anders44

well I found this map at http://www.rbracing-rsr.com, for the 26/6, anyone got something for 26/8?


anyhow I'm trying to decide on final turbo choices, I have narrowed it down to either GT30R 0.82, GT35R 0.82 or Borg warner S256.

seems the S256 is in the middle of them, has anyone got any experience with either GT35R or S256 on a stock 951 engine?

yes of course intake doesn't have the stock maf (running MAP) and intercooler/pipeing is upgraded, and exhaust is changed, wg etc but engine remains stock. since we have quite long gears I need to hit within boost rpm when shifting, but apart from that it is a racetrack only car. (not drag)

Duke

Sorry for not replying to your PM yet..

What boost/power levels are you aiming for?
I understand that you will race this car for longer periods? In that case I would suspect you will not go over 500 hp which make the GT30R the better choice.

Definatly so I you're running stock cam and such.

anders44

well i did the math on everything and will post it when at home.

yes its silly but my friends and me are known to go WOT through germany at night for transport, which means some of them topping out at close to 340kmh, gearing will reduce my speed though but saying I run 6500 consistant I will hit 280'ish and 7000 short burst should hit 300'ish.

then at nürburgring I will go around at WOT until gas tank is empty, then fill, then another tank etc.. its a high speed track and is actually quite good at cooling your car. as an example

my old car with stock brakes would last 5 laps there before there was no hope for brakes.. and at "rudskogen" which you probably know, it would last 5 laps there as well so cooling is way better.

I'm not so much aiming for an exact powerlevel as I am aiming for consistancy, im happy with whatever I get at say.. around 1.2 bar of boost which should be "safe"

anders44

here is the speed vs rpm of audi 016R on 944T with 295 30 18 rear tires. got the spreadsheet from an audi friend and just changed what was needed.

http://anders.fqdn.no/016R.xls

TRP951

the k26/8 should be the same map since its the same compressor

Duke

In that case I would recommend the GT30R with 0,63 a/r. That hotside will do the job without risking high backpressure at that boost level.

Even that compressor is on the large side if you're planning on leaving the engine otherwise stock without any VE improving mods.

Porschefile

A 3076R w/ .63 hotside will be plenty responsive and still capable of pushing a little over 450whp running high boost (like the 25-30psi area). Above that, a 3076R .82 hotside would be a better idea if you are looking for a bit more power as it can support as high as ~500-530whp, which is pretty much maxing that compressor out. Keep in mind, a bone stock motor is going to see significantly less power as 450-530whp levels are typically going to require a cam, headwork, or a stock motor with a massive turbo significantly larger than any of these choices. ;-) I think you should really ask yourself what power level you want and where you want the turbo to respond in the rpm band. A .63 3076r is generally going to make ~14psi at ~3-3.2k rpm on a 2.5l. With a .82 it will have a few hundred rpm more lag and make 14psi at ~3.4-3.6k rpm. It really depends on your driving style. Personally I feel that full boost anywhere below 4k rpm, especially with the quick transient response of a DBB center section, can't be considered laggy so I'd personally opt for the .82. A lot of people talk about lag without a real sense of actual lag. The difference between 1bar at 3k and 3.5k is minimal as unless you are in 5th gear, 500rpm will go by very quickly, especially with a DBB turbo that is already generating positive boost. Actual lag is when you bury the throttle at say 3-4k rpm and it takes 5 seconds for the turbo to wake up, and then you maybe see only ~1bar of boost around 4.5-5k rpm.

Don't waste time with something as large as a 35R if you don't want at least 500whp. It's a good turbo and will still spool plenty quick on a 2.5l, however it's just going to amount to unnecessary lag for a lower power level.

