optimum inlet tract for a given capacity engine for a desired characteristic (outright power or even gains). maybe my google search skills are waining but i am turning up little on the science of the subject.

[liam012]

mm so this is how the m5 did it, what is it that makes throttlebodies better? - as if i try and fab something with runners into a plenum which has one butterfly that wont be so bad -
but making a unit with individual butterflies does seem a more expensive mammoth difficult task for someone like me.

[Gravy]

As I recall from my inlet manifold resdeign project thingy at Uni, the longer the intake pipes, the torquier the end result (and vice versa). Although if they are too long the air will slow down too much and strangle the intake of air (I think!)
Also, despite my initial thoughts, a rough / coarse internal pipe surface is actually better than a smooth one becuse it creates turbulence into the inlet plenum which is a good thing because all the air is stirred up and used instead of leaving small pockets of slower moving / static air in corners of the internal surfaces. It is more efficient in other words.

Doesn't fully answer your question but could help a little bit!

[Toby_Unna]

Anything that optimises the inlet track will not only gain power but also improve the economy of the engine.

Andrew

optimal at 8k revs doesn't necessarily mean optimal at cruising speed - in terms of both mpg and power.

Show me a M20 with the same power getting those figures.

Andrew

the s14 is more efficient due to various factors (including the inherent reduction in mechanical loss due to fewer cylinders). throttle bodies have f**k all to do with it

[Turbo-Brown]

Very broadly speaking, longer runners will favour low end torque, shorter runners favoring top end power.

Throttle bodies provide less overall restriction to flow than one throttle attached to a plenum whilst also preventing interaction between cylinders caused by hairy cams which you can't really do with a plenum intake.

Throttle response should be made sharper the closer the throttles are to the head with the plenum being the worst setup for throttle response.

The slightly rough surface finish of the runners: This promotes the formation of a layer of still(ish) air next to the wall of the runner or port. Moving air moves much more easily over the stationary air than a stationary surface giving the better flow when compared to a polished surface. Drawn tubes seem to exhibit good flow characteristics so have a look at them for surface finish perhaps.

[Demlotcrew]

Anything that optimises the inlet track will not only gain power but also improve the economy of the engine.

Andrew

optimal at 8k revs doesn't necessarily mean optimal at cruising speed - in terms of both mpg and power.

That doesnt make sense, who said anything about RPM? Its quite obvious that you need less throttle in a powerful engine to make it produce the same power as a engine with less power. In the real world i dont need to press down on the accelerator in a M3 as you would in a 316i to make the car accelerate as fast.

The four stroke engine is very simple when broken down to its principal operation, its a big pump and if the inlet is optimised then the pump can move more air in a given time than it would normally if the inlet was restricted.

But with throttle bodies its not just that simple, the exhaust side of the equation needs particular attention and so do the cams.
Its a whole package.

Show me a M20 with the same power getting those figures.

Andrew

the s14 is more efficient due to various factors (including the inherent reduction in mechanical loss due to fewer cylinders). Throttle bodies have f**k all to do with it

Again i didn't say anything about throttle bodies being the one and only factor of the efficiency of a S14. Now i really don't see how two cylinders would really affect the friction on an engine so much that it would adversely affect its MPG/Performance as we would all be driving one cylinder cars.

Remember compared to the M20 the S14 is chain driven, has two cams, larger bores, solid buckets which all adds to the friction/weight you are referring to.

Andrew

[Toby_Unna]

Now i really don't see how two cylinders would really affect the friction on an engine so much that it would adversely affect its MPG/Performance as we would all be driving one cylinder cars.

Remember compared to the M20 the S14 is chain driven, has two cams, larger bores, solid buckets which all adds to the friction/weight you are referring to.

Andrew

don't make yourself look silly Andrew

A roller chain has in the region of 98% efficiency, it's a very clever device

and as for the friction thing, well, can you point me to a four cylinder engine of M20 performance and technology that is quite so fuel-inefficient across the board?

i'm surprised you don't agree tbh - after all, these are both areas that make your little S14 look good

and we don't all drive one cylinder cars for reasons of.. refinement. you muppet.

