I have the larger XONA XR980 Turbos. These are a 3073 framed turbo (as in 73mm compressor). I replaced my UMW K16/997GT3RS Zero clearance turbos with the 3073s. Spool on the 3073s is faster and more progressive than my K16s and yet they have the ability to flow 2 bar of boost. You are really comparing modern ball bearing turbo technology to old school +20yr old stuff. Yes, the green springs are a must for proper operation with the cracking/open pressure set at 8.5/14 psi. I am going to be running these at a rather low 1.3 bar at which they are just loafing along. Justin and I have been working with Tial to get these set up properly for our use and I am in the process of getting these tuned on my 4.0 engine. All indications are that these will be fantastic units... Even at half throttle at 0.6 bar on the base tune and running with the N75 off, the car is frighteningly fast at this point.

 

Is your take that a bb 73mm compressor has the inertia characteristics of a journal bearing 68mm with the larger compressor offering better efficiency?

 

Nathan, I am no turbocharger expert, just going off initial driving impressions. It's hard for me to make an apples to apples comparison as I am going from a 3.8L engine with the Zero clearance K16 hybrids to a much larger displacement 4.05L engine with the XONAs. I'm sure the greater displacement play a major role in the fact that the turbos spool so quickly as the engine moves a ton of air right off idle and is very fast reving due to it's internal components.

 

When do you think you'll be in a position to share power numbers / dyno charts on your new build? I'm curious to see how it compares to you previous 3.8.

 

Hopefully in the next few weeks. I’m going to be logging and getting the files updated his week. As soon as the lambdas look right where we need them, Chris and I will get it on the local dyno where we check all the motors and where I dynoed both my 3.6 and 3.8 previously. I should be getting the 1st file revision back in the next day or so.

 

Pretty interesting video on the new turbos. Not sure if he is maybe talking about BHT's GT3 at one point?

 

Xona had these turbos on RIX's car not BHT's - he has Garrett GTX3582s. Here is his build thread and some info about these...

https://www.6speedonline.com/forums/...-121-a-20.html

 

Hey Pwdrhound, I just came across this thread. I have the XR980s on my 997 turbo. I am about to change the default springs in my pair as well since the measured wg pressure is way too high. I believe I have 1 bar springs but the wg reading is 20ish psi through my boost controller, which is too high considering my target is around 21-22psi. They are great turbos!

 

The XR980 turbochargers come from Tial with the MVI2.5 waste gates which contain the "blue" spring. With minimum preload set on these springs, the waste gates begins to crack at 14psi and is fully open at near 30psi. Based on our testing this provided poor throttle control and resulted in a light switch ON/OFF boost response. After extensive consultation with Tial, their recommendation for a set up running a larget of 19-20psi is to use the green 6.25psi springs. I am now using the green spring preloaded to start cracking at 8psi and fully open with 11mm of travel at 14psi. Running on WG springs alone with the N75 disconnected results in 0.6-0.7 bar of boost on my application. With the N75 connected at a 80-85% duty cycle I was seeing significant overboost of 1.5 bar at 60% throttle. We have since limited the WG duty cycle to 20% and are slowly increasing it with each subsequent file revision to arrive at a target boost of 1.2 bar (18psi). On the last revision at 35% duty cycle I saw close to 0.75 bar. I anticipate that a WG duty cycle of about 55-60% will get us to our target of 1.2-1.3. The idea here is to use a spring soft enough that the N75 can effectively control boost via ECU commanded trimming of the boost reference air from the Y-pipe to the WG actuator. All of the above is based on a fully built race prepped 4.0L engine so your results may be slightly different on a stock 3.6 block.

Based on what we are seeing, there is absolutely no reason to run the blue stiff spring which according to Tial would be more appropriate for someone running a 2.0 bar / 30psi set up. We've spent a good bit of R&D with getting these turbochargers set up properly but in the end it will be worth it as these units spool very quickly and have an apparently limitless top end. Even at 0.6 bar on my 4.0 these seem to pull harder than my UMW K16/997GT2 turbos did at 1.2 bar on my 3.8. FYI, Tial is close to releasing a new dual port WG actuator which would be a significant improvement to the single port WG as it would allow to run a very soft spring and still have the performance of a stiff spring on the top end. We will be testing these for Tial when they are ready.

