2.7 swap
 

I have the opportunity to “steal” a complete powertrain from an 02 Boxster harness and all trans, mounts, computers. Everything but the tip for the trans. I can get it all for less money and time than rebuilding my basket case 99 with 5 speed and I’ll have a spare trans for my other 99. Question is what problems could I run in to? I already know that I have to deal with a vac line problem if I’m to bolt up the 5 speed to the engine that was previously an auto. Looking for any advise available.

It has been done, but it's not a direct swap engine for engine.
Keep everything from the 2.5 in case you decide to use it on the 2.7.

The biggest differences will be in the computer/wiring harness and the intake. The harness from a 2.7L engine does not have the same connector for the computer as the 2.5L and the two can not just be interchanged without doing some modifications.

The throttle on the 2.7L engines is electronic and the 2.5L engines uses a physical throttle cable. The 2.7L engines have a 'resonance flapper' on the intake to improve airflow across the RPM range. In 2002 the fuel system changed and no longer used a vacuum controlled fuel pressure regulator on the fuel rail.

Look at some of these posts. 'Chi-town' and 'truegearhead' have done similar swaps to what you want to do.:
http://986forum.com/forums/performance-technical-chat/76434-1999-porsche-boxster-engine-swap-questions.html
http://986forum.com/forums/performance-technical-chat/75535-2-7-swap-2-5-blown-motor.html

Deal included DME for the 2.7, theft module, key and cylinder. I was just going to use the 2.7 DME. Looks like I’ll need a pedal though. I scanned through the thread you sent thanks. I’ll more closely read it when I have some car time tonight.

Made the deal on the 2.7. Then I realized that engine is a fly by wire (no throttle cable) and a return less fuel system. Good news is the seller threw in the entire fuel system tank and all. Here is what I have from the donor car 2002 Boxster
2.7 l engine with harness
Auto trans
Complete fuel system
DME
Keys
Cylinder
Theft module

The receiving car 1999 Boxster
2.5l engine with harness
5-SPEED transmission

I would like to keep it as a 5-speed so that I would not have to change over cluster, linkages etc but not sure which module would work.

Looking for most economical solution

Thanks for reaching out over IM. As you know I put a 2.7l in my 2.5l car. You need to use the 2.7 intake manifold, and the 2.5l crossover and throttle body and the 2.5l wiring harness. The vacuum port for the second cross over can just be blocked. I used the factory 2.5l ecu. It dyno’ed at more power to the wheels then a 2.7 is supposed to make at the crank and ran great. If you need anymore help let me know, happy to help

Edit: I also used fuel rail and return system from the 2.5

This is what the hybrid manifold setup looks like all said and done. 2.7L runners, 2.5L throttle body cross over and 2.5L mechanical cable throttle body. Oddly the 2.5L throttle body and cross over is much larger than the 2.7L one which may be why this setup made so much more power than a standard 2.7

http://986forum.com/forums/uploads02...1610499329.jpg

Injectors from the 2.5 or 2.7 or are they the same?

I don’t know, I used the 2.5 injectors. With such a small displacement increase the computer will just adjust the injector duty cycle to make it work.

Do you remember how much larger the intake cross over tubes are ?? Thanks Frank

Take a look at the photo below, you can see the rubber hose it’s stretched from the smaller diameter 2.7 to the larger 2.5 cross over. The ID of the 2.5 is the same size as the 2.7 OD

I’ll measure mine when I assemble them.

I was able to put in a few hours this weekend. Removed intake and fuel injectors. In the process of cleaning up the 2.5L harness. Removed exhaust had to drill out 5 of 6 bolts. Quite a PITA. Removed Auto trans (tip). Took 3 hours as nose of converter was stuck and I didn’t want to pry too hard and break anything. Now I am having trouble with the flex plate. Rusted on. As the name implies it wants to flex too much when trying to pop it off. Any tips or tricks to this?

Did you only use the crossover with the throttle body or both crossovers?

I used both, the non-throttle body cross over has a flapper in it that the 2.5l ecu can’t handle so I just blocked the vacuum line that controls it.

The ‘02 was 87mm
The ‘99 was 97mm

I apologize for what I now see was a not so smart question. I did not realize the ‘99 only has the one crossover.

‘99 is 97mm
‘02 is 87mm

Rookie mistake. I replied to myself. I’m going to buy some silicone reducers 3.75 to 3.5 and try them.

