Adam's Homemade Plenum chamber thread

[adamnreeves]

I think it looks taller because it is on a 8-9mm thick plinth.

The front is 70mm + curve and the middle sections are 85mm + curve.
Which is lower than the standard item I believe.

The circle you can see on the front is 75mm in diameter.
As you can see I can only make maximum of 10mm shorter. I might do this but I do want the thottle intake to cause too much air turblulance around the trumpets themselves, the reason for marking where the inake would be and the reason why it is so close to the top of the plenum, I shall make some calculations to see if I can reduce the height, like I said ideally the front height would be 57mm.

Is that not too tall?

[chodjinn]

Hey Adam, interesting thread, I'll follow this closely! Would you consider making more than one . . ??!?

[adamnreeves]

I am sure I could be tempted once I have a mould fabricated that is!
Yes, keeping watching here.

Hey Adam, interesting thread, I'll follow this closely! Would you consider making more than one . . ??!?

[pitsnow]

I think it looks taller because it is on a 8-9mm thick plinth.

The front is 70mm + curve and the middle sections are 85mm + curve.
Which is lower than the standard item I believe.

The circle you can see on the front is 75mm in diameter.
As you can see I can only make maximum of 10mm shorter. I might do this but I do want the thottle intake to cause too much air turblulance around the trumpets themselves, the reason for marking where the inake would be and the reason why it is so close to the top of the plenum, I shall make some calculations to see if I can reduce the height, like I said ideally the front height would be 57mm.

I think your 57mm height would work well.
Have you planned to direct the air flow towards the middle?
If you have a closer look at the Westfield ACT plenum, the air flow from the throttle body is at an angle to the plenum chamber, directing the air towards the plenum roof.
The ACT plenum also has some "guides" on the side wall to support the air flow direction.
I assume this is the help with better air flow distribution inside the plenum.
The ACT plenum shape is lower but wider than your design.

[adamnreeves]

Didn't notice the ACT was wider that the plenum base other than the flanges, maybe this is why they feel they need to direct the air then!

I am planning on having the throttle intake to point upward towards the upper centre of the plenum which is also some 15mm higher than the lowest point.

I think it looks taller because it is on a 8-9mm thick plinth.

The front is 70mm + curve and the middle sections are 85mm + curve.
Which is lower than the standard item I believe.

The circle you can see on the front is 75mm in diameter.
As you can see I can only make maximum of 10mm shorter. I might do this but I do want the thottle intake to cause too much air turblulance around the trumpets themselves, the reason for marking where the inake would be and the reason why it is so close to the top of the plenum, I shall make some calculations to see if I can reduce the height, like I said ideally the front height would be 57mm.

I think your 57mm height would work well.
Have you planned to direct the air flow towards the middle?
If you have a closer look at the Westfield ACT plenum, the air flow from the throttle body is at an angle to the plenum chamber, directing the air towards the plenum roof.
The ACT plenum also has some "guides" on the side wall to support the air flow direction.
I assume this is the help with better air flow distribution inside the plenum.
The ACT plenum shape is lower but wider than your design.

[chodjinn]

Adam are you building this plenum for forced induction or naturally aspirated? Would it cope with forced induction pressures? Would certainly be interesting to find out!

[katanaman]

The directed/split air is because you are using a front throttle body. Without the split air intake you run the risk of poor distribution to the back pots. Pointing the air up wont do anything as the front pots will soon drag it down. I would suggest that since your trying to make this better than what is already available you look into splitting the air as Westfield and ACT have done. I would recommend it even more since your trying to get large power outputs as well or you could end up with melted rear pistons. The original doesn't need this as its on the side and has a large taper which feeds practically the whole side.

[adamnreeves]

I am going to taper my intake as much as I can which I shall do up on the pattern I am building. Will also direct towrd centre. Does the OEM intake on the side mean that one bank on the Vee is richer than the other? I presume the effect is less than lengthways where there are 4 banks of sucking trumpets! Also my intake will be on the rear of the engine so cylinders 7,8 are closest to the intake but I guess this means that cylinders 1,2 will suffer from the effect you described. I shall give a splitter some thought but will mean a kind of dolphin head shaped chamber. All valid considerations which at this stage is good. Appreciating all the feedback here.

The directed/split air is because you are using a front throttle body. Without the split air intake you run the risk of poor distribution to the back pots. Pointing the air up wont do anything as the front pots will soon drag it down. I would suggest that since your trying to make this better than what is already available you look into splitting the air as Westfield and ACT have done. I would recommend it even more since your trying to get large power outputs as well or you could end up with melted rear pistons. The original doesn't need this as its on the side and has a large taper which feeds practically the whole side.

