2.7 swap

[Dllrd23]

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.

[78F350]

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

[Dllrd23]

Originally Posted by 78F350

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.

[Dllrd23]

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

[truegearhead]

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

[truegearhead]

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

[Dllrd23]

Originally Posted by truegearhead

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

Still plodding along with this project. Had a few people ask if the throttle cable will still reach even though the throttle body has been essentially “moved back” from its original location in the 2.5. What was your experience?

[Dllrd23]

Originally Posted by truegearhead

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

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

[truegearhead]

Originally Posted by Dllrd23

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.

[flmont]

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

[truegearhead]

Originally Posted by flmont

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

[Dllrd23]

Originally Posted by flmont

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

I’ll measure mine when I assemble them.

[Dllrd23]

Originally Posted by flmont

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

‘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.

[Dllrd23]

Originally Posted by flmont

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

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.

[Dllrd23]

Originally Posted by truegearhead

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

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

[truegearhead]

Originally Posted by Dllrd23

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.

[Dllrd23]

Originally Posted by truegearhead

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.

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

[ike84]

Originally Posted by truegearhead

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

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?

Sent from my POCOPHONE F1 using Tapatalk

[JFP in PA]

Originally Posted by ike84

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?

Sent from my POCOPHONE F1 using Tapatalk

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

[ike84]

Originally Posted by JFP in PA

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?



Sent from my POCOPHONE F1 using Tapatalk