Cayman 3.8L X-51 Dyno Results

Is there anyone here who has or does anyone know of anyone or where I can find on the Internet actual dyno results on this conversion? I've read lots of talk and seen claims but where is the real proof? I've had my car dynoed and it is not making what it is supposed to. I'm becoming skeptical that these PowerKit engines will make in a Cayman what they do in a 911 . Different intake, exhaust , tune, etc.

I had done this a few years ago with a 987.1 car, 3.8 S engine and X51 intake. All this with the X51 mapping. Be careful the standard S engine (355 hp) has different ports than the x51 version. You will never get the same power as in a 911 due to different exhaust and due to a more restrictive intake air flow. My expernience is that you always need a step more in a 987 than in a 997. So a 3.8 l conversion will not make 355 but 340 hp in a cayman . A 3.8x51 will not make 381 but 360 hp. To get 380-390 hp you need 3.8 x51 and also sharp camshafts (Schrick for example). All the above for the gen 1 cars. For the gen 2 cars (Dfi) there seems to be more power from the beginning and a few are claiming good gains. But the people who claim good gains are those who have an interest in selling also, so it is up to you to judge what these claims are worth...

M97 or 9A1 (DFI)? Vision Motorsports has done both and I am sure will share dyno sheets. Dwain is pretty straight up on what the engines will do (Dwain Dement - [phone removed]). If 9A1, there are complications with the ECU (not sure exactly what), but the Cayman ECU program will run the engine and car, but limits the power. And the 911 ECU will get the power out of the engine, but has issues with the Cayman ABS, etc. Vision recently completed a 9A1 X51 swap into a Spyder - there were complications, but I believe all is now sorted. If M97, then you can use all of the X51 parts, including the intake, but it takes a bit of work (can't really use the exhaust and maintain the first set of Cats). Also remember, that on the X51 the only difference is the head porting and the intake/ exhaust manifolds. And the intake manifold eliminates the resonance flaps and really only works at high RPM. The valves, cams, pistons, etc. are identical between the stock 3.8 and the X51. Here are pictures of the M97 X51 manifold (and custom intake with GT3 TB) in a Cayman race car: Cheers,

" You will never get the same power as in a 911 due to different exhaust and due to a more restrictive intake air flow." Unlike Krokodil's, which appears to have a Cayman airbox, mine is simply an Evolution cone filter at the end of the tube, swinging in the breeze, the stock airbox removed. I don't know if it is too restrictive but it does not have any ram effect whatsoever. "So a 3.8 l conversion will not make 355 but 340 hp in a cayman. A 3.8x51 will not make 381 but 360 hp." Mine made 297 rwhp so its still 10-20 low. But not worth throwing a lot of money at. " If M97, then you can use all of the X51 parts, including the intake, ..." Yes, mine is a crate 997.1 X-51. By "intake" I assume we are talking the manifold on top - not the airbox? Is that a Cayman airbox? I'm not sure about my exhaust or headers, it was only described as Farnbacher Loles "custom exhaust." FWIW one well-known tuner claims 403 in a Cayman w/ his X-51 conversion file.

with your arrangement , e.g. open cone inside the engine vane you will never make a lot of power. Porblem is that the temp there is so high that the air gets heated up above 50 degree celsius and then the ECU will reduce power to protect the engine. You have to shield your incoming air

Yes, I am referring to only the X51 intake manifold. Yes, my car uses the stock Cayman MAF housing and airbox with a EVOMS filter/plenum inside. Notice that the center section of the intake manifold is upside down to facilitate proper routing of the TB and custom aluminum intake tube (rather than a rubber hose that will likely constrict under vacuum (the tube is not pressurized). Also, having your intake suck hot air from the engine bay rather than cooler air from the stock airbox location (ram effect aside) is likely the primary culprit in your low output. My M97 3.8 (non-X51 except or the intake) makes 345-350 to the wheels (the old one made 354 RWHP) with this setup and an open exhaust . Cheers,

Good info, guys, thanks. John Teece at BGB had the same thoughts about the hot intake air. And to add credence to that, my best lap times at Barber have been in Dec. I don't think I can get a stock airbox back in there but I was thinking at the very least to try to fab a partial enclosure of the filter. Would it not help on hot days to run w/ the engine cover off?

