M20 B3x Naturally Aspirated Stroker build past, present and future

[digger]

I'd be really tempted to run an acrylic cover over that airbox instead of the CF. Show off those trumpets..

thought about it but the lid is not flat so it would hard to mould acrylic?

[nando]

Thermoform it. Its pretty easy. I made a new cover for my custom instrument cluster out of acrylic.

[digger]

Thermoform it. Its pretty easy. I made a new cover for my custom instrument cluster out of acrylic.

im not sure how id mould a piece without damaging my existing lid given it needs to be what about 275F ? i would need to use my lid as a mould and need something to protect it

[nando]

you'd make a form out of something else (wood, clay, another sheet of acrylic, etc). it depends on the exact type of acrylic, but it's more like 300-350f. the smoother the mold of course the clearer your product ends up. I actually used another piece of acrylic (stock lens) to make my mold, it lasted about 4 times before it melted.



your shape is a lot simpler so I'd think it's definitely doable. necessary? no, but then neither is an ITB'd, 3.1 liter M20 that puts most S50s to shame. :p

[bmwandhonda]

Um, just stumbled onto this thread now. Absolutely awesome amount of work going on here, some crazy amounts of knowledge on show that is for sure!!

Keen for more progress and pictures.

[LJ851]

You sure you would want a clear lid with those stacks like that ?

[The Dark Side of Will]

curved adapters 3D printed in ABS plastic and clamps from 48mm trumpets (e21 JPS aka RHD) so that i can use a thicker wall without crushing them. they are to get everything inside the airbox and clear the hood without using a excessively short runner and provide additional clearance to the booster and not shroud the trumpet. you can rotate the whole trumpet to point them forwards slightly to but you need to rotate them all because the centre spacing is about 90-92mm and diameter is 80mm of the bell mouth



trial assembly, trumpet length is 30mm shortened to have same centreline runner length as previous. i chose 30mm so that i can shorten them a further 30mm if needed more fasts. the new engine will require about 25mm shorter length according to calculations and simulations. the dyno will decide so i favour the longer length in the interim



this is why they are needed. this is runner 2 (no curved adapter), runner 1 is worse and runners are angle downwards. runner 6 is angle upwards but less of an angle this is to clear the booster by additional amount



runner 1 & 2 are angle down to give about 30mm less height, runner 3 is about 20mm but is not 100% needed. this was done to centre the trumpet in the box height wise



a view inside from the inlet



did some conceptual CFD to deliberately look at shrouding (distance between the trumpet and wall opposite opening) and some basic distribution to convince my self it wont be a disaster. i modelled the trumpets longer so they get quite close to the opposite wall to exaggerated the issue



quite a bit of flow comes from around the sides rather than from straight above







alot of flow comes from bellow the bellmouth



open trumpet flowed 0.152kg/s by itself. when flowed with box it is 0.150kg/s runner 6 and 0.152kg/s runner 1 so not much difference to open trumpet provide the K&N isnt restrictive. i have room for larger filter so will search the K&N site for suitable one

Interesting analysis... but don't forget that you'll never see two runners pulling max flow at the same time... not sure if this will affect your model. I read on and saw that you mentioned that later...

Also, even if a runner can flow 150 g/sec, the filter doesn't have to flow 900 g/sec, more like 300 g/sec as each runner's duty cycle is only ~30%.

[digger]

Interesting analysis... but don't forget that you'll never see two runners pulling max flow at the same time... not sure if this will affect your model. I read on and saw that you mentioned that later...

Also, even if a runner can flow 150 g/sec, the filter doesn't have to flow 900 g/sec, more like 300 g/sec as each runner's duty cycle is only ~30%.

ive not seen anything on the K&N site for a guide as to the rating in terms of hp or CFM. the thing i dont like about my filter is because the ID is 4" and base OD is like 5.5" there isnt enough room for them to put an internal radius to transition from the element into the flange so its like a sharp edge. i have a pretty old 3" filter with 6" diameter which has a nice internal radius.

my current cone has unwrapped area about the same size as stock panel but i was using the bigger panel used on the S14.

im interested to know about how much of the filter area is actually used on a cone filter

[LJ851]

the thing i dont like about my filter is because the ID is 4" and base OD is like 5.5" there isnt enough room for them to put an internal radius to transition from the element into the flange so its like a sharp edge.

The filters i use on the throttle bodies on my Ducati are like this. I took a 3/4 inch ball carbide cutter and made the best radius i could with it, prob only a 1/4 inch radius but a hell of a lot better than a square edge !

[digger]

The filters i use on the throttle bodies on my Ducati are like this. I took a 3/4 inch ball carbide cutter and made the best radius i could with it, prob only a 1/4 inch radius but a hell of a lot better than a square edge !

fingers crossed my new filter is better its an extra inch diameter so should be able to a 1/2" radius no problem which is plenty considering it is 4" and hence the airflow velocity is lower than would be the case on a 3". it has 44% more surface area (projected area not considering the pleat length etc)

[digger]

thought people might be interested in a test i did last year with the socks and older ITB setup. i oiled the socks using the stuff you get for dirtbikes. they restrict flow a little ;)



cleaning them with kero and running them dry improved alot and it made 130kw ish which was still down about 12 kw from the equivalent unfiltered setup so individual socks are not great.

ideally you want a common large filter that all runners use not individual socks

[bradnic]

SUB'D.. still haven't installed my dbilas yet.

[digger]

SUB'D.. still haven't installed my dbilas yet.

please sell it and use something better in that case.


My new K&N Arrived. alot better featured and sized but dont know if this will amount to anything probably small change at best.

-44% more area (it is longer and a bigger diameter)
-internal radii of about 8mm rather than sharp edge
-flange features a step so that the sharp leading edge of the airbox cant disturb the flow

[ForcedFirebird]

please sell it and use something better in that case.

I actually LOL'd

[bradnic]

yeah me too. digger knows what he's talking about. not ready to give up on it yet though - SC + ITB at some point.