S2 & RS2 turbo comparison

[Ross]

Just done the math based on ...

f1/f2 = sqrt (p1/p2)

Assuming f1 is 320cc at 4bar fuel pressure on the S2 injector, I get 357cc for the same injector at 5bar.

Using the rule of thumb of 1bhp per injector cc, I'm looking a theoretical capability of nearly 360bhp then - with 98RON or better fuel. Knock (no pun intended) 10% off that for rubbish 95RON fuel and I get 320bhp on this configuration.


Thats the theory as they say


Paul

lol... hope you're better that me mate, spot-on with the theory but it all went to woofwoofwoofwoof when put into practice. Surely you can fit a space for 5 RS2 injectors in the budget, in the name of research? I reckon £150 or so would get you a set used.

[AnLe]

here is yet again measured flow of an rs2 injectors, rise is not propotional to the pressure, and propably not even linear.

at least my 3rd posting telling same, where is the source of the information that they work like and "ideal machine"

Not to mention, your 044 is not good pump any more at the 7 bar fuel pressure (your 5 at base pressure + 2 of boost)

[S2central.net]

Who said the rise was linear ?

Certainly not me... The formula is f1/f2 = sqrt(p1/p2) and your flowbench figures bear it out pretty well.

Who said I was planning 2bar boost ?

I know plenty people using the Bosch mosport pump with 5bar rail pressure in high boost S2 applications well in excess of 400bhp - that pump is plenty up for the challenge --- but I will look at the output spec's just to be sure...


Paul

[AnLe]

ok, mybad, I misunderstood.

What, audi with less than 2 bars? thats like making it N/A

Onething, people speaks motorsport pumps when they mean 044'ses, the real motorsport part numbers starts on B and there is even bigger pump than 044 and that's a real motosport pump, I would use that if I were possible to buy, some uk rallyshop listed price for it even.

[Audi Parts Guru]

Does anyone here have KKK catalog ?

Paul

I do

And it's bang up to date

[twoqu]

Hmmm...
On the turbo front. I have double checked the K24, K26 and K27 bearings and they are the same. The centre housings look the same to. So therefore all the shafts must have the same OD at least in the centre housing. The K24 has a 6mm nut rather than the K26/27 7mm. So the K24 shaft must have a reduced diameter at the compressor end.
So the question now is whether the RS2 shaft uses the larger nut. You might be able to determine that visually.
On the turbine front. These figures 6.12, 6.13 etc. The same source indicates that the first number is the A/R. Unfortunately it does not go on to explain what the other number indicates. The earlier K26 used 6.95 and 6.91 housings. So if dividing one by the other do you use 95 or 9.5? We could do with a definitive answer just out of interest.
So in theory it might be possible to graft the whole RS2 cold side on to the K24 hotside. There is a large amount of commonality.The biggest problem is going to be whether the RS2 has the larger shaft diameter at the compressor end. Even if it did, I have seen people graft comp wheels from the Garretts by reducing the comp wheel ID with a sleeve. I guess anythings possible! Whether it is worthwhile is another matter. To address the small hotside you could backcut the turbine wheel to free up the top end but obviously at the expense of the spool up.
Potentially quite an expensive business I guess. Only one KKK turbo has fell apart in my hands. I have tried to get the comp wheels off others without much success. Recluctent to tap the shaft. Might be able to give more info if my "consignment" arrives.

[porkkis]

Std s2 K24 uses K16 bearings AFAIK.

[AnLe]

one route: take a perfectly good k26 from an old 10v turbo engine, put the rs cold side to it, result:

[Corey]

I reckon £150 or so would get you a set used.

Why buy used when I can supply a new set of RS2 spec injectors for £170 (plus delivery), they have the same flow rate as the original RS2 injectors and they are flow matched, something which the genuine ones aren't

[Chris M]

Nice price Good result with the turbo btw

[twoqu]

Yep!
Thats what we think Hohenster, MTM and Nothelle did. Although there are two different 10V housings. Hohenster used I believe the early 944t housing. This is the "small" RS2.
Thats what I'm planning to look at. Just need to get my mits on the right bits! No sense in buying a good turbo and stripping it. In the interests of the planet I thought it would be a good idea to make one good turbo out of two dead ones!

[porkkis]

951 turbo S has audi compatible #8 housing with 55mm wheel (hen's teet sort of thing..). The non S model has #6 50mm.

@Corey:
I'm sceptic that "about the same" injectors may be used inplace of the real thing. This means mapping wise. If the software is for RS injectors then you have to use them and nothing else. There are also lots of other parameters than just the flow. Opening time for instance.
For custom mapping - sure why not.

[Mihnea]

Antti, this graph looks like massive back pressure and knock control kicking in at 3800 RPM.

one route: take a perfectly good k26 from an old 10v turbo engine, put the rs cold side to it, result:

[AnLe]

maybe, that is also the point where wastegate opens and maybe the output of the turbo is reached there, but rs2 housing is even more smaller - bigger backpressure and so on.

btw. thats with stock everything except cat-back exhaust and some freeflow filter.

[Darkside]

beyond rs2

As the discussion has mentioned turbos / injectors / fuel pump,
does anyone know the max limits of these things? (beyond an rs2 setup?)

rs2 turbo around 400 bhp ?
bosch 044 fuel pump around --- bhp ?
rs2 green injectors around --- bhp ?