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-   -   Question for Wyd (or others) re gt35 (http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/324202-question-wyd-others-re-gt35.html)

greglepore 01-10-2007 05:58 PM

Question for Wyd (or others) re gt35
 
Thinking about converting. What A/R and trim are you running?

YermanCars 01-10-2007 06:02 PM

I have a special non ball bearing turbo, that will out perform the 35r for half the price.

PM if interested.

930gt-40r 01-10-2007 07:16 PM

I dont know what Yerman has, but I am going with 1.06, with the "e" cover for the cold side becuase I have heard that the 4" inlet on the bigger housing is a pain in the @$$ to fit with the sheet metal. Are you going to use ball-bearing or no?

greglepore 01-10-2007 07:33 PM

This is for a low boost setup, I'm just interested in gaining spool over my existing, somewhat obsolete, turbo. Ultimate hp isn't as important as getting some response below 3k. I'm leaning towards bb, but I could be convinced otherwise.

930gt-40r 01-10-2007 07:38 PM

I am new to ball-bearing and am waiting arrival of my 35r, I have heard many people run them and be very happy. It is defenatly an update from any of the stock replacement junk. However I have seen some nice k-27, k-29, "K-28" hybrids out there. I just dont like how porsche does not use bbs. I think they do it to stay on the safe side for longevity purposes

YermanCars 01-10-2007 08:15 PM

I have ran a custom Gt40 turbo, it sucked. Too laggy and no throttle response, but when it hit, it took off.

I was going to get a custom Gt35r, but the Guys at Precision built me
the turbo I have now. It is a custom turbo built for me by Precision turbo, I can't give out the details really. It is a 60 trim turbo w/ a t4 flange and v band clamp, but can be built w/ a t3 or t3/t4 flange on a 3.3l w/ 7:0 comp. Full spool @ 2,900 rpms and pulls all the way to red line. I made 430rwhp @ 1bar w/ a chipped motronic based system.

The turbo runs about $700, the bb option can be added.

Porschefile 01-10-2007 11:29 PM

Quote:

Originally posted by 930gt-40r
I dont know what Yerman has, but I am going with 1.06, with the "e" cover for the cold side becuase I have heard that the 4" inlet on the bigger housing is a pain in the @$$ to fit with the sheet metal. Are you going to use ball-bearing or no?
Why the 1.06? That's going to be unnecesarily laggy. A .82 T3 or .81 T4 will work just fine and still be good for lots of hp. I'm not sure what displacement you're running but, with a 3.0L+ you'd be fine with a .82 T3 or .81 T4. On a 3.0l, 3.3L or any larger combo f6 I'd personally run either a .82 T3 or .81 T4 on a 35r. A .68 T4 would work fine too. There is also a neat .78 T3 divided housing which will help it spool even more quickly, and it would be sufficiently sized. I honestly wouldn't run any smaller hotsides than what I've mentioned here. These motors generate a large enough exhaust volume that running anything smaller, while it will spool a turbo more quickly, will be sacrificing a serious amount of power. How much power do you want, at what boost level, and what kind of spool do you want?

I'd really like to see more GT series turbos on Porsches. There are some excellent improvements with these turbos over the older T series stuff. While many of the GT series turbos may have similar boost thresholds to their older T series counterparts, one of the biggest improvements is transient response. Basically, that means being able to roll on the throttle and receive nearly instantaneous boost response compared to the second or two delay it might take a T series turbo. Of course you can't necessarily do that at 1000rpm and expect it to build any boost but, you get the idea. Also, the turbos stay spooled between gear changes much better so they don't have to spool back up when engaging the next gear. The wheels are redesigned and have improved aerodynamics, so they are more efficient and will create more power compared to a similarly size T series turbo. Honestly, I think some of the benefits of the GT series might be lost on many 930's. One of the major benefits of the GT series is with the redesigned internals, the wheels are lighter AND stronger, plus the ball bearings maintain tighter tolerances. This all equates to turbos that are capable of reliably withstanding extremely high boost pressures under constant usage (like 30-40+psi, depending on the exact model). Also, some of the GT series are in their max efficiency "island" at some higher boost levels than the older T series stuff. Not too many 930 owners run anywhere near that pressure, so some of the power benefits might not be as noticeable. Most of the GT series line really starts to "wake up" above 20psi. Most of the Gt28's, Gt30's, Gt35's, etc tend to have their max efficient islands around the 20-30psi range, depending on the exact turbo (Gt28's and Gt30's are great right around ~22-25psi). In that regard, power wise, you really might not see huge differences from the T series stuff. Though, the improvements in response are still there. Anyways, that's one thing to consider. If you're just looking for power, the older T series stuff can still give you ~80-95% of the same performance unless you are running high boost pressures. Geez, sorry to type a novel! I love these turbos as you can probably tell. At the moment I'm installing a gt35r on my 951 ;)