[liam012]

thanks for your input guys but this is a thread i have started about someting i have been interested about for along time and was looking for help and info so i could learn a bit and maybe knock something together.
so whether its telling us how great the s14 is or snide comments about 'smaller' cars , i couldnt care less as long as you do it somehwere elese. maybe i am miiss interpreting this as friendly fire and you two are 'chums' but i would be grateful for OT stuff please.
There are so many threads on the zone now with handbags and lipstick in it is getting silly and can see myself visiting here less and less because of it.

[Demlotcrew]

Agreed a roller chain is efficient but the associated hardware to make it work is not, which is why modern ///M engines have improved on the design even further.

No i don't know of any engines which have four cylinders, two valve per cylinder and the same bhp/mpg per litre.

(But that doesn't mean there are none)

My little S14 doesn't need to look good because it is good unlike your scrapheap challenge attempt.

OT but i would like you to call me a Muppet to my face

Andrew

[Toby_Unna]

Sorry Liam

to be honest I was just a bit bored

ok back on topic.

[oldroydsr4]

To get the ideal runner lenght pulse tuning is required, depending on the peak torque and power at a particular rpm.

Ill find the equation and post it.

[liam012]

your sig looks most helpful toby! i can only presume thats not standard m30 intake??

oldroydr4 that would be super mate

[oldroydsr4]

I don't know if this helps but.

Pulse tuning

The maximum speed that air can travel at is the speed of sound. In ambient conditions, this is approximately equal to 330m/s. At approximately maximum valve lift, the speed of air through the inlet tracts is a maximum with the narrowest opening providing increased pressure for the ultimate maximum air speed. If choking was to take place i.e. when the air speed reaches 330m/s, it would be at the narrowest region. The fastest air speed will be assumed at the port mouth at 330m/s
At full lift, a suction pulse is created at the valve opening and travels to the bell mouth at 330m/s. At the bell mouth, it draws in air which travels back to the valve opening at 330m/s. This provides the cylinder with further air for combustion.
This process repeats itself and provides the cylinder with further pulses of air until the valve is closed.
The number of air pulses making it into the cylinder is proportional to the length of the induction tract, the temperature of the air and the engine speed.


Inlet pulse tuning equation

L = (330 / 2) x (C / 360) x (60/RPM)

where C = Full lift to effective closing of inlet camshaft

The calculated length is from valve face to ambient (plenum)


Im sorry if this is useless, but iv just done some crappy assignment at uni involving it.

[Toby_Unna]

Liam,

they're the same intake as on the M5 engine you showed above.

these are a bit too big for a standard M30 head, which doesn't breathe that well. nice throttle response and noise though.

[liam012]

sorry if i am silly but is full lift there measured in degrees, height or time!!!?

and also there is no accounting for optimising for engine capacity or at least cylinder volume?

And to clarify the inlet tract; thats bassicly measured in this example from the valve face in the cylinder bowl to where the tract finishes and opens up in the plenum? it wouldnt matter where the actual butterfly is as the tract is what "launches" or "projects/guides" the air into the cylinder and when it is open it theoreticly could be open anywhere?

sorry i am just feeling my way along in the dark here!

[oldroydsr4]

Hi,

Sorry the effective duration is measured in degrees.

i have the full deriviation on the equation if this helps.

This equation basically calculates ideal trumpet lengths for a set rpm and assumes the air is being drawn in a 330m/s

cheers

[Demlotcrew]

your sig looks most helpful toby! i can only presume thats not standard m30 intake??

oldroydr4 that would be super mate

Heres one which might interest you also.



Andrew

[liam012]

ok so i have an alpina cam so i assume c is equal to 268, i did this little table to calculate optimum tract length - is it tract diameter that accounts for capicity of the engine because surely you have to allow for that in the equation somewhere?

