I love the thought process and the attention to detail that is going into this project Dan.

Keep it coming :-)

 

The turbos I chose are the Xona Rotor XR6564 with IWG (internal wastegate) turbine housings. The reason I chose these is because they have enough compressor wheel for ~1300whp, and utilize internal wastegates. This greatly simplifies the exhaust fabrication - all I had to do was modify the outlet pipes from my BBi exhaust to fit the TiAL v-band outlets. They are also quieter, with the wastegate gasses being contained within the exhaust without being dumped to atmosphere. These housings use a TiAL patented setup that swirls the wastegate gas around in the housing and uses it to increase turbine efficiency via a venturi effect. I'm also using the smaller turbine housing option - the .62 A/R. A larger turbine housing, the .86 is a quick swap with no other changes in the future. I'm monitoring backpressure (eMAP) to give us a good idea of where the limits are.

Right now where I am on the stock gearbox it might actually make more sense to use the .86 since we are essentially limiting torque in the midrange to protect the transmission. This would drop backpressure at the higher RPMs and give me a little top end back for the mid-range we're not using. It's always a game of optimization.

One of the reason I chose this turbo is that it's the smallest of the series. I had originally planned on using XR7164 or XR7864, but decided to start smaller to maximize my requirements for street driving. I can always swap out parts later without having to change any other components. The exterior dimensions stay the same.

XR6564
Compressor Wheel - 57/79mm inducer/exducer diameter.
Turbine Outlet - 64.1mm diameter.
65lb/min max compressor mass flow.

If the car ever starts to feel "slow" I can swap out parts to either;

XR7164
Compressor Wheel - 59.1/82mm inducer/exducer diameter.
Turbine Outlet - 64.1mm diameter.
71lb/min max compressor mass flow.

XR7864
Compressor Wheel - 62.1/86mm inducer/exducer diameter.
Turbine Outlet - 64.1mm diameter.
78lb/min max compressor mass flow.


Still need to fabricate the WG actuator rods, but otherwise they are ready to go.


The Xona turbos can certainly claim the winning position in the beauty contest. FAP covers (flow advancement port), super sexy wastegate actuators, and CNC billet compressor wheels... yeah, it's the FAP you were really thinking of.


Here you can see the inner/outer concentric rings of the exhaust. Wastegate gas is swirled through the outer ring, and gas that passes the turbine is in the inner ring.

I'm running these on the Syvecs with turbo RPM sensors in the compressor covers. This gives us shaft RPM, and we can accurately spin the turbos for maximum flow. Boost really isn't a good indicator of how hard you're pushing a turbo. The VE (volumetric efficiency) of an engine, the size of the engine, etc. can really change things. The best way to judge how hard you are pushing a turbo is how fast you're spinning it. The strategy is get it to the highest efficient shaft speed, and hold it there. Use all of the turbo. The arbitrary "boost" value of positive manifold pressure isn't nearly as authoritative as people make it out to be.

Wastegates are also an interesting topic. It seems counter intuitive, but the less boost you want to run the more wastegate you need. In order to slow the turbo down, you have to bypass more air around the turbine, not less. A turbo with no wastegate would spin *really* fast, once. What you really get out of external wastegates is flexibility. Run any turbo, run any amount of boost. All of it, or none of it. An internal wastegate setup is tuned to the flow of the compressor, and can run a "reasonable" amount of boost -- say 15psi to as much as the turbos can flow.

While I had finally come up with some turbo specs I was happy with, Unobtanium was busy working on the headers. Remember when I said that the experience with the previous vendor worked out for the best? This is when things start to get really cool.


In the beginning, there was inconel.


Chris @ Unobtainium is really the metal whisperer. His communication is off the charts, all the pictures he sent through the process were phenominal.


Fabrication photos are so much fun.

Anyone interested in the highest quality custom welding for their project should just call Chris @ Unobtainium and get it over with. Seriously, he is that good. Don't visit his Instagram feed unless you're wiling to just throw your hands up in the air and buy everything he makes.

Still more coming...

 

How's your progress? John told me about your project, very happy to hear there are others out there with similar parts. You won't be disappointed.

 

rix it looks real good. I see you went with 1.75" primaries which is the appropriate diameter for over 1kHP range with some small trade however your turbine inlet diameter at the header flange looks like its around 2" so it ends up being the tuning piece for velocity anyways. The header model parts are from IC EngineWorks, I have used them extensively at my previous employer, they work well. I remember when they were released in the market roughly 10 years ago. Right choice on header material, minimum should be 321SS for durability, if you have the cash go Inconel.

