Project 987.2 Cayman S: Getting More Out of the Engine to Chase the GT4 Part 1

Previously we have been working on Project 987.2 Caymans Suspension and Brakes to get them up to Cup Car standards.  With that work being completed we are now going to attack the engine and transmission performance.  Our goal is to try to equal or surpass the power of the 3.8 liter 981 GT4 in a car costing many times less money with the main goal for the car to turn better lap times than the GT4 as well.

If we can get better engine performance we feel that our car can be significantly faster because our car has Porsches acclaimed PDK dual-clutch transmission.  With some minor tuning, the PDK in the Cayman can be turned into the lighting fast-shifting race-box like transmission as found in the GT3RS with 7 speeds and a deep overdrive to boot! This will bode well against the manual transmission only GT4 which has a tall first geat and wide spacing between gears 1-2-3 which affects the car’s acceleration and driveabitly around a road course to boot.  The PDK also has a huge advantage as it can be upshifted and downshifted in a turn without messing up the car’s balance.  There is a reason why Porshe makes the GT3 available with the PDK as the standard transmission and the PDK version is much faster around a road course than the manual 6-speed version of the car.

So what are we going be doing to get our lowly Cayman S up into the range of the rare GT4? Read and see!

The first part of an engine build usually includes an exhaust and our car is no exception.  We selected Fabspeeds Valvetronic exhaust.  The Valvetronic exhaust is perfect for our intended dual use as it can work as both a straight-through race exhaust or a muffled exhaust to avoid attracting too much attention on the street.

The Valvetronic system uses this vacuum actuator to open and close a valve that can divert the exhaust gasses through the mufflers or run straight out the back of the car with minimal backpressure. The Valvetronic system is compatible with the OEM Porsche PSE sports exhaust system with the center console switch or you could use the Fabspeed Valve Controler kit and use their remote control to operate the valve.

You can see the actuator and the valve here.  They are constructed of stainless steel to reduce the chances of corrosion and sticking.   Fabspeed has some other exhausts with even more direct cutouts that empty into short cutouts for the very minimal in backpressure but we wanted our exhaust to empty into the same location as stock so we would not have any problems with fit with our upcoming Verus Engineering rear diffuser.

30 comments

  1. Aren’t those Fabspeed oxygen sensor spacers just an overpriced version of installing spark plug anti-foulers on them?

    If anything, they are designed to keep the rear 02 sensor reading INACCURATELY by pulling them out of the exhaust stream so the ECU thinks the secondary cats are cleaning the exhaust sufficiently. I thought they were for off-road use only?

    1. These devices have a cat in them, they are not just antifouling spacers. The rear 02 sensors don’t control the AFR, they just look for the voltage to drop after the cats light off. This car is basically a race car for of road use.

  2. Those manifolds look great and the numbers others are getting with them are YUGE.

    It is curious with the intake tube necking up for the throttle body, unless I’m seeing that wrong.

  3. The reason that dimples work so well on golf balls is because they are rotating. The dimples help disturb the boundary layer on the surface so that the airflow ‘sticks’ to the surface of the ball.

    They don’t use dimples on any non-rotating parts on F1 cars, and I’m sure they would if they actually reduced drag, and improved flow velocity. F1 teams could certainly integrate dimples into the bodywork if they wanted to.

    Zipp uses dimples on their high-end carbon fiber wheels for the same reason, because it’s rotating part. I have yet to see dimples on bicycle frames, and they would most certainly add them if they reduced drag, and improved flow velocity. There’s plenty of money to be made selling ‘low drag’ bicycles to all the dentists out there. 😉

    From Scientific American:

    “The spinning action makes the air pressure on the bottom of the ball higher than the air pressure on the top; this imbalance creates an upward force on the ball. Ball spin contributes about one half of a golf ball’s lift. The other half is provided by the dimples, which allow for optimization of the lift force.”

    https://www.scientificamerican.com/article/how-do-dimples-in-golf-ba/

    From Racecar-Engineering:

