Plenum Spacer calculations

[boucherie]

Further to robs plenum spacer ive been doing some calculations to see if it will be worth looking at having some made up.

The internal circumferance of the plenum (around the gasket) is 89cm which equates to a square of 22.25cm

therefore the surface area would be 22.25 x 22.25 = 495.0625cm2

by making up a 1" spacer the volume it will hold then becomes

495.0625 x 2.54 = 1257.49cm3 or 1.257litres

The top of the plenum chamber holds 2.5 litres so therefore a 1" spacer will increase the volume of the plenum chamber by about 50% by my calculations.

Can someone dbl check this and confirm/deny if thats correct or not.

If it is correct then who wants to get them made up!

 

[low612]

Here in the states it was measured 15% or 20% increase involume i dont remember exactly but its one of the two .

 

[boucherie]

if you took into account the rest of the inlet manifold then it would naturally reduce the 50% figure so something around 20% for the whole inlet manifold would sound about right

 

[stugtir300]

to increase the capacity of the plenum would it not be easier to have a custom one made to desired spec,would it cost alot?

 

[CruiseGTi-R]

Do you need a bigger plenum?

Doesn't having a bigger plenum give a pressure drop?

The turbo pressure has to pressurize the whole engine including pipe run, FMIC and plenum, won't you just get a tiny bit more lag and less responsiveness (a bit like the moans people have with extra lag of running bigger fmic??)

 

[Fusion Ed]

no, the extra space is like that of one engine rotation, you wouldn't notice the difference.

 

[CruiseGTi-R]

But you notice the extra lag with FMIC?

What's the extra volume for anyway? Wouldn't the best plenum be one which splits the FMIC piping into 4 equal pipes which feeds each throttle body (bit like an exhaust manifold in reverse)?

I guess I'm not really sure how a plenum works and why its used?

 

[Odin]

My understanding of the spacer plate is that it is supposed to aid low end torque, But I'll have to wait and see just what sort of results I get.



Rob

 

[Dooie Pop Pop]

My understanding of the spacer plate is that it is supposed to aid low end torque, But I'll have to wait and see just what sort of results I get.



Rob

same effect as making the runners longer then8) why dont you just supercharge the thing and be done with it:lol:

 

[nitrosgti-r]

wont it also keep the pleneum chamber heat down if its away from the block?

 

[antgtir]

Not appreciably, im sure someone out there could calculated that the temp has been reduced by 0.00000000000001 degree lol, i would hazard a guess that the temp wuld be exactly the same.

Will be interesting to see what results Rob has from this.

Ant.

 

[youngsyp]

wont it also keep the pleneum chamber heat down if its away from the block?

The spacer is also aluminium which, is a very good conductor of heat. So, it's unlikely you'll see any change in temperature readings at the plenum end.
If it we're plastic, it would be a different story though !