Please help with Turbo Selection

[lr172]

I had started a different thread on my conversion, but it seems to have taken a different direction.

I am planning a 3.2 Turbo conversion and looking for some guidance on turbo selection. I haver received some help and have done quite a bit of research, but I am struggling with the details and understanding how they all inter-relate.

I will be limiting my boost to a maximum of .7 bar (starting with .5 bar), therefore, should be under 400 HP. I plan to use the stock headers. I am open to using any type of flange and will consider a ball bearing, but would like to stay with a standard journal to avoid longevity issues by not having water cooling. This is a street car and therefore, my priority is a quick spool up with strong mid-range. I am willing to sacrcifice a little of the top end to achieve this goal. I am not worried about growth, as my 9.3:1 CR will keep me from going much beyond this level.

Given that I won't be pull that much boost from the unit, my thought was to stay on the smaller side to maximize the low end. However, I am afraid of choking the exhaust. I was originally thinking .63 AR on the exhaust, but read some posts indicating this is too small on T3 turbo to support 3.2 liters.

[EDIT:] I should add that I have done a fair bit of work in evaluating compressor maps. The following all fit my application well:

GT3071 (better suited to my .5 bar config than .7 bar config)
GT3076
T04E (60 Trim)

Where I am hung up is on the hot side. I don't know what AR or trim will spool this up quickly without choking too much.

Does anyone have recommendations for a turbo that meets these objectives or some guidance in selecting specs for a turbo?

Thanks in advance for your help.

Larry

[pkracer21j]

look up compturbo I'm using their CT61 creamic triple ball bearing. no reliability issues and fantastic spool up. plus they give you a one year no fault warrenty and have excellent customer service. no affiliation, im just extremely pleased with my turbo.

[RarlyL8]

I've handled many 3.2L Carrera Turbo conversions using stock 930 exhaust systems. The turbo I recommend and supply is the K27S. It is a perfect match for those who desire quick spool and moderate HP output. Bolts on to the stock J-pipe and uses stock 930 oiling. Plug and play with stock parts.

[sjf911]

From my research, the K27 compressor seemed most efficient at these low boost applications. Most of the other choices were really optimized for high pressure applications. IIRC, the T04E was the closest in compressor efficiency at those pressures and flows. The other issue that that I considered was bearing cooling. The ball bearing turbos are all jacketed for water cooling and are being run in our applications without additional cooling. There is significantly less oil flow to the ball bearings than the journal bearings so it would appear that you significantly reduce cooling with the BB type without adding water. How this effects durability is not documented. I did consider adding oil cooling to the water jacket of a BB but I really doubt that the stock oil pump is up to the task without severely restricting inflow which would obviously reduce cooling. OTOH, the reduced oil flow of a BB turbo has less oil scavenge issues for our stock oil pumps.

[fredmeister]

you could always install a separate oil scavenge pump electrically driven if the stock porsche cam driven pump was not enuff. oil does not cool near as efficently as water, but it is better than nothing to the center section.

[lr172]

It does seem that the K27S is providing good results in this application. My only concern is cost. This turbo is a bit more expensive than my other alternatives.

Does anyone have experience with a T3/T04E with a 60 trim compressor wheel and .63AR? These are inexpensive to purchase new (1/2 of K27 price) and I also have an option to buy one used. My application fits well on the compressor map for this turbo, but I have no real data points for the hot side and how it will perform (i.e. spool up, ability to breath up top, etc.).

Thanks again for your contributions.

Larry

[sjf911]

Originally Posted by lr172

It does seem that the K27S is providing good results in this application. My only concern is cost. This turbo is a bit more expensive than my other alternatives.

Does anyone have experience with a T3/T04E with a 60 trim compressor wheel and .63AR? These are inexpensive to purchase new (1/2 of K27 price) and I also have an option to buy one used. My application fits well on the compressor map for this turbo, but I have no real data points for the hot side and how it will perform (i.e. spool up, ability to breath up top, etc.).

Thanks again for your contributions.

Larry

LOL, I have a T3/T40E 60 sitting on the shelf brand new, never used but with a .83 hotside and a twin scroll turbine housing. I also have a set of used OBX headers (no heat) that fit the twin scroll housing. You can have them really cheap if you want, $400 total for both.

[kenikh]

Main issue with big Garrett's is they prefer water cooling - this is what they are designed for. They spool fast and make great power, especially the twin scrolls. But therein lies the bugaboos:

- You should really add a small radiator and water pump for these turbos.
- Twin scroll turbos need a true equal length exhaust that segregates the exhaust gas streams from the two cylinder banks all the way up to the turbo. If you don't, you lose the twin scroll benefits gained from stealing efficiency from the evenly timed exhaust pulses.

Doinf it right requires a lot of work and cost that removes the cost benefit of using a "less expensive" turbo.

[lr172]

Kenick, one of my attractions to the T3/T40E was that it was a std. journal bearing and therefore oil cooled. Did I miss something?

SJF911, sending you a PM on the offer. Is the .83 too big to use with the stock exhaust? I may consider your offer and fabricate heat. on these headers.

Thanks for the input guys. I appreciate it.

[kenikh]

I was going off of the latest catalog. Nothing in a 40 oil cooled that I could see.

[964 T #304]

look@ the Turbonetics GTK series

[kenikh]

Turbonetics makes great stuff, but they aren't budget parts, that's for sure.

[x98boardwell]

Sent you a PM.

Thanks,
Bryan

[911st]

Check with spence88mph. He has a very successful conversion using a GT30R, OBX headers, and a custom passenger side exit RarlyL8 muffler. He is very happy with his set up.

I would concider a K27-7200 with your goal of early boost (apx 380fwhp limit).

However, I suspect a K27-7006 with a larger hot side (same compressor, apx 400hp limit) would be more to my liking as it has a little bigger hot side for better efficiency but a bit later boost on set. With high compression I suspect a larger less restriction hot side with and effecent compressor wheel migh make some sense.

I like fast and hard boost so I am not a big fan of the HF's (big compressor wheels and small turbines) but they are good turbos, may love them, and they are very drivable as boost comes on early and builds in a more linear manner.

Before I sold my C2Turbo I had a Turbonetics 60-1 Turbo that I did not install but others w 3.3T's very much liked as it made more HP than the k27-7200 and had faster spool.

Just my opinion.

Good luck.