Guys, there are some general guidelines about the Garrett GT series that are very important to follow, otherwise not doing so can lead to a significantly shorter lifespan. The GT series do not require nearly as much oil supply as an older T series turbo. Technically they shouldn't run much more than ~40psi, otherwise you can cause the turbo to start leaking oil due to excessive pressure. For most cars, that's a relatively low pressure so 9 times out of 10 you're going to need an oil restrictor. The exact size restrictor is really going to differ between cars with different motors. Also, the GT series were designed to be used with oil AND water cooling. Simply not running any water can lead to short bearing life. Some people have tried running oil through the water ports, which apparently seems to work okay and is definitely preferrable from just running the water ports dry. You can also of course add a small water tank and make a simple water supply setup for it though this might be a bit too much trouble for some people. Either way, don't simply run the coolant ports dry; at least supply them with oil. Hopefully someone that has used them on 911's more (like Wydryd) can give a bit more info into this.

Yermancars, was it by chance the plain bearing Gt4088 and not the DBB Gt4088r? I'm thinking about a Gt4088r on my 3.4l. The 4088r is quite a bit more responsive than the non ballbearing 4088. The boost threshold still isn't going to be all that low though transient response is significantly improved so the turbo will "respond" much more quickly rather than taking several seconds to spool. Judging by what I've seen of the 4088r on some ~3.0L i6's, on a 3.4l f6 it should be pretty responsive (meaning full boost ~3.8-4k) for a 700whp capable turbo. Hehe, it's tempting to me to just go all out and do a Gt42r! ;) I personally don't mind higher boost threshold (not lag) as I love the way big turbos "hit".

Greglepore, what displacement do you have? The typical 3.3l or something different? If someone wants an ultra responsive setup for a 3.3l, a gt3076r with a .82 T3 or .81 T4 would be insanely responsive (like 1 bar below ~2.8k) and should still be good for over 350whp at 1bar. That turbo is a bit small for a 3.3l but, for those that like low-end response it would work well.

greglepore 01-11-2007 04:21 AM

Tony, thanks for the imput.

Porschefile, I'm running a low boost Protomotive setup on a 3.2. No internal mods, so I'm stuck w/ .5 bar or .7 intercooled. It currently runs an obsolete GN style turbo, which is very laggy.

930gt-40r 01-11-2007 07:27 AM

Porschefile, the only reason I am going with the 1.06 is because the motor is 9.5:1 3.4L and I really want this thing to pull to the redline (going to spin her to 7500). I dont think she will have too much problem spooling, I am hoping for 550-600 to the wheels and with the 35R that is right at the sweet spot, 22-26 psi. But you are right, I could have done the .82 or .83 housing and had a hell of a lot of bottom end. I dont know, we will just have to see when she is done, I will keep everyone posted.

YermanCars 01-11-2007 08:19 AM

Here is the turbo I had, than sold.
http://forums.pelicanparts.com/porsche-911-used-parts-sale-wanted/310158-3-2-turbo-gt37-88-a.html

Notice the low a/r on the hot and cold side. The new turbo I have, has .58 and .60 ar.

Jim2 01-11-2007 09:12 AM

Question. Does GT series use conventional Turbonetics compressor and turbine configurations? They are not very forthcoming with compressor maps.

They appear to be prepackaged combinations of regular stock parts from turbonetics... mostly ball bearing of course.

WERK I 01-11-2007 09:27 AM

Bumping to subscribe to thread.
Thanks for the great info thus far guys!

