Jump to content

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)
flyingpenguin

Internal differences between M96.20 and M96.21

Recommended Posts

A few months ago I got lucky and picked up two non running Boxster engines for little money. One M96.21 (2.7 L) with a failed IMS and piston / valve collision. The other 2.5 had a dropped sleeve that had resulted in a shattered piston on #1.

In order to be able to "mix-and-match" remaining good parts I am trying to figure out (beyond part numbers from PET) what the real differences are in terms of basic internals between these two engines.

From comparing / measuring, I believe the following parts are identical:

- Case halves

- Heads with valves and valve covers

- Connecting rods and bearings, wrist pins etc.

- IMS to exhaust cam chains

- Chain guides, tensioners etc.

Slightly different (but interchangable) are:

- Crank carrier; the main bearings are mirror images 2.5 vs. 2.7, but offsets and angles are the same. Also the 2.7 has a different design for the chain that runs from crank to IMS shaft; gear vs. double row of teeth.

- IMS shaft, for the same reason as the cranks are different.

So AFAIK, the only real difference is in the pistons.

Kind of important to have this reconfirmed before mixing-and-matching parts...

The forum's input would be very welcome.

Joost

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.


  • Similar Content

    • By Christiaan Poortman
      Hello, I'm new on this forum and stumbled upon a new problem (or old) with my 2.5l 986 Boxster from 1997.
       
      The problem occurs when the engine is started dead cold after sitting a few hours/overnight.
       
      Engine starts immediately but the RPMs start to surge / hunt between 1100 and 700 RPM. This continues for about 10 seconds after which the idle smoothes out to the normal cold idle RPM. 
       
      The first pull away requires a tad more throttle then normal to prevent stalling. After this first pull, everything is almost normal and engine performance becomes better and better. When the engine is hot, the idle sits at 780 RPM with a minor fluctuation now and then (seems to be more than normal)
       
      I've been to two shops (official Porsche dealer and local Porsche specialist). Porsche dealer couldn't find anything and the specialist found the camshaft sensor on the left bank to be unplugged - but now comes the strange thing - the cabling is nowhere to be found!!!!!!? Took the car home to check myself but didn't find anything.
       
      No camshaft related codes to be found in the diagnosis and no CEL either. 
       
      Attached one pic showing the sensor and it's missing plug
       
      Could someone help me out? - Is it possible for the engine not to throw a CEL when sensor is disconnected? - where is the sensor wire to be found?

    • By Harman2907
      Hey guys, I have 2000 Boxster S thats been sitting for months now because it has a rod bearing issue. I found a running 2.5 for cheap becuase its a family friend. I wanted to know what would be needed to do a swap like that? Would it be harder or simple. Im thinking the DME would need to be remapped. Or is it better to sell the car as is? Im trying to empty out the garage so whichever would be faster.
    • By McMadCow
      Hi everyone, I've been reading the RT Forums for a while but now I'm finally registered in order to try and track down an issue I've been having.  I've searched for related issues through the forums already, but nothing is showing up which is a match for mine.  
       
      '99 2.5, 5 Speed, 99K Miles
      Only upgrades are headers and catback.
       
      I've owned the car since March of this year and it's been great so far.  I've even taken it to the local PCA Autocross.
       
      A couple of weeks ago I was cruising on the freeway when my CEL came on steady, no blink.  There was no noise or indication to me that anything had gone wrong, the car kept running completely as usual.  When I got it home I plugged in my code reader and got a cylinder 5 misfire.  I had been planning on a spark plug job anyway, so I got new spark plug tubes the next day as well as 6 plugs and did the job.  I reset the CEL for the drive to my garage space, but on the way there I got a real misfire under heavy acceleration that felt and sounded like the engine was really struggling.  It did go away after a few seconds, though.  
      Whomever was the last person/garage to do the plugs on the car was a complete idiot and should never touch a car again.  None of the spark plugs were torqued, and were all finger tight.  The cylinder 5 plug was covered in dirty oil and had BOTH of its electrodes snapped off.  God only knows where they ended up, but it didn't seem to be in the engine, so that's good I guess.  Once I replaced all the the plug tubes and actually torqued down the plugs themselves, the engine seemed to fire up fine, plus I was no longer getting a ticking on idle that I thought might be a valve issue.  I guess things sound a lot better when the spark plugs are tightened.
       
      Since I thought that cleared things up, I drove it home, and on the way found space to put my foot down.  As soon as the pedal reached the floor, the misfiring started again, with the engine again getting super rough and struggling.  Once I got home I was able to recreate the issue in my driveway by just pinning the throttle and letting the misfires happen again.  Just to be sure the computer didn't still have some wonky settings in it, I disconnected the battery for 30 minutes to let everything reset.  
      Since then I've been pretty scared to go WOT, but a few days ago I did and the exact same thing happened again.  That code indicated cylinders 2 and 3.  Last night I did it again and the code showed cylinder 2.  Unfortunately, the miss didn't go away immediately like it usually does, so it followed me home.  Still, it went back to normal as soon as I turned off the engine and restarted.
       
      Long story short:  I'm getting a rough misfire when I go to full throttle, happens pretty much the instant the pedal hits the floor.  Usually goes away within a few seconds.  No other symptoms, idles and run completely as normal at all other times.  No CEL if I don't trigger the misfire with the gas pedal.  
       
      Any ideas?
       
       
      EDIT: Also, it doesn't appear to be a symptom of revs.  The miss starts when the pedal goes to WOT, not when the revs climb past a certain mark.  I've revved it quite high at partial throttle with no issue.  My code reader says the miss last night started at 3800 rpm, but full throttle.
    • By Nivaldo Veliz
      need help, it is a 98 Boxster 2.5 as you see in the picture the red lined tube is the one not in diagram, the blue and green circles i dont know where they go, neither the purple, now the yellow line leads to the back and that too i dont know where it goes, thank-you :)

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.