Performance plenum spacer question

[JMF894]

Has anyone any experience of using a plenum spacer on their wedge, particularly the larger engined varients?

I've read that they can give torque benefits for the larger cc cars and i was wondering if they need to be used in conjunction with anything else i.e different trumpets, in order to be worthwhile.

In addition, where are they available and for how much?

Cheers Jimbo

[JR]

IIRC the main benefit is in delaying heat soak.

Don't recall torque differences but there is a trade off in throttle response and power. I think that it's the taller plenum has more power and the lower has better throttle response but my memory may be playing tricks and it's the other way around.

Plenty to think about for trumpets as well: varying lengths and materials. Tim at ACT ofr CF.

Matt and Wedg1e make them in different thicknesses:

http://www.pistonheads.com/gassing/profile.asp?mem...

http://www.pistonheads.com/gassing/profile.asp?mem...

[wooly350i]

Wedg1e did mine for me,speak to him. Heat into plenum is delayed/reduced. Need to get it back on road to reap full benefits.
John.

[jmorgan]

Mine felt different but then it was hardly a conclusive test. You can place your hand on the plenum easily after a run. I did use my temp dohicky to see what the temp was but forget now, quite a difference I seem to remember. My trumpets were already shortened.

[combine]

Did this 2 years ago , keeps the chamber cooler for air into trumpets , have shortened flared trumpets too and other stuff , go for it !

[rev-erend]

I think you are all talking about different things.

Matt and others have made / fitted plenium insulators - about 1mm thing and stops the heat soak .. so in therory the power you have in there all the time .. and not just when the plenum is cool.

There is another product around that helps to increase the plenum volume - I've not seem any conclusive proof that it works as claimed and as others have pointed out - having an increased volume the other side of thethrottle plate could slow the all important slow speed air and harm driveability.

I would keep my hard earned in my pocket with the latter product.

[wooly350i]

I think we're all talking the same,mine is 6mm thick and insulates between inlet maniflod and trumpet base thus reduces heat soak into plenum from block,i think J Morgan went for a 10 or 12 mm of the same. Shortened trumpets etc etc are an added bonus but depends how deep ya pockets want to stretch!

[rev-erend]

Are we ?

Plenum spacer in orange and insulator in beige - from SC power.

[JMF894]

Always good to kickstart a discussion.

Keep it coming chaps.

Reverend your input in particular is very interesting. I for one didn't realise there was a spacer AND an insulator available.

I need to know what people have got and what differenc etc has made please...........

Jimbo

[JR]

rev-erend said:

Plenum spacer in orange and insulator in beige - from SC power.

That's just playing with names. What if the beige one in your diagram were 10 or 12mm thick?

[Wedg1e]

JR said:

That's just playing with names. What if the beige one in your diagram were 10 or 12mm thick?

Mine is 10mm thick; I call it a plenum insulator

I offer insulators in 6mm or 10mm (could do thinner or thicker but the bonnet needs to close!), all hand-made to order. The majority have been for the standard inlet setup but Iain Jones (Chassis33) had one cut to suit his Thor manifold. Wooly's has big-bore trumpets and some of the bore centres had been moved slightly, just for a laugh
Most people who offer them have access to a CNC machine and once the prototype design is done in AutoCAD or similar and confirmed with a trial cut, it takes seconds to load up and cut out the subsequent ones... but they don't charge any less once the initial work is done
There is quite a bit of work involved in producing them by hand which is the same every time. I haven't tried the top spacer but the principle would be the same, just more fiddly - there'd be a lot of material wastage unless by chance there's enough in the centre from which to make an insulator as well.
My car has the trumpet base milled down by 10mm so the overall plenum height (and thus the inlet tract length) is the same as standard.
As Jeff says, you can put your hand flat on the plenum top after a spirited drive and keep it there, which you certainly can't do without the insulator. I'm a bit of a wuss when it comes to touching hot things so probably well under 60 degrees, maybe even <50.

[JR]

Wedg1e said:

could do ... thicker but the bonnet needs to close!

or a shaker bonnet!