Background:
I'm looking into Garretts for the 930. I currently have a K27-7006, on B&B headers, CIS, WebCam SC grind, Kokeln IC, twinplug crankfire, C2 turbo pistons/cylinders.
The 7006 is running out of breath after 4500RPM. So I'm looking for more air volume without sacrificing too much of the low end response of the 7006 around 2800RPM.

Porschefile 01-11-2007 10:18 AM

Quote:

Originally posted by 930gt-40r
Porschefile, the only reason I am going with the 1.06 is because the motor is 9.5:1 3.4L and I really want this thing to pull to the redline (going to spin her to 7500). I dont think she will have too much problem spooling, I am hoping for 550-600 to the wheels and with the 35R that is right at the sweet spot, 22-26 psi. But you are right, I could have done the .82 or .83 housing and had a hell of a lot of bottom end. I dont know, we will just have to see when she is done, I will keep everyone posted.
Hmm, honestly I really don't think a 1.06 is necessary until you get somewhere above ~4.0L as with a smaller .82 on even a 3.4l, there won't be nearly enough backpressure or lack of exhaust flow on the hotside to necessitate the use of a larger hotside. Are you sticking with the 9.5:1 CR? If so, I hope you plan on using race gas! ;) If you really want flow, go with a .81 T4. A T4 hotside is quite a bit larger and will overall flow better. I'm running a .81 T4 hotside on my crappy 60-1 w/ a P-trim turbine. The 60-1 is ancient stuff, though w/ 964 cams my car pulls hard to 7k rpm. With a 35r compressor wheel and that T4 hotside, you will have more than enough flow and reduced backpressure that it will definitely pull hard to ~7.5k

Greglepore, with a stock CR motor, I really wouldn't waste the money converting to a GT series turbo. I'm not sure what size turbo you have on your setup. Do you have a T3 or T4 exhaust flange? I'd highly recommend checking out a turbo from Precision's "SC" series Precision Turbo I believe someone was running one on Pelican and they were reporting some crazy quick spool. Anyways, Precision's SC series turbos are usually only ~$800-850 new and I believe you can even request a T4 hotside. Ultimately, you're going to be limited on total power by your CR, and I doubt if you could make much more than ~350whp.

Jim2, Garrett's GT series doesn't use anything related to Turbonetics. Turbonetics is a completely different company. Here's a link to their website. On their website they have all of the info and compressor/turbine maps you could want. ;) Most of the stuff they are using is fairly conventional. Most of the turbos have your typical T25, T3, or T4 flanges. There are some unique and cool things about them though, such as divided exhaust housings like This which help a turbo spool up more quickly. Other than that, the wheels have been redesigned using the latest stuff like advanced CFD software, so they are much more aerodynamically efficient. On top of that, I'm not sure exactly what processes they used though the GT series wheels are lighter than their equivalent T series counterparts, yet they are stronger. This equates to quicker spool and higher shaft rpm capability, meaning they can more easily withstand high boost pressures.

Frank@AMS 01-11-2007 10:38 AM

GT series turbos are made by Garret, Turbonectics does not use the GT series design.

I deal with the 35R's on a daily basis, as well as the 30, 37, and 42.

Unless you are going to use the full potential of the turbo, you can always step down a size.

930gt-40r, what type of power are you looking to put down, and I'm guessing that you want to spool around 3krpm? also what boost level will you be running?

930gt-40r 01-11-2007 03:09 PM

I dont know what Im going to put down, I do know that I just want it to be safe. I will tune it for whatever it could go to and then turn down the pressure a few pounds. I dont think much more than 550 which would be perfect with the 35r. On race gas will be a diffrent story, Ill probley get a s-load more because of the compression. I will just have to wait and see.

Frank@AMS 01-11-2007 03:17 PM

The GT35R will be maxed out right around 650 hp to the wheels however, I doubt you will be spooling at anything before 3300rpm.

930gt-40r 01-11-2007 03:28 PM

which is the equivalant to say a k-27. I cant remember my 27 spooling much before that either. Then again I havent driven a car with a k-27 in a long time.