 

I didn't have a problem with spool or throttle control but the wg pressure (as read by my HKS boost controller) was within a few psi of the target boost of 21-22psi on my car. As I'm sure you know, the 997 turbo uses closed loop boost control unlike the 996. The only issue I encountered was that the car would bog ever so slightly between shifts...ie. 3rd gear full throttle...change to 4th...4th gear full throttle. It would have a half second of bog and the logs showed a boost spike transiently with throttle partially closing and lambdas plummeted. From speaking with Tial, the softer spring should allow the boost controller to better control the wastegate and solve my issue.
I had understood the dual-port wg actuator would be useful for those wanting much higher boost...

 

I am not familiar with the 997 boost control at all unfortunately but would imagine its different due to the VTG turbos. Like I said and suspected, what works for my set up may not work for yours as you have an external controller to boot. I would go with what Tial recommends. The nice thing about their WG set up is that they offer several different springs which can be paired to tailor the cracking and final pressures in 2psi increments. For me, the softer spring was crucial as there is simply no way to control boost if the spring does not allow the WG to open until a much higher threshold. Having a nice progressive throttle modulation is imperative for my use. Every set up I ran on the 996 had the WG spring cracking in the 7-8psi range and fully open by 12-14psi with the N75 trimming air to control the WG and allow higher boost beyond that.

On the 997, what was the reason you went with an external WG controller? You can't use the stock boost control architecture if using a non VTG turbocharger?

 

That's right...there's no choice. I was reluctant to leave vtgs because of the fear of unintentional "issues" but hopefully my issues should be resolved soon.

 

Hey Nathan,
The following dyno run was done last week on a base low boost file at 0.75 bar (11 psi) with a result of 580whp and 593wtq on 91 octane. A/F ratios are very fat right now and we will begin trimming them down once we reach our target boost of 1.3 bar (19 psi) on 91 octane. We have another 0.55 bar of increased boost to get to 1.3 so a ways to go still before everything is optimized and all the peaks and valleys smoothed out. By comparison, my 3.8 did a max of 620whp at a much higher 1.25 bar with the UMW K16/997GT2RS turbocharger.

We had the N75 limited to 50% for this dyno run and have since increased it to 65% which is giving us 0.95 - 1.0 bar. There is a significant seat of the pants increase in power at 1.0 bar v. 0.75 bar. The next file will have it bumped further to incrementally get us to a 1.3 bar target. So far I'm very impressed with these turbochargers, there is really no comparison with the K16s. I will post up addition dyno charts as we get further along with finalizing the tuning. I will be at the track next weekend which will get me more data for getting this all finished up.

Comparing this engine with the 3.8, it just plain feels bigger and more responsive as we are using the larger displacement in lieu of boost and that gives the motor a more of a normally aspirated feel. We are using the latest generation RSR crank along with the RSR billet IMS. The engine exhales through a 3.5" titanium exhaust and in combination with the XR980 exhaust back pressure is very low. On the intake side we are using highly efficient Marston Aerospace 4" intercoolers which keep the IATs amazingly low. The engine loves to rev. It's really fantastic. BTW, I was by the shop yesterday and looks like Chris has your engine is pretty much bottoned up. Looks great. Cheers!



[url=[ame=https://flic.kr/p/2euYEF3]https://flic.kr/p/2euYEF3[/ame]]

 

That curve looks real promising, nice gradual ramp up and it seems to want to carry the power well past redline. Do you think the drop around 6250 is timing related?

No doubt a k16 wouldn't do your motor justice, though I wonder if a stock 3.6 or even a mild 3.8 could move enough air to spool these up as early as your does.

Fingers crossed the additional boost will only move this curve up but stay as flat. That combined with getting that dip dialed out should make for a killer build especially considering your curb weight and suspension.

I'm trying to keep my car out of my mind to avoid going crazy. My sacrificial toy is on BaT this week, hopefully its gone by the time I need the garage space for the Porsche again. https://bringatrailer.com/listing/2015-subaru-brz/

 

I think that dip around 6200 will be dialed out for the most part even though my 3.6 and 3.8 also had it in the same spot. I have a feeling it has to do with the low/high lift switchover. I certainly can't "feel" it. Again, this run was on an initial file which will be fine tuned further as more boost is brought into play. We latest 1.0 bar file I have on the car now has been tweaked and torque brought on more softly down low which gives the motor a very nice smooth power/torque curve. I'm curious to see what the next dyno chart will look like. We may put it on the rollers tomorrow.