DIY 3.8 Engine Swap thread or article?

I'm look for any DIY 3.8 Engine Swaps threads or articles. There's a lot of picture threads with 'shop conversion' types that don't have much detail. Just pictures of engines coming out and engines going in. Has anyone bought a 3.8S engine and actually done the swap in your garage? - Specifically what 3.4 items need to be transferred to the 3.8 engine? fuel injectors?harness, sensors, any specific oil coolant lines etc. - Can you remove the 3.4 AC compressor without disconnecting and install or just use the 3.8 version b/c you will have to refill the refrigerant regardless? - Did a custom engine mounts or spacers have to be made to lower help clear the 3.8 intake? what did that look like - Will the stock airbox/hose still work? Thanks!

sl951, You can look at 101 projects for Boxster ( 101 Projects for Your Porsche Boxster ) to see what is involved in modifying a 911 engine for use in a 986. He discusses lowering the engine too. I know from installing Torque Solution trans axle mounts there is plenty of room for spacers to be installed for lowering, not sure what or if is needed at the front of engine. The AC compressor lines have been ingeniously designed to remain connected when pulling the engine. The compressor is gotten out of the way while still connected to refrigerant lines during engine removal. I believe the stock air box/hose survives. One of the P-9 members, darbyfam, has a 3.8 installed in his Cayman. I'm not sure how it got there however. Rob VN

It interests me as to how they adapt the ECU to tally with the other existing coded modules or is there a re map for the existing ECU ?

I suspect a remap of ecu Softronics sells such swap tunes

My swap was done by Napleton. You can also talk to BGB Motors. Based on my understanding of what needs to be done, it's not really a DIY project. The motor mounts on my car are not available anywhere, there are ECU mods that have to be done that are definitely NOT DIY. You can PM me with any questions you have.

you might find that using your block and getting a displacement bump to 4.0 or 4.2 more time and cost effective. Everything stays the same externally.

My 997 3.8l X51 swap was done by Orbit Racing (back in 2006) together with a TPC turbocharger. The swap uses the original 987 ECU which must be reprogrammed to "communicate" with the 997 engine. After I recently purchased my car I shipped it to TPC and, among other things, had them reprogram the ECU . The ECU programming, regardless of who does it, is proprietary IP so it may or may not be available to a DIYer. Without reprogramming, you'll have a POS.

No one has done this in their garage,hmm, yet there are ECU software vendors that are selling 3.8 swap kits? ...interesting. So all the conversions out there, (well at least on this board), are shop-type -wow. I suppose if you think dropping a motor out isn't DIY then a swap is out of the question. Personally dropping the motor isn't a big deal. Perhaps this thread could be a start of a DIY 3.8S-MY97 type. I appreciate the PM invites, I might take you up on that during my fun P- Cayman journey.

Does someone have any experience about swapping from 987 mk1 to 987 mk2 cayman S motor? I am curious because some mk1 motors blows up and people replace with new mk1 motor and no one with mk2 that is better engeneered

Pulling and installing a motor wouldn't be hard. It's the fabrication of motor mounts and the ECU programming that would stop me. Not sure I would trust and "off the shelf" ECU remap.

I've tried to start this thread in the past but have not gotten much information. The motor mounts and ECU are actually not the hard parts. It's all the other stuff I don't know about that I am afraid of. The motor mounts do need to be lowered to fit the taller motor. This is pretty much the same as what is on the pelican 986 article. I believe you buy 993 motor mounts and modify them with longer bolts and spacers. The ECU can be reprogrammed by Softronic . This shouldn't be any different than a normal Softronic flash. Worst case you take it out and send it to them.