You could probably make this work: https://products.vividracing.com/fa...g.com/fabspeed_competition_air_intake_porsche_987_1_cayman_06_08_4386079592.php No, do not run with the engine cover off. It will be far too loud and very unsafe as you are removing the "firewall" between you and all of that fuel and hot oil, and likely fire if the engine fails. Cheers,

Oops. Not to mention all the track grit and grime blowing inside. That Fabspeed intake looks about like what I have now except for the collar. For $700 I'll make my own shroud. I am convinced that the Evo filter inside the stock airbox is the way to go. But once it is out it is out, unless you drop the engine.

Your intake tubing looks awfully tight and possibly pinched in there as well. If that is just standard 4 ply silicone it could be collapsing at full throttle / high rpm as well. You may be choking the car for air up high, on top of the hot air situation. If you have dyno'd it, can you post results with AFR? Datalog runs with software? If the car is pulling timing up top you might see if anything funny is happening.

I have to strongly agree with Krokodil in regard to your "Hot Air" filter arrangement. Also, I haven't seen any mention of how you've addressed the DME flash. I've seen a number of folks drop 3.8s into Cayman and get 5-15 hp more than the 3.4 because they didn't properly address the DME . The Cayman DME has torque limiting routines in it, a passive part of the PSM. Using Air Flow and RPM the DME will calculate the engine's torque output and it will actually close the throttle plate to prevent the engine from making too much torque. This is why the torque curve on the Cayman is so flat and wide. The torque limiters are intended to prevent loss of traction. If you don't change or eliminate them, you could put a Carrera GT engine in there and it won't make much more than 310 hp.

I got in there yesterday to take a closer look at the lay of the land. Coming out of the TB is a strange looking "elbow" that is molded out of hard rubber. I can only guess that its shape is supposed to flow better. Then there is a silicone hose section, hard plastic elbow, silicone hose, hard plastic MAF housing w/ Evolution MS logo, Evolution MS cone filter. FWIW the FL build sheet I got from the original owner lists the following intake parts: "GOE10536 3.5" OD 90 Deg Elbow, INTKVFFLTR Dry Filter, 996TTMAFTUBE MAF TUBE, INTK-997SPIPE Intake pipe, EVOVENTURI EVO Venturi." I suppose that when I have it dynoed again I will take the cover off and watch for any hose collapse. Based on the A/F from previous dyno, it does not look like that is happening. See chart. Thinking about the intake some more, I'm going to try to insulate the filter from hot engine air anyway, but that does not account for the dyno results, 3 pulls when the engine bay was probably not particularly hot and it was 59* in the shop. The ECU was custom tuned by Revo for FL. Scott/ Softronic says it was not done well.

I consider Scott to be the expert on engine conversions. If (when) I put a 3.8 in my Cayman, Scotts phone will be ringing.

Hi Bill, I am sorry that you continue to have a frustrating time with your car. Please again to consider the filter's being in the engine bay AND I have seen some cars pick up 15 horsepower by cleaning the air filter which looks pretty dirty (i'm not saying that this is the reason but it could be adding to the problem). That filter's being in the engine bay and it's sucking hot engine bay air is the first alarm for the ECU to start negating power. In addition to the engine bay heat, there's so much dirt in a Cayman with no engine cover it's nuts. It's like sitting in a blender filled with sand. As for the engine bay heat, the moment your intake air temp reaches 100F, you could start to lose as much as 20 rwhp and then some. A DFI car will lose as much as 40rwhp. The kinked intake boot is not helping. Finally, IF after addressing those above items the car still continues to not make power, you need to look into the tuning and determine the exact firmware of your car's ECU file to be able to determine if you have a 997 file in your ECU OR a 987 file tuned to accept more air. On some cars this can mean as much as 35 lb/ft of torque through the rev range that the 987 ECU WILL NOT GIVE YOU no matter what motor you bolt in there. There are a lot of people around here that like to think that they have a grasp on this stuff but the reality is that no one has spent more time than yours truly dynoing the 997 firmware vs. the 987 firmware and no one can tell you the exact effect of all of that better than we can. You have a few noticeable things working against you that could be solved and then you need to dig into exactly which firmware is in there. We refuse to bolt motors into cars and let the Cayman / Boxster ECU try and optimize it. I won't let my customers spend the kind of money they're spending without guaranteeing that their dollars achieve the power and torque that brought them to our doorstep and it disappoints me to see a lot of these 3.8 cars that had motors dumped in them, expecting them to spit out 997 power. Your car is not actually that far off and even a true cold air intake like the one we designed for Fabspeed would probably free up about 10 rwhp if the car were cold and as much as 20 after the heat soak begins. You could take out that setup and start further down stream by the MAF sensor and do a different intake. I realize that you dyno tested and that the further into the session your numbers didn't fall off but your car was already heat soaked the moment you rolled onto the dyno. I know you don't want to spend anything crazy on it but I truly believe with some moving around of parts and improving what you got that you could pick up some power. That motor was rated at 385 at the crank which means that with an underdrive pulley, a proper flash, decent manifolds without cats and maybe some race gas, your car should make near 360rwhp. Best of luck! John