    “Zipp has also developed a dimpled hub for racing cycles, which suggests areas such as the driveshafts on a single-seater racecar could perhaps benefit similarly. An area such as this is constantly exposed to the sensitive rear airflow and, whilst shorter and under somewhat different demands, the principles could potentially be transferred. ‘I think that our new dimpled hub is pretty analogous to a racecar driveshaft, and on the hub we are seeing 14-20g of drag reduction at low yaw angles in the wind tunnel (at 30mph) and this is only a very small part,’ explains Poertner. ‘At the higher yaw angles the flanges (the Zipp hub is only 100mm end to end with flanges at each end), start to block the airflow over the centre of the hub so the effect goes away,’ claims Poertner. This is less likely to be a problem with a racecars’ driveshaft.”

    https://www.racecar-engineering.com/articles/technology/can-dimpled-aerodynamic-surfaces-reduce-drag/

    1. Dimples make the boundary layer thicker, rotation doesn’t have anything to do with how they work, theu just need flow velocity. Manipulating the boundary layer can make more or less drag or reduce stagnation and increase velocity in a passage. Or it could make a passage flow less.

  4. Dimples only work on rotating surfaces.

    From Racecar engineering:

    “As well as its work with wheels, Zipp has also developed a dimpled hub for racing cycles, which suggests areas such as the driveshafts on a single-seater racecar could perhaps benefit similarly. An area such as this is constantly exposed to the sensitive rear airflow and, whilst shorter and under somewhat different demands, the principles could potentially be transferred. ‘I think that our new dimpled hub is pretty analogous to a racecar driveshaft, and on the hub we are seeing 14-20g of drag reduction at low yaw angles in the wind tunnel (at 30mph) and this is only a very small part,’ explains Poertner. ‘At the higher yaw angles the flanges (the Zipp hub is only 100mm end to end with flanges at each end), start to block the airflow over the centre of the hub so the effect goes away,’ claims Poertner. This is less likely to be a problem with a racecars’ driveshaft.”

    1. I am with Joe and James, backed up with scientific research. It is a bit sad to see Mike/ MotoIQ insisting and “forcing” a belief on their audience because they’re promoting a product which they have discount on, (a big discount or a small discount does not matter). Sometime, not always, it looks like they’re trying to shovel into people’s head that what they decided to purchase or mount on their project cars, (or customer car) is the absolute best, which in SOME cases just isn’t true.
      I want to make it clear that there is no hate in my opinion but I stopped following/ reading MotoIQ a while back when I realized that 99.9% of the project cars use the same aftermarket parts from the same companies over and over again, (while some of those companies are great and offer great products) there are equally other outstanding companies out there that do make exceptional products but on this site are never heard, or never discussed, just because MotoIQ does not partner with them and/or simply are not sponsored by them.
      A variety of companies IMO is key to make it entertaining. I’d like to read articles that showcase Pankl products, X-TRAC gearbox, Staubli connectors and Bosch Motorsport electronics. DMG-MORI work, or Brembo/ AP Racing components……just to name a few.
      Mike, please share any proven articles that showcase boundary layers on a non moving object and its results, just for the sake of educating your audience.

      1. What does stating the truth have to do with forcing a belief on an audience. I didn’t even pass judgment on the part yet! That is going to come when we dyno test it! All I said is dimples do not have to be rotating to affect the boundary layer. Here is my comment exactly word per word. “Dimples make the boundary layer thicker, rotation doesn’t have anything to do with how they work, they just need flow velocity. Manipulating the boundary layer can make more or less drag or reduce stagnation and increase velocity in a passage. Or it could make a passage flow less.” There is nothing saying that this part is awsome or hey buy this part because it has dimples. In fact, there is nothing in my statement about this particular part at all good, bad or otherwise. Alex, I see that you are back to making uneducated remarks reflecting your opinion with a lot of conviction. You talk a lot about how this or that should be done like you have a lot of knowledge but you have never even personally built or achieved anything in the motorsports world yourself not to mention even built a decent streetcar. You talk about components that are used in very high forms of racing, well most of our readers including us cannot afford to use those, even with pretty well-funded efforts. Alex, I am not going to spend any time mounting a scholarly response to you. You are a troll even if you don’t think of yourself as one. I suggest you get some basic books on fluids and educate yourself.

