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09-07-2007, 07:43 PM | #1 |
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HOW BIG ARE THE STOCK TURBOS
I know a stock audi s4 2.7 biturbo has two ko3 turbos. A swap to ko4 turbos and a few goodies picks the car to 450hp. Anybody know if the stock 335 turbo´s compare in size to the ko3 used by audi. Any predictions on a big turbokit for the 335/135. I guess a pair of not to big (ko4 size) turbo´s could hit the 500hp zone with out a dramatic effect on lag and driveability.
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09-08-2007, 12:58 AM | #5 |
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Ummm, I'm pretty sure they are Mitsubishi TD-07's. They literally max out 11lbs boost at 6k rpm. Raising boost From 8.5lbs @6k to 10lbs added 40whp adjusting for timing and a/f ratio all other things equal. It will be interesting to see what would happen with one size larger twins that could push a mild 15-18lbs at 6k, 475-500whp? Remember, this engine has direct injection and the b4 s4 doesn't.
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09-08-2007, 02:09 PM | #6 |
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I've been following this thread at e90post about a tuner who's already removed the turbos. Some good info in there - http://www.e90post.com/forums/showthread.php?t=78155
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09-09-2007, 01:48 PM | #7 | |
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here is a 25g td07 compared to a 20g td06 |
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09-09-2007, 04:56 PM | #8 |
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09-10-2007, 12:15 AM | #10 |
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09-10-2007, 06:15 PM | #12 |
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GT35R is totally defeating the purpose of 300wtq at 1400rpm... If I was building a top end car I'd get a Precision PT76 and make 600+whp at like 5000rpm and then burn rubber at 80mph... unless your on the highway... personally for top end its great but i'd personally go with 2 DBB 50 trim's for top end... or two 16 g's for a street/strip car...cuz lets face it... DSM's make around 350whp max on a single 16g... thats around 650whp max on 2 16g's and if your not happy with 600whp on race gas and rubber burning fast spool up then you got issues lol...
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09-10-2007, 08:09 PM | #13 |
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Who said my purpose was 300wtq at 1400rpm?
Imho going from a Td03 to a Td05 is a big jump at this point. We don't know what the block can handle or what the fueling system is capable of. History helps us to learn to take baby steps. I don't know about you but i am going to be very cautious with my mods and do enough research so that i won't make a very costly mistake. I don't know about you but i am not in a financial position to be a pioneer of the N54. I am not looking for top end but rather something very streetable and efficient. 16g's with 10.2:1 compression should give you spoolup at ~3500 rpm... I am looking for boost around 2000-2200 rpm. |
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09-12-2007, 05:46 PM | #15 |
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I'm a turbo noob. But I know going from 8.5 psi to 10psi on the n54 netted 35whp/75wtq @5700rpm. I'm sure the law of diminishing returns kicks in at some point or that the more boost added you get diminishing returns. What size turbo's would it take to get to about 5oowhp? Considering were already at about 390whp with FMIC TBE and procede v2? I think the drivetrain could handle it. You would need new fuel injectors, which I've heard aren't available yet for the DI. If 1.5psi added 35whp would another 5psi add about 100whp? What's the smallest size dual setup that could push 15psi at 6k rpm and be within operational limits?
I'm sure there's more to it then this but humor me. BTW, the stock injectors are already operating at 80-85% of max with procede v2.0 per shiv vishnu. |
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09-12-2007, 05:48 PM | #16 | |
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09-12-2007, 08:40 PM | #17 | |
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There are exhaust and FMIC solutions on the market already, and those combined with larger turbos, should easily net you the power you are looking for. The main block we are at is the fuel injectors. I don't know of anyone making aftermarket direct injection injectors. There are a few guys on e90post upgrading turbos already, but I wonder what they will do for fuel. More boost is fine...until you run lean. :frown:
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09-13-2007, 11:24 AM | #18 | |
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I hope everyone realizes that DI fuel injector upgrades are going to be pricey. |
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09-13-2007, 12:41 PM | #19 |
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How about a pairing of turbos? If one of the two stock turbos were replaced with a slightly larger, higher capacity, slower spooling unit, it may be good way to expand the power band. Assuming both compressors feed to a common intake plenum, all cylinders would be experience the same upstream pressure response. The wastegate could be used to vent excess exhaust gas past the smaller turbine to prevent excessive turbo manifold pressures, in an attempt to match the manifold pressure occuring upstream of the larger turbine.
Or just throw two variable turbine geometry turbochargers on the car and call it a day.:biggrin: |
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09-14-2007, 03:31 AM | #20 | ||||
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power = flow(cfm) boost = resistance to flow 16psi on 10t's is not the same as 16psi on a GT35. Depending a lot on volumetric efficiency, 16psi can net you 500whp. psi is a measure of air pressure not air mass. For < efficiency you want the lowest psi with the highest air mass. The smallest twin setup for 15psi @ 6k would be 13g's but they wouldn't efficiently get you to 500whp You would net more whp with 15g's @ 15psi/6k 16t's would be even more efficient because its a newer, lighter wheel and flows similar to 15g's. It is not likely these turbos will get you 500whp@16psi Quote:
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The turbos would be working against each other and create a symptom called surge. There is a couple types of surge, but without getting too in depth, it is always bad. As the larger turbo spools up, that increased pressure would be greater than the max pressure of the smaller turbo. That increased pressure has to go somewhere, so it would 'choke' the little snail and decrease the expected lifetime. This can also work vise-versa depending on turbo size/application. You would have a less efficient and reliable system compared to a proper symmetrically sized turbo app. If you were to attempt to correct deficiencies in an asymmetrical system by leaking exhaust gas, you are now left a problem of how to properly gauge manifold pressure and you are still left with the surging. On top of that if you don't correctly equalize manifold pressure then you are left with 3 cylinders making more power and thats no good. my .08 ~Zak |
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09-14-2007, 11:54 AM | #21 | |
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Good stuff, thanks! Considering with procede v2 and TBE the n54 is putting out 365whp@10psi@6k rpm, you don't think twin 16t's pushing 16psi @6k rpm would get you to 500rwhp? Maybe 475? What do the stage 3 S4's run on? I know they have 450-460 AWHP out of a 2.7t with upgraded turbo's. It will be exiting to see what happens. Anyone hear about a new TT v8 in development by BMW for the x5/6series/7series? Probably a heavy engine but........ |
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09-14-2007, 01:43 PM | #22 | |
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500bhp maybe. 500whp? Not on pump gas... and more like +20psi @6k Depending on the stock system it would probably need 1500cc of meth injection to quell knock. Along with supporting mods: FMIC, intake, catless +3in TBE, colder plugs, clutch/flywheel, CF driveshaft, intercooler sprayer, custom tune, possibly bigger oil cooler and other ways to reduce heat, other monitoring devices w/ logging capability's, oh and not to mention a way of getting that power to the ground, etc..... Not for the faint of heart... But like i said, its still all speculation at this point.. Obviously a lot of factors come into play. I don't have an N54 yet so i wouldn't know if there were some key bottlenecks... Ie: intake manifold, head design, head gasket, compression induced knock, and all those aluminum bolts. I am not too worried about the CR and wouldn't lower it for anything, but it will get more and more difficult to raise boost without some higher octane(meth, propane, race gas). There are supra guys that build 11-11.5:1 blocks in an effort to spool huge turbos and they get along just fine. |
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