Introducing our latest 9A1 GT4 based engine, the 4.5L GT4.

“I can honestly say that the Porsche Spyder with a Deman motor is the best street car of any cost that I’ve ever driven. It isn’t just the power that makes the motor so incredible, it’s the intangibles that make the difference: instant throttle response, perfectly balanced sound, predictability/linearity across the rev range, power/torque that match the car’s weight/tires, etc. I’ve been driving the car for a year, and I just can’t seem to wrap my head around the fact that such a small motion in my right ankle generates such a huge smile on my face!”

– Mark Juncosa, VP of Vehicle Engineering at SpaceX: 

We have a dedicated thread for owners of the engine upgrades to discuss their experience.

“When we first hit the canyons in Matt’s Deman 4.5L 718 Spyder, we knew it would be quick, but it was also a cold, damp winter morning and the engine had not been fully broken in. Now, a few months and a few thousand miles later, the monstrous four-and-a-half is broken in properly, with two oil changes and Blackstone Lab reports showing good health, and we can let it rip. Matt and Zack hit the mountain on a crisp, dry morning to see what the ultimate analog sports car can really do.”

Why Matt’s New 565HP, Naturally-Aspirated 4.5L DeMan 718 Spyder is the Perfect Sports Car

As soon as I tried DeMan’s demonstrator vehicle, I was hooked, and decided that it was the best sports car of all time, and I had to have one. Nearly 20 months later, I finally do. Zack and I take our first post-break in drive up a cold, damp canyon together and make the engine sing.

Matt Farah gets to properly drive our 4.5L GT4 and experience the full package. He reviews the details with Rick in the shop, and then shares his feedback.

Matt focuses on the Porsche Cayman Complex a.k.a. how the rear-engine 911 must always be better than the mid-engine 718 — at least from the factory. But when you have Porsche tuners like DeMan Motorsport develop a 4.5L crate engine to give the Cayman the power it truly deserves, well… find out why Matt calls it “bananas” on this episode of MODIFIED.


Road and Track’s

“Meet the Shop Building the 560-HP 4.5-Liter Cayman GT4 Porsche Won’t”

DeMan Motorsport will turn your GT4 into a world-beating supercar for less than you think.

Read the full article

Read a recent review after a test drive of all 3 demo cars.

Check out more discussion on Rennlist:

Latest 4.5L GT4 Dyno Sheet

DeMan 4.5L S 565HP TCF1.11

Perfectly Matched Gear Ratios

As we started using available gear ratios with the 3.8L GT4 cars they worked fairly well, but not perfectly (speaking from a perfectionist standpoint) RPM drop and spread as the power was increasing with the 3.8L but still a major improvement over the stock setup.

So, DeMan Motorsport has developed an exclusive gear setup where the Main shafts and ratios PERFECTLY match to our large displacement high HP and TQ engines for a gearbox that will rival the PDK for close gear spacing and linear acceleration!

After studying lots of data, video, and soundtracks of these cars running through the gears we have come up with the BEST GT4 gearbox combination ever!

