special tool

Let's get them to turn that boost up!!!

Duke

First of all, I can't confirm that it has 1.4 bar at 3400 rpm. Judging by the charts it looks like peak boost hits at 4000 rpm which sounds more likely.

2.0 bar and it would be pretty fast Probably won't be able to do it with that cam though.

Cant't compare to Puppan's car since we never boosted more than 0.8 bar. Had problems with the boost solenoid.

Porschefile

First of all, there is no such thing as a PT-65 from Precision Turbo. There is a PT-64 and PT-66. Either way, those are full sized T4's. There is no physical way a full sized T4 with that size of compressor wheel would ever come on boost at ~1900rpm on a 2.5l. Even if it was a 3.0L, that's still pretty much impossible. Sorry, not gonna happen. 4cylinders just do not generate enough exhaust volume at those lower rpm levels to generate enough axial torque to drive such large wheels.

The Gt35r is a 61mm compressor wheel (82mm exducer). T04 compressor wheels around the 66mm+ (inducer) range are considerably larger in overall size and flow capacity as they generally have larger trims and larger exducer sizes than something like a Gt35r or Gt30r. With a full sized T4, even if you managed to figure out some way to spool one up so low in the rpm on a 2.5l, you would have some serious surge issues. That's just the physical reality of the matter. A full sized T4 is generally going to make full boost (lets say ~1bar) in the ~4k+ range on a 2.5l. Regardless of what some retailers/builders would have you believe, there is no magic "pixy dust" things that you can do to make turbos of this size spool up insanely low in the rpm. Sure, you can make positive boost pressure of maybe a couple psi though making say ~1+bar of boost sub 3000rpm with a 61mm+ 600+rwhp turbo is NOT GOING TO HAPPEN, PERIOD! Surge is a real issue with larger turbos like this and there is no "cheat codes" you can use to obtain quick low-rpm spool, eliminate surge, and still make a high ~600+rwhp number. You can choose 2 out of the 3 but not all 3. There are plenty of things you can do to acheive 2 out of those 3 categories (quick spool, eliminate surge, high hp) such as using a compressor surge housing, using a smaller and more restrictive exhaust housing as well as a smaller turbine, etc. Doing some of these things to acheive quicker spool and eliminate surge are also at the expense of efficiency and are counterproductive to making hp meaning they will limit your overall hp. Sorry to go off on a bit of a tangent, though I think these things need to be said and discussed. I see some around here suggesting otherwise about some of these things, and most of the time without any substantiating evidence, physical proof, or scientific explanations supporting it.

We're getting pretty OT guys. I hate to say it but, lets try to stick to the thread subject. I wanted this to be an informative post about the gt35r specifically. Hehe, 8 pages and I've only managed to post a few pics! Sorry, I'll update the thread soon. My 951 is at a friend's workshop, and because of my job I haven't been able to find the time, lately, to make it over there and start the install.

Markus951

The reason why I brought it up was because I found one similar combination fo turbo and displacement. (2.5 liter with similar turbo). I find it really interesting that people are pushing the limits of stock engines.. Unfourtunately I broke mine before I even reached the maximum of my setup..

Markus

special tool

Yes Markus, I know how you feel.
A lot of track guy think it easy to make a "glory" run on a dyno. They don't know (lack of experience) that its VERY hard on an egine to push its ultimate limits, ESPECIALLY where there is no cooling airflow.

My engine could run for 24 hour enduro on track at a measly 400 HP - that would be about 13 psi for me.