EDIT: IF ANYONE READS THIS THE NUMBERS ARE COMPLETELY WRONG!!!!

[liam012]

andrew thats not an e30 bay (no sh1t sherlock!!) what is it? looks like a tec1 engine with an m5 setup,
where did you get that from?

[Demlotcrew]

Its a E21 with a early M30 and ITB's



Andrew

[liam012]

oh i thought you were gonna tell me it was same size as m20 cylinder head, you tease!

[liam012]

http://www.rbracing-rsr.com/runnertorquecalc.html

now thats handy, or:
1. / One Formula: David Vizard's Rule for IM Runner Length

The general rule is that you should begin with a runner length of 17.8 cm for a 10,000 rpm peak torque location, from the intake opening to the plenum chamber. You add 4.3 cm to the runner length for every 1000 rpm that you want the peak torque to occur before the 10,000 rpm.

So, for instance, if peak torque should occur at 4,000 rpm the total runner length should be 17.8 cm + (6 x 4.3 cm) = 43.6 cm.

Vizard also suggests that you can calculate the ideal runner diameter by the equation :

SQRT [ (target rpm for peak torque x Displacement x VE)/ 3330 ]

SQRT = square root

VE = Volumetric Efficiency in %

Displacement in Liters


eg.

So if we want peak torque at 5800 rpm at 95% VE in a teg, VE = 0.95


SQRT [ (5800x 1.8 L x 0.95)/3330]

= 1.73 in. or 43.8 mm (1,73 x 25.4 mm/in.) is the ideal runner diameter.


2./ Another Formula to Calculate Runner Length for a Specific Peak Torque RPM: from Steve Magnante at Hot Rod magazine


N x L = 84,000

where N represents the desired engine rpm for peak torque and L is the length in inches from the opening of the runner tube to the valve head

[Dan318-is]

If you want to be really clever liam try and do some research on f1 stuff; they know have variable intake runners for peak torque everywhere and no i dont no how it works!

[oldroydsr4]

Hi liam, your numbers seem way out its for length. I dont think ive explained it very well sorry,so here goes.

It also looks as if ive made a mistake with variable 'C'

I will use a Honda F1 cam for the example so you get the idea.

The maximum speed that air can travel at is the speed of sound. In ambient conditions, this is approximately equal to 330m/s. At approximately maximum valve lift, the speed of air through the inlet tracts is a maximum with the narrowest opening providing increased pressure for the ultimate maximum air speed. If choking was to take place i.e. when the air speed reaches 330m/s, it would be at the narrowest region. The fastest air speed will be assumed at the port mouth at 330m/s
At full lift, a suction pulse is created at the valve opening and travels to the bell mouth at 330m/s. At the bell mouth, it draws in air which travels back to the valve opening at 330m/s. This provides the cylinder with further air for combustion.
This process repeats itself and provides the cylinder with further pulses of air until the valve is closed.
The number of air pulses making it into the cylinder is proportional to the length of the induction tract, the temperature of the air and the engine speed.

The time for the pulse to travel to the bell mouth and back is:

tp = 2L / 330

Where:
L = the length of the induction tract.

The time it takes the crank to rotate the required angle for the pulse to return is:

tc = (C x 60) / (360 x RPM)

Where:
C = the angle of rotation of the crank during time tp,
RPM = the engine speed for the pulse to improve performance.

To determine C:

As can be seen, the inlet valve is still open after BDC (bottom dead centre). In order for air to flow into the cylinder, its pressure must be greater than the rising pressure in the cylinder. It is ideally during this time that the pulse must return.

with the use of the below cam profile 'C'can be found

http://img472.imageshack.us/img472/7799/f1camwt4.png

Angle of full lift = 108 ATDC (after top dead centre)
Angle of valve closing = 266 ATDC
Angle between full lift and BDC = 72

Don't want the pulse to come back straight after BDC because the airs momentum will continue its flow into the cylinder. The pulse is timed so it will return as the momentum of the air has significantly reduced. So assuming the return pulse is at 28 ABDC, this implies that A, the angle between full valve lift (max air speed) and the returning pulse, is:
C = 72 + 28 = 100

note: its approximately 25 degrees, 28 is assumed for easy calculations


For this F1 example

The engine speed that shall be the focus of maximum torque will be 14500RPM.

