Anyone ported the Au BBM?

[FS5]

Originally Posted by Stav

I did a spare head in the garage.I never full removed the bbm. I didnt know the butterflies dont open fully. I am looking at dumping the manifold for something a bit different.Well alot different lol..

Intake ports matched by gasket to manifold then gasket to head.

i had a play with a bbm but never got round to fitting it.the butterflies don't open all the way up ,they stay on a bit of a lean when fuly open .how much of a topend restriction this is i wouldn't know,but i don't reckon it would be much.
you can get them to open all the way up by simple bending the little metal stopper thing on the front of the bbm where the vacume hose fits it.i'd recomend pulling the top of the bbm off to get it right ,or you could go to far and end up closing them slightly the other way.

[JoesAu]

yeah i see, i will look into that tommorow FS5

[trick_xd]

FS5 You are on the right track

all you have to do is look at it and you will see how they are still restricted .

I was told about 2 years ago after I did a cyl head for a guy he took it to G&D and they chipped and tuned it then even they said the manifold was the restriction in his motor build that it just had .

I Bent the leaver at the front of the bbm to get a extra 6 rwkw .
this is very old news and I would have really thought that a lot of you guys would have all ready done this as all it takes is a small hammer and 10 sec of your time

[blackers10]

any idea exactly how much of a "bend" this requires to give max gain??
would rather not rip off my BBM upper 1/2 just to look for 2 mins lol
cheers for the tip tho trick_xd

[trick_xd]

seems crazy but it only needs about 2 - 3 mm

in doing this you most likely find that the surge when the bbm opens ( atm should be around the 2,500rpm mark ) will be a bit later by about 500 - 700 rpm .
at this I have no real answer but for the time it takes to open the valve in the pod still opens the same but the leaver is bent so it thinks it has started to open when in fact it is not.

I hope you understand that ..... I don't make sense a lot of the time .

[Sox]

Originally Posted by trick_xd

seems crazy but it only needs about 2 - 3 mm

I did this to my XH, and can't say I really noticed much difference. I never tried back to back runs on the dyno though.

in doing this you most likely find that the surge when the bbm opens ( atm should be around the 2,500rpm mark ) will be a bit later by about 500 - 700 rpm .

Nonsense. Firstly, the changeover point stays the same as it is controlled electronically by the ECU. Changing the WOT position of the BBM butterflys will have no effect on when it begins to open.
Secondly, the point at which it does open is 3800RPM, not 2500RPM.

at this I have no real answer but for the time it takes to open the valve in the pod still opens the same but the leaver is bent so it thinks it has started to open when in fact it is not.

Eh? What is it exactly which 'thinks' that something is open when it isn't? And even if something did 'think' it, how could it, when the closed position hasn't changed, only the open position?

I hope you understand that ..... I don't make sense a lot of the time .

You're right, it doesn't make sense.

Rick.

[JoesAu]

yeah im confused now, i see what you mean the valves at wot are only 3/4 open!!, i heard that if you do adjust them you will feel the kick a little later 4000rpm mark, at the moment my car get this real huge rush at 4000rpm anyway so i dont know

[trick_xd]

I don't know how you work out that it opens at 3800rpm
I plant my foot and it starts to pick up at about the 2400 - 2600 mark , maybe it has to do with your cam?

Joe I have stuffed around with a heap of these bbms as you know I was the first to cut 1 up and flip the throttle body as well as 1 of the only people to get a twin throttle body to work right .

Best thing to do is pull your new 1 apart and have a good look at it and have a bit of a play.

[LUXO_8]

the ECU switch point is 3800rpm

[JoesAu]

yeah i know the switch point is 3800rpm, its 4mm to get the butterfies to open 100% just did it then with the split BBM i have so for anyone going to do it there you go, i might try it see how it goes tommorow, i believe it could possibly be a minor restriction at WOT looking at it now....

[JoesAu]

Originally Posted by trick_xd

I don't know how you work out that it opens at 3800rpm
I plant my foot and it starts to pick up at about the 2400 - 2600 mark , maybe it has to do with your cam?

Joe I have stuffed around with a heap of these bbms as you know I was the first to cut 1 up and flip the throttle body as well as 1 of the only people to get a twin throttle body to work right .

Best thing to do is pull your new 1 apart and have a good look at it and have a bit of a play.

i know you have played with heaps of these things, i always thought they opened at 3800rpm maybe i was wrong? looking at the valves when there at 3/4 opened(WOT) i reckon theres a reason for it, if you look i reckon its to angle the air into the each cyclinder DONT YOU THINK?

[Sox]

Originally Posted by trick_xd

I don't know how you work out that it opens at 3800rpm

It's common knowledge. The ECU is factory set to switch the butterfly at 3800rpm. That info can be found in every workshop manual, and a host of other sources.