        1. “You talk a lot about how this or that should be done like you have a lot of knowledge but you have never even personally built or achieved anything in the motorsports world yourself not to mention even built a decent streetcar. You talk about components that are used in very high forms of racing, well most of our readers including us cannot afford to use those, even with pretty well-funded efforts.”

          I didn’t say “how things should be done”. I gave you a sincere suggestion on how to carry on a debate stated above. Showcase valid data that state that what you wrote is indeed correct. Joe and James did so, and for you to go against engineers that work for Racecar Engineering, a very well written magazine I should say, it’s pretty idiotic on your part. Those folks don’t race Nissan’ S chassis and Chevy LS’s!!!

          You can call me a troll, or that I make “uneducated remark” or someone who hasn’t built anything noteworthy. It doesn’t faze me.

          I tend to shy away from social media, (although I use it occasionally).
          I don’t have to prove anything to anyone but I can guarantee you that:
          1. I have built few noteworthy “street” cars, believe it or not.
          2. I am currently working for few well known teams that race in the LMP3 and GT3 classes on two different championship and they do use the components I mentioned above.
          3. Instead of feeling salty, I would say that opening your horizon, so to speak…and accept the fact that some people see these results (CDF and wind-tunnel data) on a daily basis, and as you know, at this level of motorsport there are lots of secrecy and NDA’s to sign.

          Have a good night Mike. Tomorrow it’s gonna be a very busy day for us. We’ll race the final race of the season in the Michelin Le Mans Cup at the Circuit of Algarve in Portugal.

          1. If you are not the same Alex Butti that used to toll here all the time than I apologize, I think you are though. Joe and James showed data from a magazine article about Zipp bike wheels and why dimples help golf balls fly farther and made the assumption that dimpled surfaces have to be rotating to do something. Rotation can make the effect stronger because of its additional velocity but dimples do not have to rotating to have an aerodynamic effect good or bad. That is basic fluid dynamics, not a magazine article. Your assumption that because someone wrote an article that a dimpled bike wheel works better because its rotating means that dimples only work on rotating surfaces because CFD and Wind tunnel data are presented is a serious flaw in logic. That assumption is idiotic on your part(quoting you). Ask any degreed mechanical engineer if a dimpled surface has to be rotating to have an aerodynamic effect and they will tell you the exact same thing I am. Race Car engineering to me isn’t a good magazine as far as a source of technical information which is why I canceled my subscription. The stuff they write about is usually secret so no good information is gotten and the pictures are not allowed to show much. Everything is spoken about in nebulous terms so my educated guess is as good as the authors. It is not the fault of the magazine, in order to get access to cool stuff, they can’t really go into any good details. I also don’t agree with some of their writer’s opinions sometimes, did you know that most of their writers are not engineers, but simply well-versed journalists? I know a few of them and I sometimes don’t feel that they are particularly qualified to write on some of the subjects. It’s just the nature of journalism and it makes the Magazine more of a good reference for European parts suppliers and in no way is it a professional technical bible. I think you are doing your usual magazine article engineering. If you are the same Alex Butti, you hung around people with cool cars, you are a JDM fanboi and used to hang out at some Japanese Speedshops and worship them, you drive a beat ass civic and you have never done any grassroots or other competition of any sorts other than hanging out and on your keyboard. If you are going to talk about LS-powered drift cars like they are lowly and try to flex, did you know that the drift team I work for is a factory effort with a $500,000 a year budget just for my car? That the entire program is a multi-million dollar one? That our car is about as technically sophisticated as a GT3 car and costs around the same? That our Pikes Peak effort was faster than quite a few GT level cars, some factory-backed efforts? Did you know I work under NDA for some factory and tier-one supplier programs? I don’t believe you work for a pro race team in any sort of technical capacity. What teams do you work for and what is your job?