Porschefile

Just thought I'd do a quick update. Over this weekend I messed around with the 35r setup to see where there might be any fitment issues, considering I am using the 4" T04S compressor housing. Sorry I don't have any pics. I might be able to get some next weekend if anyone really wants me to. Here's the bad news, GT series turbos with the 4" T04S housing and with the SFR setup (modified center section and a ~6mm spacer for the turbo mount) will NOT fit without doing an AC delete. Keep in mind, I am talking about "perfect" fitment which would entail being able to run a 3-4" intake pipe without any hassles. An AC delete would position the alternator far enough out of the way that there wouldn't be any issue. Now, if someone doesn't mind a less than optimal and compromised setup (and they want to retain the AC), there is just enough room that you could still run the 4" housing, remove the plastic cover from the back of the alternator, and run a reducer coupler probably around a 4" to 3" or smaller however IMO this defeats the purpose of the 4" housing and is counterproductive for my purpose (high hp, improved top-end flow, etc). The T04E 3" housing would fit quite a bit better and would have barely any fitment issue (might be necessary to use a slight reducer coupler), even with the alternator in the stock position. Personally, in my experience the larger T04S compressor housing is really not going to be necessary to use except for those that are going for big power.

For my specific setup, I've figured out the easiest way to retain the A/C but I have a custom short runner intake that frees up quite a bit of room around the turbo, so my example is probably not going to work for everyone. With my setup, I am probably going to have a ~ 3/4" or 1" spacer machined for the mount to use instead of the SFR spacer. This will position the turbo up high enough to clear the alternator, and then it will only be necessary to add 1" the top of the cat pipe so that it will still reach the downpipe. However, I still need to test this method with the stock intake manifold to see if this will cause any fitment issues on that side. I have a sneaking suspicion that the turbo would sit too high for the intake to fit. Although I've figured out what will work for my setup, I am still going to examine what is necessary to make this setup fit with the stock intake and without doing an a/c delete for those that are considering a similar setup but want to retain most of the stock components. At this point it looks like a reducer and removing the alternator shroud should be enough to get the job done. In the next few weeks I'll do some more work with this and post updates with pics to further illustrate what I'm talking about. Ultimately, I'd recommend that for those considering making less than say 450-500+whp, just bypass these issues entirely and use the 3" T04E housing. The T04S will really just be more trouble than it's worth for anything except a high hp setup. Also, for anything over 400whp I would highly recommend going with a .82a/r exhaust housing (assuming the SFR setup, in a KKK a #10 would be similar sized). Although spool will come in a few hundred rpm later than with a .63a/r, at those boost/power levels the turbo would be significantly more efficient with a .82 which IMO would be preferrable to a few hundred rpm sooner spool.

evil 944t

Why don't you just use a smaller alternator?

Porschefile

Because I'm lazy and I just replaced this alternator. Seriously though, I've considered it, and it definitely is one solution to the problem. Since I have the room above and around the turbo as a result of the different intake, it would be far easier to use a taller turbo mount spacer and modify the cat pipe. I have access to a MIG, TIG, plasma cutter, lathe, and tons of other stuff so fabrication is no big deal. Not to mention, I'm seriously leaning towards modding the downpipe and crossover to reposition the wastegate in the engine bay (it would be located right behind the turbo) similar to the custom setup Performance Developments was doing on some 951 motor and that someone posted in this section awhile back. Here's the link: website I'm all about efficiency and to me this is more of an efficient setup provided there is enough room (in my case there is).

reno808

GOD matching turbo had so much knowledge. TO bad

333pg333

Just thought I'd dig up an old thread. Wonder what happened to tedesco's car? Duke where's your car up to? Who has a GT35 on their cars. What happened to the Swedish cars with the big turbo on the header side up front. I have a friend about to do a similar installation on a 968 and wondered on those possible problems. I'm sorry that Travis never finished this as he did things passionately and in detail.

Duke

I got 2 951 engines with GT35's in the garage right now hehe...

No real data yet though. On the 2.5 boost hit HARD at around 3700-3800 rpm with a 0.82 a/r turbine. I think 99% of the people here would be surprised how well those big GTBB turbos work.

333pg333

So with a 3.0L w good VE and shorter gearing that should be ideal then?

Duke

Absolutely, a perfect match for a 3.0l IMHO.
Personally I'm not a fan of shorter gearing on a 3 liter though.

HansB

If you track it you would be. Attainable top speed is around 250 km/h.

Chris White

Depends on the track. Short gearing dosen't work well at the Glen...a decent 3.0 should see 265kph or more.