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Old 10-15-2019, 09:53 PM   #1
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1999 Porsche Boxster Engine Swap Questions.......

Another IMS sob story.....Anyways I was thinking of getting another 2.5L short block and move over the cylinder heads, etc over to that but after some thought figured it would probably be better to get an entire long block and just move over some of the things over. Other option I was thinking of was going with a 2.7L but from what Im hearing its better to just go 3.2L S Engine. 3.4L would be nice but don't want to spend a fortune on this either.

So a few questions...
If I opt to go with the 3.2L could I just get a long block and move over my existing parts like the manifold, throttle body, exhaust manifolds, etc...? I believe I read somewhere someone used the 2.5L intake manifold and used a early 996 throttle body. Would I be able to use the 3.2L throttle body? Also if I do go with the 3.2L do I have to get a new DME? Or Reflash or can I keep my exisiting and just use that as is?

Any thoughts, advice, etc would be great. Also any thoughts if I should just stick with the 2.5L or go with the 2.7L? Trying to keep things down on a budget if possible.

Thanks in advance

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Old 10-16-2019, 07:36 AM   #2
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I just put a used 2.7 in my 99' and it wasn't that bad. I reused the 2.5 intake setup no extra wiring or flash needed.
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Old 10-17-2019, 02:55 AM   #3
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I just put a used 2.7 in my 99' and it wasn't that bad. I reused the 2.5 intake setup no extra wiring or flash needed.
Can you tell if you got a little bump in power? I just did this same swap.
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Old 10-17-2019, 10:37 AM   #4
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If you use the 2.7 you need to use the 2.7 intake manifold (the 2.5l manifold ports are too small for the 2.7 heads, they won’t line up at all). I took the harness off of my 2.5 and transferred it to the 2.7 manifold and used the 2.5 throttle body as well. The 2.7 has a flapper in the intake on the second by pass tube that you’ll need to plug the vacuum supply for. I’ve been told the 2.7 intake manifold is the same manifold the 3.2 uses so in theory you could use this approach to the 3.2 but I doubt the 2.5 tube could handle it. You’d need to get it reflashed. If you go this route feel free to reach to me to I just did it.

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Old 10-17-2019, 02:00 PM   #5
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I couldn't tell you about a difference in power since I bought the car with a blown 2.5.

As for the intake, yes the 2.5 intake does work. You have to remove the metal inserts from the front bolt holes and drill the holes for the second to last bolt. Yes the ports are smaller but the port centerline is the same and the gasket sits perfectly to seal.
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Old 10-17-2019, 07:14 PM   #6
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I just put a used 2.7 in my 99' and it wasn't that bad. I reused the 2.5 intake setup no extra wiring or flash needed.
Thank you for the info. Good to know if I just want to go with a straight forward setup I could just go this route with no tampering with the dme.

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If you use the 2.7 you need to use the 2.7 intake manifold (the 2.5l manifold ports are too small for the 2.7 heads, they won’t line up at all). I took the harness off of my 2.5 and transferred it to the 2.7 manifold and used the 2.5 throttle body as well. The 2.7 has a flapper in the intake on the second by pass tube that you’ll need to plug the vacuum supply for. I’ve been told the 2.7 intake manifold is the same manifold the 3.2 uses so in theory you could use this approach to the 3.2 but I doubt the 2.5 tube could handle it. You’d need to get it reflashed. If you go this route feel free to reach to me to I just did it.

3.2L would be the route I would like to go but around here they are asking way to much for the engine. Plus Ill have to get the DME reflashed which Im sure isn't cheap. Reason why I was thinking of going with the 2.7L which are a bit more cheaper and a bit more easier to source. I was just wondering if I could use my existing DME without a reflash which Chi-Town was able to confirm.

Also if anyone here is from California have you had any issues with smog? Thats another concern I have.
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Old 10-18-2019, 02:16 AM   #7
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I couldn't tell you about a difference in power since I bought the car with a blown 2.5.

As for the intake, yes the 2.5 intake does work. You have to remove the metal inserts from the front bolt holes and drill the holes for the second to last bolt. Yes the ports are smaller but the port centerline is the same and the gasket sits perfectly to seal.
I stand corrected! Did the rubber seal line up or did you have to find another way to seal it? On mine the rubber seal was over lapped by the port on the head
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Old 10-18-2019, 03:47 PM   #8
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The rubber seal sits about a 0.25mm away edge of the port.
No vacuum leaks (about 200 miles so far) but I also have a set of hand made intake manifold gaskets if there's an issue.
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Old 10-20-2019, 09:31 PM   #9
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Anyone in California done this swap?
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Old 10-21-2019, 08:18 AM   #10
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That's where I'm at
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Old 10-23-2019, 12:29 PM   #11
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Just got my dyno results back for my 2.7 running a 2.5 DME and throttle I'll post the graph as soon as I get it. The car has an undersized pulley, no cats and headers, stock tune. It ran a 190rwhp with the 2.5 and just ran a 224rwhp on the same dyno! Its the dyno everyone uses for NASA midatlantic so I trust it, shocked by the numbers though.
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Old 10-24-2019, 07:57 PM   #12
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That's where I'm at
Any issues with smog?

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Originally Posted by truegearhead View Post
Just got my dyno results back for my 2.7 running a 2.5 DME and throttle I'll post the graph as soon as I get it. The car has an undersized pulley, no cats and headers, stock tune. It ran a 190rwhp with the 2.5 and just ran a 224rwhp on the same dyno! Its the dyno everyone uses for NASA midatlantic so I trust it, shocked by the numbers though.
Thats impressive! Good to see that its a good improvement over the 2.5L with stock DME.
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Old 10-25-2019, 03:29 PM   #13
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Visually you can't tell the 2.7 from the 2.5 with the 2.5 intake on it so there was no issue with the visual. Passed the sniffer also.

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