Hi, John, thanks for weighing in. The frustration is due to all the power claims that are made about this conversion but no one seems to have dyno proof. So now I, and the guys participating in this discussion, are becoming skeptical that an X-51 in a Cayman w/ reasonable accommodations for it [decent intake, exhaust , and tune] will make 997 power. And I mean the 385, much less the 400+ thrown around. If I do a pull w/ engine cover off, cool ambient temp, fan directed at clean filter, and barely warmed up engine, will that not take the heat issue out of it? Then close it up, warm it up, and see what it does. Then we'll know how much difference a true CAI could make. First thing I bought when I got the car was an underdrive pulley. But the 3.8 is evidently a bit deeper than a 3.4 because there was no room to get at the nut holding the pulley on. It needs to go on before the engine goes in. My intake air routing is not kinked. I think it is OK except that the filter is not insulated from engine bay air. And its not red.

I believe a 24mm socket cut/welded to steel plate would work to bolt up the UD pulley while engine is in the car. The recess disallows a normal 24mm wrench and socket wrench is too much since motor is so close to the cabin (hope that makes sense). The X51 I have put down 320 whp w/ 91 gas and stock headers / exhaust . I've swapped to Cargraphic headers and exhaust and run 94 octane. (I've not dynoed the car myself) Feels fast enough where decided against dealing with a UD pulley. (I don't want to cut the engine block) Edit: For reference a 3.4L 987.1 puts down 270 whp (cai, plenum, ud, exhaust , 100 octane) If anyone in bay area w/ stock Boxster/Cayman S wants half off a dyno session perhaps we can setup a stock vs. modded 3.4L vs. X51 3.8L all from same dyno. To paper race: Let's say the octane difference yields +10hp (negate ud) for the 3.4L and maybe aftermarket headers / exhaust is +10hp for a 3.8L (They claim 30+ PS but let's scale back). This would be a 260whp vs. 330whp difference from 3.4L to X51 3.8L in a 987.1 , so around 70hp@91 octane? (doesn't seem too bad) I've owned both a 3.4L 987 and 3.6L MK2 911 at the same time. There was a world of difference in "acceleration feel" (from either 911 FW vs. 987 or the transmission gearing) that doesn't translate from the displacement alone. I bet driving a X51 987 driven back-to-back with a 911 3.8L wouldn't feel as "fast". But by same driver, the 987 would cross 1/4 mi. quicker due to weight. 1/4 mi time, I would estimate sub 13 sec right in the range of anther nice cabriolet of similar model year, Lamborghini Gallardo Sypder.

Anyways, I guess my post doesn't solve your problem but I would agree your dyno is about 10-20hp low. My TB is located in the stock Cayman location (pretty fancy too) via metal tubing and retains MAF & airbox. I wonder how it shifts the RPM to HP/TQ band vs. Krokodil's setup. Would Porsche had desired to put the TB some alternate distance from the manifold in a 911 ? Answer:

Slightly off topic but if you have an FBL modified 3.8 X51 Gen 1 car then the private label exhaust is actually an M&M exhaust . FVD out of FL now is the lead distributor for M&M. I had the full system on my old 987.1 put on by FBL. I also have a full M&M system on my CR 987.2 put on by SpeedSport (Spencer Cox) who was the guy who did all of the actual work for Greg at FBL. Spencer Cox at SpeedSport may also help you to understand what they did with your 3.8 X51 and if further modifications were made after it left their control. SpeedSport Tuning is right around the corner from the old FBL in danbury CT. Good luck.

Wow, good to know. I Googled M&M and came across a post from you back in 2012 re the exhaust . I've been in contact w/ Spencer and he has been of some help but apparently each of their GTRs was somewhat custom. I may run into him at Road Atlanta next mo. and I can pick his brain a bit. Actually, I thought SpeedSport was in the old FL facility. So, for purposes of this discussion, can I assume my M&M exhaust will yield optimum hp/torque exhaust -wise? I.e. if I am down on power, its not because of the exhaust ?

