GT35R turbo for 3.4L?
 

Looking for recommendation on Garrett GT35 (or other) for my 3.4L, EFI Porsche 930 motor...

Engine was newly built with all the good stuff: 8:1 compression, 3.2 intake, Motec ECU, 996 Cams and custom headers (w/T4 flange), and LARGE SPA Turbo (don't ask..). Car has G50 tranny.

With current set-up boost doesn't kick in until 4000+ RPM and pulls HARD to max boost at 6500. I would like more torque/power at lower RPM's w/o restricting too much air flow at upper end.

Can someone tell me their experience with the Garrett GT35 (or equivalent)? Boost kick-in RPM? Reliability? Compressor/Turbine size used?


Much appreciated..

Frankhttp://forums.pelicanparts.com/uploa...1319597078.jpg

A gt35r with a 0.82 hot housing will get you max boost AT LEAST 1k rpm quicker without a doubt, and have plenty of puff up top too. Perhaps even try the new gen GTX-R with the 11 blade impellers.

911TT33....thanks for reply. Quickly a few... should I consider lower in A/R (.60ish)? Do you know if oil cooling only will damage the turbo? Will T4 (I have T4) vs. T3 flange impact spool significantly?

Hopefully - I can this can be close to "drop-in" install.

Much appreciated!!

Frank

A 0.63 hot side is too small and will choke the motor.

If this is a street car, leaving a GT turbo oil cooled is fine. If you are taking to the track, then consider a water cooling solution too for longevity. You could even run oil through the water ports too. Seen that done too.

If you want a drop in install, stick to a T3 turbine housing, otherwise you will need to modify your headers with a T4 flange. Not worth the expense IMHO.

Also, get one with a 3" compressor inlet to make intake plumbing easier too.

For exhaust discharge, I'm a huge fan of V-Band flanges... Makes R&R so much easier! ;)

Thanks!

ps. I have T4 flange and V-band discharge (see pic) - so agreed.

Twin .63's on the other hand will let it boost into oblivion....63 is what is on my motor.

Lol, but twins is not exactly a drop in upgrade now is it? ;)

Forte500, you will also need to modify that oil drip tank with a new oil inlet flange. It's not the same as the KKK flange I believe. Worth getting some measurements of that flange to confirm ;)

How much power are you looking for?

Will you track this car, or is it purely to terrorize the streets?

This is strictly a street car to terrorize all the hedgefund guys in my area who "suddenly" thought it was cool to have a fast car..lol

Seriously, I would like an honest 400 RWH (.9 bar max) with better response off the line and some decent legs at the top. With a G50, Motec and 8:1 compression - this car should respond nicely and be reliable.

I hear the GT35 is best of both worlds, although some old-schoolers/tuners preach a hybrid K27 or Tial is a better option. My current SPA turbo (leftover from another build) seems better suited for racing (i.e. high revs). Not practical for the street.

What's your set-up?

ps. thanks for quick response....helpful

I ran a single GT35R for years.... Loved it! The tinkerer in me wanted to try something different, so I'm in the process of doing a twin turbo conversion. It's a loooong slippery slope when you go down this route. In hindsight, I should have stayed with the single GT setup and just enjoyed terrorizing ricers and bikies :D

Why limit boost to 0.9 bar? If you have fully programmable engine management and an efficient intercooler, no reason why you can't run more boost... Within safety limits that is :)

I use to run 1.2 bar in my car for years before taking it off the road for the TT conversion ;)

4000RPM in 4th or 1st?

At 8 to 1 compression, is it safe to run more than 0.9 bar on pump gas? Even with fuel injection and ignition timing control the dynamic compression ratio is getting up there for an air cooled engine.
just my thoughts...

That's why I said "within safety limits". Keep an eye on A/F ratios and EGT temps when tuning for more boost. Don't just increase blindly without knowing what these readings are like.

I prefer a lower C/R and more boost... The rush is so addictive! :D

The K27 hybrids and high flows will easily support 400WHP and drop your boost 1000+rpm. They also bolt on and use the OEM oiling system.

Again, nothing to compare to but before I change turbos my tuner is advising me to try .9Bar spring (now that motor is broken in) and see if spool up improves (theory the .5Bar is opening prematurely).....anyone know if this "significantly" improves spool/response??

With the G50, I don't get any boost in 1st until 4000RPM and by then it's time to shift. I watched the car closely during my morning drive and would say I hit the full boost (.5Bar) by 5200RPM in 2nd and 3rd gear....




p.s. Because of the high compression I will likely not exceed a .9 Bar spring, as well as install boost cut-off connected to Motec...in case of boost creep.

What type of waste gate are you running? OEM Porsche or aftermarket?

