Adam

I'm not *knocking* the idea behind it, far from it, it's just that i wondered what sort of benefits you'll get when on boost cause i thought since air is being forced in under pressure (each cylinder will have pressure behind it, then they get their *slug* of compressed air when the inlets open), design may not be so critical.

Certainly off boost i can see a benefit in being more efficient and hence allow the engine to come on boost quicker.

As Andy (and as David says here) i think it was, told me many moons ago. Easy in easy out all helps in producing power. An engine irrespective of make is only a big pump after all.

 

I also don't really understand the left to right and front to back thing with the cylinders.

Why did Subaru design the inlet manifolds the way the did? and why is the std not good?
Can someone explain how it works?

 

I took it the turbo was going where the top mount was!!

There's a company in Glasgow that have a Subaru with the turbo in the above location just now, but i haven't seen it (too lazy to go down and look) and i don't know what the state of play or spec is.

 

Interesting

 

Thanks David

The cost is based on having a lot of the bits lying about such as the twin TB although you could use 2x std TBs...... if you have them lying around I might still do this as the ISCV and TPS will be an issue on the SVX TB

It's not going to be all alloy, most of it will be steel and I'll weld it myself.

Alan, just because an engine is forced induction its power (per bar pressure) is still dictated by its ability to flow air. You have gone with a 2.5, only reason for that is it flows more air and hence makes more power. A 2.0 with a 25% higher airflow would have given the same result.

Looking at 2 different efficiency engines,

1 - the scoob at 80bhp/ltr NA (once fully modified) that relates to a 2.0 version at 1.5 bar (2.5 abs) making 80*2*2.5 = 400bhp
Or looking at the 2.5 scoob running 2 bar boost 80*2.5*3 =600bhp
Both not far from reality.

2 - Now take a more efficient, free breathing, higher flowing/reving engine, the Suzuki Hayabusa. 130bhp/ltr NA (bog std) A 1.3 version running 2 bar boost will make 130*1.3*3 = 507bhp and yes they do ! the LSR bikes run over 650bhp.

Now make a 2.5 ltr version with the same breathing ability 130*2.5*3 = 975bhp
Quite an improvement Now the 2.5 scoob may not be too keen to rev to 9.5K but if the breathing (VE) can be increased and maintained higher in the rpm range then it will improve on the accepted 'norm' for a Subaru lump.

Finally, if Subaru improved the manifold with each generation, why do prodrive still use one that closely resembles the large plenum version of the 93 car

Andy

 

That'd be why I have your old inlet manifold Andy, which is recieving a few additional mods to the throttle body and other unneccessary bits and bobs

 

Thanks Andy. That makes more sense to me.

Quite thought provoking using that theory!

So what could be the reasons for Subaru changing the designs of the inlets over the years do you reckon? Emissions, ease of component fitment,coupled to costs of said components? ( TD04?, coilpack? etc)

You would think as the years rolled by, they would be more inclined to produce a more efficient manifold to aid emissions and VE to gain better economy (let's be honest, they're cr*p in fuel consumption).

 

I think the phase 1.5 and 2 was purely down to wanting to increase low end torque and for neater packaging, not a lot more TBH

 

Agree with Tim for Ph1 > 1.5 then more space for an intercooler I'd say from ph1.5 > 2 > new

 

As I understand it the phase 2 throttle body has an integral ISCV, and on the phase 1 and 1.5 manifolds the ISCV is separate and is fed from a dedicated runner that comes off the plenham chamber over one of the cylinder runners.

I was wondering if there would be any benefit in either fitting the earlier car ISCV directly to the plenham (which I guess in your case Andy you will have to as the SVX throttle body doesn't appear to have an integral ISCV), and blocking off the runner internally, or fitting the later throttle body instead...

 

ISTR the six cylinder stuff works works to increase low-mid range torque by separating the inlets into 2x groups of 3 cylinders. The Vauxhall one certainly worked that way, though I don't have the Porsche info. At higher revs, the separator plate is removed allowing all of the cylinders access to one body of air.


J.

 

Any updates Andy and pics

 

 

Which part are the Velocity stacks going into, the Plenum?

Whats the black stuff on the tubes feeding 2 and 4?

Steven

ps Get them welds smoothed off

 

**** me is that turbo going to be big enough

 

looking good Andy

 

what turbo you using now? Same as mine?? or bigger?

 

PS Looking good.. giving me ideas

 

surely a 200shot will give you all the extra top end you need!

 

I've allready got that one covered as you know.. all be it only 150max

 

Velocity stacks will be inside the plenum, the black stuff is just paint that was on one of the manifolds I cut up.
Turbo is very similar to yours David, rated at 150bhp more than my last one .....who needs nos

Andy

 

looking great.

nice to see it actually being done shortly after being spoken about.

Am looking forward to the results.

btw, don't you think any of the limiting factor of the breathing/ve of the engine comes from the head design/geometry?

 

Andy-
You say you have uprated the turbo again- do you have a base set of figures to work from using that new turbo to gauge any improvements before the IM alterations?

I like your theory.. Am looking forward with interest to the next installment of this thread.

 

What he ^^^ said

 

Me too..
Graham.

 

I wish i could add something constructive but i'm just sitting here wishing i had the forward thinking to develop something like this myself.

Nice to see you posting like this Andy, rather than keeping it all under wraps for commercial gain like some others.

<thread subscribed>

 

Not sure I'm going to be able to complete this prior to SSO. There are so many other jobs to do on the car if I intend run it, such as making the new intercooler and radiator, relocating the PS and Alternator (to fit the twin TB in)

Not to mention a busy diary of customers also planning an attack on SSO themselves

Some progress however

Rolled sheet of thin steel plate




Just cutable with tinsnips






The disc gets welded to the 2.25" bore short stub of exhaust tube, this is then welded on to the end of each rolled plenum chamber tube. The plenum is joined to the individual runners with short sections of silicone hose. This also allows for some expansion differences.




Looking down the plenum...

 

With it now

You not worried thats too thin for "ballooning" ?

 

If it was any other section other than round then yes I would be.

Andy

 

nice way of going from ally to steel.. what dia is the plenum?

Im pre'za'suming dual plenum?