I don't know much about the S256 or those Borg Warner "extended tip" turbos, however I'm a bit skeptical. There hasn't been much in the way of published proof or large numbers of people using them yet, so it's tough to say. One thing I will say is, in several forums I saw multiple techs from Borg Warner basically trying to prove why their stuff decimates the competition. Every time they were asked any serious technical question, all they could do was respond by posting nice pictures of shiny, polished turbos. In the end, they got owned horribly and nothing seems to have progressed much with their stuff since then. I understand their concept and scientific logic behind their "extended tip" technology, I just don't 100% believe it's as phenomenal as they make it out to be. I've said it before and I'll say it again, Garrett is the largest turbocharger manufacturer, General Electric just bought them (now they are ridiculously large), they are an absolutely massive corporation (well as far as turbo companies go), and they use the most state of the art equipment, technology, and engineering to design their products. Simply put, they are the best and it's no small feat to top them unlike so many companies have so brazenly claimed. The Turbonetics GT-K series is another good example. They might be actual contenders or actually up to competing with the GT-R series, but I hardly think they will decimate Garrett as they claim. So far all I've seen is black/shiny painted compressor housings that are drilled for an anti-surge inlet (Precision has drilled anti-surge inlets like this for years, nothing new), and a lot of hype. Compressor charts, real world results, etc are all that really matter.

anders44

the 0.82 for the 30R is the "smallest" I have been thinking about an 3.4-3.6 is no problem at all, I really want the backpressure down since engine is stock else.

I'm having a 3liter 16v built, so this is a "until then solution" which should last out this season and most likely 2008 season as it takes time to sort the widebody stuff as well.

I got the S256 from a friend who has built many engines both with garrets, borg warners and whatnots, he had very good experience with them and it seemes it will fit between GT30R and GT35R in size.

I will see, its hard to get a non polished S256.. which is quite sillly, but they are supposed to be very cheap without it.

as for gt-k I was very excited with the news.. but the product has been out for quite some time now and still no realworld data?

iirc borg warner makes the VTG units for 997T and GT2 though?

for powerlevels.. I want a much as possible on a stock engine without blowing up under WOT for long periods with still decent response. I'm experienced enough to very rarely liftoff throttle unless I brake, so usually no problem

special tool

You are going to go through tankfulls of gas at wot with a 450 rwhp turbo and stock 2.5 engine?

anders44

I never stated a Hp number and I'm not even dreaming of 450rwhp number! . I'm saying I will go through entire tanks of gas, hence limited boost, lets say 1.2 bar max. but! I'm very open to suggestions here as well, but its stock valvesprings so they can't exactly keep high revs and high boost. I will have same 6500 revlimit as stock.

but since numbers are cool.. I am hopeing to see over 350RWHP though.

Porschefile

Anders, are you running the stock exhaust, stock afm and everything? If you are running a stock exhaust even, 350whp might be a bit optimistic for 1.2bar on a 30R. Absolute bone stock, stock exhaust, etc you're talking about an approximate 193fwhp gain simply from a turbo change and ~5.5psi more boost.

Borg Warner does make the 997 VTG turbos, however that doesn't necessarily mean BW is the "best" turbo manufacturer as many assume. Do a bit of research into Garrett, and you'll see what I mean.

gt37vgt

as for the first question the k26/6 & k26/8 are the same compressor map as the 6 or 8 are hot side and the hotside and turbine map wont be found .
I don't believe that garret being the biggest makes them the best technicly.
but being the biggest does make them the best choice . if you set the car up to take a garret life is sweat turbos are every were you can make changes to the comp wheels or exhaust A/R you can hear from people who have had that turbo on a car of the same displacment

333pg333

Just to clarify Anders. Are you saying that for a temporary motor you are going to run a reasonably stock 2.5L with a k26/8 and get 350whp?

anders44

only thing stock is engine, afm is gone and engine will run MAP, pipe to turbo will be a 4" to turbo, exhaust is not stock, wg is a turbosmart 48mm progate, ic is huuuuuuuuuge, pressure pipes are changed etc.. engine mgmt is standalone, bosch044 pump, bosch motorsport coilpack, billet fuel rail, 1000cc injectors, etc etc the exhaust header, or first part of it will remain stock, rest of exhaust is changed. brand new radiator is in and oil cooling is modified for the extra heat generated. radiator will vent up via a duct in the hood like 968 turbo, reverse vents are also on hood over manifold and intake/turbo.

no I didn't mean them as "the best", but I ment to say they apparantly have some very good products and shouldn't be knocked off. and yes you mostly find ricers with polished turbos running them.


I'm getting misunderstood here

anders44

nooooo man this is hard turbo choices are either GT30R 0.82, S256 or GT35R.


we all know the 26/8 won't work at thoose levels at all!