I don't know where you guys want to end up in backpressure ratio, I would expect you end up at the .86 A/R. Really depends on your power target.

Great work.

 

that takes some self control. my conversation with Rob went different, oh you want all of the horsepower, ok you are getting the 9567.

 

Robert was really looking out for me. Given the timeline of the project we had decided on the general family/series of turbo, but didn't make a final decision until just a couple months ago. In the interim he made mock ups with empty bearing housings/no wheels so the fabrication work could be done. Turns out the fab work never did get done, I had to go with Unobtainium to get it done. Very happy with that decision in the end. I can't say enough positive things about Chris @ Unobtainium.

Everyone wants all the horsepower, but if you look around people on 7864s are making the same power I am and not using all of the turbo. It'll be more clear when I get all of the photos & data I have out there. 9564 is huge, I think you could do 7865 (or 7864) for instance without much fabrication drama and get much more response and still do 1500whp.

 

Your eyes are pretty calibrated, here's a measurement of the v-band turbine inlet flange.

Turbine inlet flange ID is 1.967"

I'm giving up some mid range right now with that housing at the expense of top end, but I can't use the mid range without putting too much torque through the transmission. It would probably make sense to swap to the .86 but I don't want to touch it right now. Car runs so damn good I just want to leave it alone and enjoy it for a while. Inconel is a no brainer with Unobtainium, their prices are very reasonable.

 

Glad to hear it's running well I tend to pick larger a/r because of pumping work, I always want it as low as I could go. Maximum backpressure ratio I like 1.25 to 1. Not always possible but I try to stay under that. My stock vtgs were around 2 or 2.5 to 1 based on some data Mitch posted a long time ago when he released the base e85 file My current vtgs are better based on vane position but I haven't actually measured. And at this point I can't do anything about it very easily. There are options I have explored in simulation

Can't wait to read more about it. Excellent project

 

What torque do you feel is considered safe for the stock transmission?

 

At Bill Rader's recommendation I'm trying to keep it under 950 ft lbs or so. It wants to make considerably more than that around 5,000 though.

 

Hard to imagine that level of torque. You see the .86 will keep it plenty safe

 

You should use the .62 IWG housing, that's what I've detailed in this thread.

 

There's no reason to buy external gates really. If you're pushing the turbos hard, you're not even losing flow because all of the exhaust is going through the turbine anyway. Unless you want way more expense, packaging issues, more things to crack, etc. There are more and more properly designed internal wastegate setups these days. Work with a company like Forced Performance/Xona and you'll be fine. It will be quieter, simpler, and cheaper.

Now if you're going to swap between tons of different turbos and try to do 2,000whp on XR9567s with methanol injection the external wastegates are what you need. But for a "mild" 600hp turbo like the XR6564 you don't need to go to all of that extra expense. It looks cool, and sounds cool up until the point where you have to pay for it and live with it.

As far as efficiency at lower boost, I can tell you my car did 700whp with a great curve on the wastegate springs which was about 16psi. That's 93 octane pump gas as well. You shouldn't have any trouble with it no matter what range of boost you throw at it. Those compressors are a good match for the setup we're talking about. Just make sure you get the heads done appropriately. Given that you're in the UK the pump gas is different, but no reason you can't do 850whp on pump gas with things turned up.

The budget 3.6 build isn't a bad idea, but for the amount of labor required for all of this work it makes a lot of sense to go ahead and replace the pistons/sleeves and go 3.8L while you're in there. I don't think you need the GT3 oil pump, but definitely do head studs, head porting, cams, valves/springs. I've outlined my thinking and why above in this thread, for a docile driving street car that is turned towards the max-effort side of things I don't think you'll find a better combination.

Take your time and do the research so you understand what everything does and why you need to do it. If you're looking for 1000whp+ you should really look into head work as well as the other obvious things. Given the plug and play desire you have it seems pretty simple - do the internal gates, stick with a Cobb accessport for now, don't worry about the transmission. Just work with your tuner and keep the torque around 900 ft/lbs and enjoy the car.

 

997 Turbo already has an oil pump with dual pick ups just like the GT3.

On 996 you upgrade the pump.

 

Thanks for the info Mark, I didn't know that. I stuck with the stock pump at the recommendation of John Bray.