@truegearhead - I'm much in the same boat here. Looking to swap out my 2.5. From what I'm gathering you used the 2.7 engine, swapped the fuel rail, the crossover and the throttle body form the 2.5, the 2.5 harness and blocked off the crossover valve?

Everything else pretty much plug and play?

@DLLRD23 - Keep us up to date, I'm watching this one with a lot of interest.

Yep that’s it!

I just bought some silicone reducers for the crossover from Intercooler Pipe Fabrication they were 3.75” to 3.5”. I’ll let you know how they work. Next order of business is figuring out which exhaust to use. The 2.5 would be plug and play but when I went to get it yesterday, I stood it up on end and a bunch of oil ran out meaning the converter (I think only one side as this was a blown head gasket issue) would be full of oil and likely ruined. The exhaust on the 2.7 has the o2s in the wrong location for the harness which isn’t a huge deal but will require some wiring. I just got some mesh loom to update the harness and some cloth electrical tape from amazon today to freshen up the look of the harness. It was fairly inexpensive (200’ of tape 25’ of 1/4” loom and 25’ of 1/2” loom for $40). Researching which IMS bearing to go with right now. That is next after the harness then all should go quick after that.

I mocked up the intake and the silicone boots fit perfectly. They were 3.75 to 3.5 reducers. They were 3” long so I had to trim 3/4” from each side to make them close to the original boot size. I’ll try to get pics up later.

@truegearhead. My 2.5l harness only has 2 oxygen sensor connectors. Do you know if there is a sort of “jumper harness“ that the 2.5’s used. Also the temp(?) sensor is the front oil passage is a different connector. Do you remember if you had to change yours?

Progress Report: Spent a couple of hours yesterday in the garage. I was able to rehab the 2.5 harness as it was oil soaked from the previous vehicle. I wiped down all the exposed wires with brakeclean and replaces the cloth electrical tape with the same purchased on Amazon along with some mesh wire loom for about $30. All looks pretty clean now. I mocked up the upper intake using the throttle body and runner from the 2.5 and the back runner from the 2.7. For the TB runner I used some silicone adapters bought for $9 each and trimmed them down. I removed the vac valve from the rear runner and am looking for something to plug the holes with. Lastly I wired the engine with the 2.5l harness. A couple of problems I ran into were the O2 connectors are different from 99 to 02 and I have the stock 02 manifolds on still. Also there were only 2 O2 connectors on the 2.5 harness I will have to take a closer look at the 99 exhaust (it is in a separate location) this is easily fixed I just have to decide which exhaust to go with. The MAF connector is also different. Not sure if I have the MAF from the 99 or not?? I know that this thread may not be very interesting to many as I am swapping the 2nd least desirable engine for the least desirable engine but my reason for doing so is simple. I have a very clean and good running 99 that I don't want to do anything to this satisfies my itch to tinker with the Boxster plus the cost to this point is very low (probably have 1/3 of the low book invested via some good luck and a little negotiation. Thanks for following.http://986forum.com/forums/uploads02...1612099373.jpg
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Nice work! Keep us posted, 2.5l engines are becoming rare so this is valuable info. You may want to put an S oil cooler on while you have the engine out, nice cheap upgrade

Thanks for the info !!

I find this fascinating - any idea where the power came from? Did you get any afr readings? Maybe it was running lean and that's where the power came from? Maybe the resonance flapper is actually a handicap (the idea, while I understand the intended purpose, just seems absolutely ridiculous) and deleting it provided a smoother intake flow?

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You need to read up on Helmholtz resonance technology before call that device a handicap.....................

I'm not sure I understand what you mean - Helmholtz resonance refers to dynamic resonance inside of a closed container with a single point of entry.

I understand the purpose of the valve - it is porsche's version of a variable length intake that utilizes in the concept of longer length results in smoother flow which increases velocity into the valves for enhancement of midrange torque, and but utilizing shorter intakes at low rpms and high rpm in order to decrease overall resistance of the system.

My use of the term handicap simply is a reflection of my doubt about the system's ability to accomplish this task. There would need to be a standing wave whose frequency rises in correspondence with the motor rpm or else the system could actually work in reverse and be pushing air away from the open valves. This would be exceptionally difficult to accomplish since we're talking frequency in the 100hz range. Anything other than perfect synchrony would hurt performance. Hence...handicap.

You seem to be one of the most experienced people in the forum in regards to the form and function of these machines. What do you think about the increased torque output of running a 2.7l on a 2.5l tune without a resonance flapper?



