Go Back   986 Forum - The Community for Porsche Boxster & Cayman Owners > Porsche Boxster & Cayman Forums > Performance and Technical Chat

Post Reply
 
LinkBack Thread Tools Display Modes
Old 01-09-2021, 04:29 AM   #1
Registered User
 
Join Date: Aug 2020
Location: Wheeling, West Virginia
Posts: 82
Garage
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.

Dllrd23 is offline   Reply With Quote
Old 01-09-2021, 07:09 AM   #2
Motorist & Coffee Drinker
 
78F350's Avatar
 
Join Date: Jul 2014
Location: Oklahoma
Posts: 3,652
Garage
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
__________________
I am not an attorney, mechanic, or member of the clergy. Following any advice given in my posts is done at your own peril.
78F350 is offline   Reply With Quote
Old 01-09-2021, 01:27 PM   #3
Registered User
 
Join Date: Aug 2020
Location: Wheeling, West Virginia
Posts: 82
Garage
Quote:
Originally Posted by 78F350 View Post
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 is offline   Reply With Quote
Old 01-10-2021, 06:30 AM   #4
Registered User
 
Join Date: Aug 2020
Location: Wheeling, West Virginia
Posts: 82
Garage
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
Dllrd23 is offline   Reply With Quote
Old 01-12-2021, 03:47 PM   #5
Registered User
 
truegearhead's Avatar
 
Join Date: Jul 2011
Location: Richmond, VA (The Fan)
Posts: 978
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
__________________
1997 Boxster 4.2L Audi V8 Bi-Turbo
2003 911 C2
NASA HPDE Instructor

Last edited by truegearhead; 01-12-2021 at 03:52 PM.
truegearhead is offline   Reply With Quote
Old 01-12-2021, 03:57 PM   #6
Registered User
 
truegearhead's Avatar
 
Join Date: Jul 2011
Location: Richmond, VA (The Fan)
Posts: 978
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

__________________
1997 Boxster 4.2L Audi V8 Bi-Turbo
2003 911 C2
NASA HPDE Instructor
truegearhead is offline   Reply With Quote
Old 01-12-2021, 04:56 PM   #7
Registered User
 
Join Date: Aug 2020
Location: Wheeling, West Virginia
Posts: 82
Garage
Quote:
Originally Posted by truegearhead View Post
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?
Dllrd23 is offline   Reply With Quote
Old 01-13-2021, 03:26 AM   #8
Registered User
 
truegearhead's Avatar
 
Join Date: Jul 2011
Location: Richmond, VA (The Fan)
Posts: 978
Quote:
Originally Posted by Dllrd23 View Post
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.
__________________
1997 Boxster 4.2L Audi V8 Bi-Turbo
2003 911 C2
NASA HPDE Instructor
truegearhead is offline   Reply With Quote
Old 01-14-2021, 05:08 PM   #9
Registered User
 
Join Date: Aug 2017
Location: Tucson,az
Posts: 690
Do you remember how much larger the intake cross over tubes are ?? Thanks Frank
flmont is offline   Reply With Quote
Old 01-15-2021, 09:21 AM   #10
Registered User
 
truegearhead's Avatar
 
Join Date: Jul 2011
Location: Richmond, VA (The Fan)
Posts: 978
Quote:
Originally Posted by flmont View Post
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
__________________
1997 Boxster 4.2L Audi V8 Bi-Turbo
2003 911 C2
NASA HPDE Instructor
truegearhead is offline   Reply With Quote
Old 01-18-2021, 02:56 PM   #11
Registered User
 
Join Date: Aug 2020
Location: Wheeling, West Virginia
Posts: 82
Garage
Quote:
Originally Posted by flmont View Post
Do you remember how much larger the intake cross over tubes are ?? Thanks Frank
I’ll measure mine when I assemble them.
Dllrd23 is offline   Reply With Quote
Old 01-24-2021, 11:07 AM   #12
Registered User
 
Join Date: Aug 2020
Location: Wheeling, West Virginia
Posts: 82
Garage
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?
Dllrd23 is offline   Reply With Quote
Old 01-24-2021, 11:10 AM   #13
Registered User
 
Join Date: Aug 2020
Location: Wheeling, West Virginia
Posts: 82
Garage
Quote:
Originally Posted by truegearhead View Post
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?
Dllrd23 is offline   Reply With Quote
Old 01-24-2021, 11:15 AM   #14
Registered User
 
truegearhead's Avatar
 
Join Date: Jul 2011
Location: Richmond, VA (The Fan)
Posts: 978
Quote:
Originally Posted by Dllrd23 View Post
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.
__________________
1997 Boxster 4.2L Audi V8 Bi-Turbo
2003 911 C2
NASA HPDE Instructor
truegearhead is offline   Reply With Quote
Old 01-25-2021, 09:25 AM   #15
Registered User
 
Join Date: Aug 2020
Location: Wheeling, West Virginia
Posts: 82
Garage
Quote:
Originally Posted by Dllrd23 View Post
I’ll measure mine when I assemble them.
The ‘02 was 87mm
The ‘99 was 97mm
Dllrd23 is offline   Reply With Quote
Old 01-25-2021, 09:29 AM   #16
Registered User
 
Join Date: Aug 2020
Location: Wheeling, West Virginia
Posts: 82
Garage
Quote:
Originally Posted by truegearhead View Post
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.
Dllrd23 is offline   Reply With Quote
Old 01-25-2021, 02:17 PM   #17
Registered User
 
Join Date: Aug 2020
Location: Wheeling, West Virginia
Posts: 82
Garage
Quote:
Originally Posted by flmont View Post
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.

Last edited by Dllrd23; 01-25-2021 at 02:24 PM. Reason: More info
Dllrd23 is offline   Reply With Quote
Old 01-26-2021, 08:11 AM   #18
Registered User
 
Join Date: Jun 2018
Location: Portland, TX
Posts: 55
@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.
Aanic is offline   Reply With Quote
Old 01-26-2021, 01:52 PM   #19
Registered User
 
truegearhead's Avatar
 
Join Date: Jul 2011
Location: Richmond, VA (The Fan)
Posts: 978
Quote:
Originally Posted by Aanic View Post
@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!
__________________
1997 Boxster 4.2L Audi V8 Bi-Turbo
2003 911 C2
NASA HPDE Instructor
truegearhead is offline   Reply With Quote
Old 01-26-2021, 02:30 PM   #20
Registered User
 
Join Date: Aug 2020
Location: Wheeling, West Virginia
Posts: 82
Garage
Quote:
Originally Posted by Aanic View Post
@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.
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.


Last edited by Dllrd23; 01-26-2021 at 02:45 PM.
Dllrd23 is offline   Reply With Quote
Post Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Trackbacks are On
Pingbacks are On
Refbacks are On




All times are GMT -8. The time now is 05:18 AM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0
Copyright 2024 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website -    DMCA Registered Agent Contact Page