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Cayman The Destroyer!
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2,624 Posts
Discussion Starter #261
Mezger reactor is ready for installation! It's actually more compact than the old engine and will allow moving the engine and transaxle forward 1" and down 2-3". Much better axle angles and improved CG. More room on the top of the engine for routing dry sump hoses and easier maintenance too.
Unfortunately it's won't be tested before Laguna on June 12th. There are going to be some outrageous cars competing in GT1 including 2 new GT2 RS Club Sport and 2 Audi A8 LMS. It would be a great benchmark to test against.
I'll be driving a 2006 GT4 class Cayman again and it will be great fun! Mezger Reactor crop.jpg
 

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Cayman The Destroyer!
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2,624 Posts
Discussion Starter #262 (Edited)
Solid progress happening. We are looking for every bit of space to allow perfect axle alignment. Vision determined that the bellhousing could be trimmed 25mm by changing to a thin single mass flywheel. the 1" reduction of distance allows perfect alignment for the axle shafts. A very good thing with 600 lb/ft of torque!

AAsco has finished the flywheel ( standard G50 single mass TT) and bellhousing modification. Clutch is being upgraded from a dual disk Tilton to a 3 disk. 1/3 more torque capacity and smoother engagement. The clutch is only used to start from a dead stop and first gear is very long so starting can be a bitch.

Other details like moving the clutch pedal to the left and widening the brake pedal to facilitate left foot braking are done too. Engine and gearbox will go in next week and the exhaust, plumbing and wiring will be addressed.
I'm starting to get excited again now! Brake pedal edit.jpg
 

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Premium Member
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I can certainly understand why; we're excited for you too.
 

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Cayman The Destroyer!
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2,624 Posts
Discussion Starter #264
This is the new DSC stand alone controller mounted in the car. The system has it's own accelerometer and the only connections to the car are +12 V and ground. No laptop required for setup, it has it's own screen. It is possible to set up more that one program and it can be selected by a push button on the steering wheel on the fly for an instant A-B
We just couldn't get the standard DSC to talk to the Motec CAN. Hopefully this will work well. DSC Controller Mounted.jpg
 

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Cayman The Destroyer!
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2,624 Posts
Discussion Starter #265
Engineering and fabrication as art? I wish I could weld like this! The new front mount is engineered to allow the engine to be placed as far forward as possible. It can be adjusted vertically by spacers where it mounts to the chassis. The large Teflon center bushing allows for a tilt in the engine and gearbox if desired but functions as a solid mount with almost no deflection. Elegant solution on the fly. Front Engine mount.jpg
 

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Cayman The Destroyer!
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2,624 Posts
Discussion Starter #266
Great progress this week. Bell housing and tranny input shaft machined. Tilton 3 disk clutch and pressure plate ready. Race headers intended for a 996 TT work nicely for the mid engine location, just have to cut off and plug the waste gate stub as my turbos have internal bypass waste gates
Cut BH.jpg new header and turbo.jpg 3 disk clutch.jpg
 

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Vendor
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470 Posts
What turbos are you running?

My racecar is internally gated as well. These modern "G" series Garrett turbos, EFRs and the Xona (what I run) have really good internal gates!
Great progress this week. Bell housing and tranny input shaft machined. Tilton 3 disk clutch and pressure plate ready. Race headers intended for a 996 TT work nicely for the mid engine location, just have to cut off and plug the waste gate stub as my turbos have internal bypass waste gates
View attachment 269559 View attachment 269560 View attachment 269561
 

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Cayman The Destroyer!
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2,624 Posts
Discussion Starter #268
Garrett G25's. Staying with smaller turbos for throttle response.
 

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Cayman The Destroyer!
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2,624 Posts
Discussion Starter #270
We made 709 at the wheels at ~1.2 bar G 25's on 100 octane with the 4.0L M97. A sweet engine with great throttle response but the heads where lifting! New Mezger has 12mm studs and good gaskets so I think it will be much more reliable.
269564
 

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Vendor
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470 Posts
That's awsome! My 525hp cayman is scary on track... I can't imagine what yours is like!

We run 1/2" headstuds on all of big power motors.

We made 709 at the wheels at ~1.2 bar G 25's on 100 octane with the 4.0L M97. A sweet engine with great throttle response but the heads where lifting! New Mezger has 12mm studs and good gaskets so I think it will be much more reliable.
View attachment 269564
 

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Cayman The Destroyer!
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Discussion Starter #273
Time to make a decision on turbos for my 996 race engine. I've been aware of turbocharged engines and how to select turbos since the early 80's. My car (Cayman) was a 4.0L M97 and initially we used Turbonetics turbos as our goal for the engine was rather modest to slot into the GT2 class ~430hp at the wheels. When we upped the boost the results were not good so it was time to do some serious engineering and upgrade the turbos.

Most people think that a lot of boost pressure is the way to big power numbers but actually it's not boost but airflow through the engine that makes power. All 4 valve Porsche engines flow very well out of the box so it's a big advantage to start with. Anything that can be done to increase airflow by limiting restriction makes the system more efficient and powerful. So we designed the physical layout and ducting to keep losses very low.

Choosing a turbo is much easier now if the manufacturer supplies compressor maps and turbine flow numbers. On line tools like Garrett boost advisor and BorgWarner MatchBot allow an excellent analysis to be made. When I ran the analysis for my 4.0L M97 boost advisor recommended a very small turbo G25-550. I ran a more detailed analysis on MatchBot it confirmed the choice. My race shop wanted to go with much bigger turbos but I persuaded them to use the G25's and the results where outstanding. Throttle response was amazing and we made 710 WHP at 1.3 BAR. Unfortunately the engine started to lift the heads and leak combustion gasses into the water jacket.

So now we have a strong 996 Mezger TT built for the car and the design process starts again. I've heard good things about Xona Rotation turbos and my race shop has a good relationship with Evospec an engine builder that is a vendor for Xona. They build a lot of very high output Mezgers for straight line racing (1200 WHP!) They recommended XR6564 or XR6157, but there are no maps available for these turbos. He did not have any dyno charts for engines using these either. Doing my due diligence with units having complete engineering data Garrett G30-660's look like the best choice. The compressor flow is about the same as the XONA 6157 but with smaller wheels on both sides. Smaller wheels mean faster spool.

So my choice is Garrett G30-660 with a .83 AR hot side. A 996 Cup in the shop with a 3.8 L 996 TT is getting the larger XONA 6564 and it will be interesting to see how the two engines perform on the same dyno.
 

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Cayman The Destroyer!
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Discussion Starter #275
I always have doubts when a manufacturer won't supply complete data on their products. There is no proprietary secret in compressor maps and turbine flow charts. Without manufactures data or dyno pulls from a similar engine running XONA I'm going with the Garretts. I know XONA claims that their turbine design is superior to anyone else's but without data I have no way to know what it means. With good data I'm sure I will be placing the power band in the most efficient compressor operating range for the boost pressures I'll be running. It will be interesting to see how the XONA and Garrett turbos compare on similar engines and the same dyno. It may even be possible to switch turbos and run them on the same car.
 

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Cayman The Destroyer!
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2,624 Posts
Discussion Starter #277
We will be using external waste gates on both the Garrett and Xona turbos
 

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Cayman The Destroyer!
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2,624 Posts
Discussion Starter #279
I did with my G25's. Better choice of AR's with external gates for both Xona and Garrett and I already have a set of Tial gates in my junk box.
 
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