WydRyd 01-11-2007 03:30 PM

Greg, I have a GT35R with a 0.78 A/R divided inlet housing on the GSF headers. Spool is amazing! I'm not after big top end HP, just quick street spooling ;)

For your application, I'd highly recommend a slightly smaller GT30R, rated at 500HP. That would be an awesome turbo for your application IMO, if you're specifically after a BB solution.

Frank@AMS 01-11-2007 03:39 PM

Merv,

While I do agree that a GT30R would spool up sooner, Garret does not make a T4 hot side GT30R. I can most likely get one specially machined, but at the same time, the turbo would really run out of breath in the top end.

When Yermancars converted to the smaller turbo he is running now, there was a small loss in power however, it spooled up so much sooner, and the power band expanded. The car felt quite a bit faster than before, even though its down a few horsepower from the GT40.

Also, the ball bearing turbos are nice, however, you will have to run and extra oil line through the water passages.
Standard journal bearing turbos, with updated housings, are a better way to go with the air cooled boxer motor in my opinion.

930gt-40r 01-11-2007 03:40 PM

Wyd, I just thought to ask you, how do you like the protomotive/ Bosch sys. in your car? I have been thinking about my next project and concluded that I want to do a 993 to turbo conversion and that protomotive setup is is what I would want. How does it drive? Do the use the factory maps and modify the signal for map sensing?

WydRyd 01-11-2007 03:46 PM

930gt-40r, the Proto setup works great and is a simple and cheap solution for aftermarket turbocharging a naturally aspirated engine. Otherwise you're up for serious $$$$ for aftermarket standalone EFI.

I only run the Proto Stage 3 CHIP and dual rate fuel pressure regulator on my existing setup, but eventually I will swap out my OEM ECU for the Proto Motronic MAP Sensing ECU, which is a more refined solution and still cheaper than an aftermarket Motec/Autronic setup. Just drops in place of the OEM ECU, uses existing loom and just requires a vacuum line run and a IAT & TPS sensor mounted to the throttle body.

For the 993's, Proto has a variety of TT conversions/kits, so get in contact with them. I'd say you can single turbo a 993, but lumbing might be easier with the twin setup, because of the twin distributor in the path of charge air pipe in a single turbo setup. Speak to Todd Knighton.

930gt-40r 01-11-2007 03:52 PM

That sounds mint, I would just go for the pressure sensing first. Your right, twins may be more managable. I am wondering if it would still work with obd 2 and still pass emissions. This project I speak of would not be happening for a long time, but it is still fun to think about.
What is the diff. between stage 3 and pressure sensing? is it just the use of a mass air and no tps mod?

WydRyd 01-11-2007 03:55 PM

Quote:

Originally posted by Frank@AMS
Merv,

While I do agree that a GT30R would spool up sooner, Garret does not make a T4 hot side GT30R. I can most likely get one specially machined, but at the same time, the turbo would really run out of breath in the top end.

When Yermancars converted to the smaller turbo he is running now, there was a small loss in power however, it spooled up so much sooner, and the power band expanded. The car felt quite a bit faster than before, even though its down a few horsepower from the GT40.

Also, the ball bearing turbos are nice, however, you will have to run and extra oil line through the water passages.
Standard journal bearing turbos, with updated housings, are a better way to go with the air cooled boxer motor in my opinion.

Frank, Greg's original posts suggested he was after a LOW BOOST setup on a naturally aspirated motor, so I'd assume he's looking at running only about 0.7bar. The GT30R would suit that application nicely and not run out of breathe up top. It's rated to 500HP and a 0.7bar bolt on setup on a 3.2 would yield ~400HP. BTDT :)

Also, I run my GT35R oil cooled only. I left the water passages open. I use a -3AN oil feed, NO RESTRICTOR (as advised by Garrett dealer) and drain to the oil sump plug. I've had no problems to date, however, it's only been on my car for a couple months now. Time will tell. The key to making these live is to exercise proper cool-down procedure and to keep the oil clean and fresh.

The idle oil pressure on 911 engines is relatively low (~1.5bar) compared to Japanese cars, which is why the Garrett dealer suggested no restrictor is used. Also, oil pressure does not exceed 70psi under load, so that's another reason why they suggested no restrictor.

