S2 & RS2 turbo comparison

[S2central.net]

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 ?

RS2 turbo limit is approx 380bhp
RS2 injectors are approx 420bhp (at ~4bar FPR)

[S2central.net]

Further to this, I opened the RS2 turbo for investigations today... Remember I bought this as unit for a good price as it had been reco'd before a crack in the hotside was detected.

Sure enough, externally you cannot see any damage - but when i removed the RS2 hotside housing I quickly saw several very visible cracks.

No big deal, as I have my spare S2 turbo to offer up to the turbo rebuilding pixies... But no - I opened it up and saw cracks in the same places immediately after cleaning off the surface carbon/coke. Very fupped off - these cracks aren't as extreme but I'll have to get professional advice. Failing that just locate another S2 turbo that is collecting dust in someone elses garage.

Oh I snapped some pics along the way and dumped them here for anyone that cares - http://homepage.mac.com/nugentp/PhotoAlbum14.html

The two hotsides are damn near identical. Both stamped as a number '6' with the same part number stamped on housing - only difference is the RS2 item is stamped with a '2' whereby the S2 item is stamped with a '3' in the same location. That is maybe a fluke, but could be consistent with the RS2 A/R of 6/12 (0.5) versus the S2 A/R of 6/13 (0.46).

Only real visible difference is the larger diameter in the RS2 housing to accomodate the larger turbine wheel. That could be machined easily IMO... On close inspection you can just see one or two areas on the shape of the RS2 scroll that looks a tiny bit different from the S2 item.

The two turbine wheels are visibly different for obvious reasons. It would be interesting to know if there is a turbine wheel between the S2 item and the RS2 part. That would suffice for me if it can still produce 320-330bhp with less lag than the RS2 turbo.


Paul

[Corey]

@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.

Chosen for their compatability to "RS2 type software" as stated on 034 website and I quote

Flow matched set of "RS2-sized" injectors for use with RS2 software in the Audi 5-cylinder turbo.

Save over $300 on OEM RS2 injectors, flow matched, newer design injector.

Sold per set of 5 flowmatched.

quite a bold statement if they are not supposed to work with that type of software? but custom mapping is always better.

oh and the page from the website is here

http://www.034motorsport.com/product_info.php?products_id=369

I believe there are a number of people over in the States that are using these injectors with MRC chipsets.

[Mihnea]

As much as I have nothing against 034 because I've known Javad for ages, that statement is false. My US Stage 3 chipsets are made for the cheaper Lucas 37lb injectors.

Mihnea

I believe there are a number of people over in the States that are using these injectors with MRC chipsets.

[Corey]

As much as I have nothing against 034 because I've known Javad for ages, that statement is false. My US Stage 3 chipsets are made for the cheaper Lucas 37lb injectors.

Mihnea

I know what you chipsets are made for, I have only stated the fact that I believe people are using these injectors with your chipsets. I didn't say you had done the chip for these.

[S2central.net]

Are we going off-topic here or what ?

[porkkis]

I find it annoying that Corey offers his products in every single thread where possible.

[twoqu]

Hi Paul!
Thanks for the pics. It is useful to see comparsions. Might be useful to see a comparitive pic of the two turbine wheels. I am assuming that the major dimensions are the same but the minors differ. Inded some approximate measurements would be cool too! I believe the S2 has a 48mm exit and the RS2 55mm.
I am begining to suspect that the 12 and 13 designations are related to the trim. Bit like the Garretts where you have the A/R and then the letter designating the trim of the turbine wheel. So you have a family of housings all with the same A/R but matched to the trim of the turbine. Usually this means that the exit is larger as it is only the minor dimension that changes.
Its difficult to assess the turbine damage. I wouldn't like to use the RS2 one. It looks fooked. Unfortunately this appears to be quite a common problem and not cheap(£400?). The cracks on the S2 one don't appear that serious. Bit like the cracks you see on exhaust manifolds. I was told once that cracks are inevitable due to the heat, but it would be nice to start fresh again. To get a usuable turbo, I would certaintly look at getting this machined to the RS2 size.
Of course this intermediate shaft you are looking for is the 50mm minor which looks like was used by all the German tuning firms to produce the "small" RS2 turbo. As this was from the K26 range I'm assuming the RS2 comp side goes straight on.
There are other "rumours" about the RS2. One being the shaft has a lefthand thread. Another is that it is of different material, which will be difficult to prove.
One thought. Clearly the German tuners would have had the option to base their small RS2 upon the K24. They didn't. Whether that was because the turbine side was too small or the problems of grafting the RS2 comp wheel on the shaft was too much trouble is debatable. Probably both!