[adamnreeves]

Naturally aspirated at the moment!

Adam are you building this plenum for forced induction or naturally aspirated? Would it cope with forced induction pressures? Would certainly be interesting to find out!

[katanaman]

The standard setup in theory only has one bank to go over so there is a lot less starvation. In theory the Siamese plenum would be the ultimate with both sides being fed the same. In reality is seems to make little odds over a larger or bored out throttle and the factory kit seems to work pretty will.

Since your open to ideas the only other thing that seems not quite right to me is your domed top. This could be completely wrong but it looks like if you have any pulses hitting the roof which is likely, they are going to get reflected at the angle and not straight back. It also means that one side of the trumpet is further away from the top than the other, maybe causing some odd results. I would have thought a flat top would be better. The standard and act have a very slight curve to the top but nothing like yours and is more at the edges which is probably more for aesthetics. To you another advantage would be lowering the hight for your install. Of course you could raise the sided as well if you wanted max distance from trumpet to top if you have the room to spare.

Like I said its all just a theory but makes sense to me. Does it make sense to anybody else?

[adamnreeves]

The curve in the top was an attempt to have effectively the same distance between the centre of each trumpet to the plenum top, maybe I took this too literally? I see what you mean about the curve and that ideally a flat top would prove better, I guess its a balance act and somewhere between would be best. As for the height I want to get as close to 57mm as possible but like I said before would need to be heigher to accomodate the throttle intake bore and now a splitter.

I was having wild ideas last night about a twin throttle version with intakes at either end but I suppose the linkages would be a nightmare but could be done but I am thinking that intakes opposite one another would cause major air turbulence! I do not think the front intake would fit in the room available anyway.

The standard setup in theory only has one bank to go over so there is a lot less starvation. In theory the Siamese plenum would be the ultimate with both sides being fed the same. In reality is seems to make little odds over a larger or bored out throttle and the factory kit seems to work pretty will.

Since your open to ideas the only other thing that seems not quite right to me is your domed top. This could be completely wrong but it looks like if you have any pulses hitting the roof which is likely, they are going to get reflected at the angle and not straight back. It also means that one side of the trumpet is further away from the top than the other, maybe causing some odd results. I would have thought a flat top would be better. The standard and act have a very slight curve to the top but nothing like yours and is more at the edges which is probably more for aesthetics. To you another advantage would be lowering the hight for your install. Of course you could raise the sided as well if you wanted max distance from trumpet to top if you have the room to spare.

Like I said its all just a theory but makes sense to me. Does it make sense to anybody else?

[adamnreeves]

I had looked at a couple of pictures of the ACT plenum chamber from the inside and cannot see any guides or splitters. Can anyone shed light on this.

I have done a few skeches and if the splitter is required I cannot see how I come up with a spitter that gives consistent air flow and ideal trumpet to plenum top gap ratio. The best I can get on paper using a box design is 55mm under the splitter and 91 not under the splitter and that gives me wildly different ratios. Also with the splitter across the buttefly of the thottle, I am assuming that airflow across the top of the butterfly must move faster than air below it


I think I am going to think about how I could incorporate a twin throttle arrangement in a westfield!

[Eliot]

Picture of the OEM westfield seight splitter:
http://www.seight.net/images/induct1.jpg
from
from http://www.seight.net/http://www.seight ... uction.htm
i cant find it now, but he did a dyno run after removing the splitter and saw a slight improvement.
For my mates seight, i removed the splitter straight away as it was only slightly above the front trumpets and just seemed plain nasty. I'm not saying a splitter is bad, just the westfield implementation was poor.

[adamnreeves]

Yep not surprised the splitter above the first four trumpets makes a gap of 55mm whilst the front ost trumpets have a gap of 90mm, not good in my limited knowledge of this subject.

Picture of the OEM westfield seight splitter:
http://www.seight.net/images/induct1.jpg
from
from http://www.seight.net/http://www.seight ... uction.htm
i cant find it now, but he did a dyno run after removing the splitter and saw a slight improvement.
For my mates seight, i removed the splitter straight away as it was only slightly above the front trumpets and just seemed plain nasty. I'm not saying a splitter is bad, just the westfield implementation was poor.

[pitsnow]

I had looked at a couple of pictures of the ACT plenum chamber from the inside and cannot see any guides or splitters. Can anyone shed light on this.

It is not easy to see but the guide on the ACT Westfield plenum is the way it is shaped more than having deflector plates inside.
This picture may show it to a certain extend. Look at the back were the plenum is shaped outwards towards the back (which is the front on the photo)


If you could get your hands on one it would be a lot easier to see as the photo does not show it well.
As for a twin throttle in your Westy, front and back, you are having a laugh surly?