Softronic actually did all the programming for Napleton flashes and racing along with many other companies conversion files etc. One specifically of interest was the car that won the 24hrs of Daytona. You may call and discuss the conversion requirements in the DFI or Pre cars. A usual rule of thumb is swap engines within the model series. This would be 997.1 with other .1 series such as 987 and .2 DFI series with other .2 cars. We have done several .1 to .2 DFI yet mainly for racing as the cost is much higher. Best, Scott Slauson

911 engine to Cayman Swapping Questions - (FAQ most likely) The least complex and most common paths are: 987.1S with 997.1S 987.2S with 997.2S 981S with 991S ---------------------------------------------- Starting with 987.1S (3.4L) with 997.1 (3.8L). I have the following assumptions and questions. When both engines are out sitting side-by-side in your garage: Electronics: 1. Do I swap the 3.4L engine wire harness on to 3.8L engine (3.8 harness not needed)? 2. Do I use the 3.8L ignition coil packs? 3. Fuel Injectors - Do I use the ones on the 3.8L? 4. Throttle body - Do I use the 3.8L version? What if I upgrade to the 82MM size ( GT3 )? Or it doesn't matter? 5. Mass Airflow meter - Do I use the 3.4L or will I need the 997 3.8L? 6. Are there any other sensors or switches like the 3.8 VarioCam, flywheel RPM, oil or temp that I need to swap or be concerned of? Intake / Exhaust stuff: 1. Most people will use the 3.8S or (X51) intake and flip it's orientation for mid-engine arrangement. I'm assuming this make the engine slightly taller and thus the need for modified engine/tranny mounts. I know this is true for the X51 but what about for the regular 3.8S intake? 2. Exhaust /muffler- Stock cayman headers will bolt up fine or aftermarket that fits cayman etc. Oil/Coolant lines: 1. Basically swap all 3.4L Oil and coolant lines onto the 3.8L engine including the water pump (new pump preferred etc). 2. I'm assuming there isn't anything on the 3.8L that needs to be changed or blocked? Flywheel & Clutch: 1. Use a 997 type Flywheel? The RPM sensor looks different but not sure yet. 2. It appears to me that the 997 and Cayman Pressure plate/clutch are the same? Once the mechanical bits are back in, do a software flash tune from a place like the sponsors of this site. Thanks!

Simple question. How is the drivetrain's rotation corrected with the swaps? I wouldn't think 6 reverse speeds would be a benefit......

sl951 - I think the short answer to all of your electronics questions is that you use the 997 parts. Your ECU is reprogrammed the same as a 997 so everything it talks to should be from the 997. enthuz - you need to use a Cayman transmission, not a 997 transmission. It will spin the right way for the engine orientation. That brings up one of my biggest issues. I have a base Cayman and don't know if my 5 speed will bolt up to a 3.8 and/or if it will handle the power.

"I think the short answer to all of your electronics questions is that you use the 997 parts" Well that certainly makes it more ' plug and play' friendly.

In regards to the engine harness. I'm looking at both motors and I'm pretty sure you don't use the 997 harness as it literally has "Round engine bay connectors" which is different than the 987 'rectangle plug directly into the ECU " type.

Stick with your cayman flywheel and clutch, I used the 997 clutch when I did my swap and it didn't work as well. Also note worthy, there are many threads alluding to the fact that the 3.4l motor is being chocked or limited by its intake and exhaust . This may all be true to a limited extent but I can say for certain that while the stock I/h/e mount up to the 3.8l motor they are very restrictive in that setting and in my experience, I noticed large power gains in the 3.8 motor with aftermarket I/h/e. With the cayman components in place the 3.8 was not noticeably stronger than the 3.4..