It is require that the time for the pulse is equal to the time of 100 of crank rotation, therefore:

tp = tc

2L / 330 = (A x 60) / (360 x RPM)

Therefore the length of intake duct required for optimising torque at 14500RPM is:

L = (100 x 60 x 330) / (360 x 14500 x 2)
L = 0.19m =190mm



I hope this helps, Its not 100% accurate but produces a starting length for further testing and development.


There are also further calculations for calculating exhaust manifold primarys and secondarys etc.

[liam012]

i just cam accross that dan but they started ranting about problems with too much surface area and i threw up i was so dizzy.

so it seems there are various equations for determining tract length, and diameter.

what will be difficult will be matching te design to the engiine - that is to say i keep reading that the design of the throttlebody setup should not be thought of on its own but in respect o the engine, the cam, the headers, the redline, the capacity, it must be all thought of as one.

See at the moment i ahve a 2.7 which pulls astonishingly well from about 3800 to redline there might be a small torque surge about 4300 but other than that its a pretty flat feeling torwue curve after 3800. the way i have the car geared i love, 60mph in second, 95 in third and even then you change in to 4th she still wants to go for it, she also cruises at 60mph at about 2200rpm, the 3.46 diff and sport box are just how i like the car, i would not like to design the throttlebodies to move torque up the rev band if anything i would like to keep it the same or even bettert o get there before 3800 would be super but i dont know what measurements would achieve this...

what is the VE of an m20 motor? what exactly is VE? i thought it was volumetric efficiency from my megasquirt tutorials.

[Dan318-is]

VE = volumetric efficiency; mate Ve of an m20 i would love to find that out but i could not in a million years hazard a guess! probably different for a 2.7 though as opposed to a 2.5.

[liam012]

oh good post royds! very much appreciated between that and the googling i am getting it now, but only the basics, designing from my own application still boggles me!
thing is i will only get one crack of the wip fabrication wise as when and if i decide how i want it i will be paying someone to do the fabrication that requires machines as i dont have the tools r experience with metal work.

[Turbo-Brown]

Think you'd need to measure the VE of the M20, I too would love to know what it is.

VE is the amount of air the engine can consume relative to the capacity it displaces so..... if a 2.5 litre M20 could consume 2.5 litres of air every two revolutions of the crank (it only sucks air into each cyl every other rev) it would be said to have a 100% VE.

Most engines will have some way less than a 100% VE, but really well designed ones can get more

The S50B32 gets something like a 102% VE at just over 6200rpm if memory serves, which means that at 6200rpm it's consuming 10118.4litres of air / minute instead of the 9920litres of air/minute it would consume if it had just a 100%VE.

Incidentally, F1 cars aren't allowed variable intake setups anymore. The engines are pretty much just bread and butter pistons, crank, heads etc, just optimised to make loooots of power, but they're probably not much more complex than the humble M20 in principal.

[liam012]

i am guessing it cant or no one has the the money to measure it,

id there an accepted assumption on VE for a m20 2.7?

[e21Jason]

Hi

My mate is running up an m20 on his £250k engine dyno, plus he has a load off flow figures for different valves & port mods from a serdi flow bench. When he completes his research I can post the figures inc VE etc. He has also modeled the engine on ricardo wave sim to work out exhuast lengths and induction lenghts

So far the flow is good for a 2 valve head portign makes minimal differnce on a 885 head, the firiction losses from the the cam journals are high compared to industry bench marks. For more power above 260hp on throttle bodies the m20 needs bigger inlet valves and ports acordign to the ricardo wave sim software.

Jason

http://www.ricardo.co.uk/engineeringser ... ?page=wave