I highly recommend upgrading to a Tial waste gate for accurate boost regulation. You may have a faulty waste gate or vacuum leak somewhere :(

0.5 bar @ 5200 is shocking!

Frank,
What's the A/R on your current turbo?
If you're trying to avoid swapping turbos and modifying your exhaust manifold, you may give some thought to swapping a lower a/r turbine wheel in your existing turbo to see if that gives you the powerband you're looking for.

On swapping the wastegate spring - you may see a small improvement in spool, but I'd be surprised if it were more than a hundred or two rpms. Based on your comments, what I think you're after is a lower boost threshold, which should remain the same with just a spring change.

All things constant, you impact boost threshold with smaller ID exhaust manifold runners, smaller turbine A/R, less pressure drop from your intercooler... tuning can also have an impact on spool.

If you don't mind tossing the large turbo out, I'm a big fan of the ball bearing 35R. I drove a friend's 3.6L 964T a few weeks ago who had an upgraded KKK turbo... roughly the same output as my car, but came on boost noticeably later.
Best,
John

The turbo you have now must be way too big. Properly modified highflow K27 turbos are at 1bar by 2700rpm with the typical mods needed to produce 400+WHP. If boosting later than that something needs tweaked.

His headers have been built with a T4 flange, and his exhaust already has a V-Band flange.

To go to a K27, he'd have to rework his exhaust system back to a T3 flange and 4 bolt exhaust flange.

It'd be cheaper to drop in the 35R and just modify the drip tank flange to suit.

I've run a k27-7200, k27hf, and gt35R. In my personal experience with all those, I found the 35R to offer the best performance. Even a 30R would meet his 400RWHP goals and deliver very fast spool for street :cool:

Does anyone have any documented evidence that the GT spools faster than the K27?
I always read that some people feel it does.
Then I see Brian say he has not seen this to be the case.
I listen to what all you guys say. I have great respect for Brians knowledge.
Surely after all this time someone has done a documented test.

Keep in mind I have a 3.4L, carerra intake, 3.2 heads and as 911TT33 mentioned custom headers with T4 flange...wastegate is rebuilt/stock.....the current turbo has .96 A/R with 4" inlet and larger 70mm? compressor. Tyring to get best of both worlds (off-the-line kick w/o chocking the engine at top -end)

I tried to have the turbine housing swapped as JBurer suggested, but nothing was available for a SPA turbo (this came with the unfinished build I took on). I did have EverGreen turbo lighten up the shaft a bit - minor difference in perf.

I am leaning toward the GT35....my expecation is with a GT35 (and .9 Bar spring) I should be able to feel some boost in 1st gear (coming on at 2500RPM) and be able to easily break the tires free. Does this sound reasonable?

Thanks all!

0.96 is too big for our motors. No wonder its laggy as hell :(

Drop down to a 0.82 ball bearing unit and you'll see/feel the difference immediately... Guaranteed!

The GT35R comes standard with the 4" inlet 2.5" outlet compressor housing too, so your existing intake plumbing should mate up without any major mods. You can of course order them with a 3" inlet, 2" outlet too.

I'd be interested to know the diameter of the primaries on your custom headers. Too big, and that also affects spool :confused:

Btw, can you actually get a 0.9 bar spring for the OEM waste gates?

What Brian says.

I'm running a K27/HF with a Kokelyn/GHL's, and I make 370RWHP on CIS with the stock wastegate/spring. 6PSI boost @ 2400 RPM in 3rd, all in by at least 3000. It doesn't run out of boost at high RPM - just fuel.

With MOTEC, 3.2 intake and port-matched heads, you should be closer to 500RWHP than 400RWHP.

Okay, I am sold on the GT35, plus it won't require major changes or fabrication...I will measure the primary diameter......do you recommend the twin scroll/ports on the turbine? I could easily have a seperator welded on the flange as well if that helps.


RE: .9bar spring for OEM wastegate...tuner says he can get/make one and feels no need to swap out (i.e. TIAL, etc.).

I think that's a good call, given the current setup.

Pretty sure my GT35R is not a twin scroll. I believe that requires a divided manifold to work properly (?)

On boost control and wastegate springs - have you considered using the MoTeC to control boost and just leaving the 8psi spring in place?

If the merge collector on your headers is not divided, then there's no point going with a divided inlet turbine housing. Just go with an open inlet turbine housing.

Here's an example of a divided 930 manifold suitable for a divided inlet turbine housing. The idea is to isolate exhaust gas pulses from the left and right side of the motor all the way to the turbine wheel to maintain exhaust energy and maximize turbo response.

http://goingsuperfast.com/images/Porsche_930_header_NEW-5.JPG

No affiliation... Just showing an example :)

The primaries are 1.5" I.D. and secondaries approx 2" I.D....what were yours with the GT35 setup?