I have exchanged a few PMs with you but I will post this for everyone here. Electronics: 1. Do I swap the 3.4L engine wire harness on to 3.8L engine (3.8 harness not needed)? Correct, use the 3.4 harness 2. Do I use the 3.8L ignition coil packs? If you want to, basically the same as the 3.4 3. Fuel Injectors - Do I use the ones on the 3.8L? Yes 4. Throttle body - Do I use the 3.8L version? What if I upgrade to the 82MM size (GT3)? Or it doesn't matter? Use the 997 one or better yet GT3 and IPD plenum 5. Mass Airflow meter - Do I use the 3.4L or will I need the 997 3.8L? I used the 3.4, the 997 one is a bolt in sensor 6. Are there any other sensors or switches like the 3.8 VarioCam, flywheel RPM, oil or temp that I need to swap or be concerned of? Not really, the 987 ECU and Engine cluster/wiring harness does not have a provision for oil pressure Intake / Exhaust stuff: 1. Most people will use the 3.8S or (X51) intake and flip it's orientation for mid-engine arrangement. I'm assuming this make the engine slightly taller and thus the need for modified engine/tranny mounts. I know this is true for the X51 but what about for the regular 3.8S intake? I believe that the X51 intake manifold is shorter but I would still lower the motor. 2. Exhaust/muffler- Stock cayman headers will bolt up fine or aftermarket that fits cayman etc. Someone already commented that you should go aftermarket on the headers and muffler. I certainly agree. Use the primary size that a 997.1S would use. Maybe some vendor can custom one for you. I know FVD can!! Oil/Coolant lines: 1. Basically swap all 3.4L Oil and coolant lines onto the 3.8L engine including the water pump (new pump preferred etc). I know the coolant/water pump is different. Buy all new 987 bits and swap them in. I am unsure on the oil pump, though. 2. I'm assuming there isn't anything on the 3.8L that needs to be changed or blocked? NO, except that I would reuse a modified 997 motorsport AOS, which I have for sale if you want. It has like 20 miles on it. Flywheel & Clutch: 1. Use a 997 type Flywheel? The RPM sensor looks different but not sure yet. I used an Aasco flywheel and Sachs clutch. I have a brand new 997 Aasco flywheel for the 997S if you need one. Will be cheaper than you can buy. 2. It appears to me that the 997 and Cayman Pressure plate/clutch are the same? Pretty much. Once the mechanical bits are back in, do a software flash tune from a place like the sponsors of this site. Yes, FVD can help fill in the blanks if you buy parts from them Thanks! Good Luck

All good information.. thanks. A couple of things I noticed too that support some of the statements above. - the 997S and 987S has the same part numbers for injectors, throttle body, ignition modules - pretty much all the electricals. - The water pump is the same for both engines (same part number). - The oil pump is the same with just a different housing design. Even the oil pressure relief valve is the same (same part numbers for springs etc). - The coolant intake side of the engine (opposite side of pump, the lower right side when looking at the pulley side of the engine). The 3.8L engine has a cast aluminum versus plastic on the 987.1 coolant pipe. The -04 boxster 's have the 3.8 version, so you can buy the small bits to rearrange the coolant direction correctly versus the entire 987.1 plastic housing. If you do use the 987.1 plastic version you'll have to switch out the entire oil pump too (seems unnecessary to me). There is a coolant temp sensor on but both return coolant designs but the electrical plugs look slightly different (cut & swap wires?) - 997S has a entirely different AOS design. The AOS is on top and toward the middle of the engine case versus on the head. I don't see how the 987 stock or motorsport version will work unless you drill a hole into the side of the case. The 997S doesn't even have the proper screw holes to support the 987 type on the 'cylinder head.' It looks to be easier to just use the 997S version. However the 987 power-steering return line gets in the way. I believe I'm going to have to bend and reroute. - Using the 987 flywheel (types) and clutch make sense. Using a 997 flywheel would probably cause a small dimensional change against the 987 tranny 'clutch push bearing' - Better airflow (intake) and exhaust makes sense. - Use the 3.4 MAF, eh. Yep I see the 997 is a plugin type - I haven't measured it's tube diameter yet. But I can see how this is entirely dependent on which software tune to use.

sl951, I wanted to resurrect this thread after reading the latest Panorama. First, congratulations on your victory! It sounds like you figured out all the details to make the swap work. Can you update us with what you learned in the process? Any and all details would be appreciated. jmazz

It looks like this thread is centered around the 987.1 , which I know nothing about. I have however, recently completed a 3.8 DFI conversion for a 987.2 that I did myself. If someone has a 987.2 project that they would like assistance on, I would be glad to help.