      2. Also, Alex, this car has as far as I could get, the best off the shelf parts available for the platform. The caveat being off the shelf, not custom fabricated. We do not have a marketing relationship with any of the companies used on this project except KW. Most of the parts used on this car are from brands never before featured by us. The only brands ever used by us before are KW and Stoptech. If you are using the stock hydraulic system, there is no better brand of brakes than Stoptech and that includes AP and Brembo and if you read MotoIQ you would know the engineering reasons behind this. If you knew anything you could look at the factory GT-4 Cup cars and see that this car does not leave too much on the table to them and I bet it can turn similar lap times or maybe even better once it’s done. You are speaking as if we are corrupt, our opinions and test results can be bought and 99.9% of our cars use all the same parts. I take offense to this and I will say you are full of shit.

        1. I wonder if the guys above are using this as an application for a job at the Internet Research Agency (IRA). They seem really misinformed about basic fluid flow and then request easy to find top shelf racing suppliers which clearly isn’t the scope of motoiq.

          No offense intended, most of us aren’t dropping six figures on a gearbox.

          Again, love the article and stoked to see what the dyno shows.

        2. “there is no better brand of brakes than Stoptech and that includes AP and Brembo and if you read MotoIQ you would know the engineering reasons behind this.”

          “If you knew anything you could look at the factory GT-4 Cup cars and see that this car does not leave too much on the table to them and I bet it can turn similar lap times or maybe even better once it’s done.”

          Your statement is a bit amusing!
          If memory serves me right, James Sofronas from GMG Racing used to use Stop -Tech at some point on his race cars. Unfortunately I don’t recall in what class but I do believe he moved away from the brand, (for obvious reasons). But you can keep telling yourself that Stop-Tech are as good as AP Racing or Brembo’s motorsport brakes.

          As far as “GT4 Cup”…..(BTW there’s no such a thing as GT-4 Cup).
          There’s the GT4 class/ series, such as the Renault Alpina a110 GT4 or the KTM GT4 or the Porsche Cayman GT4 Clubsport, and so on and so on.). Then for example there’s the Porsche GT3 Cup series, IMSA, ADAC, and so on. Much like Ferrari offers the Ferrari Challenge exclusively for the current Ferrari 488, or Lamborghini that offers the Super Trofeo with the Huracan…..but if you only care about Formula D and Time Attack…..you should look beyond those venues……just saying’!

          Anyway, since you brought up your awesome Stop-Tech brakes, the factory “GT-4 Cup”, Porsches for example uses PFC monoblock BBK, while its bigger sister, the Porsche GT3 R uses the AP Racing Pro 5000 (also monoblock). While the big daddy, the Porsche RSR also uses the AP Racing Pro 5000 Radical BBK, (albeit with different piston sizes).
          On a side note, I find it interesting that Porsche doesn’t extend its contract with AP Racing since it already provides brakes for the GT3 R and the RSR and offers something for its Cayman GT4, that’s probably a budget issue but that’s a business related topic.
          You can keep believing that the Stop-Tech are numero 1!

          1. Of course, your logic is flawed. You intentionally edited my statement which said, if you are keeping the factory hydraulic system, Stoptech is the best. This is the most important part of my statement. Of course, I don’t discount AP and Brembo as being world-class brakes. Of course, StopTech’s offerings are not as advanced as AP and Brembo’s top motorsports systems. Stoptech is better than those systems with factory OEM hydraulic and electronic systems though, more so than the finest Brembo and AP motorsports systems have to offer under that condition. The main reason why GMG stopped using Stoptech is sponsorship money if you knew people who worked for the team you would know this.

            This is a GT4 Cup car as raced in the US under several similarly named classes

            https://www.porsche.com/usa/motorsportandevents/motorsport/customerracing/racingcars/718-cayman-gt4-clubsport/

            I do more than FD and Time Attack, some of the highest level things I do are under NDA for OEM and Tier One suppliers including Motorsports programs.