Yep, the same. Got any pics of the intercooler?

Did you get good boost in 1st? (i.e. able to spin wheels) :cool:http://forums.pelicanparts.com/uploa...1320028245.jpg
http://forums.pelicanparts.com/uploa...1320028342.jpg
http://forums.pelicanparts.com/uploa...1320028406.jpg

Frank,
Off topic, but mind if I ask what lift that is you have?
How tall are the ceilings?

Although I've yet to see a 911/930 run a divided/twin scroll and the results, it has to help. So, yes!

First, it is very easy to add a divider - I did on mine. So, I'd would buy the twin scroll housing and add the divider.

Second, that picture is NOT a divided flange. It is too thin-walled to survive the heat/stress. It is simply where the two secondary tubes were mated. Also, the supposed divider (which it is not) doesn't meet up flush with the flange. The energy would simply bypass back and forth and make probably next to no benefit.

Not trying to be pompous, just do not want people buying headers like that, putting on a twin-scroll turbo, and getting 0 benefit! :)

Interesting, that's the first kokeln IC I've seen used on a 3.2 intake manifold. Usually people go with a full length IC and relocate the AC condenser.

Btw, gorgeous looking car! You will be wrapped with the new performance of the GT turbo... It will feel like a different animal :D

Those headers look like Marco Menzies equal length headers!? You car was obviously built with big top end HP in mind.

Thanks for everyone's input....I ordered my GT35. This is great resource..intend to give back as I learn more about these cars and their limits.

Frank - any details on the lift to share?

Sure thing - I bought the lift in order to keep 3 cars in a 2 car garage. Fortunately, I have high ceilings 11ft (minimum required). I paid approx $1800 for the lift w/ramps and drip pans. Most important is a locking feature (ladder design) that is internal vs. a welded tab on the outside of the lift posts. There is no way for the lift to come down accidently! The standard lift (what I have) allows for a reg car/sedan up to 59" high and a sports car (less than 55" high) to fit under an 11ft garage. If your garage is higher, you may want to get the extended lift, which allows an SUV to fit under.

The lift came in several sections (heavy) but I was able to get most into place with a hand truck and then get a friend to help position the final track. It was pretty intuitive and a good thing, as the instructions were in Chinese and very poor diagrams :) It was delivered by a large box truck and typically requires a lift to transport from the truck to a residential garage. I paid the truck driver $100 and he agreed to help me move it in. Be sure to ask this when you buy it as some vendors will require you to have loading dock or lift.

It took about 3hrs to assemble and was very straightforward. It came with dollies to move the lift around and cement bolts to adhere to the garage floor. I chose not to drill-up my floor in case I decided to relocate the lift in the future. I did relocate the hydraulic motor at another corner so it wouldn't be in the walk-path in the garage. At first I tried it without a car on it - it felt flimsy and would rock considerably back n' forth …..with weight on it, it was rock-solid even w/o the bases bolted down. To be extra safe - I attached one side to the wall joists and now the lift doesn't rock even when the car is off.

I have to say...I love the set-up and it makes repairs a snap. Send me a PM if you want more details or know where I bought it.

FF

Nice, now make sure you give us all feedback on the end results SmileWavy

Do you have an intercooler temp gauge for your intake? It would be interesting to see how efficient that kokeln unit is. You can buy them from Davtron I think. They measure pre and post IC temps. :cool:

Sorry to hijack the thread but what rims do you have on that car? They are nice.

Fred

Measured last night and my garage ceilings are only 9.25 feet. Time to move :)

All my documentation went when I sold my car. Since it's EFI, you can get the GT to spool faster from idle (I proved it) but where the GT shines is in throttle response. The K27 center sections (bushings) can't spool up as fast as ball bearings and the vane technology that's on the GT. This is assuming you've tuned the motor well but to be fair, if you're looking for a dramatic difference, there isn't one. You get it down low quicker and in quick changes to throttle position.

I thought it was cool when I shut my motor off (it had a GT35R), the turbo would continue to spin for something like 45 seconds. The K27 stopped in 10 - 15 seconds from idle.

The ball-bearing vs. bushing turbo discussion is ALMOST as bad as one on which oil is better.

John, sorry to hear your ceilings are too low for the lift :)

Fredmeister - the rims are Kinesis K28 (w/ flat lips vs. the stepped). Fronts are 18 X 40 X 245, rear are 18 X 30 X 315. I would have never thought gold would look so nice, but as my wife says " they make the car". They really do in my opinion and resemble racing'/cup car wheels. Thanks...

I ran the GT35 on my 3.3L and now the 3.4L...shes a beast! Youll love it! I understand the twin scroll will give even better numbers. Enjoy