The turbo will let you know if a restrictor is required or not as it'd start leaking oil and smoking. Mine's been fine :cool:

Frank@AMS 01-11-2007 04:03 PM

Merv,

The coolant passages are used to cool the bearings on the turbo, Id
personally recommend at least running oil through those. As far as the GT30 being rated to 500HP, boost threshold on the turbo becomes far more apparent on a high liter car. For example, here at our shop we can run 30psi through the GT30R, at that point it stops making power on our 2.0 liter motors. On a Porsche motor, the T3 hotside would be way to restrictive even at 1.0bar of boost. There are just too many liters to fill will such a small cfm rating.

WydRyd 01-11-2007 04:07 PM

Quote:

Originally posted by 930gt-40r
What is the diff. between stage 3 and pressure sensing? is it just the use of a mass air and no tps mod?
Stage3 is just the engine build spec and associated power level. Has nothing to do with the type of engine management solution used.

My Stage3 still uses the OEM BOSCH AFM setup, which works OK, but I'd rather have the MAP Sensing setup in a heart-beat. At ~USD$2.2k, it's a great deal (compared to Motec/Autronic setup etc).

Their MAP ECU comes preprogrammed with a map to get you running asap. Apparently it's pretty accurate and may need minor adjustments for your application. To get things sport on, Todd will re-program your maps for you and send the binary image to you via e-mail for you to burn on EPROM and try in your ECU. All you do is supply him AFR's plotted against boost/load/rpm and he'll do the fine adjustments as deemed necessary.

A few guys over on Rennlist run the Proto TT setup with MAP Sensing ECU and they have only positive things to say about it! I can't wait to get it myself :( People typically say "the car is totally transformed and it feels like the engine has been swapped out with a BIG naturally aspirated motor".

WydRyd 01-11-2007 04:13 PM

Quote:

Originally posted by Frank@AMS
Merv,

The coolant passages are used to cool the bearings on the turbo, Id
personally recommend at least running oil through those. As far as the GT30 being rated to 500HP, boost threshold on the turbo becomes far more apparent on a high liter car. For example, here at our shop we can run 30psi through the GT30R, at that point it stops making power on our 2.0 liter motors. On a Porsche motor, the T3 hotside would be way to restrictive even at 1.0bar of boost. There are just too many liters to fill will such a small cfm rating.

Frank, I also have heard of people running oil through the water passages, but these are for track cars which see sustained peak loads and boost. For a street car (like mine) which sees occassional full boost, I think I'm quite safe to leave those passages open. If I were building a car for street and track, I'd definitely run oil through those passages. Good point!

BTW, don't the K27-7200, K27-HFS & HF2 turbos run a T3 hotside?

Frank@AMS 01-11-2007 04:20 PM

Merv,

The K27's do run a T3 hotside but, notice how all the 930 guys always complain how power drops off in the upper rpms ;)

WydRyd 01-11-2007 04:26 PM

I thought that was the result of the compressor not being very efficient up top? Interesting!

Anyway, I only run my baby to 1.1-1.15bar MAX, and the GT35R I have maintains HP all the way to redline. I'm happy :cool:

Porschefile 01-11-2007 05:00 PM

Quote:

Originally posted by WydRyd
I thought that was the result of the compressor not being very efficient up top? Interesting!

Anyway, I only run my baby to 1.1-1.15bar MAX, and the GT35R I have maintains HP all the way to redline. I'm happy :cool:

Properly sizing the turbine and hotside seems to be a topic that is often overlooked.

WydRyd 01-11-2007 05:15 PM

It's also interesting that all the aftermarket header manufacturers build their headers with T3 flanges (GHL, B&B, GSF, Schnell etc), except for fabricators like Marco Menzie and Bob Holcomb. I guess all the off-the-shelf stuff are design to be as bolt-on as possible, whereas MM & BH build their headers for big HP aftermarket applications.

I agree though... for a 3.3, 0.81/0.82 A/R seems to be the best sizing for good power and response. I went with 0.78 A/R because I wanted the divided inlet turbine housing to bolt right onto the GSF headers. Divided inlet housings are suppose to offer slightly improved spool-up too, I've read.