[Chimpafrolic]

rev-erend said:

Are we ?

Plenum spacer in orange and insulator in beige - from SC power.

Hi Wedgies I have both the plenum spacer (shown in orange) and the insulator gasket (shown in beige) in the CAD image above.

Both items (& the trumpet bell mouth rings) came as a kit from SC-Power.

In my case the spacer made a big difference to drivability between 1800 - 2200rpm.

The 20mm spacer works by bringing the plenum roof away from the mouths of the velocity stacks (trumpets); this reduces induction pulse interference between the open ends of each inlet tract.

I also dropped my trumpets by 8mm, so my trumpet mouths now have 28mm more clearance from the plenum roof over standard.

The spacer also has the effect of increasing the volume of the plenum by half a litre.

The insulator gasket definitely works & to my mind anything that helps reduce the temperature of the inducted air has to be a good thing, as we all know from basic school boy physics colder air has a greater volume.

I doubt the spacer made much difference to the engine power output but it did transform the low speed drivability.

Although linked it's important to understand that shortening your velocity tacks (trumpets) is a different principle to the spacer.

What TVR typically gave 4.0 & 4.5 litre Chimps on the induction side (not sure about Wedges) was pure Range Rover.

The trumpets, plenum, throttle butterfly, inlet manifold and ultimately the inlet tract lengths are all exactly as they would be on a Range Rover & all carefully designed with that heavy 4x4 vehicle in mind.

The basic rules of inlet tract length are:

1) Increasing inlet tract length brings peak torque in lower down the rev range (ideal for off-road & towing duties)

2) Shortening inlet tract length pushes peak torque further up the rev range (better suited to a light weight sports car application)

As I do not tow a horse box or drive up muddy mountains in my Chimp I figured I could easily shorten my inlet tract length by a small margin from the standard Range Rover set up.

The combination of the plenum spacer & shortening my trumpets worked really well for me

[lestershaw]

i have this as a winter project
heat sandwich and plenum spacer and flared shortened trumpets and ported heads
along with 72" plenum which i am hoping will will work well with the extra space the spacer and shortened trumpets, also larger bore ( bosch ) afm and smooth bore elbow.
i am hoping for another 13 bhp to take me above 300 bhp on my 500 chim, if any of this is at the expense of drivabilty it will all come straight back off, as i have no shunting and 287 bhp and it goes really well!

[Oz2]

I am interested in insulating the Plenum even more so because of the Australian climate combined with the suercharger heating uP the already hot air even more. you Put your hand on my Plenum at your own risk
so my question is all the info in this thread would it still stand with my engine and set uP, mine is also a 350cc so does this change the formular.....

Cheers

Adam

[adam quantrill]

I considered it briefly but the air coming into the plenum can be hotter than 100C with the Sprintex blowing.

So this means that the plenum actually conducts heat _away_ from the air and towards the engine block in our case, Adam. So it's probably a waste of money.

Added to that the spacer will have to put up with 6psi without letting go.

[JR]

adam quantrill said:

I considered it briefly but the air coming into the plenum can be hotter than 100C with the Sprintex blowing.

But the cylinder head is trying to warm the plenum up from below. How hot does the cyl head get? 400 deg inside temp?

[Oz2]

adam quantrill said:

I considered it briefly but the air coming into the plenum can be hotter than 100C with the Sprintex blowing.

So this means that the plenum actually conducts heat _away_ from the air and towards the engine block in our case, Adam. So it's probably a waste of money.

Added to that the spacer will have to put up with 6psi without letting go.

Yes very good point I had`nt thought of it that way round, plenum heating the engine

[Oz2]

Added to that the spacer will have to put up with 6psi without letting go.
[/quote]


it would have to be able to stand up to 6psi, would`nt it

[JR]

Oz2 said:

it would have to be able to stand up to 6psi, would`nt it

Whereas gaskets normally have to withstand hundreds of psi...

A supercharger is even more reason to fit a plenum insulator.