    2. No, they don’t just work on rotating surfaces, but they often have a larger-than-normal effect there. The reason they are often used on rotating surfaces is because the surface velocity is high, and the round shape can benefit from the change in flow attachment from the dimples. For non-round sections, or lower velocities, the standard tradeoffs apply for pressure drag and friction drag, and whether there would be useful changes in flow separation from dimples.

      Do the dimples inside the manifold work? Who knows, maybe. We don’t have enough specific information to know that they don’t work, any more than we have enough information to know that they do. We have a manufacturer’s claim, and whatever real-world power improvement that can be shown on the dyno. Otherwise, you would need flow velocity numbers and/or CFD with/without dimples, because there is no way to separate the effects of dimples from other discrete changes to the manifold geometry or the thermal effects of the manifold material.

      So to imply that the dimples couldn’t possibly work because the part is not rotating, and Formula1 doesn’t liberally sprinkle them all over the cars, shows a complete lack of critical thinking (especially after reading the article from Racecar Engineering).

  5. There are research papers written on the supposed effects of dimples but non have concluded that dimples will maintain velocity over time on a surface such as an intake manifold. What is known is that a 36 grit surface in the manifold and a lower 60 grit in the tracts after the butterfly are helpful for maintaining velocity…
    We didn’t read any emphatic claims in the article. We are however excited to see how well the culmination of all these parts will effect performance over the stock pieces.

  6. Dimples of that size versus the hydraulic diameter of the flow are usually used to “trip” the boundary layer into a more turbulent flow. It takes net energy out of the flow, but if you energize the flow in an area where the flow field is rapidly turning (such as an intake plenum with sharp bends), it can be a net gain in flow throughput (i.e. the energy to energize the flow is less than the unenergized flow losses you’re avoiding).

    Like all things in engineering, it’s a trade-off/optimization problem. There’s no “always right” answer – it depends on what the conditions are and what you’re trying to do.

    And as far as not seeing turbulent “trip” devices on cars – they’re all over the place if you know what you’re looking at. For something plain-jane, just look at the tail lights of a Toyota Prius and you’ll see small canards/vortex generators that trip the thick boundary layer into a turbulent downstream flow that then pulls it closer to the back of the car. This reduces the total form drag of the car by having a lower suction area on the the back bumper area. On the other end of the spectrum, just look at the intricate barge board designs of modern F1 cars to look at all the tiny winglets and flip ups that are turning/tripping the flow into doing something preferable downstream. It takes energy out of the flow, but if it attaches the flow to an area, or turns it into a better area, it’s a net benefit.

    The hard part of engineering is knowing when/where to use these devices to get a net benefit!

    1. well put! Difficult=Expensive… Another tidbit learned from Darin Morgan is that “wet flow” in case of port injected motor doesn’t see the benefit of dry flow. i.e. direct injected.

  7. Will you by dyno testing it after all the mods are installed or will you be doing a before/after for each of the mods? It would be interesting to see what the mods contribute to the overall gain, in particular the plenum.

    1. Late-model cars need to be re-tuned after each change which would make the test very cost-prohibitive and time-consuming so no, we will be doing them all at once.

  8. Hey, sorry, didn’t mean to start such a heated argument. I know how the dimples work, but I have yet to see them used in any racing applications, and I know that people have tried. It seems to be entirely dependent on flow velocity, because the dimples are very sensitive to the Reynolds Number.

    Golf balls are moving at pretty low speeds, and that’s why the dimples are effective. Here’s a chart showing that a smooth sphere actually has a lower drag coefficient at higher Reynolds numbers.

    http://www.formula1-dictionary.net/Images/dimpled_drag_sphere.jpg

    The flow inside a intake manifold approaches 500m/s, so the dimples are not going to be effective, and they actually reduce the flow velocity.