I plant my foot and it starts to pick up at about the 2400 - 2600 mark

That's obviously the natural power curve of your engine, nothing to do with the butterflies switching.

, maybe it has to do with your cam?

Maybe what has to do with my cam, the manifold changing at 3800rpm? No, that has to do with the ECU.
The cam opens the inlet and exhaust valves.

Rick.

[FS5]

Originally Posted by JoesAu

i know you have played with heaps of these things, i always thought they opened at 3800rpm maybe i was wrong? looking at the valves when there at 3/4 opened(WOT) i reckon theres a reason for it, if you look i reckon its to angle the air into the each cyclinder DONT YOU THINK?

thats what i thought to ,just looking at the way the air has to flow through the bbm and down into the runners.
let us know how it goes mate,if it don't work atleast its easy to put it back the way it was.

[JoesAu]

well had a closer look today, i reckon it could be a restriction at high RPM, as the air circles through the top of the BBM it enters the valve chambers on a down wards angle, im trying to draw a graph of it.

[JoesAu]

well heres the idea of what im talking about, i thought the air entered from the right but it enters from the left, i think the straight butterfly would be better, ive done it to my car will take it for a spin later see if theres any improvements by straightening the butterfly. you never know?

[FS5]

don't forget air is still being sucked through the long runners too.

[EL__Monty]

I have done the samething to open the butterfly valves fully.

I just bent up the metal tab on the BBM actuator with a pair of long nose pliers. Gets about 5-10 degrees further travel so the butterfly valves should be completely open. Noticed a difference when above 3800rpm.

When engine is off the BBM is switched at short runners(butterfly valves are open). When car is started there is vacuum present which holds BBM at long runners with butterfly valves closed. As engine revs past 3800rpm the vacuum is cut by the ecu thus open the butterfly valves.

[Stav]

Ive taken a long hard look at this manifold since.I think straightenning the butterfly will restrict flow.I think the angled butterfly is conducive to flow. I smell inconsistancy here..

[JoesAu]

well i can't say ive noticed any improvements, its a hard one, i had a look of the insides of the Ba bbm today, that manifold is alot better than Au, the valve/chaambers butterflies are all bigger by 3-4mm but its a thirstier motor the ba. There would be gains to be had in your Au thou would have to be punching out some good numbers.. so mayb JMM is right at a certain point it is a restiction, a point im far from just like many others!

[blackers10]

im presuming the BA one bolts on..?? or is it SLIGHTLY different like the exhaust side ??

[LUXO_8]

just give the manifold ports a nice clean up and match-port the lower to the head, and match port the upper to lower if possible...

you'll gain a lot more by doing this and smoothing out the flow than you will mucking about with the butterflies.......... ford didnt just slap them in there and say, "they'll do, the angle doesnt matter"
im sure they would have had a huge amount of testing to get the angles right

[Stav]

I removed the upper intake today. The butterflies are definately at an angle.I also discovered that my throttle body gasket was blocking flow so I recut it. I also proceeded to bend the metal stopper to straighten the butterfly angle into the manifold. I can honestly say that my car feels alot slower. Its not gonna beat its pb after this modification.I have broken my own rules..if its going great..dont touch it.!! I hope I can give it back some punch..

[Stav]

Might have to put a restrictive gasket back in

[InfernoSR]

Originally Posted by Stav

Might have to put a restrictive gasket back in

Now to figure out why that restriction actually helped... unless it was the butterfly positioning... weird either way, as i thought it would have helped throttle responce...

[Stav]

The car would lunge forward like a monster before this mod. I am going to fiddle with it tommorow and see if I can find a happy medium.

[Stav]

Fiddle I did!! The datalogger registered a leanout towards 14 under wot. The bbm tip in did nothing when the butterflies were set to fully open. I came home in the afternoon and found my rubber hose.Found a tiny airleak at the throttle body . The car feels stronger down low but not quite as good as before. I have learnt a valuable lesson here. There is more power to be had with more air going in..(even if it was a leak!!)However the sacrifice in bottom end acceleration is not worth the trouble on a daily driven car. I couldnt even overtake a slk 230 mercedestoday.I normally eat them for breakfast..Loss of low down power is too big a compromise that I won't be sacrificing again if I can get the wagon back to its line munching torque.

I tuned for the air leak and can honestly say that the car gained more power at the expense of the low to midrange punch which dominates street overtaking acceleration.

[Pekkerwood]

There must be something in the butterflies angle as the BA has bigger butterflies but still runs the angle

[Tray]

Originally Posted by Pekkerwood

There must be something in the butterflies angle as the BA has bigger butterflies but still runs the angle

Closed position is at 78* BA have 42mm butterflies, Pre BA 38mm. Runners are identical as for volume. air will travel the shortest path.. South! I've rigged up my machine to bore these manifolds out to 42mm (pm if interested).. Porting the runners will be pointless unless your running 180rwkw plus