Learn More about Our Gearing
DeMan Motorsport Gear Ratios 4.5L GT4

Reviews of the 4.5L Cayman GT4

“I’m a lurker more than a poster, but I’m also another satisfied 4.5L customer…

I recently took delivery of my 4.5L GT4 with the full set of DeMan gear ratios and upgraded diff. In prep for this decision I drove a buddy’s GT4 and loved the mid engine chassis balance, but didn’t necessarily love the transmission. The power was fine but paled in comparison to the 991.2 GT3 parked in my driveway. I was lucky enough to go for a ride in a 4.5L car at Rick’s shop and after feeling that his approach addressed these shortcomings, I went all in.
Rick had been very generous with his time, both with a detailed tour and with explaining how he arrived at the package that exists today. The 4.5L car we were in actually didn’t have the shortened gears and while tach ascent was rapid, it felt like we spent a little too much time in 2nd gear, whereas an earlier throw into 3rd would have been nice (but not really necessary). He also continues to test the package to find limits (e.g. cam-gear bolts) and there haven’t been any material updates since the current 4.5L offering. I guess that’s reassuring. I know from speaking with him that there have been options available to address idiosyncratic customer needs, but imho it probably does more sense to keep the menu simple b/c too much customization can get complicated down the road.
I opted for the GT3RS exhaust to maximize power. While it is definitely louder than stock, its fine at low loads and bearable at most other loads until you go full throttle- at which point the sound just feeds the experience. The sound just checks all the right boxes. Most importantly, the power is absolutely intoxicating (AA here I come!) and shift points are very intuitive. The later is important as the shorter gears give the flexibility to use the torque frequently, while also allowing for quick wind outs into the nether regions of the tach. With a heavy right foot, you just want to keep throwing into the next gear…the only thing better would be a no lift Drenth. Overall, the car is docile and well behaved while puttering around town (medium clutch weight with smooth engagement, smooth power delivery, rewarding sound feedback), and is eager to be unleashed when you feel its safe to drop the hammer (once the tires are warmed up). The break-in period has been a big tease, but I have a track day coming up and can’t wait to open up the set-up.

Call me old school but my gripe with many new cars is that you have to drive them hard and at instant-jail-time-speeds to feel something visceral. Well, the 4.5L package enables that experience at legal speeds, but not at the expense of higher speed capability.

For those that are on the fence, I hate sounding like an advertisement as Rick doesn’t offer sponsorships, but if any of these 4.5L ownership anecdotes sound interesting then you might consider giving Rick a call. This isn’t his first rodeo and he’s got the data to support the recommendations.

Oh, and in case you’re wondering, the GT3 is long gone.”

“This past Friday my buddy ‘twentyseven’ and I made a quick trip down to DeMan Motorsport to check out the 4.5l builds. I’ve been considering taking the plunge and wanted to make the call on if I was going to do it vs. upgrade to a GT3T. And then if this was the right choice I’d have to decide what spec to build (given there are so many combinations available).

Before we touch on anything else let’s acknowledge the people. Rick, Meaghan, and their doggo were incredibly accommodating throughout our visit. We spent a few hours there and they opened up everything for us. Cars, doors, boxes, you name it. Never did we feel rushed or pitched. Everything was an open book and fun conversation. It gave me instant peace of mind for who I’d potentially be entrusting my beloved GT4 to. After we left, the biggest takeaway was the genuine desire to be a part of their family. A squad of knowledgeable folks with amazing built cars and a love of Porsches (plus all the other things we found out we had in common!)

Now I have to tell you guys – Rick’s facility is also out of control. It’s like a Costco with nothing but Porsche parts. There are stacks of shelves to the ceiling filled with rare parts and a shop floor loaded with race cars, heavily modified streetcars, dyno area, engine room, paint booth, secondary storage area for cars etc. The place is legit. Rick keeps things pretty low key on the forums and social media, so this was a real eye opener. It’s not a fly-by-night operation. It’s a heck of a secret, but someone eventually had to post up about it ☺

OK, the cars. Well they absolutely rip it up. It is not often when you think about a modification at this level where you get to sample several versions back to back after a deep dive into the parts that make them up. Rick has it all and has it down to a very serious science. Chart after chart after chart of the gearing options and effects of other options on the dyno plots. His knowledge of the builds and the potential options and outcomes is staggering. Based on what you’re using the car for, driving style, location, etc he can recommend the optimal 4.5l setup for your car. A lot of homework has been done to get this RIGHT.

Over the visit we tested out 3 combinations:

  1. Yellow striped car – 4.5l motor kit, 2-5 gears shortened, headers, GT3 exhaust (titanium I believe), and the sound symposer retrofitted.
  2. Red striped car – 4.5l motor kit, stock gears, headers, and GT3 exhaust (steel I think)
  3. Yellow/black – 4.5l motor kit, 2-5 gears shortened, headers and OEM exhaust

What it really boiled down to after driving all three was no longer the debate to build the motor or not, everyone should do the motor, it’s less than half the price of upgrading to a GT3T. Shortening up the gears are what everyone thinks solve the cars’ biggest hamstring, but its all about the motors actual power delivery. Smoothing out the power and torque bands and giving the car a true GT feel from the seat of the pants is a game-changer physically and mentally. The dyno charts overlaying a stock GT4 against a 4.5l prove it out.