    Here’s a post from an ME saying essentially the same thing:

    ________________________________

    https://www.cliosport.net/threads/does-dimpling-intake-ports-work-no.817453/

    I have just finished writing my final year dissertation after taking a break from work to finish my university degree. My employer suggested that I should investigate the effects of adding dimples to the internal surface of an intake port in order to determine if it is beneficial to intake port performance. The port tested was a Jaguar Lightweight E-Type intake port from a wide angle Jaguar head, which had been previously optimised using CFD to improve flow through the port. After nearly 300GB of simulations which have been running for months, I have not been able to improve the flow through the port using single dimples on their own, or covering the whole port in dimples, or even dimpling just the valve guide or valve stem itself. Putting dimples into an intake port does have some beneficial characteristics, but these are outweighed by the increase in skin friction.
    Probably not of any interest to most of you, but at least next time you see those awesome pictures of CNC dimpled intake ports on websites, you can rest easy knowing that they don’t help performance, especially if the whole port is dimpled!

    The paper was just my final year project for my engineering degree, it hasn’t been published or anything, although it was featured in my universities annual research feature journal thing.
    Anyway, there seems to be a tremendous amount of smoke and mirrors surrounding the truth with intake ports, a lot of it fuelled by things people quote as fact which actually are not, and stem from some 12 year old on pistonheads quoting theory as fact ha ha.

    Anyway, the gist of it is that a rougher surface texture helps energise the boundary layer of the fluid. This very thin turbulent region can be used to create a low pressure which helps “suck” the flow to the contour of the surface in question. As an incredibly rough rule of thumb, the rougher the surface the greater the effect, however the greater the skin friction penalty incurred. Also, the effect of “sucking” the flow to a contour becomes reduced at high reynolds numbers (read: flow speeds). Dimpling is an incredibly rough surface, so works very well with low flow speeds. My paper essentially concludes that the flow in most parts of the intake port are too fast to take advantage of the dimples. When the surface is too rough, it can actually trip the flow off of the surface earlier too, which is what happens around the short side curve on the bottom of the intake port if you put dimples.

    Due to the effect only causing turbulence in the outer sort of 1mm layer of fluid in the port, mixing doesn’t really come into it at all, which I was quite surprised by, given what I’d read on the internet before starting the project.

    I found that the best surface finish was between 0.8Ra and 1.2Ra, so a smooth machined surface but not polished, although the difference is honestly marginal. The only results from my sims which weren’t marginal at all, was dimpling the whole intake port, which cased the flow rate to drop by over 10%, which is why I wrote this post in the first place to warn people of the potential harm it causes if you apply a blanket surface texture to the whole port! The only limited success I had was by putting a couple of dimples in the region surrounding the valve guide, which caused the flow to reattach and hold its speed a lot better as it goes round the valve guide and stem. However, I wasn’t able to achieve a significant benefit to mass flow rate through the port, unfortunately, only marginal gains.

    1. My thinking is that dimples may help on the floor of the intake port before the valve guide, not to increase the flow but to help velocity with less expense of flow, This change is probably way less or nonexistent in modern ports designed with CFD and other analytical tools. This may help in older engine designs though and with carburated and port-injected engines by reducing wall wetting. I think this also probably hurts direct injection engines. When I was doing stuff for my master’s degree which I never finished, we experimented with super rough port finishes (40 grit as I recall) on a 4AG engine and we did see an improvement in BSFC and torque with a wider powerband at the expense of some top-end power.

      I think Honda/Acura had dimpled floor panels on the Vigor to reduce drag. I don’t remember dimples on bodywork for any other race car or production car for that matter. There was an episode of Mythbusters where they dimpled the entire surface of a car and did 2-way coast down tests that seemed to prove that huge bowl-sized dimples made a decent difference in drag when applied on the entire body of a car but the thick layer of Bondo they used to make the dimples in might have just improved aerodynamics or the mass increase might have affected coast down, I dunno.

  9. Any plans for cooling the PDK transmission? Our Cayman has a manual box, but I’ve heard of people overheating the stock PDK boxes in racing applications. Might be worth reaching out to BGB, Deman, or Vision.

    1. The current plan is to use a GT4 Cup car engine oil cooler and to greatly improve the water cooling with race type side and center radiators. If this proves to be not enough, we can divorce the transmission from the water and use an oil to air cooler.

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