[Mihnea]

The small RS2 turbos were built based on the oil cooled K26s from the old Audi 200, they had a 50mm outlet with a #6 hot side. IMHO that combination is almost useless, spoolup is just as bad as an RS2 if not slightly worse and the amount of back pressure that you get at high RPMs means that 320-330 BHP is an absolute maximum you can get out of those turbos. 300 would be on the 100% safe side, stock-like (or idiot-proof) reliability.

HTH,


Mihnea

[porkkis]

The K26 50mm turbine wheel can be found from porsches (non turbo s 944).

AFAIK the s2 and rs2 shafts are of different thickness. The 944 shaft (+wheel as they're one piece) might be bolt on to RS2 center section, but not s2.

S2 turbine diameter is 46mm.

MTM hybrid had the 50mm turbine (with RS2 cold side or just bigger wheel machined to small std housing?).

@Paul, nasty cracks. I wouldn't use that.

[Mihnea]

I'm definitely positive there has been an Audi 50mm turbine K26 as well, oil cooled AFAIK.

Cheers,

Mihnea

The K26 50mm turbine wheel can be found from porsches (non turbo s 944).

AFAIK the s2 and rs2 shafts are of different thickness. The 944 shaft (+wheel as they're one piece) might be bolt on to RS2 center section, but not s2.

S2 turbine diameter is 46mm.

MTM hybrid had the 50mm turbine (with RS2 cold side or just bigger wheel machined to small std housing?).

@Paul, nasty cracks. I wouldn't use that.

[twoqu]

Ok!

For the record:
K24 (6.13) outlet 46mm.
Early K26 (6.91) outlet 50mm
Late K26 (6.95) outlet 56mm.
Porkkis states that the Porsche 944t(220bhp) has a 50mm outlet. I believe that is what Hohenester used as its designation is 6.92.
I believe that the RS2 has a 55mm outlet. Perhaps Paul can confirm this.
Ultimately it depends what you are trying to achieve. Obviously the smaller turbines are going to suffer at high rpm. I guess the RS2 was partly specced for durability/warranty concerns.
Mik's observations about the relative advantages of the "small" version are important. The only advantage I can see is if it improves drivability. If the chacterstics are the same, and you have the rest of the RS upgrades, then it doesen't seem worth the trouble and expense to limit the potential.
Will have to look at what other mods these companies used to compliment the turbo.

[twoqu]

Mmmm..
Just reading through one such article on the Nothelle N300. The tester comments that it has "noticeable lag" compared to the standard version. However the performance figures show that the modified car is quicker everywhere including 30-50 and 50-70 in gear acceleration. Just shows how subjective things are!

[porkkis]

I believe you're right. The earliest 10v turbo engines had smaller turbine than the usual 55mm.

I'd say 50mm turbine and about 46mm compressor would be ok if only slight performance increase is what one is after. This would mean the stock injectors etc would be retained and therefore keeping the cost down.

@twoqu
RS2 exducer is 54mm and different to K26 55mm.

I'm definitely positive there has been an Audi 50mm turbine K26 as well, oil cooled AFAIK.

Cheers,

Mihnea

[Jonas_R]

Ok!

For the record:
K24 (6.13) outlet 46mm.
Early K26 (6.91) outlet 50mm
Late K26 (6.95) outlet 56mm.
Porkkis states that the Porsche 944t(220bhp) has a 50mm outlet. I believe that is what Hohenester used as its designation is 6.92.
I believe that the RS2 has a 55mm outlet. Perhaps Paul can confirm this.
Ultimately it depends what you are trying to achieve. Obviously the smaller turbines are going to suffer at high rpm. I guess the RS2 was partly specced for durability/warranty concerns.
Mik's observations about the relative advantages of the "small" version are important. The only advantage I can see is if it improves drivability. If the chacterstics are the same, and you have the rest of the RS upgrades, then it doesen't seem worth the trouble and expense to limit the potential.
Will have to look at what other mods these companies used to compliment the turbo.

Well I can confirm that with Hohenester since my setup is from Hohenester, and it is a K26-2672 GGC 6.92 and it is watercooled. I have looked at the cold side and the part number says it is an RS2 unit. So this seems very true. I then asked Hohenester about the max on the turbo and the told me that it would do max 340 bhp and they also claim they use it because it has better spool up then the rs2 unit. They promise ca. 310 bhp on stock setup, using there own EM and turbo, the 340 setup is the same but with a larger intercooler.

/Jonas R.