930gt-40r 01-11-2007 09:09 PM

I wanted to do the whole bosch injection sys with pressure sensing, but after buying the plenum, harness, and software it would come out to almost 5 grand which is right know out of my reach. I would love to do it but I guess my accel dfi will have to due for now. Im sure it could be tuned to run close to the bosch/protomotive setup, but there is something about having the stock porsche designed part-throttle curves and map sensing that makes my pulse raise.

Porschefile 01-12-2007 12:05 AM

Quote:

Originally posted by 930gt-40r
I wanted to do the whole bosch injection sys with pressure sensing, but after buying the plenum, harness, and software it would come out to almost 5 grand which is right know out of my reach. I would love to do it but I guess my accel dfi will have to due for now. Im sure it could be tuned to run close to the bosch/protomotive setup, but there is something about having the stock porsche designed part-throttle curves and map sensing that makes my pulse raise.
With a decent, modern aftermarket EMS, you can tune ALL engine parameters for these motors (and pretty much any older motor/setup for that matter) to only run better than stock by someone that truly knows what they are doing. Aftermarket EMS gets a bad wrap because it can be very complicated to deal with and very easy to get wrong. Most modern aftermarket EMS' (except maybe SDS or some of the really simplistic ones) have superior software and superior hardware componentry compared to the stock Motronic, plus lots of advanced features that will generally increase efficiency and performance.

Wydryd, divided housings do definitely aid in spoolup. It's really fairly simple actually. You are dividing the total surface area and adding a slight restriction, which has the effect of increasing exhaust flow velocity. Quicker velocity means quicker spooling. It's much the same basic concept that people use when porting heads. Also, depending on the exact setup, with divided housings you can also take advantage of pulse tuning by grouping the proper cylinder pulses into 2 separate runners that stay separate all the way to the exhaust housing. To give a general example, all I4's have a 1-3-4-2 firing order. You'd group cylinders 1&3 into one runner and 4&2 into another runner and keep them separate all the way to the turbo. Generally, from what I've seen this tends to have more of an effect in shorter manifold designs like you'd find on a compact I4. On F6's, our headers are generally a decent amount longer so I doubt if you'd notice much effect if any. Running the divided housing alone is all that would really be necessary.

Porschefile 01-17-2007 03:45 PM

Wydryd, if you don't mind me asking, I was curious where your boost threshold is and what rpm you are seeing full boost at? I'm thinking of doing a Gt4088r w/ a .85 T4 hotside. It's the same compressor as a 35r, basically just an anti-surge housing and larger turbine/hotside than the 35r. Judging by what I've seen on other similar displacement motors (3-3.5l i6's, v6's, etc) I'm thinking I should see 1 bar around ~3.8-4k rpm which is good enough for me.

Frank@AMS 01-17-2007 04:00 PM

Porschefile

If you already running a T4 hot side, there is no need to run a .85 hot side. You would easily be able to run somewhere around a .65 without seeing any drop off in higher rpm efficiency while gaining spool time.

YermanCars 01-17-2007 04:05 PM

Quote:

Originally posted by Porschefile
Wydryd, if you don't mind me asking, I was curious where your boost threshold is and what rpm you are seeing full boost at? I'm thinking of doing a Gt4088r w/ a .85 T4 hotside. It's the same compressor as a 35r, basically just an anti-surge housing and larger turbine/hotside than the 35r. Judging by what I've seen on other similar displacement motors (3-3.5l i6's, v6's, etc) I'm thinking I should see 1 bar around ~3.8-4k rpm which is good enough for me.

What kind of power are you looking for.

Porschefile 01-17-2007 05:33 PM

I'm running a .81 T4 hotside at the moment. Frank, the thing is the 40r .85 hotside is a twin scroll, so that will aid spool a bit. Also, from what I understand there are some internal differences (other than the twin scroll setup) that make the .85 GT housing different from a regular .81 T4 housing. Since the 40r comes with the hotside, I might as well use it. Ultimately I'd like to break ~600whp. Judging by what I've seen, for that size of compressor/turbine, a .68 housing is going to be pretty restrictive around the 600whp level, and I'd like to accomplish that without running too much boost. A gt40r is similar in size to a T4 T66, so it's not really that large of a turbo for a 3.4l. It would make reaching 600whp much easier and I'd be able to accomplish it at lower boost while still not being that laggy.

