The Superboxer, a new heart for the Silver Bullet

[silverbullet]

PPS the reason for all this overchecking is that I need to cram this vacuum bypass valve in here, and there isnt much space to be had (the lifting eye on the case will have to go and be replaced by a bolt-on)

Down at eye level, I will have to make a 90 degree duct to mount the valve onto the compressor inlet:

You can see why the lifting eye will have to go...

[silverbullet]

All credit to the wbx faithful.
7" or 175mm from lifting eye to a compressed hatch seal i.e. the underside of the hatch without foam. Might have to go grp, it would be lighter too
Thats all the headroom I can have.
I am NOT raising the hatch.

[silverbullet]

Think I will have to completely remake the compressor inlet plenum to set the bypass up something like this:

Its only a lump of alloy with a few holes and a pocket or two. Reeling it in....

[silverbullet]

Its all falling into place
Shuffled things around and ended up with the compressor at a similar height to the original installation
But now the alternator can go back in the correct place, which means no obvious clearance problems with coil-on-plug (when I decide on the type)
A few views and its still going to be tight, all pretty self explanatory:

Compressor moved nearer the crank pulley end, to make space for the bypass:

Intercoolers will be hard back against the front of the engine bay:

Bypass valve repositioned to feed into the end if the inlet plenum, awaiting 90 degree hoses:

170mm tall

This is going to look tasty with the hatch up:

So... next jobs include making extension tubes to connect discharge plenum to the chargecoolers, make a slightly thinner adaptor plate to connect the d/c plenum to the compressor (welded on with bosses for 6 bolts), bandsawing the remaining outlets off the chargecoolers and making some new ones (more welding), making an inlet extension to connect the throttle body to the comp. inlet....
Then build an engine for it to feed

[ozzi_in_the_uk]

Well there's gonna be no hiding that from the insurance assessor as he peers into the engine bay, ...thats for sure!!

[silverbullet]

At least there will be a WBX engine with a DJ number under it all

[silverbullet]

I am giving a little thought to the basic engine spec, now that it all looks feasable.
So, 69mm crank or 76mm? Or something else? I will definitely have one fully counterweighted by DPR whatever, along with some other cheeky mods
69mm with the 137mm rods gives almost a 2:1 rod ratio (not ideal on a blown motor, the piston will spend too long at tdc and so risk picking up too much heat) but a nice flat bowl in the piston at 9:1 static compression.

76mm stroke and 137mm rods gives a ratio closer to 1.8:1 which is much better in that regard, but at 9:1 comp. the piston bowl is a mess.

I need to find a 3rd way... some new forged pistons will be needed anyway. Add slightly longer thick wall barrels, deck plates and longer pushrods would do it, but that will mean longer head studs, unless there is enough meat in AMC's to allow setting the head nuts a little deeper.
3mm would do it...

I need to delve into my Green Bible again...

[busbuddy]

i would stay under 9:1 if you are going to use the 22psi on a regular basis

[silverbullet]

12 or 13 psi on the gauge, keeping under 1 bar.

Penny dropped while making a cuppa and holding an old DJ piston:

Reduce the bore to 92mm!

This will give an engine of 2020cc and with DG/DJ style pistons a SCR of around 9.7 and so only minimal mods will be needed to the design or the combustion chamber

A side benefit will be an extra 1mm in the new barrel walls, for no effort.

PS I think the latest supercharged Jags are now running 9.5:1 with the latest generation high-helix rotor Eaton blowers, but have VVT and of course the spark plug is in the middle, being 4 valve so they will always burn better.

[busbuddy]

sorry i thought you had said before that 22psi was easily achieved

9.5:1 is ok if ,like you say, the burn is good and you have finite control of fuel/air to stop detonation

will you be using the standard ecu or will you go bespoke?






we didnt use the screw chargers much for racing, went straight from roots to prochargers to turbos

[silverbullet]

I think my earlier calcs were a bit off! Intrigued to hear what you have built in the past...

I have a clean sheet for EMS, but since I have taken the space occupied by the dizzy in moving all the bits around I have no choice but to go full sequential EMS.
Might still use a hotwire AFM, might go for MAP.
Not really looked into it much so far, the mechanical work is the big challenge compared to a few sensors and wires.

Did a bit on the d/c plenum this avo, including chopping up the shonky original one to use as a guide template for the ports:

Hmm...

This has worked out nicely:

Just needs the bolt tube bosses making and welding in place:


One for Duncan, the only performance graph I can find are for the slightly larger 2087 (0.87l/rev) but it gives an idea of ▲T values:

[DSM]

Hi Ian,
well this confirms the previous ball park calculations.

At 15000 rpm the power absorbed is 25Kw/33.5 Hp at 92% efficiency ( quite amazing).

For an inlet temperature of 20C the discharge or outlet will be 108C so still looking around 18 to 20 Kw of cooling at peak power to keep below the notional 50C. Not as onerous as you think though because fuel vaporizing will add a good amount of cooling ( we can calculate this as well if you can estimate peak flow against peak power).
This is where a water-cooled system is an advantage as it will absorb the peaks.

Duncan.

[DSM]

Now for the geek bit.
At full chat if the air mass flow is 15Kg/m then at 14.7:1 the fuel flow would be 1.02Kg/m. Depending on the fuel grade the latent heat of vaporization is 628Kj/Kg and this works out at roughly 10.5Kw of cooling all based at atmospheric pressure as dealing with fuel pressure over boost pressure is really complicated. Not allowing for losses that knocks the load back to a nominal 10Kw.
This will be a thirsty beast if you have a lead foot.
Duncan.

[silverbullet]

Thanks for that Duncan. I am on the right track then.

Bear in mind that this compressor only displaces 0.76l/rev but is also rated at 15krpm... continuous

The Green Bible recommends water/air chargecooling for that very reason, if the complication and costs are disregarded.
DIY and reworking cheap Jag parts is proving cheap and not too complex in this case (now it all seems to fit)

The compressor is supposed good for engines up to around 180/190kw, so that is knocking on Audi S6 2.7 Biturbo territory.

It was never going to be frugal, but that was never the point of the exercise

[silverbullet]

While the plenum is off being TIG welded I had a moment of mild panic: I hadnt given any real thought to the length of the inlet runner lengths or size...
The optimum length for a 2-valve supercharged street/hillclimb/rally engine is 300-330mm long @ 0.9 times inlet valve diameter.
A tape rule curved down the inlet port from the valve seat to the manifold face shows around 90mm at the centreline.
A crude straight line measurement from the manifold face up to the lower plenum on one chargecooler comes in at 200-210mm

So that leaves 30-40mm which will be easily used up in the bend, where the manifold runner curves down to meet the gasket face.

That's worked out nicely then