Actually Danbury Audi rented most of the old FBL buidling from Highcroft racing when all of their 2.0 engines were breaking. They wanted the extra space for all of the warranty work they were expecting. If you are familiar with where FBL was located, you head there as before when coming off of the route 7 connector and Speedsport is on the left past FBL after you make the sharp left hand corner near the airport. As for the M&M exhaust , Kip and Spencer tried every exhaust combo on their old 987.1 's and the M&M was by far the largest producer of power. It wasn't even close. So yes if you have the M&M full exhaust from headers onward you have the optimum setup. Sounds like an air issue combined with a software issue. You may want to ship your car to Speedsport for them to fully diagnose and fix the issues. Expensive but may actually be cheaper in the end. Then you can join me once fixed and run Lime Rock.

That exhaust does a pretty good job, much better than the factory. I dyno'd mine (a SpeedART Off Road Version on a stock 3.4L) at +17.9 rwhp. Coincidentally, that dyno test was performed by Farnbacher Loles. You can read more here (Yes, that is my article.)

Those tips (on the SpeedArt) look just like mine, except w/o the FL logo. FWIW I took my intake off and cleaned it and the MAF; here is what it looks like: The only odd thing is the black plastic 90* elbow at the TB. I have no idea where that came from (surely not a FL custom fabrication) but it must have been designed for clearance and flow. Otherwise why that shape. I'm fashioning some rudimentary shrouding out of a 4'x8' piece of rigid styrofoam wall sheathing. It won't be airtight but should keep some heat out and, more importantly, more outside air in.

" have you actually cleaned the MAF element?" "I took my intake off and cleaned it and the MAF..." yes " it can get very dirty very quickly, not being in a box, surrounded by the dust and dirty air swirling around your engine compartment." " I'm fashioning some rudimentary shrouding..." Of course, in a box it would be showered by all of the grass, dust, and road crap. Not being in an airtight box, some of that stuff will blow by. But I hear you. I ran it several times before I ever cleaned the filter and I was astounded at what came out. I put it on a white piece of paper and just tapped all around it. There was a mound of mostly grass and what looked like coal dust - very fine black powder. I cleaned it and ... could not tell any difference in how the car ran. :-/

just curious ... how reliable is something like a 3.8L conversion kit from say BBI or something? Reason I'm asking is that say for an M97 engine , it's much easier to just bore out the existing engine etc as all the electronics will continue to work. On top of that all the engine mounts would continue to work -- the 997.1 engine would hang a little lower i think? Also get to keep the engine serial number the same (for legal reasons in some areas). I'm thinking about 3.8L or at least 3.6L conversion down the road ... just keep tabs of ideas here.

Hello, Ill post a dyno sheet that Speedsport just did on a Mustang dyno in which reads low for WHP a week ago on a DFI. It was a man trans car with an X51 conversion and it ran 379 on it. Typically they should as a conversion run on a Mustang between 365-379 with a PDK or Man trans. I would say I have done far to many of these to count and have had many sent to me to that had been converted already to get up to the proper HP. All conversions in a 987.1 or .2 should generate at a minimum the transplanted engines HP. The above DFI car as an example is running conservatively in the mid 400's and the 987.1 X51 cars run about 410BHP and the S about 385BHP. The car that won Daytona was also a Man trans X51 conversion that I did and was a full race at 480BHP. Best, Scott

Hey Scott - was this a DFI engine or no? That's impressive power...

Yes it is a 2012 Cayman R with a DFI 3.8 x51 powerplant. Thanks Scott. The car is now incredible. The torque just never stops! Can't wait for Lime Rock to open for the season.

" the 987.1 X51 cars run about 410BHP" Scott, I would be thrilled beyond words if I could get 400BHP! I've just been trying to do my homework before doing anything. I've confirmed here that my exhaust is up to the task but I think the simple intake is a bit under par. I've tried to block off some of the engine bay hot air but I guess I'll be giving away a bit of power there. Thus 400 and not 410.

This is the Mustang dyno sheet on the 997 X51 conversion. The dyno shows 371 as the smoothing brings it down as it was 379. Sorry the info didnt scan well and was on a 987.2 DFI.. The Max HP numbers are1)368 2)371 3) 360 FT-lb are 1)294 2)297 3)284 I wanted to post these as they are hard to read.