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Hey Dllrd23, any progress in the last few weeks?

More to come Sunday. Have half of a day planned for RMS/IMS maybe going to film it and discuss some of the items to change over from 2.5 to 2.7. Just got a couple of boxes of parts from Pelican and I am itching to get back in to it. Thanks for the interest.

We did check AFR during the dyno run, if I could find the damn graph the AFR readings are plotted on the same graph as the power curve. I was completely surprised by the addition HP, I was only swapping the 2.7 in because my 2.5 blew up (failed accusump) and I had a cheap line on a 2.7.

Progress report
 

Progress today: Had high hopes of getting a lot done on the 2.7 as my first Pelican shipment has arrived. Water Pump, T-stat, 4 camshaft seals, Pelican "good-as-new" IMS bearing, tensioner o-rings and seals, and new AOS. I fabricated some camshaft holders out of a piece of stock and they worked better than expected. Pulled the tensioners and nothing moved. Went to use my homemade IMS bearing puller and discovered that the threaded shaft on the center blank was smaller that that on the 1999 2.5l boxster that I made the tool for. you can see video of the tool and the results from the 2.5 here: https://youtu.be/3WvianmKEAg Anyway, I'm going to have to make some corrections to the tool tomorrow at work and then hopefully pull and install the bearing tomorrow. I videoed the whole thing and will be posting to You Tube as well as pics/Narrative here. If you want to follow progress, please subscribe to the channel associated to the link above or check back here for updates. I'm really enjoying this project and excited to share with anyone interested. Again, thanks for following and I hope to have some pics up this week.

Here is what I learned so far. The hardest part of this is going to be the o2 sensors. I am thinking that my solution is going to be replacing all 4 with longer pigtails so that I can use the 2.7 exhaust if for no other reason than to not have to remove the manifolds and rick breaking the bolts. I am confident that I can drill and tap without damaging the head as this is a common occurrence in my job but who wants that aggravation? the reason for the longer pigtail is that in the 2.7L engine harness, you will find all 4 of the o2 connectors where in the 2.5 harness there are only connectors for the upstream o2's the downstream o2's connect to wires that locate up through the trunk and run into the white connector to the right of the ECM and from there go to the ECM. I plan on pulling the o2's and running a scope into the hole front and back to get a good idea of the condition of the catalyst material. You can get a very inexpensive camera that attached to your phone for about $25 from Aamzon.

You will have to change over the coolant temp sensor or swap connectors (which seems a lot harder as you would have to have a reliable wiring diagram and I have already found mistakes in the Bentley Manual). Again not too terribly expensive but it all adds up. About $40 on the high side.

I am changing the AOS, Water Pump, Thermostat, IMS bearing, and Rear Main Seal in the first round of parts. Second round will be spark plug tubes and seals, Spark plugs, I will need new intake gaskets, exhaust manifold to pipe gaskets and bolts, and a new Oil cooler. Figure these should run about $750 (round 1 and 2 combined). Not all of this is necessary but I could not choose which one I would want to do with the engine in the car should save a lot of time in the long run.

My particular car will need some interior work and well as removal of one scratch (with dent) in the rear quarter and a new top replaced before I will call it done. Hope to have it up and running in about 6 weeks. Keep watching and check out some of the videos at a You Tube Channel I just started tonight where I will post videos of the build.

Thanks for the update and I've subscribed. I've got to get this car back online and the only local 2.5l i've found has been sitting in junkyard car since 2015.

Porsche Boxster IMS bearing removal with home made tools Pt1

https://youtu.be/EPY5WLSxqOo

https://youtu.be/EPY5WLSxqOo

I’m not the best cameraman editor or speaker and occasionally I say things that are just completely wrong in these videos. I usually correct myself. But I do discuss a little bit more about the things necessary to complete the swap. I should have two more videos coming and then the IMS will be swapped out. One of the videos will go into pretty good detail of everything I had to change over Hopefully that will be out this weekend

Locking the cams down
 

IMS Bearing Removal Using Homemade Tools Pt2

https://youtu.be/aAsx1rOEcGM

Locking down cams.

Part 4

https://youtu.be/gn8JjcUZZKw

Dllrd23,

Where'd you end up with this? Didn't see any more videos or posts on it.

Summer and knee surgery happened but I’m back on it now. Have a few new videos posted and a couple more being edited as well as a pile or parts to put on. Stay tuned.

Part 5

https://youtu.be/I_7Est03XcA