A Friday afternoon job...
Discussion
Look, if I'm going to have an extra day off every week, I may as well do something useful with it!
So, I clamped a slab of high-density plastic onto the horizontal mill...
[pic]http://photos.fotango.com/p/eba00272483f00000091.jpg[/pic]
and cut it into three pieces. Cunningly, I'd bought a piece that was big enough to do just that... :D
Next, I clamped it to the table of the vertical mill with an offcut of MDF as a packing piece, and applied a hole saw (carefully) through the trumpet base from my project injection system:
[pic]http://photos.fotango.com/p/eba00272483f00000092.jpg[/pic]
The trumpet base is dowelled to the inlet manifold to provide a precise location so that the ports in both line up, so I thought it only right that I should do the same. Once I'd drilled the dowel holes I tried the insulator (for that is its nomenclature) on the inlet manifold to make sure it was accurate...
[pic]http://photos.fotango.com/p/eba00272483f00000093.jpg[/pic]
... which it was, luckily. A quick whizz round with the jigsaw and a polish up with an orbital sander and hey presto:
[pic]http://photos.fotango.com/p/eba00272483f00000094.jpg[/pic]
Another step closer to injected Nirvana (which is not to imply that the band of the same name are a bunch of junkies, though they may well be...)
[pic]http://photos.fotango.com/p/eba00272483f00000095.jpg[/pic]
Amazingly enough, I have enough spare material to make two more... :D
So, I clamped a slab of high-density plastic onto the horizontal mill...
[pic]http://photos.fotango.com/p/eba00272483f00000091.jpg[/pic]
and cut it into three pieces. Cunningly, I'd bought a piece that was big enough to do just that... :D
Next, I clamped it to the table of the vertical mill with an offcut of MDF as a packing piece, and applied a hole saw (carefully) through the trumpet base from my project injection system:
[pic]http://photos.fotango.com/p/eba00272483f00000092.jpg[/pic]
The trumpet base is dowelled to the inlet manifold to provide a precise location so that the ports in both line up, so I thought it only right that I should do the same. Once I'd drilled the dowel holes I tried the insulator (for that is its nomenclature) on the inlet manifold to make sure it was accurate...
[pic]http://photos.fotango.com/p/eba00272483f00000093.jpg[/pic]
... which it was, luckily. A quick whizz round with the jigsaw and a polish up with an orbital sander and hey presto:
[pic]http://photos.fotango.com/p/eba00272483f00000094.jpg[/pic]
Another step closer to injected Nirvana (which is not to imply that the band of the same name are a bunch of junkies, though they may well be...)
[pic]http://photos.fotango.com/p/eba00272483f00000095.jpg[/pic]
Amazingly enough, I have enough spare material to make two more... :D
Yep, it's an insulator to try to lower the temperature of the inlet plumbing (plenum, trumpets etc.).
There seem to be two methods that are commonly employed: the first is to fit an insulator between the trumpet base and the plenum (JMorgan has one like this EDIT: No he doesn't, see further down!) - this has an added benefit of increasing plenum volume and also raises the plenum roof height above the central trumpets, considered a good plan with large-bore trumpets.
The second is, as here, to fit a plate between the inlet manifold and the trumpet base, which in theory means that more metalwork stays cooler (less heat soak into the intake air). The racing Griffith at Cadwell a couple of weeks back had one like this.
The first method is easier to machine but needs more material to start with; the second is more compact and MAYBE more efficient.
About a squillion years ago (probably on Egroups) the idea was mooted of putting insulators between the inlet manifold and the cylinder heads (Peter Humphreys plan IIRC) but this is even more complex as you'd have to skim the manifold to keep all the ports in line.
I plan to remove an equivalent amount of alloy from the bottom of the trumpet base so that the port runners stay the correct length once the insulator is fitted... maybe next Friday!
I noticed that the racing Griff hadn't had this mod so it may not be necessary but what the hell; I have a few spares...
>> Edited by wedg1e on Wednesday 10th August 00:51
There seem to be two methods that are commonly employed: the first is to fit an insulator between the trumpet base and the plenum (JMorgan has one like this EDIT: No he doesn't, see further down!) - this has an added benefit of increasing plenum volume and also raises the plenum roof height above the central trumpets, considered a good plan with large-bore trumpets.