Ironically gearing is up for debate. Depending on the use of the car I could see someone opting to leave things stock, just do 3-5, do 3-6, throw shortening 2 in the mix, or some combination. All of them felt fun in their own way because the motor shined the brightest.

While we were in the area we were also able to meet up and chat with ‘ajw45’. He hooked us up by getting us into the Classic Car Club of Manhattan where we shared some drinks and Porsche talk. He’s got one of the earlier 4.0l builds and is considering the 4.5l upgrade. It’s always fun to finally meet a forum friend in person and feel the passion for the same nonsensical addictions.

And of course great to see ‘og_amer’ as well, in our 3rd city together since randomly meeting on our GT4 European delivery 3 years ago.

So where did this all end up? After a few days thinking it over and a quick call to Rick, transport showed up on NYE to take my car down to the shop and start the build. Rick and I will keep things updated over the next few weeks as the build unfolds.

My current spec for the build is as follows:

  • 4.5l motor
  • 2-5 gears shortened up (Guards gearing and mainshaft)
  • Headers (Rick has these custom developed)
  • Clutch/flywheel upgrade
  • Cobb Tuning port
  • Leaving the OEM muffler

New decade, new motor, new feel to the car. Giddy up!”

“Echoing BealeAss here! I had a great time going down to meet Rick and getting the tour. I once worked in a well-known Porsche shop years ago so it was really nice & reassuring to see an operation of this caliber behind the project.

Rick was also very generous in letting me have a go in the yellow-striped car too and I can say it absolutely delivers on all of the hyperbole we’ve all read about.

As a mere student of engine tuning through a friend who is an actual professional tuner/engine builder, I am familiar with what it takes to get a stock DME to play nice with all of the integrated systems and maintain factory drivability. This was really what stuck out for me the most because of how difficult and time-consuming it is. I told Rick that a 10 minute test drive worth of praise really doesn’t do the effort justice because to get it THAT good surely takes a year+ worth of work at the very least. Then when you compound the fact that he has dialed it in for basically every configuration (various intakes, exhausts, etc) you really start to get an appreciation for the attention to detail and expertise that has gone into this program. Over the years i’ve seen so many hack tuners get peak numbers out of cars that create fanfare but they neglect the actual drivability. And nothing can ruin a car like stumbles, hiccups, and compromises that the less discerning just deem acceptable… and let’s not even think about the ones who blow up motors and then feed you bs about why it’s not their fault.

So I spent the majority of the drive in traffic and just sampling the cars’ behavior below the curve and I really couldn’t find any faults. It’s easy to get in a car and get jaded by how fast it is at WOT -and this thing f**king rips- but that’s not how you drive most of the time. Doing a few 30-80 pulls in different gears really highlight the midrange punch this thing has now. And the new ratios are so well judged. For reference I used to have a 981 Spyder and a 991.1 GT3RS so my curiosity was strong with this one. Part of me wondered if the motor would feel a little less eager and just more V8ish because you’re spinning larger internals, but can say with certainty this thing zings like a GT motor should. It has that explosive spool of the 991 motor while still delivering turbo-like torque. And from the outside it sounds like a full blown cup car. I’m not a diehard Mezger purist but i’ve been lucky enough to drive a 997.2 Sharkwerks 4.1 car as well and this just feels like it takes that up a notch (which is really saying something). The stock powerband of the 9A1 in my Spyder and BealeAss’ car just always annoyed me and felt like unnecessary punishment for this type of car and especially at it’s original price point. Outright numbers aren’t my priority but to be honest paying $100k always bugged me for such a crappy delivery of only 385hp. The engine in my E46 M3 was more fun despite being slower. And the higher price vs. marginal HP increase of the 982 doesn’t make the argument any better either. I absolutely love PDK but there were days in the RS I simply missed driving a manual.. rear engined or not. So while this ‘fix’ isn’t cheap, it turns a fun car into a serious car and I really can’t imagine wanting a GT3 more than one of these. Porsche moved the ball down the field by finally giving us a 911 motor in a Cayman but DeMan carries the ball to the end zone for the touchdown. It’s a group of passionate purists that you just can’t help but want to be a part of. Meeting ajw45 for drinks after and making a new friend immediately was just further proof of this path being bigger than just the displacement of the engine itself.

