Head porting for FI

[TheTacoMan]

Looking for some pointers on port matching and doing some light port work on an m20 with FI. Any articles worth looking at or worth advice?

[IronFreak]

Looking for some pointers on port matching and doing some light port work on an m20 with FI. Any articles worth looking at or worth advice?

Get forcedfirebird in here.

[pantelones]

Looking for some pointers on port matching and doing some light port work on an m20 with FI. Any articles worth looking at or worth advice?

http://hotrodenginetech.com/pipemax-...-head-porting/

Not simple porting, but the principles and knowledge are the same. Thank digger for that link!



I gasket matched my intake, and I think it was worth the effort. I didn't take a photo of the gasket on the head, but it was nearly perfect; the intake on the other hand...




IMG_3985 by Los Pantelones!, on Flickr



IMG_3989 by Los Pantelones!, on Flickr



IMG_3988 by Los Pantelones!, on Flickr




IMG_3991 by Los Pantelones!, on Flickr



As for the head itself, try not to remove any material. Just clean up the casting and measure the chamber cc's. If they are even or very close don't worry about it. Bigger is not always better, and the 885 actually needs material added to have a more efficient port design. Also remember, do not polish anything, contrary to logic you will have a better flowing head with a textured surface. And please use a turbo cam profile; unless you can verify that your intake:exhaust pressure differential is less than 1:1 in favor of the intake side, you are losing a lot of power...

[Q5Quint]

I like you.

The m20 head flows pretty well from what I understand, but some mild work can still yield some ok but not great flow increase results. Bigger valve sizes and lift are limited due to cyl clearance but +1 works, and apparently one of the bigger restrictions is the intake manifold itself, not the head. If you go over 2.8 liters the stock intake manifold may be holding you back more than the head itself, hence why many build custom and itb units. This would apply to turbo flows as well and even more from the exhaust/header side.

"this head was done to suit class rules that dictate stock 325i camshaft"


Also read through this whole thread: http://www.e30tech.com/forum/showthread.php?t=75938

and (one of) the money shot:

I'm now up at 182-183 cfm @ 14 mm lift with a pretty calm port and nice average flow speeds (260-270 fps). The flow is 5-10 cfm lower at high lifts with the intake mounted and the reason is simple, it's too small. I have a few options to improve things from here and I haven't decided which way to go yet. (Mickes flow in yellow)

The flow achieved with Micke's head was with 43 mm (+1 mm) valves. You can see how my port flows better overall but slightly stalls up top, not much happens after 11 mm lift. If I raise the port or somehow make a better inner radius I could probably get up top 190 cfm but it's just not feasable right now.

Old:


vs new (notice the eleptical cutout so the +2mm valve actually fits in the cyl head):

Apparently that work was based on a Hartge 2.3l head.

TL;DR Gasket match your intake manifold. Clean up but dont remove much or any material from the cyl head intake/exhaust and add +1 valves with a turbo cam (not lots of overlap like NA cams). Any more than that and you probably want the flow bench. You are not using a log turbo manifold, are you?

[digger]

short side radius is more important than if NA, the denser the air the less it likes making turns.

[e30m3s54turbo]

Dinan use to port their intakes on stroker motors like m20 and m30 in the late 80's and early 90's.

[digger]

you cant do much to the intake manifold there are lots of bad tight bends and poor casting details that are not even visible unless you have cut one up into lots of tiny little bits.....let alone accessible with a grinder. simply grinding a little bit of the straight portion at the very end of the manifold is going to very little

best bet is to get one of the RHD CNC manifolds some of the RHD CNC extensions and fab a plenum with single TB. get the runners as long as you can while still fitting a nice shaped and volumed plenum and you are good to go. the length is less critical on a FI engine compared to NA but the same physics applies

[TheTacoMan]

I have a tube style manifold, I ended up using the gaskets and port matched the intake manifold. I decided I'm not going to do to much port work other than port matching the exhaust and intake manifolds. Although the next head I build will be ported a lot more. I did use a dual pattern cam with hd rockers.
Lots of good info here, I may have to go with a different intake manifold down the line.

[Overlord475]

best bet is to get one of the RHD CNC manifolds some of the RHD CNC extensions and fab a plenum with single TB. get the runners as long as you can while still fitting a nice shaped and volumed plenum and you are good to go. the length is less critical on a FI engine compared to NA but the same physics applies

RHD Engineering also makes an ITB kit for M20:

http://www.racehead.com.au/?wpsc-product=bmw-m20-itb-throttle-body-kit-40mm-plus-e30-linkage-kit

[dustyperez]

ROLLER ROCKERS!!!!!!!!:bow:

[digger]

RHD Engineering also makes an ITB kit for M20:

http://www.racehead.com.au/?wpsc-product=bmw-m20-itb-throttle-body-kit-40mm-plus-e30-linkage-kit

yeah see my sig

[TheTacoMan]

Ended up porting matching bother exhaust and intake manifolds, I have no access to dyno to confirm any gains however.