The second is, as here, to fit a plate between the inlet manifold and the trumpet base, which in theory means that more metalwork stays cooler (less heat soak into the intake air). The racing Griffith at Cadwell a couple of weeks back had one like this.
The first method is easier to machine but needs more material to start with; the second is more compact and MAYBE more efficient.
About a squillion years ago (probably on Egroups) the idea was mooted of putting insulators between the inlet manifold and the cylinder heads (Peter Humphreys plan IIRC) but this is even more complex as you'd have to skim the manifold to keep all the ports in line.
I plan to remove an equivalent amount of alloy from the bottom of the trumpet base so that the port runners stay the correct length once the insulator is fitted... maybe next Friday!
I noticed that the racing Griff hadn't had this mod so it may not be necessary but what the hell; I have a few spares... >> Edited by wedg1e on Wednesday 10th August 00:51
I seem to remember someone else (DJE)
www.djev8.com/
doing this (thermal insulating block £38)
but the problem is height - plenum rubbing on the bonnet..
Great if it does not - obvious advantage is no heat soak from the engine to the plenum
Nice job thought..
www.djev8.com/
doing this (thermal insulating block £38)
but the problem is height - plenum rubbing on the bonnet..
Great if it does not - obvious advantage is no heat soak from the engine to the plenum
Nice job thought..
Ian have you thought about making an insulating spacer to go between the plenum top and the trumpet base, instead? As well as the insulating effect, it gives you more clearance over the trumpets - my feeling is this is one of the major reasons the aftermarket plenums work so well.
Edit: you got there before me! The blower manifold has been machined a little short and I use an extra gasket between it and the heads, now that I've got the decompression plates on it needs a thicker gasket. Still gets bleeding hot, but it's got to help I reckon.
Oh and edited again: if you're doing it again, I recon you can get away with a much thinner insulating plate, I don't think you want to lengthen the intake any more than you have to?
>> Edited by GreenV8S on Friday 5th August 22:45
Edit: you got there before me! The blower manifold has been machined a little short and I use an extra gasket between it and the heads, now that I've got the decompression plates on it needs a thicker gasket. Still gets bleeding hot, but it's got to help I reckon.
Oh and edited again: if you're doing it again, I recon you can get away with a much thinner insulating plate, I don't think you want to lengthen the intake any more than you have to?
>> Edited by GreenV8S on Friday 5th August 22:45
GreenV8S said:
Ian have you thought about making an insulating spacer to go between the plenum top and the trumpet base, instead? As well as the insulating effect, it gives you more clearance over the trumpets - my feeling is this is one of the major reasons the aftermarket plenums work so well.
See above, Peter! I did consider doing both, I can add the plenum slab later without too much dismantling, I thought I may as well do this while I'm building the system up.
ETA: I have already shortened the trumpets; with the increased port runner length, maybe the effect will still be to give increased clearance over the trumpets...?
>> Edited by wedg1e on Friday 5th August 22:45
rev-erend said:
I seem to remember someone else (DJE)
www.djev8.com/
doing this (thermal insulating block £38)
but the problem is height - plenum rubbing on the bonnet..
Great if it does not - obvious advantage is no heat soak from the engine to the plenum
Nice job thought..
I think you'll find it's £60; the £38 one is for carbs...
I don't think bonnet clearance will be a problem on my car, but milling the trumpet base down would fix that anyway.
I did find a website for people putting RV8s into MGBs, where some guy had worked out he could lower the plenum, shorten the trumpet base and the inlet manifold and get a standard MGB bonnet to fit, but god knows what it did to the port tuning...
tallbloke said:
Colder air, more oxygen, bigger bang. Insulator keeps the plenum cooler so heat from the engine doesn't heat it up hence the air comming in.
Nice explanation professor.
My speciality. I am confused now
Ah maybe should have been denser air........I'll get me bull s!%t coat
I think what they mean is that (like a polystyrene cup)
the heat is NOT tranferred metal to metal, so warming the incoming air, so reducing its capacity to carry oxygen, so reducing combustion efficiency, so reducing power.
Hence, an insulated cup holder improves upon the above inadequacies.
the heat is NOT tranferred metal to metal, so warming the incoming air, so reducing its capacity to carry oxygen, so reducing combustion efficiency, so reducing power.
Hence, an insulated cup holder improves upon the above inadequacies.
Gassing Station | Wedges | Top of Page | What's New | My Stuff