Thank you! - Yep the race was fun stuff! The 987.1 3.8 swap (and probably 987.2) is pretty straight forward. Here's my random detail advice. - When you place the 3.8S and stock 3.4 motors side-by-side it becomes fairly clear what to swap over. Just about everything from the 3.4 over 3.8 motor which includes the injector rails (hoses), engine harness, and random heat shielding. Everything bolts up as the blocks are identical. Even the intake bases are the same, thus the Cayman injector rails will fit. The actual injectors are the same part numbers etc. - The front Aluminum-coolant-oil-pump-housing does not need to be swapped with the 'plastic Cayman housing' type - There's an early OEM 'boxster' coolant block off plate and OEM lower pipe that will correct the coolant flow direction. You can also use the same Cayman coolant hoses - just 'tin-snip' the 'cayman' metal connection to ensure the length is long enough to hose clamp (or use a factory hose clamp) back onto the 3.8 motor. You'll have the use the 3.8S coolant temp sensor. This sensor is electronically the same as the Cayman version but has a different connector. It's easy to swap (same color wires), so just swap onto the Cayman harness. It works. - Unlike the 3.4 Cayman engine, the Air/oil seperator is in the middle of the 3.8S motor. This intefers with the 'hard-line' power steering hose. Carefully re-bend the hard line around and tuck it slightly under the 3.8 Air/oil seperator. Use the left-over 3.8S plastic Air/oil lines and 'either plastic weld' or J/B weld onto your Cayman Air/Oil lines to get the perfect length - intake attachments. I thought about just using rubber hoses, but this method provides a factory look. - You'll need to slightly lower the engine/transmission when you reinstall back into the chassis (to allow the taller 3.8S intake to clear). You do this with 6 spacers (or washers). I believe I used 5/8" spacers on the front and 1/2" spacers for the transmission mount.. I also had to slightly grind a bit of metal around the intake and engine-cover-chassis to allow for engine movement - all minor stuff here. - You can probably use the stock OEM transmission mounts, but I recommend swapping these to the Porsche OEM 964 RS engine mounts. Dimensionally they are the same and bolt right up. They offer better stiffness without the draw-backs of increase noise or harshness of after-market stuff for street driving. - Use the Cayman clutch and just change out the 'pressure plate' to the Sach sport version. Pedal feel is still like OEM. You don't need a fancy clutch. I would even use the stock flywheel - useless you don't care about the 'light-weight' flywheel noises. Overall, I can't think of an easier P-car engine swap - no custom parts needed. You do not need a custom exhaust, custom engine mounts, or major fabrication work. The engine harness is the same as stock, you just need a software conversion or perhaps a standard 997 3.8s ECU might work (but I've never tried it).

Thanks for all the information. You make it sound simple. Where did you source the engine? I was hoping they would be more common and affordable right now. Unfortunately I guess there aren't all that many out there.

If you can remove your stock engine/transmission yourself, swapping to a 3.8 is basically the same. Finding a good motor, well that's a bigger challenge. I got lucky and found a 20K low millage version from a dismantler place in Sacramento,CA. However I did review eBay, craigslists, popular dismantler places and insurance salvage websites like iaai.com.

BGB motorsports in Florida will do it for you. Best to pay them 100 per hour to get it done right unless this is something you just really want to do yourself

The 964 RS mounts have standard part numbers. Any P-dealer can sell them or aftermarket store. I got mine from Sunset Porsche in Oregon. Here are the part numbers: Porsche 911 RS Engine Mount Set. You may or may not have to get different bolt lengths. I had to because of my transmission spacers.

I thought you also needed a longer bolt for the RS mounts?

Hey, new to the forum. Embarking on a new DIY swap for a 3.8 to a 981 . Would love to get your advise!