Maybe the guys that can have bigger garages won’t see the value in doubling down on a 981, but if you are limited by space/funds/wives/crotchgoblins or are just a more advanced driver wanting more from the platform then i’d say this is absolute deal if you look at it from a value proposition. It will stomp on a GT3 and dare I say is overkill?

But then again my dad always told me: “too much power is just enough.”rockon

Review from ajw45 on Rennlist

“The 4.5L is SAVAGE! I got a little time in the development car yesterday and it is one angry GT4! The car is the full package with everything – 4.5L, exhaust, lwfw, short gears, and who knows what else but it is far from stock. The mid-range hit going WOT totally caught me off guard, I cursed, then I held on, then I laughed my *** off after I pulled the next gear and could breathe again. I think if you crossed the old C63 NA AMG v8 with the GT3 engine you’d get something like this – aggressive, motorsporty, and silly fun. It’s not just the power, it’s also the power delivery. The combination of a lwfw, shorter gears, and the torque everywhere 4.5L makes for insane throttle response and a sharp smack of G forces when you get into the gas. Where the 3.8L makes power with an elastic surging kind of feel, this is shockingly immediate and abrupt, you get into the throttle and you don’t get pushed into the seat, you get smacked in the face. Sure the 4.5L car with that set-up and tune the new fastest most powerful GT4 but what really struck me is that car is just oozing character now. The engine is so dominant in the 4.5L that it changes the whole driving experience and turns the GT4 formula on it’s head really. Lots of torque and short gearing has given the GT4 a whole new ridiculous and hilariously hoonable side at street legal speeds like BMW M cars or modern muscle cars. I did 10k miles on my stock 3.8L, have 13k miles now on my 4L X51, test drove a stockish 4.25L, and this ***** out 4.5L development car is a whole new experience. I’ve always been skeptical about mods on performance NA engines but each and every evolution of mods to the 9A1 has really surprised and impressed me. My 4L x51 feels like a totally different engine from the stock 3.8L, stockish feel below 4k rpm but shreds from 5k-8k rpm. The 4.25L car felt like the 3.8L but, well, way bigger with massive mid-range torque like a small V8 for some serious shove. The 4.5L with X51 and GT3 bits feels like a whole different engine again, the torque curve feels flatter than both the 4L X51 and the 4.25L so there is just more power available everywhere and an exciting ramp to redline which comes so so much faster with more power and short gears. No doubt in my mind this is also a way more exciting and aggressive powertrain set-up than a stock 991.2 GT3 manual which is revvy and responsive but a little gutless and you need to ride the revs vs being able to drop the torque hammer of the 4.5L. Without sounding like too much of a fanboy, as exciting as the new 4L in the 718 is, I think the 9A1 in the 981 is still the engine to have. The 718 race cars are still racing the 3.8L, the new intake mods give it more power than the street 4L, and it is approved for racing in the 718 for the next few years with no plans to switch to the 4L. Given the next Boxtser/Cayman gen will be all electric or hybrid, the 4L will likely never get raced and we’ll never see a GT3 engine or any 500hp+ ICE in a Cayman from Porsche. On the other hand, the 3.8L 9A1 has been race tested and not only has there been a lot of effort put in developing and maintaining it by race teams, it still has another few years of continued development by race teams going forward in the 718 GT4. I think for anyone that’s found the GT4 engine a little lacking, this is going to bring more smiles and laughs than an upgrade to a 718 GT4.”

Below are a few pictures of the development process, pistons, intake adapters as well as some shinny engine hardware parts to drool over.

gt4 4.25L 2
gt4 4.25L 488horsepower
gt4 4.25L crank
gt4 4.25L crank2
gt4 4.25L engine block
gt4 4.25L engine package 2
gt4 4.25L parts
gt4 4.25L pistons
gt4 4.25L rods
4.5L Engine in Porsche Cayman at DeMan Motorsport
Porsche Cayman 4.5L Engine at DeMan Motorsport