YermanCars 01-17-2007 06:25 PM

Modified gt37 @ 16 psi, running the afm and motronics. Heat soaked intercooler, could of made 25rwhp more.

Frank is dynoing the car.

http://media.ams-evo8.com/videos/amsmisc/PorscheDynoRun.wmv

600rwhp no problem w/ 20psi, maybe 18psi w/ a good tune, full spool @ 3600 rpms.

WydRyd 01-17-2007 08:46 PM

Quote:

Originally posted by Porschefile
Wydryd, if you don't mind me asking, I was curious where your boost threshold is and what rpm you are seeing full boost at?
Porschefile, if I punch the throttle, I can get full boost at ~3K... it spools very quick, just the way I like it. It may have to do with the 0.78 A/R divided inlet housing, not sure? I'm sure the bigger A/R housings would result in more top end HP, but I wanted it purely for street as my car is my daily driver, so I wanted something snappy on the road and that's what the GT35R delivered. I'm pleased. Once I sort out my twin plugging, it'd be even more responsive ;)

I've heard reports of the GT35R spooling up as low as 2700rpm on a finely tuned motor with aftermarket engine management, pressure sensing, twin plugs etc...

Porschefile 01-18-2007 12:14 AM

Quote:

Originally posted by WydRyd
Porschefile, if I punch the throttle, I can get full boost at ~3K... it spools very quick, just the way I like it. It may have to do with the 0.78 A/R divided inlet housing, not sure? I'm sure the bigger A/R housings would result in more top end HP, but I wanted it purely for street as my car is my daily driver, so I wanted something snappy on the road and that's what the GT35R delivered. I'm pleased. Once I sort out my twin plugging, it'd be even more responsive ;)

I've heard reports of the GT35R spooling up as low as 2700rpm on a finely tuned motor with aftermarket engine management, pressure sensing, twin plugs etc...

Twin scroll housings do make turbos spool more quickly. Ultimately it's really simplistic in that they divide the total surface area of the inlet which has the effect of increasing airflow velocity and increased velocity = quicker spool. Depending on the exact turbo setup, you can couple this with pulse tuning to improve spool as well. All that means is you'd combine the proper exhaust runners to form two separate runners that stay completely separate all the way to the exhaust housing. For example, on a i4 you'd mate #1 and #3 together and you'd also group #2 and #4 together, though you'd keep each pair separate from the other pair. I hope that makes sense. I have some suspicions that simply running a divided turbo flange alone should provide 80-90% or more of the benefits of increased spool on most setups. Maybe on a motor with much shorter runners, like the typical i4 turbo setup, you might see benefits from pulse tuning a twin scroll setup (due to possible elimination of exhaust flow turbulence) though motors like 930's have decently long runners so I'm wondering if the divided flange alone is just "good enough" if you catch my drift. I'm sure Frank has much more hands on experience in this arena, so maybe he might be able to say for sure.

Personally, I'd say technically .78 divided T3 housing is a bit small considering your displacement, and a T4 housing should have some nice improvements in power however it sounds like it works perfect for your needs, and in the end that's all that really matters. Personally, I like a higher boost threshold of say anywhere around 3.5-4.5k for full boost. I don't mind the loss of some off-boost performance, and I prefer a powerband that flows plenty up top and holds torque/hp at least above 6-6.5k rpm before dropping off. I'll be going with Gt2 Evo cams and stiffer springs to support ~7.5-8k rpm so I don't mind a bit more lag. ;) The increased rpm is part of the reason I'm considering a larger turbo like the Gt4088r or possibly even the new Gt4094r (kind of a 40r/42r hybrid, about the size of a T4 T66). Either one of those should make full boost in the 3.8-4.5k range and no later, though they would both allow me to reach 600whp with quite a bit less boost than a 35r.

al clark 01-18-2007 04:37 AM

Could some one tell me if i would see much power increase on a stock 3.3 by going from a stock KKK27 to a hybred KKK28 with a KKK27 hot side KKK28 center section and KKK29 compressor side? Also would it be a bolt on or would mod.have to be made to install on 92 turbo? THANKS


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