Porsche specifies this kontrollierte qualitat grease stuff on all the o-rings. I bought a tube from Pelican Parts. I lubed up a new o-ring that goes between the oil reservoir and oil drain flange of the turbo.
I lubed up the o-ring on the infamous vacuum line before installing into the compressor housing.
The outside diameter of the stock inlet tube is about 2 3/8” which I estimated the internal flow diameter to be 54mm (about 2 1/8″). At the compressor inlet, the inner diameter of the stock inlet tube is actually smaller than the inducer diameter of the compressor wheels on the S and GTS turbo variants. My hypothesis is the inlet was designed for the 2.0L engine turbocharger and Porsche didn’t want to tool a new part for the larger turbos on the 2.5L engine.
The RaggDoll Motorsport compressor inlet tube is 3” outside diameter which I estimated to be 72mm inner diameter. The RaggDoll compressor inlet tube will pay bigger dividends on the 2.5L engine turbos by not having the inner diameter at the compressor inlet smaller in diameter than the compressor wheel inlet diameters.
I like using this online pressure drop calculator to do quick and dirty comparisons. The new larger inlet should have about one third the pressure drop of the stock inlet. Anything to reduce pressure drop on the compressor inlet side pays big dividends in reducing the compressor pressure ratio; that has compounding effects of reducing intake air temps and turbine pressure ratio.
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I personally think you can actually hear those minute surface flow improvements in the exhaust note. At this level, you’re not chasing performance gains, but rather aural pleasure, instead.
Way back in the day, I did gas stand testing to quantify the turbine efficiency improvement due to extrude honing a turbine housing. The gain was measurable and worthwhile for those seeking maximum turbine efficiency. The two major areas where surface smoothness mattered were the turbine inlet section and at the narrow throat section where the flow exists the housing volute and enters the turbine wheel. Basically, wherever flow velocity was highest. I couldn’t smooth out the throat section on this turbine housing, but I got the entrance section done and I bet the difference is measurable on the gas stand. The compressor side, not so much. I also like to call it arts and crafts time and it’s relaxing. Sure, the hand smoothing of the turbine housing is a small incremental improvement, but so is a drop-in air filter, thermal barrier coating, compressor inlet, or my x-pipe exhaust tip. Keep on adding them all up though and it comes meaningful 🙂
Awesome and thorough write-up! After a bunch of 4 cylinder miatas, I don’t think I could upgrade to a Porsche with a 4 cylinder though lol
I had glanced at the GT4, but it was essentially a $50k premium taking into account the ADM dealers were asking. The 4.0l GTS was roughly a $25k premium over my T. But in the end, I still really like turbo-4s.
Initial engineering meeting for the 718 6 cylinder : “What would be the best engine layout and displacement to give customer’s high levels of power with a linear powerband?”
Initial engineering meeting for the 718 4 cylinder: “Who has a copy of China’s engine displacement tax regulations?”
For the higher trim GTS, I don’t disagree. For the base trim, the 2.0l turbo stomps all over the 981 base 6-cylinder in torque, power, and fuel efficiency.
That said, the 2.0l with this turbo upgrade, good fuel, and some exhaust mods is 350wtq and 400whp capable which puts it in the range of a bolt-on and tune 4.0l 6-cylinder. I’m straddled with Cali 91 octane and keeping the stock cat. The 2.5l engine with larger upgraded VGT turbo is 500-550whp+ capable, over 400wtq, and still good response to boot because of the VGT. No NA modded 4.0L can touch that.
Not that everyone cares about fuel economy, but I can get 32-34mpg highway no problem. The 4.0l can’t touch that.
“The 2.5l engine with larger upgraded VGT turbo is 500-550whp+ capable, over 400wtq, and still good response to boot because of the VGT. No NA modded 4.0L can touch that.”
565>500-550 https://demanmotorsport.com/4-5l-cayman/
“I’m straddled with Cali 91 octane and keeping the stock cat.” –> We forge the chains we wear in life.
Mmm… A bit extreme as that’s well past bolt-ons and a $50k+ engine package. But it’s possible. RaggDoll is also working on a non-VGT big turbo package that will be good for 600-650whp on the 2.5l. A built bottom-end is recommended at that point. Of course, it’ll have some lag that the NA engine won’t.
Did you cerakote the compressor housing? Also, since the boost was holding with higher flowing wheels, did you notice a mass flow change in the data logs?